Radiological apparatus with multiple ionizing radiation sources and method for implementing the apparatus

Abstract

The invention relates to a radiological device comprising an ionizing radiation generator (12) and a detector (14) configured to detect the radiation emitted by the generator (12), the generator (12) and the detector (14) being opposite with respect to each other, the device (10) delimiting a useful volume (60) crossed by the ionizing radiation coming from the generator (12) and received by the detector (14), the generator (12) comprising a plurality of sources (16) distributed along a direction (18) and each emitting an ionizing radiation beam (20) substantially flat and shaped like a fan tail, the sources (16) being arranged to radiate all the useful volume (60) without translation. Another subject of the invention is a method of implementing the device (10) according to the invention, the method comprising the successive ordering of the emission of a plurality of the sources (16).

Description

TECHNICAL FIELD

[0001] The present invention relates to a radiological device and a method for implementing the device. The invention can be implemented in the medical field, in industry for carrying out non-destructive examinations and in security for detecting dangerous objects or materials. The invention also relates to a method for implementing the radiological device. The invention is particularly useful in computed tomography. The invention can also be implemented in conventional radiology without the need to move around the object to be subjected to X-ray irradiation. BACKGROUND

[0002] As is known, computed tomography, also known as scanning radiography, implements a system equipped with an x-ray tube emitting a fan-shaped collimated beam, known as "fan beam", associated with a strip-shaped detector placed opposite the beam. The tube and the detector are rotated around a table containing the patient. Each rotation, the table is advanced along the axis of rotation of the tube and the detector. Computer processing allows the reconstruction of 2D cut images or 3D volume images of the patient's anatomy. The system is known as "CT scanner", "CT" being the acronym of "Computed Tomography".

[0003] More recently, other systems have appeared with a tube emitting a cone-shaped X-ray beam, known as "cone beam", associated with a flat detector. The tube and the detector are mounted on a letter C-shaped rotating arm. These systems are known as "C-arm" or CBCT, acronym for "Cone Beam Computed Tomography". The cone-shaped shape of the beam can dispense with the translation implemented for CT scanners. For CBCT, the acquisition of data is faster since it only requires a single rotation around the patient around the assembly formed by the tube and the detector.

[0004] In systems of the CT scanner type, the flat form of the beam associated with the strip-shaped detector makes it possible to limit the effects of scattered radiation, in particular by Compton interaction of the X-rays with the patient. In CBCT type systems implementing a cone beam associated with a flat detector, the effects of scattered radiation can be minimized by using an anti-scattering grid placed on the detector. However, CBCT type systems cannot obtain sufficient clarity for certain medical examinations, in particular for the analysis of soft tissues.

[0005] Moreover, in known systems of the CT scanner or CBCT type, the X-ray tube has significant dimensions, in particular due to the implementation of a thermionic cathode. Moreover, depending on the power of the X-ray tube, the latter can be equipped with a fixed anode or a rotating anode allowing to disperse the dissipated thermal power. Fixed anode tubes have a power of a few kilowatts and are mainly used for low power medical, security and industrial applications. Rotating anode tubes can have a power exceeding 100 kilowatts and are mainly implemented in the medical field for imaging requiring a large X-ray flux, so that the contrast of the obtained images can be enhanced. For example, the diameter of an industrial tube is about 150 mm at 450 kV, about 100 mm at 220 kV and about 80 mm at 160 kV. The voltages indicated correspond to the potential difference applied between the cathode and the anode. SUMMARY

[0006] The present invention aims at producing a radiological device combining the advantages of the two known device types (CT scanner and CBCT) while avoiding their drawbacks. The device according to the invention comprises a generator and a detector that rotate together around a patient or more generally around an object to be subjected to X-ray irradiation. It implements a "fan beam" type of beam, while only requiring a single rotation, even a fraction of a turn, around the object to be subjected to X-ray irradiation.

[0007] The aim of the present invention is to produce a radiological device whose mechanical structure is much lighter than that of a device of the CT scanner type, while maintaining a low susceptibility to the effects of scattered radiation. In certain variants of the invention, it is even possible to correct for the effects of scattered radiation and thus clearly improve the quality of the radiological images obtained, whether two-dimensional or three-dimensional.

[0008] To this end, the subject of the present invention is a radiological device comprising an ionizing radiation generator and a detector configured to detect the radiation emitted by the generator, the generator and the detector being opposite each other, the device delimiting a useful volume crossed by the ionizing radiation coming from the generator and received by the detector, the generator comprising a plurality of sources distributed in one direction and each emitting a substantially flat and fan-shaped beam of ionizing radiation towards the detector (14), the sources being arranged to irradiate all of the useful volume without translation. The device also comprises a computer configured to produce a two-dimensional image of an object to be subjected to X-ray irradiation located in the useful volume, without relative movement between the generator and the detector, the computer being configured to collect information from the detector along strips of the detector, each strip being arranged to be opposite one of the beams and to establish a two-dimensional image by concatenating the information from different strips of the detector.

