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    • 专利摘要:
    Radiographic imaging system, comprising: - an X-ray emission unit (2); - a reception unit (3) of X-rays; and a plate (11) made of an X-ray opaque material and located between the transmitting unit (2) and the receiving unit (3), the plate (11) comprising at least four channels (20 to 23), each channel allowing part of the X-rays emitted by the transmitting unit (2) to pass through the channel; and an image processing unit (4) configured to determine the coordinates of the projected patterns (M1 to M4) and to calculate a position of the reception unit (3) from the coordinates of the projected patterns (M1 to M4). ) and channel coordinates (20 to 23).
    公开号:FR3028039A1
    申请号:FR1460687
    申请日:2014-11-05
    公开日:2016-05-06
    发明作者:Yannick Grondin；Philippe Augerat；Philippe Cinquin；Laurent Desbat
    申请人:Surgiqual Inst；Universite Joseph Fourier (Grenoble 1)；Centre Hospitalier Universitaire de Grenoble；
    IPC主号:
    专利说明:

    [0001] FIELD OF THE INVENTION The invention relates to radiographic imaging, especially X-ray imaging, and more particularly to mobile radiographic imaging in the medical field, in particular dental. STATE OF THE ART Currently, mobile radiography systems are used to produce radiographic images, in particular radiographic images in a patient's bed. These mobile systems comprise an X-ray unit and an X-ray unit, and these elements are placed on either side of an object, such as a patient, a container, or any other object. for which it is desired to make a radiographic image in order to examine the object. These mobile systems are manipulated by an operator and can misalign, which can produce an image with contrast and / or deformation defects of the object. In this case, the image is difficult to exploit. Some X-ray systems provide means for aligning the transmitting unit with the receiving unit.
    [0002] There may be mentioned, for example, US patent applications US2012 / 0230473, US2013 / 0051528 and French patent application FR2899349, which disclose an X-ray radiographic imaging system using a magnetic positioning device comprising an emitter of electromagnetic waves. located on the X-ray emission unit and a wave receiver located on the receiving unit. But such systems require an electromagnetic wave transmitter / receiver device in addition to the transmit unit / X-ray receiver unit unit, which makes the imaging system bulky. Moreover, the electromagnetic radiation of the positioning device can be disturbed by nearby devices. US2002 / 0150215 discloses an X-ray imaging system using an optical, or ultrasonic, or magnetic camera, located on the X-ray unit and markers placed on the receiving unit. . The camera produces an image of the markers to determine the position of the receiving unit. But the field of view of an optical or ultrasonic camera can be obstructed by the object to be analyzed. In addition, magnetic cameras may be disturbed by nearby metal objects. US patent application US2007 / 0223657 discloses a method of aligning a transmitter and an X-ray detector displaceable by motorized moving means. The method includes placing the detector in an initial position and, with the aid of the detector, generating a map, in one or more dimensions, of the radiation profile including regions of interest that are identifiable by their intensity level. radiation. Then, the detector is moved to other positions and the new radiation profiles and their coordinates in space are recorded. Once the radiation profile map is obtained, it can be used to align the source and detector. But such a method requires to perform many radiographic images and to be able to move the detector along the axis of propagation of the radiation, which is not always possible when the detector is placed beneath the bed of a patient, especially when a chest X-ray of a bedridden person. U.S. Patent Application US2002 / 0080922 discloses an X-ray radiographic method using a receiving unit comprising an X-ray detector and an anti-scattering gate located on the detector, the grid comprising pairs of radiopaque alignment bars. X. In this method, a first image of the object is produced, with a radiation delivering a low dose of X-rays, then the relative position of the alignment bars in the first image is measured, the relative angle of the detector with respect to the emission unit, and a second image is produced with radiation delivering a high dose of X-rays, for a radiographic image. But this method requires the use of an anti-diffusion grid located on the detector, which is not always the case, especially in dental radiology which uses intra-oral detectors that do not include a grid. Moreover, in the case where the grid is focused, the method does not make it possible to determine the distance between the reception unit and the transmission unit which must then be equal to the focal length of the grid.
