阅读说明：本技术 确定参考系的有效性的方法，医学系统和计算机程序产品 (Method, medical system and computer program product for determining the validity of a reference system ) 是由 菲利普·梅韦斯 冈特·米勒 于 2019-07-10 设计创作，主要内容包括：本发明涉及一种用于在对患者进行介入手术期间确定在参考结构与解剖结构之间的参考系的有效性的方法,一种所属的医学系统以及一种所属的计算机程序产品。根据本发明的用于在对患者进行介入手术期间确定在参考结构与解剖结构之间的参考系的有效性的方法具有以下步骤：-借助于X射线装置在介入手术期间在第一时刻检测患者的第一图像数据组,其中第一图像数据组具有参考结构、解剖结构以及参考系；-借助于X射线装置在介入手术期间在第二时刻检测患者的第二图像数据组,其中第二图像数据组至少具有参考结构；-将第二图像数据组配准于第一图像数据组上；并且借助于所配准的第二图像数据组与第一图像数据组的比较,确定参考系的有效性。(The invention relates to a method for determining the validity of a reference frame between a reference structure and an anatomical structure during an interventional procedure on a patient, to an associated medical system and to an associated computer program product. The method according to the invention for determining the validity of a reference frame between a reference structure and an anatomical structure during an interventional procedure on a patient has the following steps: detecting a first image data set of the patient at a first point in time during the interventional procedure by means of an X-ray device, wherein the first image data set has a reference structure, an anatomical structure and a reference frame; detecting a second image data set of the patient at a second point in time during the interventional procedure by means of the X-ray device, wherein the second image data set has at least a reference structure; -registering the second image data set on the first image data set; and determining the validity of the reference frame by means of a comparison of the registered second image data set with the first image data set.)

1. A method for determining the effectiveness of a reference frame (B) between a reference structure (R) and an anatomical structure (a) during an interventional procedure on a patient (P), the method having the steps of:

detecting a first image data set (B1) of the patient (P) by means of an X-ray device (13) at a first time during the interventional procedure, wherein the first image data set (B1) has the reference structure (R), the anatomical structure (A) and a reference frame (B) between the reference structure (R) and the anatomical structure (A),

detecting a second image data set (B2) of the patient (P) by means of the X-ray device (13) at a second time instant during the interventional procedure, wherein the second image data set (B2) has at least the reference structure (R),

-registering the second image data set (B2) to the first image data set (B1), wherein a reference structure (R) depicted in the first image data set (B1) and a reference structure (R) depicted in the second image data set (B2) are input as input parameters into the registration, and wherein the registered second image data set (B2') is determined as a result of the registration, and

-determining the validity of the reference system (B) by means of a comparison of the registered second image data set (B2') with the first image data set (B1).

2. The method of claim 1, wherein the first and second light sources are selected from the group consisting of,

wherein the reference structure (R) has at least one image marking, a first fastening means and a holding structure, wherein the at least one image marking is releasably connected to the holding structure by means of the first fastening means.

3. The method according to any one of the preceding claims,

wherein the reference structure (R) has a second fixing mechanism and a holding structure, wherein by means of the second fixing mechanism the holding structure is connected with the patient (P), and wherein by means of the connection between the holding structure and the patient (P) the reference system (B) between the reference structure (R) and the anatomical structure (A) is initially specified.

4. The method according to any one of the preceding claims,

wherein the reference structure (R) has at least one image marker absorbing X-rays, and wherein registering the second image data set (B2) to the first image data set (B1) comprises: -determining the reference structure (R) by means of at least one image marker depicted in the first image data set (B1) and at least one image marker depicted in the second image data set (B2).

5. The method according to any one of the preceding claims,

wherein the comparing comprises: a third image data set (B3) is determined by means of the first image data set (B1) and the registered second image data set (B2').

6. The method of claim 5, wherein the first and second light sources are selected from the group consisting of,

wherein determining the third image data group (B3) comprises weighting the first image data group (B1) and the registered second image data group (B2').

7. The method according to any one of claims 5 to 6,

wherein determining the validity comprises: visualization of the third image data set (B3) on a display unit (14).

8. The method according to any one of claims 5 to 7,

wherein determining the validity comprises: pixel-dependently classifying the third image data set (B3) into at least two classes according to a deviation from the reference frame (B), thereby determining pixel-dependent classification values, and wherein the pixel-dependent classification values are visualized on the display unit (14) as an overlay with the first image data set (B1), the registered second image data set (B2') and/or the third image data set (B3).

9. The method according to any one of claims 5 to 8,

wherein determining the validity comprises: invoking a threshold, segmenting the third image data set (B3), calculating a segmentation related value in the segmented third image data set, and comparing the segmentation related value to the threshold.

