阅读说明：本技术 具有摩擦引导功能的超声换能器单元 (Ultrasonic transducer unit with friction guiding function ) 是由 R·L·M·因特格罗恩 左菲 M·T·约翰逊 D·贝拉 于 2019-12-12 设计创作，主要内容包括：一种超声换能器单元(12),例如探头,被配置有摩擦引导功能。换能器单元(12)包括在组织接触区处的振动生成模块(20),并且具有用于感测换能器单元跨接触区在其处入射的组织表面(42)的滑动方向的模块(22)。组织表面可以是外部皮肤表面或内部组织表面,例如在导管的情况下。控制模块能用于控制振动生成器的振动,以调节组织接触区处的摩擦的水平。这由控制模块使用以实现摩擦引导功能,所述摩擦引导功能用于基于响应于感测到的滑动方向而控制摩擦水平来引导用户跨入射表面滑动所述单元,例如朝向目标定位(44),例如当滑动在目标方向上时提供较低的摩擦,而使其他方向具有相对较高的摩擦阻力。(An ultrasound transducer unit (12), such as a probe, is configured with a friction guiding function. The transducer unit (12) comprises a vibration generating module (20) at the tissue contact zone and has a module (22) for sensing a sliding direction of a tissue surface (42) at which the transducer unit is incident across the contact zone. The tissue surface may be an external skin surface or an internal tissue surface, for example in the case of a catheter. The control module can be used to control the vibration of the vibration generator to adjust the level of friction at the tissue contact zone. This is used by the control module to implement a friction guiding function for guiding the user to slide the unit across the incident surface, e.g. towards a target location (44), based on controlling the level of friction in response to the sensed direction of sliding, e.g. providing a lower friction when sliding in the target direction, while having a relatively higher frictional resistance in the other directions.)

1. An ultrasound transducer unit (12) comprising:

a tissue contact region (18);

a vibration module (20) at the tissue contact zone;

a movement sensing module (22) for sensing a sliding direction of the transducer unit (12) across an entrance surface; and

a controller (24);

the controller (24) is operable to control sliding friction of the transducer unit (12) across an incident surface (42) based on adjusting a vibration setting of the vibration module; and is

The controller (24) is configured to implement a friction guidance function for guiding an operator along a sliding path (46) across the incident surface, the friction guidance function controlling the sliding friction based on responding to a sensed sliding direction.

2. The ultrasound transducer unit (12) of claim 1, wherein the controller (24) is configured to set a relatively low sliding friction when the sliding direction is along the path and to set a high sliding friction when the sliding direction is off the path.

3. The ultrasound transducer unit (12) of claim 1 or 2,

the sliding path is dynamically determined along the length of the path, or

The sliding path is predetermined.

4. The ultrasound transducer unit (12) according to any one of claims 1-3, wherein the friction guiding function is for guiding an operator towards a target location (44) on the entrance surface.

5. The ultrasound transducer unit (12) of claim 4, wherein the sliding path is a shortest path across the entrance surface to the target location (44).

6. The ultrasound transducer unit (12) of any preceding claim, wherein the ultrasound transducer unit comprises a position sensing module, and wherein the friction guidance is based at least in part on a sensed position of the transducer unit on the surface.

7. The ultrasound transducer unit (12) of claim 4 and claim 6,

defining a current target sliding direction based on the sensed position and a known target location, and the sliding friction is controlled for guiding an operator to slide the probe in said direction, and

optionally wherein the current target slip direction is updated cyclically by the controller (24).

8. The ultrasound transducer unit (12) as claimed in claim 6 or 7, wherein position sensing at a given transducer unit (12) location is based on analyzing ultrasound images acquired at said location.

9. The ultrasound transducer unit (12) of any one of claims 1-8, wherein the controller (24) is configured to apply a machine learning algorithm to determine the current target sliding direction cyclically, the algorithm using real-time acquired ultrasound images as input, and

preferably wherein the algorithm is an algorithm trained using previous ultrasound images acquired at various locations across the surface and associated location information for each image.

10. The ultrasound transducer unit (12) according to any one of claims 1-9, wherein the vibration setting includes at least one of: a vibration amplitude of the vibration module (20) and a vibration frequency of the vibration module (20).

11. The ultrasound transducer unit (12) of any preceding claim,

the vibration module (20) comprises one or more electroactive polymer actuators; and/or

The vibration module (20) comprises one or more ultrasonic transducers.

12. A method of guiding an operator of an ultrasound transducer unit (12) to slide the unit across an incident surface, the method comprising:

sensing a sliding direction of the ultrasonic transducer unit (12), and

controlling sliding friction between the transducer unit (12) and the incident surface in response to the sensed sliding direction, thereby implementing a friction guiding function, wherein the friction control is based on adjusting a vibration setting of a vibration module (20) located at a tissue contact area of the ultrasound transducer unit (12).

13. The method of claim 12, wherein the controller (24) is configured to set a relatively low sliding friction when the sliding direction is in a target direction and to set a higher sliding friction when the sliding direction deviates from the target direction.

14. The method of claim 12 or 13, wherein the friction guiding function is for guiding an operator towards a target location on the incident surface, and optionally wherein,

the friction guiding function is to guide the operator along a shortest sliding path across the incident surface to the target location.

15. A computer program product comprising code means which, when said program is executed on a processor operatively coupled to an ultrasound transducer unit (12), causes the processor to:

receiving a sensor output of a movement sensing module (22) comprised by the ultrasound transducer unit and detecting a sliding direction of the transducer unit based on the sensor output; and is

Controlling a vibration setting of a vibration module (20) located at a tissue contact area of the ultrasound transducer unit (12), thereby controlling a sliding friction between the transducer unit (12) and an incident surface, the sliding friction being controlled in response to a sensed sliding direction, thereby implementing a friction guiding function.

Technical Field

The present invention relates to an ultrasound transducer unit, such as an ultrasound probe.

Background

Ultrasound is an important modality for medical imaging and is the primary examination mode for investigating many pathologies.

For example, one important area is the performance of cardiovascular examinations. Noninvasive imaging of cardiovascular regions using ultrasound is the easiest, straightforward and accurate.

Physical examination of the heart often includes examination of not only the heart of the patient, but also other parts of the body, including the hands, face and neck. Cardiovascular examinations are intended to identify any cardiovascular pathology that may cause a patient's symptoms, such as chest pain, dyspnea, or heart failure.

Key observations that may be performed during physical examination of the heart include: measurement of heart rate; measurement of heart size (e.g., by tapping and sensing the beating of the heart), e.g., as an indication of left ventricular enlargement; and examination of heart valve function and blood flow, for example via auscultation of the heart at four standard positions, which relate to different heart valves, these being the mitral valve, the aortic valve, the tricuspid valve and the pulmonary valve. Heart sounds and murmurs give an indication of valve defects, volume overload, pressure overload and hypertrophy.

One particular form of ultrasound examination is echocardiography.

Echocardiography is an ultrasound test that can be used to assess the structure of the heart and the direction of blood flow within the heart. Technicians trained specifically in echocardiography perform scans using ultrasound probes to produce images and video, often using special probes or transducers placed anywhere on the chest wall to view the heart from different directions. Cardiologists or cardiologists are trained to evaluate acquired images to assess cardiac function and provide reports of results.

The information produced by the echocardiogram may provide an indication of one or more of:

heart size. Weakened or damaged heart valves, hypertension, or other diseases can cause the chambers of the heart to enlarge or the walls of the heart to become abnormally thickened.

Cardiac pumping intensity. Echocardiography can help determine the pumping strength of the heart. Specific measurements may include the percentage of blood expelled from a filled ventricle during each heartbeat (ejection fraction) or the volume of blood pumped by the heart in one minute (cardiac output).

Damage to the myocardium. During echocardiography, it is possible to determine whether all parts of the heart wall normally contribute to the heart pumping activity. The part exhibiting weak movement may have been damaged or receive too little oxygen during the heart attack. This may be indicative of coronary artery disease or various other conditions.

Valve problems. Echocardiography indicates the movement of a heart valve while the heart is beating. It can thus be determined whether the valve is wide enough to open for adequate blood flow (i.e., no stenosis) and/or completely closed to prevent blood leakage (i.e., no valvular regurgitation).

A cardiac defect. Echocardiography can be used to detect many cardiac defects, including problems with the ventricles, abnormal connections between the heart and major blood vessels, and complex cardiac defects that may exist at birth. Echocardiography can also be used to monitor the cardiac development of an infant before birth.

In addition to the above, it is also possible to assess (using more advanced analytical techniques) heart wall thickness, wall dynamics and blood flow patterns.

There are various different hardware implementations for ultrasound examination.

The most common approach takes the form of an ultrasound probe having an array of ultrasound transducers acoustically coupled to a skin contact region at its tip. This is slid over the patient's skin, typically using an acoustic coupling gel applied between the skin and the probe. The ultrasound probe may be a hand-held probe device, for example mounted in the form of a cart or trolley, connected to the ultrasound imaging system or device.

