Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
  • A61B6/50—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications
  • A61B6/51—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications for dentistry
  • A61B6/512—Intraoral means
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B19/00—Programme-control systems
  • G05B19/02—Programme-control systems electric
  • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
  • G05B19/401—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by control arrangements for measuring, e.g. calibration and initialisation, measuring workpiece for machining purposes

Definitions

• a mobile imaging installation for example a dental digital radiology installation, comprises a source of radiation (for example x-rays), an image sensor 20, and a control unit 30.
• the sensor 20 may comprise a digital detector 21 of the CCD (Charge Coupled Device) type, associated with a scintillator 22.
• the detector 21 is sensitive to photons with a wavelength in the visible range.
• the scintillator 22 acts as a wavelength converter, receiving X-rays at the input and delivering photons of visible light at the output.
• the control unit 30 is coupled to the sensor 20 to control the operation of the installation.
• an object 40 is placed between the source 10 and the sensor 20.
• the object 40 comprises elements having a certain opacity with X-rays, such as a tooth 41 of a patient, and transparent or slightly opaque X-ray elements, such as the cheek 42 of the patient.
• the image obtained on the digital sensor 20 contains the image of the target, namely the tooth 41.
• the X-ray source 10 and the digital sensor 20 are not integral with each other.
• the sensor 20 is adapted to be placed in the mouth of the patient against the target tooth, and the user (generally the dentist or his assistant) must hold the source 10 in front of the sensitive surface of the sensor 20, and find the correct position of the source 10 relative to the sensor 20, wherein the target tooth is further located between the source and the sensor.
• angulator 50 comprises a support rod integral with the sensor 20, and along which a washer 51 is slidable.
• the sensor 20 is introduced into the patient's mouth on the opposite side to the inner face of the cheek of the patient and the washer 51 is brought against the outer face of the cheek of the patient.
• the user then brings the x-ray source 10 against the washer 51, which makes it possible to better position the X-ray source in front of the sensor, and also to better align the direction of the X-rays on the axis perpendicular to the sensitive surface. 20.
• an angulator is a long and tedious use.
• the fixing elements of the sensor on the angulator are visible on the X-ray, and it is not always possible to use them.
• a positioning defect detection device between a first element and a second element which comprises:
• the emission unit being adapted to be secured to the first element
• An electromagnetic wave reception unit and digital processing adapted to be secured to the second element, and cooperating with the electromagnetic wave transmission unit to detect a positioning defect of the first element relative to the second element.
• such a device can be adapted to an existing mobile radiology installation.
• the first element is then the radiation source, and the second element is the image sensor.
• the application of the device is however not limited to this example, the device can be used to help the positioning of all types of elements.
• electromagnetic waves are for example radio waves (produced by high frequency electric currents) of appropriate power.
• the frequency of electromagnetic waves may be less than 100 MHz, and more particularly in the band [10 kHz-100 MHz].
• the invention also proposes a mobile imaging installation, of the type comprising: a source of radiation; and,
• an image sensor having a surface sensitive to the radiation generated by the radiation source, and not integral with the radiation source.
• the installation further comprises a positioning defect detecting device according to the first aspect above, including:
• the electromagnetic wave emission unit is integral with the radiation source
• the unit for receiving electromagnetic waves and for digital processing is integral with the image sensor.
• the invention also proposes a mobile imaging installation of the above type, but in which the installation further comprises a positioning defect detection device according to the first aspect above, of which:
• the electromagnetic wave emission unit is integral with the image sensor;
• the unit for receiving electromagnetic waves and for digital processing is integral with the radiation source.
• the positioning defect may be indicated to the user in any appropriate manner.
• the user can then change the position of the source and / or the sensor.
• the positioning fault information may be used to automatically change the position of the radiation source, via a slave position control system.
• the invention thus offers an interesting alternative to the device called "angulator".