    [0003] Reference may also be made to US patent application US2006 / 0280293 which discloses an X-ray radiographic imaging system using an X-ray opaque reticle placed on the X-ray emission unit. The reticle comprises one or more openings which pass a portion of the X-rays, to obtain an image comprising the specific projection of a single pattern of the openings. Then the image is displayed using a screen and a distance is measured between the edge of the pattern and the edge of the screen to determine if the receiving unit is centered relative to the unit of the screen. program. However, the document gives no information on the X-ray dose delivered. In addition, the system only allows to center the receiving unit and does not offer the possibility of precisely positioning the receiving unit. OBJECT OF THE INVENTION An object of the invention consists in overcoming the drawbacks mentioned above, and in particular in providing means for facilitating the positioning of the reception unit with respect to the transmission unit of a Another object is to limit the X-ray doses used when positioning the reception unit with respect to the emission unit. According to one aspect of the invention, there is provided a radiographic imaging system, comprising: - an X-ray emission unit; - an X-ray reception unit; and a plate made of an X-ray opaque material and located between the transmitting unit and the receiving unit. The plate has at least four channels, each channel allowing part of the X-rays emitted by the transmitting unit to pass through the channel; the receiving unit generates an alignment radiographic image having a projected pattern of each channel; and the system includes an image processing unit configured to determine the coordinates of the projected patterns in the alignment image and to calculate a position of the reception unit from the coordinates of the projected patterns in the image of the image. alignment and channel coordinates. The image processing unit may further comprise a memory for storing parameters of a first geometric transformation matrix connecting coordinates of the reference patterns with respectively the coordinates of the channels, each reference pattern corresponding to a projection of a channel in a reference radiographic image generated when the receiving unit is located at a reference distance from the receiving unit, the processing unit being further configured to identify the projected pattern in the radiographic image of aligning each channel, to match the projected patterns in the alignment radiographic image with the channels of the plate respectively, to calculate parameters of a second geometric transformation matrix connecting the coordinates of the projected patterns in the radiographic image with the coordinates of the reference patterns, and to calculate the position of the unit of receiving from the parameters of the first and second matrices.
    [0004] The plate may comprise several channels forming an asymmetric figure. The plate may comprise at least two channels aligned along a first axis, at least two channels aligned along a second axis perpendicular to the first, and at least three channels aligned along a third axis inclined relative to the first and second axes. The transmitting unit and the receiving unit can be mobile.
    [0005] Thus, a mobile X-ray imaging system is provided which is particularly suitable for chest radiography performed in a patient's bed and for dental X-ray. The channels may have a cylindrical shape.
    [0006] The sections of the channels may have different diameters between them. According to another aspect, there is provided a method for positioning a radiographic imaging system comprising an X-ray emission unit and an X-ray reception unit, the method comprising the following steps: arranging a realized plate in an X-ray opaque material, between the transmitting unit and the receiving unit, the plate comprising at least four channels, each channel allowing part of the X-rays emitted by the transmitting unit to pass to through the canal; - emit X-rays by the emission unit; generating, by the reception unit, an alignment radiographic image comprising a projected pattern of each channel; - determine coordinates of the projected patterns in the alignment radiographic image; and calculating a position of the reception unit from the coordinates of the projected patterns in the alignment radiographic image and channel coordinates.
    [0007] The calculation step may further comprise a calibration step in which a reference radiographic image is generated by the reception unit located at a reference distance from the transmission unit, and includes a projected reference pattern of each channel, the coordinates of the reference patterns are determined, and parameters of a first geometric transformation matrix connecting the coordinates of the reference patterns to the coordinates of the channels are calculated, a step of identifying the projected pattern in the image radiographic alignment of each channel, a step of matching the projected patterns in the alignment radiographic image with respectively the channels of the plate, a step of calculating the parameters of a second geometric transformation matrix connecting the coordinates of the projected patterns in the radiographic alignment image with the coordinates of the reference patterns, the position of the u receiving unit being determined from the parameters of the first and second matrices. The calculation step may further comprise a calculation of the orientation angles of the receiving unit from the parameters of the first and second matrices. Other advantages and features will become more clearly apparent from the following description of particular embodiments and implementations of the invention given by way of nonlimiting examples and represented in the accompanying drawings, in which: which: - Figure 1 schematically illustrates an embodiment of a radiographic imaging system according to the invention; and FIGS. 2 to 5 schematically illustrate embodiments of a plate according to the invention. DETAILED DESCRIPTION FIG. 1 shows a radiographic imaging system 1, comprising an X-ray emission unit 2, an X-ray reception unit 3, a plate 11, and a radiation treatment unit 1. image 4. The imaging system 1 is intended to produce a radiographic image of an object 5, for example a patient, a bottle, a portion of a tube, and in particular an area of interest of the object 5 to examine.
    [0008] The emission unit 2 can be, for example, an X-ray tube. The emission unit 2 comprises a housing 6 in which are housed a source 7 of X-rays and a diaphragm 8. The diaphragm 8 delimits a irradiated zone 8a generally having a rectangular, circular or octagonal shape.
