FR3092239A1 - Method for the virtual determination of the dose of X-rays received by the skin of a subject - Google Patents

Abstract

Method of virtual determination of the dose of X-radiation received by the skin of a subject The present invention relates to a method of virtual determination of the dose received by the skin (1) covering an area of interest (2) of the body of a given subject (3), as well as the distribution of this dose on the skin (1). Method characterized in that it consists essentially in carrying out a 3D acquisition of the visible surface (8) of the body of the subject (3) by means of a mobile RGBD camera (9), in generating a 3D model of this visible surface ( 8), in superimposing said 3D model on a real image of the subject (3) provided by a fixed RGB or RGBD camera (7, 12) to arrive at a circumferential 3D model (10) of the whole of the skin enveloping the area of interest (2) considered of the subject's body (3), to collect data on the beam (4) emitted by the imager (5), to calculate the dose received by elementary surface units of the skin (1) of the zone of interest (2), and to display, on the 3D model (10) of the skin (1) of the zone of interest (2), the distribution of the levels of irradiation by regions according to the cumulative dose received or to be received. Figure to be published with the abstract: Fig. 2

Description

Method for virtual determination of the dose of X-radiation received by the skin of a subject

The present invention relates to the medical field, in particular medical imaging using X-rays, and relates to a method for virtual determination of the dose received or to be received by the skin of a subject, and optionally by at least some organs of the latter.

Currently, with the multiplication of exposures of subjects subjected to extra- and intraoperative shots using X-ray imagers, the cumulative dose received by subjects increases sharply and can lead to local necrosis of the skin, even underlying tissues.

Indeed, although the X-ray imagers used provide information on the dose emitted and on the dose delivered at the level of a specific reference point, this is only indirect data, which does not provide information on the dose actually received by the skin, nor on its distribution.

In addition, in terms of official rules and recommendations, it is expected that a follow-up of the subject is ensured as soon as a threshold value is reached.

Another aspect to take into consideration is the significant time lag (up to several weeks) between the application of X-rays and the appearance of the consequences of a large cumulative dose on the skin.

It would therefore be very useful, even vital from a health and medical point of view, to be able to know the dose actually received by the skin of a subject, as well as its geographical distribution, at least at the level of a zone of interest, before, during and/or after each examination or exposure, as well as the cumulative dose resulting from successive previous exposures, possibly over a given period (during which the cumulative nature of the effects is checked).

There is thus a strong demand for being able to have, preferably in real time, reliable information relating to the value of the X-ray dose received and to its distribution or distribution at the level of the skin, of the dose received during a phase shot(s), as well as the cumulative dose after massive imaging phases, during examinations or operations, whether the imagers used are fixed or mobile.

In addition, a map with history of the doses received by a subject's region of interest is of obvious medical interest.

In addition, it could also be interesting to have a simple and telling illustration of the interaction of the beam with the skin of the subject, through augmented reality.

Finally, any knowledge of the dose received or to be received by one or more internal organs affected by X-ray irradiation can be important information in the event of repeated exposure.

The object of the invention is to provide a solution at least to the main demands mentioned above, with a view to overcoming the essential limitations of the state of the art.

To this end, the subject of the invention is a method for the virtual determination, prior or subsequent to an intervention or to the taking of image(s) under X-radiation, of the dose received by the skin covering a zone of interest of the body of a given subject, during at least one phase or all of the act considered, and/or cumulatively over a defined period, as well as the distribution of this dose on the skin of said subject, knowing the geometry, the dimensions and the distribution of the radiation intensity of the X-ray beam projected by the imager used, the subject lying on his back on a table during the image capture, preferably on his back,
process characterized in that it consists of:
a) placing the subject on the table,
b) to carry out a 3D acquisition of the visible surface of the lying subject and of at least part of the table, by means of a mobile RGBD camera provided with an optical marker and to generate a 3D model of this visible surface, while determining the position of said 3D model in the frame of reference of the fixed RGB camera,
c) superimposing the 3D model, reconstructed from the shots of the mobile RGBD camera, on the real image of the subject provided by a fixed RGB camera to end up with a 3D representation, in augmented reality,
d) generating a circumferential 3D model of the entire skin enveloping the considered area of interest of the subject's body,
e) to collect orientation(s), position(s) and dose value(s) data of the beam emitted by the imager during the phase or the act considered,
f) calculating the dose received during this phase or act by elementary surface units of the skin of the area of interest,
g) to display, on the 3D model of the skin of the area of interest, the distribution of the levels of irradiation by regions according to the dose received or to be received during the phase or the procedure considered, alone (e) or cumulatively with the dose(s) received during one or more previous act(s) or phase(s).

