EP4044928A1

EP4044928A1 - Radiology device with several sources of ionising rays and method implementing the device

Info

Publication number: EP4044928A1
Application number: EP20789638.2A
Authority: EP
Inventors: Guillaume Bernard
Original assignee: Thales SA
Current assignee: Thales SA
Priority date: 2019-10-17
Filing date: 2020-10-19
Publication date: 2022-08-24
Also published as: FR3102055B1; CN114727789A; FR3102055A1; WO2021074445A1; JP2022552697A

Abstract

The invention relates to a radiology device comprising an ionising ray generator (12) and a detector (14) configured to detect the rays emitted by the generator (12), the generator (12) and the detector (14) being opposite each other, the device (10) defining a useful volume (60), traversed by the ionising rays originating from the generator (12) and received by the detector (14), the generator (12) comprising a plurality of sources (16) distributed in one direction (18) and each emitting a beam (20) of ionising rays that are basically flat and fan shaped, the sources (16) being disposed so as to irradiate the entire useful volume (60) without translation. A further aim of the invention is a method implementing a device (10) according to the invention and involving successively linking the emission of several of the sources (16).

Description

DESCRIPTION

Title of the invention: Radiology device with several sources of ionizing rays and method using the device

The invention relates to a radiology device and a method using the device. The invention can be implemented in the medical field, in industry to perform non-destructive testing and in security to detect dangerous objects or materials. The invention also relates to a method using the radiology device. The invention finds particular utility in computed tomography. The invention can also be implemented in conventional radiology without movement around the object to be radiographed.

[0002] In a known manner, computed tomography, also called computed tomography, implements a system equipped with an X-ray tube emitting a collimated beam in the form of a fan known in English under the name of "fan beam" associated with a detector in a strip arranged opposite the beam. The tube and the detector revolve around a table receiving the patient. With each revolution, the table moves forward following the axis of rotation of the tube and the detector. Computer processing makes it possible to reconstruct 2D or 3D volume sections of the patient's anatomical structures. This system is known under the name of "CT-scanner". "CT" is the acronym for "Computer Tomography".

[0003] More recently, other systems having a tube emitting a conical X-ray beam, known in English under the name of "Cone Beam", associated with a flat detector have appeared. The tube and the detector are mounted on a rotating arm in the shape of the letter C. These systems are known in English as "C-arm" or by the acronym CBCT for "Cone Beam Computer Tomography". The conical shape of the beam eliminates the need for translation implemented for the CT-scanner. For CBCT, the data acquisition is much faster because it only requires one turn around the patient of the assembly formed by the tube and the detector.

In CT-scanner type systems, the flat shape of the beam associated with the strip detector makes it possible to limit the effects of scattered radiation in particular by Compton interactions of X-rays with the patient. In CBCT type systems using a conical beam associated with a flat detector, it is possible to minimize the effects of scattered radiation by using an anti-scattering grid placed on the detector. However, the CBCT type system does not make it possible to obtain a sufficient definition for certain medical examinations, in particular for the analysis of soft tissues.

[0005] Furthermore, in known systems, of the CT-scanner or CBCT type, the X-ray tubes have large dimensions, in particular due to the use of thermionic cathodes. In addition, depending on the power of the X-ray tubes, they can be equipped with either a fixed anode or a rotating anode allowing a spread of the dissipated thermal power. Fixed anode tubes have a power of a few kilowatts and are used in particular in low power industrial, safety and medical applications. Rotating anode tubes can exceed 100 kilowatts and are mainly used in the medical environment for imaging requiring high X-ray fluxes, which makes it possible to improve the contrast of the images obtained. For example, the diameter of an industrial tube is of the order of 150mm at 450kV, 100mm at 220kV and 80mm at 160kV. The voltage indicated corresponds to the potential difference applied between the cathode and the anode.

The invention aims to provide a radiology device combining the advantages of two types of known devices, CT-scanner and CBCT, while avoiding their drawbacks. A device according to the invention comprises a generator and a detector rotating together around the patient or more generally the object to be radiographed. It uses fan beams while requiring only a single turn, or even a fraction of a turn, around the object to be radiographed.