10. The method according to any one of the preceding claims,

wherein during the interventional procedure the detection of the first image data set (B1) of the patient (P) by means of the X-ray device (13) at the first moment in time and/or the detection of the second image data set (B2) of the patient (P) by means of the X-ray device (13) at the second moment in time is carried out at a vertebra of the patient (P), and wherein the reference structure (R) is connected with a vertebra of the vertebra prior to the method for determining the validity.

11. The method according to any one of the preceding claims,

wherein when the second image data set (B2) has the reference structure (R) and the anatomical structure (A), the anatomical structure (A) depicted in the second image data set (B2) is registered to the anatomical structure (A) depicted in the first image data set (B1) or in a fourth image data set in relation to determining the validity of the reference system (B).

12. The method according to any one of the preceding claims,

wherein, when the second image data set (B2) has the reference structure (R) and the anatomical structure (A), a measurement region of a fifth image data set is defined in dependence on the reference structure (R) and the anatomical structure (A) depicted in the second image data set (B2).

13. A medical system (11) having:

-a computing unit (10) configured for the method according to any one of the preceding claims, and

-an X-ray device (13).

14. The medical system (11) according to claim 13,

wherein the X-ray device (13) has a C-arm (15).

15. A computer program product directly loadable into the memory of a computing unit (10), having program code means for implementing the method as claimed in any one of claims 1 to 12 when said computer program product is run in said computing unit (10).

Technical Field

The invention relates to a method for determining the validity of a reference frame between a reference structure and an anatomical structure during an interventional procedure on a patient, to an associated medical system and to an associated computer program product.

Background

The different units of the medical system are typically used during an interventional procedure on a patient. Such units may be, for example, patient tables, X-ray devices, C-arms, cameras and/or medical instruments. The different units of the medical system usually have different coordinate systems independent of each other. The coordinate systems which are independent of one another are preferably related by means of at least one transformation rule, whereby the units of the medical system can be collision-free and/or can cooperate, for example for medical imaging in which the patient table and/or the X-ray device and/or the medical instrument can be moved relative to one another. The patient typically has a patient coordinate system, which can be detected and/or specified, for example, in medical imaging. Preferably, the patient coordinate system is associated with an image coordinate system of an image data set detected in the medical imaging.

Typically, the registration is performed between the patient coordinate system and the coordinate system of the medical system before and/or during the interventional procedure. For example, a reference structure is fixed for this purpose at the patient, in particular at the anatomy of the patient. It is generally assumed that the reference structure is fixedly and/or rigidly connected and held with the patient, thereby defining a reference frame between the reference structure and the anatomical structure. The reference structure is preferably connected to the patient by means of a fixing mechanism. The reference structure typically enables a better registration than if only the anatomical structure is registered. Now, at least one transformation rule is specified based on the registration between the patient coordinate system with the reference frame and the coordinate system of the medical system.

However, the above assumption may not be applied in certain cases. Since the connection between the reference structure and the anatomical structure may be released and/or moved, for example when the user of the medical system collides with the reference structure and/or the fixation mechanism is released during the interventional procedure. In this case, the reference frame may lose its validity, wherein a further reference frame is defined between the reference structure and the anatomical structure and is valid. When the reference frame becomes invalid, the at least one transformation rule is typically no longer valid as such. Therefore, a renewed time-consuming registration between the other patient coordinate system with the other reference system instead of the reference system and the coordinate system of the medical system is usually followed.

In order to verify the above assumptions, a "rationality check" for determining the validity of the reference frame is usually performed during the interventional procedure, which the user of the medical system manually verifies: to what extent the validity of the reference system also applies. Manual verification typically includes: placing a medical instrument on the anatomical landmark, wherein the medical instrument is detected, for example, by means of a camera and simultaneously displayed on a display unit in superimposition with the image data set with the anatomical landmark, and wherein a user visually verifies: whether the medical instrument has the same position in the overlay of the anatomical landmark relative to the image data set and in reality. At least one transformation rule between the coordinate systems, in particular the patient coordinate system, and the coordinate system of the medical system is also particularly effective when the positions are the same.

The anatomical landmark may be a well-accessible and/or free anatomical bone of the patient with clearly identifiable features, such as a nasal and/or vertebral protrusion. In this connection, manual inspection is disadvantageous, since anatomical landmarks must be available for mechanical contact and/or the accuracy of the inspection is related to the clearly identifiable features and/or to the granularity of the features and/or to the subjective visual inspection by the user. Furthermore, during manual inspection, the optically detected medical instrument must be kept still.

Disclosure of Invention

The invention is based on the following objectives: improved feasibility for determining the effectiveness of a reference frame is presented.