An alternative hardware approach is to use an electronic stethoscope, which assists in performing cardiac auscultation. Recently, advances have been made in the field for more sophisticated processing of auscultated heart sound signals to enable, for example, improved analysis and recognition of the resulting sounds to enable result-based diagnosis. However, as with conventional stethoscopes, electronic stethoscopes rely on clinicians to listen to the auditory sounds from the heart and assess from these sounds whether the heart is healthy or unhealthy. This is a very difficult skill and relies on a high level of training and experience. Which is susceptible to inaccuracies.

Ultrasound, by contrast, is a much more intuitive examination modality, allowing it to be performed by less skilled practitioners, and rendering it less susceptible to human error and therefore unreliable. Studies have shown that even with limited learning periods, students using ultrasound perform better evaluations than experienced doctors using stethoscopes.

An ultrasound probe generates an acoustic signal with an ultrasound transducer. There are different types of ultrasound transducers. The most common type of transducer is a piezoelectric transducer.

An alternative and advantageous type is a Capacitive Micromachined Ultrasonic Transducer (CMUT). CMUT transducers are a relatively recent development. CMUTs exploit the change in capacitance to provide an energy transduction function. CMUTs are built on silicon using micromachining techniques. A cavity is formed in the silicon substrate, over which cavity a thin film is suspended, with a metallization layer thereon serving as an electrode. The silicon substrate serves as a lower electrode.

Since CMUTs are micromechanical devices, it is simpler to construct 2D and 3D arrays of transducers using this technique. This means that a large number of CMUTs may be included in the transducer array, providing a larger bandwidth compared to other transducer technologies.

In addition, due to the smaller size of the CMUT, high frequency operation is also easier to achieve using the CMUT. The frequency of operation depends on the size of the transducer unit (in particular the size of the cavity covered by the membrane) and also on the stiffness of the material used for the membrane.

In addition, since the CMUT transducers are built on silicon, integration of additional control or drive electronics is also easier compared to other transducer technologies. This offers the potential to reduce the form factor of the device, for example, by integrating the control components with the transducer on the same chip.

The decline in physical examination skills among physicians, for example, when performing manual ultrasound examination, has recently been documented. For more experienced clinicians, this may occur due to lack of recent practice or time constraints. In addition, for medical professionals who do demonstrate good technical ability, there are often deficiencies in clinical reasoning when performing examinations, such as following certain observations to determine which anatomical regions to examine or in what order to perform the examination. Sometimes anatomical regions are missed while performing the scan, which is needed for accurate diagnosis later.

Challenges include knowing which anatomical regions to examine, knowing the optimal angle at which to examine the anatomical region, and knowing which locations on the skin to place the probe to properly capture a particular viewing angle. Therefore, correct positioning of the probe on the body to capture the image is a critical issue.

Solutions are known for providing visual guidance to navigate a probe on the body, in particular by providing an additional screen or visual window to provide instructions with text or images. However, it is very difficult and inconvenient for the operator to follow the visual probe manipulation instructions while viewing the real-time ultrasound image data (for clinical evaluation).

For example, haptic feedback methods based on the use of haptic feedback devices in probe handles are also known. These may provide some degree of non-visual guidance to the user. However, communicating directional information with current haptic solutions is very difficult, meaning that some form of supplemental visual guidance is often still required.

An improved module for providing navigational guidance to an operator during an ultrasound examination is therefore sought.

Disclosure of Invention

The invention is defined by the claims.

According to an example consistent with an aspect of the present invention, there is provided an ultrasonic transducer unit including:

a tissue contact region;

a vibration module at the tissue contact zone;

a movement sensing module for sensing a sliding direction of the transducer unit across an incident surface; and

a controller;

the controller is operable to control sliding friction of the transducer unit across an incident surface based on adjusting a vibration setting of the vibration module; and is

The controller is configured to implement a friction guidance function for guiding an operator along a particular sliding path across the incident surface, the friction guidance function controlling the sliding friction based on responding to a sensed sliding direction.

Embodiments of the invention are therefore based on implementing friction guidance for the user: at a given moment, the friction in the preferred direction of movement (as determined by the system) is reduced and the friction in the non-preferred direction is increased (or not reduced).

Friction guidance is a highly effective and direct form of guidance because it not only provides a form of tactile feedback to the user, but also physically guides or causes the probe to follow a determined path. This feedback is more intuitively followed because the user can simply push the probe across the surface along a path with the apparent least resistance. This solution is therefore superior to just vibrotactile feedback, which requires the user to interpret the feedback signal and then judge the correct way of sliding the probe.

The invention is based on the application of the insight surrounding the so-called stick-slip phenomenon, in which a spontaneous jerky movement, i.e. an alternation of stick and slip, can occur between two objects slipping on each other.

It is known that by applying vibrations at the interface between the sliding object and the substrate or surface, the viscosity of the sliding object can be reduced, thereby reducing the effective frictional resistance. The degree of sliding friction can be adjusted by controlling the oscillation amplitude or oscillation frequency of the vibration.

The present invention applies these insights to achieve a navigation or guidance function in which the transducer unit is guided across the surface (e.g., along a given sliding path) by reducing the relative frictional resistance along the desired sliding direction. In other directions, the frictional resistance may increase or remain constant. This may block or impede travel in these directions while allowing or facilitating movement in the target direction.

The method relies on knowing the current sliding direction and wherein, in response, the level of frictional resistance between the tissue contact region and the incident surface is configured. Friction increases (or remains the same) momentarily when the slide is in the wrong direction (e.g., not along a determined or known navigation path or not in the preferred navigation direction) and decreases (or remains the same) when the slide is in the correct target direction.

The use of the stick-slip control insight to achieve ultrasound navigation has not previously been considered.

The transducer unit may for example be an ultrasound probe.

The incident surface for example refers to the incident tissue surface, e.g. the skin surface. The tissue may be skin or internal tissue (e.g., in the case of an invasive probe such as a catheter).

Controlling the sliding friction for example comprises controlling the sliding friction between the tissue contact area of the transducer unit and the entrance surface.

The movement sensing module may also sense a movement speed, i.e., a slip speed. In some examples, the movement sensing module may include one or more accelerometers.

The vibration module is used to generate vibrations, in particular at the tissue contact area. The vibration settings of the vibration module may include at least one or more of: vibration amplitude and vibration frequency. The controller configures the sliding friction level based on a vibration setting configuring the vibration module.

The guidance is based on friction: the friction is increased in a direction not in the target direction, and the friction is decreased in a direction in the target direction.

In an example, the tissue contact region may include an acoustic output region, such as an acoustic window. For example, it may be acoustically coupled to one or more ultrasound transducers to generate imaging signals.

The controller may determine the guided sliding path across the entrance surface completely in advance, or such a path may be determined dynamically or iteratively, for example, where the current target sliding direction is only derived at any given time (e.g., sliding direction is located towards a known target on the entrance surface).

Thus, the path may be predetermined or may occur dynamically, e.g. based on a moment-by-moment real-time calculation of the target sliding direction, e.g. to navigate to a defined target location.

The controller may be configured to set a relatively low sliding friction when the sliding direction is in a direction along the path and to set a high sliding friction when the sliding direction is in a direction deviating from the path.

For example, the sliding friction decreases when the sliding direction is in a direction along the path and/or increases when the sliding direction is in a direction deviating from the path.

Higher and lower mean (relative to each other) relatively higher and lower.

As described above, according to some examples, the sliding path may be dynamically determined along the length of the path.

Alternatively, the sliding path may be predetermined.

The dynamic determination of the path may be based on cyclically re-determining the transient target slip direction. This may be, for example, the direction of the most direct path to target location.

According to an advantageous set of embodiments, a friction guiding function may be used for guiding the operator towards a target location on the entrance surface, e.g. wherein the sliding path is a path towards a defined target location on the surface.

For example, based on the sensed positioning, a target sliding path across the incident surface to the target positioning may be determined, and a frictional sliding function is controlled for guiding the operator along the target sliding path.

The sliding path may be the shortest path across the entrance surface to the target location.

The shortest path may be a spatial shortest path (shortest distance path) or a temporal shortest path (shortest time). However, typically these will be the same.

The controller may determine the shortest path based on a known target location and a known or determined landscape and/or topology (e.g., map) of the incident surface. Known landscapes or topologies may be based on accessing maps, models, or other data sets that store data representing the landscape or topology. For example, an anatomical model or map may be employed.

Alternatively, the path may be an indirect path (e.g., a circuitous path) for traveling, for example, via one or more waypoints, or avoiding one or more obstacles.

In an example, the ultrasound transducer unit may comprise a position sensing module. The frictional guidance may be based at least in part on a sensed position of the probe on the surface. For example, a target sliding path of the transducer unit across the surface may be determined or calculated based on the sensed position of the probe and based on a known target location.

