NL2036201B1

NL2036201B1 - A gamma radiation imaging system, collimator assembly, and method

Info

Publication number: NL2036201B1
Application number: NL2036201A
Authority: NL
Inventors: Johannes Beekman Frederik
Original assignee: Stichting The Molecular Imaging
Priority date: 2023-11-07
Filing date: 2023-11-07
Publication date: 2025-05-19

Abstract

-32- A B S T R A C T A gamma radiation imaging system, for example for scintimammography, comprises a gamma camera with a collimator assembly having a slit section at the object side and a slat section at the detector side facing the detector. The slat section comprises multiple spaced elongated slats extending in a first direction. The slit section comprises multiple slit structures each extending in a second direction, and each have one slit or multiple slits in close proximity. The slit structures have a respective slit structure field of view with an acceptance angle and are arranged spaced apart from one another in the first direction. The collimator assembly is configured to move at least the slit section and/or the slit structures thereof so as to scan each of the slit structure fields of view through a portion of the imaging space substantially in the first direction and to image each of the scanned slit structure fields of view onto a respective projection area of the detector.

Description

P36521NLO0

A GAMMA RADIATION IMAGING SYSTEM, COLLIMATOR ASSEMBLY, AND METHOD

The present invention relates to a gamma radiation imaging system.

In embodiments, the system is configured for scintimammography or for imaging another human body part, e.g. an extremity like an arm or a leg, or for imaging an animal body part.

As discussed herein, other fields of use are also envisaged, e.g. industrial applications, etc.

For example, scintimammography is to be performed as complementary to regular X-ray based mammography, e.g. in case of dense breast tissue.

Known systems for scintimammography are described, for example, in WO2010008538,

WO02010/014001, WO2010120636, US2013/0158389, and US105159456.

In US9711251 breast imaging is discussed, wherein use is made of a so-called VASH collimator, wherein VASH stands for variable angle slant hole. This collimator includes a stack of collimator leaves, like a deck of cards, each leaf being provided with a 2D-array of apertures in an identical pattern. For example, the apertures are square. The leaves are capable of alignment in an initial position wherein the apertures in the leaves are axially aligned with one another and at 90° with respect to the plane of the collimator. Also, there is a controlled mechanism for positioning each of the leaves in the stack in a controlled manner such that each leaf slides at a predetermined rate with respect to the surrounding leaves in the stack. This allows to vary the inclination of the holes formed by the apertures in the leaves. A known drawback of this collimator is that, in particular at a significant inclination, the shape of the hole becomes irregular, e.g. jagged. This, for example, leads to issues with penetration and resulting impairment of the imaging process.

The present invention aims to provide an improved gamma radiation imaging system and/or collimator assembly, for example an improved scintimammography system.

The present invention aims to provide a system which has an increased angular sampling resolution and sensitivity of the object (e.g. the person or animal) in view of the imaging.

The present invention also or alternatively aims to reduce the time required for the imaging, e.g. enhancing throughput and/or enhancing comfort for the person.

The present invention also or alternatively aims to provide increased accuracy of the localization of the tumorous lesion.

The present invention provides a gamma radiation imaging system, for example for scintimammography, according to claim 1.

The gamma radiation imaging system, for example for scintimammography, comprises: - a gamma camera configured and arranged to detect gamma radiation emitted from an object received in an imaging space, e.g. a human body part, e.g. a female breast, wherein the gamma camera comprises: - a collimator assembly which extends in a plane and has an object side facing the imaging space and a detector side, - a gamma sensitive detector arranged at the detector side of the collimator assembly to receive gamma radiation passing through the collimator assembly on an incident side of the detector, wherein the collimator assembly comprises: - a slit section at the object side, - a slat section at the detector side, wherein the slat section comprises multiple spaced elongated slats having a length in a first direction of the collimator assembly, a spacing between neighboring slats in a second direction of the collimator assembly, and a height in a third direction of the collimator assembly perpendicular to the plane of the collimator assembly, wherein the slit section is adjacent the slat section, which slit section comprises multiple slit structures each extending in the second direction, preferably at least three slit structures, which slit structures each have one slit or multiple slits in close proximity, each slit structure having a respective slit structure field of view with an acceptance angle, which slit structures are arranged in the slit section spaced apart from one another in the first direction, wherein the collimator assembly is configured to move at least the slit section and/or the slit structures thereof so as to scan each of the slit structure fields of view through a portion of the imaging space substantially in the first direction and to image each of the scanned slit structure fields of view onto a respective projection area of the detector.

As will be explained herein, the inventive concept provides for scanning of each of the slit structure fields of view through a portion of the imaging space substantially in the first direction by various embodiments of the collimator assembly that allow for motion of at least the slit section and/or the slit structures thereof. This, for example, allows for enhanced resolution and/or sensitivity of the gamma camera, which may benefit the imaging process, e.g. in terms of the time required for the imaging, e.g. enhancing comfort for the person, and/or increased accuracy of the localization of the tumorous lesion.

The slat section can be readily assembled in different configurations, e.g. in view of optimization of the imaging a certain object, e.g. a female breast, e.g. desiring to enhance view where the breast adjoins the torso.

For example, the multiple spaced elongated slats are at a fixed perpendicular orientation relative to the plane of the collimator assembly.

For example, the multiple spaced elongated slats are slanted at a fixed orientation relative to the plane of the collimator assembly, e.g. all at the same inclination.

For example, the multiple spaced elongated slats are slanted in a fixed converging arrangement relative to the plane of the collimator assembly.

For example, the multiple spaced elongated slats are parallel to one another at least at the object side of the collimator assembly. This may, for example, allow for a converging arrangement of the slats. In another embodiment all slats are perfectly parallel to one another.

For example, one or more, e.g. all, of the multiple spaced elongated slats are configured to vary the inclination thereof by a slat inclination mechanism, e.g. over an inclination range including a perpendicular orientation relative to the plane of the collimator assembly. For example, the slat inclination mechanism is configured to provide a perpendicular orientation of all slats relative to the plane of the collimator assembly, or of a majority of the slats, and an inclined orientation of multiple slats, e.g. all slats or of a majority of the slats, e.g. a converging and/or diverging arrangement of multiple slats.