[0009] Advantageously, the computer is configured to produce an estimate of the radiation scattered in each of the strips from the radiation measured by the detectors outside the relevant strip and to subtract this estimate of scattered radiation from the measurements performed by the detectors in the relevant strip.

[0010] Advantageously, the computer is configured to produce an estimate of the radiation scattered in each of the bands from a model of scattered radiation moving away from the relevant band (14-i).

[0011] Advantageously, the device comprises a support able to carry the object to be irradiated by X-rays and an actuator able to move the assembly formed by the generator and the detector around the support. The computer can then be configured to produce a three-dimensional image of the object to be irradiated by X-rays located in the useful volume from the plurality of two-dimensional images produced by moving the assembly formed by the generator and the detector around the support between each two-dimensional image.

[0012] Advantageously, the detector is formed by a flat panel extending in two perpendicular axes, a first axis of the two axes being parallel to the direction in which the sources are distributed and a second axis of the two axes belonging to the plane in which one of the beams propagates.

[0013] Advantageously, the planes in which the beams propagate are parallel to each other.

[0014] Advantageously, each source comprises a cold cathode emitting an electron beam by field effect.

[0015] Advantageously, at least several of the sources have a common vacuum chamber.

[0016] As a variant, the generator can comprise a plurality of series of aligned sources, each series being aligned along one direction and each emitting a substantially flat ionizing beam, the planes of each of the beams being parallel to each other.

[0017] The directions of each of the series of sources can be parallel to each other.

[0018] Furthermore, the subject of the application is a method of implementing a device according to the application, the method comprising successively ordering the emission of a plurality of the sources.

[0019] The sources are arranged along their directions and advantageously grouped together in subsets each grouping together sources of uniform distribution, the subsets being nested with each other, the method then comprising controlling the simultaneous emission of the sources of the same subset and successively ordering the emission of the different subsets.

[0020] Advantageously, the method comprises synchronizing the sources and the detector spatially and temporally.

[0021] Advantageously, the method comprises synchronizing the emission of each source with the assignment of the corresponding band of the detector.

[0022] Advantageously, the method comprises synchronizing the emission of each source with the assignment of the corresponding band of the detector.

[0023] Advantageously, the method comprises combining the emission of different origins with the movement of the actuator.

[0024] Advantageously, the method comprises moving the actuator continuously during the emission of different origins. BRIEF DESCRIPTION OF DRAWINGS

[0025] The application will be better understood and other advantages will become apparent on reading the detailed description of embodiments, given by way of example, the description being illustrated by the appended drawings among which:

[0026] Figure 1 a and 1b A first variant of a radiological device according to the application is shown by a front view and a side view;

[0027] Figure 2 An example of an ionizing radiation generator that can be implemented in a radiological device according to the application is represented;

[0028] Figure 3 An example of a detector in the form of a flat panel that can be implemented in a radiological device according to the application is represented in cross-section view;

[0029] Figure 4 A second variant of a radiological device according to the application is shown by a front view;

[0030] Figure 5a , 5b and 5c show a method of implementing a device according to the application;

[0031] Figure 6 Other components of a radiological device are shown;

[0032] Figure 7 A configuration of a device that can reduce the impact of scattered radiation is represented. DETAILED DESCRIPTION

[0033] For the sake of clarity, identical elements will have the same reference signs in the various drawings.

[0034] Figure 1 a and 1b The main components of a radiological device 10 for computed tomography examinations are schematically shown. The device 10 is particularly used for medical examinations. It is of course possible to implement the device 10 in any other field, in particular in industry for non-destructive examinations and in security for detecting dangerous objects or materials.

[0035] The apparatus 10 comprises an ionizing radiation generator 12 and a detector 14 configured to detect the radiation emitted by the generator 12. The object to be irradiated by X-rays is placed on a support 62 between the generator 12 and the detector 14. The apparatus 10 also comprises a computing apparatus, not shown, and makes it possible to process the data from the detector 14 to make them available to the operator of the apparatus. This processing can notably produce a 2D or 3D reconstruction of the object to be irradiated by X-rays.

[0036] The generator 12 and the detector 14 are opposite with respect to each other. In a simple embodiment of the radiological apparatus, the generator 12 and the detector 14 can be fixed with respect to each other. Alternatively, a radiological apparatus can be provided in which the generator 12 and / or the detector 14 are movable with respect to each other. In the following, an embodiment in which they are fixed with respect to each other will be considered.