    [0009] The diaphragm 8 can open and close to vary the amount of X-radiation to the receiving unit 3. The source 7 produces X-ray radiation, which passes through the irradiated zone 8a of the diaphragm 8, towards the The reception unit 3. The X-ray beam is shown schematically by the reference A3. The reception unit 3 comprises an X-ray detector 9, and may comprise an anti-diffusion gate 10 for reducing the scattered X-rays and improving the contrast of the images. The grid 10 may be focused, i.e. it may comprise bars oriented towards a focal point, or it may be unfocused when it comprises parallel bars. The reception unit 3 can be positioned so that the incidence of X-rays is normal to the reception unit 3. In this case, a longitudinal axis Al of the reception unit 3 is perpendicular to a propagation axis A2 of the X-radiation emitted. Moreover, for some examinations, it is possible to use an oblique incidence of the X-ray radiation, and in this case the longitudinal axis Al is inclined by an angle A different from 90 ° with respect to the axis of propagation A2. For example, the receiving unit 3 may be tilted to view certain areas of the object 5 that are masked when using a 90 ° X-ray angle. In addition, the transmission unit 2 and the reception unit 3 are movable in translation and in rotation, and are displaceable manually, or by displacement means, respectively represented by the references 12 and 13. The displacement means 12, 13 may be manual or automated micrometric actuators for moving the emission 2 and reception 3 units of the imaging system 1. Alternatively, the transmission unit 2 can be moved in an automated manner and receiving unit 3 can be moved manually by an operator.
    [0010] The processing unit 4 cooperates with the plate 11 so as to improve the alignment of the reception unit 3 with respect to the emission unit 2. It is meant by aligning the reception unit 3, the operation which consists in positioning and orienting the reception unit 3 with respect to the emission unit 2, or vice versa, so as to produce an exploitable radiographic image, that is to say an image whose contrast level allows a user to visualize the areas of interest of the object 5 to be analyzed. In order to align the reception unit 3 with respect to the emission unit 2, the object 5 to be examined is placed between the reception unit 3 and the emission unit 2, and then the plate is placed. 11 on the emission unit 2, and a first IR radiographic image, noted alignment image. The embodiment of the IR alignment image consists in emitting an X-ray radiation, by the emission unit 2, in the direction of the reception unit 3, and then detecting, by the reception unit 3, the X-radiation to generate the IR alignment image. The obtained IR alignment image makes it possible to determine the position and the orientation of the reception unit 3 with respect to the emission unit 2. Since the realization of the IR alignment image is carried out when the object 5 is placed between the receiving unit 3 and the transmitting unit 2, it is advantageous to make a plate 11 which limits the X-radiation received by the object 5 during the alignment step elements 2, 3 of the imaging system 1. In addition, the plate 11 must make it possible to generate an exploitable IR alignment image for accurately determining the position and the orientation of the reception unit 3.
    [0011] The plate 11 is made of an X-ray opaque material, for example lead or tungsten. The plate 11 has, for example, a thickness of at least 3 mm to stop almost all the photons having an energy used in conventional radiology. The plate 11 is located between the emission unit 2 and the reception unit 3, on the path A3 of the X-rays emitted by the emission unit 2. The plate 11 is preferably mounted on the tube 2 to For example, the plate 11 is housed in the housing 6 of the tube 2. Advantageously, the plate 11 is located in the housing 6 so that the diaphragm 8 is placed between the plate 11 and the source 7 of X-rays.
    [0012] The plate 11 is intended to receive an X radiation emitted by the emission unit 2 in order to be able to align the reception unit 3 with the emission unit 2. The plate 11 comprises at least four channels 20 to 23. Each channel 20 to 23 allows part of the X-rays emitted by the transmitting unit 2 to pass through the channel 20 to 23. A channel 20 to 23 may be an opening, such as a hole or slot, filled or However, the channel 11 comprises only four channels 20 to 23, thus reducing the amount of X-rays emitted towards the X-ray. In general, the diameter of the channels 20 to 23 is less than the length of the plate 11. The diameter of at least one channel may be greater than that of the other channels of the plate 11. Preferably, the plate 11 is located perpendicular to the axis of propagation A2 X-rays so that the channels 20 to 23 are oriented towards the source 7 to obtain a projection of the channels in the IR alignment image which is not deformed. FIGS. 2 to 6 show several embodiments of the plate 11. FIG. 1 shows a front view of the plate 11 comprising four channels 20 to 23, preferably four circular section openings, that is, the channels 20 to 23 have a cylindrical shape. The channels 20 to 23 are located at specific positions in the plate 11 so that the figure formed by the four channels 20 to 23 is asymmetrical. For example, the channels 20 to 23 are cylindrical and their sections have different diameters between them. In the example illustrated in Figure 1, the channels 20 to 23 have the same cylindrical shape and have different diameters. Thus, the channels 20 to 23 are differentiated by their size. In FIG. 2, the plate 11 comprises four channels 20 to 23, in particular four openings with a circular section. The channels 20 to 23 are located at specific positions in the plate 11 so that the figure formed by the four channels 20 to 23 is asymmetrical. In addition, the channels 20 to 23 have the same length L, that is to say that their sections have the same diameter. Thus, the channels 20 to 23 are differentiated by their position on the plate 11.
