EP1250705B1 - Radiological image sensing system for scanning x-ray generator - Google Patents

Radiological image sensing system for scanning x-ray generator Download PDF

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Publication number
EP1250705B1
EP1250705B1 EP00993753A EP00993753A EP1250705B1 EP 1250705 B1 EP1250705 B1 EP 1250705B1 EP 00993753 A EP00993753 A EP 00993753A EP 00993753 A EP00993753 A EP 00993753A EP 1250705 B1 EP1250705 B1 EP 1250705B1
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EP
European Patent Office
Prior art keywords
image
image sensor
detection system
scanning
irradiated
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German (de)
French (fr)
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EP1250705A1 (en
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Paul Thomson-CSF Propriété IntellectuellE DE GROOT
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Thales Electron Devices SA
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Thales Electron Devices SA
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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/02—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators
    • G21K1/04—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators using variable diaphragms, shutters, choppers
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/02—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators
    • G21K1/04—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators using variable diaphragms, shutters, choppers
    • G21K1/043—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators using variable diaphragms, shutters, choppers changing time structure of beams by mechanical means, e.g. choppers, spinning filter wheels

Definitions

  • the present invention relates to a detection system image for a scanning X-ray generator capable of operate at high speed.
  • X-ray imaging systems comprising a system of X-ray image detection associated with an X-ray generator are used in the medical field or in the field of control not destructive. In these types of application, we seek to obtain images of very good quality and particularly well contrasted.
  • a conventional X-ray imaging system used in the medical field generally includes an X-ray generator delivering X-rays to which a patient is exposed and, in contrast to the X-ray generator, a detection system that detects radiation X having passed through the patient and who is then carrying a radiological image.
  • the X-ray generator and the patient are positioned relative to each other. each other so that the x-ray irradiation field covers at a instant given the entire surface to be imaged of the patient.
  • the detection system stationary then simultaneously detects the radiological image of the entire surface to be imaged.
  • This grid absorbs a large part of the scattered X-rays but also absorbs some useful x-rays, and therefore requires a dose higher patient.
  • This grid is currently the only solution for eliminate diffuse in intensifier tube detection systems which are currently the most used to make real-time radiological imaging.
  • Another solution to get rid of X-rays scattered without increasing the dose of x-rays involves using an x-ray generator scanning which irradiates the surface to be imaged in a progressive manner, the area instant irradiated being only a portion of the surface to be imaged.
  • the X-ray generator is associated with a system mobile detection which is synchronized with the scanning movement of the X-ray and in geometric correspondence with the irradiated area Instant.
  • the detection system is generally made up of elements solid state sensors covered with scintillator material and arranged in bar, the dimensions of this bar are such that it only receives the image of the instant irradiated area. It therefore does not detect the rays Scattered X which are deflected but which X-rays have passed directly through the patient.
  • the dimensions of the bar are conditioned by those of the instant irradiated area. It is therefore not possible, without changing bar, to want to optimize the compromise between the dimensions of the area irradiated and the X-ray rate.
  • the precision mechanics used to move the system detection represents an important item in the cost of such detection systems detection.
  • the present invention while continuing to eliminate the scattering of radiological images, aims to overcome the above-mentioned problems, especially related to the doses to be administered to the patient, to the movement mechanics of the image sensor or other parts such as slots in shutters on the detection side; it allows to reach speeds compatible with those required in fluoroscopy mode.
  • the present invention proposes a system of radiological image detection able to cooperate with a generator X-ray scanning to produce X-ray scanning a surface to be imaged, this X-ray irradiating portion after portion the surface to be imaged, X-ray radiation from a portion carrying an image radiological of said portion.
  • the system includes an image sensor which is stationary with respect to the sweep and which is dimensioned to be able to acquire an image of the entire surface to be imaged via X-ray radiation portions, the detection system further comprising means electronic to limit, at a given time, the acquisition of the sensor image to an area corresponding to the portion irradiated at this time, these electronic limitation means being in synchronism with the scanning and in geometric correspondence with the irradiated portion.
  • Electronic limitation means are purely static unlike rotating or scrolling mechanical limiting means of the prior art.
  • the means to limit the acquisition of the image sensor can be means for partially obscuring the image sensor with respect to the surface to be imaged, external to the sensor image.
  • a liquid crystal display whose scanning is controlled by synchronization with the scanning of the X-ray beam, makes it possible not to pass to a detection camera only a limited image area corresponding to that which is illuminated at this instant by the detector.
  • the image sensor can be a bright image sensor and cooperate with means to convert X-rays from portions in bright image.
  • the image sensor can be a electronic image sensor and cooperate with means to convert the X-ray from the portions directly in electronic image.
  • the selenium sensors are able to do this direct conversion.
  • the means to limit the acquisition of the sensor can be integrated into the image sensor, this being organized to prevent any image acquisition outside the area that corresponds to an image portion illuminated at an instant by the X-ray beam.
  • the image sensor can be of the solid state type and in particular of the type CCD, CMOS type, with photosensitive diodes, with capacitive elements.
  • the image sensor can be a light image sensor formed of a plurality of photosensitive pixels in the solid state, the means for limit the acquisition of the image sensor can order, just before that a portion is not irradiated, an erasure of the pixels of the sensor corresponding to the light image of said irradiated portion, and a reading of said pixels just after the irradiation of said portion.
  • the image sensor can be a formed electronic image sensor of a plurality of capacitive elements and the means for limiting the acquisition of the image sensor can order just before a portion is irradiated, resetting the charge of the corresponding capacitive elements to the electronic image of said irradiated portion and a reading of the charges stored in said capacitive elements just after the irradiation of said portion.
  • the light image sensor is of the film type. photographic or cinematographic film; in this case we will use principle a liquid crystal display to perform image limitation.
  • Means for converting X-rays into bright images can be of radiological image intensifier or scintillator type deposited on a photosensitive matrix in the solid state, while the means to convert x-ray into electronic image can be realized based on selenium.
  • the detection system may include means for processing the image captured by the image sensor so as to reconstruct an image complete radiological image of the surface to be imaged from the images irradiated areas.
  • FIG. 1 represents an image detection system 20.
  • This image detection system is used in imaging equipment medical comprising a scanning X-ray generator 10 which delivers a X-ray 1 scanning a surface to be imaged 2 of a patient 3 to be examined.
  • the X-ray radiation only irradiates a portion 2 ′ of the surface to be imaged 2.
  • the X-ray generator 10 at scan can be a slot scan, i.e. with a slot that moves in front of an X-ray source or be fixed slit as described by example in French patent application FR A- 2 795 864.
  • the scanning speed may be high, in the absence of movements of mechanical parts.
  • the detection system 20 On the other side of patient 3, i.e. opposite the generator 10 scanning x-ray is the detection system 20. It detects the X-ray 1 having passed through the patient, this X-ray being carrier of a radiological image.
  • the image detection system 20 includes an image sensor 22 intended to acquire, via the X-ray radiation coming from the portions, an image of the surface to be imaged.
  • This image sensor 22 is stationary with respect to the scan and it has dimensions allowing it to acquire an image of the entire surface to be imaged 2. It is neither set in motion nor limited in dimensions to those of the irradiated portion. By removing the means for set the sensor in motion since it is stationary, we get rid of in particular mechanical problems encountered with a sensor displaceable to the rhythm of the sweeping radiation.
  • the image detection system 20 also includes means 24 to limit, at a given instant, the acquisition of the image sensor 22 essentially to that of the image of the portion 2 'irradiated at this instant, these means being in synchronism with the scan and in correspondence geometric with the irradiated portion 2 '.
  • a dotted line illustrates the synchronism between the scanning X-ray 1 and the means 24 limiting the acquisition of the image sensor 22.
  • the image sensor 22 is a sensor of bright image and it cooperates with means 21 to convert the X-ray carrying the radiological image into a bright image received by the light image sensor 22.
  • the detection system 20 includes as image conversion means an image intensifier tube radiological 21 known by the acronym IIR, followed by the image sensor 22 light.
  • the means 24 limiting the acquisition of the image sensor 22 light are mechanical means for partially obscuring the sensor 22 bright image. These partial concealment means 24 are external to the light image sensor 22, they partially mask the sensor image 22 so that it captures, at a given instant, only the image light of the portion irradiated 2 ′ by the scanning X 1 radiation.
  • the IIR tube 21 conventionally comprises an enclosure 200 vacuum tight closed at one end by an entrance window 201 by which penetrates the scanning X-ray 1 having passed through the patient 3.
  • the X-ray scanning 1 then meets an input screen 202 whose function is to translate the intensity of X-rays into a amount of electrons.
  • This input screen 202 is dimensioned so as to be able to be struck by X 1 radiation regardless of the place of impact on the input window 201.
  • the input screen 202 generally comprises a scintillator 203 associated with a photocathode 204.
  • the scintillator 203 converts the scanning X-ray 1 into visible photons which are themselves converted to electrons by photocathode 204.
  • a set of electrodes 205 accelerates the electrons and focuses them on a cathodoluminescent output screen 206.
  • the output screen 206 luminescent is disposed near an exit window 207 located at opposite of the input window 201.
  • the impact of electrons on the screen luminescent 206 allows to reconstruct the luminous image which has formed on photocathode 204. This bright image translates at a given time the radiological image of the irradiated portion 2 '.
  • This bright image contains the faults mentioned above because with only the scanning X-ray, scattered X-rays strike photocathode 204 and their effect is visible on the output screen 206.
  • This bright image sensor 22 is generally a CCD type sensor (for Charge-Coupled Device in English language or charge coupled device) included in a camera video 220, a cinematographic film placed in a camera cinematographic or photographic film included in a camera photographic.
  • the CCD sensor can advantageously be replaced by a CMOS type sensor that works very similarly.
  • the transmission of the bright image displayed by the screen of output 206 to the light image sensor 22 is generally done by via an optical coupling device 209, arranged outside of the IIR tube 21 and centered on a longitudinal axis XX 'of the IIR tube, axis around which is also centered the output screen 206.
  • This optical device for coupling 209 may include lenses and / or optical fibers.
  • the light image sensor 22 is sized to receive the entire image of the surface to be imaged 2, as is the case in conventional X-ray beam image detection systems stationary.
  • the image detection system 20 may include a device signal acquisition and processing 23 which processes and stores signals relating to the image delivered to it by the light image sensor 22. After appropriate treatment, these signals can be observed on a display 25.
  • the light image sensor 22 is stationary with respect to the scanning while the concealment means partial 24 are movable and more particularly rotatable relative to the 22 bright image sensor. They are placed between the output screen 206 and the light image sensor 22.
  • This window 241 can simply be a opening in the disc which lets pass the bright image of the portion irradiated 2 '.
  • the disc 240 is rotated so that its window 241 moves in synchronism with the X-ray 1 scanning the surface to be imaged 2.
  • the window 241 has excursed the sensor bright image and the latter captured the entire radiological image of the surface to be imaged 2 converted into a light image, from a plurality of bright images corresponding to the different irradiated portions 2 ' during scanning.
  • the rotation speed of the disc 240 is synchronized with that of the X-ray beam scanning 1.
  • the scanning of X-ray 1 scanning takes place on the surface to be imaged 2 from top to bottom as shown in the figure 1.
  • the X-ray scanning 1 emerges from a slit 4 whose length, perpendicular to the direction of the scan, corresponds to the dimension of the surface to be imaged 2 also located perpendicular to the scanning direction, to within an enlargement coefficient.
  • This factor is a function of the distance between patient 3 and the X-ray generator 10.
  • the width of the slot 4 located in the scanning direction is very small in front of the other dimension of the surface to be imaged 2 also located in the scanning direction.
