EP3987314A1 - Procede d'imagerie utilisant conjointement une reconstruction pet et une reconstruction compton, de preference en compton 3d - Google Patents
Procede d'imagerie utilisant conjointement une reconstruction pet et une reconstruction compton, de preference en compton 3dInfo
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- EP3987314A1 EP3987314A1 EP20737365.5A EP20737365A EP3987314A1 EP 3987314 A1 EP3987314 A1 EP 3987314A1 EP 20737365 A EP20737365 A EP 20737365A EP 3987314 A1 EP3987314 A1 EP 3987314A1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/20—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
- G01N23/20066—Measuring inelastic scatter of gamma rays, e.g. Compton effect
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- G—PHYSICS
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- G01N2223/40—Imaging
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Definitions
- TITLE IMAGING PROCESS USING JOINTLY A PET RECONSTRUCTION AND A COMPTON RECONSTRUCTION, OF
- the present application relates to the field of imaging and more particularly to the imaging of sources of gamma rays.
- the invention relates to a gamma ray detection imaging system and methods combining Compton camera type detection and Positron Emission Tomography (PET) type coincidence detection.
- PET Positron Emission Tomography
- the invention further relates to the use of the imaging and / or detection system in the fields in particular of astronomy, industry, in particular nuclear, and the medical or veterinary field.
- the imaging of gamma ray sources (the energy of which is generally greater than 30 KeV) is carried out essentially for medical diagnostic purposes around three techniques: PET, SPECT and the Compton Camera.
- SPECT is based on scintigraphy and makes it possible to produce three-dimensional images and reconstructions of organs and their metabolism by means of a set of gamma cameras rotating around a patient.
- the SPECT can use several gamma ray energies, for example less than or equal to 300 KeV, but the lead collimator which allows to know the trajectory of the rays absorbs more than 99%.
- PET generally uses a ring of segmented detectors.
- radiopharmaceutical compounds emitting positrons. These give rise to a pair of 51 1 keV photons of which it is possible to locate the emission source thanks to their simultaneous detection on the ring of detectors (coincidence detection).
- the radioelements used for PET have a short life and are therefore often expensive.
- PET imaging is functional imaging that is very attractive to guide medical intervention with an image that clearly indicates where the source of the radiation that is observed is located. This is particularly the case in Oncology where the emission of rays is concentrated on tumors and makes it possible to differentiate the latter from healthy tissues.
- PET imaging is also widely used in preclinical imaging on rats or mice to observe biological processes in vivo.
- PET imaging is also the imaging technology which makes it possible to obtain the most precise images currently (signal / noise ratio and angular resolution), for energetic gamma radiation of 51 1 keV.
- one of the key points in PET imaging is the precise measurement of the time of flight of 51 1 keV photons from their place of emission. This measurement of time of flight is all the better as the thickness of the scintillator traversed is thin.
- a large part of the photons is not detected correctly because the probability of detection increases with the thickness of the scintillator crossed.
- PET imagers usually consist of a complete ring around the patient (or any object) with a diameter of about 80cm for a width of over 20cm and a scintillator thickness of 20mm.
- This ring configuration is imposed by the very small field of view of PET. Indeed, only the interactions in coincidence between two detectors are observed there, which imposes a reduced solid angle for each event in ring.
- This configuration makes their use difficult to envisage in the context of a surgical operation.
- PET scanners are very expensive (around two million euros) due to the volume of detectors required.
- the doses of radioactivity injected into the mice are very high, which can disrupt the processes. physiological that one wishes to observe.
- it would be advantageous to be able to drastically reduce the injected dose for example a dose less than or equal to 1 MBq in the vicinity of the organ to be treated.
- the Compton camera like the SPECT, makes it possible to make an image regardless of the energy of the gamma radiation, but unlike the SPECT, all the photons can contribute to the image.
- the applications of the Compton camera are still often limited today, in particular because of its cost, the high level of noise on the images and the difficulty of obtaining precise reconstructions.
- scintillating crystals are used to produce an image of gamma radiation sources, one comes up against the probabilistic nature of the gamma photon / matter interaction. We notice essentially two effects.
- the first effect resides in the fact that the gamma photon can be absorbed at any depth on its propagation path (“Depth of Interaction” effect according to the English terminology).
- the second effect is that all current imaging systems (pixel matrix or Anger camera) are based on the postulate that the place where the maximum light emission takes place is the place where the gamma photon has been detected. Because of the Compton deviation, this assumption is correct as long as we consider the mean value of a large number of events.
- the error on the position, may be of several millimeters. The solution adopted is then to reject the events for which the energy deposited is not correct.
- the arrival time of the first photons on each pixel makes it possible to determine the position of the disc (and therefore of the cone) of the non-scattered photons, which makes it possible to improve the precision of the l estimation of the position (in particular in "depth", that is to say parallel to the imaging axis on which the PET detectors are aligned).