In some examples, the position sensing module may facilitate or provide a movement sensing module, i.e. a movement direction may be detected via sensing a change in the position of the probe. In other examples, a separate means for sensing position may be provided. This may be a sensor, or in some examples may be based on analysis of the acquired ultrasound images, for example to detect anatomical landmarks.

In some examples, the friction guide may determine the target sliding direction based at least in part on a sensed position of the probe relative to the target location, i.e., based on the current position.

According to one or more examples, based on the sensed position and the known target location, a current target sliding direction may be defined, and sliding friction is controlled for guiding an operator to slide the probe in said direction. The target sliding direction may be, for example, the direction of the shortest path to the target location.

The current target slip direction may be updated cyclically by the controller. For example, it may be updated periodically, e.g., at regular intervals. Which may be updated in response to sensed movement or a new sensed position fix.

Where position sensing is included, position sensing at a given transducer unit location may be based on analyzing ultrasound images acquired while at the location. For example, the images may be analyzed to detect anatomical landmarks that may be used to detect the position of the probe.

The detection of the position may be based on a comparison of the current image view with a known perspective of the target location or region of interest. It may be based on a comparison of real-time image data with a data set or database of reference image data corresponding to different known locations across the body.

The images used for position detection may be acquired in real time at each given location and analyzed in real time.

According to one set of embodiments, the controller may be configured to determine the current target slip direction cyclically using a machine learning algorithm. The algorithm may use ultrasound images acquired in real time as input. The algorithm may enable image analysis of the image. The algorithm may be an algorithm trained using previous ultrasound images acquired at various locations across the incident surface and associated location information for the images.

The vibration setting of the vibration module may include at least one of: the vibration amplitude of the vibration module and the vibration frequency of the vibration module.

According to one or more sets of embodiments, the vibration module may comprise one or more electroactive polymer (EAP) actuators, i.e. actuators comprising an EAP.

Electroactive polymers (EAPs) are an emerging class of materials in the field of electroactive materials. EAPs can operate as sensors or actuators and can be easily manufactured in a variety of shapes to allow easy integration into a wide variety of systems.

Advantages of EAP include low power, small form factor, flexibility, noiseless operation, accuracy, possibility of high resolution, fast response time, and cyclic actuation.

The improved properties and particular advantages of EAP materials have led to new applications.

Using EAP to achieve functions that were previously not possible, or provide significant advantages over commonly used sensor/actuator solutions, due to the relatively large deformation and force combined in a small volume or thin form factor compared to conventional actuators. EAP also gives noiseless operation, accurate electronic control, fast response, and a large range of possible actuation frequencies, e.g. 0-1MHz, most commonly below 20 kHz.

The vibration module may additionally or alternatively comprise one or more ultrasonic transducers, for example one or more CMUT transducers.

In further examples, the vibration module may include a vibration actuator, such as a mechanical or electromechanical vibration actuator. This may include, for example, an eccentric rotating mass vibrator.

An example according to another aspect of the invention provides a method of guiding an operator of an ultrasound transducer unit to slide the unit across an incident surface, the method comprising:

sensing a sliding direction of the transducer unit, and

controlling sliding friction between the transducer unit and the incident surface in response to the sensed sliding direction, thereby implementing a friction guiding function, wherein the friction control is based on adjusting a vibration setting of a vibration module located at a tissue contact area of the ultrasound transducer unit.

The direction of sliding may be sensed cyclically, e.g. periodically, e.g. at regular intervals, or in response to e.g. sensing movement (i.e. triggering of a movement sensor).

In an example, the controller may be configured to set a relatively low sliding friction when the sliding direction is in the target direction, and set a high sliding friction when the sliding direction deviates from the target direction.

According to an advantageous set of embodiments, the friction guiding function is configured for guiding the operator towards a target location on the entrance surface. For example, the controller directs the operator along a particular path toward the target location or in a particular direction toward the target location (e.g., the most direct direction or the most direct path).

The friction guiding function may be configured to guide the operator along a shortest sliding path across the entrance surface to the target location.

An example according to another aspect of the invention provides a computer program product comprising code means which, when said program is executed on a processor operatively coupled to an ultrasound transducer unit, causes the processor to:

receiving a sensor output of a movement sensing module included by the ultrasonic transducer unit, and detecting a sliding direction of the transducer unit based on the sensor output; and is

Controlling a vibration setting of a vibration module located at a tissue contact area of the ultrasound transducer unit, thereby controlling a sliding friction between the transducer unit and an incident surface, the sliding friction being controlled in response to a sensed sliding direction, thereby implementing a friction guiding function.

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiment(s) described hereinafter.

Drawings

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

FIG. 1 illustrates a relationship between normalized sliding velocity and normalized sliding friction of an object at different vibration amplitudes;

fig. 2 schematically illustrates an example ultrasound transducer unit in accordance with one or more embodiments;

figure 3 illustrates an example ultrasound transducer unit in use;

FIG. 4 illustrates, in block diagram form, yet another example ultrasound transducer unit in accordance with one or more embodiments;

FIG. 5 illustrates a position detection module based on image registration analysis;

FIG. 6 shows a known electroactive polymer (EAP) device that is not clamped;

fig. 7 shows a known electroactive polymer device constrained by a backing layer; and is

Fig. 8 illustrates the use of EAP actuators for generating vibrations in an example ultrasound transducer unit, in accordance with one or more embodiments.

Detailed Description

The present invention will be described with reference to the accompanying drawings.

It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the devices, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems, and methods of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings. It should be understood that the figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the figures to indicate the same or similar parts.

The present invention provides an ultrasonic transducer unit, e.g., a probe, equipped with a friction guide function. The transducer unit comprises a vibration generating module at the tissue contact area and has a module for sensing a sliding direction across the tissue surface at incidence of the transducer unit contact area. The control module can be used to control the vibration of the vibration generator to adjust the level of friction at the tissue contact zone. This is used by the control module to implement a friction guiding function for guiding the user to slide the unit across the incident surface based on controlling the level of friction in response to the sensed direction of sliding, e.g. providing a lower friction when sliding in the target direction, while having a relatively higher frictional resistance in the other directions.

The present invention thus provides a friction guiding function that guides (i.e. navigates) a user across the incident surface, for example towards a particular target location on the surface, along a particular path across the surface, or in a particular direction or trajectory along the surface.

The friction guidance is based on controlling the friction between the tissue contact surface of the ultrasound transducer unit and said surface, and this is achieved by adjusting the settings of the vibration generating module at the contact surface. The vibrations are adjusted to provide reduced friction when the probe is sensed to move in a mapped target direction or path or trajectory (e.g., for reaching a target location on the surface). When the probe is sensed to move in a direction or path or trajectory different from the determined target, the vibrations may be adjusted to provide a relatively high degree of friction (e.g., by disabling any vibrations) so that the friction with the surface is maintained at its natural (high) state.

The level of friction reduction may be adjusted according to the degree of deviation from the desired direction or path of movement (e.g., according to the angle of deviation). For example, a maximum friction reduction may be provided when the direction of movement is substantially parallel to the target direction or path of movement, and then the level of friction reduction (e.g., vibration amplitude or frequency) provided is reduced in proportion to the angle of departure from that direction or path. The vibration level may be set at zero or a minimum when the direction of movement is exactly opposite to the desired direction or path or trajectory.

Embodiments of the present invention are based on the application of the insight surrounding the stick-slip phenomenon.

The stick-slip phenomenon is a kind of spontaneous jerky motion (jerking motion) that can occur between two objects when slipping against each other, i.e., a case where stick between objects and slip between objects alternately occur.

Generally, there are three possible stick-slip conditions, each producing a different amount of transient frictional resistance. One is stick (maximum frictional resistance), one is slip (smaller frictional resistance), and the other is jump (no contact at all, where the friction is zero).

Depending on the sliding speed and the amplitude and frequency of the oscillations applied at the contact surface, a specific alternating pattern of these three states can occur. At the macroscopic level, this results in an overall effective sliding friction that is dependent on the incidence of different states.

While the bounce state has the lowest frictional resistance associated with it, it lacks controllability and is therefore generally undesirable. The slip state is most desirable and ideal for reducing the frictional resistance, but in order to maintain the slip control, the slip between the two objects should be in the slip state for as high a time ratio as possible.

Stick-slip phenomenon and critical velocity v_{Critical point of}In association, below the critical speed this phenomenon does not occur or occurs at a significantly reduced frequency. Critical velocity v_{Critical point of}Dependent on the amplitude of vibration Δ u at the interface between the objects_zAnd the vibration frequency omega and the friction coefficient mu at the interface₀：

v_{Critical point of}＝μ₀ωΔu_z (1)

Thus, for a constant sliding velocity v, it is possible to increase the critical velocity v_{Critical point of}To reduce the effective frictional resistance, e.g. to keep the critical speed above the level of the sliding speed or to rise higher than it.

