WO2010136851A1

WO2010136851A1 - Imaging device for positron emission tomography

Info

Publication number: WO2010136851A1
Application number: PCT/IB2009/053529
Authority: WO
Inventors: Guillaume Montemont; Françoise Mathy; Dimitri Visvikis; Serge Maitrejean
Original assignee: Biospace Lab
Priority date: 2009-05-26
Filing date: 2009-05-26
Publication date: 2010-12-02
Also published as: EP2435853A1

Abstract

An imaging device for positron emission tomography (PET), comprising an examination volume extending along a longitudinal direction (X), and detectors adapted to determine a position of a radiation interaction, and a lateral detection module comprising a first group of the detectors and disposed on a lateral side of the examination volume. The imaging device further comprises an adjusting device of the lateral detection module, adapted to expand a longitudinal dimension (LD) of the lateral detection module along the longitudinal direction (X).

Description

Imaging device for positron emission tomography

FIELD OF THE INVENTION

The present invention concerns imaging device for positron emission tomography.

BACKGROUND OF THE INVENTION

The present invention concerns more precisely imaging device for positron emission tomography, comprising:

- an examination volume adapted for receiving a body to be imaged emitting a radiation, the examination volume extending along a longitudinal direction, having a lateral side along and around this longitudinal direction and two end sides at each end in this longitudinal direction,

- detectors, each detector comprising at least a semiconductor material and electrodes adapted to determine a three-dimensional position of an radiation interaction within the semiconductor material of the detector,

- a lateral detection module comprising a first group of said detectors, disposed along said longitudinal direction on the lateral side of the examination volume, and having a longitudinal dimension along said longitudinal direction.

Positron emission tomography (PET) is an imaging method based on detection of a radiation emitted from electron-positron annihilation events within the body to be imaged. This radiation is typically a pair of photons emitted in opposite directions and detected by opposite detectors in the PET imaging device.

Usually, a body to be imaged is disposed along a longitudinal direction and the PET imaging device has rings of detectors arranged around said direction in a substantially perpendicular plane thereof. These detectors are sensing radiations in a field of view (FOV) that is substantially the disc inside the ring. The detectors should be close to each other to avoid gaps and the loss of radiation detection. The imaging device also comprises means to move the body along this longitudinal direction and to calculate an image of the body. Unfortunately, in such cylindrical arrangement of a PET imaging device the sensivity of the imaging device is good in the centre of the disc and decreases with distance from this centre.

It is known from US-5 854 489 to have a PET detector enabling detection of the depth of interaction (DOI) of the radiation in the detector. Such detectors enable to get rid of the previously compulsory radial distribution of detectors.

Thus, PET devices having a rectangular transaxial field of view, and four detection modules arranged around the field of view were proposed. The detectors of these PET devices have a side surface to front surface contact arrangement. Thanks to this arrangement, gaps are reduced and the size of the field of view can be more easily adjusted closely to the body without gaps. The sensivity of the imaging device is therefore improved.

OBJECTS AND SUMMARY OF THE INVENTION

One object of the present invention is to provide an imaging device for positron emission tomography with a greater flexibility.

To this effect, the imaging device for positron emission tomography further comprises an adjusting device adapted to expand the lateral detection module in the longitudinal direction between a packed configuration and an expanded configuration and wherein:

- in the packed configuration, said longitudinal dimension is higher than transverse dimensions of the examination volume along both transverse directions (Y, Z), said transverse directions being perpendicular to the longitudinal direction (X) , and - in the expanded configuration, said longitudinal dimension is higher than the longitudinal dimension in the packed configuration.

Thanks to these features, the examination volume has an adjustable longitudinal dimension and the imaging device can be adjusted to bodies of different lengths with a minimal amount of detectors, so that the body can be completely included inside the field of view of the imaging device. Therefore, the PET imaging device does not need to move the body to be imaged along the longitudinal direction .

The present invention concerns also an imaging device for positron emission tomography, comprising:

- an examination volume adapted for receiving a body to be imaged emitting a radiation,

- detectors adapted to determine a position of a radiation interaction,

- a detection module comprising a group of said detectors, disposed along a direction, and having a dimension along said direction.