For example, multiple spaced elongated slats and the associated slat inclination mechanism are configured to vary the inclination of the slats, e.g. to allow for multiple of the following slat orientations:

- the slats being perpendicular to the plane of the collimator assembly, - the slats having the same inclination in the same direction, - the slats having a converging arrangement, - the slats having a diverging arrangement, -the slats have a symmetrical inclination relative to a central normal plane of the slat section of the collimator assembly, e.g. a converging symmetrical or asymmetrical inclination, - the slats having an asymmetrical inclination relative to a central normal plane of the slat section of the collimator assembly, e.g. a diverging symmetrical or asymmetrical inclination, - etc.

For example, the system is configured such that a first imaging step is done with a perpendicular orientation relative to the plane of the collimator assembly of all slats, or of a majority of the slats, in order to determine the presence and location of a region of interest in the object. Based on the determination made in the first imaging step, e.g. based on an analysis of the image by a medical doctor and/or an automated image processing, a second imaging step may then be performed for which the slat inclination mechanism changes the inclination of multiple slats, e.g. all slats or of a majority of the slats, e.g. a converging arrangement of multiple slats focused towards the region of interest determined in the first step.

In embodiments, the slat section is configured such that the spacing between multiple slats, e.g. a majority or all of the slats, is adjustable, e.g. by a corresponding slat spacing adjustment mechanism. This allows to vary the sensitivity of the slat section.

In embodiments, both a slat spacing adjustment mechanism and a slat inclination mechanism is provided, allowing for variation of both the spacing and in the inclination of the slats, e.g. controlled by a computerized controller, e.g. both variations being done simultaneously or one after the other.

In embodiments, the slat section as a whole is stationary relative to the detector, wherein the collimator assembly is configured to move the entire slit section relative to stationary slat section.

In embodiments, the collimator assembly is configured to move both the slat section and the slit section relative to the detector.

As will be discussed in more detail below, in embodiments, only the slit structures of the slit section are moved, e.g. each being rotatable and being rotated about a corresponding axis extending in the second direction.

In an embodiment, the slit section is a slit plate member provided with the multiple slit structures each extending in the second direction, wherein the collimator assembly is configured to scan the slit structure fields of view through respective portions of the imaging space substantially in the first direction by moving the slit plate member in the first direction.

For example, the slit structures are spaced apart from one another in the first direction at a regular spacing distance, and the gamma camera is configured to move the slit plate member in the first direction over a scanning distance which corresponds to the regular spacing distance or a greater distance, e.g. less than twice the regular spacing distance.

For example, the slit structures each define in the slit plate member a single slit or as multiple, e.g. two, slits in close proximity, wherein inclined edges within the slit plate member provide the acceptance angle with the respective slit field of view for the slit structure.

For example, the acceptance angle of each slit structure is between 20° and 70°.

For example, the acceptance angle is symmetrical relative to a normal plane perpendicular to the object side of the slit section, or the acceptance angle is asymmetrical relative to a normal plane perpendicular to the object side of the slit section, e.g. wherein slit structure fields of view are converging relative to one another.

In a practical embodiment, the slit width is fixed and lies between 1 and 3 millimeters.

In embodiments, the slit section is configured such that the slit width of one or more slits, e.g. all slits, is adjustable.

In embodiments, the slit section is configured such that one or more of the slits can selectively be closed, e.g. by provision of a corresponding shutter or by reducing the width in an adjustable slit width embodiment to zero.

In practical embodiments, the object side and the detector side of the collimator assembly are generally planar and parallel to one another. Also, in practical embodiments, the incident side of the detector is planar.

-B-

In an embodiment, according to claim 7, the slit section is a slit plate member provided with the multiple slit structures extending in the second direction, wherein each slit structure comprises an elongated rotatable slit member extending in the second direction and rotatably received in a corresponding elongated passage in the slit plate member to be rotatable about arotation axis, wherein the rotatable slit member is provided with one slit or multiple slits in close proximity through the rotatable slit member, preferably one slit, wherein a rotation drive is provided for rotating the rotatable slit members over a rotation angle about the rotation axis, wherein the collimator assembly is configured to scan the slit fields of view through respective portions of the imaging space substantially in the first direction by rotating the rotatable slit members.

In practical embodiments, an elongated rotatable slit member may have a length between 5 and 35 centimeters, e.g. extending across the majority of or the entire effective dimension of the collimator assembly in the second direction.

For example, each rotatable slit member has a rod-shaped main body with circular cross- section which is rotatable about an axis extending through the center of the rod-shaped main body. For example, adjoining faces of the slit plate member are semi-circular to receive the rod-shaped main body in rotatable manner.

For example, each rotatable slit member is provided with a single slit or multiple, e.g. two, slits in close proximity, wherein inclined edges in the rotatable slit member provide the acceptance angle with the respective slit structure field of view.

For example, the acceptance angle of a rotatable slit member is between 10° and 50°.

For example, the slit structure fields of view each have a center plane, wherein the slit section is configured such that the center planes of multiple or all of the slit structure field of views are parallel to one another.

For example, the slit structure fields of view each have a center plane, wherein the slit section is configured such that the center planes of multiple or all of the slit structure field of views are converging.

In an embodiment, the collimator assembly is configured and to be operated such that in a first imaging step all slit structures perform the same rotation with all center planes of the fields of view being parallel to one another. Once this scanning has resulted in the localization of a region of interest, in a second imaging step, the slit structures are rotated so as to have a focus towards the region of interest, e.g. a converging arrangement of the center planes of at least some of the slit structures, where the scanning may then comprise performing a limited rotation of the rotatable slit structures.

For example, the rotation drive is configured to rotate all of the slit structures simultaneously and, preferably, in identical manner.

For example, the rotation drive is configured to rotate all of the slit structures independently, e.g. including multiple independently controllable drives.

For example, the collimator assembly is configured to scan the slit fields of view through respective portions of the imaging space substantially in the first direction by both moving the slit plate member in the first direction and rotating the rotatable slit members.

For example, the collimator assembly is configured to scan the slit fields of view through respective portions of the imaging space substantially in the first direction by stepwise moving the slit plate member in the first direction and rotating the rotatable slit members in between step motions of the slit plate member. In embodiments, steps in the stepwise linear motion in the first direction have some overlap in time with steps of rotation of the rotatable slit members.