As can be seen from equation (1), this can be achieved by increasing the vibration amplitude Δ u at the interface between the objects_zOr one or both of frequencies omega.

Thus, with the present invention, reducing the effective sliding friction between the tissue contact area of the ultrasound transducer unit and the incident tissue surface may be achieved by increasing the vibration amplitude and/or frequency of the vibration module. The level of friction reduction is roughly proportional to the increased vibration amplitude and frequency.

FIG. 1 (left side) shows a graph illustrating the normalized coefficient of friction μ at the surface interface_macro/μ₀(y-axis) normalized sliding velocity for ultrasound transducer unitA graph of the dependency of (c). Normalized slip velocity vs. critical velocity v_{Critical point of}Is normalized so thatCorrespond toThe normalized friction coefficient is relative to the friction coefficient μ between the contact surface of the transducer unit and the tissue surface when there is zero vibration and the sliding speed is at a critical speed₀Is normalized.

Each of the graphical curves or lines corresponding to a different normalized vibration amplitude Delaut_z/Δu_z,0Wherein, Δ u_z,0Corresponding to an absolute baseline surface height u_zAnd (4) horizontal. From top to bottom, the curve corresponds to Δ u_z/Δu_z,0The vibration amplitudes were 0, 0.2, 0.4, 0.6, 0.8, and 1. The upper horizontal line corresponds to Δ u_z/Δu_z,00. Since there is no vibration at this amplitude and thus μ_macro＝μ₀(μ₀Is the coefficient of friction when the vibration is zero) so it is a constant value of 1.

It can be seen that for a given sliding speed, the increased oscillation amplitude reduces the effective frictional resistance (normalized coefficient of friction) between the transducer element and the incident surface.

The graph of fig. 1 (left) is limited only to the slip and stick states. The graph of fig. 1 (right) shows the same set of relationships when the jump-up state is also included. The lines and curves above and including the thick curve correspond to normalized oscillation amplitudes Δ u from top to bottom_z/u_z,00, 0.2, 0.4, 0.6, 0.8, 1.0 and the curve under the bold line corresponds to normalized oscillation amplitude au from top to bottom_z/u_z,0＝1.2、1.4、1.6、1.8、2.0。

As in the left graph of FIG. 1, the upper horizontal line corresponds to Δ u_z/Δu_z,0＝0。

Thus, as mentioned above, reduced friction due to stick-slip phenomena may occur below the critical slip speed:

wherein the content of the first and second substances,and the other symbols have the same names as set forth in the above paragraph.

In practice, applying the above theory to reduce friction places certain constraints on the range of vibration frequencies and amplitudes required given the range of typical sliding speeds of an ultrasound probe during an examination. However, the available frequency and amplitude of vibration using current techniques can be calculated to be sufficient to provide a critical speed well above typical probe sliding speeds.

For example, by applying vibrations using the CMUT cell, at a vibration frequency of 2.5MHz and a CMUT membrane oscillation amplitude of 200nm, and by a friction coefficient μ₀0.4 (no gel applied): v. of_{Critical point of}＝0.2m/s。

For applying vibrations with CMUT cells at the same frequency and amplitude and by applying a gel (coefficient of friction μ)₀＝0.03):v_{Critical point of}＝0.015m/s。

In general, a typical speed at which the ultrasound probe moves or slides during the examination is about 0.05m/s (5cm per second). Thus, the above examples show the available vibration amplitude and frequency such as to allow control of friction within this range of sliding speeds.

Therefore, since the stick-slip phenomenon depends on the slip speed and the oscillation frequency at the surface interface, the sliding friction of the object on the surface is controllable.

Embodiments of the present invention suggest this insight of using a novel directional haptic feedback system that guides an ultrasound probe across a surface (e.g., towards a point of interest on a human body) to enable a user to find the correct probe location without the need to look at the probe itself or independently view provided visual probe manipulation instructions. In particular, the sliding friction may be controlled such that the friction decreases when sliding towards the point of interest and increases when sliding away from the point of interest (or e.g. only indirectly towards it). This induces the dynamic effects that are felt when sliding the ultrasound probe. This is in contrast to currently known vibro-tactile feedback that does not directly convey directional information.

Embodiments of the present invention remove the need to view probe steering instructions by providing direct feedback in the form of frictional resistance that varies in different directions to achieve directional guidance of the operator entirely non-visually. This frees the operator from paying attention to only the acquired ultrasound image information while performing the examination. This solution may be particularly beneficial for less experienced users who benefit not only from navigation guidance, but also from increased attention to medical images.

Fig. 2 schematically illustrates an example ultrasound transducer unit in accordance with one or more embodiments of the invention. The ultrasound transducer unit 12 takes the form of an ultrasound probe having a probe head portion 14 and a handle portion 16. The right hand side of fig. 2 schematically depicts a cross-sectional view through the head portion 14, illustrating at least part of its internal components.

The ultrasound transducer unit 12 includes a tissue contact region 18 located across the upper surface of the head portion 14 in this example. This region provides, in use, a contact interface with the incident surface to which the probe head is applied, so that the probe is slid across that surface via the end of the head.

A vibration module 20 is provided for generating vibrations at the tissue contact region 18. The vibration module 20 may optionally be facilitated by an ultrasound transducer element included in the probe for generating imaging signals. In other examples, the vibration module may be a separate dedicated component, such as a mechanical vibrator (e.g., an eccentric mass vibrator) or an EAP actuator arrangement.

A movement sensing module 22 is also provided for sensing the sliding direction of the transducer unit across the entrance surface. In some examples, the movement sensor may include one or more accelerometers.

A controller 24 is also provided operatively coupled with the vibration module 20 and the movement sensing module 22.

The controller 24 can be used to control the sliding friction of the transducer unit 12 across the incident surface based on adjusting the vibration settings of the vibration module 20.

The controller is configured to implement a friction guidance function for guiding an operator across the incident surface, the friction guidance function controlling sliding friction based on responding to a sensed sliding direction.

For example, the friction guiding function guides the user along a particular sliding path across the incident surface (which may be predetermined or repeatedly calculated along the path), and/or towards a target point/location on the incident surface, or in a certain trajectory across the incident surface, or according to a certain navigation route along the surface.

It should be noted that the relative positioning and location of the components shown in fig. 2 is purely schematic and that the actual location and size may vary. For example, although the controller 24 and motion sensing module 22 are shown in fig. 2 as being located in the head portion 14 of the example probe 12, in other examples, one or both may be located, for example, in the handle portion 16 of the transducer unit 12.

The ultrasound transducer unit 12 contains one or more ultrasound transducer elements, e.g. CMUT transducer elements, for performing ultrasound signal generation and sensing. As described above, in some examples, these transducer elements also contribute to vibrating module 20. Here, noise correction may be applied to correct for noise introduced in the imaging data as a result of the additionally applied baseline oscillation. The vibrations used for friction control are typically at a lower frequency than the ultrasonic oscillations, which means that vibration noise can be distinguished from the imaging signal in the data.

In use, an operator applies the ultrasound transducer unit 12 (in this example a probe) to an incident tissue surface of the body. This may be an external skin surface in the case of an ultrasound probe, or an internal tissue surface, for example, in the case of an invasive ultrasound probe (e.g., a catheter). The user maneuvers the probe over the tissue surface by sliding in the manner typically required for ultrasound examinations. The ultrasound (e.g., acoustic) settings may be adjusted, for example, on an ultrasound control unit and the images generated by the probe monitored in real time on a display of the control unit.

During (and preferably throughout) the examination, the controller 24 of the ultrasound transducer unit 12 implements a friction guidance function. In particular, the controller may determine the target sliding direction for the probe, e.g., cyclically. This may be determined to guide the user to a known target location on the tissue surface, or to guide the user along a target path across the surface. The target location may be a surface location corresponding to a particular target internal anatomical location. For example, for guiding a user to a suitable location on a tissue surface for imaging a region of the heart (e.g., the left ventricle, by way of one example).

Fig. 3 schematically illustrates one example ultrasound transducer unit for use in accordance with one or more embodiments. The transducer unit 12 is shown applied to an example incident tissue area 42, where the tissue contact region 18 at the top of the head 14 of the unit 12 is applied or pressed against a tissue surface to make sealing contact therewith. In an example, an acoustic engagement gel may be applied between the tissue contact region of head 14 and the tissue surface.

The controller 24 of the ultrasound transducer unit 12 determines an instantaneous target sliding direction for the probe along the shortest path 46 towards the target location 44 on the tissue surface 42 of the transducer unit. The controller 24 may predetermine the entire course of the path 46 or may determine only the instantaneous target slip direction for the probe at any given time that represents the most direct path to target location. In some cases, the direction (or path) may be determined by controller 24 to direct transducer unit 12 along an indirect (e.g., circuitous) path toward the location, such as including one or more way-points (way-points) that the probe passes on its way to target location 44 within the sliding travel route of the probe.