[0007] The objective of the invention is to provide a radiology device having a mechanical structure that is much lighter than that of a CT-scanner type device while retaining low susceptibility to the effects of scattered radiation. In certain variants of the invention, it is even possible to correct the effects of the scattered radiation and thus significantly improve the quality of the radiological images obtained both for two-dimensional images and for three-dimensional images. To this end, the invention relates to a radiology device comprising a generator of ionizing rays and a detector configured to detect the rays emitted by the generator, the generator and the detector being opposite one with respect to the other, the device delimiting a useful volume, crossed by the ionizing rays coming from the generator and received by the detector, the generator comprising several sources distributed along one direction and each emitting a beam of ionizing rays which is essentially flat and shaped. fan in the direction of the detector (14), the sources being arranged so as to irradiate the entire useful volume without translation. The device further comprises a computer configured to produce a two-dimensional image of an object to be radiographed located in the working volume without relative movement between the generator and the detector, the computer being configured to collect information from the detector along bands. of the detector, each band being arranged opposite one of the beams and to establish the two-dimensional image by juxtaposing the information coming from the different bands of the detector.

Advantageously, the computer is configured to make an estimate of the radiation scattered in each of the bands as a function of radiation measured by the detector outside the band concerned and to subtract the estimate of the scattered radiation from the measurements made by the detector in the affected band.

Advantageously, the computer is configured to estimate the radiation scattered in each of the bands as a function of a scattered radiation decay model moving away from the band concerned (14-i)

Advantageously, the device comprises a support capable of carrying an object to be radiographed and an actuator making it possible to move an assembly formed by the generator and the detector around the support. The computer can then be configured to produce a three-dimensional image of an object to be radiographed located in the useful volume from several two-dimensional images produced by moving between each two-dimensional image the assembly formed by the generator and the detector around the support.

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

Advantageously, the planes in which the beams propagate are mutually parallel.

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

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

[0016] As a variant, the generator can comprise several series of aligned sources, each series being aligned along a direction and each emitting an essentially flat beam of ionizing rays, the planes of each of the beams being mutually parallel.

The directions of each of the series of sources can be mutually parallel.

[0018] The subject of the invention is also a method implementing a device according to the invention, consisting in successively linking the transmission of several of the sources.

The sources are ordered along their direction and advantageously grouped into sub-assemblies each grouping together equally distributed sources, the sub-assemblies being nested within each other, the method then consisting in controlling the simultaneous emission of the sources of 'one and the same subset and successively chain the transmission of the different subsets.

Advantageously, the method consists in spatially and temporally synchronizing the sources and the detector.

Advantageously, the method consists in synchronizing the emission of each source with an allocation of the corresponding band of the detector.

Advantageously, the method consists in combining the emission from the different sources and the movement of the actuator. Advantageously, the method consists in moving the actuator continuously during transmission from the different sources.

[0025] The invention will be better understood and other advantages will appear on reading the detailed description of an embodiment given by way of example, description illustrated by the accompanying drawing in which:

Figures 1a and 1b illustrate a front and side view of a first variant of a radiology device according to the invention;

[0027] Figure 2 shows an example of an ionizing ray generator that can be implemented in a radiology device according to the invention;

[0028] Figure 3 shows in section an example of a detector in the form of a flat panel that can be implemented in a radiology device according to the invention;

[0029] Figure 4 illustrates a front view, a second variant of a radiology device according to the invention;

Figures 5a, 5b and 5c illustrate a method implementing a device according to the invention;

[0031] Figure 6 illustrates other components of the radiology device;

[0032] Figure 7 shows a configuration of the device for reducing the effects of scattered radiation.

For the sake of clarity, the same elements will bear the same references in the different figures.

Figures 1a and 1b schematically illustrate the main components of a radiology device 10 used for computed tomography examinations. The device 10 finds particular utility in medical examinations. It is of course possible to use the device 10 in any other field, in particular in industry, to carry out non-destructive testing and in security to detect dangerous objects or materials. The device 10 comprises an ionizing ray generator 12 and a detector 14 configured to detect the rays emitted by the generator 12. The object to be radiographed is placed between the generator 12 and the detector 14 on a support 62.

The device 10 also comprises computer means, not shown and making it possible to process the data coming from the detector 14 in order to make them usable for an operator of the device. This treatment can in particular achieve a 2D or 3D reconstruction of the object to be radiographed.

[0036] The generator 12 and the detector 14 face each other. In a simple embodiment of the radiology device, generator 12 and detector 14 can be fixed relative to each other. Alternatively, it is possible to provide a radiology device in which generator 12 and / or detector 14 are movable relative to each other. Subsequently, we will consider that they are fixed with respect to each other.

