FR2685155A1 - Device for viewing X-rays and use of this device - Google Patents

Abstract

In order to simplify stereographic viewing (5) and mammography, each of the two negatives (2, 3) obtained is placed facing a black-and-white television camera (1, 8). The image signals from these two cameras are sent (4, 9) on two different colour channels, for example on the green (V) channel and on the magenta (R, B) channel of a colour television monitor (5). Then, by means of a micrometer screw (16), one of the negatives is moved with respect to the other. Thus at one moment an image is made to appear which, instead of remaining a colour image, becomes a black-and-white only image. This moment reveals coincidences of X-ray abnormalities. With respect to an initial setting position, it is possible to measure a deviation imparted by the micrometer screw (16) and to deduce therefrom, in a conventional way, values of cartesian coordinates of the position of a tumour which corresponds to these abnormalities.

Description

DEVICE FOR VIEWING RADIOGRAPHS AND
USE OF THIS DEVICE
The present invention relates to a device for viewing radiographs, as well as the use of this device. The use which is described in this patent application is essentially a medical type use. The device is in particular described for viewing radiographs, in particular radiographic images, resulting from irradiation of a patient with an X-ray tube.

The invention can nevertheless find its use in other fields, in particular in non-destructive testing.

 The object of the invention is to improve the reading of radiographs and therefore to allow the observation of micro details, in particular in the field of mammography, in order to examine the presence of micro-calcifications. The invention also aims, by comparing two radiographs, to determine relief information relating to the radiographed objects. In particular, we will seek to locate in space, at altitude, the position of micro-calcifications in the breast of patients.

 Finally, the invention makes it possible to observe over time dimensional variations in the bones, in general radiology. In addition, the invention makes it possible to carry out measurements of radiological density, in particular in bone densitometry, by comparing radiographs acquired under two different energies of X-ray radiation.

 The invention also relates to a stereography device in mammography which allows a simple and inexpensive adaptation of mammographs not originally intended for this.

 Devices for viewing radiographs are known, in particular devices comprising digitization of images. In principle, these devices include a television camera which takes a radiographic image which is presented to them.

These cameras deliver image signals representing radiography. Also known, in radioscopy, radiological image intensifying screens, coupled to television cameras which also deliver image signals in real time. These image signals are normally analog signals. They are formatted in television mode.

 Before their visualization, they are generally subjected to treatments. When these treatments are digital, the analog signal is first transformed into a digital signal by interposed analog digital converters. Then the digital signals are processed, in particular to take into account the detection sensitivity (the sensitivity of the image intensifier screen or the sensitivity of the film on which the radiographic image is revealed).

They can also be processed to perform contrast expansions, in selected contrast windows.

 These digital signals, processed or not, relating to an image, can be stored in an image memory. For visualization, the image memory is connected to a visualization monitor. The operation of such a monitor is similar to that of a conventional television set. The image is thus presented on the screen of this monitor.

 It is also known to use color monitors to present an image. In this case, protocols are used to show color images by which certain levels of the image signal are assigned to particular colors.

 All these devices, and in particular the treatments, have the drawback on the one hand of being very complicated, and on the other hand, despite this complication, of being ineffective. Indeed, in particular for the examination of breast cancer and the revelation of micro-calcifications, there is an essential difficulty, linked to the fact that these micro-calcifications are not very differentiated in terms of contrast with the surrounding tissues. We are therefore required to process the signal to reinforce this contrast. However, by doing so, in particular in stereoscopy or stereography, one can lose the notion of coherence that there is between the micro-calcifications revealed by the two images acquired under two incidences from the same breast. It becomes difficult, if not impossible, for a computer system to restore this coherence and bring out in a flagrant manner the position of the same micro-calcifications in the two photographs.

 The object of the invention is to solve this problem, by proposing a method of great simplicity, which does not require, a priori, significant calculations of image processing, although one can also execute them, and which is easily learned by practitioners. To implement this method, the invention recommends a simple device.