[0037] The generator 12 comprises a plurality of ionizing radiation sources 16 distributed along a direction 18. Each source 16 emits an ionizing radiation beam 20 which is substantially flat and shaped like a fan tail. This type of beam is known in the literature as a "fan beam". In a simple configuration, the direction 18 is rectilinear and the planes in which the beams 20 propagate are substantially parallel to each other and at right angles to the direction 18. In the context of the present invention, other configurations are also possible. The direction 18 can be curved and the planes of the beams 20 can be neither parallel to each other nor at right angles to the direction 18.

[0038] The sources 16 are advantageously compact, for example as described in patent application No. WO2019 / 011980A1 in the name of the Applicant. Each source comprises, in a vacuum chamber, a cathode which emits an electron beam, an anode which has a target bombarded by the electron beam and which emits an ionizing radiation beam. The cathode advantageously emits the electron beam towards the target by field effect. This type of cathode is also called a cold cathode, as opposed to a hot cathode also called a thermionic cathode.

[0039] The advantage of implementing a compact cold cathode source is to allow the convergence of the foci of the beams 20 along the direction 18.

[0040] Figure 2 An example of the generator 12 is represented in more detail in which a plurality of the sources 16 have a common vacuum chamber 22. In particular, all the sources 16, or at least a plurality of the sources, can be produced in a single vacuum chamber 22. The advantage of a plurality of sources 16 sharing a vacuum chamber is to allow the convergence of the foci of the beams 20. The distribution of the sources 16 along the direction 18 can be uniform, as shown in Figure 2 where the distance separating two adjacent sources 16 is constant. A non-uniform distribution can also be chosen. Alternatively, in the context of the present invention, it is of course possible to implement a vacuum chamber for each source 16.

[0041] In the example of the generator 12 represented in Figure 1, the sources 16 are distributed along a straight line. In the context of the present invention, other configurations are also possible. The sources 16 can be distributed along a curved line. The sources 16 can also be distributed in a non-uniform manner. Figure 2In this case, the cold cathodes 24 are distributed along the axis 18. The sources 16 can comprise an anode 26 common to the different sources 16. The anode 26 carries as many targets 28 as the cathodes 24. Each cathode 24 emits an electron beam 30 towards the target 28 associated with it. The interaction between the electron beams 30 and the targets 28 makes it possible to produce the ionizing beam 20. The different sources 16 can be controlled independently of one another by controlling their respective cathodes 24.

[0042] It is clearly understood that the application can also be implemented with thermionic cathode sources.

[0043] The detector 14 is configured to receive the different beams 20 emitted by the sources 16. The detector 14 can comprise a plurality of individual strip detectors. Each individual detector is arranged opposite one of the beams 20. Alternatively, the detector 14 is produced in the form of a surface detector that can be curved or in the form of a flat panel extending in two perpendicular axes 32 and 34. The axis 32 is parallel to the direction 18 and the axis 34 belongs to one of the planes of the beams 20. The flat panel is described, for example, in European patent EP 1 378 113 filed by the company TRIXELL. This patent addresses the butt joining of a plurality of substrates to produce a flat panel of a size greater than a standard substrate. Other detectors produced in the form of a flat panel by the company TRIXELL or other companies can also be implemented in the context of the application.

[0044] The use of a flat panel simplifies the acquisition of data from the detector 14. Indeed, the flat panel can be equipped with a reading circuit and a multiplexer, the output of which transmits all the data from the detector 14 by serial link.

[0045] Figure 3 An example of a detector 14 in the form of a flat panel is represented in cross section. The detector 14 allows the detection of ionizing radiation, the direction of which is illustrated by the arrows 36 belonging to the different planes of the beams 20. The detector 14 comprises a sensor 38, a scintillator 40 that converts the ionizing radiation into radiation to which the sensor 38 is sensitive, for example in the visible light band, and a rigid input window 42 that is crossed by the ionizing radiation upstream of the scintillator 40. The scintillator can be dispensed with by implementing a sensor that is directly sensitive to the ionizing radiation. The scintillator 40 is arranged between the sensor 38 and the input window 42. The sensor 38 comprises a substrate 44 and light-sensitive elements 46 arranged on the substrate 44. The scintillator 40 comprises a support 48 and a scintillating substance 50 arranged on the support 48. Alternatively, the support 48 can be omitted and the scintillating substance 50 deposited directly on the sensor 38. A tight seal joint 52 fixes the input window 42 to the substrate 44. The seal joint 52 can be used to fix the scintillator 40 to the sensor 38. The light-sensitive elements 46 are organized in rows and columns. The rows extend along the axis 32 and the columns extend along the axis 34, or vice versa.

