DE3230894C2 - X-ray image reading system for electrostatic charge images - Google Patents

Abstract

X-ray image reading system with a camera (Fig. 1) generating a charge image on a roller belt (6), of which this charge image is generated line-by-line or line-parallel by rotating the belt (7, 8) past a reading head (9, Fig. 2) is read out and converted into digital output information with intermediate storage.

Description

- That an X-ray camera (1) with image recording is provided on the surface (16) of a roll tape (6),

- That a device (7, 8) is provided for driving the roller belt (6) for reading out,

- That the camera contains a line reading head (21), which is arranged so close to the roller belt (6) to be set in circulation that during one rotation of the roller tape (6), the pixels of a line are recorded by a charge scanning probe (25) can be, and

- That the reading head (61) is designed so that it with each revolution of the roller conveyor (6) one line each on the surface (16) of the roller conveyor (6) scanned the recorded charge image and timed the scanning of all times takes place one after the other

2. X-ray image reading system with electrical charge image recording the X-ray image taken of the object,

characterized by.

- that an X-ray camera (1) with image recording on the surface (16; a roller belt (6) is provided

- That a device (7, 8) is provided for driving the roller belt (6) for reading out,

- That the camera has a line reading head (21) which corresponds to one of the number of lines Number of individual modules (22) and the so close to the conveyor belt to be put into circulation (6) is arranged that already with one revolution of the roller conveyor (6) in the system all Image points of all lines of the surface (16) of the roller conveyor (6) are scanned and by the reading head (9) be included.

3. Reading system according to claim 1 or 2, characterized in that in the reading head (9, 21, 61) analog / digital conversion is provided.

4. Reading system according to one of claims 1 to 3, characterized in that for correcting inhomogeneities of the surface (16) of the roller belt (6) an additional program reference memory (134) is provided in which correction data can be stored are.

5. Camera for a reading system according to one of the claims 1 to 4, characterized in that it contains a device with which the roller belt (6) in the Temporarily suck the area of the image surface (16) onto a correspondingly shaped electrode plate (19) allows, so as to allow the required spherical shape of the roller belt (6) during the image recording reach.

6. Camera for a reading system according to one of claims I to 5, characterized in that dab in this Contain xenon as an X-ray absorbing gas under a pressure of more than 5 bar The present invention relates to an X-ray image reading system, as indicated in the preamble of claim 1

For decades, methods and devices have been developed with which X-ray images, e.g. B.

by the human body, recorded and / or reproduced in an ever more optimal way can be. It is important to have the highest possible spatial resolution as well as possible large dynamic range of the recorded X-ray image to reach. For this, the BUd-Aüinahmemsteria! be free of inhomogeneities and the period of time within which the image was recorded or available stands should be as small as possible. This is particularly important in all cases with medical x-rays ensure that the X-ray exposure of the subject is kept as low as possible

For the recording and / or reproduction of X-ray images, the film is still sensitive to X-rays Silver halite used. However, the image development time lasts at least a few minutes and only a small dynamic range of about 30 dB is achieved. For a long time The X-ray television image is also used for a period of time, but this also has a relatively low resolution has a relatively limited dynamic range. Various methods are known under the term "Electroradiography" are to be summarized. They also require a relatively long image development time for z. B. only 20 dB dynamic ranges. It is z. B. worked with a charge storage plate on the amorphous Selenium is applied as X-ray sensitive material by plate homogeneity it comes there but unfortunately more often to picture disturbances. Another embodiment in this regard is that of ionography the z. B. Xenon under a pressure of 10 bar as an X-ray receiver is used. After each X-ray exposure, however, a gas exchange is necessary. Development work is carried out with light radiation that by means of X-rays on a charge plate or on a phosphorescent plate to scan the generated X-ray image. As far as tested, it can be stated that the image development time is relatively long is needed. Image disturbances due to plate inhomogeneities can also hardly be avoided and with the The charge plate adds up the residual conductivity and the phosphorescent plate adds up Residual lights added as a disruptive factor.

It is an object of the invention to provide an X-ray imaging / reading system indicate that the image development time required is as short as possible and that it is as long as possible Dynamic range offers. In particular, this system should lead to images that are free from artifacts, such as those found in e.g. B. known to occur due to inhomogeneities in the transducer material.

This task is achieved with an X-ray image recording / reading system according to the preamble of the patent claim 1 solved, which is determined according to the invention by the features of the characterizing part of this claim.

3 4

Further refinements and developments of the Er- Each line reading module has a charge scanning

finding emerge from the subclaims. probe, on which the surface of the Roliband of the .Tt

The invention is based on various realizations that practically all of the image or uses various known, older single point information containing electrical charges measures and combines them into a new system 5 of the belt surface in the input amplifier the technical result is improved in accordance with the task. By pressing the column reading column against the To avoid artifacts, the distance can be kept small with a wall tape and there is a medium worked, the more or less compulsory with the read signal is insensitive to small is usually free of inhomogeneities, namely with a fluctuation in the distance.