- the use of monolithic crystals for PET scanners has multiple advantages, such as easy access to depth measurement, reduced cost and a potential for high spatial resolution, in particular by using information relating to the depth. distribution of events over time ("temporal imagery", as mentioned above).
- the fastest scintillating crystals today are Lanthanum halides, such as CeBr3 or LaBr3: This emits up to 4 times more photons during the first nanosecond than LYSO: This is often used in the field today. .
- these lanthanum halides are the best candidates for temporal imaging.
- these crystals are very delicate to use because they are extremely sensitive to atmospheric conditions (especially hydrometry), which restricts their use in the form of monolithic crystals.
- the use of monolithic crystals comes up against a paradox with regard to the measurement of the time of arrival of photons.
- the measurement of the arrival time of the first photons should be more precise in a monolithic crystal than in a detector in the form of a matrix (ie, pixelated) of scintillating crystals, in particular due to the absence of optical deviation from the place of emission.
- a matrix ie, pixelated
- the first photon detected by a given pixel is very likely to have undergone multiple reflections on the lateral faces of the crystal before being collected by the photodetector and the information on the real time d. The program will therefore be imprecise, if not totally lost.
- the present application also proposes solutions to this paradoxical problem.
- the spatial resolution, signal / noise ratio of PET imagers are limited by many factors: the thermalization of the positron, the non-collinearity of 51 1 keV photons, the structure of the detectors, the large proportion of recorded events due to fortuitous coincidences, to diffused pairs. These unwanted events affect the measurement of activity and increase noise in the reconstructed images.
- the time-of-flight information provides improvements but is limited by the precision of the time measurement. Theoretical studies show that if we could obtain a flight time of 30 pico seconds, there would be no need for sophisticated reconstruction of the image, it would be perfectly clear.
- the flight time is not very relevant today on small scanners (brain for example) or small animal imaging, the scanner being less than 30 centimeters in diameter.
- the diameter of the PET rings being the limiting factor for very large fields imaging (horses, ...)
- the best current PET scanners have a flight time of 240 picoseconds FWHM which corresponds to an average length of LOR of six centimeters compared to eighty centimeters without flight time.
- PET imaging which has fewer drawbacks than the prior art, in terms of acquisition time, speed of convergence of the algorithms, quality of the reconstructed images, and possibilities of small field imaging (small animal type, brain %) and very large field (horses, ).
- the present invention provides a device, system and method for PET and COMPTON 3D imaging making it possible to overcome at least part of the drawbacks of the prior art.
- the "PET and Compton” or conversely “Compton and PET” imaging method denotes an imaging method using jointly a PET reconstruction and a Compton 3D reconstruction.
- the invention relates to a PET and Compton imaging method implemented by a device comprising at least one facing PET module, characterized in that it comprises at least one Compton cameras producing at least one. Compton view, the acquisition fields of said PET and Compton views having at least one overlap zone covering the object to be imaged.
- Such an imaging method coupling the PET and at least one Compton camera allows the Compton image to be able to truncate the LORs (response lines) of the PET imaging with accuracy better than 2 cm.
- said device allows the following steps to be carried out:
- the invention also relates to a PET and Compton imaging method implemented by a device comprising at least one Compton camera producing at least one Compton view from at least two positions, preferably three, among three known positions distributed over at least one of the three axes (X, Y, Z) of a trihedron, the acquisition fields of said views having at least one overlap zone covering the object to be imaged .
- a device comprising at least one Compton camera producing at least one Compton view from at least two positions, preferably three, among three known positions distributed over at least one of the three axes (X, Y, Z) of a trihedron, the acquisition fields of said views having at least one overlap zone covering the object to be imaged .
- said PET and Compton imaging method comprises an additional step of filtering the LORs passing through a dense zone by considering the probability of association of a LOR with said dense zone.
- said PET and Compton imaging method comprises at least one Compton multi-capture camera.
- said PET and Compton imaging method contains a PET and Compton tomographic reconstruction method taking into account at least three separate Compton views locating the object to be imaged, defining the contours of the dense zone and guiding LOR segmentation.
- said PET and Compton imaging process contains a PET and Compton reconstruction method in which only the intersections of cones from 3 different views locating the object to be imaged, defining the contours of dense area and guiding LOR segmentation.
- said PET and Compton imaging method contains an additional step in which the location of the site of emission of the photons is determined by the intersection between a Compton cone an LOR in the case for example where the radioelement emits a gamma photon in coincidence with the emission of a positron (e.g. 22Na, 41 Sc, etc ).
- a positron e.g. 22Na, 41 Sc, etc .
- said PET and Compton imaging method contains an additional step in which the location of the site of emission of the photons is determined for the radionuclides which are emitters of at least two types of radiation, in particular a positron and a gamma ray, by the intersection between a Compton cone a LOR.
