EP0349370A1 - X-ray image intensifier device provided with a circuit to compensate for magnetic distortion effects - Google Patents
X-ray image intensifier device provided with a circuit to compensate for magnetic distortion effects Download PDFInfo
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- EP0349370A1 EP0349370A1 EP89401676A EP89401676A EP0349370A1 EP 0349370 A1 EP0349370 A1 EP 0349370A1 EP 89401676 A EP89401676 A EP 89401676A EP 89401676 A EP89401676 A EP 89401676A EP 0349370 A1 EP0349370 A1 EP 0349370A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/003—Arrangements for eliminating unwanted electromagnetic effects, e.g. demagnetisation arrangements, shielding coils
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2229/00—Details of cathode ray tubes or electron beam tubes
- H01J2229/0007—Elimination of unwanted or stray electromagnetic effects
- H01J2229/003—Preventing or cancelling fields entering the enclosure
- H01J2229/0038—Active means
Definitions
- the present invention relates to an intensifier of radiological images, in particular of the type of those used in the medical field, either in direct radioscopy, or in radiology with digital processing of the signal representative of the image. It relates more particularly to a device for correcting the distortion brought to the image recorded with such devices.
- a radiological image intensifier is intended to receive low-power X-radiation and to transform this X-radiation into more powerful light radiation, more easily detectable by a display means, in particular by a camera.
- the reason for the weak X-ray received is to be sought in order to protect, in the medical field, patients subjected to examinations with such X-rays. In particular this occurs when these examinations are long, as is the case of treatments with digitization of image information, or as may be the case for a future generation of CT scanners where the detection member will precisely be such an intensifier of radiological images.
- An image intensifier essentially comprises a conversion slab for converting received X-ray radiation into light radiation capable of attacking a photocathode placed opposite this slab.
- the X-ray radiation-light radiation transformation is obtained in a known manner by providing the screen with cesium iodide crystals. Under the effect of illumination, photoelectrons are torn from the photocathode and move towards a screen. This movement towards the screen is subject to the effects of electronic optics. This optic tends to ensure that the impacts of the photoelectrons on the screen correspond to the location of the photocathode from which they were emitted.
- the screen is itself of a particular type: it re-emits a bright image representative of the electronic image transported by the electrons, itself representative of the X-ray image.
- This bright image can then be detected by a means any viewing device, in particular by a target of a conventional camera, so as to be viewed on a viewing device, in particular a device of the television monitor type.
- This bright image is written on one side facing the target while a target reading brush reads the written image on the other side.
- Such a display chain has an important drawback: the image revealed is an image geometrically distorted with respect to the X-ray image which is its origin. This distortion mainly occurs between the photocathode excited by the photons emanating from the conversion slab and the screen which receives the electronic radiation emitted by the photocathode. Indeed, during their transit, the photoelectrons are subjected to disturbing effects, in particular to magnetic effects due to the terrestrial magnetic field. If all the photoelectrons during this transit were affected by the same type of disturbance, it would suffice to correct at any point in the image chain the action of these disturbances so as not to be embarrassed.
- the image of a straight line interposed between an X-ray tube and such an image intensifier will be a straight line in the X-ray image which excites the slab, will be a line in the photonic image which attacks the photocathode, will be a line in the electronic image which leaves this photocathode, but will no longer be a line in the electronic image which comes to be displayed on the screen. Consequently, it can no longer be a straight line in the luminous image produced by this screen.
- the display device that is placed downstream then somehow reveals the result of the distortion due to the inhomogeneity of the earth's magnetic field in the space traversed by the electronic image.
- the correction of the distortion in these normal images shows its limits when the volume of information to be processed becomes large. Indeed, this distortion information is essentially linked to the position of the image intensifier tube in space at the moment when it receives, through an object to be radiographed, X-radiation to be measured.
- this distortion information is essentially linked to the position of the image intensifier tube in space at the moment when it receives, through an object to be radiographed, X-radiation to be measured.
- the multitude of possible positions of such an image intensifier tube makes it very cumbersome to store this correction information in memory.
- the application of the corrections calculated to normal images requiring the implementation of bilinear algorithms (with multiplications) is long to process if the number of correction bits is large.
- One of the solutions aimed at reducing the cumbersome execution of such calculations consists in limiting the corrective quantities to be taken into account.
- the object of the present invention is to remedy these drawbacks by proposing a simple solution which does not involve complex arrangements of correction coils, but which contributes to significantly reducing the number of processing bits to be managed.
- the invention starts from the following observation that the disturbing transverse components of the magnetic field have transverse effects in the image created. Rather than then seeking to counteract the disturbing magnetic effects of the field, in their writing distortion on the target of the camera, we are content to measure the existence of these disturbing components and take them into account to organize the reading of this camera target. In particular with the horizontal scanning and vertical scanning controls of the target read brush of this camera, one can take into account the offset at the origin as well as possibly modifications of dynamics of exploration of the target according to the measurements of these disturbing components.