The imaging device for positron emission tomography further comprises an adjusting device adapted to expand the detection module in said direction between a packed configuration and an expanded configuration, and wherein: - in the packed configuration, said detectors of said group have an initial position, and

- in the expanded configuration, said detectors of said group are tilted relative to said initial position of the detectors in the packed configuration and the dimension is higher than the dimension in the packed configuration.

Other objects, features and advantages of the invention will be apparent from the following detailed description of seven of its embodiments given by way of non-limiting example, with reference to the accompanying drawings . BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings :

- Figure Ia is a perspective view of a semiconductor layer of a detector, - Figure Ib is a diagram of a detector,

- Figure 2 is a perspective view of an assembly of detectors,

- Figures 3a, 3b and 3c are longitudinal views in packed, intermediate and expanded configurations of a first embodiment of the invention,

- Figure 3d is a transversal view of the first embodiment of the invention,

- Figures 4a, 4b and 4c are longitudinal views in packed, intermediate and expanded configurations of a second embodiment of the invention,

- Figure 4d is a transversal view of the second embodiment of the invention,

- Figure 5a is a perspective view of another assembly of detectors, - Figure 5b is a side view of a lateral detector module with the assembly of figure 2,

- Figure 5c is a side view of a lateral detector module with the assembly of figure 5a,

- Figures 6a, 6b and 6c are longitudinal views in packed, intermediate and expanded configurations of a fourth embodiment of the invention,

- Figure 6d is a transversal view of the fourth embodiment of the invention,

- Figures 7a, 7b and 7c are longitudinal views in packed, intermediate and expanded configurations of a fifth embodiment of the invention,

- Figure 7d is a transversal view of the fifth embodiment of the invention, in the enlarged configuration,

- Figure 7e is a transversal view of the fifth embodiment of the invention, in the retracted configuration, - Figures 8a, 8b and 8c are longitudinal views in packed, intermediate and expanded configurations of a sixth embodiment of the invention,

- Figure 8d is a transversal view of the sixth embodiment of the invention,

- Figures 9a, 9b and 9c are longitudinal views in packed, intermediate and expanded configurations of a seventh embodiment of the invention,

- Figure 9d is a transversal view of the seventh embodiment of the invention,

- Figures 10a, 10b and 10c are longitudinal views of an example of a first adjusting device in packed, intermediate and expanded configurations, said first adjusting device being at least adapted to the first to fifth embodiments of the invention,

- Figures 11a, lib and lie are longitudinal views of an example of a second adjusting device in packed, intermediate and expanded configurations, said second adjusting device being adapted to the sixth and seventh embodiments of the invention.

MORE DETAILLED DESCRIPTION

In the various figures, the same reference numbers indicate identical or similar elements. The direction X is a longitudinal direction, a direction Y or Z is a transversal direction.

Figure Ia is a perspective view of a layer 10 of a detector suitable for the present imaging device. For example, the layer of detector comprises a semiconductor CdTe substrate 11, with a top surface 14 and a bottom surface 16. The substrate 11 has a small thickness Tl and a width Wl and a length Ll. The top surface 14 comprises a cathode 12a formed by series of regularly spaced electric conductive stripes parallel to each other. The bottom surface 16 comprises an anode 12b also formed by series of regularly spaced electric conductive stripes parallel to each other. The stripes of the cathode and anode are substantially perpendicular to each other. The anode and cathode produce a biasing electric field inside the substrate 11. The semiconductor material can be a CdTe semiconductor material, or a CdZnTe semiconductor material, or a Ge semiconductor material, or an Hgl2 semiconductor material, or a Si semiconductor material, or a TlBr semiconductor material, for example. An incident radiation R may produce an interaction inside the semiconductor substrate 11 providing mobile electrons and holes. The electrons drift toward the bottom surface 16 (anode) , while the holes drift toward the top surface 14 (cathode) . The drift of electrons and holes produce an electronic signal on a pair of anode-cathode stripes that is representative of a position of the radiation interaction in the length direction L and width direction W inside the substrate 11.

As shown on figure Ib, detector 20 may comprise a stack of several layers 10 of small thickness Tl to form a detector 20 of thickness T2. For example, a thickness Tl could be 1 mm, the width Wl and the length Ll could be 16 mm, and the detector 20 could have 10 or more stacks. A radiation interaction is detected in a specific layer of this stack. The position of a radiation interaction in the thickness direction T inside the detector 20 is therefore determined at least by said specific layer, and is for example approximated to be in the median plane between the surfaces 14 and 16. A detector control device 21 comprises a clock 22 and measures charges between each anode stripe and each cathode stripe of each stack of the detector 20, so that it can provide to a central unit 23, such as computer, the information of an event of a radiation interaction, the date of this radiation interaction, and a position in the three dimensions (3D) of this radiation interaction inside the detector 20.

