阅读说明：本技术 有源上升和下降时间的补偿算法 (Compensation algorithm for active rise and fall times ) 是由 J·范布鲁塞尔 于 2020-04-03 设计创作，主要内容包括：提供一种用于补偿脉冲X射线系统的设置的方法。针对要提供的X射线脉冲选择电流、电压和预期脉冲宽度设置。然后,根据存储的在预定温度处的一个或多个标准化值,考虑到X射线罐的电子电路的环境温度,对针对设定电压和管电流的所选择的脉冲宽度设置进行补偿。在校准步骤中根据实际的或有效的脉冲宽度及其与预期宽度的差来获得标准化值,利用提供给所述源的脉冲电压和电流的电路的温度使所述值标准化。(A method for compensating a setting of a pulsed X-ray system is provided. The current, voltage and desired pulse width settings are selected for the X-ray pulse to be provided. The selected pulse width setting for the set voltage and tube current is then compensated for taking into account the ambient temperature of the electronic circuitry of the X-ray canister, according to the stored one or more normalized values at the predetermined temperature. In the calibration step a normalized value is obtained from the actual or effective pulse width and its difference from the expected width, which value is normalized by the temperature of the circuit supplying the pulsed voltage and current of the source.)

1. A method of providing X-ray pulses by an X-ray system comprising an X-ray canister including an X-ray source, the method comprising:

selecting (101) a current, a voltage and a desired pulse width setting for the X-ray pulse to be provided,

compensating (103) the selected pulse width setting for the selected voltage and tube current according to the stored normalized value at the predetermined temperature taking into account the internal temperature of the X-ray canister.

2. The method according to the preceding claim, further comprising calculating (106) a normalized value from the stored normalized values corresponding to the first setting for current and the first setting for voltage and the stored other normalized values corresponding to the other settings for current and the other settings for voltage by interpolation, at least one of the other settings being different from the value of the first setting, wherein the selected current and voltage values are between the first setting and the other settings for current and/or voltage and the other settings.

3. A method of calibrating an X-ray system comprising an X-ray canister, wherein the X-ray canister comprises an X-ray source, the method comprising:

applying (502) settings for the selected current, the selected voltage and the expected pulse width to the X-ray source, thus generating actual voltage and current signals for the X-ray source to produce at least one X-ray pulse, the at least one X-ray pulse thus produced having an actual pulse width,

measuring (503) the actual voltage signal applied to the X-ray source,

determining (504) the actual pulse width based on the measured actual voltage signal,

obtaining (505) a difference between the actual pulse width and the expected pulse width,

obtaining (507) a normalized value from the difference at a predetermined temperature taking into account (506) an internal temperature of the X-ray canister, the internal temperature being an ambient temperature for electronic circuitry of the X-ray canister, and

storing (510) the normalized value from the difference as a function of the settings of the selected current and the selected voltage.

4. The method of claim 3, further comprising measuring an internal temperature of the X-ray canister prior to obtaining a normalized value from the difference, the internal temperature of the X-ray canister being the ambient temperature for the electronic circuitry of the X-ray canister.

5. The method according to claim 3 or 4, further comprising obtaining (509) a rise and fall time deviation of the at least one X-ray pulse from the difference between the determined actual pulse width and the expected pulse width, wherein obtaining a normalized value from the difference at a predetermined temperature further comprises obtaining (508) a normalized value of the rise and fall time deviation at the predetermined temperature by using a predetermined relation between a capacitance change of the X-ray canister and an internal canister temperature, the internal canister temperature being the ambient temperature for the electronic circuit.

6. The method of any of claims 3 to 5, wherein storing the normalized value from the difference between the actual pulse width and the expected pulse width comprises:

storing (510) the normalized values of the rise and fall time deviations as a function of the selected current and the selected voltage.

7. The method according to any of claims 3 to 6, further comprising repeating the method for at least one different set of selected currents and/or voltages, whereby further normalized values from the difference are stored (510) as a function of the different selected currents and selected voltages.

8. The method as recited in claim 7, further comprising calculating (511) at least one normalized value of current and/or voltage from between a selected setting of current and/or voltage and a different selected setting of current and/or voltage by interpolation.

9. A computer program product comprising instructions which, when said program is executed by a computer, cause the computer to control an X-ray system to provide X-ray pulses according to the method of any one of claims 1 or 2.

10. A computer program product comprising instructions which, when said program is executed by a computer, cause the computer to control the calibration of an X-ray system according to the method of any one of claims 3 to 8.

11. A data storage (207) for an X-ray system comprising normalized values obtained by the method according to any one of claims 3 to 8.

12. An X-ray system (200) comprising an X-ray canister (201), the X-ray canister (201) comprising an X-ray source (203), the X-ray system (200) further comprising a control unit (208) controllable by a software product according to any one of claims 9 or 10.

13. The X-ray system of claim 12, further comprising a temperature sensor (209) for sensing the temperature of at least a portion of the X-ray canister.

14. The X-ray system according to any one of claims 12 or 13, further comprising a data storage (207) according to claim 11, wherein the control unit (208) is configured to receive at least one of the normalized values.

Technical Field

The present invention relates to the field of radiation diagnosis. More particularly, the invention relates to methods, software products and systems for generating X-ray pulses, activating and calibrating X-ray systems, and to related calibrated X-ray systems.

Background

In an X-ray machine, several different X-ray patterns can be generated. Depending on the application, the surgeon, the type of surgery, and/or the components used in the X-ray machine, certain X-ray patterns may be more advantageous than others. One possible X-ray pattern is a pulsed pattern, in which X-rays are generated at a predetermined duty cycle.

According to international regulations, the applied X-ray parameters should be reported to the user within a defined accuracy. In particular, for many applications (including medical and surgical applications), it is expected that the average tube current should be accurate to within 20% of the current actually applied to the tube, for any setting selectable by the user. For the continuous X-ray mode, the average tube current depends only on the amount of tube current. However, for pulsed X-ray mode, the average current is a combination of the peak tube current and the pulse width as a function of the cycle time (duty cycle) in which the peak tube current is actually applied.