[0046] In Figure 1 b which the different ionizing beams 20 are represented as being at a distance from each other, parallel to each other, each in a plane at right angles to the direction 18. In practice, in order for the object to be irradiated by X-rays to be completely traversed by the ionizing radiation, the beams 20 are continuous, even slightly overlapping. More specifically, the device 10 delimits a useful volume 60, as Figure 1 a indicated, in which the object can be irradiated by X-rays, that is to say traversed by the ionizing radiation received by the detector 14. The beams 20 can fan out outside the median plane in which they are represented vertically in Figure 1 b order to become continuous, even overlapping, within the useful volume 60. Along its direction 18, the source 16 is arranged to irradiate all of the useful volume 60 without translation, as opposed to a radiological device of the CT scanner type, which requires the object to be irradiated by X-rays to be translated relative to the assembly formed by the X-ray generator and the associated detector in order to scan its useful volume.

[0047] The device 10 comprises a support 62 able to carry the object to be irradiated by X-rays. In the medical field, the support 62 is for example a table on which the patient lies down. In order to carry out a computed tomography examination, the assembly formed by the generator 12 and the detector 14 revolves around the support 62. The generator 12 and the detector 14 can be coupled by an arm 64, for example in the shape of a circular arc centered on the axis of rotation 66 of the generator 12 and the detector 14. The axis of rotation 66 is at right angles to the different planes of the beams 20. In order to carry out the rotation, the device comprises an actuator represented by a rotary movement device 68. During the rotation, the beams 20 revolve around the axis 66. Thus, for all the stages of rotation, the useful volume 60 in which the beams 20 produce irradiation and reach the detector 14 is in the shape of a cylinder around the axis 66. For example, a useful volume 60 of 10 cm can be obtained along the axis 66 by a generator 12 comprising 10 sources 16 regularly distributed along the direction 18, which is here rectilinear. As Figure 2 indicated, a common vacuum chamber 22 can be used to produce a generator 12 comprising 10 sources 16 distributed per centimeter. In practice, the invention advantageously implements a generator 12 comprising at least 10 sources 16 in order to obtain a useful volume of advantageous minimum size.

[0048] For reasons of production of the common vacuum chamber 22, the common vacuum chamber 22 can not exceed a maximum number of sources 16, for example 10 sources 16. If it is desired to produce a device with more than 10 sources, it is possible to produce a generator 12 with a plurality of vacuum chambers, the sources 16 of which are arranged in alignment with each other in the direction 18. It is also possible to slightly offset the directions 18 of the different vacuum chambers while keeping them parallel to each other

[0049] The actuator can be a rotary motor driving the arm 64 about the axis 66. Alternatively, the actuator can generate more complex movements resulting from a combination of translation and rotation. Such movements can make it possible to modify the shape or the position of the useful volume. In computed tomography, in order to ensure good reconstruction, it is important that the object to be irradiated by X-rays be traversed by ionizing radiation in all directions, to observe the Tuy condition. Complex movements of the actuator can make it possible to observe this condition in volumes without circular cross-section as illustrated in Figures 6 and 7. Figure 1 a and 1b This makes it possible to better adapt to the shape of the object to be irradiated by X-rays. The movements advantageously contain in the plane of the Figure 1 b , that is to say in a plane at right angles to the plane of the beam 20. In order to perform a computed tomography examination, with the device according to the application, it is not necessary for the movements generated by the actuator to comprise a translation at right angles to the plane of the beam 20, as in a CT scanner type device. However, a translational movement at right angles to the plane of the beam 20 can be useful in order to increase the length of the useful volume 60 along the axis 66.

[0050] Figure 4 A second variant of the radiological device 70 according to the application is illustrated, which allows the useful volume to be enlarged. Once again, there is a detector 14, a support 62, an arm 64 and an actuator 68. The device 70 comprises a generator 72, which differs from the generator 12 in that there are a plurality of series of sources 16. Indeed, the generator 12 comprises only a single series of sources 16 arranged along a direction 18. The different series of the generator 72 are each arranged along a direction. In the example illustrated, the generator 72 comprises three series of sources, aligned respectively in directions 74, 76 and 78. Of course, this variant can be implemented for other numbers of series. As before, the different sources 16 of the generator 72 each emit a substantially flat beam 20 of ionizing radiation, the plane of each of the beams 20 being for example parallel to one another. Figure 4 The cross-section in a plane at right angles to the axis 66 is represented. The cross-section of the useful region 80 is here a disc. The directions 74, 76 and 78 can be parallel to one another and parallel to the axis of rotation 66. In this case, the useful volume 80 extends cylindrically about the axis 66. Other arrangements of the directions 74, 76 and 78 are possible, for example parallel to one another and not parallel to the axis 66, or even not parallel to one another. These alternatives can adjust the shape of the useful region 80 as desired.