[0037] The generator 12 comprises several sources of ionizing rays 16 distributed along a direction 18. Each source 16 emits a beam 20 of ionizing rays which is essentially flat and in the shape of a fan. This type of beam is known in Anglo-Saxon literature under the name of "fan beam". In a simple configuration, the direction 18 is rectilinear and the planes in which the beams 20 essentially propagate are parallel to each other and perpendicular to the direction 18. Other configurations are possible within the scope of the invention. Direction 18 can be curved and the planes of beams 20 can be neither parallel to each other nor perpendicular to direction 18.

The sources 16 are advantageously compact as for example described in the patent application published under the number: WO 2019/011980 A1 filed in the name of the applicant. Each source comprises in a vacuum chamber, a cathode emitting an electron beam, an anode having a target bombarded by the electron beam and emitting a beam of ionizing rays. The cathode advantageously emits the electron beam by field effect in the direction of the target. This type of cathode is also known as cold cathode in opposition to hot cathodes also called: thermionic cathodes. The advantage of using compact cold cathode sources is to allow their focal point to be brought together along the direction 18.

Figure 2 shows in more detail an example of generator 12 in which several of the sources 16 have a common vacuum chamber 22. In particular, it is possible to produce all the sources 16 or at least several of them in a single vacuum chamber 22. The advantage of a vacuum chamber common to several sources 16 is to allow the focal points of the beams to be brought together 20. The distribution of the sources 16 along the direction 18 can be uniform as shown in FIG. 2 where the distance separating two neighboring sources 16 is constant. It is also possible to opt for a non-uniform distribution. Alternatively, in the context of the invention, it is of course possible to implement a vacuum chamber per source 16.

In Figure 2, the cold cathodes 24 are distributed along the axis 18. The sources 16 may include an anode 26 common to the different sources 16. The anode 26 carries as many targets 28 as there are cathodes 24. Each cathode 24 emits an electron beam 30 in the direction of the target 28 which is associated with it.

The interaction between an electron beam 30 and a target 28 makes it possible to generate a beam of ionizing rays 20. The different sources 16 can be driven independently of each other by means of the driving of their respective cathode 24.

[0042] It is understood that the invention can also be implemented with sources with thermionic cathodes.

The detector 14 is configured to receive the different beams 20 emitted by the sources 16. The detector 14 can include several elementary detectors in a strip. Each elementary detector being arranged opposite one of the beams 20. Alternatively, the detector 14 is produced in the form of a surface detector which may be curved or in the form of a flat panel extending along 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. A flat panel is for example described in European patent EP 1 378 113 filed by the company TRIXELL. This patent is concerned with the splicing of several substrates making it possible to produce a flat panel of larger dimensions than those of the substrates. standards. Other detectors produced in the form of flat panels and produced by the company TRIXELL or by other companies can also be used within the framework of the invention.

The use of a flat panel simplifies the capture of data from the detector 14. Indeed, the flat panel can be equipped with read circuits and a multiplexer whose output delivers the assembly over a serial link. data from detector 14.

FIG. 3 shows in section an example of a detector 14 in the form of a flat panel. The detector 14 allows the detection of ionizing rays, the direction of which is materialized by the arrows 36 belonging to the different planes of the beams 20. The detector 14 comprises a sensor 38, a scintillator 40 transforming the ionizing rays into radiation to which the sensor 38 is sensitive. , for example in the visible band, and a rigid entry window 42 traversed by the ionizing rays upstream of the scintillator 40. It is possible to do without a scintillator by using a sensor directly sensitive to the ionizing rays. The scintillator 40 is disposed between the sensor 38 and the entry window 42. The sensor 38 comprises a substrate 44 and photosensitive elements 46 disposed on the substrate 44. The scintillator 40 comprises a support 48 and a scintillator substance 50 deposited on the surface. support 48. Alternatively, it is possible to dispense with support 48 and deposit the scintillating substance 50 directly on the sensor 38. A waterproof seal 52 fixes the inlet window 42 to the substrate 44. The seal 52 can be used to attach scintillator 40 to sensor 38. Photosensitive elements 46 are organized in row and column. The lines extend along axis 32 and the columns extend along axis 34 or vice versa.