- said PET and Compton imaging method is capable of measuring the time of flight of the photon in coincidence with the PET emission.
- said PET and Compton imaging process contains a Compton analysis process, used in the case where the intensity of the source is identical between several views, to filter the parasitic events for which said intensity of the source does not satisfy the law of the inverse of squared distances, not varying like 1 / d 2 on each of the views, d being the distance from the source to the camera on each of the views.
- the invention further relates to a PET and Compton imager comprising at least one Compton camera capable of producing at least one Compton view, at least two PET cameras capable of performing coincident acquisitions for the setting. implementation of the method according to the features described above.
- said imager comprises hybrid PET and Compton cameras.
- the Compton camera has a temporal resolution which allows it to measure the time of flight from the place of emission (case of radionuclides generating the emission in any way of 3 photons).
- the intersection of the Compton cone with the LOR linked to the decay of the positron gives two straight line segments.
- the times of flight measured on the two coinciding detectors and on the Compton camera then often make it possible to exclude one of the two line segments on the basis of a single discrimination based on the times of flight (TOF).
- said imager is coupled to a third imaging modality (CT-Scan or MRI ...) facilitating the fusion of images for a better diagnosis.
- CT-Scan or MRI
- At least one of the Compton cameras of said imager is mounted on at least one device provided with at least one motor which can successively and / or simultaneously move in all directions in space and be oriented along Euler angles, either in automatic mode or in manual mode.
- the invention also relates to the use of said PET and Compton imager according to at least one of the particularities described in the health field, in the veterinary field and in industry.
- the invention relates to the use of said PET and Compton imager to produce images with at least one tracer capable of generating photons of different energies.
- the invention provides imaging improvement kits, to transform PET imagers, CT-Scan, PET / CT and / or PET / MRI imagers, MRI imagers compatible with the process. according to the characteristics described.
- Said Enhancement Kit contains a device capable of providing at least one view, preferably three separate Compton views in the three directions of space.
- said improvement kit further contains a reconstruction module implementing a reconstruction algorithm combining the acquisitions of the PET imager and of said Compton three-view device for the implementation of the method according to the particularities described.
- said improvement kit contains a reconstruction module implementing a reconstruction algorithm combining the acquisitions of the imager and of said device with three Compton views and two PET cameras for the implementation of the method according to the characteristics described.
- said improvement kit contains a reconstruction module implementing a reconstruction algorithm combining the acquisitions of the MRI imager and of said device with three Compton views and two PET cameras for the implementation of the process according to the features described.
- FIG. 1 is a schematic representation of classic Compton imaging of the prior art
- FIG. 9 a is a schematic representation of two cones in two separate views.
- FIG. 9. b is the schematic representation of the area of intersection of these two cones and of its volume.
- FIG. 9.c] and FIG. 9.d] are the images of two sources ( 22 Na and 1 37 Cs) detected by two distinct views according to one embodiment of the invention (reconstructed image (MLM / MLEM) from said two views according to the X axis [Fig. 9.c], along the Z axis [Fig. 9.d]: - I Fig. 10] is a schematic representation of three Compton cameras distributed over the three axes (X, Y, Z) of a trihedron centered in O, o [Fig. 11.a] is a schematic representation of three cones in three distinct views. o [Fig. 11. b] is a schematic representation of the area of intersection of said three cones and of its volume. o The [Fig.
- FIG. 12. a represents the XZ section obtained by “classical” 3D reconstruction by considering all the intersections between Compton cones. The position of the 2 sources is clearly visible but the image shows many artefacts.
- o represents the same section XZ obtained by reconstruction according to the invention using only the multi-view intersections and clearly showing the position of the two sources and the virtual disappearance of the artefacts.
- FIG. 13 is a schematic representation of a double emission embodiment of the invention (the 22 Na source simultaneously emits gamma photons of 1, 3 MeV and b + which generate photons of 511 keV) which illustrates a device containing two PET cameras each detecting a 511 keV photon and a Compton camera detecting the 1.3 MeV photon for an implementation of the method of the invention.
- - [Fig. 14] is a schematic representation of an embodiment of the invention and illustrates a device containing two PET cameras each detecting a 511 keV photon and three Compton cameras locating a dense zone centered on a trihedron whose origin is the point of departure of the source which coincides with the point of intersection of the Compton cones.
- the present invention relates to an imaging system and method jointly using a PET-type coincidence reconstruction and a single-photonic reconstruction at the same energy (511 keV) of the Compton 3D type.
- a device comprising at least one PET type coincidence detection module.
- TOF Time Of Flight
- said device further comprises at least one Compton camera producing at least one Compton view, the acquisition fields of said views having at least one overlap zone covering the object to be imaged.
- said device comprises one or more Compton cameras producing at least one Compton view from at least one position among three known positions distributed over at least one of the three axes (X, Y, Z) of a trihedron ([Fig. 14]) of which the zone to be imaged is at the origin, the acquisition fields of said views having at least one overlap zone covering the object to be imaged.