The invention will be better understood, thanks to the description below, which relates to preferred embodiments, given by way of non-limiting examples, and explained with reference to the appended diagrammatic drawings, in which:

is a perspective view of a room equipped with a fixed C-arm imager, as well as a table and a fixed RGB camera;

is a perspective view of a room equipped with a mobile C-arm imager, as well as a table and fixed RGB and RGBD cameras;

is a partial view illustrating the acquisition by means of a mobile RGBD camera of shots of the subject (pig) and of the table on which he is lying;

and

are views according to two different directions of the 3D model of the visible surface of the subject and of its immediate environment obtained by reconstitution of the shots of FIG. 3;

is an augmented reality 3D representation of the subject by superimposing the real image of the RGB camera with the 3D model of the area of interest obtained by processing shots from the mobile RGB camera;

and

are front and back views of the circumferential 3D model of the entire skin enveloping the area of interest of the subject's body, obtained from shots taken with the mobile RGBD camera followed either by a calculation carried out using using an algorithm adapted to complete the mesh of the patient for the portions in contact with the table (and which are not visible by the RGBD camera), or a registration with a preoperative 3D model (which also makes it possible to obtain the mesh of the patient's skin which is in contact with the table) or of a preoperative 3D model;

is a view similar to that of FIG. 5, with additional display of the zones corresponding to the regions with different irradiations of the skin of the zone of interest;

and

are graphic representations, respectively in the form of a plot (8A) and a screen printout (8B), making it possible to compare the theoretical curve (obtained by implementing the method) and the curve of the actual measurements of the dose received by the subject, and,

is an augmented reality 3D representation, similar to that of Figure 5, of a human subject.

The invention relates to a method for virtual determination, before or after an intervention or an image(s) being taken under X-radiation, of the dose received by the skin 1 covering a zone of interest 2 of the body of a given subject 3, during at least one phase or all of the act considered, and/or cumulatively over a defined period, as well as the distribution of this dose on the skin 1 of said subject 3, knowing the geometry, the dimensions and the distribution of the radiation intensity of the beam 4 of X-rays projected by the imager 5 used, the subject 3 lying on a table 6 during the image capture, preferably on his back.

In accordance with the invention, this method essentially consists of:
a) placing subject 3 on table 6,
b) to carry out a 3D acquisition of the visible surface 8 of the body of the elongated subject 3 and of at least part of the table 6, by means of a mobile RGBD camera 9, if necessary provided with an optical marker 9 ', and to generate a 3D model of this visible surface 8,
c) superimposing the 3D model, reconstructed from the shots of the mobile RGBD camera 9, on a real image of the subject 3 provided by a fixed RGB or RGBD camera 7 to arrive at a 3D representation 8', in augmented reality , said body of subject 3,
d) generating a circumferential 3D model 10 of all of the skin enveloping the considered area of interest 2 of the body of the subject 3,
e) in collecting orientation(s), position(s) and dose value(s) data of the beam 4 emitted by the imager 5 during the phase or act considered,
f) in calculating the dose received during this phase or act by elementary surface units of the skin 1 of the zone of interest 2,
g) to display, on the 3D model 10 of the skin 1 of the zone of interest 2, the distribution of the levels of irradiation by regions according to the dose received or to be received during the phase or the act considered (e ), alone or in combination with the dose(s) received during one or more previous procedure(s) or phase(s).

Thanks to the invention, it is thus possible to have, for a given subject 3 or at least for an area or region of interest 2 of such a subject:
- real-time information on the distribution of the individual dose applied/received during a given procedure;
- information on the cumulative dose received following repeated, performed or planned procedures;
- dynamic visualization of the interaction of the X-ray beam with the subject's skin and/or organs.

These elements make it possible, within the framework of the performance of an act to be performed or being performed, to optimize the dose delivered and/or to adjust the ballistics of application of the dose, and, within the framework of simulations of virtual systems/processes, to carry out preoperative planning and to estimate and optimize the angle of application of the X-rays on the area of interest 2, to minimize the dose received by the subject 3.

In accordance with a first embodiment, the real image of the subject 3 is provided by a fixed RGB camera 7, advantageously located in height and above the imager 5, the 3D model is provided by a mobile RGBD camera 9 provided with an optical marker 9' and a step of determining the position of the 3D model in the frame of reference of the fixed RGB camera 7 is carried out before superposition of said 3D model and the real image.

