Method and device for digital calibration of an X-ray installation.

The invention relates to a digital calibration method for a radiology installation, especially for angiographic and angioplasty procedures and the installation for the implementation of this method.

Has already disclosed a radiology installation comprising a general table position at least substantially horizontally adjustable and lockable, on which can rest the body of a patient to be examined; a headband including isocentric, supporting at both ends of the means for emitting an X-ray beam (at the lower end below the table) and the receiving means of said beam (at the upper end the above the table and known by the skilled person under the name amplifier) ​​also adjustable and lockable; storage means, processing; viewing images associated with receiving means, including through digital analysis of the images produced, in particular through a computer. Support means of the table and the headband are adjustable and lockable through drive means and control means.

With such known apparatus, one can place a patient's body to be examined on the table and adjust the position of the table and / or the hoop to a certain relative position corresponding to some gauges and some angles of incidence and that, according to the needs imposed by the desired examination.

Several developments have recently been made to these facilities. First of all the images of the digitizing technique has facilitated the implementation of the installation with respect to the image processing. Then it was proposed to automate the movement of the table and the headband with a control computer (see FR 2588745).

Moreover recently, angioplasty procedures have developed the spot comprising first, under angiography, the existence of a stenosis in the patient and then introduce into the artery at the site of the stenosis a flask appropriate size with swelling, repeated several times if necessary, can increase the caliber of the artery.

The proper execution of these angioplasty procedures require fast and precise knowledge of internal diameters or sizes of the artery in a healthy serving and place of stenosis. Indeed, in particular, the size of the balloon to be used depends on its internal diameter.

Or, radiology facilities presently used commonly, only allow a relative appreciation of the dimensions but not their absolute knowledge in a direct reading of the image. And this knowledge dimension in absolute value is more important than the relative positions table-hoop are infinite.

The invention therefore primarily intended to allow direct assessment at any time and for any position on table-hoop, the exact dimensions in absolute value of what appears on the image.

The technical measure proposed for this main object is the prior calibration of the installation.

For this purpose, the invention first proposes a method of calibrating an X-ray installation, especially for angiographic procedures or angioplasty, X-ray installation comprising a general position at least substantially horizontal table , which may be based on the patient's body to be examined, movable and lockable; a headband including isocentric support at both ends of the means for emitting an X-ray beam and receiving means of said beam, displaceable and lockable; means for storing, processing, displaying images associated with the receiving means, in particular by digital analysis of the images produced through an image analysis computer; and a computer for receiving and controlling the positions of the table and of the transmission means and reception related to the image analysis computer; procedures angiography or angioplasty in which is placed a patient's body on the table is adjusted the relative positions of the table and transmission and reception means of X-rays (amplifier), is implemented the means for storing, processing, image display, characterized in that before an angiography procedure or angioplasty, in the absence of a patient on the table calibrating the installation so as to know its coefficients magnification and distortion and therefore the scale of the images obtained, and for this purpose: to the relative positions of the table and transmitting and receiving means:<ul><li>(I) is placed and the table of the transmitting and receiving means (amplifier) ​​in a first relative position;</li><li>(Ii) In this first relative position, is interposed on the X-ray beam, a calibrated grid and X-ray opaque, whose center is aligned with the center of the amplifier, at least substantially parallel to the plane of amplifier ; the center of the grid lying in the first relative position of the table and of the amplifier at equal distance between the table plane and the center of the amplifier;</li><li>(Iii) In this first relative position and in the presence of this grid, it implements the means of storage, processing, viewing, a short time to obtain an image of the grid;</li><li>(Iv) We compare the dimensions and surfaces of the calibrated grid and its image in order to know for the first relative position, the coefficients of expansion and distortion and scale of the image produced; </li><li>(V) then placed the table and the transmitting and receiving means (amplifier) ​​in a second different relative position of the first and not too far;</li><li>(Vi) In this second relative position is adjusted where appropriate by the position of the grid to adapt it if necessary-in particular is moved then the blocks by positioning and also it implements the storage means, processing , visualization, to know, to this second position, the coefficients of expansion and distortion and scale of the image produced;</li><li>(Vii) is transmitted to the computer the parameters characterizing in relative positions of the table, emission and reception means (amplifier) ​​and the corresponding values ​​of the expansion coefficient and distortion and scale.</li><li>(Viii) It interpolates the coefficients of expansion and distortion and the scale for any intermediate relative position between the first and second relative positions when necessary;</li><li>(Ix) repeating the preceding steps for other relative positions and the desired intermediate relative positions;</li><li>(X) is stored the coefficients of expansion and distortion scales and parameters characterizing the different relative positions and the interpolated values.</li></ul>