• the electromagnetic wave receiving unit is configured to further detect a angle between a plane of the electromagnetic wave emission unit and a plane of the wave receiving unit electromagnetic. This angle corresponds to the angular position error (also called parallax error) between the radiation source and the sensor.
• the electromagnetic wave receiving unit comprises a number M of electromagnetic receivers arranged in the same plane at respective non-symmetrical positions with respect to a first axis and / or a second axis in said plane, where M is an integer greater than or equal to 2.
• the electromagnetic wave receiving unit is furthermore configured to further determine by signal processing the signals from the different electromagnetic emitters for each of the M electromagnetic receivers, and deriving a rotation of said plane with respect to said first axis and / or said second axis, respectively.
• FIG. 1, already analyzed is a diagram illustrating the principle of digital dental radiology
• FIG. 2, also already analyzed is a diagram which illustrates a solution known in the prior art under the name of angulator, to solve the problem of relative positioning of the radiation source and the sensor in the context of digital radiology.
• dental is a diagram which illustrates a solution known in the prior art under the name of angulator, to solve the problem of relative positioning of the radiation source and the sensor in the context of digital radiology.
• Figure 3 and Figure 4 are diagrams illustrating an embodiment and the principle of operation of an installation object of the present invention
• FIG. 5 is a very simplified diagram illustrating the problem of the parallax defect between the radiation source and the sensor in the context of mobile X-ray digital imaging
• Figures 6a, 6b and 6c are diagrams illustrating embodiments of the electromagnetic wave emitting device
• Figures 7, 8a and 8b are diagrams of an embodiment of an electromagnetic receiving unit for automatically detecting the orientation of the image sensor in its own plane
• - Figure 9 is a diagram illustrating an embodiment of the installation allowing integration of the faster image sensor.
• mobile radiology installation means an installation in which the radiation source and / or the image sensor are not integral with each other.
• digital installation is meant an installation in which the image acquisition process is at least partly carried out by digital means.
• a digital radiology installation comprises a radiation source 10, such as an X-ray generator.
• the gun 12 of the generator is a cylinder whose function is to shape the generated X-ray beam so that it has the shape, for example, of a cone with a very small aperture, that is of substantially constant diameter, and equal to 60 mm for example.
• the main axis of the barrel 12 corresponds to the axis 11 of incidence of generated X-rays.
• the installation also comprises a digital image sensor 20. It may comprise a CCD 22 associated with a scintillator 21 (which, in operation, is arranged on the CCD side which is oriented towards the X-ray source).
• the CCD image sensor is for example of size 2, that is to say that its sensitive surface corresponds to a rectangle of diameter equal to 48 mm.
• the image sensor is coupled to a control and operating unit, which produces the radiological image itself.
• a control and operating unit which produces the radiological image itself.
• Other dimensions than those indicated above are of course conceivable, but these are typical of an application to digital dental radiology.
• the installation further comprises an electromagnetic wave emitting unit 13 which can be secured to the source 10, and a reception unit electromagnetic waves that can be made integral with the image sensor 20, cooperating with each other.
• electromagnetic wave emitting unit 13 which can be secured to the source 10
• reception unit electromagnetic waves that can be made integral with the image sensor 20, cooperating with each other.
• the device is adapted to indicate to the user any positioning error. This error can then be corrected by the practitioner, manually or via a robotic control device.
• the source for this purpose, the source
• the positioning error is provided at the input of a slave controller which automatically positions the X-ray source with respect to the image sensor.
• the positioning defect detection device comprises an electromagnetic wave emission unit which, in the operating situation, is made integral with the radiation source 10. This emission unit is controlled by a unit 15.
• the unit 15 comprises for example a microprocessor controlled by software.
• the transmitting unit also comprises a set of at least 3 controlled electromagnetic wave generators 120, such as solenoids.
• the solenoids are for example placed in the same plane, which is perpendicular to the incident axis 11 of the X-ray beam.