In accordance with a second embodiment, the real image of the subject 3 is provided by a fixed RGBD camera 7, advantageously located in height and above the imager 5, the 3D model is provided by an RGBD camera and a step of registering the respective clouds of points of the real image and of the 3D model is carried out before superposition of said 3D model and of said real image.

If necessary, it may be provided to acquire beforehand the relative positions of the table 6 and the imager 5 by means of the fixed RGB camera 7, provided with a reference frame.

Advantageously, the method may consist, during step d), in extracting from the partial 3D representation 8′ obtained at the end of step c), a first portion of the circumferential 3D image of the skin 1 corresponding to the area of interest 2 concerned and to generate a circumferential 3D image 10 of all of the skin 1 enveloping the area of interest 2, first by software construction of a second complementary portion corresponding to the non-visible surface, namely corresponding to the back of the subject 3, then by merging said first and second portions.

Preferably, the method may consist, prior to carrying out the intervention or the taking of image(s), in obtaining a virtual 3D model of the subject 3, or at least of the zone of interest 2 concerned, from a complete or incomplete preoperative CT or CT image of the subject 3, in carrying out, if necessary, a segmentation of said 3D model to extract therefrom a circumferential 3D representation of the entire surface of the subject 3 enveloping the zone of interest 2 concerned, and if necessary of the internal organs of this zone 2, to carry out a registration, and possibly an adaptation, of this circumferential 3D representation using the 3D image acquired by means of the RGBD camera 9 in step b), and in using this readjusted circumferential 3D representation to perform steps e) to g).

According to a first variant embodiment, and in the case of an imager 5 which is fixed, at least with respect to the table 6 and to the fixed RGB camera 7, for example fixed to the ceiling of the room housing the imager 5, the transition matrix of the frame of reference of the imager 5 to the frame of reference of the fixed RGB camera 7 and the position of the table 6 in this latter frame of reference are determined, by positioning a marker 11, visible for the imager 5 and for the fixed camera 7, on table 6 and acquiring the position of marker 11 in these two reference frames.

According to a second variant embodiment, and in the case of a mobile imager 5, the position of said imager 5 is determined by a fixed RGBD camera 12.

As part of a prior preparatory phase or during the performance of an act, the method may consist, possibly prior to the performance of a given phase or act, of estimating the foreseeable dose that the skin 1 of the area of interest 2 and its distribution, this for a given virtual position of the imager 5 relative to the subject 3 during said phase or said determined act and, possibly, to modify the position of the imager 5 and repeating the preceding estimate until a received dose value and a distribution thereof deemed optimal are reached.

In order to achieve informatively effective and intuitive visualization, it may be provided, on a display means, at least of the zone of interest 2, to visually differentiate the zones irradiated at different doses, cumulative or not, by implementation of a palette of colors correlated to said doses.

By way of example, a C-arm type X-ray imager 5 can be implemented.

In the context of efficient medical follow-up, and in connection with the use of electronic medical records, it can advantageously be provided to create a file specific to each subject 3 and containing a 3D representation of the surface of the skin of the latter or at least of the zone of interest 2 considered, displaying the distribution of the cumulative successive doses of X-rays, possibly each assigned a reduction factor depending on the age of the exposure.

Of course, the invention is not limited to the embodiments described and shown in the appended drawings. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without thereby departing from the scope of protection of the invention.

Claims (12)