 The principle of the invention is as follows. To view two x-rays and compare them, we capture images from these x-rays with one (or two) television cameras. An image signal from one of the two images is sent to one of the color channels of a television monitor. If this signal were revealed alone on the screen of this monitor, a monochrome image would be obtained, for example in green if the green color channel was chosen. The other image signal is sent on another color channel, for example red, or blue, or even preferably on a combination of the two remaining colors, red and blue.

In this way we would also obtain another monochrome image, if it is presented alone. The color of this other image alone is magenta (red and blue mixed positively by additive synthesis).

 In the invention, an image is represented on the screen of the monitor simultaneously with the representation of the other image on the same screen. Each of the images is then sent on different color channels. By means of a shifting method, another object of the invention, a monochrome image is moreover displaced on the screen with respect to the other. As long as the images are not in coincidence, we have an overall colored image. It comprises for example green zones and dark zones (relating to the first image), magenta zones and dark zones (relating to the second image), and colored and clear zones (relating to the imperfect superposition of certain drawings of the two images).

 When by shifting one image with respect to another one arrives at a perfect superposition, one obtains an image in which each of the image elements of the screen receives a signal of brightness on the green channel, on the blue channel and on the red way: on this image element, the light signal is made white. At other points, where no brightness is received, the points are dark.

 In this case, when there is a coincidence, we therefore obtain a black and white image and no longer a color image. This simple principle is implemented in the invention, to make it possible to detect the presence of micro-calcifications. It suffices to detect the transition from the colored image to the black and white image. Of course, one can also determine the altitude position of these micro-calcifications. As is known elsewhere, this determination is obtained by measuring the offset of the radiographs, between the presentation of the images calibrated at the start and the place of coincidence.

The subject of the invention is therefore a device for viewing radiographs comprising
at least one television camera for taking images from these two radiographs and delivering corresponding image signals, and
- a color monitor comprising several color channels for receiving these image signals and representing these images, characterized in that
- the image signal of one of the two images is sent on one of the color channels of the monitor,
- the image signal of the other image is sent on another color channel of the monitor, in order to represent at the same time, on the screen of this monitor, the two raised images.

 The subject of the invention is also a mammograph comprising an X-ray tube, a breast plate, a breast compression plate, and a device for collecting an X-ray image, characterized in that the two plates are mounted movable on a structure fixed relative to the tube and to the sampling device, the mobility being perpendicular to a main direction which connects the tube to the sampling device.

 The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These are given for information only and in no way limit the invention. Although the invention will be described for a digital image signal, it is also applicable to the case where the image signal is present in analog form and not in digital form. The figures show - Figure 1: a schematic representation of the radiography display device of the invention; Figures 2a and 2b: examples of acquisitions of radiographic images, studied by the display mode of the invention, in the context of mammography; - Figures 3a to 3c: schematic representations of displayed images showing the principle of the invention; - Figure 4: a diagram showing the principle of localization in altitude of micro-calcifications; - Figure 5a and 5b: the effect of detecting microcalcifications with the mammograph of the invention.

 Figure 1 shows a radiography display device according to the invention. This device comprises at least one television camera 1 for taking images from two x-rays, respectively 2 and 3, and delivering corresponding image signals.

These image signals are for example transmitted in real time by a connection 4 to a color monitor 5. The color monitor 5 has three color channels, respectively the red R, blue B and green V channels. This monitor 5 is normally intended to receive a color television signal transmitted on an input 6. This monitor normally comprises processing circuits which extract from the color signal received at 6, signal components to be sent on each of the three color inputs RB V. In the invention , the image signal of one of the two images is sent directly on one of the channels of the color monitor, for example on the green channel, while the other signal is sent directly on another channel, for example the red channel, or the blue way, or preferably on a color way combining these two last, to form a magenta color.

 Preferably, to view in real time x-rays 2 and 3 placed on a X-ray film viewer 7, two television cameras are used, the television camera 1 and a television camera 8. These two cameras take the images from the x-rays 2 simultaneously and respectively. and 3. The image signal picked up by the camera 8 is transmitted by a connection 9.