Due to wiring and circuitry, cable and circuit capacity can lead to increased pulse rise times when applying voltage setting (e.g., square wave) pulses to power the X-ray tube anode. On the other hand, when the voltage is removed at the end of the pulse to terminate the X-ray exposure, the discharge of the cable and circuit capacitance currents causes the applied kilovolt voltage to decay with some delay, rather than dropping instantaneously.

When the interval is long, e.g., more than 20 milliseconds (ms), the slow rise time and extended decay time result in an error in the exposure interval on the order of one or a few percent. However, for short duration X-ray exposures, such as less than 20 milliseconds, the rise and decay times represent a significant percentage of the exposure interval.

US4454606A provides an automatic exposure control for compensating rise and decay times. However, the compensation cannot take into account changes in the X-ray generator, e.g. due to use, and time consuming recalibration of the device is usually required to compensate for such changes.

Furthermore, such inaccuracies are more difficult to predict, and settings of the X-ray system that are outside of the optimal setting range may need to be compensated for to achieve improved accuracy.

Disclosure of Invention

It is an object of embodiments of the present invention to provide a method of activating an X-ray system, a method of calibrating an X-ray system, a software implemented method of calibrating and/or activating an X-ray system, and an X-ray system, wherein the pulses are normalized and compensated for temperature variations in the X-ray source electronics, e.g. the oil surrounding the X-ray tube.

In a first aspect, the invention provides a method of providing or generating X-ray pulses by means of an X-ray system comprising an X-ray canister containing an X-ray source or tube, the method comprising:

-selecting current, voltage and desired pulse width settings for the X-ray pulses to be provided,

-compensating the selected pulse width setting for the set voltage and the tube current according to the stored normalized value at the predetermined temperature taking into account the internal temperature of the X-ray canister.

The X-ray system may comprise an X-ray generator and the compensation may be done by introducing a compensated X-ray pulse width in the X-ray generator.

An advantage of embodiments of the present invention is that deviations in pulse width caused by the influence of temperature on the electronics of the system, in particular the electronics of the X-ray canister, can be compensated for by using a predictive model taking into account the temperature. Pulse width correction improves the dose of X-rays, as well as the average current accuracy through the X-ray tube, which makes it easier to meet international standards and allows a further reduction of the minimum available pulse width.

In other words, for the selected (expected) pulse width, the actual pulse width value to be used, for example, when generating X-ray pulses using the X-ray system, may be derived from a respective one of the stored normalized values, for example, matching the normalized values determined for the tube voltage and current for the current settings of the tube voltage and current. In the present context, a "normalized value" is to be understood as a deviation or delta value between an expected X-ray pulse width and an actual X-ray pulse width normalized to a predetermined temperature. Although the normalized value is determined at a predetermined temperature (or reference temperature), the current temperature, in particular the internal temperature of the X-ray canister, may be taken into account when determining any required compensation for the actual X-ray pulse width to be set. For example, as described further herein, a predetermined temperature dependence of the pulse width deviation may be involved.

In some embodiments of the invention, the method further comprises calculating a normalized value from the stored normalized values corresponding to the first setting for current and the first setting for voltage and the stored other normalized values corresponding to the other settings for current and the other settings for voltage by interpolation, at least one of the other settings being different from the first setting value, wherein the selected current and voltage values are between the first setting and the other settings of the at least one different current and/or between the first setting and the other settings of voltage.

An advantage of embodiments of the invention is that the settings of the voltage and/or current that are not used during calibration can still be compensated by obtaining a normalized value using interpolation of the values that store the run time, thus allowing a small number of values to be stored, e.g. allowing a small LUT to be used.

In a second aspect, the invention provides a method of calibrating an X-ray system comprising an X-ray canister, wherein the X-ray canister comprises an X-ray source, the method comprising:

applying the settings for the selected current, the selected voltage and the desired pulse width to the X-ray source, thereby generating an actual voltage and current signal for the X-ray source for producing at least one X-ray pulse, thereby producing at least one X-ray pulse having an actual pulse width,

measuring an actual voltage signal applied to the X-ray source and determining an actual pulse width based on the measured actual voltage signal,

-obtaining a difference between the actual pulse width and the expected pulse width,

normalizing such difference obtained at the actual internal temperature of the X-ray canister to a normalized difference for a predetermined internal temperature of the X-ray canister, which is the ambient temperature for the electronic circuit (e.g. comprising the capacitor), thus obtaining a normalized value from such difference at the predetermined temperature taking into account the internal temperature of the X-ray canister as the ambient temperature of e.g. the capacitor, and

-storing the normalized value from the difference as a function of the settings of the selected current and the selected voltage.

For example, the X-ray system may comprise an X-ray generator and applying the settings may comprise applying the settings in the X-ray generator.

The stored normalised value can be used in the method of the first aspect of the invention. It is an advantage of embodiments of the present invention that a predictive model can be provided for compensating for temperature induced deviations in pulse width for all required voltage (kV) and tube current settings of a high voltage power supply X-ray system, e.g. an X-ray canister comprising an X-ray source. The normalized values are preferably stored in a LUT. The actual pulse width can be determined as the time interval between the moment when the actual voltage signal exceeds the predetermined threshold and the moment when the actual voltage signal falls below the predetermined threshold.

In some embodiments of the invention, the method further comprises measuring the internal temperature of the X-ray canister (i.e. the ambient temperature for the electronic circuitry of the X-ray canister) before obtaining the normalized value from the difference.

An advantage of embodiments of the invention is that it is possible to obtain with a simple temperature sensor for different settings a change in temperature which can be normalized to a predetermined temperature by a predetermined relationship between the temperature and a change in the electrical characteristics of the circuit in the tank.