The object is achieved by the features of the invention. Advantageous embodiments are described in the following description.

The method according to the invention for determining the validity of a reference frame between a reference structure and an anatomical structure during an interventional procedure on a patient has the following steps:

detecting a first image data set of the patient at a first point in time during the interventional procedure by means of an X-ray device, wherein the first image data set has a reference structure, an anatomical structure and a frame of reference between the reference structure and the anatomical structure,

detecting a second image data set of the patient at a second point in time during the interventional procedure by means of the X-ray device, wherein the second image data set has at least a reference structure,

-registering the second image data set to the first image data set, wherein the reference structure depicted in the first image data set and the reference structure depicted in the second image data set are input as input parameters into the registration, and wherein the registered second image data set is determined as a result of the registration, and

determining the validity of the reference system by means of a comparison of the registered second image data set with the first image data set.

The method according to the invention has the following advantages, among others:

the comparison of the registered second image data set with the first image data set preferably enables: the validity of the reference frame is determined by manual verification by a user of the medical system without the aid of medical instruments. In other words, according to the method for determining the validity of the reference frame, an alternative "plausibility check" can be achieved, in particular without mechanically contacting anatomical landmarks by means of medical instruments. Advantageously, the selection of anatomical landmarks that must be accessible to the medical instrument and/or the medical instrument remaining stationary during the performance of a visual check of the effectiveness by a user of the medical system is accordingly omitted.

Another advantage may be: the validity of the reference frame is determined purely image-based and/or quantitatively. It is therefore preferred that smaller movements of the reference structure can be identified than in the case where the validity of the reference frame is determined visually.

The validity of the reference frame is advantageously determined faster than in the case where a manual check is performed. Typically, time savings are associated with cost advantages.

One embodiment provides that the reference structure has at least one image marking, a first fastening means and a holding structure, wherein the at least one image marking is releasably connected to the holding structure by means of the first fastening means. The described embodiment offers the following advantages, among others: the validity of the reference frame can be determined when the at least one image marker is released from the first securing mechanism.

One embodiment provides that the reference structure has a second fixing mechanism and a holding structure, wherein the holding structure is connected to the patient by means of the second fixing mechanism, and wherein a reference frame between the reference structure and the anatomical structure is initially defined by means of the connection between the holding structure and the patient. It can advantageously be determined that: when the connection between the holding structure and the patient has been loosened and/or moved, the reference frame typically becomes invalid.

One embodiment proposes that the reference structure has at least one image marker which absorbs X-rays, and wherein registering the second image data set to the first image data set comprises determining the reference structure by means of the at least one image marker depicted in the first image data set and the at least one image marker depicted in the second image data set. In this connection, the embodiment is advantageous in that the at least one image marker absorbing X-rays can have a higher contrast than the anatomical structure in the first image data set and/or the second image data set, whereby the registration typically becomes more accurate and/or simplified.

One embodiment provides that the comparison comprises a determination of the third image data set by means of the first image data set and the registered second image data set. Advantageously, the first image data set and the registered second image data set can be at least partially superimposed in the pixel region, so that the pixel region is similarly superimposed in the third image data set with the first image data set and/or the registered second image data set.

One embodiment provides that determining the third image data set comprises weighting the first image data set and the registered second image data set. Advantageously, the embodiments enable a fast determination of the validity of the reference frame. A further advantage may be that pixel regions with anatomical structures are weighted differently from pixel regions with reference structures in accordance with the structures depicted in the first image data set and/or the registered second image data set.

An embodiment provides that the determination of the validity comprises a visualization of the third image data set on a display unit. Preferably, the user can see the third image data set on the display unit.

One embodiment provides that the determination of the validity comprises a pixel-dependent classification of the third image data set into at least two classes as a function of the deviation from the reference frame, whereby a pixel-dependent classification value is determined, and wherein the pixel-dependent classification value is visualized on the display unit as an overlay with the first image data set, the registered second image data set and/or the third image data set. In this connection, the embodiment is advantageous in that the pixel-dependent classification values show the following pixel regions to the user: the pixel regions have, for example, a small or large deviation from the initially performed registration. In other words, the third image data set can be classified such that the user of the medical system can evaluate according to the pixel-dependent classification value: to what extent it makes sense to continue the interventional procedure without re-registration.

One embodiment provides that determining the validity comprises invoking a threshold, segmenting the third image data set, calculating a segmentation related value in the segmented third image data set, and comparing the segmentation related value to the threshold. The embodiment enables a standardized and thus reproducible determination of the validity of the reference frame. Another advantage of the described embodiment may be that the determination of effectiveness is quantifiable and/or therefore comparable.