In embodiments, a controller, e.g. computerized, controls linear motion of the slit section and/or rotary motion of the rotatable slit structures, e.g. the two motions in a coordinated manner.

In embodiments, each slit has a width of between 1 and 3 millimeter.

For example, the spacing distance, e.g. the regular spacing distance, between neighboring slit structures, is at least 20 millimeters, e.g. when slits are formed in the slit plate.

For example, the spacing distance, e.g. the regular spacing distance, between neighboring rotatable slit members is at least 15 millimeters.

Preferably, the collimator assembly is configured such that, with the collimator assembly considered stationary, the projection areas of the slit structures field of view are non- overlapping.

In an embodiment, the system comprises multiple gamma cameras, e.g. two gamma cameras on opposite sides of the imaging space.

Itis noted that the invention also relates to a system just having one gamma camera, noting that this is impractical for scintimammography where two opposing cameras are common and preferred.

In other embodiments, three or more gamma cameras are provided to image an object in the imaging space, e.g. three in a triangular arrangement about the imaging space.

As preferred, the one or more gamma cameras are at stationary location(s) relative to the imaging space, and preferably relative to the object held therein, during imaging of the object. During imaging, motion of the slit section, slit structures, the slats in the slat section, and/or the entire collimator assembly takes place in one or more manners as discussed herein.

As will be appreciated, with the gamma camera at a stationary location, the scanning motion(s) as discussed herein are performed due to appropriate operation of the collimator assembly.

In an embodiment, the system further comprises an immobilization assembly to immobilize the object.

For example, the immobilization assembly comprises: - a frame supporting a first immobilization plate and a second immobilization plate, which second immobilization plate is arranged or arrangeable to extend parallel to the first immobilization plate, wherein the first and second immobilization plates define the imaging space between them and are configured to clamp the object to be imaged, e.g. a human body part, e.g. a female breast, between the immobilization plates, wherein the gamma camera is positioned with the collimator assembly thereof adjacent the first immobilization plate.

For example, the system comprises a second gamma camera positioned with the collimator assembly thereof adjacent the second immobilization plate.

In an embodiment, at least one of the first and second immobilization plates is provided with a grid of tool apertures each configured to allow for passage of a tool through the first immobilization plate, e.g. a biopsy tool.

In an embodiment, the system is configured for scintimammography, wherein a female breast is to be received in the imaging space.

Preferably, the slit structures extend in the axial direction of the female breast from torso to nipple and the first direction or displacement direction is in a plane parallel to a coronal plane of the female breast.

In an embodiment, e.g. for scintimammography, the collimator assembly with non-rotatable slit structures has between 3 and 6 slit structures.

In an embodiment, e.g. for scintimammography, the collimator assembly with rotatable slit structures has between 5 and 10 slit structures, so possibly closer spaced to one another than in the version with fixed slit structures.

In another embodiment, the invention provides a gamma radiation imaging system, for example for scintimammography, comprising: - a gamma camera configured and arranged to detect gamma radiation emitted from an object received in an imaging space, e.g. a human body part, e.g. a female breast, wherein the gamma camera comprises: - a collimator, which extends in a plane and has an object side facing the imaging space and a detector side, - a gamma sensitive detector arranged at the detector side of the collimator to receive gamma radiation passing through the collimator assembly, wherein the collimator comprises multiple converging fan beam collimator portions arranged in series in a first direction of the collimator, each converging fan beam collimator portion having a fan beam field of view defined by holes forming an array of openings in the object side extending in the first direction and in a second direction perpendicular to the first direction and forming an array of openings in the detector side, wherein the arrays of openings in the object side are spaced from one another in the first direction over a spacing distance,

wherein the gamma camera is configured to move the collimator in the first direction so as to scan each of the fan beam fields of view through a portion of the imaging space substantially in the first direction and to image each of the scanned fan beam fields of view onto a respective projection area of the detector.

The present invention also relates to a gamma camera collimator assembly as described herein.

The present invention also relates to a gamma camera collimator assembly, e.g. for use in scintimammagraphy, which collimator assembly comprises: - a slit section at an object side, - a slat section at a detector side, wherein the slat section comprises multiple spaced elongated slats having a length in a first direction of the collimator assembly, a spacing between the neighboring slats in a second direction of the collimator assembly, and a height in a third direction of the collimator assembly perpendicular to the plane of the collimator assembly, wherein the slit section comprises a slit plate member provided with multiple slit structures extending in the second direction, wherein each slit structure comprises an elongated rotatable slit member extending in the second direction and rotatably received in a corresponding elongated passage in the slit plate member to be rotatable about a rotation axis, wherein each rotatable slit member is provided with one slit or multiple slits in close proximity through the rotatable slit member, preferably one slit, wherein a rotation drive is provided for rotating the rotatable slit members over a rotation angle about the rotation axis, wherein the collimator assembly is configured to scan the slit fields of view through respective portions of the imaging space substantially in the first direction by rotating the rotatable slit members.

The present invention also relates to a gamma camera collimator assembly, e.g. for use in scintimammography, which collimator assembly comprises: - a slit section at an object side, - a slat section at a detector side,

wherein the slat section comprises multiple spaced elongated slats having a length in a first direction of the collimator assembly, a spacing between the neighboring slats in a second direction of the collimator assembly, and a height in a third direction of the collimator assembly perpendicular to the plane of the collimator assembly, wherein the slit section comprises one or more slits extending in the second direction, wherein multiple slats are configured to have a variable inclination, and wherein the gamma camera is provided with a slat inclination mechanism configured to vary the inclination of one or more, e.g. all, of the multiple spaced elongated slats, e.g. over an inclination range including a perpendicular orientation relative to the plane of the collimator assembly.

The gamma camera collimator assembly with the slat inclination mechanism can be part of a gamma camera which is part of a gamma radiation imaging system for imaging of an object, for example for scintimammography, wherein the gamma camera is configured and arranged to detect gamma radiation emitted from an object received in the imaging space, e.g. a human body part, e.g. a female breast.

For example, the slat inclination mechanism is configured to provide a perpendicular orientation of all slats relative to the plane of the collimator assembly, or of a majority of the slats, and an inclined orientation of multiple slats, e.g. all slats or of a majority of the slats, e.g. a converging and/or diverging arrangement of multiple slats.