Once the instantaneous target sliding direction or path 46 of the transducer unit 12 is determined by the controller 24, the controller implements a friction guidance function for guiding the probe along that direction or path based on friction control and in response to the sensed sliding direction.

A movement sensing module (e.g., an accelerometer in some examples) is used to determine the direction of sliding of the probe 12 and compare it to a target sliding direction or direction of the sliding path. The level of friction between probe tissue contact area 18 and tissue surface 42 is set by the controller at a lower level in response to the sensed direction of sliding along the target direction or path and at a higher level in response to the sensed direction of sliding being different or deviating from the target direction or path. This is schematically illustrated in fig. 3, which shows that for various potential slip directions 48 deviating from the direction of the target path 46 towards the target point 44, the friction (represented by the wavy line) is at a high level, resulting in frictional resistance to the slip. However, in the direction along the path, the sliding friction is reduced by applying vibrations having an appropriate frequency and amplitude using the vibration module 20 (not shown). This results in a sliding path along the target path 46 that provides a lower sliding resistance.

Higher and lower friction levels may be achieved by controlling the vibration settings (e.g., vibration amplitude and/or vibration frequency) of the vibration module 20. These settings are increased to increase the friction reduction and decreased to decrease the friction reduction. Thus, the level of friction experienced may be inversely proportional to the increased vibration amplitude and/or frequency. In some examples, for maximum friction, no vibration is applied, or the vibration is set at a minimum frequency and/or amplitude. For minimum friction, the vibration may be set at a defined maximum amplitude and/or frequency.

The vibration level, and thus the friction reduction level, may be set by the controller 24 according to the degree of alignment between the sensed slip direction (sensed using the movement detection module 22) and the instantaneous target slip direction or direction of the path (a higher vibration level is set for closer alignment, and vice versa).

The degree of friction reduction may be set, for example, according to the scalar product of the unit direction vector corresponding to the slip direction (i.e., normalized to magnitude 1) and the unit direction vector corresponding to the target slip direction (e.g., along the target path).

In some examples, controller 24 may calculate an angle between the sensed current direction of motion and a desired (target) direction (a direction toward point of interest 44). When the angle is close to zero, the controller 24 may adjust the vibration level to provide a minimum sliding friction (high vibration level). When the angle is larger, the controller will make adjustments to provide more friction (e.g., reduce vibration level). When the angle is 180 degrees from the target direction (i.e., opposite the target direction), the controller may make adjustments to provide maximum friction (e.g., by deactivating the vibration, or configuring the vibration setting to a minimum level).

As discussed, in accordance with one or more sets of embodiments, the friction guiding function may be configured to guide the ultrasound transducer unit to a target location 44 on the incident surface 42. The controller 24 may determine a target sliding direction away from the current position of the probe, either cyclically or in response to movement, for example, to achieve the target position. For example, this may correspond to the direction of the most direct or shortest path across the incident surface 42 to the target location 44.

Controller 24 may be configured to determine a path, such as the shortest path, across the surface to the target location. The path may be predetermined or dynamically determined along the length of the path. In this example or otherwise, the controller may determine a direction of a shortest path between the probe and the target location at each time and frictionally guide the probe in that direction. This example still ultimately results in guiding the probe to the target location along some path (if guidance is followed to completion).

Fig. 4 illustrates, in block diagram form, components of one example ultrasound transducer unit 12 configured for enabling frictional guidance towards target location on an incident surface in accordance with one or more embodiments.

As in the example of fig. 2, the unit 12 includes a vibration module 20 ("vibration"), a controller 24 ("control"), and a motion sensing module 22 ("motion sensing"). The unit also includes a target location (or point of interest) locator ("POI locator") 52. The target location detector uses the target location and knowledge of the currently detected motion of the transducer unit 12 relative to the target location to determine the instantaneous target movement direction of the probe. The target location detector may also generate a friction steering signal indicative of the determined target direction. This may be communicated to the controller or vibration module to configure the vibration settings of the vibration module accordingly.

In particular, the signal may indicate, for each movement direction of a set of possible movement directions, an appropriate vibration level for guiding the probe in the target direction. Alternatively, the target location detector may use the detected instantaneous direction of probe movement and determine the appropriate vibration settings for the vibration module 20 based on this and the determined target location. The vibration setting may be determined based on, for example, calculating a relative angle between the direction of motion and the target direction using a vibration level set in proportion to the offset angle (or normalized offset angle)

Although the object-locating detector 52 is described above as a separate component, in other examples its functionality may be integrated in the controller 24, i.e. the controller may carry out its functionality.

The ultrasound transducer unit 12 may further comprise a position detection module for determining a current position or location of the ultrasound transducer unit 12 on the target surface. This may be determined and expressed as a set of coordinates, for example in a locally defined coordinate system of the entrance surface, or may be expressed in any other form.

In some examples, the position detection may be in the form of radio localization, wherein the transducer unit 12 comprises means for generating and transmitting electromagnetic wave localization signals, and an external receiver unit (spaced apart from the transducer unit at a known reference location relative to the patient or the incident surface) is configured to receive the electromagnetic signals transmitted by the localization means of the transducer unit. For example, the location of the unit may be determinable based on the sensed attenuation of the received signal. Multiple receivers (e.g., at least three receivers) may be provided to allow for position triangulation. The transducer unit may instead include a receiver, and one or more transmitters are placed at various reference locations (known to the position detection module of the transducer unit) and configured to transmit a locating signal for detection by the transducer unit receiver.

In some examples, the position detection may be based on image analysis, in particular analysis of ultrasound image data collected in real time at each given location of the probe during use. Based on this, an anatomical analysis of the image data may be applied to detect the current position of the probe. For example, the image data is compared to a data set of reference images or image data identified or tagged with corresponding positioning information of the images or image data. Based on the comparison, the location of the probe can be determined. The positioning may be determined cyclically or, for example, each time movement is sensed.

According to one set of embodiments, a mapping model (e.g., using a machine learning algorithm) may be used to detect location. An example workflow based on this method will now be briefly outlined with reference to fig. 5.

According to this set of examples, the point of interest locator 52 (controller 24) applies a mapping model (e.g., employing a machine learning algorithm, such as a depth learning algorithm) configured (e.g., trained) to identify the current location of the ultrasound transducer unit 12 based on the captured local ultrasound images. Subsequently, a direction towards a given target interest point 44 (e.g. a direction along the most direct path to the interest point) may be determined from the determined geometric vector between the derived current location of the transducer unit 12 and the interest point 44.

A possible workflow for determining such a geometric vector may be as follows.

The first step includes determining whether the image captured at the current location is within the range of known image views of the target region of interest ROI (the anatomical region captured in the image taken at the target navigational location 44). This is schematically illustrated in fig. 5.

For example, an image registration algorithm may be applied to compare the captured image view (at the current location) with known image views associated with the target region of interest (e.g., the region under the target location). If the two do not match, or no overlap is detected (e.g., as illustrated in FIG. 5 (left)), then it is determined that the currently captured view is outside of the view for target localization.

In other examples, a classifier algorithm may be employed, for example, to determine anatomical similarities between a view captured by the ultrasound transducer unit at a current location and a view known to be associated with an image at a target location (ROI).

In the event that at least an overlap between the current view and the target (ROI) view is detected (e.g., as shown in fig. 5 (right)), then only relatively small adjustments to the probe position may be required in order to reach target location.

An image registration algorithm may be applied to determine a degree of registration between a current image view and a target image (ROI) view (e.g., from a model database) to determine a quantitative displacement or deviation (distance + direction) from the target ROI.

In the absence of overlap between the current location view and the target location (ROI) view, controller 24 may, in some examples, search an ultrasound atlas of the currently captured view (a dataset comprising known image views and their associated anatomical locations across the incident surface) and determine the current anatomical location of the transducer unit based on identifying a matching view in the dataset.

By way of alternative, a classifier algorithm may be employed that is trained to predict the current (anatomical) localization from the input current image view. The degree of directional deviation (e.g., angle of deviation from a target localization (ROI) view) can be derived, for example, using model estimation, e.g., calculated using a stored set of view images in an atlas (dataset).

In this case, optionally the distance to the target location (ROI) may not be determined: since a greater distance is to be traveled, only the track direction of travel is immediately relevant. Controller 24 may control the vibration module according to the sensed coupled direction to guide the user in a determined target direction towards target localization (ROI).

In some examples, a mapping model for determining a location from captured image data may utilize a machine learning algorithm, as described above. The machine learning algorithm may be trained using training data comprising ultrasound images or image data representing images captured by the transducer unit at various locations across the incident surface, each image labeled with an associated location of the image. Thus, the algorithm learns (trains) to detect a current location of the transducer unit based on an analysis of the input image data captured at the current location.