- the subject of the invention is therefore a radiological image intensifier tube comprising - a conversion slab to convert X-ray radiation into electronic radiation, - a screen to convert electronic radiation into light radiation, - a camera fitted with a target to detect this light radiation, - and a circuit to compensate for the effects of distortion due to magnetic disturbances, characterized in that this circuit includes: a circuit for adjusting the reading mode of the target of the camera as a function of a measurement of the magnetic distortion.
- FIG. 1 single shows a radiological image intensifier tube provided with the device of the invention.
- an image intensifier tube 1 includes a conversion slab 2 for converting incident X-radiation 3 into electronic radiation 4.
- a screen 5 receives the electronic radiation 4 and transforms it into light radiation 6 detectable by a target 7 of a camera 8.
- a primary objective 9 makes it possible to send the image formed on the screen to infinity 5.
- the secondary objective 12 forms, from the image to infinity, a real image on the target 7 of an analyzer tube 10.
- a diaphragm 36 is interposed making it possible to adjust the light intensity arriving on the analyzer tube 10.
- the camera comprises a deflection block comprising a vertical deflection winding 17 and a horizontal deflection winding 16. These deflectors are used to scan the target of the analyzer tube by means of an electronic brush.
- the horizontal deflection circuit receives a horizontal scanning signal BH, and the vertical deflection circuit receives a vertical scanning signal BV.
- the tube 1 also comprises in a conventional manner a magnetic shielding 13 which envelops it, as well as a coil 14 for correcting the component oriented along the main axis 15 of the magnetic field near the input face of the tube 1, where the conversion slab 2 is located.
- the invention essentially comprises means to measure the transverse components of the disturbing magnetic field near the tube, as well as a circuit for correcting the deviation of the target read brush 7 as a function of these measurements.
- Other signals in particular of extinction of the scanning beam of the target during the scanning returns are also present. With their application circuit, they are not shown because they do not interfere with the invention.
- the corrections applied as a function of the horizontal and vertical disturbance measurements are taken into account in the form of offsets at the origin of the incremental horizontal and vertical scans respectively.
- operational amplifiers 18 and 19 mounted with resistors in adding circuits are respectively provided for adding horizontal shift signals H to the horizontal scan signals BH, and vertical shift signals V to the vertical scan signals BV.
- Obtaining the H and V signals representative of the offsets to be applied corresponding to the magnetic disturbances is advantageously carried out by probes of the HALL effect type like the probe 20.
- These probes are in the form of a parallelepiped and are traversed, between two opposite faces 21 and 22, by a bias current I supplied by a generator not shown.
- a bias current I supplied by a generator not shown.
- these probes develop a potential difference between the other faces of the parallelepiped perpendicular to this field. This potential difference is proportional to the amplitude of the component B measured.
- This difference potential is detected and, possibly after passing through a correction amplifier 23, is applied as a signal representative of the disturbance measured at the offset circuit comprising the operational amplifiers 18 and 19 respectively.
- a correction amplifier 23 In order to take account of the manufacturing dispersions of the probes such than 20, and also from the differences in the field value measured on either side of the conversion slab 2, it is preferable to pair the probes.
- the probe 22 is paired with a probe 24, the signal delivered by these two probes being combined in the amplifier 23.
- an axis change circuit 25 can be provided where, as indicated in dashes, the signal H is applied as correction of vertical scan offset, while signal V would be applied as horizontal scan correction.
- This circuit 25 can in particular be justified when for manufacturing reasons, it may be necessary to modify at the last moment the position of the image intensifier screen 1 relative to the camera 8.
- the circuit 25 may nevertheless have another advantage , that of allowing to take account of left corrections.
- H ′ aH + bV
- a′2 + b′2 1
- a circuit 26 making it possible to correct the offset at the origin as a function of the position in scanning of the target read brush.
- this circuit 26 shows that it is possible to obtain a dynamic correction (of order one or more) of the reading dynamics.
- the circuit 26 provides an offset at the variable origin as a function of time.
- This circuit 26 can in digital mode consist of a set of pre-programmed memory registers. Of course the circuit 26 includes an input 27 for resetting to zero in order to synchronize with the scanning signal considered.
- the HALL effect probes will be grouped in a cubic type assembly (six-sided cube: one probe on each side) so as to take into account by a compact device the three disturbing components of the magnetic field.
- the cubic device 28 will even be placed at the rear and on the axis 15 of the tube 1.
- a display monitor 29 makes it possible, once the corrections are made, to represent, correctly centered and respecting the real dimensions, images acquired during a radiology experiment. This visualized image or even stored in memory can be used for purposes of morphometry or reconstruction of computed tomography images.
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- Electromagnetism (AREA)
- Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
- Analysing Materials By The Use Of Radiation (AREA)
Abstract
Pour compenser les effets de distorsion magnétique, dans un tube (1) intensificateur d'images radiologiques on modifie (18-19) le mode de balayage de la cible (7) de la caméra (8) associée à ce tube. On provoque des décalages (H,V) du balayage ligne et du balayage vertical correspondant à des distorsions mesurées (20-24). De cette manière on restitue sur un écran de visualisation (29) une image utilisable en morphométrie.To compensate for the effects of magnetic distortion, in a radiological image intensifier tube (1) the scanning mode of the target (7) of the camera (8) associated with this tube is modified. Shifts (H, V) of the line scan and the vertical scan are caused, corresponding to measured distortions (20-24). In this way, an image usable in morphometry is restored on a display screen (29).