- the desired objective is to locate and delimit the dense areas with the number of views acquired, and required to apply the 3D Compton reconstruction taught in an application filed the same day by the same inventor.
- the invention relates to a Compton imaging method using one or more Compton cameras.
- Said Compton cameras produce at least three views [Fig. 10], [Fig. 1 1 .c] (containing the capture centers CC1, CC2, CC3 [Fig. 10.]) from three known positions distributed over the three axes (X, Y, Z) each passing through one of the capture centers d one of the Compton cameras.
- the implementation of said method allows the 3D reconstruction of the image of an object from a minimum of views, preferably three.
- Such an imaging process coupling PET and at least one Compton camera allows the Compton image to be able to truncate the LORs (response lines) of PET imaging with accuracy better than 2cm.
- An advantage of using the method of the present invention is to make it possible to reduce the number of views necessary for the reconstruction of the image which imposes constraints (time, dose, cost, etc.). For example, multiplying the number of views has a cost, either in pause time if we have to move the camera to obtain enough views, or in equipment cost if using equipment taking several views simultaneously.
- the implementation of the method of the present invention makes it possible to combine the advantages of the detection mode of Compton cameras, of the original and novel method of selection of the photons required to reconstruct 3D image.
- the method of the present invention comprises a 3D Compton reconstruction step requiring less than 10 photons / voxels to reconstruct the image. This is in part due to the finesse of our photon selection method which, by reducing positional uncertainty by acquisition, improves the location accuracy of reconstructive gamma photons.
- said method allows with very few photons in comparison with current conventional tomographic imagers, to reconstruct 3D images of better or at least equivalent quality.
- said method allows with very few photons in comparison with current conventional tomographic imagers, to reconstruct 3D images of better or at least equivalent quality.
- the method of the present invention comprises a step of 2D (or even 3D) Compton reconstruction requiring less than 10 photons / voxels to reconstruct the image. This is in part due to the finesse of our photon selection method which improves the localization accuracy of reconstructing gamma photons for a better image with fewer hits compared to conventional imagers of the same type.
- a 2D image from a single fixed position, that is to say a single acquisition (planar mode) or 3D with a second position of acquisition.
- a Compton 3D reconstruction is carried out from three views, each sampling one of the three directions of space.
- 11 and I2 are the two points of interaction and the direction of diffusion is given by the line d (11 I2) passing through 11 and I2.
- the point of absorption I2 apex of the Compton cone is the reference point locating the position of one of the views on one of the axes, the three axes forming a trihedron whose origin O [Fig. 10.] is the point of intersection of said axes.
- the 1 D, 2D, 3D modes described below must be understood as being the number of spatial directions of view (s).
- two gamma photons coming from the same source are detected by a Compton camera along one of the axes of the trihedron (1 D mode).
- a Compton camera along one of the axes of the trihedron (1 D mode).
- the intersection volumes of the cones are quite large. For example, 2240 cm3 for the intersection volume following a view [Fig. 8.c]
- the two gamma photons are detected either by two different Compton cameras, each along one of the three axes of the trihedron, or by a single Compton camera capable of successively producing two views, each along two different axes of the trihedron ([Fig. 9.a]; [Fig. 9 b]).
- Such an arrangement of Compton cameras makes it possible to have two separate shots along two axes of a plane passing through the object to be imaged, the details of the object to be imaged are better circumscribed, better defined and better resolved. than in 1 D mode.
- One of the advantages of this embodiment is to highlight three problems, an artefact line along the axis of view, the image of the point source is not spherical and has a distortion along the same axes as the artifact, the image computation time is very long.
- An advantage of this embodiment is that it makes it possible to position the object correctly with a very low number of photons (only ten per voxel against one 50 for an image on at least one single view, for example). According to another particularity, only the intersections of cones originating from the X and Y views in the reconstruction are considered. All XX and YY intersections are eliminated, which has the effect of improving the source location precision, accelerating the convergence of the algorithm, and reducing artifacts due to phantom sources.
- an observation along the Z axis further reduces the artifacts. Indeed, with this complete observation there is no longer a particular direction according to a view and the artifact is much less marked.
- one solution offered by the method is, to limit this problem, to observe the system along the Z axis.
- three gamma photons from the same source are detected, either by three different Compton cameras, each along one of the three axes of the trihedron ([Fig. 10]; [Fig. 12]), or by a single Compton camera capable of producing three views, each along three different axes of the trihedron, or by two cameras, one producing a view along one of the axes of the trihedron and the other successively producing the other two views respectively on the other two axes of the trihedron.
- the purpose of these different Compton camera layout options is to cover all the possible configurations to ultimately make it possible to obtain three distinct shots along the three axes of a trihedron.