In some embodiments of the invention, the method further comprises obtaining a rise and fall time deviation of the at least one X-ray pulse from a difference between the determined actual pulse width and the expected pulse width. Obtaining a normalized value from the difference at the predetermined temperature further includes obtaining normalized values of rise and fall time deviations at the predetermined temperature by using a predetermined relationship between a capacitance change of the X-ray canister and an internal canister temperature.

An advantage of embodiments of the present invention is that by calculating the change in electrical characteristics as a function of the internal temperature of the X-ray canister and the circuitry therein (e.g., high voltage converter, wiring, etc.), any reproducible rise and fall time deviations can be compensated for, thereby improving the accuracy of the average current applied to the X-ray source. Another advantage is that international regulatory requirements for current accuracy can be met more easily. Another advantage is that smaller pulse widths can be used with high accuracy.

In some embodiments of the invention, storing the normalized value from the difference between the actual pulse width and the expected pulse width comprises storing the normalized value of the rise and fall time deviations as a function of the selected current and the selected voltage.

An advantage of an embodiment of the invention is that normalized values of the rise and fall deviations can be stored without storing the pulse width or the difference thereof.

In some embodiments of the invention, the method is repeated for at least different settings of the selected current and/or voltage, whereby further normalized values from the difference are stored as a function of the different selected current and selected voltage.

An advantage of embodiments of the present invention is that a list of values for building a predictive model can be obtained.

In a particular embodiment, the method comprises calculating at least one normalized value by interpolating the current and/or voltage according to a setting of the selected current and/or voltage and a different setting of the selected current and/or voltage.

An advantage of embodiments of the present invention is that the settings of the voltage and/or current that are not used during calibration can still be compensated by obtaining a normalized value using interpolation of the values stored during calibration, without the need to provide a calculation run time, thereby saving processing time during utilization of the X-ray system.

In a third aspect, the invention provides a software product or program comprising instructions for controlling an X-ray system for providing X-ray pulses according to the method of the first aspect of the invention, further adapted to receive a desired pulse width setting, and further adapted to receive a normalized value obtained by the method of the second aspect of the invention.

The software product or program may comprise a data storage.

An advantage of embodiments of the present invention is that software can be provided, for example, in a control unit for an X-ray system and/or in an X-ray generator of an X-ray system, which can improve the performance of the system. It enables the use of pulses with smaller widths by improving the accuracy of the pulse width over a wider range of settings than the optimal range for an X-ray system alone, thus increasing the available range of voltage, current settings and allowable pulse widths. Another advantage of X-ray systems is that X-ray generation can be provided at lower power, which in turn increases the lifetime of the X-ray source. A further advantage is that international regulatory requirements for accuracy can be easily met.

In an embodiment of the fourth aspect of the invention, the software product is adapted to calibrate a pulse width of the X-ray pulses provided by the X-ray system, the software product being adapted to receive pulse width measurements and optionally also temperature measurements. When implemented in an X-ray system, the software product is adapted, e.g. comprising instructions, to perform the calibration method of the second aspect of the invention.

An advantage of embodiments of the invention is that a software product can be provided, for example comprised in a control unit for an X-ray system, which is capable of building a prediction model for compensating deviations in pulse width caused by the temperature of the X-ray system (or an X-ray canister thereof).

In a fifth aspect, the present invention provides a data store for an X-ray system comprising normalised values obtained by the method of the second aspect of the invention. An advantage of embodiments of the present invention is that the data storage can be used for calibrating different X-ray systems comprising electronic circuits having a behavior similar or identical to temperature in the X-ray canister. The data storage may be comprised in the control unit or in the software product of the third aspect.

In a sixth aspect, the present invention provides an X-ray system. The X-ray system comprises an X-ray canister comprising an X-ray tube and further comprises a control unit controllable by the software product of the third aspect of the invention (e.g. integrated in an X-ray generator unit comprised in the X-ray system). Data storage in the software product of the third or fifth aspect of the invention may also be included.

In some embodiments of the invention, the X-ray system further comprises a temperature sensor for sensing a temperature of at least a part of the X-ray canister, such as an internal temperature, for example an ambient temperature of an electrical circuit in the canister, for example a temperature of a fluid surrounding said electrical circuit.

In some embodiments of the invention, the X-ray system further comprises a data store of the fifth aspect, which is optionally a reprogrammable data store. In this case, for example, the control unit is configured to receive at least one normalized value from the data storage.

It is an advantage of embodiments of the present invention that the X-ray system comprises previously obtained normalized values for correcting the pulse width and optionally is able to calibrate itself and update the normalized values to compensate for the pulse width when needed.

A modular device comprising the X-ray system of the invention can be provided, the modular device being suitable for mobile surgical applications. An advantage of embodiments of the present invention is that an X-ray system with a large range of available pulse widths and high accuracy and effective pulses can be obtained even at low pulse energies, and also allows for a reduction in the peak energy used, so that the device can use a more compact power supply while achieving the same average power, e.g. without reducing the average power.

Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

Drawings

Fig. 1 shows an X-ray pulse having a desired shape, the actual voltages used to generate the charge beams for the photons forming the X-ray pulse, and the actual shape of the generated X-ray pulse;

FIG. 2 schematically illustrates an X-ray system according to some embodiments of the invention;

FIG. 3 illustrates a method of generating pulsed X-rays including compensating for a selected setting for X-ray generation;

FIG. 4 illustrates an exemplary relationship between a change in capacitance of an X-ray system and its ambient temperature;

FIG. 5 illustrates a calibration method according to an embodiment of the invention, including optional steps in dashed lines;

FIG. 6 schematically illustrates an X-ray system according to some embodiments of the inventions.

The drawings are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes.

Any reference signs in the claims shall not be construed as limiting the scope.

The same reference numbers in different drawings identify the same or similar elements.

Detailed Description

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The dimensions and relative dimensions do not correspond to a practical simplification of the practice of the invention.

Moreover, the terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

Furthermore, the terms top and bottom and the like in the description and the claims are used for descriptive purposes and not for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.