Description
La présente invention a pour objet un intensificateur d'images radiologiques, en particulier du type de ceux utilisés dans le domaine médical, soit en radioscopie directe, soit en radiologie avec traitement numérisé du signal représentatif de l'image. Elle concerne plus particulièrement un dispositif de correction de la distorsion apportée à l'image relevée avec de tels appareils.The present invention relates to an intensifier of radiological images, in particular of the type of those used in the medical field, either in direct radioscopy, or in radiology with digital processing of the signal representative of the image. It relates more particularly to a device for correcting the distortion brought to the image recorded with such devices.
Un intensificateur d'images radiologiques est destiné à recevoir un rayonnement X de faible puissance et à transformer ce rayonnement X en un rayonnement lumineux plus puissant, plus facilement détectable par un moyen de visualisation, en particulier par une caméra. La raison de la faiblesse du rayonnement X reçu est à rechercher dans le souci de protéger, dans le domaine médical, les patients soumis à des examens avec de tels rayonnements X. En particulier ceci se présente lorsque ces examens sont longs, comme c'est le cas des traitements avec numérisation des informations d'images, ou comme cela pourra être le cas pour une future génération de tomodensitomètres où l'organe de détection sera justement un tel intensificateur d'images radiologiques.A radiological image intensifier is intended to receive low-power X-radiation and to transform this X-radiation into more powerful light radiation, more easily detectable by a display means, in particular by a camera. The reason for the weak X-ray received is to be sought in order to protect, in the medical field, patients subjected to examinations with such X-rays. In particular this occurs when these examinations are long, as is the case of treatments with digitization of image information, or as may be the case for a future generation of CT scanners where the detection member will precisely be such an intensifier of radiological images.
Un intensificateur d'images comporte essentiellement une dalle de conversion pour convertir un rayonnement X reçu en un rayonnement lumineux susceptible d'attaquer une photocathode placée en vis à vis de cette dalle. La transformation rayonnement X-rayonnement lumineux est obtenue d'une manière connue en munissant la dalle de cristaux d'iodure de césium. Sous l'effet de l'illumination, des photoélectrons sont arrachés de la photocathode et se déplacent en direction d'un écran. Ce déplacement vers l'écran est soumis aux effets d'une optique électronique. Cette optique tend à ce que les impacts des photoélectrons sur l'écran correspondent au lieu de la photocathode d'où ils ont été émis. L'écran est lui-même d'un type particulier : il réémet une image lumineuse représentative de l'image électronique transportée par les électrons, elle même représentative de l'image de rayonnement X. Cette image lumineuse peut alors être détectée par un moyen de visualisation quelconque, en particulier par une cible d'une caméra classique, de manière à être visualisée sur un dispositif de visualisation, en particulier un dispositif de type moniteur de télévision. Cette image lumineuse s'écrit sur une face en regard de la cible tandis qu'un pinceau de lecture de la cible lit sur l'autre face l'image écrite.An image intensifier essentially comprises a conversion slab for converting received X-ray radiation into light radiation capable of attacking a photocathode placed opposite this slab. The X-ray radiation-light radiation transformation is obtained in a known manner by providing the screen with cesium iodide crystals. Under the effect of illumination, photoelectrons are torn from the photocathode and move towards a screen. This movement towards the screen is subject to the effects of electronic optics. This optic tends to ensure that the impacts of the photoelectrons on the screen correspond to the location of the photocathode from which they were emitted. The screen is itself of a particular type: it re-emits a bright image representative of the electronic image transported by the electrons, itself representative of the X-ray image. This bright image can then be detected by a means any viewing device, in particular by a target of a conventional camera, so as to be viewed on a viewing device, in particular a device of the television monitor type. This bright image is written on one side facing the target while a target reading brush reads the written image on the other side.