 In a digitized version, the image signals are sent in analog-digital converters respectively 10 and 11, and possibly processed, according to known modes, in downstream processing devices, respectively 12 and 13. These signals processed or not can be stored in an image memory 14. Since it is a question of storing a color image, the image memory comprises three pages in the invention: a green page, a red page and a blue page. In each of these pages, each image element of the screen of the monitor 5 is identified by the same address. The image signal delivered by the camera 1 is stored in the green page, while the image signal delivered by the camera 8 is stored, preferably, in both the red page and the blue page. When this image memory 14 is read, these signals, previously delivered in analog form, are transmitted to the corresponding color channels of the monitor 5.

 You don't have to look at x-rays. One can, for example, also examine image signals which would have been recorded by means of an intensifying screen of radiological images and which would have been stored in image memories of monochrome type. The information content of these image memories would, according to the invention, be transferred in deferred time to a color image memory such as the image memory 14. This also makes it possible to implement the invention. When we talk about x-rays, it is therefore not necessarily x-rays. Just as well, they can be images acquired in real time using a bifocal x-ray tube.

 In the invention, provision can also be made to offset the representation of one radiography with respect to the other. For example, provision is made to offset the radiography 3 with respect to the radiography 2. For this purpose, the radiography 3 can be driven by a carriage or feeder 15. The movements of the carriage 15 are imposed by a micrometric screw 16. During this displacement, the radiography 2 remains fixed facing the camera 1. The displacement means, which comprise this micrometric screw 16, can be replaced by an articulation 17 of the focal length of one of the two cameras, or rather a translation of one of the two cameras, for example camera 8. Likewise, and more simply, it is possible, when reading the image memory 14, to shift the reading addresses of the image signals read in the green page, relative to the addresses of the corresponding image signals read in the red and blue pages.

 In doing so, an image can be composed on the monitor 5. This image corresponds by a drawing 18 to the image of the radiography 2, and by a drawing 19 to the image of the radiography 3. When the shift of the x-rays, for example by means of the micrometric screw 16 (or by means of an operating ball or a mouse 20, connected to a microprocessor 21 which controls the reading of the image memory 14), the displacement of the drawing 19 relative to the drawing 18. If the two radiographs are identical, it is possible to obtain, at the time of the superposition, a black and white image and no longer a color image. Indeed, as explained above, by additive synthesis, there are no more than picture elements receiving both a red blue and green signal, or nothing at all.

 For this to happen, it may be useful to adjust, beforehand, by means of brightness or luminance buttons 22 to 24 of the monitor 5, for each of the red, blue or green channels, the brightness of the elements of image so as to obtain, for each monochrome image, a perfect range of gray, and so as to adjust the contrasts in green or in magenta in the same way. To simplify, this can amount to sending half of the signal sent on the green track to the red track and to the blue track. This may not be entirely accurate, given the flaws in the linearity of the disclosure. The adjustment with buttons 22 to 24 takes account of this non-linearity. If necessary, a processing program contained in a memory 28 in relation to the microprocessor 21 may contain instructions which, in addition to the processing and the address offset, also manage these contrast problems.

 If the adjustment is not possible in a large range of gray, one will be satisfied with obtaining it for a weaker range. This lower range corresponds to the range of only part of radiographs 2 and 3, part for which we will look locally for coincidence.

 It is not necessary to cause a displacement of the images to implement the principle of the invention. Indeed, if one acquires images under two different energies, for example under 120 KV and 70 KV to see bone tissue, or for example under 20 KV and 25 KV to examine breasts, one can also visualize these two images simultaneously. Given the differences in contrast due to the different energies, the images, which strictly represent the same object, do not have marked contours, in terms of contrast1 in the same way. We then proceed as follows: we adjust with one of the luminance buttons the luminance (or gray level) of one of the channels so that, locally, the black and white image covers part of the object for which we are looking to measure the density. We measure the position of the button, or the value of this luminance. Then we shift the setting of this button. We then observe that the black and white part of the image moves inside the monitored contour.

In practice, we then see a black and white wave propagate on the screen. We stop modifying the setting when this wave has swept the entire surface we are studying. The new luminance value is then measured. The density sought is deduced from these two luminance measurements.