It is to be noticed that the term 'comprising', used in the claims, should not be interpreted as being limitative to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the term "comprising" covers the presence of the stated features only as well as the presence of these features and one or more other features. Thus, the scope of the expression "a device comprising means a and B" should not be interpreted as being limited to only devices consisting of only parts a and B. This means that the only relevant components of the device in terms of the present invention are a and B.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly, it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Moreover, although some embodiments described herein include some other features that are not included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments, as will be understood by those of skill in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

X-ray systems, including systems for medical applications, typically include an X-ray generator and an X-ray canister, which includes an X-ray source. X-ray sources, also referred to in the art as X-ray tubes, typically produce high energy X-ray photons generated by the interaction of an electron beam from a cathode and a target anode.

The electron beam is typically provided by applying a voltage between a cathode and an anode. In the pulse mode, the voltage is applied in a pulse form in which a predetermined voltage is intermittently applied. In particular, a constant voltage is applied for a time interval for the duration of the pulses, and between the pulses the voltage is insufficient to produce X-ray emission; ideally, no voltage (or zero voltage) is applied. The specific pulse parameters having the desired or expected pulse width are selected according to the application requirements, such as the type of procedure, the area to be irradiated, the patient's weight, etc.

The desired pulse may be an ideal pulse wave, such as a square wave, in which the voltage momentarily reaches a predetermined value, and also momentarily drops. However, in practical situations, a perfect pulsed wave cannot be obtained by simply applying suitable settings on the X-ray system or its X-ray generator. The voltage actually applied to the power supply takes some time to reach its desired value and reaches a minimum value after the pulse is turned off. Thus, the effective or actual pulse width may be less than the expected pulse width.

Fig. 1 shows a top curve 10 with expected X-ray pulses CTRL-X. The desired shape is defined by having a desired pulse width T_IWCurrent, voltage and width settings. The settings are applied to the system, for example by introducing the settings in the X-ray generator.

The middle curve 20 shows the variation in the actual voltage (kVact) over time through the source or tube, which generates a beam of electric charges (typically an electron beam) to generate photons that form an X-ray pulse. The actual voltage kVact comprises rising and falling edges 21, 22. These edges occur due to circuit electronics, parasitic capacitance and resistance, etc., primarily from the circuitry powering the power supply. Not all emitted photons can be considered valid when the voltage is increased or decreased. The actual parameters of the generated X-rays, in particular the width, have to be calculated taking these edges into account. By definition, X-rays are considered valid X-rays when the voltage is equal to or greater than a predetermined percentage of the set voltage. In other words, the effective width of the actual pulse (or simply the actual pulse width) is measured from the moment the voltage rises above a predetermined threshold (typically 75% of the peak value) until the moment the voltage drops to the same threshold.

The actual effective X-ray pulse xect is shown in the bottom curve 30 of fig. 1. Due to the rising edge 21, Xact starts after the control signal for the intended X-ray pulse CTRL-X has been introduced and only when the actual voltage kVact exceeds 75% of the threshold value of the set voltage kVset, at the "rise time (T)_RISE) "has passed before it is considered to be a valid X-ray. Similarly, due to falling edge 22, pulse Xact is only after CTRL-X is turned off, at "falling time (T)_FALL) After "passing, in particular when the actual voltage kVact drops below the threshold of the voltage set kVsetIs considered to be off at 75%. Actual pulse width T_EffPWIs measured from the moment the Xact starts and the Xact ends. Thus, the actual X-ray pulse, in particular its width T_EffPWRise time (T) of applied voltage_RISE) And a fall time (T)_FALL) Influence. It should be noted that compensating for the fall time is difficult because it was not previously known how long the voltage would take to fall below the threshold and would change, as shown in fig. 1.

Furthermore, when very short pulse widths, e.g. of the order of milliseconds, are used, the inaccuracy increases, because in this case the relative influence of the fixed amount of rise and fall times is greatest compared to the actual X-ray pulse at the intended setting. For very low voltage (kV) and current (mA) conditions, inaccuracy may increase. This is believed to be due to the reduced speed of the high voltage power supply and its circuitry. In particular due to the discharge index curve of the capacitor. At higher voltages, the initial part of the discharge phase of the capacitor is faster than at lower voltages. For example, 100% to 75% is 100kV to 75kV at 100kV, and 40kV to 30kV for 40kV, and thus the discharge speed is different.

Furthermore, it has been observed that temperature fluctuations of the X-ray canister lead to increased inaccuracies. Without wishing to be bound by theory, this increase is believed to be due to a change in an impedance (e.g., capacitance) parameter caused by a change in temperature of the circuitry (typically present in the tank) that provides the pulsed voltage and current to the power supply.

The present invention provides a predictive model that allows for compensating rise and fall times even for very short pulses, low voltages and currents, and in some embodiments for different temperatures. In particular, the invention allows to take into account the temperature of the electronic circuit, e.g. for variations in temperature, even before generating the X-ray pulse, correcting the settings of the X-ray generator for the pulse width as a function of the voltage and current. In some embodiments, the predictive model is capable of predicting the behavior of rise and fall times obtained from the change in electrical characteristics of the circuitry in the X-ray generator with temperature.

In a first aspect, the present invention provides a method of generating or providing X-ray pulses with a pre-calibrated X-ray system. Fig. 2 schematically illustrates such an X-ray system 200 according to some embodiments of the present invention, comprising an X-ray canister 201 and an X-ray generator 202. The tank 201 includes an X-ray source 203 and electrical circuitry 204, 205 (including transformers, capacitors, etc.) surrounded by a fluid 206 (e.g., a cooling fluid). At least one normalized value for correcting the pulse width is stored in a data storage 207 such as a memory, a software database, a look-up table (LUT), a matrix equation, or the like.