[0051] In both variants 10 and 70 described previously, the simultaneous emission of all sources 16 can lead to difficulties in distinguishing the photons from each source 16 at the output of the detector 14. This distinction is particularly useful for limiting the effects of scattered radiation. These effects can be limited by placing an anti-scattering grid on the detector 14. One alternative that can be combined with the presence of an anti-scattering grid consists in successively ordering the emission of a plurality of sources 16 among the sources 16. The aim of this ordering is to avoid the simultaneous emission of a plurality of sources 16 whose simultaneous emission would add together the respective scatterings. In other words, it is possible to emit with only one of the sources 16 at a time, or to allow the simultaneous emission of sources 16 sufficiently spaced apart from one another according to the attenuation gradient of the halo produced by the scattered radiation. When it is desired to irradiate all of the useful volume 60 or 80, all of the sources 16 must emit at least once. It is also possible to reduce the length of the useful volume along the axis 66, for example when the object to be irradiated by X-rays is smaller than the maximum useful volume of the device. This reduction of the useful volume is achieved by selecting a portion of the sources 16, these portions being opposite to the object to be irradiated by X-rays.

[0052] Figures 5a to 5c The ordering of such simultaneous emissions is illustrated, in which, at each emission instant, the separation between two sources 16 along the direction 18 is maintained. The sources 16 are grouped together in a plurality of subsets, these subsets each grouping together sources that are uniformly distributed. The subsets are nested with one another and the method consists in controlling the simultaneous emission of the sources 16 of the same subset and the successive ordering of the emission of different subsets.

[0053] More particularly, the generator 12 comprises N sources 16 arranged in the direction 18. The order of the sources 16 is denoted i, i thus varying from 1 to N. The distance separating two successive sources 16i and 16i+1 along the direction 18 is constant for the N sources 16. These sources are divided into P subsets, these subsets each comprising sources of order j.(N / P+1)+i, j varying from 0 to N / P - 1 for a subset and i varying from 1 to P for each subset, i and j being natural integers. The subsets successively emit. N does not necessarily divide P. If N does not divide P, in the formula giving the order, the integer part of N / P will be taken and the sources of order higher than the integer part (N / P).P are then divided into the subsets by maintaining the same pitch between the sources 16.

[0054] In Figures 5a to 5c , the order of the sources 16 is specified. In Figure 5a , at the first instant of the cycle, the sources of order 1, 6, 11 and 16 emit. At the next instant, as Figure 5b illustrated, the sources of order 2, 7, 12 and 17 emit. At the last instant of the cycle, as Figure 5cThe order is shown to be 5, 10, 15 and 20 for the sources. In this example, the emission cycles of the different subsets are ordered in the order of the first source of each subset. It is also possible to make the subsets emit in other orders, for example to make the subsets in which the first source has an odd order emit first, then the subsets in which the first source has an even order. This makes it possible to limit the remanence of the reading implemented by the detector 14.

[0055] The successive emissions performed by the different sources, whether this emission is individual (one source at a time) or collective (i.e. one subset at a time), can be implemented with the device 70, in which it is advantageous for the sources not to be emitted simultaneously if they are too close to one another. In the case of emission in subsets, each of the subsets can comprise sources belonging to the same direction or to different directions.

[0056] In addition to the successive emissions, it is advantageous to synchronize the detector therewith. More particularly, as mentioned above, the detector 14 comprises light-sensitive elements organized in a matrix of rows and columns. The designation of the rows and columns is purely conventional, and therefore, in what follows, the term row will be used, but it can be applied to the rows or to the columns. The detector is ordered in an acquisition phase, then in a matrix reading phase. It is possible to read row by row. By orienting the detector 14 in this way so that the orientation of the reading rows is in line with the orientation of the plane of the beam 20, it is possible to read only the row or rows closest to the plane of the beam 20, and more particularly the row or rows illuminated by the beam or beams 20 emitted simultaneously. Thus, it is possible to ignore the ionizing rays forming essentially scattered radiation, deflected by the object to be irradiated by the X-rays, when reading the matrix. More generally, the sources 16 and the detector 14 are spatially and temporally synchronized.