  • the slot 4 can be moved back and forth in translation, but we can consider, to overcome this back and forth movement which is always difficult to perform at large speed, to use a rotating disc with a or more slots. In this case the scanning is unidirectional.
  • the dimensions of the irradiated portion 2 'at a given time are modeled on those of slot 4 to the nearest magnification.
  • the windows 241 are slots radial whose dimensions are modeled on those of the irradiated portion 2 ', to within a proportionality coefficient, function of the relative positions and effects of the different elements between patient 3 and the concealment means 24.
  • These slots 241 are located at the periphery of the disc 240. It is better to distribute windows 241 around the entire periphery of the disk especially if the rate of radiological images to be taken is high.
  • the disc 240 will have a large radius in front of the length of windows 241 so that the displacement of a slit in front of the light image sensor 22 either comparable to a translation.
  • the disc 240 will have a large radius in front of the length of windows 241 so that the displacement of a slit in front of the light image sensor 22 either comparable to a translation.
  • the partial concealment means 24 can take the form of an opaque ribbon 242 provided with one or more windows 243 transparent to the exit screen light 206.
  • This strip 242 can be configured in loop and driven by rollers 244 as illustrated in Figure 3. When is facing the light image sensor 22, it moves in translation. His windows 243 are slots transverse to the direction of travel of the ribbon 242. Reference is made to FIG. 4.
  • the X-ray emission can be stopped during one of the two journeys if the partial concealment means have a unidirectional movement in rotation or translation.
  • the concealment means 24 partial are arranged between the output screen 206 and the image sensor 22 light.
  • the partial concealment means 24 can be located either between the screen of output 206 and the optical coupling device 209 as in FIG. 1, or between the optical coupling device 209 and the image sensor 22 as shown in Figure 3.
  • the means of concealment 24 partial are placed between the patient 3 and the conversion means 21 and that they are directly exposed to X-ray.
  • the image sensor could be an electronic image sensor.
  • the image sensor is a light image sensor and the conversion means 21 are materialized by an IIR tube.
  • the partial concealment means 24 are exposed directly to X-ray 1 having passed through patient 3 and have an opaque part 247 with X-rays and one or more parts 248 which lets him pass.
  • the partial concealment means 24 take the form of a disc which forms the opaque part 247 and that this disc has windows 248 in the form of slits which allow the radiological image of the irradiated portion 2 ′ to pass.
  • These partial concealment means 24 having to be partially opaque to the X-rays are made from lead and require resources more powerful to be moved and more expensive than in the variants preceding.
  • the present invention proposes to use means electronic, synchronized with the X-ray scanning movement, to produce an electronic image only in an area that given moment, corresponding to the area irradiated by the X-ray in sweeping movement.
  • These means are static and replace advantageously the mechanical means described above, in the different configurations envisaged.
  • a liquid crystal screen is inserted between the luminous image and an image sensor.
  • This image sensor is preferably electronic (such as the CCD or CMOS matrix sensor of an electronic camera) but we can also consider that it is a simple photographic film which will be exposed area by area as the X-ray is scanned, the film areas that do not correspond to the area irradiated at one time given being hidden at this time.
  • the liquid crystal display is rendered opaque everywhere except in an area (in principle a matrix line if the scanning allows line-by-line irradiation) corresponding to the image actually irradiated by the X-ray.
  • the light image sensor if is electronic, does not collect a signal, except in this area.
  • the X-rays which may have been scattered in scattered directions and which may have produce a bright image not limited to the irradiated portion, will not influence the electronic sensor because it will only observe one area corresponding to the irradiated portion.
  • the means of integration electronics that convert bright image photons or photons of image X into electrons are organized to prevent integration or reading of charges outside the image area which corresponds to the area irradiated at a given time by the scanning X-ray.
  • the partial concealment means 24 are produced by a network shutter 245 with liquid crystal transmission subject to the position of the portion irradiated 2 'by X-ray radiation 1 sweeping. These partial concealment means 24 are used to stop the light from the output screen 206 of the image intensifier tube radiological 21.
  • This shutter 245 may comprise a thin layer 31 of liquid crystals (for example of nematic type in helix) taken in sandwich between two transparent blades 32, 33 sealed together, they same placed between two crossed polarizers 36.
  • liquid crystals for example of nematic type in helix
  • Such a shutter 245 operates in the following manner. At least one of the transparent blades is provided with an array of electrodes. for applying an electric field to portions of the liquid crystals. This is why the shutter 245 is said to be networked. In subjecting part of the liquid crystal layer to a field electric, it becomes opaque and stops the light coming from the screen of output 206. This light can no longer reach image sensor 22 light. In the absence of an electric field, this part is transparent and lets in the light coming from the output screen 206. This light can thus reach the light image sensor 22.
  • each plate 32 33 transparent a network 34, 35 of parallel transparent electrodes E1, E2 oriented transversely to the direction of X-ray scanning 1.
  • An electrode E1 of a network 34 is paired with an electrode E2 of the other network 35 and two electrodes matched are opposite.
  • Each network 34, 35 is connected to a device for command respectively 37, 38 making it possible to apply to its electrodes E1, E2 an appropriate potential and therefore subject to an electric field suitable for the portion of liquid crystal between two electrodes matched to make it opaque.
  • the order of potentials to apply to the electrodes carried out in synchronism with the scanning allows, at each instant, to include in the obturator 245 opaque a transparent zone 246 whose dimensions are such that the light image sensor 22 does not captures only the radiological image of the irradiated portion 2 '.
  • the dimensions of the transparent zone 246 are modeled on those of the irradiated portion 2 'at proportionality coefficient.
  • Electrodes patterns depicted in Figure 7 are only non-limiting examples and others are of course possible to delimit what should remain opaque and what should become transparent.
  • a pattern conventional matrix can be used, provided that the control means, in principle line by line, are organized so as to correspond with the nature of the X scan used.
  • a significant advantage of the means to limit the acquisition the image sensor associated with an X-ray image intensifier tube, in the configuration where they are located between the output screen and the sensor picture is that these limiting means don't just eliminate the light from the X-ray scattered in the patient but also scattered light and X-rays scattered along the entire path between them and the patient. In their absence, this light or this X-ray would be captured by the image sensor and the contrast would be degraded. The best gains in contrast are obtained by placing the most limiting means possible near the light image sensor.
  • the scanning X-ray generator 10 which delivers the X-ray radiation 1 scanning the surface to be imaged 2 of a patient 3 to be examined.
  • the detection system 20 On the other side of the patient 3 is the detection system 20 according to the invention with a light image sensor 22. It includes means 21 for converting the X-ray from the 2 'portions in an IIR tube type light image associated with the light image sensor 22.
  • the image sensor 22 luminous is a CMOS type electronic sensor included for example in a video camera 220.
  • the means 240 for limiting the acquisition of the light image sensor are integrated into the light image sensor.
  • CMOS type sensors are starting to be used. They are very promising because they consume much less that CCD sensors, are much less bulky, offer new possibilities in the acquisition of portions of images, can operate at higher speeds than CCD sensors and are costly lower.
  • each pixel does not only have one photosensor element, for example a photodiode, but also a circuit CMOS transistor with reading amplifier function allowing power quickly read the quantity of charges stored at the level of each pixel which was exposed to a light signal.
  • On the same substrate there are also means for digitizing the signals stored by the pixels and used during reading.
  • the sensor 22 bright image is formed by a plurality of sensitive points or pixels P1 to P9 photosensitive arranged in a matrix and connected between a column conductor Y1 to Y3 and a row conductor X1 to X3. These pixels are symbolized by a square. We only represented nine for do not overload the figure.
  • the pixels P1 to P3 connected to the same line conductor X1 are addressed in at the same time by an addressing device 400 connected to the conductors of line X1 to X3, the amount of light they received is read at each pixel, the data read for each pixel being transferred by the column conductors Y1 to Y3 in a conversion device analog-digital 401 operating in parallel to be digitized there.
  • the means 240 limiting the acquisition of the image sensor 22, in a first phase, just before a 2 'portion is irradiated, control the reset to zero, i.e. the erasure of pixels P4 to P6 of the sensor corresponding to the light image of said portion, and in a second phase, just after the 2 'portion has been irradiated, order the reading of the pixels P4 to P6 corresponding to this bright image. For acquire the bright image of the surface to be imaged 2 all the pixels are subject to this succession of states erasure, exposure, reading.
  • Figures 9a to 9c are used to describe the operation of the means 240. It is assumed that the scanning of X-ray 1 is done linearly as in Figure 1 and that a line of pixels corresponds to a 2 'irradiated portion. The arrow entering block 240 symbolizing the limitation means indicates that these means are synchronized with the X-ray scanning movement.
  • the line conductor X2 to which the pixels P4 to P6 carries an arrow from the addressing device 400, which symbolizes that they have just been deleted or set to zero. They were emptied of any traces of previous exposure. Pixels P1 to P3 are exposed and are shown grayed out while pixels P7 to P9 are read, which is symbolized by arrows on the column conductors Y1 to Y3 from pixels P7 to P9 and directed to the analog-digital conversion device 401.
  • the pixels P4 to P6 are grayed out, which means that they have just been exposed to an illumination delivered by the intensifier tube radiological image.
  • Pixels P1 to P3 are read, which is symbolized by arrows on the column conductors Y1 to Y3 from pixels P1 to P3 and directed to the analog-digital conversion device 401.
  • the pixels P7 to P9 are erased which is symbolized by the arrow, from the addressing device 400, and carried by the line conductor X3 to which pixels P7 to P9 are connected.
  • FIG. 9c we wanted to illustrate the fact that the pixels P4 to P6 are read at this time while the pixels P1 to P3 are erased and the pixels P7 to P9 are exposed.
  • the same symbols as before have been used. In this way, the signals read do not include a broadcast.
  • the generator 10 x-ray scanning which delivers x-ray 1 scanning the surface at image 2 of a patient 3 to be examined.
  • the detection system 20 On the other side of patient 3 is the detection system 20 according to the invention.
  • IIR tube There is no IIR tube. It comprises a solid state image sensor 22, 52 which can be either of the sensor type light image 22, or of the electronic image sensor type 52. Its dimensions are substantially those of the surface to be imaged 2.
  • the sensor cooperates with means 21, 51 for converting X-ray radiation from 2 'portions either as a light image or as an electronic image. If it is about of a conversion into a bright image, the conversion means 21 are of scintillator type which cover the light image sensor 22.
  • the conversion means 51 are made from selenium which covers the electronic image sensor 52.
  • the conversion means 21, 51 are directly facing the X-ray who crossed the patient.
  • the light image sensor 22 can be a sensor whose pixels are formed by a cooperating photosensitive diode with a switch. This type of sensor is well known in radiology digital.
  • the electronic image sensor 52 can comply with what shows FIG. 10.
  • the means 240 for limiting the acquisition of the sensor are integrated in the image sensor 22, 52 and quite comparable to what has been described in figure 8a
  • the sensitive elements of the sensor are subject to a succession of states: erasure or reset, exposure, reading.
  • the electronic image sensor 52 is formed of a plurality of points 53 sensitive to electronic charges, each formed of a capacitive element 54 associated with an element of switching 55 for example a TFT transistor (for the Anglo-Saxon designation Thin Film Transistor) activated especially during playback, arranged in a network like the representations in Figures 9. These points sensitive are made in particular using film deposition technique thin semiconductor materials such as amorphous silicon.
  • This electronic image sensor 52 cooperates with conversion means 51 radiological image - electronic image based on selenium for example.
  • the sensitive points are covered with a layer 51 based on selenium. When crossing the selenium-based layer 51 the X-ray is directly converted into electronic charges (symbolized by an arrow).
  • These electronic charges are stored on the capacitive elements 54.
  • the means for limiting the acquisition of the electronic image sensor operate in a manner comparable to what has been described in FIGS. 8a and 8b.
  • the charges stored on the capacitive elements 54 are read sequentially line by line. By performing a surrender operation zero of the capacitive elements 54 of a line just before they receive electronic charges and a read operation of stored charges in these capacitive elements right after they have received charges, we manages to eliminate the signal linked to the x-rays scattered in the acquisition of the radiological image.