- the views can be acquired, either simultaneously by three separate Compton cameras, or sequentially by a movement of at least one Compton camera on said 3 axes X, Y and Z of the trihedron.
- the place of emission (S) of the detected photon coincides with the point of intersection (O) of the X, Y and Z origin axes of the trihedron [Fig. 10.].
- said trihedron is a trihedron with orthogonal X, Y and Z axes defining three directions of space. Three views following the three directions of space constitute optimal observation conditions for a given source located at the origin of said trihedron, If the field of view is transparent to radiation, the views above and below are equivalent in information, and are those where the axes joining the source to the camera constitute an orthogonal trihedron.
- the source is simultaneously observed along the 3 axes of the trihedron and only the intersections which include the three viewing angles are considered, in the most general case there are only 8 possible point solutions for the source in space, 8 restricted zones if the cones have a certain thickness due to uncertainties [Fig. 9. a]
- the method contains a Compton reconstruction method in which only the intersections of cones from different views are retained.
- One of the advantages being, for example, the improvement of the source localization precision which allows a better reduction of the phantom source artefacts in the reconstructed image. If we compare 2 intersections of cones in 3D mode containing the same source but corresponding to two different groups of photons, the probability that the “phantom” solutions coincide is very low. The reconstruction technique will therefore converge with a very limited number of photons. (To a lesser extent this is also the case when we consider all the intersections).
- the voxel being the unit of volume image, the geometry of which can be varied as desired in a nonlimiting manner (cubic, cylindrical, spherical, etc.).
- Another advantage of imposing the presence of cones coming from the 3 views to consider an intersection zone as valid, is that this will considerably accelerate the convergence of the back projection algorithm by removing the irrelevant zones to locate the source.
- Another advantage is that this reduction of uncertainties leads to reducing the dimensions of the task which contains the image of the source. With three views we have a better angular resolution of the Compton camera.
- said Compton imaging method further contains a Compton scanning process, used in the case where the intensity of the source is identical between several views, to filter the parasitic events for which said intensity of the source does not satisfy the law of the inverse of squared distances, not varying as 1 / d2 on each of the views, d being the distance from the source to the camera on each of the views.
- a Compton scanning process used in the case where the intensity of the source is identical between several views, to filter the parasitic events for which said intensity of the source does not satisfy the law of the inverse of squared distances, not varying as 1 / d2 on each of the views, d being the distance from the source to the camera on each of the views.
- the views of the source are simultaneous, in particular if the absorption of the radiation is negligible, it is possible in most cases to determine which of the two solutions is the correct one because the number of photons detected by each camera should vary as 1 / d2 depending on the distance from the source, which is not generally verified for the "phantom" source.
- the present invention further relates to a Compton imager comprising at least one Compton camera, capable of producing at least three successive or simultaneous views and implementing the Compton imaging method according to the particularities described above.
- Said dense area can be located using one Compton view, two Compton views, preferably at least three Compton views, the accuracy of localization along the axis of sight of the Compton camera being low. Additionally, with at least 3 Compton views, artifacts are reduced, contours are better defined, and Compton 3D reconstruction is faster and much better.
- said device comprises at least one Compton multi-capture camera (using at least two positions of Compton imagery captures taken from at least two different locations).
- This embodiment makes it easier to define a desired geometry to delimit the localized dense zone. For example, for a view produced with a binocular Compton camera (two capture heads), it is easier to define cylindrical geometries for the voxels of said dense zones located by these binocular Compton cameras. This improves the quality of the reconstructed images.
- said device is able to locate a dense zone using the intersection of the cones from various distinct views and able to define the contour of said dense zone ([Fig. 14]).
- said device is able to quantify the activity present in said dense zone by counting the number of cones and thus to estimate the distribution of the radio tracer in said dense zone.
- said device is able to perform coincident detections by the PET cameras and to associate with each one a response line (LOR) ([Fig.13]).
- LOR response line
- the 3D Compton reconstruction described above is used to reconstruct the 3D image of the localized dense zone and then calculate a 3D detection probability map from the image.
- the 3D Compton reconstruction gives a 3D density map of the valid interactions (multi-views for example) resulting from the detected Compton events. This map is used to calculate voxel / voxel a probability map of the presence of gamma emission in this voxel.
- the filtering is performed by assigning to each segment of the LOR PET crossing the Compton voxel the associated probability. This filtering process is similar to that used in Time of Flight type PET scanners. In these scanners for each LOR we define a source position probability distribution as a function of the relative arrival times of the photons on the two coinciding detectors.
- said device is able to select a beam on the basis of a plurality of LORs and of the zone of intersection between said beam and said dense zone.
- the spatial resolution of a Compton camera is an angular resolution. The closer you get to the detector, the smaller the spatial resolution. In the case of imaging specific to an organ, for example the brain, if it is possible to approach the Compton camera at 10cm from the organ, the spatial resolution of the Compton image will then be 3mm, which would be equivalent to a TOF of 10 ps [00112]
- the PET and Compton imaging process comprises an additional step of electronically filtering the LORs passing through a dense zone by considering the probability of association of an LOR with said dense zone.