In Figure 1b, the various ionizing ray beams 20 are shown at a distance from each other, parallel to each other, each in a plane perpendicular to the direction 18. In practice, so that the object to be radiographed is completely crossed by the ionizing rays, the beams 20 are contiguous, or even slightly overlap. More precisely, the device 10 delimits a useful volume 60, identified in FIG. 1a, where the object can be radiographed, that is to say crossed by ionizing rays received by the detector 14. The beams 20 can be radiographed. flare around their median plane shown vertically in FIG. 1b until they become contiguous, or even overlap in the useful volume 60. Along their direction 18, the sources 16 are arranged so as to irradiate the whole of the useful volume 60 without translation, unlike the CT-scanner type radiology devices which require the translation of the object to be radiographed relative to the assembly formed by the generator X and the associated detector to scan their useful volume.

The device 10 comprises a support 62 capable of carrying the object to be radiographed. In the medical field, the support 62 is for example a table on which a patient can lie down. To carry out a tomodensitometry examination, the assembly formed by the generator 12 and the detector 14 rotates around the support 62. The generator 12 and the detector 14 can be connected by an arm 64, for example in the form of an arc of a circle centered on the axis 66 of rotation of the generator 12 and of the detector 14. The axis of rotation 66 is perpendicular to the different planes of the beams 20. To perform the rotation, the device comprises an actuator represented by a rotational movement 68. During the rotation, the beams 20 rotate about the axis 66. Consequently, the working volume 60 in which, for all the phases of rotation, the beams 20 producing irradiation and reaching the detector 14, is cylindrical in shape around the axis 66. By way of example, it is possible to obtain a useful volume 60 of 10cm along the axis 66 by means of a generator 12 comprising ten sources 16 regularly distributed along the direction 18 which is here rectilinear. A generator 12 comprising ten sources 16 distributed every centimeter can be produced, as shown in FIG. 2, with a common vacuum chamber 22. In practice, the invention is advantageously implemented for a generator 12 comprising at least ten sources 16 in order to obtain a useful volume of interesting minimum size.

For manufacturing reasons of the common vacuum chamber 22, the latter may not be able to exceed a maximum number of sources 16, for example ten sources 16. If one wishes to produce a device having more than 10 sources, it is possible to produce a generator 12 having several vacuum enclosures, the sources 16 of which are arranged in alignment with one another in direction 18. It is also possible to slightly offset the directions 18 of the different enclosures empty while keeping them parallel to each other.

The actuator can be a rotary motor driving the arm 64 around the axis 66. Alternatively, the actuator can generate a more complex movement made from a combination of translations and rotations. This movement can allow the shape or position of the useful volume to be modified. In tomodensitometry, in order to ensure a good reconstruction, it is important that the object to be radiographed is crossed in all directions by ionizing radiation, in order to respect Tuy's condition. A complex movement of the actuator can make it possible to comply with this condition in a volume not having a circular section as shown in FIGS. 1a and 1b. this makes it possible to better adapt to the shape of the object to be radiographed. The movement is advantageously contained in the plane of FIG. 1 b, that is to say in a plane perpendicular to the planes of the beams 20. To carry out a tomodensitometry examination, with a device according to the invention, it is not necessary. It is not necessary for the movement produced by the actuator to include a translation perpendicular to the planes of the beams 20 as with a device of the CT-scanner type. However, a translational movement perpendicular to the planes of the beams 20 can be useful in order to lengthen the useful volume 60 along the axis 66.

FIG. 4 illustrates a second variant of a radiology device 70 according to the invention making it possible to enlarge the useful volume. We find the detector 14, the support 62, the arm 64 and the actuator 68. The device 70 comprises a generator 72 which differs from the generator 12 by the presence of several series of sources 16. In practice, the generator 12 only includes a single series of sources 16 aligned along direction 18. The different series of generator 72 are each aligned along one direction. In the example shown, the generator 72 comprises three series of sources, respectively aligned in directions 74, 76 and 78. It is of course possible to implement this variant for other numbers of series. As previously, the different sources 16 of the generator 72 each emit an essentially flat beam 20 of ionizing rays, the planes of each of the beams 20 being for example parallel to each other. FIG. 4 is shown in section in a plane perpendicular to the axis 66. The section of the useful zone 80 is here a disc. The directions 74, 76 and 78 can be mutually parallel, and parallel to the axis of rotation 66. In this case, the useful volume 80 extends cylindrically around the axis 66. Other arrangements of the directions 74, 76 and 78 are also possible, for example parallel to each other and not parallel to the axis 66 or even not parallel to each other. These alternatives make it possible to adapt the shape of the useful zone 80 as needed.