One embodiment provides that a first image data record of the patient is acquired at a first point in time by means of the X-ray device and/or a second image data record of the patient is acquired at a second point in time by means of the X-ray device during the interventional procedure, and the reference structure is connected to the vertebrae of the spine prior to the method for determining the validity. Advantageously, the embodiments enable surgery at a spine of a patient. Another advantage may be a reduction in the examination duration of an interventional procedure performed on a patient.

An embodiment provides that, when the second image data set has a reference structure and an anatomical structure, the anatomical structure depicted in the second image data set is registered to the anatomical structure depicted in the first image data set or in the fourth image data set in connection with determining the validity of the reference frame. The registration especially yields a further transformation rule. The described embodiment offers the following advantages, among others: at least one transformation rule continues to be valid after being extended with another transformation rule without a renewed time-consuming registration between the patient coordinate system having another reference system instead of the reference system and the coordinate system of the medical system. In other words, the at least one transformation rule between the coordinate systems is advantageously adjusted solely on the basis of the difference between the reference system and the further reference system, which generally takes place faster than a renewed time-consuming registration between the further patient coordinate system and the coordinate system of the medical system.

One embodiment provides that, when the second image data set has a reference structure and an anatomical structure, the measurement region of the fifth image data set is defined in relation to the reference structure and the anatomical structure depicted in the second image data set. In this connection, the embodiment is advantageous because the expansion of the measurement region is generally associated with the dose of X-rays determined for the fifth image data set.

The medical system according to the invention has a computing unit and an X-ray device.

One embodiment provides that the X-ray device has a C-arm. The C-arm preferably enables a fast detection of the volumetric image data set.

The computer program product according to the invention, which can be loaded directly into the memory of the computing unit, has program code means for implementing the method according to the invention when the computer program product is run in the computing unit.

The computer program product may be or comprise a computer program. The computer program product has, inter alia, program code means which delineate the method steps according to the invention. The method according to the invention can thus be carried out in a defined and reproducible manner, and monitoring can be carried out by passing the method according to the invention. The computer program product is preferably configured such that the computing unit is capable of carrying out the method steps according to the invention by means of the computer program product. The program code means can be loaded in particular into a memory of a computing unit and is typically run by means of a processor of the computing unit by accessing the memory. All embodiments of the method according to the invention can typically be performed when the computer program product, in particular the program code means, is run in a computing unit. The computer program product is stored, for example, on a physical, computer-readable medium and/or stored digitally as data packets in a computer network. The computer program product may be a physical, computer-readable medium and/or a data package in a computer network. Thus, the present invention may also be directed to physical, computer-readable media and/or data packets in a computer network. The physical, computer-readable medium can typically be connected directly to the computing unit, for example, by: the physical computer-readable medium is inserted into the DVD drive or is inserted into the USB interface, so that the computing unit can access the physical computer-readable medium, in particular, in a read-out manner. The data packet is preferably capable of being invoked by a computer network. The computer network may have a computing unit or be indirectly connected to the computing unit by means of a wide area network connection (WAN) or a (wireless) local area network connection (WLAN or LAN). For example, the computer program product can be stored digitally on a cloud server in a storage location of a computer network, transmitted to the computing unit via the internet by means of a WAN and/or by means of a WLAN or a LAN, in particular by invoking a download link to the storage location of the computer program product.

Features, advantages or alternative embodiments mentioned in the description of the device can equally be transferred to the method and vice versa. In other words, the claims directed to the method may be amended by means of the features of the device and vice versa. The device according to the invention can be used in particular in a method.

Drawings

The invention will be described and explained in more detail below with reference to embodiments shown in the drawings. In principle, structures and elements that remain substantially the same in the following description of the figures are designated with the same reference numerals as when the corresponding structure or element first appears.

The figures show:

fig. 1 shows a flow chart of a method for determining the validity of a reference frame between a reference structure and an anatomical structure during an interventional procedure on a patient of a first embodiment;

fig. 2 shows a method for determining validity of a second embodiment;

fig. 3 shows a flow chart of a method for determining validity of a third embodiment;

FIG. 4 illustrates a method for determining validity of a fourth embodiment;

fig. 5 shows a medical system of a fifth embodiment.

Detailed Description

Fig. 1 shows a flow chart of a first exemplary embodiment of a method for determining the validity of a reference system B between a reference structure R and an anatomical structure a during an interventional procedure on a patient P, having the following steps:

method step S100 shows that a first image data record B1 of the patient P is acquired at a first time by means of the X-ray device 13 during the interventional procedure, wherein the first image data record B1 has a reference structure R, an anatomical structure a and a reference system B between the reference structure R and the anatomical structure a.

Method step S101 indicates that a second image data record B2 of the patient P is acquired at a second point in time during the interventional procedure by means of the X-ray device 13, wherein the second image data record B2 has at least the reference structure R.