The invention then provides an X-ray installation, especially for angiographic procedures or angioplasty, comprising a general position at least substantially horizontal table, which may be based on the patient's body to be examined, driven support means of displaceable and lockable table, with table driving means with locking control means and the position of the table; a headband including isocentric, supporting at its two ends means for emission of an X-ray beam and means for receiving the said beam, carried by an arch support means displaceable and lockable by means of drive means shackle with locking and control means of the position of the arch; means for storing, processing, viewing images associated with receiving means, including numerical analysis, using a computer image analysis; and a computer associated with the control means of the position of the table and of the headband, characterized in that it also comprises first calibration means for knowing the expansion coefficient and distortion of the installation as well as the scale of the images obtained for the relative positions of the table and transmission and reception means; and secondly, an interface adapted to allow at any time on the one hand the transmission of the digital values ​​characterizing any relative position of the table and transmission and reception means (amplifier) ​​and, on the other hand the control of the movements of the table and transmission and reception means from instructions from the computer.

The invention will be well understood from the following description with reference to the accompanying drawings:<ul><li>- Figure 1 is a purely schematic perspective view of a radiological installation of the invention.</li><li>- Figure 2 is a diagram illustrating the calibration of the invention.</li><li>- Figure 3 is one of the possible patterns of interface.</li></ul>

The invention relates to a radiology installation comprising (1) a table 1 generally at least substantially horizontal position, which may rest on a patient's body to be examined, scope table support means 2 adjustable and lockable through table driving means with locking control means and the position of the table; a hoop 3, in particular isocentric, supporting at both ends of the transmission means 4 to an X-ray beam and receiving means 5 (amplifier) ​​of said beam, carried by support means 6 shackle movable and lockable through arch driving means with locking control means and the position of the arch; means 7 for storage, processing, viewing images associated with receiving means, including numerical analysis, using a computer image analysis 8; and a 9 associated with computer means for controlling the position of the table and of the hoop and which can be connected to the computer 8.

Such a facility as it has just been described is well known in the art and therefore requires no additional detailed explanations. This is especially true for the support means for driving and controlling the table and the arch which are not in themselves the object of the invention. The transmission means 4 are generally located at the lower end of the hoop 3 and under the table 1, while the receiving means 5 (amplifier) ​​are usually located at the upper end of the arch and above table 1 and, in operation of the plant placed directly in contact with the patient resting on the table 1 and that in the desired area. Table 1, and the roll bar 3 and the transmission means 4 and receiver 5 can be moved according to various movements combined sliding and / or rotation so as to adjust the position of the X-ray beam relative to the table 1, not only with respect to the two axes (length and width) thereof-especially for movement along the body of the patient-but also in impact.

Also known manner, the receiving means 5 (amplifier) ​​are generally placed in operation close to the patient's body, as already indicated.

The computer 8 capable of digital image analysis and the computer 9 for controlling the table 1 and the arch 3 are the same or different but are connectable functionally and / or structurally to each other. They naturally contain the control means, the CPU, peripherals, etc ..., appropriate and are loaded with or suitable programs.

The means 7 are shown in Figure 1 as comprising one or more screen (s) display. Of course, they may have other means of temporary or permanent visualization and storage means of the images obtained.