Several detectors 20 are arranged around a longitudinal direction X, for example in a ring configuration, and are connected to the central unit 23. In the case illustrated in figure 2, eight detectors 20 form an assembly. This assembly has in a cross section perpendicular to the longitudinal direction X an octagonal shape. However, this assembly may have a triangular shape, a rectangular shape, a polygonal shape or a circular shape, depending on the number and size of the detectors 20. This assembly has an inner dimension Di and a length Wi along direction X that determines an inner volume of examination. The body to be imaged is installed along the longitudinal direction X to provide 3D images of said body. In all the following described embodiments, the body B to be imaged is represented by a mouse. In each configuration, mice of different length, measured along the longitudinal direction, could be used for the illustration of the advantage of the invention. The PET imaging device of the invention is particularly efficient for imaging small animals, such a mouse, because this PET imaging device provides a good sensivity in all its configurations, but the features of such imaging device can be adapted to imaging devices for imaging human or other bodies. Such as mice and humans, most of the bodies which can be subject to PET imaging have a longitudinal dimension which is their longest dimension (for humans, this dimension is usually referred to as the height) .

A first embodiment of the invention is shown on figures 3a to 3d. The PET imaging device comprises a lateral detection module 30 comprising, for example, along the longitudinal direction X four assemblies 31, 32, 33, 34 similar to the one of figure 2 and defining an examination volume EV inside these assemblies and along the longitudinal direction X. The four assemblies comprise detectors 20. But, other designs of the lateral detection module 30 can be used, organising the detectors 20 of said lateral detection module 30 in another manner.

The examination volume EV is adapted for receiving a body B to be imaged, such as a body B emitting a radiation R typical of PET imaging. The examination volume EV comprises a lateral side along and around the longitudinal direction X and two end sides at each end of this longitudinal direction X. The lateral side of the examination volume EV is at least partially covered by the lateral detection module 30. The lateral detection module 30 has a longitudinal dimension LD along the longitudinal direction X, a first transversal dimension TD_Y along the lateral direction Y, and a second transversal dimension TD_Z along the vertical direction Z.

Optionally and as represented on the figures, each end side of the examination volume EV is also partially covered by an end detection module 40, 50. The end detection modules 40, 50 are shown on figure 3a to 3c by their transversal section. The end detection module 40 is shown on figure 3d by its face. The examination volume EV is therefore an octagonal cavity extruded along the longitudinal direction X inside the lateral detection module 30.

Figure 3a represents the first embodiment of the imaging device in a packed configuration, wherein the assemblies 31, 32, 33, 34 are all close to each other, for example so that the detectors are in contact along said longitudinal direction X.

Figure 3b represents the same in an intermediate configuration, wherein the assemblies 31, 32, 33, 34 are each separated from the neighbour by a gap G. The examination volume is therefore expanded according the longitudinal direction X.

Figure 3c represents the same in an expanded configuration, wherein the assemblies 31, 32, 33, 34 are each separated from the neighbour assembly by a gap G larger than the gap of the intermediate configuration of figure 3b. The longitudinal dimension LD of the lateral detection module 30 is higher in that expanded configuration than in the packed configuration.

Consequently, the examination volume is longer in the expanded configuration than in the packed configuration, and provides more flexibility, and it is possible to install inside the examination volume EV of the imaging device in the expanded configuration a longer body B than in the packed configuration. In any case, the body to be imaged will be placed in the examination volume with its longitudinal direction aligned with that of the imaging device.

The imaging device comprises an adjusting device adapted to expand the lateral detection module 30 from the packed configuration of figure 3a to expanded configuration of figure 3c. The description of an example of such adjusting device will be given later.

For example, a small mouse must be imaged. A radiopharmaceutical is introduced in the body of the animal. The small mouse is installed in the imaging device of figure 3a, wherein all the detectors 20 of the lateral detection module 30 are close to each other, and the end detection modules 40, 50 are closing the imaging device along the longitudinal direction X.