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  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
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Abstract

The invention concerns a radiological image sensing system capable of co-operating with a scanning X-ray generator (10) designed to generate a X-radiation (1) scanning a surface (2) whereof the image is to be produced. The X-radiation (1) irradiates successively portions (2') of the surface whereof the image is to be produced (2). The X-radiation derived from a portion (2') bears a radiological image of said portion. The sensing system comprises an image sensor (22, 52) which is stationary relative to the scanning and dimensioned so as to acquire an image of the whole surface (2) whereof the image is to be produced via the X-radiation derived from the portions (2'). It further comprises means (24, 240) for limiting, at a given time, the image sensor (22, 52) acquisition to that of the image of the irradiated portion (2') at said time, said limiting means being synchronised with the scanning and in geometric correspondence with the irradiated portion (2').

Description

La présente invention est relative à un système de détection d'image radiologique pour générateur de rayons X à balayage apte à fonctionner à cadence élevée.The present invention relates to a detection system image for a scanning X-ray generator capable of operate at high speed.

Les systèmes d'imagerie à rayons X regroupant un système de détection d'image radiologique associé à un générateur de rayons X sont utilisés dans le domaine médical ou dans le domaine du contrôle non destructif. Dans ces types d'application, on cherche à obtenir des images de très bonne qualité et notamment bien contrastées.X-ray imaging systems comprising a system of X-ray image detection associated with an X-ray generator are used in the medical field or in the field of control not destructive. In these types of application, we seek to obtain images of very good quality and particularly well contrasted.

Un système d'imagerie à rayons X classique utilisé dans le domaine médical comporte généralement un générateur de rayons X délivrant un rayonnement X auquel est exposé un patient et, à l'opposé du générateur de rayons X, un système de détection qui détecte le rayonnement X ayant traversé le patient et qui est alors porteur d'une image radiologique. Le générateur de rayons X et le patient sont positionnés l'un par rapport à l'autre de manière que le champ d'irradiation du rayonnement X couvre à un instant donné toute la surface à imager du patient. Le système de détection stationnaire détecte alors simultanément l'image radiologique de toute la surface à imager.A conventional X-ray imaging system used in the medical field generally includes an X-ray generator delivering X-rays to which a patient is exposed and, in contrast to the X-ray generator, a detection system that detects radiation X having passed through the patient and who is then carrying a radiological image. The X-ray generator and the patient are positioned relative to each other. each other so that the x-ray irradiation field covers at a instant given the entire surface to be imaged of the patient. The detection system stationary then simultaneously detects the radiological image of the entire surface to be imaged.

Or une partie importante des rayons X qui traverse le patient est diffusée, c'est-à-dire qu'elle est déviée de sa trajectoire rectiligne initiale. Les rayons déviés ou diffusés sont quand même détectés par le système de détection et l'image détectée est détériorée par rapport à celle qui serait fournie uniquement par les rayons X utiles, c'est-à-dire ceux qui n'ont pas été déviés. Cette détérioration se traduit par une dégradation du contraste.However, a significant part of the X-rays which pass through the patient is diffused, that is to say that it is deviated from its initial rectilinear trajectory. The deflected or scattered rays are still detected by the detection and the detected image is deteriorated compared to what would be supplied only by useful x-rays, i.e. those that have not been diverted. This deterioration results in a degradation of the contrast.

Pour s'affranchir des rayons X diffusés, on place généralement une grille anti-diffusante entre le patient et le système de détection. Cette grille absorbe une grande partie des rayons X diffusés mais absorbe aussi une partie des rayons X utiles, et nécessite en conséquence une dose patient plus élevée. Cette grille est actuellement la seule solution pour éliminer le diffusé dans les systèmes de détection à tube intensificateur d'image radiologique qui sont actuellement les plus utilisés pour faire de l'imagerie radiologique en temps réel. To get rid of scattered X-rays, we generally place an anti-diffusion grid between the patient and the detection system. This grid absorbs a large part of the scattered X-rays but also absorbs some useful x-rays, and therefore requires a dose higher patient. This grid is currently the only solution for eliminate diffuse in intensifier tube detection systems which are currently the most used to make real-time radiological imaging.

Une autre solution pour s'affranchir des rayons X diffusés sans augmenter la dose de rayons X consiste à utiliser un générateur de rayons X à balayage qui irradie la surface à imager de manière progressive, la zone irradiée instantanée n'étant qu'une portion de la surface à imager.Another solution to get rid of X-rays scattered without increasing the dose of x-rays involves using an x-ray generator scanning which irradiates the surface to be imaged in a progressive manner, the area instant irradiated being only a portion of the surface to be imaged.

Dans ce cas, le générateur de rayons X est associé à un système de détection mobile qui est synchronisé avec le mouvement de balayage du rayonnement X et en correspondance géométrique avec la zone irradiée instantanée. Le système de détection est généralement formé d'éléments capteurs à l'état solide recouverts d'un matériau scintillateur et arrangés en barrette, les dimensions de cette barrette sont telles qu'elle ne reçoit que l'image de la zone irradiée instantanée. Elle ne détecte donc pas les rayons X diffusés qui sont déviés mais que des rayons X ayant traversé directement le patient.In this case, the X-ray generator is associated with a system mobile detection which is synchronized with the scanning movement of the X-ray and in geometric correspondence with the irradiated area Instant. The detection system is generally made up of elements solid state sensors covered with scintillator material and arranged in bar, the dimensions of this bar are such that it only receives the image of the instant irradiated area. It therefore does not detect the rays Scattered X which are deflected but which X-rays have passed directly through the patient.

Or la mise en oeuvre de tels systèmes de détection nécessite des dispositifs mécaniques compliqués.However, the implementation of such detection systems requires complicated mechanical devices.

Les dimensions de la barrette sont conditionnées par celles de la zone irradiée instantanée. Il n'est donc pas possible, sans changer de barrette, de vouloir optimiser le compromis entre les dimensions de la zone irradiée et le débit de rayons X.The dimensions of the bar are conditioned by those of the instant irradiated area. It is therefore not possible, without changing bar, to want to optimize the compromise between the dimensions of the area irradiated and the X-ray rate.

Il n'est pas aisé de déplacer la barrette d'éléments capteurs à l'état solide au rythme du rayonnement X balayant, surtout si la vitesse de balayage requise est élevée, comme dans les examens de fluoroscopie dans lesquels plusieurs dizaines d'images par secondes doivent être réalisées.It is not easy to move the array of sensor elements to the solid state to the rhythm of the sweeping X-ray, especially if the speed of required scan is high, as in fluoroscopy exams in which several tens of images per second must be taken.

La mécanique de précision utilisée pour mouvoir le système de détection représente un poste important dans le coût de tels systèmes de détection.The precision mechanics used to move the system detection represents an important item in the cost of such detection systems detection.

On a également proposé des systèmes de détection dans lesquels une fente dans un obturateur mécanique se déplace au niveau du détecteur, en synchronisme avec le balayage exécuté par le faisceau de rayons X. Ces systèmes mécaniques ne permettent pas une grande cadence de balayage et sont lourds et coûteux. Le brevet EP 0 083 465 en donne un exemple.Detection systems have also been proposed in which a slot in a mechanical shutter moves at the detector, in synchronism with the scanning carried out by the beam of X-rays. These mechanical systems do not allow a high rate and are heavy and expensive. EP 0 083 465 gives one example.

La présente invention, tout en continuant à éliminer le diffusé des images radiologiques, vise à s'affranchir des problèmes sus mentionnés, notamment liés aux doses à administrer au patient, au mouvement mécanique du capteur d'image ou d'autres pièces telles que des fentes dans des obturateurs du côté de la détection ; elle permet d'atteindre des vitesses de balayage compatibles avec celles requises en mode fluoroscopie.The present invention, while continuing to eliminate the scattering of radiological images, aims to overcome the above-mentioned problems, especially related to the doses to be administered to the patient, to the movement mechanics of the image sensor or other parts such as slots in shutters on the detection side; it allows to reach speeds compatible with those required in fluoroscopy mode.

Pour y parvenir la présente invention propose un système de détection d'image radiologique apte à coopérer avec un générateur de rayons X à balayage destiné à produire un rayonnement X balayant une surface à imager, ce rayonnement X irradiant portion après portion la surface à imager, le rayonnement X issu d'une portion étant porteur d'une image radiologique de ladite portion. Le système comporte un capteur d'image qui est stationnaire vis à vis du balayage et qui est dimensionné pour pouvoir acquérir une image de toute la surface à imager via le rayonnement X issu des portions, le système de détection comportant de plus des moyens électroniques pour limiter, à un instant donné, l'acquisition du capteur d'image à une zone correspondant à la portion irradiée à cet instant, ces moyens de limitation électronique étant en synchronisme avec le balayage et en correspondance géométrique avec la portion irradiée.To achieve this, the present invention proposes a system of radiological image detection able to cooperate with a generator X-ray scanning to produce X-ray scanning a surface to be imaged, this X-ray irradiating portion after portion the surface to be imaged, X-ray radiation from a portion carrying an image radiological of said portion. The system includes an image sensor which is stationary with respect to the sweep and which is dimensioned to be able to acquire an image of the entire surface to be imaged via X-ray radiation portions, the detection system further comprising means electronic to limit, at a given time, the acquisition of the sensor image to an area corresponding to the portion irradiated at this time, these electronic limitation means being in synchronism with the scanning and in geometric correspondence with the irradiated portion.

Les moyens de limitation électronique sont purement statiques contrairement aux moyens de limitation mécaniques tournants ou défilants de l'art antérieur.Electronic limitation means are purely static unlike rotating or scrolling mechanical limiting means of the prior art.

Dans une première configuration, les moyens pour limiter l'acquisition du capteur d'image peuvent être des moyens d'occultation partielle du capteur d'image vis à vis de la surface à imager, externes au capteur d'image. Un écran à cristaux liquides dont le balayage est commandé en synchronisme avec le balayage du faisceau de rayons X, permet de ne laisser passer vers une caméra de détection qu'une zone d'image limitée correspondant à celle qui est illuminée à cet instant par le détecteur.In a first configuration, the means to limit the acquisition of the image sensor can be means for partially obscuring the image sensor with respect to the surface to be imaged, external to the sensor image. A liquid crystal display whose scanning is controlled by synchronization with the scanning of the X-ray beam, makes it possible not to pass to a detection camera only a limited image area corresponding to that which is illuminated at this instant by the detector.

Le capteur d'image peut être un capteur d'image lumineuse et coopérer avec des moyens pour convertir le rayonnement X issu des portions en image lumineuse.The image sensor can be a bright image sensor and cooperate with means to convert X-rays from portions in bright image.

Dans un autre mode de réalisation, le capteur d'image peut être un capteur d'image électronique et coopérer avec des moyens pour convertir le rayonnement X issu des portions directement en image électronique. Les capteurs au sélénium sont aptes à faire cette conversion directe.In another embodiment, the image sensor can be a electronic image sensor and cooperate with means to convert the X-ray from the portions directly in electronic image. The selenium sensors are able to do this direct conversion.

Dans les deux cas, les moyens pour limiter l'acquisition du capteur d'image peuvent être intégrés au capteur d'image, celui-ci étant organisé pour empêcher toute acquisition d'image hors de la zone qui correspond à une portion d'image éclairée à un instant par le faisceau de rayons X.In both cases, the means to limit the acquisition of the sensor can be integrated into the image sensor, this being organized to prevent any image acquisition outside the area that corresponds to an image portion illuminated at an instant by the X-ray beam.

Le capteur d'image peut être de type état solide et notamment de type CCD, de type CMOS, à diodes photosensibles, à éléments capacitifs.The image sensor can be of the solid state type and in particular of the type CCD, CMOS type, with photosensitive diodes, with capacitive elements.