• they are arranged on a support 13 of toric shape, whose inner diameter is adapted so that it is fixed at the end of the gun of the generator 10.
• the plane of the support 13 corresponds to the plane of the end of the barrel 12 of the generator 10.
• the solenoids 120 are preferably distributed equidistantly (i.e., in equitably distributed angular positions) along the ring formed by the main plane of the support 13. This arrangement makes it possible to simplify the processing carried out on the reception side. In the figure, there are thus 3 solenoids angularly spaced two by two by an angle equal to 120 degrees.
• solenoids 120 each emit, with a certain recurrence, a directional magnetic field. For this purpose, they are excited by a control system managed by the control unit 15. More particularly, the unit 15 is responsible for modulating this field in a frame having a specific bit pattern of each of the transmission solenoids. This allows the receiving unit, by signal processing, to identify (i.e., determine and separate) the signals from the different transmit solenoids.
• the positioning defect detecting device comprises at least one receiving solenoid 230 which, in the operating situation, is secured to the image sensor 20.
• this solenoid is arranged on a plate 23 arranged behind the sensor, that is to say on the side opposite to the sensitive surface of the sensor, that is to say also on the side of the CCD 22 which is opposite the scintillator. 21, or on the side of the sensor 20 which, in operation, is opposed to the source 10.
• the electromagnetic wave receiving unit also comprises processing means, such as an operating unit 25.
• the unit For example, it comprises a microprocessor and is controlled by software. It can advantageously be confused with the control and operating unit of the digital image sensor 20, these elements being for example made in the form of a computer, for example a conventional personal computer.
• the receiving solenoid 230 captures the magnetic field from a transmitting solenoid.
• the signal thus captured is electronically conditioned and then digitized for analysis by signal processing, at the level of the unit 25.
• the intensity and the phase of the electromagnetic fields are a function of the distance and the angle at which they are measured, with respect to their emission point, that is to say at the location of the emission solenoids which generate.
• the electromagnetic waves that are generated are adapted to cross human tissues, of course in a manner that is not harmful to the physical integrity and health of the patient.
• Such electromagnetic waves are for example radio waves (produced by high frequency electric currents) of appropriate power.
• the frequency of the electromagnetic waves may be less than 100 MHz. In particular, this frequency can be in the band [10 kHz - 100 MHz].
• Such waves propagate well in the air, but less well in human tissues and even less well through dense parts such as teeth or bones.
• the received signal is generally quite low, of the order of a few microvolts ( ⁇ V) and is therefore quite difficult to treat.
• An operating principle that however gives good results under such unfavorable conditions is the use of the relative intensity of the fields between the transmission solenoids 120 to find the point where they balance. Considering that the characteristics of the emitters are identical, this point corresponds to the center of the plane of the support 13 of the emission solenoids.
• the receiving solenoid is preferably placed opposite the center of the sensitive surface of the image sensor 20. However, this provision is not mandatory, since it can very well be taken into account in the calculations leading to the detection. or not a positioning error, a known distance between the center of the sensitive surface of the image sensor 20 and the location of the receiving solenoid.
• An error distance from the equilibrium point of the electromagnetic fields generated by the emission solenoids can be determined from the relative intensity of the fields if the attenuation as a function of the distance is known, which can be the case either by the application of the propagation laws of the electromagnetic waves, or by a simple calibration of the system.
• a relatively accurate estimate of the position of the receiving solenoid relative to the plane formed by the transmitting solenoids can be obtained using a series of triangulation calculations. Since the measurement is carried out on relative amplitudes and phases, it is preferable that the signals emitted by each transmission solenoid have identical characteristics in terms of amplitude, frequency, phase, recurrence period, and electromagnetic field. created (especially polarization). Performance is improved with simplified calculations.
• solenoids 120 which are identical to one another are provided.
• the transmitting unit is adapted to establish a control sequence of the transmission solenoids on the basis of a "one-at-a-time" rule, for example "each in turn” , on which the unit of reception can synchronize.