 The theoretical calculations that lead to this density-luminance relationship can be quite complicated to carry out. First, we are satisfied with a calibration: we measure the variations in luminance values obtained by viewing objects of known density. We draw abacuses which reflect these correspondences. Thereafter, we refer to these abacuses to determine the density. The abacuses are not necessarily drawings. They can be tables stored in the memory 28 in relation to the microprocessor 21. Similarly, the luminance value of a channel, the position of the adjustment knob, can be managed by the microprocessor 21. In the latter case, this ci can impose, in overlay in a line at the bottom of the screen of the monitor 5, the density value calculated by interpreting the two adjustment values.

 For reasons of value for money, the two cameras are black and white video cameras, for example of the CCD type. The lenses of the cameras look at a X-ray viewer on which the x-rays are arranged. On the top of the X-ray viewer, there is a transparent plate which receives the pictures. This negatoscope comprises a fixed feeder 25, making it possible to wedge the radiographic image 2, and a feeder constituted by the carriage 15 capable of moving in translation. Maintaining the position of the plate 2 can even be facilitated by the presence of pins such as 26, entering perforations made in advance in the plate 2. The mobile feeder 15 has a garage position, adjusted by construction, corresponding to predetermined positions of the radiographs.

 In one example, against the feeder 25, a snapshot of the lumbar spine taken in profile and executed on October 15, 1990 was placed. The camera n01 is centered, on this snapshot, on the vertebra called L3. The black and white image signal is interpreted in green on the monitor 5.

Against the carriage 15, a photograph of the same anatomical region was placed. However, this radiography was performed a year later, on October 17, 1991. The image signal detected by the camera 8 is interpreted in magenta on the monitor 5. As the images are slightly different, it is necessary to move to by hand the pictures, make the lumbar L3 raised by the camera 8 coincide, with the lumbar L3 raised by the camera 1. To simplify this coincidence, for example, the upper plates of the vertebra coincide. We could then see that the lower plates of this vertebra are distinguished from each other. Thus, instead of having a line which represents these lower plates, single and of white color, one obtained a double line: green for the image revealed by the camera 1, and magenta for the image revealed by the camera 8 .

 It is a vertebral compaction. We can measure its evolution. There are several ways to do this. For example, you can measure the distance between the green line and the magenta line on the screen. If this is not sufficiently precise, one causes, by means of the micrometric screw 16 or the maneuvering ball 20, or by another described means, an offset of the radiography 3, so that the lower plates of the vertebra coincide. When the coincidence occurs the two-color lines transform into a single luminous line. If necessary to make the coincidence even more precise, it is possible to use the zooming capabilities of the monitor 5.

 Between the two coincidence positions, the desired difference is obtained. It is thus possible to measure, with the micrometer, crushings due to osteoporosis of the order of a tenth of a millimeter.

 In other words, the invention makes it possible to reveal, by the presence of colored lines (green and magenta in a color image, instead of more or less gray lines in a black and white image), the lack of coincidence of two images. We measure with the micrometric screw or by a similar means, the shift that must be made to an image, so that this defect of coincidence is compensated.

 When a digital version of the image signal is not used, with or without intermediate storage in an image memory 14, it may be necessary to synchronize the two cameras, with each other, so that their horizontal and vertical scanning correspond to each other. This can be obtained naturally by connecting, by an electrical link such as 27, the synchronization commands of the two time bases of these cameras. The monitor 5 is also synchronized with cameras.

 In the case where the image memory 14 is not used, and where the two cameras have been synchronized, it is also possible to cause the two offsets by subjecting one of the two signals delivered by one of the two cameras to a delay with respect to to the signal from the other camera. We can simply place an adjustable delay line in series in one of the two connections 4 or 9. By varying the delay, we vary the representation shift of one of the two images displayed on the monitor screen. The monitor 5 is then only synchronized with one of the two cameras.