    [0013] In Figure 3, the plate has four channels 20 to 23 cylindrical arranged to form an asymmetrical figure. Preferably, the distances separating the channels 20 to 23 are distinct so as to distance a channel 22 from the two first ones 20, 21. Preferably, the arrangement of the channels 20 to 26 within the plate 11 forms an asymmetric figure. An asymmetrical pattern makes it possible to obtain, in the IR alignment image, projected patterns from the channels that are located at distinct distances from one another. The distinct distances obtained may facilitate the matching of the projected patterns with the channels of the plate 11.
    [0014] In FIG. 4, the plate 11 comprises three zones Z1 to Z3, each zone comprising several channels, and a cylindrical channel 23 distinct from those of the zones. The three zones Z1 to Z3 each comprise six cylindrical channels arranged symmetrically to form a circle. A zone Z1 to Z3 comprising six channels makes it possible to reduce the dose of x-rays emitted with respect to a single channel that would surround the six channels. It may be noted that each zone Z1 to Z3 forms a symmetrical figure, however, the arrangement of the zones Z1 to Z4 forms an asymmetric figure.
    [0015] In FIG. 5, the plate 11 comprises fourteen channels 20 to 33. In particular, the plate 11 comprises a first group of seven channels 20 to 26 aligned along a first axis B1, a second group of four channels 27 to 30 aligned according to a second axis B2 perpendicular to the first axis B1, and a third group of three channels 31 to 33 aligned along a third axis B3 inclined at an angle B relative to the first and second axes B1, B2. In addition, the four channels 27 to 30 of the second group are aligned along the second axis B2 with the third channel 22 of the first group, starting from the left in FIG. 5. The three channels 31 to 33 of the third group are also aligned. along the third axis B3 with the third channel 22 of the first group. For example, the angle B is equal to 45 °. Each line of channels may comprise several channels. In this embodiment, the channels 20 to 33 have a circular section and have the same diameter. In particular, the plate 11 has more than four channels when it is desired to align the transmission unit 2 with the reception unit 3 in complex situations, for example in the case where the object 5 is bulky, or when the amount of X-radiation emitted is low. In addition, the fact of aligning channels along three distinct axes B1 to B3 makes it possible to improve the robustness of the image processing by improving the determination of the coordinates of the patterns projected in the image.
    [0016] The image processing unit 4 makes it possible to determine the position and the orientation of the reception unit 3 of the imaging system 1. The image processing unit 4 is coupled to the reception unit 3 The processing unit 4 is either integrated within the detector 9, or located outside the detector 9 being electrically connected to the detector 9 by wired or wireless connection. The detector 9 receives the X-radiation emitted by the emission unit 2, and generates an X-ray image of IR alignment corresponding to the X-radiation received by the detector 9. The IR alignment image generated by the detector 9 comprises the respective projections of the channels 20 to 23 of the plate 11, that is to say the projected patterns M1 to M4 channels 20 to 23. In addition, the detector 9 transmits the images generated by electrical signal to the unit 4 which determines the position and the orientation of the reception unit 3 with respect to the transmission unit 2. The determination of the position and the orientation of the reception unit 3 is carried out from known algorithms of image processing integrated in the processing unit 4. In general, the processing unit 4 determines the coordinates of the projected patterns M1 to M4 in the image of alignment IR, then determines a position of the reception unit 3 from the coor determined data and coordinates of the channels 20 to 23. In addition, the processing unit 4 can also determine an inclination of the receiving unit 3 relative to an axis perpendicular to the plate 11. More particularly, the unit of processing 4 includes a memory for storing parameters of a first geometric transformation matrix Kref. The geometric transformation associated with the first matrix Kref corresponds to a projection of the coordinates of the channels 20 to 23 of the plate 11 in a reference radiographic image. In other words, the first matrix Kref makes it possible to connect the coordinates of a projected pattern in the reference image with those of the channel 20 to 23 of the plate 11 which generated the projected pattern. The patterns projected in the reference image are also referred to as reference patterns. The reference patterns are obtained by positioning the reception unit 3 at a reference distance Dref of the reception unit and by generating the reference radiographic image of the plate 11. In particular, the unit receiving plane 3 in a reference orientation in which the plane of the receiving unit 3 is parallel to the plane of the plate 11, and perpendicular to the axis of propagation A2 of the X-rays. The reference radiographic image is also generated. with the plate 11 located in the housing 6 of the emission unit 2 and without the object 5 to be studied. Thus, the reference image comprises the respective projected patterns of the channels of the plate 11. It is then possible to write, for a channel 20 to 23 of the plate 11 and for the projected pattern of the channel 20 to 23 in the radiographic image of reference, the following relation: Qref = Kref x P with: - Kref: the first geometric transformation matrix; P: a coordinate matrix of a channel 20 to 23 of the plate 11; and Qref: a matrix of the coordinates of the reference pattern corresponding to the projection of the channel 20 to 23 in the reference radiographic image.