- said device is able to segment LORs of the beam passing through said dense zone.
- the source By delimiting said dense zone where there is a high concentration of activity, the source is located. Then, by segmenting the LORs crossing said dense zone along its contours, the uncertainty about the real source position is reduced. This step of the process is decisive in optimizing the position of the source, makes it possible to produce a very precise local image, to accelerate the reconstruction algorithms, to reduce the dose required for imaging.
- the time-of-flight information is useful for improving the image quality, the acquisition time, reducing the dose, etc.
- the best current PET imagers have a flight time of 240 ps FWHM which corresponds to an average LOR length of 6 cm. This length is great compared to the intrinsic spatial resolution of scanners of the order of three or four (3 ⁇ 4) millimeters (mm). As a result, it is not possible to obtain an image directly by positioning the line segments in space. You have to go through a sinogram and a complex reconstruction process. However, the 6 cm section considerably improves the spatial resolution of the reconstructed images.
- the LOR segmentation method of the present invention based on the contours of the dense zone localized by Compton cameras makes it possible to obtain LORs of 1 cm which is impossible for current imagers and contributes to reducing artefacts and improving resolution. spatial. Indeed, an essential contribution of Compton cameras to the device is to allow the production of a precise 3D Compton image of dense zones of sizes of approximately 1 cm for a point source and their localization. Also, the temporal resolution of our cameras ( ⁇ 250 ps) facilitates the implementation of the method of the present invention because it is possible to obtain a measurement of Time of flight between the emission and the Compton camera in the event that an event is detected by the PET.
- a single Compton sight is required to locate the source.
- the LORs from the PET scanner are intersected with a "two-dimensional" Compton image acquired from a single Compton view.
- the position of the source will be precise (at 1 cm for example) in the direction perpendicular to the sight of the camera (X, Y) and degenerate along the sight axis (Z axis).
- the source in the case where the source emits a gamma photon at the same time as a positron ( 22 Na, 41 Sc, etc.) only one Compton view is necessary to locate the source .
- the two 51 1 keV photons having been detected jointly by the PET cameras and the third photon detected by the Compton camera alone in the same time window.
- This embodiment is suitable for radionuclides which simultaneously emit two types of radiation, betas plus (b + ) and gamma (y), for example 22 Na, 41 Sc etc.
- betas plus (b + ) and gamma (y) for example 22 Na, 41 Sc etc.
- b + betas plus
- gamma (y) for example 22 Na, 41 Sc etc.
- two photons of 51 1 keV are detected and a third of different energy (1.3 MeV for 22 Na for example) also emitted during the disintegration of said radionuclide.
- the very good temporal resolution ( ⁇ 250 ps) of certain Compton cameras, equivalent to that of PET cameras, allows the detection of the three events by measuring the flight times between source / PET detectors but also source / camera.
- the 3D localization of a source can be achieved by at least three separate views.
- the two 51 1 keV photons are jointly detected by the PET cameras and the third photon detected by the Compton camera in the same time window.
- the intersection between the Compton cone from the Compton camera and the LOR joining the two PET cameras gives the place emission of the three photons detected.
- the three vents all coming from the same atom also give here a quasi-deterministic localization of said place of emission (two zones of cone / LOR intersections).
- the measurement of the impact times of the photons on the two PET detectors and on the Compton camera makes it possible to estimate the source / detector distance on the LOR and on the cone. We must therefore intersect a slice of a cone for the Compton with a line segment for the LOR. In this mode, a single Compton camera is sufficient. In this mode we can also make a Compton image with the photon co-emitted with the beta plus.
- the gamma co-emitted with beta-plus. being emitted in all directions of space, it is possible, by energy windowing of the PET cameras, centered on 1, 3 MeV, to filter the 51 1 KeV and we thus have, at the end of said windowing three views at 1.3 MeV, the possibility of performing an imaging at 1.3 MeV of the source.
- said method contains an additional step in which the location of the site of emission of the photons is determined for the radionuclides which are emitters of at least two types of radiation simultaneously (for example 22 Na , 41 Sc) by the intersection between a Compton cone an LOR.
- said device contains a Compton camera capable of measuring the time of flight of the photon in coincidence with the PET emission.
- the intersection of the two objects will in the general case give two LOR segments 1 cm in length and 3-4 mm in diameter. Furthermore, since the arrival time of the third photon on the Compton camera is available, it is possible in most cases to exclude one of the two positions due to the TOF, either Compton or PET. In the case where one of the two positions can be excluded, there is a deterministic image without reconstruction of the emission zone. Two or three Events of this type by Voxel are sufficient to obtain a perfect image of the object and allow a marked reduction in the injected dose for a medical application for example.