Le capteur d'image peut être un capteur d'image lumineuse formé d'une pluralité de pixels photosensibles à l'état solide, les moyens pour limiter l'acquisition du capteur d'image peuvent commander, juste avant qu'une portion ne soit irradiée, un effacement des pixels du capteur correspondants à l'image lumineuse de ladite portion irradiée, et une lecture desdits pixels juste après l'irradiation de la dite portion.The image sensor can be a light image sensor formed of a plurality of photosensitive pixels in the solid state, the means for limit the acquisition of the image sensor can order, just before that a portion is not irradiated, an erasure of the pixels of the sensor corresponding to the light image of said irradiated portion, and a reading of said pixels just after the irradiation of said portion.

Le capteur d'image peut être un capteur d'image électronique formé d'une pluralité d'éléments capacitifs et les moyens pour limiter l'acquisition du capteur d'image peuvent commander juste avant qu'une portion ne soit irradiée, une mise à zéro de la charge des éléments capacitifs correspondant à l'image électronique de ladite portion irradiée et une lecture des charges stockées dans lesdits éléments capacitifs juste après l'irradiation de la dite portion.The image sensor can be a formed electronic image sensor of a plurality of capacitive elements and the means for limiting the acquisition of the image sensor can order just before a portion is irradiated, resetting the charge of the corresponding capacitive elements to the electronic image of said irradiated portion and a reading of the charges stored in said capacitive elements just after the irradiation of said portion.

Il est aussi possible que le capteur d'image lumineuse soit de type film photographique ou film cinématographique ; dans ce cas on utilisera en principe un écran à cristaux liquides pour effectuer la limitation d'image.It is also possible that the light image sensor is of the film type. photographic or cinematographic film; in this case we will use principle a liquid crystal display to perform image limitation.

Les moyens pour convertir le rayonnement X en image lumineuse peuvent être de type intensificateur d'image radiologique ou scintillateur déposé sur une matrice photosensible à l'état solide, tandis que les moyens pour convertir le rayonnement X en image électronique peuvent être réalisés à base de sélénium.Means for converting X-rays into bright images can be of radiological image intensifier or scintillator type deposited on a photosensitive matrix in the solid state, while the means to convert x-ray into electronic image can be realized based on selenium.

Le système de détection peut comporter des moyens de traitement de l'image captée par le capteur d'image de manière à reconstruire une image complète de l'image radiologique de la surface à imager à partir des images des zones irradiées.The detection system may include means for processing the image captured by the image sensor so as to reconstruct an image complete radiological image of the surface to be imaged from the images irradiated areas.

D'autres caractéristiques et avantages de l'invention apparaítront à la lecture de la description qui suit illustrée par les figures annexées qui représentent :

  • la figure 1 une coupe d'un exemple de système de détection d'image associé à un générateur de rayons X à balayage, dans lequel les moyens de limitation de l'acquisition du capteur d'image sont des moyens d'occultation partielle mécaniques ;
  • la figure 2 une vue de face des moyens limitant l'acquisition du capteur d'image utilisés dans le système de détection d'image de la figure 1 ;
  • la figure 3 une coupe d'un second exemple de système de détection d'image associé à un générateur de rayons X à balayage, dans lequel les moyens de limitation de l'acquisition du capteur d'image sont des moyens d'occultation partielle mécaniques ;
  • la figure 4 une vue de face des moyens limitant l'acquisition du capteur d'image utilisés dans le système de détection d'image de la figure 3 ;
  • la figure 5 une coupe d'un troisième exemple de système de détection d'image associé à un générateur de rayons X à balayage, dans lequel les moyens de limitation de l'acquisition du capteur d'image sont des moyens d'occultation partielle mécaniques ;
  • la figure 6 une coupe d'un quatrième exemple de système de détection d'image selon l'invention associé à un générateur de rayons X à balayage, dans lequel les moyens de limitation de l'acquisition du capteur d'image sont des moyens d'occultation partielle électroniques et externes au capteur d'image ;
  • la figure 7 une vue de face des moyens d'occultation partielle utilisés dans le système de détection d'image de la figure 6 ;
  • les figures 8a, 8b, en coupe, deux nouveaux exemples de système de détection d'image selon l'invention dans lesquels les moyens limitant l'acquisition du capteur d'image sont intégrés au capteur d'image ;
  • les figures 9a, 9b, 9c trois vues de face du capteur d'image de la figure 8a, à des instants différents, permettant de comprendre le fonctionnement des moyens limitant son acquisition ;
  • la figure 10, en coupe partielle un capteur d'image électronique pouvant être intégré dans un système de détection d'image selon l'invention.
Other characteristics and advantages of the invention will appear on reading the following description illustrated by the appended figures which represent:
  • FIG. 1 is a section through an example of an image detection system associated with a scanning X-ray generator, in which the means for limiting the acquisition of the image sensor are mechanical partial occultation means;
  • Figure 2 a front view of the means limiting the acquisition of the image sensor used in the image detection system of Figure 1;
  • FIG. 3 is a section through a second example of an image detection system associated with a scanning X-ray generator, in which the means for limiting the acquisition of the image sensor are mechanical partial occultation means ;
  • Figure 4 a front view of the means limiting the acquisition of the image sensor used in the image detection system of Figure 3;
  • FIG. 5 is a section through a third example of an image detection system associated with a scanning X-ray generator, in which the means for limiting the acquisition of the image sensor are mechanical partial occultation means ;
  • FIG. 6 is a section of a fourth example of an image detection system according to the invention associated with a scanning X-ray generator, in which the means for limiting the acquisition of the image sensor are means of 'partial blackout electronic and external to the image sensor;
  • Figure 7 a front view of the partial concealment means used in the image detection system of Figure 6;
  • FIGS. 8a, 8b, in section, two new examples of image detection system according to the invention in which the means limiting the acquisition of the image sensor are integrated into the image sensor;
  • Figures 9a, 9b, 9c three front views of the image sensor of Figure 8a, at different times, to understand the operation of the means limiting its acquisition;
  • FIG. 10, in partial section, an electronic image sensor that can be integrated into an image detection system according to the invention.

Sur ces figures les mêmes éléments portent la même référence et les échelles ne sont pas respectées dans un souci de clarté.In these figures the same elements bear the same reference and the scales are not respected for the sake of clarity.

La figure 1 représente un système de détection d'image 20. Ce système de détection d'image est utilisé dans un équipement d'imagerie médicale comportant un générateur 10 de rayons X à balayage qui délivre un rayonnement X 1 balayant une surface à imager 2 d'un patient 3 à examiner. A un instant donné, le rayonnement X 1 n'irradie qu'une portion 2' de la surface à imager 2. A l'issue d'un balayage complet, toute la surface à imager 2 a été irradiée portion par portion. Le générateur 10 de rayons X à balayage peut être à balayage de fente, c'est à dire avec une fente qui se déplace devant une source de rayons X ou être à fente fixe comme décrit par exemple dans la demande de brevet française FR A- 2 795 864. Dans ce cas, c'est en agissant sur l'orientation variable du faisceau d'électrons par rapport à une cible qu'on fait varier l'angle d'incidence du faisceau X sur le corps à irradier : la vitesse de balayage peut être élevée, en l'absence de mouvements de pièces mécaniques.FIG. 1 represents an image detection system 20. This image detection system is used in imaging equipment medical comprising a scanning X-ray generator 10 which delivers a X-ray 1 scanning a surface to be imaged 2 of a patient 3 to be examined. At a given instant, the X-ray radiation only irradiates a portion 2 ′ of the surface to be imaged 2. After a complete scan, the entire surface to be imaged imager 2 has been irradiated portion by portion. The X-ray generator 10 at scan can be a slot scan, i.e. with a slot that moves in front of an X-ray source or be fixed slit as described by example in French patent application FR A- 2 795 864. In this case, it is by acting on the variable orientation of the electron beam by relative to a target that is varied the angle of incidence of the X beam on the body to be irradiated: the scanning speed may be high, in the absence of movements of mechanical parts.

De l'autre côte du patient 3, c'est à dire à l'opposé du générateur 10 de rayons X à balayage se trouve le système de détection 20. Il détecte le rayonnement X 1 ayant traversé le patient, ce rayonnement X étant porteur d'une image radiologique.On the other side of patient 3, i.e. opposite the generator 10 scanning x-ray is the detection system 20. It detects the X-ray 1 having passed through the patient, this X-ray being carrier of a radiological image.

Le système de détection 20 d'image comporte un capteur d'image 22 destiné à acquérir via le rayonnement X issu des portions, une image de la surface à imager. Ce capteur d'image 22 est stationnaire vis à vis du balayage et il possède des dimensions lui permettant d'acquérir une image de toute la surface à imager 2. Il n'est pas mis en mouvement ni limité en dimensions à celles de la portion irradiée. En supprimant les moyens pour mettre en mouvement le capteur puisqu'il est stationnaire, on s'affranchit notamment des problèmes mécaniques rencontrés avec un capteur déplaçable au rythme du rayonnement balayant..The image detection system 20 includes an image sensor 22 intended to acquire, via the X-ray radiation coming from the portions, an image of the surface to be imaged. This image sensor 22 is stationary with respect to the scan and it has dimensions allowing it to acquire an image of the entire surface to be imaged 2. It is neither set in motion nor limited in dimensions to those of the irradiated portion. By removing the means for set the sensor in motion since it is stationary, we get rid of in particular mechanical problems encountered with a sensor displaceable to the rhythm of the sweeping radiation.

Le système de détection d'image 20 comporte également des moyens 24 pour limiter, à un instant donné, l'acquisition du capteur d'image 22 essentiellement à celle de l'image de la portion 2' irradiée à cet instant, ces moyens étant en synchronisme avec le balayage et en correspondance géométrique avec la portion irradiée 2'. Une liaison en pointillés illustre le synchronisme entre le rayonnement X 1 balayant et les moyens 24 limitant l'acquisition du capteur d'image 22.The image detection system 20 also includes means 24 to limit, at a given instant, the acquisition of the image sensor 22 essentially to that of the image of the portion 2 'irradiated at this instant, these means being in synchronism with the scan and in correspondence geometric with the irradiated portion 2 '. A dotted line illustrates the synchronism between the scanning X-ray 1 and the means 24 limiting the acquisition of the image sensor 22.

Dans l'exemple décrit, le capteur d'image 22 est un capteur d'image lumineuse et il coopère avec des moyens 21 pour convertir le rayonnement X porteur de l'image radiologique en une image lumineuse reçue par le capteur d'image 22 lumineuse. In the example described, the image sensor 22 is a sensor of bright image and it cooperates with means 21 to convert the X-ray carrying the radiological image into a bright image received by the light image sensor 22.

On pourrait envisager d'utiliser un capteur d'image électronique à la place du capteur d'image lumineuse comme le montre la figure 10 décrite ultérieurement. Ce capteur est destiné à capter des charges électroniques et il coopère avec des moyens pour convertir directement le rayonnement X porteur de l'image radiologique en une image électronique.We could consider using an electronic image sensor to the place of the light image sensor as shown in Figure 10 described later. This sensor is intended to pick up electronic charges and it cooperates with means to directly convert the X-ray carrying the radiological image into an electronic image.

Dans l'exemple décrit à la figure 1, le système de détection 20 comporte en tant que moyens de conversion un tube intensificateur d'image radiologique 21 connu sous le sigle IIR, suivi du capteur d'image 22 lumineuse.In the example described in FIG. 1, the detection system 20 includes as image conversion means an image intensifier tube radiological 21 known by the acronym IIR, followed by the image sensor 22 light.

Les moyens 24 limitant l'acquisition du capteur d'image 22 lumineuse sont des moyens mécaniques d'occultation partielle du capteur d'image 22 lumineuse. Ces moyens 24 d'occultation partielle sont externes au capteur d'image 22 lumineuse, ils masquent partiellement le capteur d'image 22 de manière à ce qu'il ne capte, à un instant donné, que l'image lumineuse de la portion irradiée 2' par le rayonnement X 1 balayant.The means 24 limiting the acquisition of the image sensor 22 light are mechanical means for partially obscuring the sensor 22 bright image. These partial concealment means 24 are external to the light image sensor 22, they partially mask the sensor image 22 so that it captures, at a given instant, only the image light of the portion irradiated 2 ′ by the scanning X 1 radiation.