For example, multiple spaced elongated slats and the associated slat inclination mechanism are configured to vary the inclination of the slats, e.g. to allow for multiple of the following slat orientations: - the slats being perpendicular to the plane of the collimator assembly, - the slats having the same inclination in the same direction, - the slats having a converging arrangement, - the slats having a diverging arrangement, - the slats have a symmetrical inclination relative to a central normal plane of the slat section of the collimator assembly, e.g. a converging symmetrical or asymmetrical inclination, - the slats having an asymmetrical inclination relative to a central normal plane of the slat section of the collimator assembly, e.g. a diverging symmetrical or asymmetrical inclination, - etc.

For example, the slit section comprises multiple slit structures each extending in the second direction, preferably at least three slit structures, which slit structures each have one slit or multiple slits in close proximity, each slit structure having a respective slit structure field of view with an acceptance angle, which slit structures are arranged in the slit section spaced apart from one another in the first direction.

For example, the collimator assembly is configured to move at least the slit section and/or the slit structures thereof so as to scan each of the slit structure fields of view through a portion of the imaging space substantially in the first direction and to image each of the scanned slit structure fields of view onto a respective projection area of the detector.

For example, the gamma camera is part of a system which is configured such that a first imaging step is done with a perpendicular orientation relative to the plane of the collimator assembly of all slats, or of a majority of the slats, in order to determine the presence and location of a region of interest in the object. Based on the determination made in the first imaging step, e.g. based on an analysis of the image by a medical doctor and/or an automated image processing, a second imaging step may then be performed for which the slat inclination mechanism changes the inclination of multiple slats, e.g. all slats or of a majority of the slats, e.g. a converging arrangement of multiple slats focused towards the region of interest determined in the first step.

The present invention also relates to a method of gamma imaging an object, e.g. of a human body part, e.g. of a female breast, wherein use is made of the system and/or collimator assembly as described herein.

The invention will now be explained with reference to the drawings. In the drawings: - fig. 1 shows schematically an embodiment of a system according to the invention during an imaging step, - figs. 2, 3, and 4a schematically illustrate an embodiment of a collimator assembly according to the invention, - fig. 4b shows a variant wherein a slit structure is composed of two slits in close proximity, - figs. 5a, 5b, 6 schematically illustrate another embodiment of a collimator assembly according to the invention, - figs. 7, 8 schematically illustrate yet another embodiment of a collimator assembly according to the invention, -figs. 9a - f schematically illustrate different slat configurations for one or mare embodiments of a collimator assembly according to the invention

With reference to the figures examples of the collimator assembly will be discussed, here in the context (as preferred) of gamma radiation imaging for scintimammography and possibly an immediate follow up by a biopsy.

The system comprises a frame 1, only shown highly schematically, supporting a first immobilization plate 10 and a second immobilization plate 110 which here extends parallel to the first immobilization plate 10. The plates 10, 110 define an imaging space 200 between them for one breast 250 (shown schematic) of a female human person, e.g. standing or sitting.

The system is configured to clamp the breast to be imaged between the plates 10, 110.

In a practical embodiment, the plates 10, 110 are made of plastic material, e.g. one or both plates of a visually transparent plastic material.

The first immobilization plate 10 is provided with a 2D-grid of tool apertures, which are each configured to allow for passage of a tool through the first immobilization plate 10. In practical embodiments, the plate 10 has a multitude of apertures, closely spaced from one another. In practical embodiments, e.g. in view of the tool(s) that is to be passed through an aperture,

the diameter of each aperture may be several millimeters, e.g. between 3 and 8 millimeters, e.g. about 5 — 6 millimeters.

The system further comprises a first gamma camera 50 which is configured and arranged to detect gamma radiation emitted from the breast 250 in the imaging space passing through the first immobilization plate 10.

The system further comprises a second gamma camera 150 which is configured and arranged to detect gamma radiation emitted from the breast 250 in the imaging space passing through the second immobilization plate 110.

During imaging, the two gamma cameras 50, 150 are “as a whole” stationary relative to the imaging space and the object, here the breast 250 clamped between the plates 10, 110. As will be explained herein, the collimator assembly 160, possibly also part 65, is configured to perform a scanning motion during imaging.

The first gamma camera 50 comprises: - a first collimator assembly 60, which extends in a plane parallel to the first immobilization plate 10, - afirst gamma sensitive detector 80 arranged to receive gamma radiation passing through the first collimator assembly 60.

The second gamma camera 150 comprises: - a second collimator assembly 160, which extends in a plane parallel to the second immobilization plate 110, - a second gamma sensitive detector 180 arranged to receive gamma radiation passing through the second collimator assembly 160.

It is noted that in the figures the detectors 80, 180 are shown to be quite far away from the associated collimator assembly. This is done for clarity of the figures, in practical embodiments the detectors 80, 180 are in close proximity to the associated collimator assembly.

The first and the second collimator assemblies 60, 160 are each movable in the plane of the corresponding plate 10, 110 in a displacement direction Y, also called first direction, relative to the respective immobilization plate.

The collimator assembly 60 is guided by guide rails 5, 6 of the frame of the system.

Each collimator assembly 60, 160 is linearly driven in Y-direction by a corresponding collimator motion device 95, 195 which configured to controllably move the collimator assembly in the displacement direction Y.

The X-direction extends in the plane of the plates 10, 110, perpendicular to the Y-direction.

The X-direction corresponds to the axial direction of the breast 250 from torso to nipple.

As shown, the first collimator assembly 60 is slidable along the first immobilization plate 10 in the Y direction, perpendicular to the X-direction.

The first collimator assembly has a collimator part 65 which is provided with collimator openings through which gamma radiation passes from the imaging space to the detector 80.

The first collimator assembly has a non-collimating support part 75 adjoining the collimator part 65.

The second collimator assembly 160 is shown, by way of example, in more detail in figures 2, 3, and 4. This embodiment will now be discussed in more detail below. It is noted that the collimator part 65 may, preferably is, of a same design as the collimator assembly 160.

The collimator assembly 160 comprises: -aslit section 170 at the object side, - a slat section 165 at the detector side.