In the two variants of the device 10 and 70 described above, the simultaneous emission from all the sources 16 can cause difficulties in discriminating, at the output of the detector 14, the photons coming from each source 16. This discrimination is particularly useful. to limit the effects of scattered radiation. These effects can be limited by placing an anti-scattering grid on the detector 14.

An alternative, which can be combined with the presence of an anti-scattering grid, consists in successively linking the emission of several of the sources 16. The aim of this linking is to avoid the simultaneous emission of several sources 16 including the respective scattered radiations. can add up to each other. In other words, it is possible to emit with only one of the sources 16 at a time or to authorize the simultaneous emission of sources 16 sufficiently distant from each other according to the decrease gradient of the halo created by the radiation. broadcast. When it is desired to irradiate the entire useful volume 60 or 80, all 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 radiographed is smaller than the maximum useful volume of the device. This reduction in the useful volume is done by selecting only part of the sources 16, parts located opposite the object to be radiographed.

Figures 5a to 5c illustrate this sequence of simultaneous transmissions in which at each moment of transmission, the distance between two sources 16, along the direction 18, is preserved. The sources 16 are grouped into several subsets each grouping together equally distributed sources. The sub-assemblies being nested within each other and the method consists in controlling the simultaneous transmission of the sources 16 of the same sub-assembly and in successively linking the transmission of the various sub-assemblies.

More specifically, the generator 12 comprises N sources 16 which are ordered according to the direction 18. The rank of a source 16 is denoted i, i therefore varying from 1 to N. The distance along the direction 18 separating two successive sources 16 i and i + 1 is constant for the N sources 16. The sources are divided into P subsets each comprising the sources of rank 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 numbers. The sub-assemblies transmit in turn. It is not mandatory that N be divisible by P. If N is not divisible by P, we will take in the formula giving the rank, the integer part of N / P and the sources of ranks greater than: Integer part ( N / P). P are then distributed in the sub-assemblies while keeping the same pitch between sources 16.

In Figures 5a to 5c, the rank of the sources 16 is specified. In FIG. 5a, at the first instant of the cycle, the sources of rank 1, 6, 11 and 16 transmit. At the next instant, shown in Figure 5b, the sources of rank 2, 7, 12 and 17 are transmitting. At the last instant of the cycle, shown in FIG. 5c, the sources of rank 5, 10, 15 and 20 transmit. In this example, the emission cycle of the different sub-assemblies connects the emissions in the order of the rank of the first source of each sub-assembly. It is also possible to send the subsets in other orders, for example, by first sending the subsets whose first source has an odd rank then the subsets whose first source has an odd rank. peer. This makes it possible to limit the remanence in the reading effected by the detector 14.

The successive transmissions produced by the different sources, whether this transmission is individual, a single source at a time, or collective, that is to say by subset, can also be implemented with the device 70 In which, it is also advantageous not to simultaneously transmit sources that are too close to each other. In the case of emissions by subsets, each of them may include sources belonging to the same direction or to different directions.

In addition to the successive transmissions, it is advantageous to synchronize the detector thereon. More precisely, as indicated above, the detector 14 comprises photosensitive elements organized in a matrix of rows and columns. The name row and column being purely conventional, subsequently, we will use the term row which can be applied either to a row or to a column.

The detector connects an acquisition phase followed by a reading phase of the matrix. Reading can be done row by row. By orienting the detector 14 so that the orientation of the reading rows coincides with the orientation of the planes of the beams 20, it is possible to read only the row or rows closest to the plane of the beam 20 and more precisely of the rows illuminated by the beam or beams 20 emitting simultaneously. Thus, the ionizing rays deflected by the object to be radiographed, essentially forming the scattered radiation, can be ignored when reading the matrix. More generally, a spatial and temporal synchronization of the sources 16 and of the detector 14 is carried out.