On va voir maintenant plus en détails le système de détection d'image dans sa réalisation de la figure 1.We will now see in more detail the detection system image in its realization of figure 1.

Le tube IIR 21 comporte de manière classique une enceinte 200 étanche au vide fermée à une extrémité par une fenêtre d'entrée 201 par laquelle pénètre le rayonnement X balayant 1 ayant traversé le patient 3.The IIR tube 21 conventionally comprises an enclosure 200 vacuum tight closed at one end by an entrance window 201 by which penetrates the scanning X-ray 1 having passed through the patient 3.

Le rayonnement X balayant 1 rencontre ensuite un écran d'entrée 202 dont la fonction est de traduire l'intensité du rayonnement X en une quantité d'électrons. Cet écran d'entrée 202 est dimensionné de manière à pouvoir être frappé par le rayonnement X 1 quel que soit le lieu d'impact sur la fenêtre d'entrée 201. L'écran d'entrée 202 comprend généralement un scintillateur 203 associé à une photocathode 204. Le scintillateur 203 convertit le rayonnement X 1 balayant en photons visibles qui sont eux-mêmes convertis en électrons par la photocathode 204.The X-ray scanning 1 then meets an input screen 202 whose function is to translate the intensity of X-rays into a amount of electrons. This input screen 202 is dimensioned so as to be able to be struck by X 1 radiation regardless of the place of impact on the input window 201. The input screen 202 generally comprises a scintillator 203 associated with a photocathode 204. The scintillator 203 converts the scanning X-ray 1 into visible photons which are themselves converted to electrons by photocathode 204.

Un jeu d'électrodes 205 accélère les électrons et les focalise sur un écran de sortie cathodoluminescent 206. L'écran de sortie 206 luminescent est disposé à proximité d'une fenêtre de sortie 207 située à l'opposé de la fenêtre d'entrée 201. L'impact des électrons sur l'écran luminescent 206 permet de reconstituer l'image lumineuse qui s'est formée sur la photocathode 204. Cette image lumineuse traduit à un instant donné l'image radiologique de la portion irradiée 2'. A set of electrodes 205 accelerates the electrons and focuses them on a cathodoluminescent output screen 206. The output screen 206 luminescent is disposed near an exit window 207 located at opposite of the input window 201. The impact of electrons on the screen luminescent 206 allows to reconstruct the luminous image which has formed on photocathode 204. This bright image translates at a given time the radiological image of the irradiated portion 2 '.

Cette image lumineuse comporte les défauts évoqués plus haut car avec uniquement le rayonnement X balayant, des rayons X diffusés percutent la photocathode 204 et leur effet est visible sur l'écran de sortie 206.This bright image contains the faults mentioned above because with only the scanning X-ray, scattered X-rays strike photocathode 204 and their effect is visible on the output screen 206.

L'image affichée par l'écran de sortie 206 est alors transmise vers le capteur d'image 22 lumineuse. Ce capteur d'image 22 lumineuse est généralement un capteur de type CCD (pour Charge-Coupled Device en langue anglaise ou dispositif à couplage de charges) inclus dans une caméra vidéo 220, un film cinématographique placé dans une caméra cinématographique ou un film photographique inclus dans un appareil photographique. Le capteur CCD peut être remplacé avantageusement par un capteur de type CMOS qui fonctionne de manière très semblable.The image displayed by the output screen 206 is then transmitted to the light image sensor 22. This bright image sensor 22 is generally a CCD type sensor (for Charge-Coupled Device in English language or charge coupled device) included in a camera video 220, a cinematographic film placed in a camera cinematographic or photographic film included in a camera photographic. The CCD sensor can advantageously be replaced by a CMOS type sensor that works very similarly.

La transmission de l'image lumineuse affichée par l'écran de sortie 206 vers le capteur d'image 22 lumineuse se fait généralement par l'intermédiaire d'un dispositif optique de couplage 209, disposé à l'extérieur du tube IIR 21 et centré sur un axe XX' longitudinal du tube IIR, axe autour duquel est également centré l'écran de sortie 206. Ce dispositif optique de couplage 209 peut comporter des lentilles et/ou des fibres optiques....The transmission of the bright image displayed by the screen of output 206 to the light image sensor 22 is generally done by via an optical coupling device 209, arranged outside of the IIR tube 21 and centered on a longitudinal axis XX 'of the IIR tube, axis around which is also centered the output screen 206. This optical device for coupling 209 may include lenses and / or optical fibers.

Le capteur d'image 22 lumineuse est dimensionné pour recevoir en totalité l'image de la surface à imager 2, comme c'est le cas dans les systèmes de détection d'image classiques à faisceau de rayons X stationnaire.The light image sensor 22 is sized to receive the entire image of the surface to be imaged 2, as is the case in conventional X-ray beam image detection systems stationary.

Il est associé à des moyens d'occultation 24 partielle synchronisés avec le mouvement de balayage du rayonnement X 1 balayant et en correspondance géométrique avec la portion 2' irradiée de la surface à imager. En étant masqué partiellement, le capteur d'image 22 lumineuse ne peut capter que l'image lumineuse de la portion irradiée 2' par le rayonnement X 1 balayant. Ces moyens d'occultation 24 empêchent que le capteur d'image 22 lumineuse ne capte la trace de rayons X diffusés dans le patient 3.It is associated with synchronized partial concealment means 24 with the scanning movement of X-ray 1 scanning and geometric correspondence with the irradiated portion 2 'of the surface to imaged. By being partially masked, the light image sensor 22 does not can capture that the bright image of the portion irradiated 2 'by the 1 x scanning radiation. These concealment means 24 prevent the light image sensor 22 does not pick up the trace of X-rays scattered in the patient 3.

Le système de détection d'image 20 peut comporter un dispositif d'acquisition et de traitement de signaux 23 qui traite et stocke des signaux relatifs à l'image que lui délivre le capteur d'image 22 lumineuse. Après traitement approprié, ces signaux peuvent être observés sur un dispositif de visualisation 25. The image detection system 20 may include a device signal acquisition and processing 23 which processes and stores signals relating to the image delivered to it by the light image sensor 22. After appropriate treatment, these signals can be observed on a display 25.

Dans l'exemple de la figure 1, le capteur d'image 22 lumineuse est stationnaire vis à vis du balayage tandis que les moyens d'occultation partielle 24 sont mobiles et plus particulièrement rotatifs par rapport au capteur d'image 22 lumineuse. Ils sont placés entre l'écran de sortie 206 et le capteur d'image 22 lumineuse.In the example of FIG. 1, the light image sensor 22 is stationary with respect to the scanning while the concealment means partial 24 are movable and more particularly rotatable relative to the 22 bright image sensor. They are placed between the output screen 206 and the light image sensor 22.

Ils prennent la forme d'un disque 240 opaque à la lumière provenant de l'écran de sortie 206, et doté d'au moins une fenêtre 241 laissant passer la lumière. Cette fenêtre 241 peut être tout simplement une ouverture dans le disque qui laisse passer l'image lumineuse de la portion irradiée 2'.They take the form of a disc 240 opaque to light from the output screen 206, and provided with at least one window 241 letting the light pass. This window 241 can simply be a opening in the disc which lets pass the bright image of the portion irradiated 2 '.

Le disque 240 est entraíné en rotation de manière que sa fenêtre 241 se déplace en synchronisme avec le rayonnement X 1 balayant la surface à imager 2. Lorsque le rayonnement X 1 balayant a excursionné totalement la surface à imager 2, la fenêtre 241 a excursionné le capteur d'image lumineuse et ce dernier à capté la totalité de l'image radiologique de la surface à imager 2 convertie en image lumineuse, à partir d'une pluralité d'images lumineuses correspondant aux différentes portions irradiées 2' pendant la balayage. La vitesse de rotation du disque 240 est synchronisée avec celle du faisceau de rayons X balayant 1.The disc 240 is rotated so that its window 241 moves in synchronism with the X-ray 1 scanning the surface to be imaged 2. When the scanning X-ray 1 has excursed totally the surface to be imaged 2, the window 241 has excursed the sensor bright image and the latter captured the entire radiological image of the surface to be imaged 2 converted into a light image, from a plurality of bright images corresponding to the different irradiated portions 2 ' during scanning. The rotation speed of the disc 240 is synchronized with that of the X-ray beam scanning 1.

On suppose que le balayage du rayonnement X 1 balayant s'effectue sur la surface à imager 2 de haut en bas comme le montre la figure 1. Le rayonnement X balayant 1 émerge d'une fente 4 dont la longueur, perpendiculaire à la direction du balayage, correspond à la dimension de la surface à imager 2 située également perpendiculairement à la direction de balayage, à un coefficient d'agrandissement près. Ce facteur est fonction de la distance séparant le patient 3 du générateur de rayons X 10. La largeur de la fente 4 située dans le sens du balayage est très petite devant l'autre dimension de la surface à imager 2 située également dans le sens du balayage. La fente 4 peut-être animée d'un mouvement de va-et-vient en translation, mais on peut envisager, pour s'affranchir de ce mouvement de va-et-vient qui est toujours difficile à réaliser à grande vitesse, d'utiliser un disque animé d'un mouvement de rotation et doté d'une ou plusieurs fentes. Dans ce cas le balayage est unidirectionnel.Suppose that the scanning of X-ray 1 scanning takes place on the surface to be imaged 2 from top to bottom as shown in the figure 1. The X-ray scanning 1 emerges from a slit 4 whose length, perpendicular to the direction of the scan, corresponds to the dimension of the surface to be imaged 2 also located perpendicular to the scanning direction, to within an enlargement coefficient. This factor is a function of the distance between patient 3 and the X-ray generator 10. The width of the slot 4 located in the scanning direction is very small in front of the other dimension of the surface to be imaged 2 also located in the scanning direction. The slot 4 can be moved back and forth in translation, but we can consider, to overcome this back and forth movement which is always difficult to perform at large speed, to use a rotating disc with a or more slots. In this case the scanning is unidirectional.

Les dimensions de la portion irradiée 2' à un instant donné sont calquées sur celles de la fente 4 au coefficient d'agrandissement près. The dimensions of the irradiated portion 2 'at a given time are modeled on those of slot 4 to the nearest magnification.

Sur l'exemple de la figure 1, les fenêtres 241 sont des fentes radiales dont les dimensions sont calquées sur celles de la portion irradiée 2', à un coefficient de proportionnalité près, fonction des positions relatives et des effets des différents éléments se trouvant entre le patient 3 et les moyens d'occultation 24.In the example of FIG. 1, the windows 241 are slots radial whose dimensions are modeled on those of the irradiated portion 2 ', to within a proportionality coefficient, function of the relative positions and effects of the different elements between patient 3 and the concealment means 24.

Ces fentes 241 sont situées à la périphérie du disque 240. Il est préférable de répartir les fenêtres 241 sur toute la périphérie du disque surtout si la cadence des images radiologiques à prendre est élevée.These slots 241 are located at the periphery of the disc 240. It is better to distribute windows 241 around the entire periphery of the disk especially if the rate of radiological images to be taken is high.

Dans le cas où le balayage se fait en translation, le disque 240 aura un rayon grand devant la longueur des fenêtres 241 de sorte que le déplacement d'une fente devant le capteur d'image 22 lumineuse soit assimilable à une translation. On se réfère à la figure 2.In the case where the scanning is done in translation, the disc 240 will have a large radius in front of the length of windows 241 so that the displacement of a slit in front of the light image sensor 22 either comparable to a translation. We refer to figure 2.