The slat section 165 comprises multiple spaced elongated slats 166 each having a length in a first direction, here displacement direction Y, of the collimator assembly, a spacing between the neighboring slats 166 in the second direction X of the collimator assembly, and a height in a third direction Z of the collimator assembly perpendicular to the plane of the collimator assembly.

For example, the slats 166 have a fixed configuration, e.g. spaced equidistant from one another and/or perpendicular to the plane of the collimator assembly.

For example, the slats 166 each have a thickness between their planar and parallel main faces of between 0.1 and 1 millimeters.

For example, the slats 166 have a spacing between 1 and 3 millimeters.

For example, the slats 166 have a height of between 1 and 10 centimeters.

The slit section 170 is arranged adjacent the slat section 165.

The slit section is a slit plate member 171 provided with the multiple slit structures, here five slit structures 172, each extending in the second direction X.

The collimator assembly 160 is configured to scan the slit structure fields of view through respective portions of the imaging space 200 substantially in the first direction Y by moving the slit plate member 171 in the first direction. In embodiments, the slat section 165 moves along with the slit plate member 171. In another embodiment, the slat section 165 is stationary relative to the detector 180.

In the depicted embodiment, each of the slit structures 172 has one slit 174 having a respective slit structure field of view with an acceptance angle. As can be seen, inclined edges, here knife edges, of the slit plate member provide the acceptance angle a with the respective slit field of view for the slit structure 172.

In general, the slits 174 may have a constricted profile in cross-section, such as a knife-edge profile, defining an acceptance angle of the field of view. Although the cross-section of a slit is not particularly limited, having a constricted profile, such as preferably a knife-edge profile, offers the advantage that the field of view is well-defined. However, other possibilities for the profile, such as a double horn-shape with rounded edges, are not excluded.

In the depicted embodiment, the fields of view of the slit structures are identical with regard to their acceptance angle and with regard to their orientation relative to the plane of the collimator 160. Also, the acceptance angle of each slit structure is symmetrical relative to a central normal plane through the slit structure. This, however, may also be different.

For example, in an embodiment, multiple slit structures 172 are embodied to have a converging configuration, which may be symmetrical relative to a central normal plane of the slit section by could also be asymmetric.

In another embodiment, each slit structure 172 is has multiple, e.g. two or three, slits in close proximity. Figure 4b shows an embodiment, wherein a slit structure 172 is composed of two slits 174a, b in close proximity which together define the acceptance angle a. In another embodiment, a third slit is arranged in the center plane, between the two slits 174a,b. This, for example, allows for each slit 174a, b to have a small acceptance angle with the totality of the slits defining the acceptance angle a of the slit structure field of view.

The slit structures 172 are arranged in the slit section 170 spaced apart from one another in the first direction, here over a regular spacing distance d.

For example, the gamma camera 150, here the drive 195, is configured to move the slit plate member 170 (possibly along with the slat section 165), in the first direction Y over a scanning distance which corresponds to the regular spacing distance “d” or over a greater distance, e.g. less than twice the distance “d” in practical embodiments.

The movement has the effect of scanning each of the slit structure fields of view through a portion of the imaging space 200 substantially in the first direction Y and to image each of the scanned slit structure fields of view onto a respective projection area 181 of the detector 180.

The non-collimating support part 75, e.g. made of plastic, comprises one or more tool openings, e.g. a slotted opening 90 in the second direction X, and/or grid of openings formed by support ribs of the part 75, e.g. a grate of ribs. The ribs may define openings which are open at the face of the first immobilization plate 10 as well as opposite thereof.

The openings of the non-collimating support part 75 are greater than each of the tool apertures in the first immobilization plate 10.

The first collimator assembly 60 is slidable selectively between a position wherein the collimator part 65 is in operative position for imaging of the breast with the first gamma camera 50 and a position, wherein the non-collimating support part 75 is in the operative position thereof for use in passing a tool, e.g. a biopsy tool, through an aligned opening, e.g. slotted opening 90, and a tool aperture in the plate 10.

In use, the breast 250 is clamped between the plates 10, 110, e.g. by moving the plate 10 along with the assembly 60, the detector 80, and rest of camera 50 towards the other plate 110.

Due to the provision of the non-collimating support part 75 adjoining the collimator part, it is possible to embody the immobilization plate 10 rather thin.

In practical embodiments, the immobilization plate 10, e.g. the plastic plate 10, has a thickness of less than 5 millimeters, more preferably between 1 and 3 millimeters, e.g. 2-3 millimeters.

A thin immobilization plate 10 would, by itself, bend under the loading during clamping of the body part, here breast 250, e.g. when the collimating part would be removed in order to perform an activity involving the tool that is to be passed through a selected tool aperture 15 in the immobilization plate 10. Due to the structure of the collimator assembly 60, this bending is countered by the non-collimating support part 75 which provides the desired structural support for the rather thin plate 10. This support is provided throughout the step of sliding the assembly such that the collimator part 85 is slid away from the operative position and the support part 75 in slid into the operative position.

Due to the opening(s) 90, here slot(s), a tool has access to a selected aperture in the plate 10, e.g. to penetrate a biopsy tool into a breast 250 of a female person.

In practical embodiments, one or more friction reducing features may be present in the system to reduce friction between the plate 10 and the assembly 60 during sliding. For example, a Teflon coating is provided, pressurized air or another lubricant is used between the plate 10 and the assembly 60, etc.

When it is determined that a biopsy of the region of interest is desired, the breast 250 remains immobilized by the plates 10, 110.

Part of the first gamma camera 50, at least including the detector 80 in practice also including a housing between the detector 80 and the collimator assembly 60, is repositioned away from the operative position thereof to provide space for the tool and access to the apertures 15. The tool is then passed through an opening in the part 75 and an aperture 15 so as to penetrate into the breast 250, make a mark on the breast, etc.

Repositioning of the first gamma camera 50, at least the detector 80, in order to provide access for the tool is done here by camera drive 85.

In an embodiment, not shown, the system further comprises a tool orientation device configured to be releasably mated with the non-collimating support part 75 and to interact with the tool that is to be passed through a tool aperture so as to provide for correct orientation of the tool. The orientation provided by the tool orientation device may comprise one or more of the position of the tool in the plane of the immobilization plate, the angle of the tool relative to the immobilization plate (e.g. the tool orientation device being configured to keep the tool perpendicular to the immobilization plate or at a specific angle). For example, the tool orientation device is configured to be mated with one or more ribs of the non- collimating support part 75. For example, the tool orientation device has a mating portion that fits into one or more openings of the part to mate the device with the part.