A machine learning algorithm is any self-training algorithm that processes input data to produce output data. In the present case, the input data comprises ultrasound images or image data representing images captured by the transducer unit at various locations across the incident surface, each image being marked with an associated location of the image. The output data comprises an indication of the current location of the transducer unit.

Suitable machine learning algorithms for employment in the present invention will be apparent to the skilled person. Examples of suitable machine learning algorithms include decision tree algorithms and artificial neural networks. Other machine learning algorithms such as logistic regression, support vector machines, or naive bayes models are suitable alternatives.

The structure of an artificial neural network (or simply, a neural network) is inspired by the human brain. The neural network is composed of a plurality of layers, each layer containing a plurality of neurons. Each neuron includes a mathematical operation. In particular, each neuron may include a different weighted combination of a single type of transform (e.g., the same type of transform, sigmoid, etc., but with different weights). In processing input data, mathematical operations of each neuron are performed on the input data to produce a numerical output, and the output of each layer in the neural network is sequentially fed into the next layer. The final layer provides the output.

Methods of training machine learning algorithms are well known. In general, such methods include obtaining a training data set including training input data entries and corresponding training output data entries. An initialized machine learning algorithm is applied to each input data entry to generate a predicted output data entry. The error between the predicted output data entry and the corresponding training output data entry is used to modify the machine learning algorithm. This process may be repeated until the error converges and the predicted output data entries are sufficiently similar (e.g., ± 1%) to the training output data entries. This is commonly referred to as a supervised learning technique.

For example, in case the machine learning algorithm is formed by a neural network, (the weighting of) the mathematical operation of each neuron may be modified until the error converges. Known methods of modifying neural networks include gradient descent, back propagation algorithms, and the like.

The training input data entries in the present case may correspond to images or image data. The training output data entries may be anatomical locations corresponding to each image.

By way of non-limiting example, one example machine learning algorithm that may be employed in embodiments of the present invention is outlined in detail in the following article: standard plate Localization in Fetal Ultrasound via Transferred Deep Neural Networks, Chen H, Ni D, Qin J, Li S, Yang X, Wang T, Heng PA, IEEE J Biomed Health info.2015Sep; 19(5):1627-36.

This article describes a deep learning based framework for detecting the standard viewing plane of fetal ultrasound. The same depth learning method can be applied and appropriately adjusted for probe location detection using ultrasound images, as described above.

The ultrasound transducer unit of the present invention comprises a motion sensing module 22. Different options for implementing the motion sensing module 22 of the ultrasound transducer unit 12 are possible.

According to one or more examples, the motion sensing module includes an accelerometer. Accelerometers are otherwise known as G-sensors.

An accelerometer can measure movement of an object, typically in three dimensions (via sensing acceleration forces of the object). More generally, accelerometers are capable of sensing tilt (attitude), acceleration, vibration, and impact forces. For example, in other areas, a mobile device may typically use its accelerometer to determine its current orientation in order to rotate the screen for matching. The wearable fitness device may measure distance, number of steps taken, and pace of movement. Gaming devices often use accelerometer inputs to measure the tilt and/or rotation of a gaming handset in order to control on-screen actions.

According to one or more examples, the motion sensing module may include a magnetic sensor or an electronic compass. Such sensors detect device heading based on the earth's magnetic field. Many consumer devices on the market contain magnetic sensors to enable accurate directional pointing for map orientation and navigation applications.

Magnetic sensors can also provide accurate position determination.

GPS may also provide location information. However, while GPS provides accurate location detection in outdoor environments, it is often not available indoors and is often only occasionally available in dense urban areas, given current technical limitations. In contrast, magnetic sensors support dead reckoning, wherein device position can be tracked based on sensed direction of movement and based on last known position (e.g., a known reference position or starting position), enabling accurate positioning in indoor and GPS challenging areas.

According to one or more examples, the motion sensing module may include one or more gyroscopes. The gyroscope may measure the rate of rotation of the device. This may be used for example to measure the tilt or the pose of the ultrasound transducer unit.

Any other form of movement sensor may additionally or alternatively be used, and the above examples are not limiting. One or more of the options outlined above may also be combined according to one or more examples, such that the ultrasound transducer unit 12 comprises a combination of the example motion sensing modules described above.

As described above, the ultrasound transducer device comprises one or more ultrasound transducer elements for generating and sensing ultrasound acoustic signals for performing imaging. In an advantageous example may comprise an ultrasound transducer array, e.g. with beam steering functionality based on applying appropriate delays to the pulsed excitation of the array of elements. This can be controlled by a beam steering controller. Those skilled in the art will know the means for implementing ultrasound transducer elements and arrays for implementing ultrasound imaging.

According to one or more advantageous sets of embodiments, ultrasound transducer elements for imaging may also be employed for facilitating the vibration module 20. To achieve vibration at a particular level, the controller 24 may be configured to apply a consistent baseline oscillation signal to the entire set of ultrasound transducer elements or a subset of elements at a frequency matching the desired vibration frequency. Any ultrasonic signal is generated by applying an ultrasonic frequency drive signal on top of or superimposed with the baseline vibration signal.

For example, typically, the generated vibrations will have a much lower frequency than the ultrasonic acoustic signals. Thus, the two signals do not significantly interfere with each other even when generated using the same transducer components. Thus, a single set of transducer elements may be driven to simultaneously generate both vibration signals and ultrasound imaging signals, if necessary. The sensing of the reflected ultrasound signal may also be simultaneous with the vibration generation, since again the difference in frequency of the two signals means that the two can be easily distinguished and separated from each other, e.g. using a high pass filter to pass only the (higher frequency) imaging signal.

In some cases, the generated vibrations may have a higher frequency than the generated ultrasound imaging signal. For example, it is generally preferred that the vibrations have a maximum value of [ vibration amplitude ]. times [ frequency ] (in order to achieve maximum friction reduction). If the transducer has the same maximum amplitude available for all frequency levels, it can be preferable to have the vibrations have a higher frequency than the imaging signal.

In either case, the frequencies of the two signals are typically different enough from each other to avoid significant interference between the two.

When the ultrasonic transducer element is driven for generating (friction reducing) vibrations, the imaging capability may be slightly degraded due to vibration noise. During navigation of the probe to the target point of interest 44 on the incidence surface, detailed imaging of the anatomy below the surface is not required (since the desired imaging location has not been reached), and thus the reduced imaging capability does not generally present significant difficulties. However, according to one or more examples, the additional noise may be overcome by controlling the transducer elements in alternating imaging and vibration (oscillator) modes.

The ultrasound transducer elements may take any suitable form. The transducer elements may include piezoelectric transducers (e.g., Piezoelectric Micromachined Ultrasonic Transducers (PMUTs)) and/or capacitive transducers (e.g., Capacitive Micromachined Ultrasonic Transducers (CMUTs)).

According to one set of advantageous embodiments, the ultrasound transducer unit may comprise a posture sensing module for determining the posture (i.e. the angle of inclination) of the probe, e.g. with respect to the entrance surface. In some examples, this functionality may be facilitated by the movement monitoring module, for example where the movement monitoring module includes one or more accelerometers and/or gyroscopes.

The detection of the pose of the ultrasound transducer unit 12 enables further enhancement of the vibration direction guidance with oblique guidance to guide the user to obtain a specific view of the imaged object or region.

Controller 24 may access a data set (stored locally or remotely) that includes an ultrasound transducer unit 12 for association with different anatomical locations and a set of target tilt angles or poses for imaging different anatomical features or bodies. The controller may determine a target pose of the ultrasound transducer unit 12 based on a reference to the data set, based on a current location of the probe on the body and/or one or more user input commands indicative of a desired anatomical object or view (e.g., perspective) to be captured.

The motion sensing module or a separate dedicated tilt sensor may sense the current transducer unit 12 pose and compare it to the identified target pose for the transducer unit. Based on this, the controller 24 may determine the required tilt translation of the transducer unit in order to reach the target pose, based on the current pose. This can be determined as the geometric translation vector required to reach the target tilt position.

This may be performed, for example, using a scalar product calculation between the direction vector corresponding to the current probe pose and the vector corresponding to the target probe pose. This allows, for example, to use the standard formula θ ═ arccos (, (a·b) /(| a | b |)) to determine the angular deviation between two vectors, wherein,aandbtwo directional vectors are represented.

Since the tilt angle or pose is only fully represented by a three-dimensional vector, determining the required angular translation can be performed in two steps, e.g. by representing each pose (current pose and target pose) with a pair of two-dimensional vectors, one in the horizontal plane (representing horizontal rotation) and one in the vertical plane (representing vertical rotation). The necessary rotational translation for reaching the target pose may then be determined in two parts as a horizontal rotation and a vertical rotation based on the use of corresponding scalar products of the horizontal and vertical vectors of the current pose and the target pose.