    [0017] Then, the processing unit 4 determines the coordinates of a reference pattern, and calculates the parameters of the first matrix Kref from the relation Qref = Kref x P, that is to say from the coordinates of the reference pattern, expressed by the matrix Qref, and coordinates of the channel associated with the reference pattern, expressed by the matrix P. The processing unit 4 can also calculate the parameters of the first matrix Kref, for each reference pattern and for each channel associated with the reference pattern, and compare the values of the parameters obtained for each calculation. To simplify the calculations, the coordinates of a point in a radiographic image, reference or alignment, are expressed according to a two-dimensional image reference defined by two orthonormal vectors U, V and an origin point O. The reference image is linked to radiographic reference and alignment images. A three-dimensional object marker is also defined comprising three orthonormal vectors X, Y, Z and an origin point I, in which the coordinates of the channels are expressed. The object marker is linked to the source 7. In addition, when the plate 11 is placed in the housing 6, the plate 11 is secured to the source 7, and the object marker is also connected to the plate 11. The coordinates of the channels 20 to 23 of the plate 11 are expressed in the object reference. The coordinates of the channels 20 to 23 are previously recorded in the memory of the processing unit 4. In general, the coordinates of a channel 20 to 23 correspond to the coordinates of the center of gravity of a section of the channel 20 to 23. More particularly , the centroid chosen to determine the coordinates of the channel 20 to 23 is the centroid of a section of the channel located at the surface of the plate 11 placed opposite the source 7. In addition, the orientation of the plate 11 in the object repository is also stored in the memory. Preferably, the plate 11 has a 90 ° orientation with respect to the X-ray propagation axis. For example, the matrix Kref can be written in the following way: kxDref 0 Kref = 0 kxDref U01 VO 0 0 1 with : - Dref: the reference distance of the reception unit 3, expressed in meters; - k: a conversion factor from meter to pixel, the value of which depends on the type of detector 9 and whose unit is in pixels per meter; - UO, VO: coordinates, in the image frame, of a point of the reference image corresponding to the orthogonal projection of the X-ray source 7. The other matrices can also be written in the following way: 'Qref = [Vm1 0 with - Um1, Vm1: the coordinates of a reference pattern in the image reference; and Xcll P = [Ycl Zcl-Xc1, Yc1, Zc1: the coordinates of a channel in the object reference. To determine the positioning of the reception unit 3, the IR alignment image is generated with the same plate 11 for which the parameters of the first geometric transformation matrix Kref have been determined, and with the object 5 to be analyzed. located between the reception unit 3 and the emission unit 2. From the radiographic alignment image IR, the processing unit 4 identifies the projected patterns M1 to M4 in the alignment image IR using known image processing algorithms to detect the contours of the projected patterns M1 to M4. The same algorithms can be applied to the reference image to identify the reference patterns. For example, Canny filters can be used. The gray alignment thresholding algorithm can be pre-applied to the IR alignment image to provide a simplified image for improved edge detection. In addition, filtering may be applied to the IR alignment image to suppress the isolated pixels, i.e., to suppress the noise of the image. Then, image processing algorithms configured to determine the characteristics of each projected pattern can be applied to identify the patterns. Features include, but are not limited to, the shape, length, and coordinates of the projected pattern in the IR alignment image. For example, a Hough transform function can be applied to determine the characteristics of the projected patterns M1 to M4. When the channels 20 to 23 are cylindrical, the projected patterns M1 to M4 are circles or ellipses. In this case, the coordinates of the pattern are those of the center of the circle or ellipse. In general, the coordinates of a pattern correspond to the coordinates of the centroid of the pattern. The other characteristics of the patterns M1 to M4 are the diameters of the circles, the small and large axes of the ellipses. Then, the processing unit 4 matches the identified patterns M1 to M4 with the associated channels 20 to 23 of the plate 11. In other words, the processing unit 4 matches the projected patterns M1 to M4 using a table of characteristics stored in the memory of the processing unit 4. For example, the table comprises the characteristics of the channels 20 to 23 of the plate 11, namely their shape, their length and their position in the plate 11 More particularly, the pairing consists in traversing the IR alignment image to identify the projected patterns M1 to M4, and for each identified projected pattern, the processing unit 4 calculates the characteristics of the pattern, such as, for example, its shape. , its length, and its position in the IR image. Then the processing unit 4 compares the calculated characteristics with those of the table and locates the channel of the plate that corresponds to the projected pattern. For example, a projected pattern corresponds to a channel of the plate when the calculated characteristics are proportional to those of the table. The proportionality corresponds to an enlargement or a narrowing, as a function of the position of the detector 9. Moreover, when the channels 20 to 23 have