The normalized value is the deviation between the expected pulse width for a particular transistor current and voltage (kV) setting and the effective or actual pulse width at a predetermined or reference temperature. In the context of the present application, these deviation values are referred to as being "normalized" with respect to a predetermined or reference temperature. In determining the normalized value, the temperature may be controlled or measured.

By compensating the actual pulse width according to the normalized value, the expected variation of the electrical characteristic with temperature or a correction factor can be taken into account. The electrical characteristic may include an impedance (e.g., capacitance) of the circuit having a desired or known variation depending on temperature. During calibration, a normalized value may be calculated from a measurement of the difference between the actual and expected pulse widths, which is then stored. Alternatively or additionally, the normalization value may be inserted from a previously stored normalization value, for example when no matching stored normalization value is available for a particular combination of tube current and voltage.

A process flow for generating X-rays with an X-ray system, including a maintenance procedure, is shown in fig. 3. First, the voltage, current, and pulse width settings are selected 101. For example, selecting a desired width T_IWAnd introduced into the X-ray generator 202. These settings may be defined in a database for examination settings, together with voltage and current settings for the X-ray source. These settings usually depend on the type of examination, the thickness of the patient or the part of the patient body under investigation, the structure in the image area, etc., and they are usually predefined in a database. For example,the user can select the type of application (veterinarian, human, body part to be irradiated, bone or vascular settings, etc.) and/or the radiation dose, etc. The actual pulse settings for voltage, current and pulse width are applied internally by the system based on the user's selection.

The method includes accessing 102 a stored value normalized to a predetermined temperature (the stored value is referred to simply as a "normalized value") related to at least the pulse width.

The normalized values have been obtained during calibration with the selected settings of voltage, current and pulse width and are linked to the values of these settings of voltage and current. The normalized values can be obtained during a prior calibration procedure performed by the manufacturer (e.g., as part of the system's manufacture), or by a service engineer, or by the end user once the system is provided to the user. The obtained normalized values are stored in the data storage 207 as a reference to be accessed during the method of generating X-rays. The calibration is explained in more detail with reference to embodiments of the second aspect of the invention.

A normalized value for correcting the pulse width can be obtained for one or more current and/or voltage settings. The normalized value is selected when the current and voltage settings selected for generating X-rays coincide with the current and voltage settings for which a normalized value has been stored in the data storage 207.

In some embodiments, when the current and voltage settings selected for generating X-rays do not correspond to the values of the current and voltage settings already stored in the data storage, normalized values are inserted 106. Thus, the normalized value for the selected setting is calculated by inserting the normalized values for the closest higher setting and the closest lower setting. For example, the selected voltage and current settings may not correspond to any values used to obtain the normalized values. In this case, two normalized values are selected, namely the value corresponding to the voltage setting between which the selected voltage setting falls and the closest current setting. The normalized values for the selected current and voltage settings are calculated by interpolating the normalized values of the two selected voltage settings. A similar procedure would apply if it were necessary to insert a normalized value based on the closest higher and lower current settings or a combination of voltage and current settings. In some embodiments, a voltage/current curve is selected and the interpolated value is calculated based on the selected voltage (the current associated therewith).

In some embodiments, linear interpolation can be used. However, other types of interpolation can be used in embodiments of the invention, for example, where several voltage settings for a particular voltage/current curve are used. It should be noted that if interpolation is performed during application of X-rays, a small number of normalized values need to be stored, thereby reducing the size of the data memory 207. However, interpolation during calibration is also possible, reducing run-time calculations at the expense of a larger data memory 207.

The at least one normalized value can be used to correct or compensate 103 the width of the pulse (e.g., the width of a CRTL-X pulse) before providing the pulse to the X-ray source. Thus, during application, the X-ray settings (e.g., pulse width) can be updated prior to providing the voltage pulses using the stored normalized values for the predetermined temperature by applying 104 the compensated settings to the source (e.g., to actually achieve a pulse width correction for the expected pulse width at the temperature for the selected voltage and current settings). The updating can be done with a programmed control unit 208, for example inside or outside the X-ray generator. The unit 208 may comprise a data storage 207; however, the updating can also be done with an algorithm comprising instructions to control and adjust the parameters, e.g. in an X-ray generator comprising the data storage 207.

In order to correctly consider the influence of temperature on the electronic properties of the tank, in particular the electric properties of the high-voltage capacitor and/or the smoothing capacitor, the following information can be used:

-an expected change of one or more electrical characteristics of the circuit in the tank with temperature, and

-the temperature of the electronic circuit.

This temperature can be controlled by a heating and/or cooling subsystem 210 (shown in fig. 2) which controls the temperature of the electrical circuits 204, 205 (e.g. the temperature of their environment, e.g. the temperature of a fluid 206 such as transformer oil in contact with the electrical circuits), so that the actual temperature is the predetermined temperature at which the value related to the pulse width is normalized. In this case, the value can be used as a normalized value to directly correct or compensate 103 the setting (e.g., width) of the pulse before applying the pulse. The normalized value may be, for example, the difference between the actual pulse width obtained by calibration and the measured pulse width, and is normalized to a predetermined temperature, and thus can be directly applied to the pulse width setting when the X-ray canister is set at the predetermined temperature without performing calculation to obtain the normalized value.

Alternatively or additionally, the temperature of the circuit can be measured 105. For example, a temperature sensor 209 (shown in fig. 2) can measure 105 the temperature of the X-ray canister prior to applying the pulse, and thus can take into account the electrical characteristics when compensating 104 the settings. The temperature of the tank 105 can be measured by measuring the ambient temperature around the high voltage converter 204 and/or the High Voltage (HV) and smoothing capacitor 205 in the tank, for example measuring the temperature of the surrounding fluid 206 (e.g. transformer oil).

In embodiments where temperature is measured, the electrical characteristics (taking into account the power supply's capacitors, cables, etc.) and the expected change in temperature are known, so a correction factor for the electrical characteristics (e.g., impedance, capacitance) can be used to account for the rise and fall times caused by the circuit, while accounting for the different behavior of the circuit as the temperature changes.