Method step S102 indicates that the second image data set B2 is registered to the first image data set B1, wherein the reference structure R depicted in the first image data set B1 and the reference structure R depicted in the second image data set B2 are input as input parameters into the registration, and wherein the registered second image data set B2' is determined as a result of the registration.

Method step S103 indicates that the validity of the reference system B is determined by means of a comparison of the registered second image data set B2' with the first image data set B1. The determination of the validity of the reference system B, in particular the method steps S101 to S103, can be carried out at least partially and/or completely by means of the computing unit 10 of the medical system 11. Determining validity may be performed semi-automatically and/or fully automatically. Determining the validity may include providing an output value based on the validity of the reference frame B, wherein the output value is descriptive of the validity.

A reference frame B between the reference structure R and the anatomical structure a typically describes the relationship between the reference structure R and the anatomical structure a. The reference frame B is particularly relevant for the positioning of the reference structure R relative to the anatomical structure a. The localization describes, inter alia, the location and/or orientation of the reference structure R and/or the anatomical structure a. The reference frame B is generally valid as long as the positioning of the reference structure R with respect to the anatomical structure a is rigidly and/or fixedly maintained. The reference frame B may become invalid when the positioning of the reference structure R relative to the anatomical structure a changes. In principle, it is conceivable for the change in position to be quantified by an offset value and for the validity to be specified in accordance with the offset value. The threshold value can, for example, be defined up to which the reference frame B remains valid despite the positioning change. The reference frame B may be changed, for example, by a force acting on the reference structure R and/or on the anatomical structure a. The force action may be based on, for example, gravity and/or contact with a user of the medical system 11. The reference frame B describes, among other things, the state of the anatomical structure a and the reference structure R. Based on the change of positioning, another reference frame B' may be specified.

The anatomical structure a comprises at least one anatomical landmark, in particular a bony structure and/or a cartilaginous structure, of the patient P. The at least one anatomical landmark may include a nose, an organ, a bone, a vertebra, a bony protrusion, and/or a vertebral protrusion of the patient P.

The reference structure R is typically an artificial structure. In other words, the reference structure R is not a natural component of the patient P. The reference structure R may have a solid and/or liquid material. The reference structure R is generally rigid. In other words, the reference structure R is in particular inelastic. The reference structure may be connected to and/or disconnected from the patient P, for example, before, during and/or after the interventional procedure.

The interventional procedure comprises in particular a surgical procedure, such as an invasive and/or minimally invasive procedure. During an interventional procedure, it is intended that the patient P is typically supported and/or anesthetized on the patient table 12 for the interventional procedure. Determining effectiveness generally describes a non-invasive approach. The interventional procedure may include, inter alia, angiography, cardiac surgery and/or surgery on the spine of the patient P.

Detecting the first image data set B1 generally includes: a first image data set B1 is provided for further processing, in particular for registration according to method step S102. Before the provision of the first image data set B1, the first image data set B1 is typically detected by means of the X-ray device 13. For this purpose, the X-ray device 13 can have an X-ray tube and an X-ray detector, wherein the X-ray detector is in particular designed to detect X-rays emitted by the X-ray tube. After the detection of the emitted X-rays, a first image data set B1 of the patient P can be reconstructed, for example, by means of the calculation unit 10. In principle, it is conceivable to transmit the first image data record B1 to a radiology information system and/or a PACS image archiving system before provision. Detecting the first image data group B1 may include: the first image data set B1 is called from the radiology information system and/or the PACS picture archiving system. The first image data record B1 may be present in particular in the DICOM image format. The first image data set B1 typically has at least one two-dimensional image. In principle, it is conceivable for the first image data record B1 to be a volumetric image data record. The volumetric image data set may have, for example, a two-dimensional image sequence and/or have been reconstructed from at least two-dimensional images which are not parallel to one another.

Since the examination of the first image data set B1 and the examination of the second image data set B2 are substantially identical, for the sake of overview, reference is made to the above description of the examination of the first image data set B1 in respect of the examination of the second image data set B2.

Typically, the first time is before the second time. In other words, method step S100 is usually performed before method step S101. The first time may be, for example, before an invasive intervention into the patient P, and the second time may be after the invasive intervention. In principle, however, the reverse order is also conceivable.

The first image data set B1 generally has a first measuring region and the second image data set typically has a second measuring region, wherein the first measuring region and the second measuring region preferably coincide. In other words, the same coordinates of the medical system 11 are covered by the first and second measurement areas. In principle, it is conceivable that the first measurement region and the second measurement region partially overlap, wherein in this case the intersection of the overlaps typically has the reference structure R.