In computed tomography, it is necessary to rotate the generator 12 or 72 and the detector 14 in order to carry out a 2D or 3D reconstruction of the object to be radiographed. The presence of several sources 16 emitting parallel beams makes it possible to carry out only one turn, or only a fraction of a turn to obtain the various cuts necessary for the reconstruction. For this purpose, the emission of the different sources 16 is combined with the rotation of the actuator 68. Different combination modes are possible. It is for example possible to rotate the actuator 68 incrementally and to cause all the sources 16 to emit successively between each increment of rotation. It is also possible to make smaller increments and to transmit from a source 16 or a subset of sources 16 between each increment. It is also possible to rotate the actuator 68 continuously and during its rotation perform as many emission cycles as necessary. In practice, during continuous rotation, it is possible to consider that during an emission, the actuator 68 is almost static. 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 moving elements. In fact, in the event of incremental movement of the actuator, each stop and each start of the actuator generates jolts degrading the positioning accuracy of the arm 64. The continuous movement of the actuator 68 makes it possible to limit these to -blows. Preferably, the continuous movement of the actuator 68 takes place in a uniform manner, that is to say at a constant speed, which completely eliminates any jerking. Intermediate, while maintaining a continuous movement of the actuator 68, it is possible to slow down its movement during each emission from a source 16 and to accelerate it between two emissions.

It is also possible to implement a device according to the invention not having an actuator. In other words, the generator 12 or 72 and the detector 14 remain fixed relative to the support 62. This device is useful for radiographing objects capable of generating a strong diffusion by Compton interaction, for example in the medical field for carrying out pulmonary radiology. This type of radiology is generally performed using a generator emitting a conical X-ray beam. The generator is associated with a flat detector where the scattered radiation can only be distinguished from the useful information with an anti-scattering grid; grid whose efficiency is medium and imposes a higher dose of ionizing rays on the patient. By implementing the invention, it is possible to transmit successively by the different sources 16. By synchronizing in time and space the detector 14 and the generator 12 or 72, it is possible to avoid the detection of scattered radiation. In practice, a complete emission cycle by all the sources of the device can be fast enough to be considered instantaneous and thus obtain an almost instantaneous image of the object to be radiographed.

FIG. 6 again represents the radiology device 10 to illustrate the means enabling it to produce an image. The device comprises a computer 90 configured to produce a two-dimensional image 92 of an object to be radiographed located in the useful volume 60. Each source, identified here 16-1 to 16-7, emits a beam 20 in the direction of the detector 14 As described above, the transmissions from the different sources 16-1 to 16-7 are advantageously carried out sequentially. Each beam 20 is received by a region of the detector 14, forming a strip of pixels of the detector 14 placed opposite each beam 20. The bands are marked 14-1 to 14-7 with reference to the sources 16-1 to 16-7. opposite.

The computer 90 is configured to collect information from each band 14-1 to 14-7. To establish a two-dimensional image 92, the computer 90 is configured to juxtapose the information coming from the different bands 14-1 to 14-7 of the detector 14. To produce a two-dimensional image 90, the actuator 68 remains inactive. The assembly formed by the generator 12 and the detector 14 is stationary relative to the support 62. The image capture is similar to that produced by a conventional two-dimensional radiology device or by a device of the CBCT type without rotation. The main advantage of implementing the device 10 according to the invention is to reduce the effects of scattered radiation. In fact, each band 14-1 to 14-7 only detects the radiation contained in the plane of the beam 20 coming from the corresponding source 16-1 to 16-7 and ignores the radiation scattered outside this plane. More precisely, a band 14-i is defined to receive the direct radiation coming from the corresponding source 16-i. The band 14-i is completely illuminated by the direct radiation coming from the corresponding source 16-i. Direct radiation is understood to mean radiation without scattered radiation. By design of the device, each of the bands is aligned with the beam 20 coming from the corresponding source. In this way, the pixels of each band essentially receive direct radiation from the corresponding source. Only a very small part of the scattered radiation coming from this same source and propagating in the plane of the beam will reach the pixels of this band. Most of the scattered radiation propagates outside the beam plane and therefore does not reach the pixels of the band concerned. As will be seen below, this large part of the scattered radiation can be detected by other pixels of the detector located outside the band concerned. The bands advantageously have a width less than the width of the beam at the level of the detector in order to limit as much as possible the detection of scattered radiation coming from the beam in question and propagating away from the plane of the beam. As we have seen previously, the beams can overlap slightly. In this situation, it is advantageous to temporally shift the emission from immediately neighboring sources, for example as illustrated with the aid of FIGS. 5a to 5c. Also in this situation, the detector bands can also overlap. The synchronization of the reading of the tapes with the emission of the corresponding sources makes it possible to read each in turn all the tapes. Using overlapping bands makes it possible to widen the width of each band and therefore to receive a greater signal amplitude. The bands form zones of the detector allocated temporally to the reading of the flow of photons coming from each source. The time allocation is synchronized with the emission of the sources. When controlling the emission by the different sources, it is advisable to avoid that a band cannot receive direct radiations other than that coming from the source which is associated with it. It is possible to further improve the quality of the image. In fact, each band of the detector 14 receives radiation scattered in the plane of the beam 20 itself and it is advantageous to correct the measurement made by the detector 14 in each of the bands 14-1 to 14-7 to reduce the part due to the radiation. broadcast. In each of the bands 14-1 to 14-7, it is possible to estimate this part from measurements made outside the band considered. Indeed, during the emission of the beam 20 opposite the band considered, only this band receives the useful signal coming from the beam 20 having passed through the object to be radiographed. Outside this band, and outside other bands facing simultaneously activated beams 20, only a scattered radiation when passing through the object to be radiographed reaches the detector. By means of measurements made by the detector outside the band considered, it is possible to estimate the scattered radiation present in the band itself. The correction of the measurement carried out in the band is then possible, by subtracting the estimate of the scattered radiation from the measured radiation.