The radiopharmaceutical inside the body B decays, positrons are generated that react with an electron in what is known as an annihilation event, and rays of radiation are emitted in directions approximately 180° opposite directions towards detectors of the imaging device.

A radiation arrives to a detector 20 composed of a stack of semiconductor layers 10, through a lateral surface (figure Ia) or the top surface 14, or the bottom surface 16. In all the cases, the radiation interacts inside the semiconductor material of the detector 20. The radiation interaction is detected by electrodes that provide the tree-dimensional position and date of the radiation interaction inside the detector to a central unit 23. A pair of detectors provides radiation interactions events to the central unit 23. Because, rays travel in opposite directions, the positron annihilation occurred along a line of coincidence connecting the detected three- dimensional positions inside said pair of detector. The central unit 23 implements a software that determines the configuration of the imaging device, determines the positions of the detectors 20 of the imaging device, reads the positions of the radiation interactions in each detector and converts these positions in absolute three- dimensional position of the imaging device, and define the line of coincidence between two radiation interactions validating grouping conditions. For example, grouping conditions could be one or a combination of the following conditions: difference of the date of the radiation interactions lower than a time difference limit, radiation interactions belonging to opposite detectors inside the imaging device, etc. Opposite detectors are detectors that are positioned inside the imaging device substantially symmetrically relative to the centre of the examination volume or imaging device, or at least on the half volume opposite to the detector 20 detecting said radiation interaction .

In case of the packed configuration of figure 3a, the examination volume EV is completely covered by detectors, and any radiation emitted in said examination volume in any direction should pass through a detector. There a very small loss. Such imaging device has a good sensivity .

For example, a mouse with a longer body B is installed in the same imaging device. The lateral detection module of said imaging device is expanded along the longitudinal direction X, such as on figure 3c, so that the body B of this mouse may be included inside the examination volume EV. End detection modules 40, 50 are eventually closing the imaging device along the longitudinal direction X. Thanks to these configuration modifications, the same imaging device is able to image or analyse a small mouse and a longer mouse.

A second embodiment of the invention is shown on figures 4a to 4d, and differs from the first embodiment by its adjusting device that is adapted to move the detectors 20 of the lateral detection module 30 along a transversal direction, the YZ plane, so that the lateral detection module 30 has: - a retracted configuration corresponding to the figures 3a to 3d of the first embodiment, and

- an enlarged configuration, in which said detectors are moved substantially in the plane YZ along a radial direction (figure 4d) . The first and second transversal dimensions TD_x and

TD_Y of the lateral detection module 30 are higher in the enlarged configuration than in the retracted configuration.

Said detectors are in the plane YZ separated from each other, letting some empty spaces SP between these detectors around the longitudinal direction X. These spaces are possibly regularly spaced as represented.

The end detection modules 40, 50 may each comprises portions that are able to move substantially in the plane YZ along a radial direction. For example, an end detection module 40, 50 comprises four detectors 41, 42, 43, 44 disposed in the four quadrants of the YZ plane. In the enlarged configuration, these four detectors are separated by two spaces, SPY along the direction Y and SPZ along the direction Z. The examination volume EV of the imaging device is larger in the transversal directions Y and Z. This is more flexible to install a larger body B than in the first embodiment (especially a body which is larger in the directions transverse to its longitudinal direction) . Thanks to these features, the sensitivity of the imaging device is good in the retracted configuration and in the enlarged configuration.

The other features of this second embodiment of the invention are identical to the first embodiment of the invention. In particular, the adjusting device is adapted to expand the lateral detection module along the longitudinal direction X between the packed configuration (figure 4a) and the expanded configuration (figure 4c), in the enlarged configuration or in the retracted configuration . The longitudinal adjustment is the ratio of the longitudinal dimension LD in the expanded configuration and the longitudinal dimension LD in the packed configuration. A transversal adjustment is the ratio of a transversal dimension in the enlarged configuration and the same transversal dimension in the retracted configuration. The longitudinal and transversal adjustments may be linked or independent. The adjusting devices of the imaging device may be adapted to provide same or different adjustments.

On the figure 4c of this second embodiment, the lateral detection module 30 are expanded and enlarged so that a bigger and longer mouse may be imaged, with the same imaging device of figure 4a. Such imaging device is very flexible .

A third embodiment of the invention is shown on figures 5a to 5c, and differs from the first embodiment by the organisation of the detectors inside the lateral detection module 30.