By the first image data set B1 having the reference structure R, the anatomical structure a and a reference frame B between the reference structure R and the anatomical structure a, the reference frame B can be initially specified. In addition to the reference structure R, the second image data set B2 may have an anatomical structure a. In addition to the anatomical structure a and/or the reference structure R, the first image data set B1 and/or the second image data set B2 may have further structures. Having may mean that the anatomical structure a and/or the reference structure R are depicted in the first image data set B1 and/or the second image data set B2. In other words, the pixel values of the first image data set B1 and/or the second image data set B2 typically reflect the anatomical structure a and/or the reference structure R.

Inputting the reference structure R depicted in the first image data group B1 and the reference structure R depicted in the second image data group B2 as input parameters may include: the first image data set B1 and/or the second image data set B2 are weighted and/or segmented such that the reference structure R forms a starting point for the registration. In other words, the first image data set B1 and the second image data set B2 are preferably registered such that the reference structure R depicted in the first image data set B1 and the reference structure R depicted in the second image data set B2 are congruent. The weighting and/or segmentation may be performed, for example, in the calculation unit 10 by means of an image recognition algorithm. The result of the registration may comprise additional transformation rules which may be applied to the second image data set B2 such that a registered second image data set B2' is determined. Registration typically includes rigid registration. The rigid registration results in particular in translational and/or rotational transformation rules. The registration may detect segmentation and/or filtering of the first image data set B1 and/or the second image data set B2. For example, it is conceivable that additional translational and/or rotational transformation rules are determined by means of the segmented first image data set and/or the segmented second image data set and are applied to the second image data set B2. In principle, it is conceivable to register the first image data set B1 with the second image data set B2 instead of registering the second image data set B2 with the first image data set B1.

The comparison of the registered second image data set B2' with the first image data set B1 may be performed semi-automatically and/or fully automatically. In the latter case, this means that the validity of the reference frame B is determined without interaction with the user. The comparison may be made such that the first image data set B1 and the registered second image data set B2' are correlated on a pixel basis, wherein a change in pixel value may indicate: the reference frame B is no longer valid. Starting from the reference structure R, the comparison is carried out in particular as follows: only regions of pixels outside the reference structure R are compared with one another, since preferably the reference structure R depicted in the first image data set B1 and the reference structure R depicted in the registered second image data set B2' are superimposed on a pixel-by-pixel basis. In other words, the position of the anatomical structure a in the first image data set B1 is preferably compared with the position of the anatomical structure a in the second image data set B2. In principle, it is conceivable to compare only the anatomical structure a depicted in the first image data set B1 with the anatomical structure a depicted in the registered second image data set B2'. In general, the reference frame B is valid as long as the first image data set B1 and the second image data set B2 are congruent. In other words, in this case there is no change in the pixel values, which indicates a movement of the reference structure R between the first and second instants. The validity of the reference system B is described in particular: to what extent the positioning of the reference structure R with respect to the anatomical structure a changes between the first and the second instant.

Fig. 2 shows a method for determining validity of the second embodiment.

In fig. 2, a first image data record B1 and a second image data record B2 are shown one above the other and each have an anatomical structure a and a reference structure R.

Fig. 2 shows an exemplary embodiment in which a first image data record B1 of the patient P is detected at a first point in time by means of the X-ray device 13 and/or a second image data record B2 of the patient P is detected at a second point in time by means of the X-ray device 13 during the interventional procedure, and in which the reference structure R is connected to the vertebrae of the spine prior to the method for determining the validity. The anatomical structure a is in particular a vertebra of the spine of the patient P.

In the described embodiment, the reference frame B is unambiguously specified, since the reference structure R is rigidly and/or fixedly connected to the patient P, in particular to the spine.

The reference structure R has at least one image marking, a first fastening means and a holding structure, wherein the at least one image marking is releasably connected to the holding structure by means of the first fastening means. The first fixing means may be a ball receiving device for the at least one image marker. In this case, the at least one image marker may be replaced and/or cleaned, for example, before, during and/or after the interventional procedure. In principle, it is conceivable for the at least one image marking to be a fixed component of the holding structure and/or to be non-releasably connected.

The reference structure R has a second fixing mechanism and a holding structure, wherein the holding structure is connected to the patient by means of the second fixing mechanism, and wherein a reference system B between the reference structure R and the anatomical structure a is initially defined by means of the connection between the holding structure and the patient P. In this case, the reference structure R is connected invasively to the patient P, in particular to the anatomical structure a, in particular before the detection of the first image data set B1. The retaining structure may be constructed of plastic and/or metal. The second securing mechanism may include a clip, a bolt, and/or a pin. The second fixing means are basically designed such that the holding structure is fixedly and/or rigidly connected to the patient P, in particular during an interventional procedure. The fixed connection means in particular that the holding structure preferably cannot be released from the patient without tools. A rigid connection means in particular that the reference frame B between the reference structure R and the anatomical structure a is preferably not changed unless due to force effects.