Gas or a liquid medium, with the help of which io By parallel control of the line modules with a

according to the principle of ionography an implementation of clock lines and three command lines (input, readout,

X-ray intensity into an electrical characteristic reference value memory pixel limit number and

size is possible This electrical parameter is line address transfer mode) and with the help of a

conductivity generated by ionization, which, when present, B. 12 bit data transmission line can be the entire

gen of an electric field for a charging current 15 line reading and storage column as (the central)

can be used. fast data processing and storage system or-

That the results can be ganized by the applied ionography. This makes it possible to directly control an image-accessible charge image in a layer of a viewing device or a data carrier recording device or on an electrically insulating film and also to control data from the outside into the sperm. According to a feature of the invention, this is read in a 20 earlier. In summary >. The invention has an endless belt, a roller belt, which can be set in circulation over two rollers, if necessary with the appropriate stretching. The tape is the embodiment of the invention - including the following advantages: during the recording, it can be used immediately after the recording homo £; -; n are. In the case of the invention, however, no gas is needed, the result of which is that all image points of the charge image created on the exchange after each X-ray exposure, such as film or on the roller band, is the case with known ionography. The direct is completely scanned. Charge sensing provides the maximum possible charge

The charge image scan can be line by line or. dungssignaL Disruptive “shunt” capacities occur at a much higher speed, the lines do not appear and therefore the induced idle signal is parallel be performed. For the latter alternative voltage on the stylus or on the scanning probe a multiple reading head for electrical charge read-out is the maximum achievable value instead of direct reading is used (as in principle in natural charge scanning can also use a potential probe other design for data magnetic tapes Ver Array according to DE-OS 32 35 076 are used, finds application). The read-out head does not only contain the 35. Although the roller tape in the invention is only a single one Channel preamplifier, but is subject to more advantageous wear and tear, it is also still wise, there is also enough storage space for easy replacement. Leave with the invention preferably digital pixel storage. In particular, image readout times of less than 0.5 s can be achieved. the which is therewith also ensured that the with the scrolling image repetition frequency is practically only by the band achieved a high quality of the recording, subsequently 40 necessary exposure time for the X-ray radiation no loss of quality during processing suffers limited

In the case of a gas such as B. Xenon (under, for example, plugged-together line modules, which themselves-10 bar pressure), is for the ionization path, i.e. that active with the common electrical lines ver-thickness the layer effective for ionization on z. B. be bound, kept very low and something cm thick. In the case of a liquid as ionization, faulty time modules can be easily replaced, tion medium can this thickness because of the higher ab- Further explanations of the invention go from sorption can be reduced to less than 1 mm. With the BeGases given for the following, using the figures It is advisable to use the foil of the writing for greater thickness.

Roll band in the recording field of the spherical cap surface F i g. 1 shows a top view of an invented

to adapt mechanically, which serves as the picture surface for the system according to the invention.

Central projection of the x-ray image gives this figure. 2 shows a multiple line reading head.

can be realized in that on the one hand for the film F i g. 3 shows a block diagram of an inventive

of the roller band a material with a corresponding elastic system and

We use efficiency and the film by suction air (as in Fig. 4 shows a flow chart for the sequence of the

end of standstill or recording) against the use of a. system according to the invention.

Plate is drawn with the shape of this spherical cap. The F i g. 1 essentially gives a

A novel X-ray system to be used which is suitable for an embodiment.

sesäule consists z. B. from a stack of identical cameras 1 again. With 2 the X-ray radiation

Table modules that are mechanically and electrically simple, with 3 the object and with 4 the entry window

rather way to form such a column 60 called the camera. The illustrated camera 1 is

are. Each of these line modules preferably contains, preferably for operation with gas, e.g. xenon, under

Ie an input amplifier, an analog / digital a pressure of 10 bar determined This gas is located

converter and a memory for at least one line inside the gas-tight housing 5. The roll band

information and a line comparison information (for is denoted by 6, which runs over two rollers 7, 8

Calibration) with associated control circuit. In particular 65 and a roller drive, not shown, has 9 is

Integrated circuits are preferred for this. In the denotes a line readout head, which is used in the following for

Joule heat occurring in circuits can be explained in more detail separately. At 10 it's up

thin intermediate sheets made of copper are removed. a connection cable indicated that the reading head 9 with

an external electronics 11 connects. With 12 is an unloading device for the surface of the conveyor belt 6 designated

An electrical high voltage is generated between an electrode 13 in the interior of the housing 5 and an electrode 19 14 temporarily applied via a switch 15 to be actuated. In the illustrated embodiment the electrode 19 is electrically conductively connected to the housing and the space between the electrode 13 and the housing wall 4 is preferably filled with a gas which hardly absorbs the X-rays.

The housing wall 4, the electrode 13 and the electrode 19 are preferably designed in the form of a spherical cap in the image field area of the object 3 such that their spherical center lies in the focus of the X-ray beam 2. The electrode 19 is in electrically conductive contact with the conductive layer of the roller band 6. Preferably, during the applied high voltage (and standstill of the tape 6) of the frame part 16 sucked in the roller band 6 to the electrode 19 (with the aid of a device 20), whereby also the roller band in the image field area is given a spherical shape corresponding to the electrode 19.