Figure 5a a variant of the assembly of detectors shown on figure 2. Compared to the assembly of figure 2, in this new assembly the eight detectors 20a to 2Oh are not all aligned in a transversal plane YZ. The detectors 20a, 20c, 2Oe and 2Og are shifted in one direction (positive) along the longitudinal direction X, and the others, the detectors 20b, 2Od, 2Of and 2Oh are shifted in the opposite direction (negative) along the longitudinal direction X, forming an assembly of detectors that looks like a ring with left-right teeth. Such assembly can be used in the general design of the first embodiment.

Figure 5b show a side view of the lateral detector module 30 comprising the assembly of figure 2, in the expanded configuration. In such design, there is a transversal space Sl between each assembly.

Figure 5c show a similar side view of the lateral detector module 30 of the third embodiment comprising the assembly of figure 5a. In such design, between each assembly, there are small and space spread square spaces S2, forming a sort of checkerboard. Thanks to this geometry, the sensivity of the imaging device is improved in the expanded configuration.

A fourth embodiment of the invention is shown on figures 6a to 6d, and differs from the first embodiment by its lateral detection module 30 comprising at least two layers Ll, L2 of detectors 20. In the packed configuration of figure 6a, the detectors 20 of each layer Ll, L2 are close to each other along the longitudinal direction X. The detectors 20 of the second layer L2 are shifted along the longitudinal direction X in comparison to the detectors of the first layer Ll.

In the intermediate and expanded configuration of respective figures 6b and 6c, the detectors 20 of each layer Ll, L2 are separated from the neighbour of the same layer by a gap, similarly as in the first embodiment. Due to the shift of the detectors of the second layer L2, the detectors 20 of the second layer L2 are transversally covering a first gap Gl between consecutive detectors of the first layer Ll along the longitudinal direction X, and the detectors 20 of the first layer Ll are transversally covering a second gap G2 between consecutive detectors of the second layer L2 along the longitudinal direction X.

Thanks to these features, the gaps of each layer are covered by detectors of the other layer, and the lateral detection module 30 does not have any space along a transversal direction wherein a radiation can go through without being detected. The imaging device of this embodiment is able to expand along the longitudinal direction X as the first embodiment, and has a better sensitivity .

A fifth embodiment of the invention is shown on figures 7a to 7d, and differs from the fourth embodiment by the adjusting device that is also adapted to move the detectors 20 of the lateral detection module 30 along a transversal direction, in the YZ plane. As in the second embodiment, this new embodiment has:

- a retracted configuration corresponding to the figures 6a to 6d of the fourth embodiment, and

- an enlarged configuration, wherein said detectors are moved substantially in the plane YZ along a radial direction (figure 7d) .

The first and second transversal dimensions TD_x and

TD_Y of the lateral detection module 30 are higher in the enlarged configuration than in the retracted configuration. These changes are clearly shown by the figure 7e that is a transversal view in the retracted configuration and by the figure 7d that is a transversal view in the enlarged configuration .

The detectors 20 are in the plane YZ separated from each other. In the enlarged configuration there may be some small spaces between the detectors. These spaces are possibly regularly spaced and spread around the outer surface of the lateral detection module 30. These spaces are limited in surface as the lateral detection module 30 comprises two layers Ll, L2 of detectors, the detectors of the first layer Ll being shifted transversally relative to the detectors of the second layer L2. Looking from outside, a side view of the lateral detection module 30 would look like two superposed checkerboards shifted one relative to the other to minimise the holes through the lateral detection module 30.

The end detection modules 40, 50 may each comprises portions that are able to move substantially in the plane YZ along a radial direction. For example, an end detection module 40, 50 comprises four detectors 41, 42, 43, 44 disposed in the four quadrants of the YZ plane. In the enlarged configuration, these four detectors are separated by two spaces, SPY along the direction Y and SPZ along the direction Z.

The examination volume EV of the imaging device is larger in the transversal directions Y and Z. This is more flexible to install a larger body B than in the previous embodiment. Thanks to these features, the sensitivity of the imaging device is good in the retracted configuration and in the enlarged configuration. The other features of this fifth embodiment of the invention are identical to the fourth embodiment of the invention. In particular, the adjusting device is adapted to expand the lateral detection module 30 along the longitudinal direction X between the packed configuration (figure 7a) and the expanded configuration (figure 7c) , in the enlarged configuration or in the retracted configuration (see figures 6a and 6c).