The reference structure R has at least one image marker which in the described embodiment absorbs X-rays. Preferably, the reference structure R, in particular the at least one image marker, absorbs more X-rays than the anatomical structure a. The at least one image marking may be a hybrid marking which can be detected, for example, optically by means of a camera and/or by means of the X-ray device 13. The at least one image marking may be spherical, wherein the sphere is filled with a contrast agent and/or is made of metal, for example. It is particularly advantageous if at least one image marking has a plurality of balls, for example 4 to 6 balls, which are fixedly positioned relative to one another.

Registering the second image data set B2 to the first image data set B1 according to method step S102 includes: the reference structure R is determined by means of at least one image marker depicted in the first image data set B1 and at least one image marker depicted in the second image data set B2. In other words, the transformation rule derived therefrom is preferably determined such that the at least one image marker depicted in the first image data set B1 and the at least one image marker depicted in the registered second image data set B2 coincide.

As illustrated, for example, in fig. 2, the positioning of the reference structure R relative to the anatomical structure a is unchanged between the first image data set B1 and the second image data set B2. In this case, the reference system B is valid according to method step S103.

Fig. 3 shows a flowchart of a method for determining validity according to a third exemplary embodiment.

Method step S104 shows that the comparison comprises: a third image data set B3 is determined by means of the first image data set B1 and the registered second image data set B2'. A third image data set B3 is typically determined in the calculation unit 10. In other words, the third image data set B3 is calculated and is not detected by means of the imaging device, in particular the X-ray device 13. Determining the third image data set B3 may include segmenting and/or filtering the first image data set B1 and the registered second image data set B2'.

Method step S105 shows that determining the third image data set B3 includes weighting the first image data set B1 and the registered second image data set B2'. The weighting may include addition, subtraction, multiplication, and/or division. The weighting may be performed according to an image recognition algorithm applied to the first image data set B1 and/or the registered second image data set B2' in order to identify the reference structure R and/or the anatomical structure a. The image recognition algorithm may particularly recognize anatomical landmarks. An image recognition algorithm may be used for filtering and/or segmenting the first image data set B1, the second image data set B2, the registered second image data set B2' and/or the third image data set B3.

Method step S107 shows that determining validity comprises: the third image data set B3 is pixel-dependently classified into at least two classes according to the deviation from the reference frame B, whereby pixel-dependent classification values are determined and wherein the pixel-dependent classification values are visualized on the display unit 14 as an overlay with the first image data set B1, the registered second image data set B2' and/or the third image data set B3. The pixel-dependent classification may be performed on a pixel-by-pixel basis or for groups of pixels. Deviations from the reference frame B are described in particular: whether and/or to what extent the anatomical structure a has moved between the first image data set B1 and the registered second image data set B2'. Deviations from the reference frame B can be detected, for example, in pixel coordinates and/or millimeters. One of the two categories may, for example, include pixels having a deviation value less than or equal to a threshold value, while the other of the two categories may include pixels having a deviation value greater than the threshold value. The threshold value is preferably 5mm, advantageously 3mm and particularly preferably 1 mm. The threshold may be between 0.1mm and 5 mm. In the described embodiment, the pixel-dependent classification value specifies binary: whether a structure depicted in the pixel or in the group of pixels has moved by at most 5mm or more between the first and second instants. In other words, the pixel-dependent classification values represent regions with small deviations and regions with large deviations. Preferably, the user of the medical system 11 is able to identify by means of the superimposition: in which regions there are large deviations and in which regions there are small deviations.

Method step S106 shows that determining validity comprises: the third image data set B3 is visualized on the display unit 14. Determining the third image data group B3 may include: the first image data set B1 and the registered second image data set B2 'are displayed one above the other, wherein for example the first image data set B1 and/or the registered second image data set B2' are at least partially transparent. In this case, the user of the medical system 11 can, for example, determine the validity of the reference frame B.

Alternatively or in addition to method steps S106 and S107, determining the validity may comprise: invoking a threshold, segmenting the third image data set B3, calculating a segmentation related value in the segmented third image data set B3, and comparing the segmentation related value to the threshold. A segmentation of the third image data set B3 may be performed by means of an image recognition algorithm in order to identify the reference structure R and/or the anatomical structure a. The threshold value may be entered by a user of the medical system 11 and/or recalled from a database, for example. The segmentation-related values for example give the mean, median and/or value distribution of the segmented regions of the third image data set.