It is emphasized that the relationship between the electrical characteristic and the temperature can be used for normalization during calibration (as will be seen in the second aspect), as well as during application of the temperature measurement, to effectively convert the pulse width correction from normalization to the actual temperature.

FIG. 4 shows a graph of an exemplary relationship 400 between the change in capacitance of X-rays measured as a percentage change (and therefore, a capacitance correction factor) and the ambient temperature in degrees Celsius. Providing such a relationship can be done theoretically or empirically. In other words, the temperature dependence of the electrical characteristics can be known from the specifications of the circuit component manufacturer, it can be obtained from the type of capacitors and elements in the X-ray generator, from a data table, etc.; or capable of measurement processing; or both, for fine tuning. During application, a change in capacitance related to the temperature of the circuit (e.g., can) is obtained, and a value related to the pulse width is "de-normalized," thereby enabling compensation 103 of the pulse width.

Finally, the compensated settings can be applied 104 to the source to obtain X-ray pulses (e.g., a train of X-ray pulses to provide pulsed X-ray generation) having a corrected pulse width that more closely corresponds to the desired width than would be obtained if the settings were simply used. For example, the corrected pulse width may match the expected width.

Furthermore, the fall time can be updated by measuring the temperature run time and updating a normalized value, which may change over time due to degradation of the X-ray source and/or the X-ray canister. This reduces the need for recalibration and the need for service engineers. The method is similar to that described, but does not introduce defined voltage and current settings.

In a second aspect, the present invention provides a calibration method based on a predictive model for compensating the rise and fall times of the rising and falling edges 21, 22 (shown in fig. 1) of the pulses. The method includes providing at least one pulse (e.g., a train of pulses) having predetermined current and voltage settings to obtain a pulse having a desired width, measuring an actual pulse width, obtaining a difference between the desired pulse width and the actual pulse width, and normalizing a value at a predetermined temperature. Normalization can be accomplished by setting the temperature of the circuit to a known value (e.g., a predetermined normalized value), or by measuring the temperature (e.g., with a sensor) and then normalizing the value at the predetermined temperature. From the difference between the temperature and the width, the influence of the temperature on the rise and fall times caused by the circuit can be considered. The normalized values obtained from the measured values are stored in a data memory 207, for example in a LUT. This can be repeated for a plurality of values of voltage, current or a combination of voltage and current, thereby obtaining normalized values corresponding to different settings of current and voltage. In principle, these settings are valid for a wide range of pulse widths.

An example of such a calibration procedure is shown in fig. 5. First, settings are selected and introduced 501 in the X-ray system (e.g. via a user interface or a database, e.g. in the X-ray generator 202) to provide a predetermined shape CTRL-X, in particular a predetermined intended pulse width T_IWOf (2) is performed. These settings may include voltage, current, and desired pulse width.

A setting is applied 502 to the source 203, the source 203 is activated and provides at least one pulse. Subsequently, the actual voltage signal applied to the X-ray source is measured 503. The measurement can be done with a subsystem for measuring voltage, e.g. an electronic circuit in the control unit 208, or e.g. in the X-ray generator 202, etc.

Based on the measurement, the actual pulse width is determined 504. The actual pulse width can be determined 504 as the time interval between the instant the actual voltage signal exceeds the predetermined threshold and the instant the actual voltage signal falls below the predetermined threshold.

In other words, the rise time T of the voltage signal can be determined_RISEAnd a fall time T_FALLTaking into account, the effective width of the actual X-ray pulse ("actual pulse width") is thus determined 504 taking into account the time interval between the voltage exceeding a predetermined threshold (conventionally 75% of the voltage fixed in the setup) and the moment when the voltage falls below the predetermined threshold.

The desired pulse width (T) is then obtained 505_IW) And the actual pulse width (T)_effPW) The difference between them.

Further, the temperature of the circuit is considered 506. This may be done by obtaining the temperature of the circuit, may include setting the temperature to a predetermined value before applying 502 the setting to the source, or may include measuring the temperature of the circuit while applying 502 the setting to the source and generating the pulse.

Setting the temperature may include heating or cooling the temperature of the circuit, e.g., the temperature of the surrounding fluid (e.g., oil in a tank) during the period of the electrons, using a heater or cooler, as explained previously. Measuring the temperature may comprise (as also explained before) measuring the ambient temperature of the electronic device, e.g. the ambient temperature of the converter, e.g. the HV and the smoothing capacitor, e.g. by sensing the temperature of the fluid of the tank, e.g. with a temperature sensor 209 comprising a sensing probe.

The difference between the actual width and the intended width may then be normalized 507 to a predetermined temperature, such as the temperature of the circuit set by the user, or a temperature typically found in transformers, such as room temperature (e.g., between 20 ℃ and 40 ℃, such as 25 ℃).

Not only the rise and fall times can be compensated, but also the influence of the electrical characteristics in the rising and falling edges with temperature variations. In particular, the rise and fall times depend on the electrical characteristics (e.g., impedance, e.g., capacitance) of the specific circuitry of the X-ray canister (including transformers, capacitors, cables), which in turn depend on temperature. Thus, as has been explained before, the change in the electrical characteristic, such as impedance, can be obtained 508 by measurement or from the specifications of the circuit manufacturer. A normalized value can then be obtained 509 from the measurement of the actual pulse width and the expected pulse width taking into account the temperature of the X-ray canister and the previously obtained 508 change in electrical characteristics.

For example, the change in capacitance of the HV and smoothing capacitor with temperature can be obtained 508 or known, as shown in fig. 4. The rise and fall times over temperature are obtained 509 from the change in capacitance as a percentage over temperature. The measured temperature shows the change in nominal capacitance in curve 400. The normalized value is obtained by calculating such a change for a predetermined temperature.

The obtained normalized value is stored 510, for example in the data storage 207, together with the current and voltage settings at which the normalized value was obtained.