A sixth embodiment of the invention is shown on figures 8a to 8d, and differs from all the preceding embodiments by the ability to tilt the detectors 20 of the lateral detection module 30, so that a detector 20 is positioned like roof tiles.

In this embodiment, the detectors 20 of the lateral detection module 30 have, in an initial position of the packed configuration of figure 8a, a size along the vertical direction Z higher than a size along the longitudinal direction X. All the detectors of the lateral detection module 30 are tilted of an angle A relative to their initial position. While a detector 20 is tilted or rotated, the next detector 20 along the longitudinal direction X is also tilted of the same angle A and translated along said longitudinal direction X. The lateral detection module 30 is therefore expanded from the packed configuration (figure 8a) , to an intermediate configuration (figure 8b) and to an expanded configuration (figure 8c) .

The longitudinal dimension LD of the lateral detection module 30 is longer in the expanded configuration than in the packed configuration.

The detectors 20 that are tilted are transversally overlapping their neighbours. Such organisation of the detectors 20 in the lateral detection module 30 is able to produce high expansion ratios without empty space through which a radiation could go through without being detected.

In the packed configuration of figure 8a, the examination volume EV is completely covered by detectors, and any radiation emitted in said examination volume in any direction should pass through a detector.

In the expanded configuration of figure 8c, the examination volume EV is also completely covered by detectors, and any radiation emitted in said examination volume in any direction should pass through a detector.

In any configuration, such imaging device of the sixth embodiment has a good sensivity.

Thanks to the configuration modifications between the packed configuration and the expanded configuration, the same imaging device is able to image or analyse a small mouse of figure 8a and a longer mouse of figure 8c.

The imaging device of this sixth embodiment has simultaneously a great flexibility and a good sensivity.

A seventh embodiment of the invention is shown on figures 9a to 9d, and differs from the sixth embodiment by the added ability to expand in the transversal directions Y and Z, with a similar organisation of the detectors 20 as described above on all the faces of the lateral detection module 30 and on the end detection modules 40, 50. The adjusting device is adapted to adjust the size of the lateral detection module 30 along the longitudinal direction X, and additionally along one or both the transversal directions Y, Z. Each of the end detection module 40, 50 may optionally have an adjusting device adapted to adjust its size along the same directions.

Along the longitudinal direction X, the imaging device has packed configuration and expanded configuration.

Along a transversal direction Y or Z, the imaging device has a retracted configuration and an enlarged configuration.

These configurations can be combined. Figure 9a represents the imaging device in the packed-retracted configuration. The figure 9c represents the imaging device in the expanded-enlarged configuration. In this last configuration, the longitudinal dimension LD of the lateral detection module is longer than in the packed configuration, and the second transversal dimension TD_Z is larger than in the retracted configuration.

Thank to these features, the imaging device of this embodiment is again more flexible, to install various lengths and sizes of body B to be imaged. A small mouse can be imaged (figure 9a) or a big and longer mouse can be imaged (figure 9c) .

Figures 10a, 10b and 10c are longitudinal views of an example of a first adjusting device 60 in packed, intermediate and expanded configurations, said first adjusting device 60 being at least adapted to the first to fifth embodiments of the invention.

These figures show three detectors 20a, 20b, 20c aligned along the longitudinal direction X. The adjusting device 60 comprises:

- a first plurality of hinges 62, each hinge of this plurality being attached to a detector,

- a second plurality of hinges 63, and - a plurality of arms 61 linking successively a hinge of the first plurality of hinges 62 to a hinge of the second plurality of hinge 63, or reciprocally.

The adjusting device 60 forms a chain of detectors linked together with pairs of arms. Arms are constrained to keep parallel to each other, or the second plurality of hinges 63 are constrained to stay at a constant distance to the longitudinal direction X.

A force F can be applied to the last detector along the longitudinal direction X to move all the detectors together along this longitudinal direction X.

Then, the detectors move to stay equidistant to each other with a gap G along the longitudinal direction X.

Such first adjusting device may be applied in any direction to groups of detectors of the embodiments of the invention to reduce the number of actuators to be used.