To guide the operator to the target pose, tactile feedback may be provided to the operator. In some examples, the torque feedback device may be incorporated in the ultrasound transducer unit 12, for example in a handle portion of the unit. The torque feedback device is capable of providing force feedback in opposition to the applied turning force. This may in the present case e.g. be used to apply an opposing force when the transducer unit is tilted in a direction opposite or deviating from the determined translation vector or angle to achieve the target pose. However, when the operator tilts at the correct translation angle or vector, the opposing force may not be applied. This provides direct resistive feedback for incorrect tilt angles, similar to direct frictional resistive feedback generated by the vibration module for guiding the correct sliding direction across a surface.

The invention includes a vibration module. As described above, in certain embodiments, the vibration module may be facilitated by an ultrasound transducer element for ultrasound imaging. The same element may be used both for generating vibrations and for generating ultrasound signals, wherein both may be generated simultaneously by the same element or by alternating between a vibration mode and an ultrasound mode. In the case where the vibration and ultrasound signals are generated simultaneously by the same element, signal processing may be applied to the received reflected signals to filter the portion of the signal associated with the frictional vibration (e.g., a low-pass or high-pass filter). Noise correction may additionally or alternatively be applied to counter noise generated in the reflected signal by the vibrations. In some examples, the vibration control signal may be used as an input to signal processing for use in selecting or filtering a portion of the signal associated with the vibration.

In other examples, a subset of the transducer elements may be used solely for imaging and another solely for generating vibrations. In this example, noise correction may also be applied to the received signal, as the reflected signal may still include noise components due to local vibrations.

In some examples, a separate vibration module 20 (separate from the ultrasound transducer) may be provided. Different options for implementing individual vibration modules 20 are possible.

According to one or more examples, one or more mechanical or electromechanical vibrators may be provided.

In some examples, the vibration module may include one or more linear resonant actuators.

In some examples, the vibration module may include one or more eccentric rotating mass vibration motors.

One or more of these above-described examples may be combined in various examples.

According to one set of embodiments, the vibration module may include one or more responsive material actuators for generating vibrations.

One example is the use of one or more electroactive polymer actuators. Such actuators may comprise one or more layers of electroactive polymer material or a body thereof, with electrodes for electrically stimulating the deformation of the material, thereby providing an actuation effect. These are driven in a periodic drive scheme to generate an oscillating or vibratory actuation output.

Electroactive polymers (EAPs) are an emerging class of materials in the field of electrically sensitive materials. EAPs can work as sensors or actuators and can be easily manufactured in various shapes that allow easy integration into a wide variety of systems.

Materials have been developed with properties, such as actuation stress and strain, that have improved significantly over the past decade. Advantages of EAP include low power, small form factor, flexibility, noiseless operation, accuracy, possibility of high resolution, fast response time and cyclic actuation.

Devices using electroactive polymers can be subdivided into field-driven materials and ion-driven materials.

Examples of field-driven EAPs include piezoelectric polymers, electrostrictive polymers (such as PVDF-based relaxor ferroelectric polymers), and dielectric elastomers. Other examples include electrostrictive graft polymers, electrostrictive paper, electrets, electrostrictive elastomers, and liquid crystal elastomers.

Examples of ion-driven EAPs are conjugated/conducting polymers, Ionic Polymer Metal Composites (IPMC), and Carbon Nanotubes (CNT). Other examples include ionic polymer gels.

The field driven EAPs are actuated by an electric field through direct electromechanical coupling. Which typically requires high fields (tens of megavolts per meter) but low currents. The polymer layer is typically thin to keep the driving voltage as low as possible.

Ionic EAPs are excited by the electrically induced transport of ions and/or solvents. Which typically requires low voltage but high current. Which require a liquid/gel electrolyte medium (although some material systems may also operate using solid electrolytes).

These two classes of EAPs have multiple family members, each with its own advantages and disadvantages.

The first notable subclass of field-driven EAPs are piezoelectric and electrostrictive polymers. While the electromechanical properties of conventional piezoelectric polymers are limited, a breakthrough in improving this property has led to PVDF relaxor ferroelectric polymers, which show spontaneous electric polarization (field-driven alignment). These materials may be pre-strained for improved performance in the direction of strain (pre-straining enables better molecular alignment). Typically, metal electrodes are used because the strain is typically in the medium regime (1-5%). Other types of electrodes (such as conductive polymers, carbon black based oils, gels or elastomers, etc.) may also be used. The electrodes may be continuous or segmented.

Another interesting subclass of field driven EAPs is that of dielectric elastomers. A thin film of this material can be clamped between compliant electrodes to form a parallel plate capacitor. In the case of dielectric elastomers, Maxwell stress caused by the applied electric field results in stress on the film, which causes it to contract in thickness and expand in area. The strain performance is typically augmented by prestraining the elastomer (requiring a frame to maintain prestrain). Strain may be considered (10-300%). This also constrains the type of electrodes that can be used: for low and medium strains, metal electrodes and conductive polymer electrodes may be considered, for high strain regimes, carbon black based oils, gels or elastomers are typically used. The electrodes may be continuous or segmented.

The first significant subset of ionic EAPs is the Ionic Polymer Metal Composites (IPMC). IPMC comprises a solvent expanded ion exchange membrane laminated between two thin metal or carbon-based electrodes and requires the use of an electrolyte. Typical electrode materials are Pt, Gd, CNT, CP, Pd. Typical electrolytes are solutions based on Li + and Na + water. When the field is applied, cations typically travel with the water to the cathode side. This results in reorganization of the hydrophilic clusters and polymer swelling. The strain in the cathode region results in strain in the remaining part of the polymer matrix, resulting in bending towards the anode. Reversing the applied voltage reverses the bend. The known polymer film isAnd

another significant subclass of ionic polymers is the conjugated/conducting polymers. Conjugated polymer actuators typically include an electrolyte sandwiched by two layers of conjugated polymer. The electrolyte is used to change the oxidation state. When an electrical potential is applied to the polymer through the electrolyte, electrons are added to or removed from the polymer, driving oxidation and reduction. Reduction results in shrinkage, oxidation in expansion.

In some cases, thin film electrodes are added when the polymer itself lacks sufficient conductivity (size by size). The electrolyte may be a liquid, gel, or solid material (i.e., a composite of a high molecular weight polymer and a metal salt). The most common conjugated polymers are polypyrrole (PPy), Polyaniline (PANi), and polythiophene (PTh).

The actuator may also be formed of Carbon Nanotubes (CNTs) suspended in an electrolyte. The electrolyte forms a bilayer with the nanotubes, allowing injection of charge. This double layer charge injection is considered to be the main mechanism in CNT actuators. The CNTs act as electrode capacitors with charge injected into the CNTs, which are then balanced by an electrical double layer formed by the movement of the electrolyte to the CNT surface. Changing the charge on the carbon atom results in a change in the length of the C — C bond. As a result, the expansion and contraction of the individual CNTs can be observed.

Fig. 6 and 7 show two possible modes of operation of an EAP device.

The device includes an electroactive polymer layer 64 clamped between electrodes 60, 62 on opposite sides of the electroactive polymer layer 64.

Figure 6 shows the device unclamped. As shown, a voltage is used to cause the electroactive polymer layer to expand in all directions as shown.

Fig. 7 shows a device designed such that the expansion occurs in one direction only. The device is supported by a carrier layer 66. A voltage is used to bend or buckle the electroactive polymer layer.

The electrode, electroactive polymer layer, and carrier may together be considered to constitute the overall electroactive polymer structure.

The nature of this movement arises, for example, from the interaction between the active layer, which expands when actuated, and the passive carrier layer. To obtain an asymmetric curve of the axis as shown, molecular orientation (film stretching) may for example be applied, forcing a movement in one direction.

The expansion in one direction may result from asymmetry in the EAP polymer, or it may result from asymmetry in the properties of the carrier layer, or a combination of both

For the purposes of the present invention, the vibration module 20 may be facilitated by providing an electroactive polymer actuator in vibratory communication with the tissue contact region 18 of the ultrasound transducer unit 12. These may be driven with an alternating (oscillating) drive signal (electrical stimulation) provided at a frequency that matches the desired vibration frequency. The response time of the EAP is sufficient to enable even MHz frequency vibration. For field-driven EAPs, the drive signal may take the form of an (alternating) electric field applied between opposing electrodes sandwiching one or more layers or bodies of EAP material. For ionic EAPs, the drive signal may take the form of an applied (alternating) current. In a simple embodiment, the vibration may be generated by alternately activating EAP (e.g., at voltage V-150 volts) and deactivating EAP (V-0 volts).