• the emission solenoids emit all, but each alternately. This sequence is taken into account by the processor controlling the transmission unit.
• Embodiments provide a solution to the additional problem of detecting a parallax error.
• the knowledge of the shape of the electromagnetic fields also makes it possible to determine an incident angle between the electromagnetic emitters and the electromagnetic receiver (s). This angle corresponds to the parallelism error between ⁇ XG.YG ⁇ and ⁇ XC, YC ⁇ planes, respectively of the X-ray generator and the image sensor, which corresponds to the measurement of the parallax error between the first and second.
• the electromagnetic emission unit comprises at least four identical electromagnetic emitters 120.
• the control unit 25 The calculations making it possible to determine the incident angle between the electromagnetic emitters and the electromagnetic receiver (s) are here also carried out by the control unit 25. They implement rules of triangulation and trigonometry classic, and do not need to be explained here. Indeed, the skilled person is able to proceed with their implementation, for example in the form of appropriate software.
• the electromagnetic wave emission unit comprises in fact 8 identical emission solenoids or electromagnetic emitters. This number achieves the best compromise between the complexity of the calculations to be performed and the level of performance achieved.
• the N solenoids of the electromagnetic wave emission unit may comprise a center transmission solenoid corresponding to the center of the toric support 13.
• a center transmission solenoid corresponding to the center of the toric support 13.
• this central solenoid 130 has a diameter between the internal diameter and the outer diameter of the torus 13.
• the solenoid 130 thus has a larger diameter, a larger surface and a higher efficiency than the solenoids 120, which makes it possible to improve the measurements made for the other solenoids.
• the X-ray When the X-ray sensor is placed in the patient's mouth, the X-ray may include the teeth of the upper jaw or the lower jaw on the right or left side of the patient.
• the cable connecting the control and operating unit 25 to the image sensor 20 imposes a different angular position of the latter in each of these four cases. It follows that the meaning of the image obtained must be determined and noted on the image by the practitioner, for example by writing it on a self-adhesive tablet deposited on the radiological image obtained, or manually entered on a keyboard. computer to appear on the snapshot itself.
• embodiments allow to automatically determine the orientation of the sensor in the mouth, and to take into account during the production of the image, so that it is always identified and / or presented in a corresponding manner.
• the device already described above which allows the determination of the position of the sensor with respect to the plane of the transmitting solenoids, can in fact be further improved to further enable the detection of the orientation of the image sensor.
• the electromagnetic wave receiving unit comprises a single receiving solenoid, as in the case of the embodiment according to FIG. 4 (on which the angular position of the device is marked by a black dot in a corner of the plate 23 ), a rotation of 180 degrees, for example, gives the same position. This is because a single point corresponding to the center of the receiving solenoid 230 is taken into account in the triangulation calculations.
• Different angular positions of the receiving unit can be discriminated in its own plane, by providing at least two receiving solenoids, such as solenoids 231 and 232 of the embodiment according to FIG. 7. It is observed at each level. of them the electromagnetic signals from the electromagnetic emitters 120 of the electromagnetic emission unit.
• the solenoids 231 and 232 are offset from one another with respect to the axis or to the reference axes, which are here, for example, a vertical axis (-YC + YC) and a horizontal axis (-XC. + XC) of the ⁇ XC, YC ⁇ plane of the image sensor.
• At least one second electromagnetic wave receiver is added to the electromagnetic wave reception unit so as to allow, when the latter is secured to the image sensor 20, to determine the angle formed by the axis perpendicular to the sensitive surface of the image sensor and the axis of incidence of X-rays from the generator 10.
• These solenoids are located in the same plane (the plane of the plate 23), in respective positions not symmetrical with respect to a first axis and / or a second axis in said plane. The Determination of the position with respect to the transmit solenoids is then performed for each of the receive solenoids. The relative positions then give the angle of rotation of the plate in its own plane, which angle corresponds to the angle of rotation of the image sensor in its own plane.