- the LOR segmentation step of the method of the present invention by relying on the contour delimiting the dense zones makes it possible to obtain LORs of approximately 1 cm.
- the advantages of this embodiment are many, some of which are the significant reduction in the number of fortuitous coincidences, the acceleration of the reconstruction, the improvement of the image quality, also the cost of the device of the present invention compared to with classic PET and TEP TOF.
- this embodiment of the invention accelerates the convergence of the reconstruction algorithm and improves the quality of the reconstructed image.
- the three views are acquired from three known positions distributed over at least one of the three axes (X, Y, Z) of a trihedron ([Fig. 14], the fields of acquisition of said views having at least one overlap zone covering the object to be imaged, the objective here being, using the three Compton views, to locate the dense zone.
- said device contains a method allowing it to make acquisitions according to three distinct Compton views.
- one of the methods would be to insert at least two Compton heads at 90 ° to each other inside the ring of a PET scanner, the third head being located in the axis of the ring outside the usual PET field of view, the three heads able to form a direct trihedron centered on the area to be imaged [Fig. 14]
- Another method would be to have the three Compton heads at 120 ° to each other outside the ring of the PET each being inclined and targeting the geometric center of the ring in order to produce a trihedron which samples all the axes of said trihedron.
- the present invention makes a Kit available to users allowing them to increase the performance of an existing PET scanner by performing a retrofit and comprising at least one Compton camera.
- the number of said Compton cameras in the Kit varying according to the nature of the desired assembly.
- Another embodiment provides the device as described in the present invention in a single unit and comprising three Compton cameras and at least two PET cameras.
- Said device is capable of locating a dense zone and of delimiting the contour of said dense zone.
- the PET and Compton imaging method is suitable for implementing a PET and Compton tomographic reconstruction method which takes into account at least three distinct views locating the object to be imaged which contains said dense area.
- the PET and Compton imaging method contains a Compton reconstruction method in which only the intersections of cones from 3 different views are retained.
- the PET and Compton imaging method is suitable for implementing a PET and Compton tomographic reconstruction method which takes into account at least three distinct views locating the object to be imaged, defining the contours of the dense zone and guiding LOR segmentation.
- the PET and Compton imaging method contains a PET and Compton reconstruction method in which only the intersections of cones resulting from 3 different views defining the contours of dense zones guiding the segmentation are retained. of LORs.
- the PET / Compton imaging method contains a Compton analysis process, used in the case where the intensity of the source is identical between several views, to filter the parasitic events for which said said Source intensity does not satisfy the law of the inverse of squared distances, not varying as 1 / d 2 on each of the views, where d is the distance from the source to the camera on each of the views.
- a Compton analysis process used in the case where the intensity of the source is identical between several views, to filter the parasitic events for which said said Source intensity does not satisfy the law of the inverse of squared distances, not varying as 1 / d 2 on each of the views, where d is the distance from the source to the camera on each of the views.
- the invention further relates to a PET and Compton imager comprising at least one Compton camera capable of producing at least one Compton view, at least two PET cameras capable of performing coincidence acquisitions for the implementation of the method according to a of the features described.
- the PET and Compton imager of the present invention comprises hybrid PET and Compton cameras.
- the PET and Compton hybrid camera technologies are taught in application PCT / EP2019 / 062805 by the same inventor ("a first module (CP), called” hybrid ", the scintillator (2) of which comprises at least one scintillator crystal plate (P1 ), said to be fast, whose rise time at the light peak is less than 1 ns, said "hybrid” module being able to produce both Compton scattering and absorption of at least part of the gamma radiation for detection coincidence between the events in this first hybrid module (CP) and the events in a second detection module (CP, P) with which this first hybrid module (CP) therefore forms said pair of PET coincidence detection modules ”) are able to carry out both types of acquisitions (PET and Compton). Their use facilitates the compactness of the imager (a single camera instead of two or more, in certain embodiments).
- the PET and Compton imager of the present invention is coupled to a third imaging modality (CT-Scan or MRI, etc. as already mentioned in the present application) facilitating the fusion of images for better diagnosis.
- CT-Scan or MRI, etc. as already mentioned in the present application
- the coupling of the PET and Compton imager to a CT-Scan allows thanks to the CT-Scan to acquire a real mapping of the attenuation coefficients of the object to be imaged and to be able to apply during the PET and Compton reconstruction. an attenuation correction for a desired area.
- the coupling of the PET and Compton imager to an MRI type imager makes it possible, among other things, to provide a solution to the problem of small field size of MRI imagers, to better understand the operation of a organ by combining the advantages of these two functional imaging modalities, etc.
- This embodiment disclosing the coupling of the PET and Compton imager of the present invention with another imaging modality makes it possible to simultaneously produce several images with different imaging modalities in the same position.
- One advantage being, by facilitating the realization of image mergers, take advantage of the strengths of each of said modalities. Thus, it is possible to improve the quality of the interpretation of the resulting merged images, the precision of the positioning of patients in the treatment room, etc.