EAP actuators are ideal for embodiments of the present invention because of their thin form factor (< 1mm), and their ability to be shaped into any desired footprint. It is also highly flexible, allowing it to be adapted to curved surfaces. Even at very small sizes, they can actuate at frequencies on the order of 1000Hz and above and with amplitudes of about 1 mm. As described in the examples above, these frequencies and amplitudes are sufficient to move between a high friction condition (no actuation) and a low friction condition (with actuation) at typical probe sliding speeds.

It should be noted that for friction reduction, it is the product of the frequency and amplitude of the vibration, which is often important for determining the degree of friction reduction provided by the vibration. Thus, vibrations having a lower frequency and a higher amplitude may provide the same friction reducing effect as vibrations having a higher frequency but a lower amplitude.

One example EAP actuator drive scheme includes driving an EAP actuator with a combined signal composed of a DC signal component and a superimposed high-frequency AC signal component. This results in the generation of surface vibrations that are superimposed on the baseline actuator displacement. The baseline actuator displacement may be configured to lift the tissue contact surface, such as at least partially away from the incident surface, such that a majority of the contact surface is no longer in contact with the incident surface: only the EAP actuator(s) are in contact. This therefore reduces the total contact area with the incident surface ("floating contact"), which greatly reduces friction.

The AC ripple signal above the DC baseline signal additionally provides vibration friction reduction. It may also relax trapped particles or mechanically interlocking surface defects (e.g., local surface roughness peaks or scratches). This further reduces the effective sliding friction between the tissue contacting surface 18 and the incident surface.

The lifting of the contact surface when the DC signal is applied may be, for example, lifting the ultrasound imaging transducer away from the incident surface. This is advantageous when imaging is not used for probe sliding navigation over a surface, as it further reduces contact friction. Where imaging is used to guide navigation across a surface, the EAP actuators can be configured such that DC baseline signal elevation does not lift the imaging actuators away from contact with the incident surface.

Fig. 8 schematically illustrates a cross-sectional view of an example tissue contact region 18 applied to an incident tissue surface 42, the tissue contact region 18 including a set of EAP actuator elements 74 disposed at its surface. These are illustrated in ovals below the two illustrated surface layers. The waveform of an exemplary applied signal is shown in a schematic graph 74, where the y-axis represents voltage and the x-axis represents time. The drive signal applied by the controller 24 includes an AC (ripple) signal superimposed over the DC baseline drive signal. The resulting surface vibration provides anti-stiction properties.

The EAP actuator element 72 is configured such that the drive signal 74 generates both normal orientation 76 and transverse orientation 78 vibrations. Two different subsets of actuation elements may be used to achieve two orientations of actuation. The two subsets may each be clamped in different configurations to cause different directional vibrations. Normal vibration can be achieved by clamping the EAP layer between its side surfaces. The lateral vibration may be achieved by clamping the layer between its upper and lower surfaces.

The EAP actuator elements 72 can each comprise a single layer EAP or a multi-layer EAP stack. In some examples, the EAP actuator may include a bending actuator. In this configuration, the EAP layer is clamped at only one end, leaving the other end free to bend. The free end oscillates up and down (or side-to-side depending on the mounting orientation) in response to an alternating drive signal.

Overall, the higher the amplitude of the AC signal, the lower the sliding friction will be experienced (because the vibrations are greater).

An example according to another aspect of the invention provides a method of guiding an operator of an ultrasound transducer unit to slide the unit across an entrance surface.

The method comprises the following steps:

the sliding direction of the transducer unit is sensed, and

controlling sliding friction between the transducer unit and the incident surface in response to the sensed sliding direction, thereby implementing a friction guiding function, wherein the friction control is based on adjusting a vibration setting of a vibration module located at a tissue contact area of the ultrasound transducer unit.

For example, the friction guiding function may be used to guide the operator along a particular sliding path, or on a particular sliding trajectory, and/or to guide the operator towards a target location on the incident surface.

The controller may be configured to set a relatively low sliding friction when the sliding direction is in the target direction and set a high sliding friction when the sliding direction deviates from the target direction.

As noted, the friction-guided function in some examples may be used to guide an operator toward a target location on the incident surface.

The friction guiding function may be used to guide the operator along the shortest sliding path across the entrance surface to the target location.

The implementation options and details of each of the above steps can be understood and explained in light of the explanations and descriptions provided above for the apparatus aspect of the invention (i.e., the transducer unit 12 aspect).

Any of the example, option or embodiment features or details described above with respect to the apparatus aspect of the invention (with respect to the transducer unit 12) may be applied or combined or otherwise incorporated into the present method aspect of the invention as compared.

An example according to a further aspect of the invention provides a computer program product comprising code means which, when the program is executed on a processor operatively coupled to an ultrasound transducer unit, causes the processor to:

receiving a sensor output of a movement sensing module included by the ultrasonic transducer unit, and detecting a sliding direction of the transducer unit based on the sensor output; and is

Controlling a vibration setting of a vibration module located at a tissue contact area of the ultrasound transducer unit, thereby controlling a sliding friction between the transducer unit and the incident surface, the sliding friction being controlled in response to the sensed sliding direction, thereby performing a friction guiding function.

As described above, certain embodiments utilize electroactive polymers (EAPs). Materials suitable for the EAP section are known. Electroactive polymers include, but are not limited to, the following subcategories: piezoelectric polymers, electromechanical polymers, relaxor ferroelectric polymers, electrostrictive polymers, dielectric elastomers, liquid crystal elastomers, conjugated polymers, ionic polymer metal composites, ionic gels, and polymer gels.

Subcategories of electrostrictive polymers include, but are not limited to:

polyvinylidene fluoride (PVDF), polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene (PVDF-TrFE-CFE), polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene (PVDF-TrFE-CTFE), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyurethane, or mixtures thereof.

Subclasses of dielectric elastomers include, but are not limited to:

acrylate, polyurethane, silicone.

Subcategories of conjugated polymers include, but are not limited to:

polypyrrole, poly-3, 4-ethylenedioxythiophene, poly (polyphenylene sulfide) and polyaniline.

The ionic devices may be based on Ionic Polymer Metal Composites (IPMC) or conjugated polymers. Ionic Polymer Metal Composites (IPMC) are synthetic composite nanomaterials that exhibit artificial muscle behavior under an applied voltage or electric field.

In more detail, IPMC comprises an ionic polymer (e.g., Nafion or Flemion) whose surface is chemically plated or physically coated with a conductor, such as platinum or gold, or a carbon-based electrode. Under an applied voltage, bending deformation is caused by ion migration and redistribution due to the applied voltage across the IPMC strip. The polymer is a solvent expanded ion exchange polymer membrane. The field causes the cations to travel to the cathode side along with the water. This results in reorganization of the hydrophilic clusters and polymer expansion. The strain in the cathode region causes stress in the rest of the polymer matrix, resulting in bending towards the anode. Reversing the applied voltage reverses the bend.

If the plated electrodes are arranged in an asymmetric configuration, the applied voltage can cause all kinds of deformations, such as twisting, rolling, twisting, rotation, and asymmetric bending deformations.

In all of these examples, an additional passive layer may be provided to affect the electrical and/or mechanical behavior of the EAP layer in response to an applied electric field.

The EAP section of each cell may be sandwiched between electrodes. The electrodes may be stretchable such that they follow the deformation of the EAP material. Materials suitable for the electrodes are also known and may for example be selected from the group comprising: thin metal films such as gold, copper, or aluminum; or an organic conductor such as carbon black, carbon nanotubes, graphene, Polyaniline (PANI), poly (3, 4-ethylenedioxythiophene) (PEDOT), for example poly (3, 4-ethylenedioxythiophene) poly (styrenesulfonic acid) (PEDOT: PSS). Metallized polyester films, such as metallized polyethylene terephthalate (PET), for example, with an aluminum coating, may also be used.

As described above, embodiments utilize a controller. The controller may be implemented in a number of ways, using software and/or hardware, to perform the various functions required. A processor is one example of a controller that employs one or more microprocessors that are programmed using software (e.g., microcode) to perform the required functions. However, the controller may be implemented with or without a processor, and may also be implemented as a combination of dedicated hardware and a processor (e.g., one or more programmed microprocessors and associated circuits) that perform some functions to perform other functions.

Examples of controller components that may be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, Application Specific Integrated Circuits (ASICs), and Field Programmable Gate Arrays (FPGAs).

In various embodiments, a processor or controller may be associated with one or more storage media, such as volatile and non-volatile computer memory, such as RAM, PROM, EPROM and EEPROM. The storage medium may be encoded with one or more programs that, when executed on one or more processors and/or controllers, perform the desired functions. Various storage media may be fixed within a processor or controller or may be transportable, such that the program or programs stored thereon can be loaded into a processor or controller.

Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. If a computer program is discussed above, it may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems. If the term "adapted" is used in the claims or the description, it is to be noted that the term "adapted" is intended to be equivalent to the term "configured to". Any reference signs in the claims shall not be construed as limiting the scope.