Les moyens d'occultation 24 partielle peuvent prendre la forme d'un ruban opaque 242 doté d'une ou plusieurs fenêtres 243 transparentes à la lumière de l'écran de sortie 206. Ce ruban 242 peut être configuré en boucle et entraíné par des galets 244 comme l'illustre la figure 3. Lorsqu'il est face au capteur d'image 22 lumineuse, il se déplace en translation. Ses fenêtres 243 sont des fentes transversales à la direction de déplacement du ruban 242. On se réfère à la figure 4.The partial concealment means 24 can take the form of an opaque ribbon 242 provided with one or more windows 243 transparent to the exit screen light 206. This strip 242 can be configured in loop and driven by rollers 244 as illustrated in Figure 3. When is facing the light image sensor 22, it moves in translation. His windows 243 are slots transverse to the direction of travel of the ribbon 242. Reference is made to FIG. 4.

Si le mouvement de balayage est un mouvement de va et vient bidirectionnel, l'émission des rayons X peut-être arrêtée pendant un des deux trajets si les moyens d'occultation partielle sont animés d'un mouvement unidirectionnel en rotation ou en translation.If the sweep movement is a back and forth movement bidirectional, the X-ray emission can be stopped during one of the two journeys if the partial concealment means have a unidirectional movement in rotation or translation.

Dans les deux configurations décrites, les moyens d'occultation 24 partielle sont disposés entre l'écran de sortie 206 et le capteur d'image 22 lumineuse. Dans le cas où un dispositif optique de couplage 209 est interposé entre l'écran de sortie 206 et le capteur d'image 22 lumineuse, les moyens d'occultation 24 partielle peuvent se trouver soit entre l'écran de sortie 206 et le dispositif optique de couplage 209 comme sur la figure 1, soit entre le dispositif optique de couplage 209 et le capteur d'image 22 lumineuse comme sur la figure 3.In the two configurations described, the concealment means 24 partial are arranged between the output screen 206 and the image sensor 22 light. In the case where an optical coupling device 209 is interposed between the output screen 206 and the light image sensor 22, the partial concealment means 24 can be located either between the screen of output 206 and the optical coupling device 209 as in FIG. 1, or between the optical coupling device 209 and the image sensor 22 as shown in Figure 3.

On pourrait aussi envisager que les moyens d'occultation 24 partielle soient placés entre le patient 3 et les moyens de conversion 21 et qu'ils soient directement exposés au rayonnement X. Dans cette variante, le capteur d'image pourrait être un capteur d'image électronique. We could also consider that the means of concealment 24 partial are placed between the patient 3 and the conversion means 21 and that they are directly exposed to X-ray. In this variant, the image sensor could be an electronic image sensor.

Dans l'exemple illustré à la figure 5, le capteur d'image est un capteur d'image lumineuse et les moyens de conversion 21 sont matérialisés par un tube IIR. Les différences avec les configurations décrites précédemment sont que maintenant les moyens d'occultation partielle 24 sont exposés directement au rayonnement X 1 ayant traversé le patient 3 et comportent une partie opaque 247 au rayonnement X et une ou plusieurs parties 248 qui le laisse passer. On suppose sur cette figure 5 que les moyens d'occultation partielle 24 prennent la forme d'un disque qui forme la partie opaque 247 et que ce disque est doté de fenêtres 248 sous forme de fentes qui laissent passer l'image radiologique de la portion irradiée 2'. Ces moyens d'occultation partielle 24 devant être partiellement opaques au rayonnement X sont réalisés à base de plomb et nécessitent des moyens plus puissants pour être déplacés et plus onéreux que dans les variantes précédentes.In the example illustrated in FIG. 5, the image sensor is a light image sensor and the conversion means 21 are materialized by an IIR tube. Differences with the described configurations previously are that now the partial concealment means 24 are exposed directly to X-ray 1 having passed through patient 3 and have an opaque part 247 with X-rays and one or more parts 248 which lets him pass. It is assumed in this figure 5 that the partial concealment means 24 take the form of a disc which forms the opaque part 247 and that this disc has windows 248 in the form of slits which allow the radiological image of the irradiated portion 2 ′ to pass. These partial concealment means 24 having to be partially opaque to the X-rays are made from lead and require resources more powerful to be moved and more expensive than in the variants preceding.

Les exemples précédents font comprendre les principes de mise en correspondance d'une partie de corps, irradiée à un instant donné par le faisceau de rayons X qui balaye le corps, avec une partie d'image lumineuse correspondante et avec une partie d'image électronique correspondante, ou bien directement avec une partie d'image électronique correspondante lorsque le système convertit directement les rayons X en image électronique sans passer par une image lumineuse. Mais ces exemples montrent aussi que cette mise en correspondance est faite par des moyens mécaniques, essentiellement sous forme de fentes qui se déplacent en synchronisme avec le balayage du faisceau X.The previous examples explain the principles of setting in correspondence of a body part, irradiated at a time given by the beam of X-rays which scans the body, with a part of bright image corresponding and with a corresponding electronic image part, or well directly with a corresponding electronic image part when the system directly converts x-rays into an electronic image without going through a bright image. But these examples also show that this matching is done by mechanical means, essentially in the form of slots which move synchronously with X-ray scanning.

La présente invention propose d'utiliser des moyens électroniques, synchronisés avec le mouvement de balayage du faisceau X, pour ne produire une image électronique que dans une zone qui, à un moment donné, correspondant à la zone irradiée par le faisceau X en mouvement de balayage. Ces moyens sont statiques et remplacent avantageusement les moyens mécaniques décrits ci-dessus, dans les différentes configurations envisagées.The present invention proposes to use means electronic, synchronized with the X-ray scanning movement, to produce an electronic image only in an area that given moment, corresponding to the area irradiated by the X-ray in sweeping movement. These means are static and replace advantageously the mechanical means described above, in the different configurations envisaged.

Deux réalisations principales sont prévues.Two main achievements are planned.

Dans la première, qui est applicable lorsqu'une partie de la chaíne de conversion des rayons X en image électronique passe par une image lumineuse, on intercale un écran à cristaux liquides entre l'image lumineuse et un capteur d'image. Ce capteur d'image est de préférence électronique (tel que le capteur matriciel CCD ou CMOS d'une caméra électronique) mais on peut également envisager qu'il s'agisse d'un simple film photographique qui sera exposé zone par zone au fur et à mesure du balayage de rayons X, les zones de film ne correspondant pas à la zone irradiée à un moment donné étant masquées à ce moment. L'écran à cristaux liquides est rendu opaque partout sauf dans une zone (en principe une ligne de matrice si le balayage permet une irradiation ligne par ligne) correspondant à l'image effectivement irradiée par le faisceau X. Le capteur d'image lumineuse, s'il est électronique, ne recueille pas de signal, sauf dans cette zone. Les rayons X qui ont pu être diffusés dans des directions éparpillées et qui ont pu produire une image lumineuse non limitée à la portion irradiée, ne vont pas influencer le capteur électronique car celui-ci n'observera qu'une zone correspondant véritablement à la portion irradiée.In the first, which is applicable when part of the chain converting x-rays into an electronic image goes through an image luminous, a liquid crystal screen is inserted between the luminous image and an image sensor. This image sensor is preferably electronic (such as the CCD or CMOS matrix sensor of an electronic camera) but we can also consider that it is a simple photographic film which will be exposed area by area as the X-ray is scanned, the film areas that do not correspond to the area irradiated at one time given being hidden at this time. The liquid crystal display is rendered opaque everywhere except in an area (in principle a matrix line if the scanning allows line-by-line irradiation) corresponding to the image actually irradiated by the X-ray. The light image sensor, if is electronic, does not collect a signal, except in this area. The X-rays which may have been scattered in scattered directions and which may have produce a bright image not limited to the irradiated portion, will not influence the electronic sensor because it will only observe one area corresponding to the irradiated portion.

Dans la deuxième grande variante de réalisation, applicable qu'il y ait conversion en image lumineuse avant que l'image ne soit recueillie par un capteur électronique d'image lumineuse ou qu'il y ait conversion directe des rayons X en image électronique, on prévoit que les moyens d'intégration électronique qui convertissent les photons d'image lumineuse ou les photons d'image X en électrons sont organisés pour empêcher l'intégration ou la lecture de charges en dehors de la zone d'image qui correspond à la zone irradiée à un instant donné par le faisceau X balayant.In the second major variant, applicable that there conversion to a bright image before the image is collected by a electronic light image sensor or direct conversion of X-rays in electronic image, it is expected that the means of integration electronics that convert bright image photons or photons of image X into electrons are organized to prevent integration or reading of charges outside the image area which corresponds to the area irradiated at a given time by the scanning X-ray.

Typiquement, si une ligne (ou éventuellement quelques lignes) de capteur d'image lumineuse ou électronique est irradiée à un instant donné, on s'arrange pour vider les charges de ces lignes juste avant que ne commence l'irradiation (vidant ainsi les charges issues des rayonnements diffusés indésirables), on intègre les charges résultant uniquement de l'irradiation de la zone irradiée, et on lit ces charges immédiatement après le temps d'irradiation.Typically, if a line (or possibly a few lines) of light or electronic image sensor is irradiated at a given time, we manage to empty the charges of these lines just before begins irradiation (thus emptying the charges from the radiation undesirable), we integrate the charges resulting solely from irradiation of the irradiated area, and these charges are read immediately after irradiation time.

On se réfère d'abord aux figures 6 et 7 qui illustrent l'invention.Reference is first made to Figures 6 and 7 which illustrate the invention.

Les moyens d'occultation partielle 24 sont réalisés par un obturateur 245 à cristaux liquides en réseau dont la transmission est asservie à la position de la portion irradiée 2' par le rayonnement X 1 balayant. Ces moyens d'occultation partielle 24 sont utilisés pour arrêter la lumière provenant de l'écran de sortie 206 du tube intensificateur d'image radiologique 21.The partial concealment means 24 are produced by a network shutter 245 with liquid crystal transmission subject to the position of the portion irradiated 2 'by X-ray radiation 1 sweeping. These partial concealment means 24 are used to stop the light from the output screen 206 of the image intensifier tube radiological 21.

Cet obturateur 245 peut comprendre une fine couche 31 de cristaux liquides (par exemple de type nématique en hélice) prise en sandwich entre deux lames transparentes 32, 33 scellées entre elles, elles mêmes placées entre deux polariseurs croisés 36.This shutter 245 may comprise a thin layer 31 of liquid crystals (for example of nematic type in helix) taken in sandwich between two transparent blades 32, 33 sealed together, they same placed between two crossed polarizers 36.

Un tel obturateur 245 fonctionne de la manière suivante. Au moins une des lames transparentes est pourvue d'un réseau d'électrodes. permettant d'appliquer un champ électrique à des portions de la couche de cristaux liquides. C'est pourquoi l'obturateur 245 est dit en réseau. En soumettant une partie de la couche de cristaux liquides à un champ électrique, elle devient opaque et arrête la lumière provenant de l'écran de sortie 206. Cette lumière ne peut plus atteindre le capteur d'image 22 lumineuse. En l'absence de champ électrique, cette partie est transparente et laisse passer la lumière provenant de l'écran de sortie 206. Cette lumière peut ainsi atteindre le capteur d'image 22 lumineuse.Such a shutter 245 operates in the following manner. At least one of the transparent blades is provided with an array of electrodes. for applying an electric field to portions of the liquid crystals. This is why the shutter 245 is said to be networked. In subjecting part of the liquid crystal layer to a field electric, it becomes opaque and stops the light coming from the screen of output 206. This light can no longer reach image sensor 22 light. In the absence of an electric field, this part is transparent and lets in the light coming from the output screen 206. This light can thus reach the light image sensor 22.