Une telle chaîne de visualisation présente un inconvénient important : l'image révélée est une image distordue géométriquement par rapport à l'image de rayons X qui en est l'origine. Cette distorsion se produit essentiellement entre la photocathode excitée par les photons émanant de la dalle de conversion et l'écran qui reçoit le rayonnement électronique émis par la photocathode. En effet, pendant leur transit, les photoélectrons sont soumis à des effets perturbateurs, notamment à des effets magnétiques dus au champ magnétique terrestre. Si tous les photoélectrons pendant ce transit étaient affectés par un même type de perturbation, il suffirait de corriger à un endroit quelconque de la chaîne d'image l'action de ces perturbations pour ne pas en être gêné. Malheureusement la sensibilité de ces photoélectrons est forte et l'inhomogénéité du champ magnétique sur leur lieu de passage est alors telle qu'il en résulte une distorsion dans l'image électronique projetée sur l'écran. Pour rendre plus concrets les effets d'une telle distorsion, on peut dire que l'image d'une droite interposée entre un tube à rayons X et un tel intensificateur d'images sera une droite dans l'image des rayons X qui excitent la dalle, sera une droite dans l'image photonique qui attaque la photocathode, sera une droite dans l'image électronique qui quitte cette photocathode, mais ne sera plus une droite dans l'image électronique qui vient s'afficher sur l'écran. Par conséquent, elle ne pourra plus être une droite dans l'image lumineuse produite par cet écran. Le dispositif de visualisation que l'on place en aval révèle alors en quelque sorte le résultat de la distorsion due à l'inhomogénéité du champ magnétique terrestre dans l'espace traversé par l'image électronique.Such a display chain has an important drawback: the image revealed is an image geometrically distorted with respect to the X-ray image which is its origin. This distortion mainly occurs between the photocathode excited by the photons emanating from the conversion slab and the screen which receives the electronic radiation emitted by the photocathode. Indeed, during their transit, the photoelectrons are subjected to disturbing effects, in particular to magnetic effects due to the terrestrial magnetic field. If all the photoelectrons during this transit were affected by the same type of disturbance, it would suffice to correct at any point in the image chain the action of these disturbances so as not to be embarrassed. Unfortunately the sensitivity of these photoelectrons is high and the inhomogeneity of the magnetic field on their place of passage is then such that it results in a distortion in the electronic image projected on the screen. To make the effects of such a distortion more concrete, it can be said that the image of a straight line interposed between an X-ray tube and such an image intensifier will be a straight line in the X-ray image which excites the slab, will be a line in the photonic image which attacks the photocathode, will be a line in the electronic image which leaves this photocathode, but will no longer be a line in the electronic image which comes to be displayed on the screen. Consequently, it can no longer be a straight line in the luminous image produced by this screen. The display device that is placed downstream then somehow reveals the result of the distortion due to the inhomogeneity of the earth's magnetic field in the space traversed by the electronic image.
Jusqu'à présent, ce type d'inconvénient avait pu être négligé du fait que les images que l'on cherchait à produire étaient essentiellement qualitatives et qu'on se préoccupait peu de leur contenu quantitatif : de la justesse des contours des objets révélés. Cependant, actuellement, avec le développement des techniques, on cherche de plus en plus à utiliser de telles images d'une manière quantitative. Par exemple, on peut vouloir réaliser des prothèses à partir des images obtenues et il est alors intolérable de disposer d'images faussées. Par ailleurs, dans le contrôle industriel, ce type de défaut entraîne l'impossibilité d'utiliser facilement de tels intensificateurs d'images en métrologie. De même, avec des futures tomodensitomêtres, cette altération empêchera une reconstruction correcte des images de coupes acquises simultanément.Until now, this type of drawback had been overlooked because the images we were trying to produce were essentially qualitative and that little attention was paid to their quantitative content: the accuracy of the contours of the objects revealed. However, at present, with the development of techniques, there is an increasing search to use such images in a quantitative manner. For example, we may want to make prostheses from the images obtained and it is therefore intolerable to have distorted images. Furthermore, in industrial control, this type of defect makes it impossible to easily use such image intensifiers in metrology. Similarly, with future CT scanners, this alteration will prevent correct reconstruction of the section images acquired simultaneously.
Il a été préconisé, pour remédier à ces inconvénients, diverses solutions tendant essentiellement à modifier le champ magnétique perturbateur. Dans une première famille de solutions on enveloppe le tube intensificateur d'images d'un blindage magnétique. Ce blindage canalise les lignes de champ magnétique et réduit les effets de la distorsion. Cependant, pour des questions d'absorption radiologique il n'est pas possible de placer un tel blindage au-dessus et à proximité de la face externe de la dalle de conversion. En conséquence à proximité de cette dalle les distorsions magnétiques continuent d'exister. Malheureusement, justement à proximité de cette dalle, les électrons arrachés à la photocathode sont encore à des vitesses très faibles. Ils sont par conséquent très sensibles à cet endroit à toutes les perturbations magnétiques.It has been recommended, to remedy these drawbacks, various solutions essentially tending to modify the disturbing magnetic field. In a first family of solutions, the image intensifier tube is enveloped with magnetic shielding. This shield channels the magnetic field lines and reduces the effects of distortion. However, for reasons of radiological absorption, it is not possible to place such a shield above and near the external face of the conversion slab. Consequently near this slab magnetic distortions continue to exist. Unfortunately, precisely near this slab, the electrons torn from the photocathode are still at very low speeds. They are therefore very sensitive there to all magnetic disturbances.