[0057] In computed tomography, it is necessary to rotate the generator 12 or 72 and the detector 14 to produce a 2D or 3D reconstruction of the object to be irradiated by X-rays. The presence of a plurality of sources 16 emitting parallel beams makes it possible to perform only a single revolution or only a fraction of a turn to obtain the different cuts necessary for the reconstruction. To this end, the emission of the different sources 16 and the rotation of the actuator 68 are combined. Different combination modes are possible. For example, it is possible to make the actuator 68 revolve incrementally and to make all the sources 16 emit continuously between each rotation increment. It is also possible to perform smaller increments and to perform an emission of one source 16 or of a subset of sources 16 between each increment. It is also possible to make the actuator 68 revolve continuously and, during its rotation, to perform as many emission cycles as necessary. In practice, during the continuous rotation, it is possible to take into account that, during the emission, the actuator 68 is in fact stationary. The continuous movement of the arm 64 carrying the detector 14 and the generator 12 or 72 makes it possible to limit the effects of the mechanical inertia of the mobile elements. Indeed, in the case of incremental movement of the actuator, each stop and each start of the actuator generates a jerk which reduces the positioning accuracy of the arm 64. The continuous movement of the actuator 68 makes it possible to limit these jerks. Preferably, the continuous movement of the actuator 68 is carried out uniformly, that is to say at a constant speed, which completely eliminates all the jerks. At the same time, while maintaining the continuous movement of the actuator 68, it is possible to slow down its movement during each emission of the sources 16 and to speed up its movement between two emissions.

[0058] It is also possible to implement a device according to the application without an actuator. In other words, the generator 12 or 72 and the detector 14 remain fixed relative to the support 62. This device can be used for X-ray objects which can generate strong scattering by Compton interaction, for example for performing a lung X-ray in the medical field. This type of radiology is generally performed by a generator emitting a conical X-ray beam. The generator is associated with a flat detector in which the scattered radiation can only be distinguished from the useful information by a backscattering grid; this grid is moderately efficient and imposes a greater dose of ionizing radiation on the patient. By implementing the application, it is possible to emit continuously by the different sources 16. By synchronizing the detector 14 and the generator 12 or 72 in time and in space, it is possible to avoid detecting scattered radiation. In practice, the complete emission cycle of all the sources of the device can be fast enough to be considered instantaneous and thus to obtain an almost instantaneous image of the object to be irradiated by X-rays.

[0059] Figure 6The radiological device 10 is again represented to illustrate the means that allow it to produce images. This device comprises a computer 90 configured to produce a two-dimensional image 92 of an object to be irradiated by X-rays located within the useful volume 60. Each source, here identified as 16-1 to 16-7, emits a beam 20 towards the detector 14. As mentioned above, the emission of the different sources 16-1 to 16-7 is advantageously performed sequentially. Each beam 20 is received by a zone of the detector 14, forming a band of pixels of the detector 14 disposed opposite each beam 20. These opposite bands 14-1 to 14-7 are identified with reference to the sources 16-1 to 16-7.

[0060] The computer 90 is configured to collect information from each band 14-1 to 14-7. To establish the two-dimensional image 92, the computer 90 is configured to combine the information from the different bands 14-1 to 14-7 of the detector 14. To produce the two-dimensional image 90, the actuator 68 remains inactive. The assembly formed by the generator 12 and the detector 14 is immobile relative to the support 62. The image acquisition is similar to that performed by a conventional radiological device in two dimensions or by a CBCT type device without rotation. The main advantage of implementing the device 10 according to the application is to reduce the impact of scattered radiation. Indeed, each band 14-1 to 14-7 detects only the radiation contained in the plane of the beam 20 from the corresponding source 16-1 to 16-7 and ignores the scattered radiation outside this plane. More particularly, a band 14-i is defined as receiving direct radiation from the corresponding source 16-i. The band 14-i is entirely irradiated by the direct radiation from the corresponding source 16-i. Direct radiation is understood to be radiation without scattered radiation. By design of the device, each band is aligned with the beam 20 from the corresponding source. In this way, the pixels of each band essentially receive direct radiation from the corresponding source. Only a small fraction of the scattered radiation from the same source and propagating in the plane of the beam reaches the pixels of this band. Most of the scattered radiation propagates outside the plane of the light and thus does not reach the pixels of the relevant band. As will be seen later, this majority of scattered radiation can be detected by other pixels of the detector located outside the relevant band. The band advantageously has a width smaller than the width of the beam at the detector, so as to limit as much as possible the detection of scattered radiation coming from the considered beam and propagating away from the plane of the beam. As mentioned previously, the beams can slightly overlap. In this case, it is advantageous to stagger in time the emission of the sources immediately adjacent, for example using Figures 5a to 5c In this case, the bands of the detector can also overlap. The reading of the bands is synchronized with the emission of the corresponding sources so that all the bands can be read in turn. Implementing overlapping bands can widen the width of each band and thus receive a greater signal amplitude. These bands form zones of the detector temporally assigned to read the flow of photons from each source. The temporal assignment is synchronized with the emission of the sources. When controlling the emission of the different sources, it should be avoided that a band is able to receive direct radiation instead of radiation originating from the source with which it is associated.