the same size, for example the same diameter, the pairing is performed according to the position of the sensors. patterns projected in the image, because the position of the patterns in the image makes it possible to differentiate them from each other. On the contrary, when the channels have different sizes, the matching is done according to the sizes of the projected patterns, because they are different from each other. Then, the processing unit 4 calculates, by known image processing algorithms, parameters of a second geometric transformation matrix H connecting the coordinates of the reference patterns with the coordinates of the projected patterns M1 to M4 in the Radiographic image of IR alignment. The second matrix H corresponds to a planar homography between the reference radiographic image and the radiographic image of IR alignment. This planar homography is mathematically represented by the second matrix H. For each pattern projected in the reference image, we can write the following relation: Qali = H x Qref with: - H: the second geometric transformation matrix; Qref: the coordinate matrix of the reference pattern corresponding to the projection of the channel 20 to 23 in the reference radiographic image; Qali: a coordinate matrix of the channel 20 to 23 projected in the alignment radiographic image. The processing unit 4 calculates the parameters of the second matrix from the relation Qali = H x Qref, that is to say from the coordinates of a pattern projected in the alignment image, expressed by the Qali matrix, and coordinates of the associated reference pattern, expressed by the matrix Qref. The pattern projected in the alignment image and the associated reference pattern are generated by the same channel of the plate 11. In addition, the coordinates of a projected pattern M1 to M4 can be connected in the alignment image. IR with the coordinates of the channel of the plate 11 which generated the projected pattern, from a third Kali matrix of geometric transformation. The third geometric transformation associated with the third matrix Kali corresponds to a projection of the coordinates of a channel 20 to 23 of the plate 11 in the IR alignment image. In other words, the third matrix Kali makes it possible to connect the coordinates of a projected pattern in the IR alignment image with those of the channel 20 to 23 of the plate 11 which generated the projected pattern.
    [0018] We can still write the following relation: Qali = Kali x Rali x P with: - Kali: the third matrix corresponding to the third geometrical transformation; and - Rali: a rotation matrix of the third geometrical transformation. From the relations described above, we obtain the following relation: Kali x Rali = H x Kref For example, we can write the third matrix Kali of the third geometrical transformation in the following way: k'xD 0 Kali = 0 k 'xD U01 VO 0 0 1 with: - k': another conversion factor from meter to pixel, whose value depends on the type of detector 9 and whose unit is in pixels per meter; D: a distance between the reception unit 3 and the transmission unit 2, expressed in meters, during the generation of the IR alignment image. The processing unit 4 calculates, from the product between the first and second matrices Kref, and H, the parameters of the matrices Kali and Rali. Then, the processing unit 4 calculates the position and orientation of the receiving unit from the calculated parameters. More particularly, the processing unit 4 calculates the distance D between the reception unit 3 and the emission unit 2. Furthermore, the rotation matrix Rali can be decomposed into three matrices, that is, say three other matrices each representing a rotation of the reception unit 3 with respect to an axis X, Y, Z of the object reference.
    [0019] The user can furthermore enter, by means of a graphic interface 14, a position, or a distance between the transmission unit 2 and the reception unit 3, and a desired inclination. The processing unit 4 then calculates the difference in position between the desired position and the determined position, as well as the difference in orientation between the desired orientation and the determined orientation. Using the calculated differences, the processing unit can provide position correction and orientation information. Then, from the position correction and orientation information obtained, it is possible to align the transmission unit 2 with the reception unit 3, manually by an operator, or automatically by means of 12, 13 which can be motorized and controlled by the image processing unit 4. In addition, the positioning device 4 may comprise a signaling unit 15, for example a screen, coupled to the processing unit 14. to indicate to the operator the values of the determined position and orientation. The signaling unit 15 may further indicate the initial distance determined by the processing unit 4. The signaling unit 15 may also indicate a displacement information, in translation and in rotation, to align the transmission unit. 2. Preferably, the displacement information corresponds to the displacement of the transmission unit 2 necessary to align it with respect to the reception unit 3. For example, the displacement information is that which makes it possible to move the transmission unit 2 so that the distance between the receiving unit 3 and the transmitting unit 2 is equal to an optimum distance provided by the manufacturer of the receiving unit 3. The optimum distance may be the focal length of the anti-diffusion gate 10 in the case where the reception unit 3 is equipped with such a gate. The housing 6 of the transmission unit 2 may further comprise displacement means 16 for placing and removing the plate 11 in an automated manner.