Method step S108 shows that, when the second image data set B2 has the reference structure R and the anatomical structure a, the anatomical structure a depicted in the second image data set B2 is registered with the anatomical structure a depicted in the first image data set B1 or in the fourth image data set in connection with the determination of the validity of the reference system B. In particular, the fourth image data record may be a volume image data record, which is typically detected prior to the interventional procedure, for example by means of the X-ray device 13 and/or a computer tomography scanner and/or a magnetic resonance tomography scanner.

When the reference system B is valid, the transformation rules between the patient coordinate system and the coordinate system of the medical system 11 are typically valid. Typically, when the reference frame B is invalid, the transformation rule is invalid. Without valid transformation rules, there is typically no feasibility except by re-registering the two coordinate systems: the patient coordinate system is associated with the coordinate system of the medical system 11. The re-registration is typically time consuming and/or computationally intensive. The patient coordinate system typically has a reference frame B. When the reference frame B becomes invalid, the patient coordinate system typically becomes invalid as well, and the other patient coordinate system is valid. The other patient coordinate system typically has another reference system B'. The further reference frame B' may be generated by: the reference frame B becomes invalid between the first image data set B1 and the second image data set B2.

Typically, the fourth image data set has a patient coordinate system and/or is registered with the patient coordinate system by means of at least one transformation rule. Preferably, at least one transformation rule can be extended and/or supplemented with another transformation rule, whereby in turn another patient coordinate system can be associated with the coordinate system of the medical system 11. The expanding may comprise multiplying at least one transformation rule with another transformation rule. Another transformation rule may generally be determined when registering the anatomical structure a depicted in the second image data set B2 with the anatomical structure a depicted in the first image data set B1 or in the fourth image data set.

Method step S109 indicates that, when the second image data set B2 has the reference structure R and the anatomical structure a, the measurement region of the fifth image data set is defined on the basis of the reference structure R and the anatomical structure a depicted in the second image data set B2. The fifth image data set preferably has the reference structure R and the anatomical structure a, in particular if the measurement region is specified in advance accordingly. The specification of the measurement range can be carried out, for example, on the display unit 14 by a user of the medical system 11 and/or automatically in the computing unit 10.

In principle, it is conceivable to carry out method steps S108 and S109 in a different order and not in parallel.

The method steps S104 to S109 can typically be carried out independently of one another, so that they are carried out either individually or in any combination.

Fig. 4 shows a method for determining validity in a fourth exemplary embodiment in an illustrative flow chart.

Fig. 4 shows a situation which is in particular the reverse of fig. 2, in which the reference system B is not valid according to method step S103. In the described embodiment, a further reference frame B' is defined as a result of the change in the position of the reference structure R relative to the anatomical structure a in the second image data set B2.

Furthermore, fig. 4 shows the registered second image data set B2' and third image data set B3. The registered second image data set B2 'indicates that the reference structure R depicted in the first image data set B1 and the reference structure R depicted in the second image data set B2 are input as input parameters into the registration, since the registered second image data set B2' is oriented according to the reference structure R. Preferably, the reference structure R is thus depicted at the same position in the first image data set B1 and in the registered second image data set B2'.

The third image data set B3 schematically shows, in particular, method step S104. Determining the third image data group B3 may include: the fusion and/or the superimposition of the first image data set B1 and the registered second image data set B2'. The third image data set B3 shows, in particular, that the reference structure R depicted in the first image data set B1 and the reference structure R depicted in the registered second image data set B2' are exactly superimposed on top of one another. The anatomy a of the registered second image data set B2' is shown in dashed lines in the third image data set B3.

A further reference frame B 'and a reference frame B are shown in the third image data set B3, wherein at or after the second time instant the further reference frame B' is valid and the reference frame B is invalid.

Fig. 5 shows a medical system 11. The medical system 11 has an X-ray device 13 and a computing unit 10. The X-ray device 13 has a C-arm 15, an X-ray detector and an X-ray radiator. In addition to the medical system 11, the patient P is supported on a patient table 12 in a prone position in fig. 5, so that, for example, a surgical operation can be performed at the spine of the patient P. Furthermore, a reference structure R is shown relative to the patient P. Based on the positioning of the reference structure R, forces may act on the reference structure R, whereby the reference frame B may become invalid. The force action may be performed, for example, by the user, by gravity and/or by rotation of the patient P.

In the embodiment, the medical system 11 has a display unit 14. The display unit 14 has a monitor and may have an input mechanism. The display of the third image data set B3 is schematically shown on the display unit 14 when the reference frame B is active.

Although the details of the invention have been illustrated and described in more detail with reference to preferred embodiments, the invention is not limited to the examples disclosed and other variants can be derived therefrom by those skilled in the art without departing from the scope of the invention.