[0061] The quality of the image can be further enhanced. Indeed, each band of the detector 14 receives interleaved radiation in the normal plane of the beam 20 and it is advantageous to correct the measurements made by the detector 14 in each band 14-1 to 14-7 to reduce the portion due to scattered radiation. In each band 14-1 to 14-7, this portion can be estimated from measurements made outside the band under consideration. Indeed, during the emission of the beam 20 opposite the band under consideration, only this band receives the useful signal from the beam 20 that has crossed the object to be radiated by X-rays. Outside this band and outside the other bands activated at the same time and opposite the beam 20, only scattered radiation reaches the detector when crossing the object to be radiated by X-rays. The scattered radiation present in the band itself can be estimated by the measurements made by the detector outside the band under consideration. The measurements performed in the band can then be corrected by subtracting the estimate of the scattered radiation from the measured radiation.

[0062] Figure 7 Various ways of estimating the scattered radiation present in the band irradiated by the beam 20 and referenced 14-i are illustrated. In a first method, it can be considered that the scattered radiation is constant on an axis 100 at right angles to the maximum length of the band 14-i. One pixel or one group of pixels 100-1 of the detector 14 located outside the band 14-i is chosen. The level of radiation scattered within the band 14-i is considered equal to the level of scattered radiation measured by the pixel 100-1 during the irradiation of the object to be radiated by X-rays. For all the pixels located within the band 14-i along the axis 100, the value measured by the pixel 100-1 is subtracted from the measurements made.

[0063] Two pixels or two groups of pixels 100-1 and 100-2, both located outside the band 14-i, can also be chosen. The pixels 100-1 and 100-2 are set on either side of the band 14-i and equidistant from the band 14-i. It can be clearly understood that, during the emission of the beam 20, the pixels 100-1 and 100-2 are not illuminated by the other beams 20. The estimate of the scattered radiation within the band 14-i is then equal to the average of the measured values in each pixel 100-1 and 100-2. These measurements are made for all the axes at right angles to the maximum length of the band 14-i. All the measurement pixels are set on axes 102-1 and 102-2 parallel to the maximum length of the band 14-i. Since the spatial variation of the scattered radiation is generally slow, the measurements made on all the points of type 100-1 on one side and on all the points of type 100-2 on the other side can be smoothed along their respective axes 102-1 and 102-2.

[0064] The estimation of the level of scattered radiation present in the band 14-i can be improved by moving a reduction model of the scattered radiation away from the band 14-i. The reduction is a function of the distance from the band 14-i along the axis 100. This reduction model can be defined empirically by measurements made from a sample object of properties close to the real object expected to be irradiated by the X-rays. Once the measurements necessary to establish the model are completed, these measurements can be approximated using for example a polynomial or a trigonometric function. From the model retained, the level of scattered radiation within the band 14-i can be estimated by inputting in the model the measurements made outside the band, these measurements being performed during the irradiation of the object to be irradiated by the X-rays. When the X-rays are performed, the measurements made by the pixels 100-1 and 100-2 are introduced in the retained model to estimate the level of scattered radiation within the band 14-i along the axis 100. As mentioned previously, the measurements outside the band 14-i are performed on the axes 102-1 and 102-2 in order to correct all the pixels of the band considered. Using this model, the correction of the scattered radiation can be refined by individualizing the correction for each pixel of the band considered.

[0065] The measurement correction capable of limiting the influence of the scattered radiation can be implemented in a radiological system having only a single source 16. In other words, it is advantageous to implement this type of correction in a CT scanner.

[0066] In addition, the computer 90 can be configured to produce a three-dimensional image 94 of the object to be irradiated by the X-rays located within the useful volume 60. To produce the three-dimensional image, cuts of the object in the planes formed by each beam 20 can be constructed. These cuts are constructed from the information received by the detector by rotating the generator 12 and the detector 14 around the support 62. The three-dimensional image is obtained from the different cuts. To perform this type of reconstruction, algorithms generally implemented in devices of the CT scanner type can be implemented. The main advantage of implementing the device 10 according to the application is the reduction of the weight to be rotated.