• the rotation of the plate 23 implies a difference in distance between each of the receiving solenoids 231 and 232 on the one hand, and each of the transmission solenoids (not visible in these figures), on the other hand .
• the determination of the angular orientation of the image sensor allows the automatic rotation of the image displayed on the video monitor of the installation, by the application software executed by the computer 25.
• this also supposes that the orientation of the x-ray generator is known.
• the solenoids 231 and 232 are preferably arranged at a distance from each other which is the highest possible to make the discrimination of the different orientations easier. In the application which is concerned here, this discrimination is not very difficult to achieve because only four angular positions are to be discriminated (from 0 to 360 degrees, in steps of 90 degrees).
• An X-ray digital X-ray sensor typically comprises a CCD matrix coated with a chemical element (corresponding to the scintillator) transforming X-rays into photons.
• the detection of the presence of X-rays is carried out autonomously at image sensor level by exceeding a threshold by the amount of light received at the sensor.
• TRIG detection the X-ray presence information is available at the sensor, it is controlled in so-called "integration" mode in which it is maintained in static so that it can capture all the X-rays that continue to flow. until the end of the exhibition period.
• integration so-called "integration” mode in which it is maintained in static so that it can capture all the X-rays that continue to flow. until the end of the exhibition period.
• the average reaction time is of the order of 2 milliseconds, for an exposure time of between 15 and 250 milliseconds.
• embodiments of the invention provide that an X-ray radiation detection device is placed in front of the end of the barrel 12 of the X-ray generator.
• This X-ray detector can advantageously be mechanically interdependent. of the electromagnetic emission unit, for example mounted on the support 13 of the transmission solenoids 120 and 130.
• the control unit 15 has a simple signal conditioning electronics from the detector 14.
• X-ray presence information supplied by the detector 14 is then transmitted in a coded manner by the transmission solenoids 120 to the electromagnetic wave receiving unit, for example in the form of of a different modulation frequency.
• the control unit 25 of the reception unit can then control the integration of the image sensor 20.
• reaction time is reduced by a factor of 10 compared to a detection on the image sensor itself, because the signal is very strong at the output of the gun 12 which is close to the source of the X-rays, and because no obstacle does not attenuate or obscure the radiation.
• a reaction time of the order of 200 microseconds can thus be obtained. Decreasing the delay of the image sensor integration mode also allows a reduced exposure time for the same image quality.
• the digital detector CCD can be replaced by a phototransistor detector (photodiodes) in CMOS technology.
• the image sensor is not necessarily a digital sensor, but can also be an analog sensor, whose output information is scanned or not.
• the radiation source is not necessarily an X-ray generator, but it can also be a Gammas ray generator, or others.
• a button located on the processing unit 15 of the transmission unit can make it possible to put the emission unit under tension for a predetermined duration, which can be predefined;
• the reception unit can be integrated in the radiological image sensor or on a small plate contiguous thereto.
• the noise generated by an electromagnetic transmitter does not disturb the radiological image sensor
• the presence of the electromagnetic transmitter does not present any incompatibility of use with an intrusive element such as a dental radiological image sensor;
• the solenoid integrated in the radiological image sensor may be the electromagnetic transmitter, the solenoids integral with the generator becoming electromagnetic receivers.
• the basic principle remains strictly the same because the physical systems are always symmetrical and reversible.
• the mathematical treatments are simply permuted in principle. If these treatments are to be performed by the application software managing the X-ray image sensor (which is executed on the practitioner's general-purpose computer), the receiving unit operating at the X-ray generator must have a communication channel with this application software, wired (USB protocol, RS232, ...) or wireless (WIFI standards, Bluetooth, ...);
• the electromagnetic wave emission unit is adapted to transmit and the electromagnetic wave receiving unit is adapted to receive additional information in addition to the bit pattern.
• additional information may include radiation detection information of the radiation source, or other control, signaling, or other information.

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