    [0020] When the reception unit 3 and the emission unit 2 are aligned, the plate 11 is removed, and a normal radiographic image of the object 5, denoted diagnostic image, is produced. In general, to determine the position and inclination of the receiving element 3, the projected patterns M1 to M4 of the IR alignment image must have a minimum diameter of 1 mm. In this case, when it is desired to carry out an IR alignment image with the reception unit 3 located at a distance from the transmission unit 2 for which the enlargement factor of the channels 20 to 23 of the plate 11 is equal, for example, to 10, a plate 11 will be made whose channels have a diameter greater than 100 gn. Thus, in the IR alignment image, projected patterns M1 to M4 having a diameter of about 1 mm are obtained, which allows their detection. When the receiving unit 3 has a smaller enlargement factor, for example for an imaging system used in the dental field for which the distances between the movable elements 2, 3 are reduced, a plate 11 which can be used is used. channels 20 to 23 having an identical shape, however, the diameter of each channel is less than 100, t, m. For example, the magnification factor may be 4 and the plate 11 used then has channels 20 to 23 each having a diameter of 50 gn. Depending on the X-ray detector used, the size of the channels is adapted to the type of detector, in particular according to the size of the pixels. In particular, the alignment image is performed with a low dose of X-rays. This low dose corresponds to about ten times less than a normal dose for producing a diagnostic X-ray image. Furthermore, the surface ratio between a plate-free irradiation field with open diaphragms, for example 20 cm x 20 cm, and the plate-field area where X-rays pass only through the channels is For example, for a diagnostic X-ray image requiring a PDS dose area product of the order of 100 cGy.cm2, the additional dose given to the patient during the alignment step is 10 x 10,000 times less, that is 10 microGy.cm2 in terms of PDS, which is negligible.
    [0021] To achieve the dimensions and patterns of the channels, a succession of radiographic images is carried out beforehand, in the presence of calibrated objects and in the absence of a patient to be analyzed. Simulation is performed by varying the diameter of the channels and recording the delivered X-ray dose required for detection of the projected patterns formed in the radiographic images obtained. In addition, the signal-to-noise ratio can be recorded according to the size of the object and the dose delivered. This gives a set of plates 11 respectively associated with different clinical situations, for example situations that require different doses of X-rays. This set includes plates 11 optimized to perform a specific radiographic image from a given imaging system. The imaging system 1 makes it possible to place a plate 11 according to the distance between the reception unit and the emission unit, and therefore the enlargement factor of the reception unit 3. Other parameters can be taken into account, for example the thickness of the area of interest of the object 5, the sensitivity of the reception unit 3, the contrast of the desired image ... One can also make a second image alignment to check the alignment of the receiving unit 3.
    [0022] The method of positioning the reception unit 3 with respect to the emission unit, or vice versa, can be implemented by the imaging system 1 defined above. In an initial step, the reception unit 3 and the transmission unit 2 are arranged so that the object 5 to be analyzed is situated between the emission unit 2 and the detector 9. The process comprises in addition the following steps: - arrange the plate 11 made of an X-ray opaque material, between the emission unit 2 and the reception unit 3, the plate 11 comprising at least four channels 20 to 23, each channel allowing part of the X-rays emitted by the transmitting unit 2 to pass through the channel; - emit X-rays by the emission unit 2; generating, by the reception unit 3, an alignment radiographic image comprising a projected pattern of each channel; - determine coordinates of the projected patterns in the alignment radiographic image; and calculate a position of the reception unit 3 from the determined coordinates and the coordinates of the channels.
    [0023] In addition, prior to the step of generating the alignment image, it is possible to generate a reference radiographic image so as to identify the geometrical transformations for connecting the coordinates of the channels with the projected pattern coordinates of the channels in the alignment image.
    [0024] When X-ray radiation is emitted, a low dose of X-rays is used, relative to the dose used to make a diagnostic x-ray image of the object 5.
    [0025] Thus, there is provided a radiographic imaging system and a system positioning method that minimizes the quantities of X-rays emitted while allowing radiographic images to be made without distortion. In addition, the number of images is reduced so as to limit a patient's exposure to X-rays. Such an imaging system is particularly suitable for environments comprising metallic objects that can disturb electromagnetic measurement systems. classic distances.
    权利要求:
    Claims (10)
    [0001]
    REVENDICATIONS1. Radiographic imaging system, comprising: - an X-ray emission unit (2); - a reception unit (3) of X-rays; and - a plate (11) made of an X-ray opaque material and located between the emission unit (2) and the reception unit (3), characterized in that: - the plate (11) comprises at at least four channels (20 to 23), each channel allowing part of the X-rays emitted by the transmitting unit (2) to pass through the channel; the reception unit (3) generates an alignment radiographic image (IR) comprising a projected pattern (M1 to M4) of each channel (20 to 23); and the system comprises an image processing unit (4) configured to determine the coordinates of the projected patterns (M1 to M4) in the alignment radiographic image (IR), and to calculate a position of the unit of receiving (3) from the coordinates of the projected patterns (M1 to M4) in the alignment radiographic image (IR) and channel coordinates (20 to 23).