Figure 7 illustrates several ways of estimating the scattered radiation present in a band illuminated by a beam 20 and referenced 14-i. As a first approach, it is possible to consider that the scattered radiation is constant along an axis 100 perpendicular to the greatest length of the band 14- i. We choose a pixel or a group of pixels 100-1 of the detector 14 located outside the band 14-i. The level of scattered radiation within band 14-i is considered to be equal to the level of scattered radiation measured by pixel 100-1 when irradiating an object to be radiographed. For all the pixels located in the band 14-i along the axis 100, we subtract from the measurement made, the value measured by the pixel 100-1.

It is also possible to choose two pixels or two groups of pixels 100-1 and 100-2 both located outside the band 14-i. The pixels 100-1 and 100-2 are arranged on either side and at an equal distance from the strip 14-i. It is understood that during the emission of the beam 20, the pixels 100-1 and 100-2 are not illuminated by other beams 20. The estimate of the radiation diffused inside the band 14-i is then equal to the average of the measurements in each of the pixels 100-1 and 100-2. These measurements are carried out for all the axes perpendicular to the greatest length of the strip 14-i. All the measurement pixels are arranged on axes 102-1 and 102-2 parallel to the greatest length of the strip 14-i. The spatial variation of the scattered radiation being generally slow, it is possible to smooth the measurements made for all the points of type 100-1 on the one hand and 100-2 on the other hand along their axis 102-1 and 102-2 respective.

It is possible to refine the estimate of the level of scattered radiation present in the 14-i band by means of a scattered radiation decay model away from the 14-i band. The decay is a function of the distance to the band 14-i along the axis 100. This decay model can be defined empirically by measurements made from control objects of a nature close to real objects that l 'we want to X-ray. Once the measurements necessary to establish the model have been made, it is possible to approximate them, for example using a polynomial or trigonometric function. From a selected model, it is possible to estimate the level of scattered radiation inside the band 14-i by entering into the model measurements made outside the band, measurements made during irradiation of d. 'an object to be radiographed. During an x-ray, the measurements made by pixels 100-1 and 100-2 are introduced into the model used to estimate the level of radiation scattered inside the band 14-i, along the axis 100 As previously, measurements outside the band 14-i are carried out on the axes 102-1 and 102-2 in order to carry out the corrections for all the pixels of the band considered. The use of such a model makes it possible to refine the correction of scattered radiation by individualizing the correction of each of the pixels of the band considered.

The measurement correction making it possible to limit the effects of scattered radiation can be implemented in a radiology system having only one source 16. In other words, it is advantageous to implement this type of correction in a CT-scanner.

In addition, the computer 90 can be configured to produce a three-dimensional image 94 of an object to be radiographed located in the useful volume 60. To produce a three-dimensional image, it is possible to construct cross-sections of the object in planes formed by each of the beams 20. These sections are constructed from information received from the detector by rotating the generator 12 and the detector 14 around the support 62. The three-dimensional image is obtained from the images. different cuts. To carry out this type of reconstruction, it is possible to implement algorithms usually implemented in CT-scanner type devices. The main advantage in implementing the device 10 according to the invention is then the reduction in the mass to be rotated.