 Figure 2 shows a mammography application. This schematic representation shows an X-ray tube 30 radiating in a first position 31, the breast 32 of a patient. In Figure 2a, the X-ray tube moves from one position to another. In Figure 2b the breast 32 moves from one position to another. This breast 32 is kept in compression between a compression plate or ball 33 and a breast plate 34. A cassette 35 carrying a radio sensitive film, can be placed directly below the plate 34, or possibly distant from this plate for allow an enlargement of the image.

 In position 31, a first picture is taken. Then, the sensitive radio film is replaced inside the cassette 35, and a second picture is taken, while the apparatus occupies another position, position 36. Positions 31 and 36 are inclined relative to the vertical, preferably symmetrically by a more alpha or less alpha angle respectively.

 With the device of FIG. 2b, an attempt is made to adapt existing mammographs, those with a fixed column 37 which carries the tube 50 and the cassette 35.

For this purpose, a structure 38 is placed on the cassette 35, or on the breast plate 34. the structure 38 essentially comprises a slide 39 which maintains the compression plate 33, preferably at predetermined positions, in lateral translation according to the arrow 40 perpendicular to the radii of the tube 30. If the plate 33 is moved alone, for example by 1 or 2 cm, the breast rolls on itself. We can acquire different images for different positions of this board. Figures 5a and 5b show the effects of this double acquisition. The structure 38 also includes another slide in order to be able to move a false breast support plate 41. In this way, by linking the two sliding plates, the breast can be moved laterally without causing it to roll. With the images acquired in both cases, a stereotaxic study can be carried out.

 So we develop pictures and put them on a negatoscope of a stereotaxic device. We know, normally, with a stereotaxic apparatus comprising a negatoscope and movable indexes above the negatoscope, to move two indexes above the two pictures thus obtained for directions 31 and 36, and to point to accidents there. radiographic: the presence of suspicious spots. We can measure the displacements that these indexes must undergo, above each image, in order to point to these spots. If these spots correspond to a tumor, the calculation of the three-dimensional Cartesian coordinates of the positions of the tumor in the breast are of known type. They are based on the measurement of index displacements. They are, for example, of the type described in French patent application 2 248 535, filed on October 17, 1974 or in French patent application 2 645 286 filed on March 29, 1989.

 In the invention, to identify the presence of tumors at altitude, the same principle is used. Quite simply, the displacement of the micrometric screw 16 gives the equivalent of the distance traveled by one of the indexes with respect to the other. It is used to calculate the altitude of the tumor. The displacement of the screw 16 can be replaced by the other means described above. The displacement of the micrometric screw, or that caused by the other means, of displacement can be measured by a displacement calibration and a location of the starting and ending positions.

These calculations have for example the following form, relating to FIG. 4: this relates to the application of FIG. 2b. The formula below provides the Z altitude of the tumor. The meaning of the references is as follows
A is the focus of the X-rays;
D is the focal point X / image distance; d is the displacement of the breast (20mm in our example) from one snapshot to another relative to the vertical
M - d is the measurement of the shift in the micrometer
Hmc is the height of the micro-calcifications starting from the lower part of the breast;
H is the distance from the radiograph to the upper part of the breast.

(D / M) x (M-20) = H
H-20 = Hmc
Any other formula, in particular for the application represented in FIG. 2a, can be deduced by trigonometric composition. In this case, it becomes
D / ((d + M) / M) = H
with HC = Hmc
However, in examining microcalcifications, the invention makes it possible to be even more effective.

Indeed, in the state of the art, or as said above, to be able to point an index on a radiological accident, it is necessary to see this accident. However, the presence of microcalcifications is not easily detectable.

In the invention, it is detected that one is in the presence of such micro-calcifications, collected one next to the other, when, suddenly, during the displacement of an image relative to the other image overall on the screen that was previously colored becomes a black and white only image (at least locally). In this case, the passage of part of the image, from color to black and white, reveals the presence of these microcalcifications.