- At least one of said Compton cameras is mounted on at least one device provided with at least one motor which can successively and / or simultaneously move in all directions in space. and be oriented according to the angles of Euler, either in automatic mode, or in manual mode. The objective being to obtain as easily as possible whatever the geometric configuration, all the desired views of the object to be imaged.
- the invention further relates to the use of the PET and Compton imager, in the fields of health, in the veterinary field and in industry.
- the device of the present invention provides users with numerous options of use which allow the user to envisage, without additional constraints, imaging very large objects (elephants, etc.) .
- the user has other use options available for objects of small sizes for which current imagers do not offer solutions.
- the invention makes available to users several types of imaging enhancement kit, to reversibly transform imagers (for example PET imagers, CT-Scan imagers, MRI ...) making them compatible with the process according to one of the characteristics described above.
- said improvement kit contains, on the one hand, a device capable of producing at least three distinct Compton views along the three directions of space and, on the other hand, a reconstruction module implementing a reconstruction algorithm combining the acquisitions of the PET imager with those of said Compton three-view device for the implementation of the method according to the features described above.
- said improvement kit contains, on the one hand, a device capable of producing at least three distinct Compton views in the three directions of space, at least two PET cameras and, on the other hand, a reconstruction module implementing a reconstruction algorithm combining the acquisitions of the CT-Scan imager and of said Compton three-view device and two PET cameras for implementing the method according to the features described above.
- said improvement kit contains, on the one hand, a device capable of producing at least three distinct Compton views in the three directions of space, at least two PET cameras and, on the other hand, a reconstruction module implementing a reconstruction algorithm combining the acquisitions of the MRI imager with those of said device with three Compton views and two PET cameras for the implementation of the method according to the features described above.
- the present invention also provides a kit for improving existing devices using means of bringing (physical or human, depending on the risks) the Compton cameras of the object to be observe, so as to obtain a segmentation of the LORs less than or equal to 1 cm.
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US16/446,471 US20200400593A1 (en) | 2019-06-19 | 2019-06-19 | Camera compton multi-capture et procede d'imagerie |
FR2001010A FR3097655B1 (fr) | 2019-06-19 | 2020-01-31 | Procede d’imagerie utilisant conjointement une reconstruction pet et une reconstruction compton, de preference en compton 3d |
FR2001009A FR3097656B1 (fr) | 2019-06-19 | 2020-01-31 | Camera Compton et procédé d’imagerie 3D COMPTON |
PCT/EP2020/067232 WO2020254649A1 (fr) | 2019-06-19 | 2020-06-19 | Procede d'imagerie utilisant conjointement une reconstruction pet et une reconstruction compton, de preference en compton 3d |
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EP20800005.9A Pending EP3987312A1 (fr) | 2019-06-19 | 2020-06-19 | Camera compton et procede d'imagerie 3d campton |
EP20737365.5A Pending EP3987314A1 (fr) | 2019-06-19 | 2020-06-19 | Procede d'imagerie utilisant conjointement une reconstruction pet et une reconstruction compton, de preference en compton 3d |
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US7550738B1 (en) * | 2005-04-28 | 2009-06-23 | Utah State University | Nuclear material identification and localization |
US8461547B2 (en) * | 2005-04-28 | 2013-06-11 | Utah State University | Suppressed correlation method for identifying radioactive sources |
WO2010141583A2 (fr) * | 2009-06-02 | 2010-12-09 | Mayo Foundation For Medical Education And Research | Système et procédé permettant une vérification des doses en radiothérapie |
FR2997766B1 (fr) | 2012-11-08 | 2015-06-12 | Alain Iltis | Systeme et procede de detection de rayonnement gamma de type gamma camera |
FR3013125A1 (fr) | 2013-11-08 | 2015-05-15 | Alain Iltis | Procede pour ameliorer la resolution en energie de detecteurs de rayons gamma a scintillation, systeme, composant et application associes |
FR3036500B1 (fr) | 2015-05-18 | 2017-06-23 | Alain Iltis | Systeme et procede de detection de rayonnement gamma de type camera compton. |
ES2629092B1 (es) | 2015-11-04 | 2018-07-04 | Consejo Superior De Investigaciones Científicas (Csic) | Sistema de cámara compton de rayos gamma con medida de tiempo de vuelo |
JP6842694B2 (ja) * | 2017-02-20 | 2021-03-17 | 国立研究開発法人量子科学技術研究開発機構 | 部分リングpet装置及びpet装置 |
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US20220357291A1 (en) | 2022-11-10 |
FR3097656B1 (fr) | 2022-07-22 |
FR3097655A1 (fr) | 2020-12-25 |
WO2020254653A1 (fr) | 2020-12-24 |
FR3097655B1 (fr) | 2022-01-28 |
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