During taking of a biopsy with tool, the second gamma camera 150 can, if desired, be operational, e.g. to monitor penetration of the tool into the part 250.

With reference to figures 5a, b and 6 an alternative embodiment of collimator assembly, now denoted as 260, will be discussed. As will be appreciated, the part 65 of the collimator assembly 60 can be of the same design.

The collimator assembly 260 comprises: - a slit section 265 at the object side, - a slat section 270 at the detector side.

The slat section 265 comprises multiple spaced elongated slats 266 each having a length in a first direction, here displacement direction Y, of the collimator assembly, a spacing between the neighboring slats 266 in the second direction X of the collimator assembly, and a height in a third direction Z of the collimator assembly perpendicular to the plane of the collimator assembly.

The slit section 270 is arranged adjacent the slat section 265.

The slit section is a slit plate member 271 provided with the multiple slit structures, here five slit structures 272, each extending in the second direction X.

Each slit structure comprises an elongated rotatable slit member 273 extending in the second direction and rotatably received in a corresponding elongated passage in the slit plate member 271 to be rotatable about a rotation axis R.

Each rotatable slit member 273 is provided with one slit 274 through the rotatable slit member in this example.

In an alternative embodiment, each slit member 273 is provided with multiple, e.g. two or three, slits in close proximity through the rotatable slit member.

A rotation drive 275 is provided for rotating each of the rotatable slit members 273 over a rotation angle about the rotation axis R.

Generally, the collimator assembly 260 is configured to scan the slit fields of view through respective portions of the imaging space 200 substantially in the first direction by rotating the rotatable slit members 273.

In this example, each rotatable slit member 273 is provided with a single slit 274, wherein inclined edges in the rotatable slit member, here forming a knife edge, provide the acceptance angle a with the respective slit structure field of view.

For example, in the case of the rotatable slit members 273, the acceptance angle a is between 10° and 50°. This may be smaller than the angle for the embodiment of figures 2, 3, and4.

In the example shown here, the slit structure fields of view each have a center plane and the slit section is configured such that the center planes of all of the slit structure field of views are parallel to one another. In another embodiment, the center planes of multiple or all of the slit structure field of views are converging.

In an embodiment, the rotation drive 275 is configured to rotate each of the rotatable slit members over less than a full revolution, e.g. over a swivel angle so that the members can perform a swivel motion.

In an embodiment, the rotation drive 275 is configured to rotate all of the rotatable slit members 273 simultaneously and, possibly, in identical manner.

In another embodiment, the rotation drive 275 is configured to rotate all of the slit structures independently. This may allow for various orientations of the center planes relative to one another. The relative orientation may, possibly, be unchanged during making of a scan, but in other embodiments the relative orientation of the center planes is varied during a scan, e.g. in view of assessment of a region of interest in the object 250.

In an embodiment, the collimator assembly 260, is configured to scan the slit fields of view through respective portions of the imaging space substantially in the first direction by both moving the slit plate member in the first direction YY, here by drive 195, and rotating the rotatable slit members 273 by drive(s) 275.

For example, each slit 274 has a smallest width of between 1 and 3 millimeter.

In a practical embodiment, as shown, the slit width is fixed and lies between 1 and 3 millimeters. Possibly the slit width is variable, e.g. within such a range.

Possibly one or more of the slits can selectively be closed, e.g. by provision of a corresponding shutter or by reducing the width in a variable slit width collimator assembly to zero.

For example, the spacing distance “d” between slit structures 272 is at least 20 millimeters, e.g. between 25 and 50 millimeters, e.g. for scintimammography.

With reference to figures 7 and 8 now yet another embodiment of a collimator 360 will be discussed.

The collimator 360 can, for example, be used in the context of the system described with reference to figure 1, e.g. as replacement for the collimator assembly 160, and/or for collimator part 85 in the assembly 60.

The collimator 360 extends in a plane and has an object side configured to face the imaging space, e.g. space 200, and a detector side facing a gamma sensitive detector, e.g. detector 180, which arranged at the detector side of the collimator to receive gamma radiation passing through the collimator 360.

The collimator 360 comprises multiple converging fan beam collimator portions 361 which are arranged in series in a first direction Y of the collimator 360.

Each converging fan beam collimator portion 361 has a fan beam field of view defined by holes, here schematically depicted in area 362 of the object side only for reasons of clarity.

These holes form an elongated 2D - array of openings in the object side extending in the first direction Y and in a second direction X perpendicular to the first direction. The holes also form a 2D - array of openings in the detector side.

As shown and preferred, the fan beam collimator portions 381 are solid, rigid portions.

The 2D - arrays of openings in the object side belonging to the different portions 361 are spaced from one another in the first direction over a spacing distance “d”.

The gamma camera to which the collimator 360 belongs, e.g. camera 50 and/or camera 150, is configured to move the collimator 360 as a whole in the first direction Y so as to scan each of the fan beam fields of view through a portion of the imaging space 200 substantially in the first direction Y and to image each of the scanned fan beam fields of view onto a respective projection area 181 of the detector 80, 180.

Preferably, the projection areas 181 do not overlap one another.

The angle a may be chosen in view of optimized imaging. It is noted that this angle a can be chosen to be large. The latter, e.g., may have the effect that a region in the object is viewed during scanning by lines of views (defined by the holes of a portion 361) having significantly different angles, enhancing accuracy of localization.

The linear scan motion can be performed by a drive of the collimator, e.g. drive 95 or drive 195.

As shown, the collimator 360, e.g. for use in scintimammography, has between 3 and 6 fan beam collimator portions 361, here five.

The number, shape, and/or angular orientation of the holes 362 in each fan beam portion 361 may be varied in view of optimized imaging of the object, e.g. female breast 250, held in the imaging space 200. The fan beam portions 362 may be identical, but may also differ from one another. For example, outer portions 361 may have holes under a greater angle relative to the object side than holes of inner portions 361 of the collimator.