Dans l'exemple décrit et représenté en détails sur la figure 7, on a représenté sur chaque lame 32, 33 transparente un réseau 34, 35 d'électrodes E1, E2 transparentes parallèles orientées transversalement à la direction du balayage du rayonnement X 1. Une électrode E1 d'un réseau 34 est appariée à une électrode E2 de l'autre réseau 35 et deux électrodes appariées sont en vis à vis. Chaque réseau 34, 35 est relié à un dispositif de commande respectivement 37, 38 permettant d'appliquer à ses électrodes E1, E2 un potentiel approprié et donc de soumettre à un champ électrique approprié la portion de cristaux liquides située entre deux électrodes appariées afin de la rendre opaque. La commande des potentiels à appliquer aux électrodes réalisé en synchronisme avec le balayage, permet, à chaque instant, d'inclure dans l'obturateur 245 rendu opaque une zone transparente 246 dont les dimensions sont telles que le capteur d'image 22 lumineuse ne capte que l'image radiologique de la portion irradiée 2'. Les dimensions de la zone transparente 246 sont calquées sur celles de la portion irradiée 2' au coefficient de proportionnalité près.In the example described and shown in detail in FIG. 7, we have represented on each plate 32, 33 transparent a network 34, 35 of parallel transparent electrodes E1, E2 oriented transversely to the direction of X-ray scanning 1. An electrode E1 of a network 34 is paired with an electrode E2 of the other network 35 and two electrodes matched are opposite. Each network 34, 35 is connected to a device for command respectively 37, 38 making it possible to apply to its electrodes E1, E2 an appropriate potential and therefore subject to an electric field suitable for the portion of liquid crystal between two electrodes matched to make it opaque. The order of potentials to apply to the electrodes carried out in synchronism with the scanning, allows, at each instant, to include in the obturator 245 opaque a transparent zone 246 whose dimensions are such that the light image sensor 22 does not captures only the radiological image of the irradiated portion 2 '. The dimensions of the transparent zone 246 are modeled on those of the irradiated portion 2 'at proportionality coefficient.

Les motifs d'électrodes décrits sur la figure 7 ne sont que des exemples non limitatifs et d'autres sont bien sûr envisageables pour délimiter ce qui doit rester opaque et ce qui doit devenir transparent. Un motif classique matriciel peut être utilisé, pourvu que les moyens de commande, en principe ligne par ligne, soient organisés de manière à correspondre avec la nature du balayage X utilisée.The electrode patterns depicted in Figure 7 are only non-limiting examples and others are of course possible to delimit what should remain opaque and what should become transparent. A pattern conventional matrix can be used, provided that the control means, in principle line by line, are organized so as to correspond with the nature of the X scan used.

Un avantage non négligeable des moyens pour limiter l'acquisition du capteur d'image associés à un tube intensificateur d'image radiologique, dans la configuration où ils sont localisés entre l'écran de sortie et le capteur d'image est que ces moyens de limitation n'éliminent pas seulement la lumière provenant du rayonnement X diffusé dans le patient mais également la lumière diffusée et les rayons X diffusés sur tout le trajet compris entre eux et le patient. En leur absence, cette lumière ou ce rayonnement X seraient captés par le capteur d'image et le contraste serait dégradé. Les meilleurs gains en contraste sont obtenus en plaçant les moyens de limitation le plus près possible du capteur d'image lumineuse.A significant advantage of the means to limit the acquisition the image sensor associated with an X-ray image intensifier tube, in the configuration where they are located between the output screen and the sensor picture is that these limiting means don't just eliminate the light from the X-ray scattered in the patient but also scattered light and X-rays scattered along the entire path between them and the patient. In their absence, this light or this X-ray would be captured by the image sensor and the contrast would be degraded. The best gains in contrast are obtained by placing the most limiting means possible near the light image sensor.

Au lieu d'être externes au capteur d'image, les moyens de limitation de son acquisition peuvent lui être intégrés. Dans cette deuxième solution, c'est le capteur électronique d'image qui ne recueille qu'une zone d'image utile à un instant donné. Ces variantes sont illustrées aux figures 8a, 8b, 9a à 9c et 10 avec des capteurs d'images à l'état solide.Instead of being external to the image sensor, the means of limitation of its acquisition can be integrated. In this second solution is the electronic image sensor which collects only one area useful image at a given time. These variants are illustrated in FIGS. 8a, 8b, 9a to 9c and 10 with solid state image sensors.

On se réfère à la figure 8a. On retrouve comme sur la figure 1, le générateur 10 de rayons X à balayage qui délivre le rayonnement X 1 balayant la surface à imager 2 d'un patient 3 à examiner. De l'autre côté du patient 3 se trouve le système de détection 20 selon l'invention avec un capteur d'image lumineuse 22. Il comporte des moyens 21 pour convertir le rayonnement X issu des portions 2' en image lumineuse de type tube IIR associés au capteur d'image lumineuse 22. Maintenant le capteur d'image 22 lumineuse est un capteur électronique de type CMOS inclus par exemple dans une caméra vidéo 220. Les moyens 240 pour limiter l'acquisition du capteur d'image lumineuse sont intégrés au capteur d'image lumineuse. Ils peuvent soit empêcher l'acquisition d'image en dehors d'une zone déterminée (correspondant à la zone irradiée par le faisceau X) soit efectuer une remise à zéro de l'imagé acquise dans une zone déterminée (une ligne de capteur par exemple ou quelques lignes) juste avant de recueillir une image désirée dans cette zone, et là encore en synchronisme avec le balayage du faisceau X. We refer to Figure 8a. We find as in Figure 1, the scanning X-ray generator 10 which delivers the X-ray radiation 1 scanning the surface to be imaged 2 of a patient 3 to be examined. On the other side of the patient 3 is the detection system 20 according to the invention with a light image sensor 22. It includes means 21 for converting the X-ray from the 2 'portions in an IIR tube type light image associated with the light image sensor 22. Now the image sensor 22 luminous is a CMOS type electronic sensor included for example in a video camera 220. The means 240 for limiting the acquisition of the light image sensor are integrated into the light image sensor. They can either prevent image acquisition outside an area determined (corresponding to the area irradiated by the X-ray) either effect a reset of the image acquired in a specific area (a line sensor for example or a few lines) just before collecting a desired image in this area, and again in synchronism with the X-ray scanning.

Les capteurs de type CMOS de conception récente commencent à être utilisés. Ils sont très prometteurs car ils consomment beaucoup moins que les capteurs CCD, sont beaucoup moins encombrants, offrent de nouvelles possibilités dans l'acquisition de portions d'images, peuvent opérer à des vitesses supérieures à celles des capteurs CCD et sont de coûts moindres. Dans un tel capteur chaque pixel ne comporte pas seulement un élément photocapteur, par exemple une photodiode, mais aussi un circuit à transistor CMOS à fonction d'amplificateur de lecture permettant de pouvoir lire rapidement la quantité de charges stockée au niveau de chaque pixel qui a été exposé à un signal lumineux. Sur le même substrat se trouve aussi des moyens pour numériser les signaux stockés par les pixels et utilisés lors de la lecture.Newly developed CMOS type sensors are starting to be used. They are very promising because they consume much less that CCD sensors, are much less bulky, offer new possibilities in the acquisition of portions of images, can operate at higher speeds than CCD sensors and are costly lower. In such a sensor, each pixel does not only have one photosensor element, for example a photodiode, but also a circuit CMOS transistor with reading amplifier function allowing power quickly read the quantity of charges stored at the level of each pixel which was exposed to a light signal. On the same substrate there are also means for digitizing the signals stored by the pixels and used during reading.

Dans la configuration de la figure 8a et des figures 9a à 9c, le capteur d'image 22 lumineuse est formé d'une pluralité de points sensibles ou pixels P1 à P9 photosensibles arrangés en matrice et connectés entre un conducteur de colonne Y1 à Y3 et un conducteur de ligne X1 à X3. Ces pixels sont symbolisés par un carré. On en a représenté seulement neuf pour ne pas surcharger la figure. Après une exposition à un signal lumineux, les pixels P1 à P3 reliés à un même conducteur de ligne X1 sont adressés en même temps par un dispositif d'adressage 400 relié aux conducteurs de ligne X1 à X3, la quantité de lumière qu'ils ont reçue est lue au niveau de chaque pixel, les données lues pour chaque pixel étant transférées par les conducteurs de colonne Y1 à Y3 dans un dispositif de conversion analogique-numérique 401 fonctionnant en parallèle pour y être numérisées.In the configuration of FIG. 8a and of FIGS. 9a to 9c, the sensor 22 bright image is formed by a plurality of sensitive points or pixels P1 to P9 photosensitive arranged in a matrix and connected between a column conductor Y1 to Y3 and a row conductor X1 to X3. These pixels are symbolized by a square. We only represented nine for do not overload the figure. After exposure to a light signal, the pixels P1 to P3 connected to the same line conductor X1 are addressed in at the same time by an addressing device 400 connected to the conductors of line X1 to X3, the amount of light they received is read at each pixel, the data read for each pixel being transferred by the column conductors Y1 to Y3 in a conversion device analog-digital 401 operating in parallel to be digitized there.

Les moyens 240 limitant l'acquisition du capteur d'image 22, dans une première phase, juste avant qu'une portion 2' ne soit irradiée, commandent la remise à zéro c'est à dire l'effacement des pixels P4 à P6 du capteur correspondant à l'image lumineuse de ladite portion, et dans une seconde phase, juste après que la portion 2' ait été irradiée, commandent la lecture des pixels P4 à P6 correspondant à cette image lumineuse. Pour acquérir l'image lumineuse de la surface à imager 2 tous les pixels sont soumis à cette succession d'états effacement, exposition, lecture.The means 240 limiting the acquisition of the image sensor 22, in a first phase, just before a 2 'portion is irradiated, control the reset to zero, i.e. the erasure of pixels P4 to P6 of the sensor corresponding to the light image of said portion, and in a second phase, just after the 2 'portion has been irradiated, order the reading of the pixels P4 to P6 corresponding to this bright image. For acquire the bright image of the surface to be imaged 2 all the pixels are subject to this succession of states erasure, exposure, reading.

Les figures 9a à 9c servent à décrire le fonctionnement des moyens de limitation 240. On suppose que le balayage du rayonnement X 1 se fait linéairement comme sur la figure 1 et qu'une ligne de pixels correspond à une portion irradiée 2'. La flèche entrant dans le bloc 240 symbolisant les moyens de limitation indique que ces moyens sont synchronisés avec le mouvement de balayage du rayonnement X.Figures 9a to 9c are used to describe the operation of the means 240. It is assumed that the scanning of X-ray 1 is done linearly as in Figure 1 and that a line of pixels corresponds to a 2 'irradiated portion. The arrow entering block 240 symbolizing the limitation means indicates that these means are synchronized with the X-ray scanning movement.

Sur la figure 9a, le conducteur de ligne X2 auxquels sont reliés les pixels P4 à P6 porte une flèche issue du dispositif d'adressage 400, ce qui symbolise qu'ils viennent d'être effacés ou mis à zéro. Ils ont été vidés de toute trace d'exposition antérieure. Les pixels P1 à P3 sont eux exposés et sont représentés grisés tandis que les pixels P7 à P9 sont lus, ce qui est symbolisé par des flèches sur les conducteurs de colonne Y1 à Y3 issues des pixels P7 à P9 et dirigées vers le dispositif de conversion analogique-numérique 401.In FIG. 9a, the line conductor X2 to which the pixels P4 to P6 carries an arrow from the addressing device 400, which symbolizes that they have just been deleted or set to zero. They were emptied of any traces of previous exposure. Pixels P1 to P3 are exposed and are shown grayed out while pixels P7 to P9 are read, which is symbolized by arrows on the column conductors Y1 to Y3 from pixels P7 to P9 and directed to the analog-digital conversion device 401.

Sur la figure 9b, les pixels P4 à P6 sont grisés ce qui signifie qu'ils viennent d'être exposés à un éclairement délivré par le tube intensificateur d'image radiologique. Les pixels P1 à P3 sont lus, ce qui est symbolisé par des flèches sur les conducteurs de colonne Y1 à Y3 issues des pixels P1 à P3 et dirigées vers le dispositif de conversion analogique-numérique 401. Les pixels P7 à P9 sont effacés ce qui est symbolisé par la flèche, issue du dispositif d'adressage 400, et portée par le conducteur de ligne X3 auxquels sont reliés les pixels P7 à P9.In FIG. 9b, the pixels P4 to P6 are grayed out, which means that they have just been exposed to an illumination delivered by the intensifier tube radiological image. Pixels P1 to P3 are read, which is symbolized by arrows on the column conductors Y1 to Y3 from pixels P1 to P3 and directed to the analog-digital conversion device 401. The pixels P7 to P9 are erased which is symbolized by the arrow, from the addressing device 400, and carried by the line conductor X3 to which pixels P7 to P9 are connected.