Method for virtual determination, before or after an intervention or image(s) taken under X-radiation, of the dose received by the skin (1) covering a zone of interest (2) of the body of a subject (3) given, during at least one phase or all of the act in question, and/or cumulatively over a defined period, as well as the distribution of this dose on the skin (1) of the said subject (3), knowing the geometry, the dimensions and the distribution of the radiation intensity of the X-ray beam (4) projected by the imager (5) used, the subject (3) lying on a table (6) during the taking of image, preferably on his back,
process characterized in that it essentially consists of:
a) placing the subject (3) on the table (6),
b) to carry out a 3D acquisition of the visible surface (8) of the body of the elongated subject (3) and of at least a part of the table (6), by means of a mobile RGBD camera (9), the case optionally provided with an optical marker (9'), and generating a 3D model of this visible surface (8),
c) in superimposing the 3D model, reconstructed from the shots of the mobile RGBD camera (9), on a real image of the subject (3) provided by a fixed RGB or RGBD camera (7, 12) to arrive at a 3D representation (8'), in augmented reality, of said body of the subject (3),
d) generating a circumferential 3D model (10) of all of the skin enveloping the considered area of interest (2) of the body of the subject (3),
e) in collecting orientation(s), position(s) and dose value(s) data of the beam (4) emitted by the imager (5) during the phase or act considered ,
f) in calculating the dose received during this phase or act by elementary surface units of the skin (1) of the zone of interest (2),
g) displaying, on the 3D model (10) of the skin (1) of the area of interest (2), the distribution of the irradiation levels by region as a function of the dose received or to be received during the phase or the act considered, alone or in combination with the dose(s) received during one or more previous act(s) or phase(s). Method according to claim 1, characterized in that the real image of the subject (3) is provided by a fixed RGB camera (7), advantageously located at height and above the imager (5), in that the 3D model is provided by a mobile RGBD camera (9) provided with an optical marker (9') and in that a step of determining the position of the 3D model in the frame of reference of the fixed RGB camera (7) is carried out before superimposing said 3D model and the real image. Method according to Claim 1, characterized in that the real image of the subject (3) is provided by a fixed RGBD camera (7), advantageously located at height and above the imager (5), in that the 3D model is supplied by an RGBD camera and in that a step of registering the respective clouds of points of the real image and of the 3D model is carried out before superimposing said 3D model and said real image. Method according to any one of Claims 1 to 3, characterized in that it consists, during step d), of extracting from the partial 3D representation (8') obtained at the end of step c) , a first portion of the circumferential 3D image of the skin (1) corresponding to the area of interest (2) concerned and to generate a circumferential 3D image (10) of all of the skin (1) surrounding the area of interest (2), first by software construction of a second complementary portion corresponding to the non-visible surface, namely corresponding to the back of the subject (3), then by merging said first and second portions. Method according to any one of Claims 1 to 3, characterized in that it consists, prior to carrying out the intervention or the taking of image(s), in obtaining a virtual 3D model of the subject (3) , or at least of the area of interest (2) concerned, from a complete or incomplete preoperative CT or CT image of the subject (3), in carrying out, if necessary, a segmentation of said 3D model to extract a 3D representation therefrom circumferential of the entire surface of the subject (3) enveloping the zone of interest (2) concerned, and if necessary of the internal organs of this zone (2), to carry out a registration, and possibly an adaptation, of this representation circumferential 3D using the 3D image acquired by means of the RGBD camera (9) in step b), and using this registered circumferential 3D representation to perform steps e) to g). Method according to any one of Claims 1 to 5, characterized in that in the case of an imager (5) which is fixed, at least with respect to the table (6) and to the fixed RGB camera (7), for example fixed to the ceiling of the room housing the imager (5), the transition matrix from the imager reference frame (5) to the fixed RGB camera reference frame (7) and the position of the table (6) are determined in this last frame of reference, by positioning a marker (11), visible for the imager (5) and for the fixed camera (7), on the table (6) and by acquiring the position of the marker (11) in these two frames of reference . Method according to any one of Claims 1 to 5, characterized in that in the case of a mobile imager (5), the position of the said imager (5) is determined by a fixed RGBD camera (12). Method according to any one of Claims 1 to 7, characterized in that it consists, possibly prior to carrying out a given phase or act, in estimating the foreseeable dose that the skin (1 ) of the area of interest (2) and its distribution, this for a given virtual position of the imager (5) relative to the subject (3) during said phase or said determined act and, possibly, to modify the position of the imager (5) and repeating the preceding estimate until a received dose value and a distribution thereof deemed optimal are reached. Method according to any one of Claims 1 to 8, characterized in that it consists in visually differentiating the zones irradiated at different doses, cumulative or not, by implementing a palette of colors correlated to said doses. Method according to any one of Claims 1 to 9, characterized in that it consists in implementing a C-arm type X-ray imager (5). Method according to any one of Claims 1 to 10, characterized in that it consists in creating a file specific to each subject (3) and containing a 3D representation of the surface of the skin of the latter or at least of the area of interest (2) considered, displaying the distribution of successive cumulative doses of X-rays, each possibly affected by a reduction factor depending on the duration of the exposure. Method according to any one of Claims 1 to 11, characterized in that it consists in acquiring beforehand the relative positions of the table (6) and of the imager (5) by means of the fixed RGB camera (7) , provided with a frame of reference.