Figures 11a, lib and lie are longitudinal views of an example of a second adjusting device 70 in packed, intermediate and expanded configurations, said second adjusting device 70 being at least adapted to the sixth and seventh embodiments of the invention.

These figures show four detectors and the adjusting device 70 comprises: - a first plurality of hinges 62, each hinge 62 of this first plurality being attached to a lower part of a detector ,

- a second plurality of hinges 63, each hinge 63 of this second plurality being attached to an upper part of a detector, and - a plurality of arms 61 linking successively a hinge 62 of the first plurality of hinges to a hinge 63 of the second plurality of hinge, or reciprocally.

The adjusting device 60 forms a chain of detectors, each detector being linked with one arm to another detector.

Arms are constrained to keep parallel to each other, or the second plurality of hinges 63 are constrained to stay at a constant distance to the longitudinal direction X. A force F can be applied to the last detector along the longitudinal direction X to move all the detectors together along this longitudinal direction X and to simultaneously tilt the detectors.

On figure lie, the arms 61 are horizontal. The longitudinal dimension of the group of detectors is considerably increased, and each detector is overlapping a following detector, so that there is no free space in a transversal direction. Most of the radiations should be detected, in the packed configuration of figure 11a and the expanded configuration of figure lie.

Claims

1. An imaging device for positron emission tomography (TEP), comprising: - an examination volume adapted for receiving a body to be imaged emitting a radiation, the examination volume extending along a longitudinal direction (X) , having a lateral side along and around this longitudinal direction (X) and two end sides at each end in this longitudinal direction (X) ,

- detectors, each detector comprising at least a semiconductor material and electrodes adapted to determine a three-dimensional position of a radiation interaction within the semiconductor material of each detector, - a lateral detection module comprising a first group of said detectors, disposed along said longitudinal direction (X) on the lateral side of the examination volume, and having a longitudinal dimension (LD) along said longitudinal direction (X) , the imaging device being characterized in that it further comprises an adjusting device adapted to expand the lateral detection module in said longitudinal direction (X) between a packed configuration and an expanded configuration and wherein : - in the packed configuration, said longitudinal dimension (LD) is higher than dimensions of the examination volume along both transversal directions (Y, Z), said transversal directions being perpendicular to the longitudinal direction (X) , and - in the expanded configuration, said longitudinal dimension (LD) is higher than the longitudinal dimension (LD) in the packed configuration.

2. An imaging device according to claim 1, wherein the adjusting device supports the detectors of the first group and is adapted to move the detectors of the first group so that said adjusting device expands the lateral detection module .

3. An imaging device according to claim 1 or claim 2, wherein the detectors of the first group are more spaced from each other along the longitudinal direction (X) in the expanded configuration than in the packed configuration.

4. An imaging device according to any of the claims 1 to 3, wherein the adjusting device is adapted to have the detectors of the first group organised along at least one layer and regularly spaced from each other in the longitudinal direction (X), and wherein:

- in the packed configuration, said detectors are close to each other in the longitudinal direction (X) , and

- in the expanded configuration, said detectors are spaced from each other by a gap (G) in the longitudinal direction (X) .

5. An imaging device according to any of the claims 1 to 3, wherein the adjusting device is adapted to have the detectors of the first group organised along at least two layers, a fist layer and a second layer, and regularly spaced from each other in the longitudinal direction (X) , and wherein:

- in the packed configuration, the detectors of at least one layer are close to each other in said longitudinal direction (X) , and

- in the expanded configuration, said detectors of the first layer are spaced from each other by a first gap

(Gl) along the longitudinal direction (X), the detectors of the second layer are spaced from each other by a second gap (G2) along the longitudinal direction (X), each detector of the second layer transversally covering a corresponding first gap (Gl), and each detector of the first layer transversally covering a corresponding second gap (G2) .

6. An imaging device according to any of the claims 1 to 3, wherein the adjusting device is adapted to have the detectors of the first group regularly spaced from each other in the longitudinal direction (X), and wherein:

- in the packed configuration, said detectors of the first group have an initial position, and

- in the expanded configuration, said detectors are tilted by an angle (A) relative to said initial position of the detectors in the packed configuration.

7. An imaging device according to claim 6, wherein the adjusting device is adapted so that, in the packed configuration, the detectors are close to each other along the longitudinal direction (X) .

8. An imaging device according to claim 6 or claim 7, wherein the adjusting device is adapted so that in the expanded configuration, the detectors are spaced from each other by a gap (G) in the longitudinal direction (X) .