Alternatively, it is possible to construct a three-dimensional image 94 from several two-dimensional images as described above. Between each two-dimensional image, the generator 12 and the detector 14 are rotated around the support 62 by means of the actuator 68. The construction of the three-dimensional image can be carried out by implementing an algorithm usually implemented. in CBCT type devices. The main advantage of implementing the device 10 according to the invention here is the reduction of the effects of the radiation diffused in each two-dimensional image, which improves the quality of the three-dimensional image 94.

Claims

A radiology device comprising a generator (12; 72) of ionizing rays and a detector (14) configured to detect the rays emitted by the generator (12; 72), the generator (12; 72) and the detector (14). being opposite one another, the device (10) delimiting a useful volume (60; 80), crossed by the ionizing rays 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 substantially flat and d-shaped ionizing rays 'fan towards the detector (14), in that the sources (16) are arranged so as to irradiate the whole of the useful volume (60;

80) without translation, in that it comprises a computer (90) configured to produce a two-dimensional image (92) of an object to be radiographed located in the useful volume (60) without relative movement between the generator (12) and the detector (14), the calculator (90) being configured to collect information from the detector (14) along bands (14-1 to 14-7) of the detector (14), each band (14-1 to 14 -7) being arranged opposite one of the beams (20) and to establish the two-dimensional image (92) by juxtaposing the information coming from the different bands (14-1 to 14-7) of the detector (14).

2. Device according to claim 1, characterized in that the computer (90) is configured to estimate the radiation scattered in each of the bands (14-1 to 14-7) as a function of radiation measured by the detector (14) outside the band concerned (14-i) and to subtract the estimate of the scattered radiation from the measurements made by the detector (14) in the band concerned (14-i).

3. Device according to claim 2, characterized in that the computer (90) is configured to perform an estimate of the scattered radiation in each of the bands (14-1 to 14-7) as a function of a scattered radiation decay model. away from the band concerned (14-i).

4. Device according to one of the preceding claims, characterized in that it comprises a support (62) capable of carrying an object to be X-rayed and an actuator (68) making it possible to move an assembly formed by the generator (12; 72) and the detector (14) around the support (62) and in that the computer (90) is configured to produce a three-dimensional image (94) of an object to be radiographed located in the working volume (60) from several two-dimensional images (92) made in moving between each two-dimensional image (92) the assembly formed by the generator (12; 72) and the detector (14) around the support (62).

5. Device according to one of the preceding claims, characterized in that the detector (14) is formed of a flat panel extending along two perpendicular axes (32, 34), a first (32) of the two axes being parallel. to the direction (18) in which the sources (16) are distributed, a second (34) of the two axes belonging to a plane in which one of the beams (20) propagates.

6. Device according to one of the preceding claims, characterized in that the planes in which the beams (20) propagate are mutually parallel.

7. Device according to one of the preceding claims, characterized in that each source (16) comprises a cold cathode (24) emitting an electron beam (30) by field effect.

8. Device according to claim 7, characterized in that at least several of the sources (16) have a common vacuum chamber (22).

9. Device according to one of the preceding claims, characterized in that the generator (72) comprises several series of sources (16) aligned, each series being aligned along a direction (74, 76, 78) and each emitting a substantially flat beam (20) of ionizing rays, the planes of each of the beams (20) being mutually parallel.

10. Device according to claim 9, characterized in that the directions (74, 76,

78) of each of the series of sources (16) are mutually parallel.

11. A method implementing a device (10; 70) according to one of the preceding claims, characterized in that it consists in successively linking the transmission of several of the sources (16).

12 The method of claim 11, characterized in that the sources (16) are ordered along their direction (18; 74, 76, 78) and grouped into subsets each grouping together equally distributed sources, the subsets being nested into each other and in that it consists in controlling the simultaneous transmission of the sources of the same subset and successively linking the transmission of the different subsets.

13. Method according to one of claims 11 or 12, characterized in that it consists in spatially and temporally synchronizing the sources (16) and the detector (14).

14. The method of claim 13, characterized in that it consists in synchronizing the emission of each source (16-i) with an allocation of the corresponding band (14-i) of the detector (14).

15. Method according to one of claims 11 to 14 implementing a device according to claim 4, characterized in that it consists in combining the emission of the different sources (16) and the movement of the actuator (68). .

16. The method of claim 15, characterized in that it consists in moving the actuator (68) continuously during the emission of the various sources (16).