Il a par ailleurs été préconisé, dans un même esprit que celui qui avait conduit a utiliser des blindages, de placer à proximité de la dalle de conversion une bobine de correction du champ magnétique. Cette bobine est bobinée sur le pourtour de la dalle. Dans une demande de brevet français n° 88 04071 déposée le 29 mars 1988, il a même été proposé d'asservir le courant qui parcourerait cette bobine à une mesure de la composante du champ magnétique co-linéaire à l'axe principal du tube intensificateur d'images.It was moreover recommended, in the same spirit as that which had led to using shieldings, to place near the slab of conversion a coil of correction of the magnetic field. This coil is wound around the edge of the slab. In a French patent application n ° 88 04071 filed on March 29, 1988, it was even proposed to control the current flowing through this coil to a measurement of the component of the co-linear magnetic field to the main axis of the intensifier tube of images.
Il pourrait étre envisageable de généraliser cette dernière technique à la mesure des composantes transverses du champ magnétique perturbateur de manière à en compenser les effets. Cette solution n'est cependant pas envisageable car les bobines de correction ne produisent pas des champs magnétiques de correction indépendents les uns des autres. Ces bobines réagissent l'une sur l'autre de telle sorte que la correction globale devient rapidement inextricable. Cependant, la nécessité de prendre en compte les distorsions apportées par les composantes transverses du champ magnétique devient cruciale dans la mesure où on veut utiliser les tubes intensificateurs d'images à des fins de morphométrie. Il peut par ailleurs être envisageable d'acquérir une image typique, distordue par les perturbations, et d'en déduire des corrections à appliquer à des images normales, acquises dans des mêmes conditions que l'acquisition de l'image typique. La correction de la distorsion dans ces images normales, basée sur des algorithmes mathématiques mis en oeuvre par des programmes de traitement sur ordinateur montre ses limites quand le volume des informations à traiter devient important. En effet, ces informations de distorsion sont liées pour l'essentiel à la position du tube intensificateur d'images dans l'espace au moment où il reçoit, à travers un objet à radiographier, un rayonnement X à mesurer. D'une part la multitude des positions possibles d'un tel tube intensificateur d'images rend très encombrante la mise en mémoire de ces informations de correction. D'autre part l'application des corrections calculées aux images normales, nécessitant la mise en oeuvre des algorithmes bilinéaires (avec des multiplications) est longue à traiter si le nombre de bits de correction est important. Une des solutions visant à réduire la lourdeur d'exécution de tels calculs consiste à limiter les grandeurs correctrices à prendre en compte. En définitive on cherche à limiter le nombre de bits de calcul. Si on considère que la correction logicielle a pour résultat la correction fine de la distorsion de l'image, il est nécessaire d'obtenir une correction grossière de cette distorsion par d'autres moyens.It could be possible to generalize this latter technique to the measurement of the transverse components of the disturbing magnetic field so as to compensate for its effects. However, this solution cannot be envisaged since the correction coils do not produce magnetic correction fields independent of each other. These coils react one over the other so that the overall correction quickly becomes inextricable. However, the need to take into account the distortions provided by the transverse components of the magnetic field becomes crucial insofar as one wants to use image intensifier tubes for morphometric purposes. It may also be possible to acquire a typical image, distorted by the disturbances, and to deduce therefrom corrections to be applied to normal images, acquired under the same conditions as the acquisition of the typical image. The correction of the distortion in these normal images, based on mathematical algorithms implemented by computer processing programs shows its limits when the volume of information to be processed becomes large. Indeed, this distortion information is essentially linked to the position of the image intensifier tube in space at the moment when it receives, through an object to be radiographed, X-radiation to be measured. On the one hand, the multitude of possible positions of such an image intensifier tube makes it very cumbersome to store this correction information in memory. On the other hand, the application of the corrections calculated to normal images, requiring the implementation of bilinear algorithms (with multiplications) is long to process if the number of correction bits is large. One of the solutions aimed at reducing the cumbersome execution of such calculations consists in limiting the corrective quantities to be taken into account. Ultimately, we seek to limit the number of calculation bits. If we consider that the software correction results in the fine correction of the image distortion, it is necessary to obtain a correction gross of this distortion by other means.
La présente invention a pour objet de remédier à ces inconvénients en proposant une solution simple, ne faisant pas intervenir d'arrangements complexes de bobines de correction, mais contribuant à réduire d'une manière significative le nombre de bits de traitement à gérer. L'invention part de la constatation suivante que les composantes transversales perturbatrices du champ magnétique ont des effets transversaux dans l'image créée. Plutôt que de chercher alors à contrarier les effets magnétiques perturbateurs du champ, dans leur distorsion d'écriture sur la cible de la caméra, on se contente de mesurer l'existence de ces composantes perturbatrices et d'en tenir compte pour organiser la lecture de cette cible de la caméra. En particulier avec les commandes de balayage horizontal et de balayage vertical du pinceau de lecture de la cible de cette caméra, on peut tenir compte du décalage à l'origine ainsi qu'éventuellement des modifications de dynamique d'exploration de la cible en fonction des mesures de ces composantes perturbatrices.The object of the present invention is to remedy these drawbacks by proposing a simple solution which does not involve complex arrangements of correction coils, but which contributes to significantly reducing the number of processing bits to be managed. The invention starts from the following observation that the disturbing transverse components of the magnetic field have transverse effects in the image created. Rather than then seeking to counteract the disturbing magnetic effects of the field, in their writing distortion on the target of the camera, we are content to measure the existence of these disturbing components and take them into account to organize the reading of this camera target. In particular with the horizontal scanning and vertical scanning controls of the target read brush of this camera, one can take into account the offset at the origin as well as possibly modifications of dynamics of exploration of the target according to the measurements of these disturbing components.