9. An imaging device according to claim 6 or claim 7, wherein the adjusting device is adapted to hold a gap (G) minimal and a tilted detector is close to its neighbour detectors in the longitudinal direction (X) .

10. An imaging device according to any of the claims 6 to 9, wherein the adjusting device comprises for each detector of the first group: - a translation actuator to translate said detector according the longitudinal direction (X) , and

- a rotation actuator to rotate said detector.

11. An imaging device according to any of the claims 6 to 9, wherein the adjusting device comprises:

- connecting rods adapted to link a lower part of a detector to an upper part of another detector, forming a chain of detectors of the first group, and

- a translation actuator adapted to translate an end detector of said chain of detectors.

12. An imaging device according to any of the claims 1 to 11, wherein said imaging device further comprises end detection modules, each end detection module:

- comprising a second group of detectors, and - disposed on a respective end side of the examination volume.

13. An imaging device according to claim 12, wherein the detectors of the lateral detection module and the end detection modules are positioned in the packed configuration, so that a radiation emitted in the examination volume in any direction is passing through at least one of said detectors.

14. An imaging device according to claim 13, wherein the detectors of the lateral detection module and the end detection modules are positioned in the expanded configuration, so that a radiation emitted in the examination volume in any direction is passing through at least one of said detectors.

15. An imaging device according to any of the claims 1 to 14, further comprising a central unit receiving signals from the detectors, wherein the central unit is adapted to: - detect events of radiation interaction inside the detectors, the events being characterised by parameters, the parameters being at least one or a combination of the date of each event, and the position of each event,

- define a pair of events belonging to two substantially opposite detectors relative to the examination volume, and thanks to grouping conditions, and - determine lines in the examination volume representing the radiation at the origin of each pair of events .

16. An imaging device according to any of the claims 1 to 15, wherein the lateral detection module (30) has a transversal dimension (TD_Y, TD_Z) along one of the transversal directions (Y, Z), and wherein the adjusting device is adapted to adjust the lateral detection module (30) at least said in one of the transversal directions between a retracted configuration and an enlarged configuration, and wherein in the enlarged configuration said transversal dimension is higher than in the retracted configuration .

17. An imaging device according to any of the claims 1 to 16, wherein the semiconductor material is in the list of CdTe, or CdZnTe, or Ge, or Hgl2, or Si, or TlBr material.

18. An imaging device according to any of the claims 1 to 17, wherein the lateral detection module has, in a cross section of the imaging device perpendicular to the longitudinal direction (X) , a shape in the list of a substantially rectangular shape, a substantially polygonal shape, and a substantially circular shape.

19. An imaging device for positron emission tomography (TEP), comprising:

- detectors adapted to determine a position of a radiation interaction within each detector,

- a detection module comprising a group of said detectors, disposed along a direction, and having a dimension along said direction, the imaging device being characterized in that it further comprises an adjusting device adapted to expand the detection module in said direction between a packed configuration and an expanded configuration, and wherein:

- in the packed configuration, said detectors of said group have an initial position, and

20. An imaging device according to claim 19, wherein the adjusting device supports the detectors of said group and is adapted to move the detectors of said group so that the adjusting device expands the detection module.

21. An imaging device according to claim 19 or claim 20, wherein the detectors of said group are more spaced from each other along the direction in the expanded configuration than in the packed configuration.

22. An imaging device according to any of the claims 19 to 21, wherein the adjusting device is adapted so that, in the packed configuration, the detectors are close to each other along the direction.

23. An imaging device according to any of the claims 19 to 22, wherein the adjusting device comprises for each detector of said group:

- a translation actuator to translate said detector along said direction, and

- a rotation actuator to rotate said detector.

24. An imaging device according to any of the claims 19 to 22, wherein the adjusting device comprises: - connecting rods adapted to link a lower part of a detector to an upper part of another detector, forming a chain of detectors of said group, and

25. An imaging device according to any of the claims 19 to 24, wherein each detector comprise at least a semiconductor material and electrodes adapted to determine a three-dimensional position of the radiation interaction within the semiconductor material of the detector.

26. An imaging device according to claim 25, wherein the semiconductor material is in the list of CdTe, or CdZnTe, or Ge, or Hgl2, or Si, or TlBr material.