The cycle can be repeated for a plurality of settings. In general, the current setting and the voltage setting can be selected differently, for example, for different settings (e.g., high current and low current).

For example, a normalized value can be provided for a few voltage settings, linked to a predetermined value of the current setting, and the same cycle can be repeated for the same few voltage settings, linked to a predetermined but different current setting. This means that calibration can only be provided for a few voltage and current settings, so that values of the voltage or current settings that are not selected for calibration are not assigned to their normalized values.

In some embodiments of the invention, it is still possible to insert 511 those normalized values corresponding to values of the voltage or current settings not selected for calibration from the normalized values of the selected settings, in a manner similar to the insertion performed with reference to embodiments of the first aspect, e.g. from values obtained with voltage values above or below the unselected settings, but closest to the unselected settings. When performing such an insertion during calibration, a larger data memory 207 is required, but processing time is saved during utilization of the X-ray system.

In any case, the insertion can be done during calibration, and if desired, also during run-time if the selected setting is not between those used to obtain the normalized value or the normalized values inserted during calibration.

In the following, exemplary program steps for calibration and subsequent application flow are provided:

exemplary steps for calibration:

obtaining voltage, current and desired pulse width settings

Transmitting pulses

Measuring the actual (effective) width of the pulse

Measuring the ambient temperature of the internal circuit of the tank

Comparing the deviation between the effective pulse width and the expected pulse width by:

calculating an expected change in capacitance of a capacitor in the high voltage converter from the measured temperature, and using the actual capacitance (normalization) to obtain the rise time and fall time deviations of the pulses for a defined temperature

The rise time and fall time offsets and temperatures are stored in the LUT for the selected voltage and current settings.

Exemplary steps for the application flow:

introducing voltage and current settings and width of expected pulse width taking into account normalized compensation

Measuring temperature

Obtaining an expected change in capacitance as a function of temperature compared to capacitance at a predetermined temperature

Obtaining the required compensation for the rise and fall times that can be expected from the voltage and current settings and the expected change in the capacitance

Applying voltage and current settings and widths (including non-normalized compensation) to transmit corrected pulses

Table I below shows exemplary values set and normalized values obtained for a plurality of calibration settings in a particular calibration method for measuring the temperature of a tank. The voltage, current and expected pulse width, as well as the predetermined temperature Tp are values set by the user, while the effective pulse width and temperature are measured, and then the difference between the pulse width (Delta) and the normalized value NV is calculated.

Table i. calibration file.

For table I, two curves (a and B) with different current settings were used. For each curve, the expected pulse width is 10ms, but the effective width of the actual pulse (obtained from the measured actual voltage) is different for each setting. The difference (Delta) is derived from the difference between the expected pulse width and the effective pulse width:

Delta D＝T_IW-T_EFFPW

the temperature was measured for each setting and the normalized value of Delta was obtained from Delta by normalizing to Tp-25 ℃ using the relationship of fig. 4:

normalized value NV ═ D (1+ (0.005(T-Tp))

In this case, the relationship is linear, but in other cases, NV can be calculated using different factors depending on the circuit components.

Table II below shows an example correction for pulse width in the "CTRL-X programmed APW" column, using the normalized values of table I, for each of curves a and B. It should be noted that each voltage setting is linked to a current setting in curve a and a different current setting in curve B. In the case of table II, the number of voltage settings that have been selected is greater than the voltage settings used for calibration, so interpolation is used to obtain an intermediate value (interpolated NV).

In this case, linear interpolation is used. The temperature (Tm) is also measured, the predetermined temperature Tp of the normalized value being the same as in the calibration. Linear interpolation is done based on the value of the voltage setting, but a different linear interpolation is done for each current setting (each curve A, B). The difference in linear interpolation between the curves depends on the difference in current (or curve shape). The measured temperature Tm causes a change in percentage. A different desired pulse width is selected for each setting of curve a and each setting of curve B.

TABLE II calibration based on stored normalization values

The voltage V has been chosen to range between 41 and 50. Thus, for each curve (each different mA setting), the inserted normalized values are inserted from the normalized values obtained for the settings of 40kV and 80kV, respectively, -5.4 and-2.2 for curve A, and-1 and 0 for curve B (see Table I).

In each case, the linear interpolation is:

for curve a, interpolated NVIntNV ═ 5.4+ (V-40 kV) (-2.2- (-5.4))/(80kV-40kV),

for curve B, interpolated NV IntNV ═ 1.0+ (V-40 kV)/(80kV-40kV),

in the case of curve a, the actual temperature of the circuit (for example the tank) is constant, equal to 40 ℃. In the case of curve B, there is a change in the measured value of the circuit temperature. The predetermined temperature Tp for normalization (25 ℃ in this case) is again used to obtain the actual Delta correction Dc, which should be applied as:

Dc＝IntNV(1-(0.005(Tm-Tp))

finally, delta correction is used to obtain the Actual Pulse Width (APW) that the user needs to program for the desired pulse width TIW:

CTRL-X programmed APW ═ T_IW+Dc

It is therefore clear that the calibration method of the second aspect can be used to provide a normalized value for use in the method of providing X-ray pulses of the first aspect of the invention.

In a third aspect, the invention provides a software product, such as a computer program product, or a data carrier comprising such a program, such that when linked to an X-ray system, the software product allows the method according to the first aspect of the invention to provide X-ray pulses.

The software product may be adapted to receive the required pulse width setting and also to receive the normalized value obtained by the calibration method of the second aspect of the invention.

An X-ray system comprising such a software product (e.g. in the control unit 208 or in the X-ray generator 202) can improve the performance of the system, enabling the use of pulses of small width, thereby increasing the usable range. The control unit also allows the generation of X-rays at lower power, which in turn increases the lifetime of the X-ray source. Moreover, international regulatory requirements for accuracy can be more easily met, since the difference between the expected pulse and the obtained pulse is reduced for the same voltage and current settings. This also helps to increase the usable range of pulse widths in the lower range, for example to provide accurately small widths (very short pulses).