L'invention a donc pour objet un tube intensificateur d'images radiologiques comportant
- une dalle de conversion pour convertir un rayonnement X en un rayonnement électronique,
- un écran pour convertir le rayonnement électronique en un rayonnement lumineux,
- une caméra munie d'une cible pour détecter ce rayonnement lumineux,
- et un circuit pour compenser les effets de distorsion dus aux perturbations magnétiques,
caractérisé en ce que ce circuit comporte :
- un circuit de réglage du mode de lecture de la cible de la caméra en fonction d'une mesure de la distorsion magnétique.The subject of the invention is therefore a radiological image intensifier tube comprising
- a conversion slab to convert X-ray radiation into electronic radiation,
- a screen to convert electronic radiation into light radiation,
- a camera fitted with a target to detect this light radiation,
- and a circuit to compensate for the effects of distortion due to magnetic disturbances,
characterized in that this circuit includes:
a circuit for adjusting the reading mode of the target of the camera as a function of a measurement of the magnetic distortion.
L'invention sera mieux comprise à la lecture de la description qui suit et à l'examen de la figure qui l'accompagne. Celles-ci ne sont données qu'à titre indicatif et nullement limitatif de l'invention.The invention will be better understood on reading the description which follows and on examining the accompanying figure. These are given for information only and in no way limit the invention.
La figure 1 unique montre un tube intensificateur d'images radiologiques muni du dispositif de l'invention. Dans cette figure un tube intensificateur d'images 1 comporte une dalle de conversion 2 pour convertir un rayonnement X incident 3 en un rayonnement électronique 4. Un écran 5 reçoit le rayonnement électronique 4 et le transforme en un rayonnement lumineux 6 détectable par une cible 7 d'une caméra 8. Un objectif primaire 9 permet de renvoyer à l'infini l'image formée sur l'écran 5. L'objectif secondaire 12 forme, à partir de l'image à l'infini, une image réelle sur la cible 7 d'un tube analyseur 10. Entre les deux objectifs 9 et 12, on interpose un diaphragme 36 permettant de régler l'intensité lumineuse arrivant sur le tube analyseur 10.FIG. 1 single shows a radiological image intensifier tube provided with the device of the invention. In this figure, an image intensifier tube 1 includes a conversion slab 2 for converting
La caméra comporte un bloc de déflexion comportant un enroulement de déflexion verticale 17 et un enroulement de déflexion horizontale 16. Ces déflecteurs servent à balayer la cible du tube analyseur au moyen d'un pinceau électronique. Le circuit de déflexion horizontale reçoit un signal BH de balayage horizontal, et le circuit de déflexion verticale reçoit un signal BV de balayage vertical. Le tube 1 comporte par ailleurs d'une manière classique un blindage magnétique 13 qui l'enveloppe, ainsi qu'une bobine 14 de correction de la composante orientée selon l'axe principal 15 du champ magnétique à proximité de la face d'entrée du tube 1, là où se trouve la dalle de conversion 2.The camera comprises a deflection block comprising a vertical deflection winding 17 and a horizontal deflection winding 16. These deflectors are used to scan the target of the analyzer tube by means of an electronic brush. The horizontal deflection circuit receives a horizontal scanning signal BH, and the vertical deflection circuit receives a vertical scanning signal BV. The tube 1 also comprises in a conventional manner a magnetic shielding 13 which envelops it, as well as a
L'invention comporte essentiellement des moyens pour mesurer les composantes transverses du champ magnétique perturbateur à proximité du tube, ainsi qu'un circuit de correction de la déviation du pinceau de lecture de la cible 7 en fonction de ces mesures. D'autres signaux, notamment d'extinction du faisceau de balayage de la cible pendant les retours de balayage sont aussi présents. Avec leur circuit d'application ils ne sont pas représentés car ils n'interfèrent pas dans l'invention. Dans une application préférée, les corrections appliquées en fonction des mesures des perturbations horizontales et verticales sont prises en compte sous la forme de décalages à l'origine des balayages respectivement horizontaux et verticaux incriminés. Dans ce but, des amplificateurs opérationnels 18 et 19 montés avec des résistances en circuits additionneurs sont respectivement prévus pour additionner des signaux H de décalage horizontal aux signaux BH de balayage horizontal, et des signaux V de décalage vertical aux signaux BV de balayage vertical.The invention essentially comprises means to measure the transverse components of the disturbing magnetic field near the tube, as well as a circuit for correcting the deviation of the target read brush 7 as a function of these measurements. Other signals, in particular of extinction of the scanning beam of the target during the scanning returns are also present. With their application circuit, they are not shown because they do not interfere with the invention. In a preferred application, the corrections applied as a function of the horizontal and vertical disturbance measurements are taken into account in the form of offsets at the origin of the incremental horizontal and vertical scans respectively. For this purpose,