Thereafter designates by "relative position" of table 1 and of the hoop 3, a certain position defined in the table 1 and the transmission means 4 and 5 of reception (amplifier), characterized by situations compared the two axes of the table 1, the angles of incidence of the X-ray beam relative to the plane P of the upper table 1 (reference plane) and the spacings in the vertical direction means 4, 5 with respect to the table 1.

It is understood that these relative positions are unlimited and for each there is a certain value of the degree of magnification and distortion and a certain scale.

ladder means in the context of the present invention, the distance between two points on the image screen means 7 compared to the actual distance between the two points of origin image. For example the diameter of the image of an artery relative to the effective diameter of the artery itself.

According to the calibration method according to the invention of the X-ray installation thus defined before angiography or angioplasty procedure and in the absence of a patient on the table 1 calibrating the installation to know its expansion coefficient and distortion and therefore the scale of the images obtained, and, for this purpose: to the relative positions of the table 1 and means for transmitting and receiving 4, 5: <ul><li>(I) is placed the table 1 and the means of transmission and reception 4, 5, in a first relative position;</li><li>(Ii) In this first relative position, is interposed on the X-ray beam, a calibrated grid 10 and radiopaque, whose center is aligned with the center of the amplifier, at least substantially parallel to the plane of the amplifier ; the center of the grid lying in the first relative position of the table and of the amplifier at equal distance between the table plane and the center of the amplifier;</li><li>(Iii) In this first relative position and in the presence of this gate 10, implements the transmission means and reception 4, 5 and the means 7 for storage, processing, viewing, a short time to obtain an image of the grid 10;</li><li>(Iv) We compare the dimensions and surfaces of the calibrated grid 10 and its image in order to know for the first relative position, the coefficients of expansion and distortion and scale of the image produced;</li><li>(V) Table 1 is then placed and means of transmitting and receiving 4, 5 in a different second position relative to the first and not too far;</li><li>(Vi) In this second relative position, adjusting the position of the grid 10 to accommodate and also it implements the means of transmission and reception 4, 5 and the means 7 for storage, processing, viewing, for know, for this second position, the coefficients of expansion and distortion and wide image and made it according to the procedure already described;</li><li>(Vii) is transmitted to the computer the parameters characterizing in relative positions of the table, emission and reception means (amplifier) ​​and the corresponding values ​​of the expansion coefficient and distortion and scale.</li><li>(Viii) It interpolates the coefficients of expansion and distortion and the scale for any intermediate relative position between the first and second relative positions when necessary;</li><li>(Ix) repeating the preceding steps for other relative positions and the desired intermediate relative positions;</li><li>(X) is stored the coefficients of expansion and distortion, scales and parameters characterizing the different relative positions and the interpolated values.</li></ul>

The relative positions in which are made the measurements are taken either randomly or match conventional investigative positions, or result from an increment of parameters defining a position.

The difference between two relative positions in which a measurement is made is within the scope of those skilled in the art according to particular calculation means used for interpolation, the desired accuracy for the calculations of values ​​by interpolation, the importance of changes sought coefficients and scales relative to the variation of the parameters defining the positions.

To insert the grid 10, as provided in step (ii), is placed in the center of the grid 10 and the center of the amplifier 5, two balls opaque to X-rays (in lead) , 11 and 12 respectively, so that they are aligned and superimposed, the grid 10 being carried by a suspension 13 in particular, driven by the amplifier 5. in this way the grid 10 is parallel to the plane of the amplifier 5, permanently . In addition, (see Figure 2B especially) the distances between the center of the grid and one hand in terms of amplifier 5 on the other hand the plane P in table 1 are equal.

An installation according to the invention is therefore characterized in that it also comprises calibration means for knowing the expansion coefficient and distortion of the installation and the scale of the images obtained for the relative positions of the table and transmitting and receiving means.

Preferably, the invention implements a computer 9 adapted to perform the required interpolations and the storage of the coefficients and scales for each position. This computer 9 is separate or not the 8 processing images and / or controlling the relative movements but it is associated.