In a fourth aspect of the invention, a software product for calibrating an X-ray system is provided. The software product may be adapted to receive pulse width measurements, it may optionally be adapted to receive temperature measurements, and it may comprise instructions for performing the calibration method of an embodiment of the second aspect of the invention when implemented in an X-ray system. Such a software product enables to build a predictive model for compensating deviations in pulse width including temperature variations of the canister, thereby providing a pulse width compensated X-ray system when the software is implemented in the X-ray system.

A software product according to an embodiment of the invention may comprise the third and fourth aspects of the invention, thereby allowing to calibrate the X-ray system and to provide pulsed X-rays with a corrected pulse width obtained during calibration.

In a fifth aspect, the present invention provides a data store comprising normalised values obtained by the method of the second aspect of the invention. Such a data storage may be linked to a control unit, for example a unit comprising a software product according to an embodiment of the third and/or fourth aspect of the invention. In some embodiments, the data store is implemented in software. For example, it may be implemented as part of the software product of the third and/or fourth aspect of the invention.

Such a data store may be reprogrammable and can comprise updated normalized values, for example by interpolation or by a calibration method according to an embodiment of the second aspect of the invention.

In a sixth aspect, the invention provides an X-ray system adapted to generate pulses with an effective width, to be compensated for different values of voltage or current settings and independently of temperature, according to embodiments of the first aspect, and/or for performing the calibration described with reference to embodiments of the second aspect. For example, the X-ray system may comprise a software product or a program product according to embodiments of the third and/or fourth aspect of the invention.

The voltage range provided by the X-ray system may be between 35kV and 150kV, for example between 40kV and 120 kV. Conventional X-ray systems have an optimum setting which is very much in line with the effective pulse, for example typically between 70kV and 80 kV. The deviation between the expected and effective pulse width increases for higher and lower kV settings. The invention provides an efficient correction of pulse width for a wider range of voltage and current settings, even for very low current and/or voltage values, which allows to optimize the dose and to reduce the wasted power. Since the pulse width is more accurate, an average current with higher accuracy can be obtained that meets the specifications of current and voltage accuracy, and in turn a smaller pulse width can be achieved.

Turning to fig. 2, an illustrative embodiment of such an X-ray system 200 is shown, which includes an X-ray generator 202 and an X-ray source 203 contained in a canister 201. In the specific example of this figure, the X-ray system 200 includes a high voltage converter 204 and HV and smoothing capacitor 205 surrounded by a fluid 206. For example, at least the converter 204 and smoothing capacitor 205 may be surrounded by oil (e.g., transformer oil), for example, in the tank 201, and the tank 201 may further include the source 203. A control unit 208 is included which may comprise a software program according to an embodiment of the third aspect of the invention. The control unit 208 may be external as shown, or internal, e.g. as an integral part of the X-ray generator 202. The data memory 207 may comprise a normalized value for adjusting the pulse width according to an embodiment of the first aspect. And (5) carrying out the following steps. The data storage 207 may optionally be part of the control unit 208. The data store may be reprogrammable to provide additional normalized values by measuring it from an actual pulse or by interpolating it from known values.

The X-ray system may be adapted to take into account the temperature of the circuitry (e.g. the high voltage converter, and/or the HV and smoothing capacitor) or parts thereof used to provide the pulses. In some embodiments, the temperature can be measured by a temperature sensor 209, the temperature sensor 209 comprising any sensor that measures a parameter as a function of temperature. For example, the temperature sensor may include an element that measures a change in resistance of the conductor due to a change in temperature. In some embodiments of the invention, the ambient temperature of the circuit in the tank is measured. For example, HV and the temperature of the smoothing capacitor 205 can be measured. For example, the temperature of the environment surrounding the circuitry of the high voltage converter 204 or the circuitry of both the converter 204 and the smoothing capacitor 205 can be measured, optionally including wiring or the like. In some embodiments, the environment surrounding at least a portion of the electrical circuit is a fluid 206, such as oil (e.g., transformer oil, commonly used for cooling, although the invention is not limited to cooling functions). The temperature of the fluid is an important indicator of the ambient temperature, especially where this fluid 206 surrounds the HV and smoothing capacitors 205, since these capacitors play a major role in the shape of the voltage pulse and its edges 21, 22. Thus, in embodiments of the present invention, the fluid temperature is measured, for example, in the immediate environment of the smoothing capacitor, for example, using one or more NTC thermistors, thermocouples, or the like.

In some embodiments, the fluid can be circulated to provide an evenly distributed temperature in the tank. For example, an oil pump may be included. Cooling, such as passive cooling, may be implemented.

In an alternative embodiment, to account for the temperature of the electrical circuit, the system 200 includes a heating and/or cooling temperature subsystem 210, such as a heater and/or heat sink, for setting the temperature 206 of the fluid. In this case, the temperature sensor 209 can still optionally be present. The subsystem 210 may be actuated by the X-ray system, e.g. by its control unit 208, e.g. during calibration and/or during use of the X-ray system.

The X-ray system may include a subsystem 211 for measuring the effective width of the actual pulses provided during calibration. For example, subsystem 211 may include electronic circuitry in control unit 208 and/or in the X-ray generator. The actual voltage level in the X-ray canister can be measured and the measurements can be processed (e.g., in a system controller, control unit, etc.) to determine the signal level.

The X-ray system 200 may be comprised in one whole, integrating at least the tank 201, optionally also the X-ray generator 202, in a single block, which can be part of, for example, a CR unit, a mammography unit, a mobile X-ray imaging device for mobile surgical applications, to which the invention is not limited.

Fig. 6 shows an assembly 600, which may be stationary or movable, comprising an X-ray canister 201 containing a source 203 and a detector 601 arranged remote from the source 203, for example in a rotatable tomography setup. Comprising an X-ray generator 202, said X-ray generator 202 for example comprising data storage and executable instructions for performing the methods of the first and second aspects of the invention.