L'obtention des signaux H et V représentatifs des décalages à appliquer correspondant aux perturbations magnétiques, est avantageusement réalisée par des sondes de type à effet HALL comme la sonde 20. Ces sondes se présentent sous une forme parallélépipédique et sont parcourues, entre deux faces opposées 21 et 22, par un courant I de polarisation fourni par un générateur non représenté. Soumises à une induction extérieure 
Plutôt que d'appliquer directement les signaux mesurés H et V dans les circuits de décalage, il peut être prévu un circuit 25 de changement d'axe où, tel que cela est indiqué en tirets, le signal H est appliqué à titre de correction de décalage du balayage vertical, tandis que le signal V serait appliqué à titre de correction du balayage horizontal. Ce circuit 25 peut notamment se justifier lorsque pour des raisons de fabrication, il peut être nécessaire de modifier au dernier moment la position de l'écran intensificateur d'images 1 par rapport à la caméra 8. Le circuit 25 peut néanmoins avoir un autre intérêt, celui de permettre de tenir compte de corrections gauches. Dans une réalisation plus complexe, les signaux H et V sont transformés en des signaux H′ et V′ tels que
H′ = aH + bV
V′ = a′H + b′V
avec a² + b² = 1
et a′² + b′² = 1
Ceci revient à faire un changement d'axe sur les corrections à attribuer et permet en définitive de tenir compte de toutes les situations : notamment des diverses positions que peut occuper la caméra par rapport au tube intensificateur d'images.Rather than directly applying the measured signals H and V in the offset circuits, an
H ′ = aH + bV
V ′ = a′H + b′V
with a² + b² = 1
and a′² + b′² = 1
This amounts to making a change in focus on the corrections to be allocated and ultimately allows all situations to be taken into account: in particular the various positions the camera can occupy relative to the image intensifier tube.
En outre, pour corriger la dynamique, il est possible d'introduire sur chacune des voies H et V un circuit 26 permettant de corriger le décalage à l'origine en fonction de la position en balayage du pinceau de lecture de la cible. Bien que dans une application préférée le circuit 26 sera omis, ce circuit 26 montre qu'il est possible d'obtenir une correction de dynamique (d'ordre un ou plus) de la dynamique de lecture. Le circuit 26 fournit un décalage à l'origine variable en fonction du temps. Ce circuit 26 peut en mode numérique être constitué d'un ensemble de registres mémoires préprogrammés. Bien entendu le circuit 26 comporte une entrée 27 de remise à zéro pour se synchroniser avec le signal de balayage considéré.In addition, to correct the dynamics, it is possible to introduce on each of the channels H and V a
Dans une application préférée et compte tenu des questions d'encombrement, les sondes à effet HALL seront groupées en un montage de type cubique (cube à six faces : une sonde sur chaque face) de manière à prendre en considération par un dispositif compact les trois composantes perturbatrices du champ magnétique. De manière préférée le dispositif cubique 28 sera même placé à l'arrière et sur l'axe 15 du tube 1.In a preferred application and taking into account the dimensions, the HALL effect probes will be grouped in a cubic type assembly (six-sided cube: one probe on each side) so as to take into account by a compact device the three disturbing components of the magnetic field. Preferably, the
Un moniteur de visualisation 29 permet une fois que les corrections sont effectuées de représenter, correctement centrées et en respectant les dimensions réelles, des images acquises pendant une expérience de radiologie. Cette image visualisée ou même mise en mémoire peut être utilisée à des fins de morphométrie ou de reconstruction d'images tomodensitométriques.A display monitor 29 makes it possible, once the corrections are made, to represent, correctly centered and respecting the real dimensions, images acquired during a radiology experiment. This visualized image or even stored in memory can be used for purposes of morphometry or reconstruction of computed tomography images.