    [0002]
    2. System according to claim 1, wherein the image processing unit (4) comprises a memory for storing parameters of a first geometrical transformation matrix connecting coordinates of the reference patterns with respectively the coordinates of the channels ( 20 to 23), each reference pattern corresponding to a projection of a channel (20 to 23) in a reference radiographic image generated when the reception unit (3) is located at a reference distance from the reference unit. transmission (2), the image processing unit (4) is further configured to identify the projected pattern (M1 to M4) in the alignment image (IR) of each channel (20 to 23), to match the projected patterns (M1 to M4) in the alignment radiographic image (IR) with the channels of the plate (11) respectively, to calculate parameters of a second geometric transformation matrix connecting the coordinates of the projected patterns (M1 to M4) in the alignment radiographic image (IR) with the coordinates of the reference patterns, and for calculating the position of the receiving unit (3) from the parameters of the first and second matrices.
    [0003]
    3. System according to claim 1 or 2, wherein the plate (11) comprises a plurality of channels forming an asymmetrical figure.
    [0004]
    4. System according to one of claims 1 to 3, wherein the plate (11) comprises at least two channels aligned along a first axis (A1), at least two channels aligned along a second axis (A2) perpendicular to the first , and at least three channels aligned along a third axis (A3) inclined with respect to the first and second axes (A2, A3).
    [0005]
    5. System according to one of claims 1 to 4, wherein the transmitting unit (2) and the receiving unit (3) are movable.
    [0006]
    6. System according to one of claims 1 to 5, wherein the channels have a cylindrical shape.
    [0007]
    7. System according to claim 6, wherein the sections of the channels have different diameters between them.
    [0008]
    8. A method for positioning a radiographic imaging system comprising an X-ray emission unit (2) and an X-ray reception unit (3), characterized in that it comprises the following steps: a plate (11) made of an X-ray opaque material, between the transmitting unit (2) and the receiving unit (3), the plate (11) comprising at least four channels (20 to 23), each channel allowing a portion of X-rays emitted by the transmitting unit (2) to pass through the channel; - emit X-rays by the emission unit (2); generating, by the reception unit (3), an alignment radiographic image (IR) comprising a projected pattern (M1 to M4) of each channel (20 to 23); - determining coordinates of the projected patterns (M1 to M4) in the alignment radiographic image (IR); and calculating a position of the receiving unit (3) from the coordinates of the projected patterns (M1 to M4) in the alignment radiographic image (IR) and channel coordinates (20 to 23).
    [0009]
    9. The method of claim 8, wherein the calculation step comprises a calibration step in which is generated, by the receiving unit located at a reference distance from the transmitting unit, a reference radiographic image. comprising a projected reference pattern of each channel (20 to 23), the coordinates of the reference patterns are determined, and parameters of a first geometric transformation matrix connecting the coordinates of the reference patterns with the coordinates of the channels are calculated ( 20 to 23), a step of identifying the projected pattern (M1 to M4) in the alignment radiographic image (IR) of each channel (20 to 23), a step of matching the projected patterns (M1 to M4 ) in the alignment radiographic image (IR) with respectively the channels (20 to 23) of the plate (11), a step of calculating the parameters of a second geometric transformation matrix connecting the coordinates of the patterns p rotated (M1 to M4) in the alignment radiographic image (IR) with the coordinates of the reference patterns, the position of the receiving unit (3) being determined from the parameters of the first and second matrices.
    [0010]
    The method of claim 9, wherein the calculating step further comprises calculating the orientation angles of the receiving unit from the parameters of the first and second matrices.
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    同族专利:
    公开号 | 公开日
    FR3028039B1|2016-12-30|
    US10758204B2|2020-09-01|
    US20170332986A1|2017-11-23|
    WO2016071645A1|2016-05-12|
    EP3215830A1|2017-09-13|
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    优先权:
    申请号 | 申请日 | 专利标题
    FR1460687A|FR3028039B1|2014-11-05|2014-11-05|RADIOGRAPHIC IMAGING SYSTEM AND METHOD FOR POSITIONING SUCH A SYSTEM|FR1460687A| FR3028039B1|2014-11-05|2014-11-05|RADIOGRAPHIC IMAGING SYSTEM AND METHOD FOR POSITIONING SUCH A SYSTEM|
    PCT/FR2015/052998| WO2016071645A1|2014-11-05|2015-11-05|Radiographic imaging system and method of positioning such a sysytem|
    US15/524,942| US10758204B2|2014-11-05|2015-11-05|Radiographic imaging system and method for positioning one such system|
    EP15804885.0A| EP3215830A1|2014-11-05|2015-11-05|Radiographic imaging system and method of positioning such a sysytem|
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