Sur la figure 9c, on a voulu illustrer le fait que les pixels P4 à P6 sont lus à cet instant tandis que les pixels P1 à P3 sont effacés et que les pixels P7 à P9 sont exposés. Les mêmes symboles que précédemment ont été utilisés. De cette manière, les signaux lus ne comportent pas de diffusé.In FIG. 9c, we wanted to illustrate the fact that the pixels P4 to P6 are read at this time while the pixels P1 to P3 are erased and the pixels P7 to P9 are exposed. The same symbols as before have been used. In this way, the signals read do not include a broadcast.

Sur la figure 8b, on retrouve comme sur la figure 1, le générateur 10 de rayons X à balayage qui délivre le rayonnement X 1 balayant la surface à imager 2 d'un patient 3 à examiner. De l'autre côté du patient 3 se trouve le système de détection 20 selon l'invention. Il n'y a pas de tube IIR. Il comporte un capteur d'image 22, 52 à l'état solide qui peut être soit de type capteur d'image lumineuse 22, soit de type capteur d'image électronique 52. Ses dimensions sont sensiblement celles de la surface à imager 2. Le capteur coopère avec des moyens de conversion 21, 51 du rayonnement X issu des portions 2' soit en image lumineuse, soit en image électronique. S'il s'agit d'une conversion en image lumineuse, les moyens de conversion 21 sont de type scintillateur qui recouvrent le capteur d'image 22 lumineuse. S'il s'agit d'une conversion en image électronique, les moyens de conversion 51 sont réalisés à base de sélénium qui recouvre le capteur d'image 52 électronique. Les moyens de conversion 21, 51 sont directement face au rayonnement X qui a traversé le patient. Le capteur d'image 22 lumineuse peut être un capteur dont les pixels sont formés d'une diode photosensible coopérant avec un interrupteur. Ce type de capteur est bien connu en radiologie numérique. Le capteur d'image électronique 52 peut être conforme à ce que montre la figure 10. Les moyens 240 pour limiter l'acquisition du capteur d'image sont intégrés au capteur d'image 22, 52 et tout à fait comparables à ce qui a été décrit à la figure 8a Les éléments sensibles du capteur sont soumis à une succession d'états : effacement ou remise à zéro, exposition, lecture.In FIG. 8b, we find, as in FIG. 1, the generator 10 x-ray scanning which delivers x-ray 1 scanning the surface at image 2 of a patient 3 to be examined. On the other side of patient 3 is the detection system 20 according to the invention. There is no IIR tube. It comprises a solid state image sensor 22, 52 which can be either of the sensor type light image 22, or of the electronic image sensor type 52. Its dimensions are substantially those of the surface to be imaged 2. The sensor cooperates with means 21, 51 for converting X-ray radiation from 2 'portions either as a light image or as an electronic image. If it is about of a conversion into a bright image, the conversion means 21 are of scintillator type which cover the light image sensor 22. If it is about of a conversion into an electronic image, the conversion means 51 are made from selenium which covers the electronic image sensor 52. The conversion means 21, 51 are directly facing the X-ray who crossed the patient. The light image sensor 22 can be a sensor whose pixels are formed by a cooperating photosensitive diode with a switch. This type of sensor is well known in radiology digital. The electronic image sensor 52 can comply with what shows FIG. 10. The means 240 for limiting the acquisition of the sensor are integrated in the image sensor 22, 52 and quite comparable to what has been described in figure 8a The sensitive elements of the sensor are subject to a succession of states: erasure or reset, exposure, reading.

On se réfère à la figure 10, le capteur d'image électronique 52 est formé d'une pluralité de points 53 sensibles aux charges électroniques, formés chacun d'un élément capacitif 54 associé à un élément de commutation 55 par exemple un transistor TFT (pour la dénomination anglo-saxonne Thin Film Transistor) activé notamment lors de la lecture, arrangés en réseau à la manière des représentations des figures 9. Ces points sensibles sont réalisés notamment à l'aide de technique de dépôt en films minces de matériaux semi-conducteurs tels que le silicium amorphe. Ce capteur d'image électronique 52 coopère avec des moyens de conversion 51 image radiologique- image électronique à base de sélénium par exemple. Les points sensibles sont recouverts d'une couche 51 à base de sélénium. En traversant la couche 51 à base de sélénium le rayonnement X est directement converti en charges électroniques (symbolisées par une flèche). Ces charges électroniques sont stockées sur les éléments capacitifs 54. Les moyens pour limiter l'acquisition du capteur d'image électronique fonctionnent de manière comparable à ce qui a été décrit aux figures 8a et 8b. Les charges stockées sur les éléments capacitifs 54 sont lues séquentiellement ligne par ligne. En effectuant une opération de remise à zéro des éléments capacitifs 54 d'une ligne juste avant qu'ils ne reçoivent des charges électroniques et une opération de lecture des charges stockées dans ces éléments capacitifs juste après qu'ils aient reçu des charges, on parvient à éliminer le signal lié aux rayons X diffusés dans l'acquisition de l'image radiologique. Referring to FIG. 10, the electronic image sensor 52 is formed of a plurality of points 53 sensitive to electronic charges, each formed of a capacitive element 54 associated with an element of switching 55 for example a TFT transistor (for the Anglo-Saxon designation Thin Film Transistor) activated especially during playback, arranged in a network like the representations in Figures 9. These points sensitive are made in particular using film deposition technique thin semiconductor materials such as amorphous silicon. This electronic image sensor 52 cooperates with conversion means 51 radiological image - electronic image based on selenium for example. The sensitive points are covered with a layer 51 based on selenium. When crossing the selenium-based layer 51 the X-ray is directly converted into electronic charges (symbolized by an arrow). These electronic charges are stored on the capacitive elements 54. The means for limiting the acquisition of the electronic image sensor operate in a manner comparable to what has been described in FIGS. 8a and 8b. The charges stored on the capacitive elements 54 are read sequentially line by line. By performing a surrender operation zero of the capacitive elements 54 of a line just before they receive electronic charges and a read operation of stored charges in these capacitive elements right after they have received charges, we manages to eliminate the signal linked to the x-rays scattered in the acquisition of the radiological image.

Au lieu de remettre à zéro une ligne avant de la soumettre à une irradiation lumineuse ou une irradiation de rayons X, on pourrait envisager d'empêcher l'intégration des charges photogénérées en dehors d'une ligne déterminée et de ne l'autoriser que dans la ligne sélectionnée.Instead of resetting a line before subjecting it to a light irradiation or x-ray irradiation we might consider prevent the integration of photogenerated charges outside a line determined and to authorize it only in the selected line.

Enfin, il faut signaler que, notamment dans le domaine médical, on tend à remplacer les intensificateurs d'image radiologiques (tubes à vides) par des détecteurs à l'état solide, éventuellement de larges dimensions, et que l'on peut par conséquent adapter directement cette solution de limitation de l'observation à une zone déterminée en correspondance et en synchronisme avec une balayage de faisceau X.Finally, it should be noted that, particularly in the medical field, we tends to replace radiological image intensifiers (vacuum tubes) by solid state detectors, possibly of large dimensions, and that we can therefore directly adapt this limitation solution observation to a determined area in correspondence and in synchronism with an X-ray scan.

Les exemples décrits ne sont pas limitatifs en ce qui concerne les choix d'association entre le capteur d'image, les moyens de conversion et les moyens limitant l'acquisition du capteur d'image, d'autres combinaisons sont possibles sans sortir du cadre de l'invention.The examples described are not limiting as regards the choice of association between the image sensor, the conversion means and the means limiting the acquisition of the image sensor, other combinations are possible without departing from the scope of the invention.

Claims (12)

  1. Radiological image detection system capable of cooperating with a scanning X-ray generator (10) designed to produce X-ray radiation (1) scanning a surface (2) to be imaged, this X-ray radiation (1) irradiating, portion (2') after portion, the surface (2) to be imaged, the X-ray radiation from a portion (2') carrying a radiological image of the said portion, the system comprising an image sensor (22, 52) which is stationary with respect to the scanning and which is dimensioned so as to be able to acquire an image of the entire surface (2) to be imaged by the X-ray radiation from the portions (2'), characterized in that the detection system comprises in addition means for electronically limiting, at a given time, the acquisition of the image sensor (22, 52) to an area corresponding to the irradiated portion (2') at that time, these limitation means acting in synchronism with the scanning and in geometrical correspondence with the irradiated portion (2').
  2. Image detection system according to Claim 1, characterized in that the image sensor is a light image sensor (22) and in that it cooperates with means for converting the X-ray radiation from the portions (2') into a light image.
  3. Image detection system according to Claim 2, characterized in that the means (24) for limiting the acquisition are produced by a shutter (245) with a liquid crystals array, fixed with respect to the light image sensor (22) and inserted between the means for converting the X-ray radiation into a light image and the light image sensor.
  4. Image detection system according to either of Claims 1 and 2, characterized in that the means (240) for limiting the acquisition of the image sensor (22) are integrated with the image sensor.
  5. Image detection system according to Claim 4, in which the image sensor (22) is formed from a plurality of solid-state photosensitive pixels, characterized in that the means (240) for limiting the acquisition of the image sensor (22) control, just before a portion is irradiated, the erasure of the sensor pixels corresponding to the light image of the said irradiated portion, and the reading of the said pixels just after the said portion is irradiated.
  6. Image detection system according to Claim 4, in which the electronic image sensor is formed from a plurality of capacitive elements (54), characterized in that the means (240) for limiting the acquisition of the image sensor (52) control, just before a portion (2') is irradiated, the setting to zero of the capacitive elements (54) corresponding to the electronic image of the said irradiated portion and the reading of the charges stored in the said capacitive elements (54) just after the said portion (2') is irradiated.
  7. Detection system according to one of Claims 1 to 4, characterized in that the image sensor (22, 52) is of the solid-state type and especially of the CCD type or of the CMOS type, with photosensitive diodes or capacitive elements.
  8. Detection system according to Claim 2, characterized in that the means (21) for converting the X-ray radiation into a light image are of the X-ray image intensifier or scintillator type.
  9. Image detection system according to Claim 1, characterized in that the image sensor (52) is an electronic image sensor and in that it cooperates with means (51) for directly converting the X-ray radiation from the portions (2') into an electronic image.
  10. Detection system according to Claim 9, characterized in that the means (51) for converting the X-ray radiation into an electronic image are selenium-based.
  11. Detection system according to one of Claims 1 to 10, characterized in that it comprises means (23) for processing the image picked up by the image sensor (22) so as to reconstruct a complete image of the radiological image of the surface to be imaged from the images of the irradiated areas.
  12. Detection system according to one of Claims 1 to 3, characterized in that the light image sensor is of the photographic film or cinematographic film type.
EP00993753A 1999-12-30 2000-12-28 Radiological image sensing system for scanning x-ray generator Expired - Lifetime EP1250705B1 (en)

Applications Claiming Priority (3)

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FR9916778A FR2803394B1 (en) 1999-12-30 1999-12-30 X-RAY IMAGE DETECTION SYSTEM FOR SCANNING X-RAY GENERATOR
FR9916778 1999-12-30
PCT/FR2000/003723 WO2001050481A1 (en) 1999-12-30 2000-12-28 Radiological image sensing system for scanning x-ray generator

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DE60010521T2 (en) 2005-05-12
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WO2001050481A1 (en) 2001-07-12
FR2803394B1 (en) 2003-04-25
US7082187B2 (en) 2006-07-25
US20050201518A1 (en) 2005-09-15
US20020172327A1 (en) 2002-11-21
DE60010521D1 (en) 2004-06-09
EP1250705A1 (en) 2002-10-23

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