Claims (9)
- une dalle (2) de conversion pour convertir un rayonnement X (3) en un rayonnement électronique (4),
- un écran (5) pour convertir le rayonnement électronique en un rayonnement lumineux (6),
- une caméra (8) munie d'une cible (7) pour détecter le rayonnement lumineux,
- et un circuit (18-19) pour compenser les effets de distorsion de l'image dus aux perturbations magnétiques, caractérisé en ce que ce circuit comporte
- un circuit (18-19) de réglage du mode de lecture (10) de la cible de la caméra en fonction d'une mesure (18-24) de la distorsion magnétique.1 - Tube (1) radiological image intensifier comprising
- a conversion slab (2) for converting X-ray radiation (3) into electronic radiation (4),
- a screen (5) for converting electronic radiation into light radiation (6),
- a camera (8) provided with a target (7) for detecting light radiation,
- And a circuit (18-19) to compensate for the effects of image distortion due to magnetic disturbances, characterized in that this circuit comprises
- a circuit (18-19) for adjusting the reading mode (10) of the camera target as a function of a measurement (18-24) of the magnetic distortion.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8808960 | 1988-07-01 | ||
| FR8808960A FR2633794A1 (en) | 1988-07-01 | 1988-07-01 | RADIOLOGICAL IMAGE INTENSIFIER TUBE WITH MAGNETIC DISTORTION EFFECTS COMPENSATION CIRCUIT |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP0349370A1 true EP0349370A1 (en) | 1990-01-03 |
Family
ID=9367998
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP89401676A Withdrawn EP0349370A1 (en) | 1988-07-01 | 1989-06-15 | X-ray image intensifier device provided with a circuit to compensate for magnetic distortion effects |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4945223A (en) |
| EP (1) | EP0349370A1 (en) |
| JP (1) | JP2766850B2 (en) |
| FR (1) | FR2633794A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111043113A (en) * | 2019-12-26 | 2020-04-21 | 深圳市联建光电有限公司 | Front adjusting device and LED display module capable of being adjusted in front |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2019881C1 (en) * | 1991-12-26 | 1994-09-15 | Физический институт им.П.Н.Лебедева РАН | Cathode-ray tube |
| RU2064206C1 (en) * | 1991-12-26 | 1996-07-20 | Физический институт им.П.Н.Лебедева РАН | Laser screen for cathode-ray tube and method for its manufacturing |
| US5339003A (en) * | 1992-06-22 | 1994-08-16 | Principia Optics, Inc. | Laser screen for a cathode-ray tube |
| JP4018165B2 (en) * | 1995-05-19 | 2007-12-05 | 株式会社東芝 | X-ray image tube device |
| DE19926098C2 (en) * | 1999-06-08 | 2003-05-15 | Siemens Ag | X-ray system |
| FR2823968B1 (en) * | 2001-04-27 | 2005-01-14 | Ge Med Sys Global Tech Co Llc | CALIBRATION METHOD OF IMAGING SYSTEM, MEMORY MEDIUM AND ASSOCIATED DEVICE |
| US7957582B2 (en) | 2007-06-21 | 2011-06-07 | General Electric Company | Method and system for correction of fluoroscope image distortion |
| US20090267703A1 (en) * | 2008-04-23 | 2009-10-29 | Andrzej May | Dynamically adaptable impedance matching circuitry between an electro-optical load and a driving source |
| DE102008045720A1 (en) * | 2008-09-04 | 2010-03-18 | Siemens Aktiengesellschaft | Method for correcting aberrations of an X-ray image intensifier system and associated X-ray image intensifier system |
| USD880453S1 (en) * | 2018-07-25 | 2020-04-07 | Dolby Laboratories Licensing Corporation | Speaker |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3809889A (en) * | 1972-12-29 | 1974-05-07 | Gen Electric | Image intensifier compensated for earth{40 s magnetic field |
| DE2809725A1 (en) * | 1978-03-07 | 1979-09-13 | Licentia Gmbh | CRT with coil measuring stray magnetic fields - and controlling current in compensating coil also around outside edge of screen |
| DE3419043A1 (en) * | 1984-05-22 | 1985-11-28 | Siemens AG, 1000 Berlin und 8000 München | Circuit arrangement for compensation of signal distortion at the edge of a television picture |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5827580Y2 (en) * | 1975-05-22 | 1983-06-15 | ソニー株式会社 | Raster - Hizumi Hoseisouchi |
| US4328418A (en) * | 1980-04-10 | 1982-05-04 | Picker Corporation | Magnetic field correction method and apparatus |
| US4456853A (en) * | 1981-07-06 | 1984-06-26 | Tektronix, Inc. | Feedback CRT for use in a closed-loop correction system |
-
1988
- 1988-07-01 FR FR8808960A patent/FR2633794A1/en not_active Withdrawn
-
1989
- 1989-06-15 EP EP89401676A patent/EP0349370A1/en not_active Withdrawn
- 1989-06-29 US US07/372,903 patent/US4945223A/en not_active Expired - Fee Related
- 1989-06-30 JP JP1169692A patent/JP2766850B2/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3809889A (en) * | 1972-12-29 | 1974-05-07 | Gen Electric | Image intensifier compensated for earth{40 s magnetic field |
| DE2809725A1 (en) * | 1978-03-07 | 1979-09-13 | Licentia Gmbh | CRT with coil measuring stray magnetic fields - and controlling current in compensating coil also around outside edge of screen |
| DE3419043A1 (en) * | 1984-05-22 | 1985-11-28 | Siemens AG, 1000 Berlin und 8000 München | Circuit arrangement for compensation of signal distortion at the edge of a television picture |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111043113A (en) * | 2019-12-26 | 2020-04-21 | 深圳市联建光电有限公司 | Front adjusting device and LED display module capable of being adjusted in front |
Also Published As
| Publication number | Publication date |
|---|---|
| US4945223A (en) | 1990-07-31 |
| JPH02210744A (en) | 1990-08-22 |
| JP2766850B2 (en) | 1998-06-18 |
| FR2633794A1 (en) | 1990-01-05 |
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