A fan beam portion 361 may have, as shown, holes 362 which are symmetrically arranged relative to a normal center plane of the fan beam portion. Embodiments wherein one or more fan beam portions 361 has an asymmetric arrangement are also envisaged.

The scan motion of the collimator 360 is , preferably such, that each location in the object to be imaged is seen by lines of view (defined by the holes 362) under a variety of angles, e.g. belonging to one portion 361 or to multiple, e.g. two, portions 361.

The figures 9a — f schematically illustrate different slat configurations for one or more embodiments of a collimator assembly according to the invention. Herein reference numeral 180 denotes the detector, 183 the incident side thereof, and 165 the slat section with slats 166.

In figure 9a the slats 166 are all perpendicular to the plane of the collimator assembly and equidistant spaced from one another, e.g. the slats 166 being fixed in this configuration.

As discussed, in embodiments, the spacing between slats 166 is adjustable by means of a corresponding slat spacing adjustment mechanism. This is illustrated in figure 2b where the spacing between the slats has been reduced. The slat spacing adjustment mechanism may be embodiment to maintain an equidistant spacing between all slats 166 and/or to allow for different spacings between slats 166 of section 165.

As discussed, in embodiments, the slats 166 are arranged or arrangeable in a converging configuration, e.g. as illustrated in figures 9c, 9d, 9e.

As discussed, in embodiments, a slat inclination mechanism is provided allowing multiple, e.g. all, spaced elongated slats 166 to have a variable inclination, e.g. over an inclination range including a perpendicular orientation (fig. 9a) relative to the plane of the collimator assembly and one or more inclined configurations (one or more of figs Sc, 9d, Se, 9f).

For example, the slat inclination mechanism is configured to provide a perpendicular orientation relative to the plane of the collimator assembly of all slats, or of a majority of the slats, and an inclined orientation of multiple slats, e.g. all slats or of a majority of the slats, e.g. a converging (fig. 9c, 9d, Se) and/or diverging (fig. 9f) arrangement of multiple slats 166.

In another embodiment, the slat section 165 is configured such that the spacing between multiple slats 166, e.g. a majority or all of the slats, is adjustable, e.g. by a corresponding slat spacing adjustment mechanism. This allows to vary the sensitivity of the slat section.

Figure 9c shows the slats 166 having a symmetrical inclination relative to a central normal plane 168 of the slat section 165 collimator assembly, here a converging symmetrical inclination.

Figure 2d and 9e show the slats 166 having an asymmetrical inclination relative to a central normal plane 168 of the slat section 185 of the collimator assembly, here a converging asymmetrical inclination.

Figure 9f show the slats 166 having an asymmetrical inclination relative to a central normal plane of the slat section 165 of the collimator assembly, here a diverging asymmetrical inclination.

As discussed herein, in embodiments, the slats 166 are variable both with respect to their spacing and with respect to their inclination.

Whilst in the description of the figures examples of the collimator assembly have been discussed in the context of an exemplary system for scintimammography, the inventive concepts may be implemented in different systems for scintimammography as well as for other applications.

As indicated in the introduction, the inventive concepts may be implemented for other objects, e.g. other human body parts, like the head, torso (e.g. for heart imaging), and/or limbs of the human body, etc.

The inventive concepts may also be implemented for imaging other organisms, e.g. animals, plants, etc.

The inventive concepts may also be implemented for imaging other objects than humans, organisms. For example, the inventive concepts may be implemented for imaging objects in nuclear industry and/or research, industrial applications, etc.

For example, a system may lack the immobilization plates, e.g. immobilization of the object being done by another immobilization device or immobilization being absent, e.g. the object not requiring immobilization.

For example, a system may have three, four, five, or more gamma cameras arranged into image an object in the imaging space. For example, three or more gamma cameras are arranged in a polygonal configuration about the imaging space, e.g. three cameras in a triangular configuration.

Claims

CONCLUSIONS

1. A gamma radiation imaging system for imaging an object, for example for scintimammography, comprising: - a gamma camera configured and arranged to detect gamma radiation emitted from an object received in an imaging space, for example a human body part, for example a female breast, the gamma camera comprising: - a collimator assembly extending in a plane and having an object side facing the imaging space and a detector side, - a gamma-sensitive detector arranged on the detector side of the collimator assembly to receive gamma radiation passing through the collimator assembly, the collimator assembly comprising: - a slit portion on the object side, - a slat portion on the detector side, the slat portion comprising a plurality of spaced apart elongated slats having a length in a first direction of the collimator assembly, a distance between the adjacent slats in a second direction of the collimator assembly, and a height in a third direction of the collimator assembly perpendicular to the plane of the collimator assembly, collimator assembly, wherein the slit portion is adjacent to the slat portion, said slit portion comprising a plurality of slit structures each extending in the second direction, preferably at least three slit structures, said slit structures each having one slit or having a plurality of slits in close proximity to each other, each slit structure having a respective slit structure field of view having an acceptance angle, said slit structures being disposed in said slit portion spaced apart from each other in said first direction, said collimator assembly being configured to move at least said slit portion and/or said slit structures thereof so as to scan each of said slit structure fields of view through a portion of said imaging space substantially in said first direction and to image each of said scanned slit structure fields of view onto a respective projection area of said camera.

2. The system of claim 1, wherein the slit member is a slit plate member having the plurality of slit structures each extending in the second direction, the collimator assembly being configured to scan the slit structure fields of view through respective portions of the imaging space substantially in the first direction by moving the slit plate member in the first direction.

3. The system of claim 2, wherein the slit structures are spaced apart from each other in the first direction at a regular interval, and wherein the gamma camera is arranged to move the slit plate member in the first direction by a scanning distance corresponding to the regular interval or greater, for example less than twice the regular interval.

4. A system according to claim 2 or 3, wherein the slot structures are each formed in the slot plate member as a single slot or multiple, for example two, slots close to each other, wherein beveled edges within the slot plate member provide the acceptance angle with the respective slot field of view for the slot structure.

5. A system according to any one of claims 1 to 4, wherein the acceptance angle of each slot structure is between 20° and 70°.

6. A system according to any one or more of claims 1 to 5, wherein the acceptance angle is symmetrical with respect to a normal plane perpendicular to the object side of the slit portion, or wherein the acceptance angle is asymmetrical with respect to a normal plane perpendicular to the object side of the slit portion, for example wherein the slit structure fields of view converge with respect to each other.