 The invention makes it possible to compare two radiographic images, or more generally two radiographs, or even two images, as long as one is sent on a color channel while another is sent on another channel. For most of the comparison, you don't even have to plan a trip. The mode of comparison of the invention is shown schematically in Figures 3a to 3d. FIG. 3a shows for example the representation of the photograph 2, where the green color of the radiological accidents is materialized by small circles. In the same conditions, Figure 3b shows the presentation of the photo 3, where the magenta color is represented by crosses. When we move, Figure 3c, superimposing one of the two images relative to the other, the crosses move towards the circles. At the time of coincidence, Figure 3d, we get a black and white image: there are no more circles or crosses, these are replaced by large dots more or less gray.

 Figures Sa and 5b show the effects of a breast roll. Usually, the tumors attach to the milk ducts. The two figures each show three. In the channel shown at the top of these figures, the presence of three radiological accidents has been schematized by X's. We do not know a priori whether the center one is also superimposed on the canal.

After rolling the breast slightly, the second X-ray shows that the central accident is still on the canal. In this case, the prognosis is poor. Either the central accident marked by an O is no longer located on the trace of the canal: the prognosis is not bad. On the right of each figure, an image is projected showing the phenomenon.

Claims (16)

 1 - X-ray display device (2,3) comprising  at least one television camera (1) for taking images from these two radiographs and delivering (4) corresponding image signals, and  - a color monitor (5) comprising several color channels (R, G, B) for receiving these image signals and representing these images, characterized in that  - the image signal of one (2) of the two images is sent on one (V) of the color channels of the monitor,  - the image signal of the other image (3) is sent on another channel (R, B) of the monitor color, in order to represent at the same time, on the screen of this monitor, the two images detected.  2 - Device according to claim 1, characterized in that  - This device comprises means (16) for moving, on the screen, one of the two images shown with respect to the other.  3 - Device according to claim 1 or claim 2, characterized in that  - the monitor has three color channels (R, G, B),  - one of the two image signals is sent on one channel, while the other is sent at the same time on the other two channels.  4 - Device according to any one of claims 1 to 3, characterized in that it comprises  - two television cameras (1,8) for simultaneously capturing images from each of the two radiographs.  5 - Device according to claim 4, characterized in that  - the two cameras are synchronized. (27)  6 - Device according to any one of claims 1 to 5, characterized in that  - the means for moving one of the on the screen. two images shown in relation to each other include a carriage (15) for moving one of the two x-rays in the field of the camera.  7 - Device according to any one of claims 1 to 5, characterized in that  - The means for moving one of the two images shown relative to the other on the screen include means (17) for shifting the focal length of one of the two cameras.  8 - Device according to claim 4, characterized in that  - The means for moving one of the two images shown relative to the other on the screen include means for delaying the image signals delivered by one of the two cameras.  9 - Device according to any one of claims 1 to 8, characterized in that it comprises for moving the radiographed object at the time of acquisition of the radiography. (fig. 2b)  10 - Device according to any one of claims 1 to 9, characterized in that  the image signals are stored, (14) image element by image element, in memory cells of an image memory,  - the content of the image memory is read and then viewed by the monitor.  11 - Device according to claim 10, characterized in that  - the means for moving one of the two images shown relative to the other on the screen include means (21, 28) for shifting in the image memory apparent addresses for storing image signals relating to a color relative to the addresses of the image signals relative to the other color.  12 - Device according to any one of claims 5 to 11, characterized in that  - The means for moving are connected to displacement measuring means to deduce therefrom relief information of the same object represented on the two radiographs.  13 - Device according to any one of claims 1 to 12, characterized in that  - the two colors are green and magenta, the latter color being obtained by a combination of red and blue, green red and blue being the three color channels of the color monitor.  14 - Use of the device according to any one of claims 1 to 13 for examining radiographs of the same object obtained with radiation of different X-ray energies.  15 - Use of the device according to any one of claims 1 to 13 for examining radiography produced by a mammograph.  16 - Mammograph comprising an X-ray tube, a breast plate, a breast compression plate, and a device for taking an X-ray image, characterized in that the two plates are mounted mobile on a fixed structure (38) relative to the tube and the sampling device, the mobility being perpendicular (40) to a main direction which connects the tube to the sampling device.