[0067] Alternatively, the three-dimensional image 94 can be constructed from a plurality of two-dimensional images as mentioned previously. Between each two-dimensional image, the generator 12 and the detector 14 are rotated around the support 62 by the actuator 68. The three-dimensional image can be constructed by performing algorithms generally implemented in devices of the CBCT type. Here, the main advantage of implementing the device 10 according to the application is the reduction of the influence of the scattered radiation in each two-dimensional image, which enhances the quality of the three-dimensional image 94.

Claims

1. A radiological apparatus comprising an ionizing radiation generator (12; 72) and a detector (14) configured to detect the radiation emitted by the generator (12; 72), the generator (12; 72) and the detector (14) being opposite with respect to each other, the apparatus (10) delimiting a useful volume (60; 80) crossed by the ionizing radiation coming from the generator (12; 72) and received by the detector (14), characterized in that, The generator (12; 72) comprises a plurality of sources (16) distributed along a direction (18; 74, 76, 78) and each emitting a beam (20) of ionizing radiation substantially flat and shaped like a fan tail towards the detector (14); the sources (16) are arranged to irradiate the whole of the useful volume (60; 80) without needing to be translated; the apparatus comprises a computer (90) configured to generate a two-dimensional image (92) of an object to be irradiated by X-rays located in the useful volume (60) without there being relative movements between the generator (12) and the detector (14), the computer (90) being configured to collect information from the detector (14) along strips (14-1 to 14-7) of the detector (14), each strip (14-1 to 14-7) being arranged opposite one of the beams (20) and being configured to build the two-dimensional image (92) by concatenating the information coming from different strips (14-1 to 14-7) of the detector (14); wherein the radiological apparatus further comprises a support (62) able to carry an object to be irradiated by X-rays and an actuator (68) able to move the assembly formed by the generator (12; 72) and the detector (14) around the support (62), and wherein the computer (90) is configured to generate a three-dimensional image (94) of an object to be irradiated by X-rays located in the useful volume (60) from a plurality of two-dimensional images (92) generated by moving the assembly formed by the generator (12; 72) and the detector (14) around the support (62) between each two-dimensional image (92); wherein the emission of different sources (16) is combined with the movement of the actuator (68); and wherein the actuator rotates incrementally and the sources emit continuously between each rotation increment, or the actuator remains continuously moving and slows down its movement during each emission of a source and accelerates between two emissions.

2. The apparatus of claim 1, wherein, The computer (90) is configured to generate an estimate of the scattered radiation in each of the strips (14-1 to 14-7) from the radiation measured by the detector (14) outside the relevant strip (14-i) and to subtract the estimate of the scattered radiation from the measurements performed by the detector (14) in the relevant strip (14-i).

3. The apparatus of claim 2, wherein, The computer (90) is configured to generate an estimate of the scattered radiation in each of the strips (14-1 to 14-7) from a model of the scattered radiation moving away from the relevant strip (14-i).

4. The device of one of the preceding claims, characterized in that The detector (14) is formed by a flat panel extending on two orthogonal axes (32, 34), a first axis (32) of the two axes being parallel to the direction (18) along which the sources (16) are distributed, a second axis (34) of the two axes belonging to the plane in which one of the beams (20) propagates.

5. The apparatus of one of claims 1-3, wherein, The planes in which the beams (20) propagate are parallel to each other.

6. The apparatus of one of claims 1-3, wherein, Each source (16) includes a cold cathode (24) that emits an electron beam (30) by field effect.

7. The apparatus of claim 6, wherein, At least a plurality of the sources (16) have a common vacuum chamber (22).

8. The apparatus of one of claims 1-3, wherein, The generator (72) includes a plurality of series of aligned sources (16), each series aligned along a direction (74, 76, 78) and each emitting a substantially planar ionizing radiation beam (20), the planes of each of the beams (20) being parallel to each other.

9. The apparatus of claim 8, wherein, The directions (74, 76, 78) of each of the series of aligned sources (16) are parallel to each other.

10. A method of implementing a radiological device, the radiological device being the device according to one of the preceding claims, characterized in that, It includes sequential ordering of the emission of a plurality of the sources (16).

11. The method of claim 10, wherein, The sources (16) are arranged along their directions (18; 74, 76, 78) and grouped together in subsets, each subset grouping uniformly distributed sources, the subsets being nested to each other, and the method includes controlling the simultaneous emission of the sources of a same subset and sequential ordering of the emission of different subsets.

12. The method of any one of claims 10 and 11, wherein, It includes spatially and temporally synchronizing the sources (16) and the detector (14).

13. The method of claim 12, wherein, It includes synchronizing the emission of each source (16-i) with the assignment of a corresponding band (14-i) of the detector (14).

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