The absorbed in the space between the electrode 13 and the rolling tape 6 resting on the electrode 19 X-ray quanta generate ions. These ions migrate under the influence of the applied electric field depending on the sign to the electrode 13 or to the roller band 6. They remain on the insulating side of the roller band adhere and thus create a charge image.

The roll band 6 has such a structure that the source 2 for the X-rays faces an insulator layer (of the roll band), whereas the back of the roll band 6 is an electrically conductive layer. A surface conductivity of approx. 10 ~ ⁷ A / V is sufficient for the conductive layer. So it doesn't necessarily have to be metallic.

F i g. 2 shows a line reading head already mentioned

21. It has a large number of individual modules 22 lying on top of one another, between which there are preferably copper sheets as heat dissipation. On the curved side 24, the individual modules 22 are lined up practically without any problems to each other. They each have a charge scanning probe, 25 of which are in the topmost individual module It is indicated by dashed lines. With 26, the rear side of the modules is designated. With 27, the connection contacts are of the individual (here the top module) modules

22, to which the data lines are connected, In this embodiment it is provided that an analog-digital conversion is already performed in the individual module 22 takes place and digital information is already being given by the module.

F i g. 3 shows a preferred exemplary embodiment for a circuit of each of the individual modules 22. With 31 is the one in single module! 22 included output terminal of the respective charge scanning probe 25 is denoted by 32 is a preamplifier and 33 is the one already mentioned Analog / digital converter denotes. The line memory 34 is connected to the converter 33, in which in the readout signals of all image points of the image line belonging to the respective individual module 22 are already in digital form get saved. With 35 a part of the line memory 34 is designated in which the line number is stored is 36 with a small processor is referred to, with which from the line memory 34 the charge image corresponding, usable electrical signal can be obtained at the output 37. 38 is the input for the control clock and 39 are inputs for lines for control commands.

An optionally provided reference value memory is indicated at 134 (dashed because of its optional significance shown). Corrections can be made with this reference value memory. Has z. B. the surface 16 of the roller conveyor 6, in which the electrical charge corresponding to the individual pixels recorded and temporarily saved

ίο is inhomogeneities that z. B. in artifacts in would express the reproduced image, compensation signal values can be stored in the reference value memory 134 for Corrective actions are indicated. Such inhomogeneities can be determined on a test image and apply the corrections afterwards to every picture taken in the company.

4 shows a flow chart for the operation of an erfir.dur.2E ^c 'ern ^a ' ^l '^{> r} ! Rnnttrpnhild-I.esesvstems. Reference 41 is made to the process step of recording.

During the recording, indicated by 42, the charge image is generated on the roller conveyor 6. At 43, for example, line-by-line reading is indicated. The control electronics 44 on the one hand the line module column 43 signals, but on the other hand receives the output signals of the line module column 43 and processes them z. B. in a digital-to-analog converter 45 into analog image information that can be reproduced by the display device 46. An analog video recording 47 can also be provided. With 48 possible digital recording of the obtained image information is indicated, the device part 48 also for (re) reading in information, eg. B. in the reference value memory 134. can serve. With 49 is indicated, for example, floppy disks with which the image can also be stored digitally. With 50 is indicated an Eia / output connection for further data communication with the reading system according to the invention.
It has already been pointed out above that instead of a line-by-line reading with a number of individual modules corresponding to the number of lines - with which all lines can then be scanned one after the other can be provided. The conveyor belt is read line by line by a single line reading head. When the conveyor belt revolves, all tie points of a single line are read out. The reading head is advanced in the direction perpendicular to the line and as the roller belt continues to rotate, all lines of the surface of the roller belt are scanned one after the other. The chronologically successive incoming signals are further processed in a device. This device can be designed in such a way that it also reproduces an analog image on the screen of this device for the viewer at its output

Between these extreme types of readout with only one reading head or with as many reading heads as there is Corresponding to the number of lines read out »z«, corresponding readout modems with »n« read heads can of course also be used and "z / n" tape rotations are implemented for image readout.

In addition, the structure of the image pickup device can be greatly simplified if the inside of the Housing wall 4 in FIG. 1 itself the function of the electrode 13 takes over The high voltage is then applied to the electrode plate 19, which is in electrical contact With the conductive layer of the roll tape 6, possible malfunctions of the sense amplifiers 23 are shown in FIG. 2

by the high potential of the conductive tape layer 16 can e.g. B. by lifting the reading heads 9 from the roller conveyor 6, while the high voltage on the electrode 19 is present, can be prevented. In this exemplary embodiment, the separate gas space falls between electrode 13 and housing wall 4 and the pressure compensation membrane 17 whole,; g.

For this purpose 2 sheets of drawings

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Claims (1)

Patent claims: 1. X-ray image reading system with electrical charge image recording of the X-ray image recorded of the object, characterized in that, 7. Camera for a reading system according to one of claims 1 to 5, characterized in that in this a liquid is contained as an X-ray absorbing medium