It should be noted that the described calibration can be performed originally before the first implementation of the installation and then verified at regular time intervals to ensure the consistency of the values ​​obtained or, if appropriate, correct (especially if changes or replacement of the camera and / or lens).

The invention also provides that during the subsequent use of the installation, after calibration, the values ​​of coefficients and scales are displayed on the screen means 7, during operation and that for any particular relative position of the table 1 and 3 of the hoop and means 4, 5. This display can be instantaneous through calibration performed previously, and through the interface between the radiological installation and the computer 9.

In the case of angioplasty, the practitioner can then, thanks to the invention, have an immediate and precise knowledge of the actual size of a stenosis as well as healthy portions of the artery including the stenosis. It can therefore use the appropriate ball, error-free without the need for trial and error without delay.

Naturally the invention implies that at any time the relative position table 1 arch-3 is known, which is made possible by the computer 8 which is able, at any time on the one hand to know the relative position table 1/3 hoop /. means 4/5 /; and secondly controlling the relative displacements. Generally, there is provided a hand display means parameters defining a relative position, in particular on the means 7 of the screen, and, on the other hand, the desired value input means for parameters defining a position on such as a keyboard, or a mouse or a voice control induction system or otherwise. A suitable software of the computer used to control the proper movements of the table 1 and the arch 3 according to an initial relative position and the relative position thus defined.

Where appropriate, there is also provided means for storing the parameters of a particular relative position, particularly repetitive.

According to a possible variant of implementation of the invention, the parameters defining a relative position table 1-hoop 3 are the following (Figure 3): - Table Height 1 (X) - Table 1 Position anterior posterior (Y) - Position 1 side table (Z) - Height receiving means 5 (H) - Average Rotation reception 5 (β) - Angulation means receiving 5 (γ) - Champ (C)

Each of these parameters as well as others, may vary between any of the end terminals. The settings for a dimension or angle varies continuously. The field generally varies discretely, which can take several values ​​(eg three).

The parameter values ​​correspond to adjustable levels of analog potentiometers POT drive means of the table 1 and the arch 3.

A suitable circuit allows the transmission to the computer used for the calibration of parameter values ​​corresponding to the relative position table 1 3-arch.

This circuit can be object of numerous variants. For example if one refers expressly to the fig 3 it may include an amplifier stage AMP for normalizing the voltage values ​​of analog potentiometers already mentioned; a transmission circuit comprising the mixing of signals MIX, a sampler / switch S / N, an analog / digital A / D, leading to the bottom of the computer 9 which includes a database DATA BASE for associating with specific parameter values ​​of a relative position-that is to say to a relative position déterminée- the expansion coefficient values ​​and distortion and the scale of the image. These coefficient values ​​and the scale are achieved and described by interpolation from some values ​​tested.

According to another aspect, the invention is well suited for real-time angioplasty procedure. Although initially, when taking a photograph, after injection of the contrast medium, the operator stores the image and the parameters defining the relative position of the radiological installation, and continues its review by repeating this procedure a number of time. At the end of the examination, the operator recalls images to select those corresponding to the best effect for performing angioplasty. With the calibration method according to the invention, it can qualitatively measure the diameter of the artery in its healthy portions and steosées, by direct analysis of the image. Finally, the relative proportions being stored together with the image, it can automatically reposition the installation in the position corresponding to the image acquisition position.

According to another characteristic, the installation is well suited for a procedure artérographie lower limb wherein is carried out an injection into the artery followed by a change of the relative position elemental itself followed by an injection and another modification of the relative position and so on. In this case, it is possible, also, to provide a control computer injections (including quantitatively) in association with the control of the relative positions of computer.

According to another feature, the software for the change of relative positions according to the instructions given by the operator comprises a safety of limiting the amplitude of the displacements according to the terminals corresponding to the morphology of the body of a patient on the table 1, to thereby avoid interference between the patient's body and the receiving means 5. in addition, pressure sensors are provided on the receiving means 5 in such a way that when stressed -which indicates interference between the reception means 5 and a fixed part: table 1 or patient-body movements are stopped.