7. The system of claim 1, wherein the slit member is a slit plate member provided with a plurality of slit structures extending in the second direction, each slit structure comprising an elongated rotatable slit member extending in the second direction and rotatably received in a corresponding elongated passage in the slit plate member to be rotatable about a rotational axis, the rotatable slit member having one or more slits in close proximity through the rotatable slit member, preferably one slit, a rotation drive being provided for rotating the rotatable slit members through a rotational angle about the rotational axis, the collimator assembly being configured to scan the slit fields of view through respective portions of the imaging space substantially in the first direction by rotating the rotatable slit members.

8. A system according to claim 7, wherein each rotatable slit member comprises a single slit or multiple, for example two, slits close together, wherein beveled edges in the rotatable slit member provide the acceptance angle with the respective slit structure field of view.

9. The system of claim 8, wherein the acceptance angle is between 10° and 50°.

10. A system according to any one or more of claims 1 to 9, wherein the slit structure fields of view each have a center plane, and wherein the slit portion is arranged such that the center planes of several or all of the slit structure fields of view are parallel to each other.

11. A system according to any one or more of claims 1 to 9, wherein the slit structure fields of view each have a center plane, and wherein the slit portion is arranged so that the center planes of several or all of the slit structure fields of view converge.

12. System according to one or more of claims 6 to 11, wherein the rotation drive is arranged to rotate rotatable slit members simultaneously and, possibly, in an identical manner.

13. A system according to any one of claims 6 to 12, wherein the rotary drive is adapted to independently rotate rotatable slit members.

14. The system of any one of claims 6 to 13, wherein the collimator assembly is configured to scan the slit fields of view through respective portions of the imaging space substantially in the first direction by both moving the slit plate members in the first direction and rotating the rotatable slit members.

15. System according to one or more of claims 1 to 14, wherein each slot has a width of between 1 and 3 millimeters, and wherein the spacing, for example the regular spacing, between adjacent slot structures is at least 15 millimeters, for example between 15 and 50 millimeters.

16. A system as claimed in any one of claims 1 to 15, wherein the collimator assembly is arranged such that, with the collimator assembly considered stationary, the projection areas of the slit structures are fields of view non-overlapping.

17. A system according to any one of claims 1 to 16, wherein the system comprises a plurality of gamma cameras, for example two gamma cameras on opposite sides of the imaging space.

18. The system of any one of claims 1 to 17, wherein the system further comprises: - a frame supporting a first immobilization plate and a second immobilization plate, the second immobilization plate being arranged or being arrangeable to extend parallel to the first immobilization plate, the first and second immobilization plates defining the imaging space therebetween and being adapted to clamp a body part to be imaged, e.g. a human body part, e.g. a female breast, between the immobilization plates, the gamma camera being positioned with its collimator assembly adjacent to the first immobilization plate.

19. The system of claim 18, wherein the system comprises a second gamma camera positioned with its collimator assembly adjacent to the second immobilization plate.

20. The system of claim 18 or 19, wherein at least one of the first and second immobilization plates is provided with a grid of instrument openings each configured to pass an instrument through the first immobilization plate, for example a biopsy instrument.

21. The system of any one of claims 1 to 20, wherein the system is configured for scintimammography, wherein a female breast is received in the imaging room.

22. The system of claim 21, wherein the slit structures extend in the axial direction of the female breast from torso to nipple, and the first direction or direction of displacement is in a plane parallel to a coronal plane of the female breast.

23. The system of any one of claims 1 to 22, wherein the collimator assembly has between 3 and 10 slit structures.

24. A gamma camera collimator according to any one of claims 1 to 23.

25. A gamma camera collimator assembly, for example for use in scintimammography, the collimator assembly comprising: - a slit member on the object side, - a slat member on the detector side, the slat member comprising a plurality of spaced apart elongated slats having a length in a first direction of the collimator assembly, a distance between adjacent slats in a second direction of the collimator assembly, and a height in a third direction of the collimator assembly perpendicular to the plane of the collimator assembly, the slit member comprising a slit plate member provided with a plurality of slit structures extending in the second direction, each slit structure comprising an elongated rotatable slit member extending in the second direction and rotatably received in a corresponding elongated passage in the slit plate member so as to be rotatable about a rotation axis, the rotatable slit member being provided with one or more slits in close proximity to each other by the rotatable slit member, preferably one slit, wherein a rotation drive is provided for rotating the rotatable slit members through a rotation angle about the rotation axis, wherein the collimator assembly is arranged to scan the slit fields of view through respective portions of the imaging space substantially in the first direction by rotating the rotatable slit members.

26. Method for gamma imaging of an object, for example a human body part, for example a female breast, using the system according to one or more of claims 1 to 23.

27. Method according to claim 26, wherein use is made of a system at least according to claim 7, wherein the collimator assembly is arranged and operated such that in a first imaging step all rotatable slit structures perform the same rotation with all center planes of the fields of view parallel to each other, and wherein on the basis of the first imaging step a localization of a region of interest is determined, and wherein in a second imaging step, the slit structures are rotated so as to have a focus towards the region of interest, for example a converging arrangement of the center planes of at least some slit structures.

28. A gamma-ray imaging system for imaging an object, for example for scintimammography, comprising:

- a gamma camera arranged to detect gamma radiation emitted from an object received in an imaging room, for example a human body part, for example a female breast,

where the gamma camera comprises:

- a collimator, which extends in a plane with an object side facing the imaging space and a detector side,

- a gamma-sensitive detector disposed on the detector side of the collimator for receiving gamma radiation passing through the collimator, the collimator comprising a plurality of converging fan-beam collimator sections disposed in series in a first direction of the collimator, each fan-beam collimator section having a fan-beam field of view defined by holes forming a grid of apertures in the object side, the grid extending in the first direction and in a second direction perpendicular to the first direction, and forming a grid of apertures in the detector side, the grids of apertures in the object side being spaced apart in the first direction by an intermediate distance,

wherein the gamma camera is configured to move the collimator in the first direction to scan each of the fan beam fields of view through a portion of the imaging space substantially in the first direction and to image each of the scanned fan beam fields of view onto a respective projection area of the detector.