DE2822241A1 - SCANNING X-RAY EXAM ARRANGEMENT - Google Patents

Description

PHN.884 5 DEEN / AYDV

"Scanning X-ray examination arrangement"

The invention relates to an arrangement for

Determination of absorption differences present in places in a body with the aid of a scanning X-ray beam and an X-ray detector.

Such an arrangement is known from DE-PS 693374. In the described therein The arrangement works with a beam that covers the entire body to be examined in one plane. By mutual rotation of the fan-shaped beam and a plane of the body to be examined is irradiated from several directions. the end the measurement data determined in the process, also in the following

8 0 98 50/069 4

FHN. 881 5 12/12/77

Called absorption values, which are a measure of the Absorption in a part of the body penetrated by the beam, "an image is put together in which the spatial absorption in the irradiated plane is shown. In the described arrangement there are some when reconstructing an image from the absorption values Problems that have prevented this arrangement from being used more widely. In particular, the spatial is enough Resolving power of the 'arrangement for example medical diagnostic applications.

Furthermore, the radiation dose is for the patient relatively large when using such an arrangement.

In more recent arrangements of this type it has been seeks to overcome these drawbacks by using an elemental X-ray beam, i. of an X-ray whose transverse dimension is directly a Large for the resolving power of the arrangement measured transversely to the beam direction. An example of one Arrangement is described in Dutch patent application 6912869. With this arrangement, a Gain in resolution and significant time savings through the use of modern digital Computing devices reached. In their place, however, is a relatively long examination time with a still relatively high radiation dose entered.

809850/0694

PHN.8815, 12/12/77

In DE-OS 2442809 is an arrangement
described in the "now" again using a fan-shaped X-ray beam through which
Using an adapted detection and digital signal processing the measurement speed is significantly increased. A disadvantage of this arrangement, however, is the high radiation dose and the relatively expensive and complicated detector arrangement, in which the conversion of the simultaneously arriving into sequential ones to be read

Measurement signals a relatively extensive electronic Circuit requires.

Another disadvantage of the previously known arrangements is that they are quick and easy. very precisely defined mechanical displacement of the X-ray carrier and the detector around the object to be examined is necessary. In the first and the last of the arrangements mentioned, this movement is to be investigated
Cross section on a rotation of the radiator and
of the detector is limited to the object to be examined.

In the second of the mentioned arrangements is included
a translatory movement of the emitter and the detector over the width dimension of the object to be examined is also necessary. In this case, on the other hand, the detection arrangement can be relatively simple and can be read simultaneously.

809850/0694

-tf- PHN. 8815 12/12/77

The invention is based on the object of creating an X-ray examination arrangement in which from at least some of the disadvantages mentioned have been eliminated as required. There is also an X-ray examination arrangement of the type mentioned, characterized in that the X-ray tracer with a Anode target with a large detection area at least in one direction and with electron deflection means to move an electron impact ~ area over the anode target to create a X-ray scanning the body to be examined is equipped.

As in an X-ray examination arrangement according to the invention the deflection means for the electron beam a scanning movement of the X-ray beam "5

can be supplied with a significantly less mechanical movement mechanism in the assembly get along. Thus, at least during the examination, per cross-section with a stepped shift of the Radiator between successive electrical Scanning movements are made.

In a preferred embodiment a simple detector is used, i.e. a detector which only has a single local absorption value records. This means that the detector does not need to be exhausted

8098 50/0694

-ZT-. PIIN. 8815

12/12/77 O

a multitude of identical and similarly working channels and can therefore be more sensitive and be executed more reliably. By including a collimator between the emitter and the to J examining body, which collimator, depending on the position of the scanning beam, only lets through that part which is directed at the detector, a substantial reduction in radiation dose can be achieved. Using a good quality detector can reduce the

ΙΟ further reduce the required radiation energy. The application of the principle of the constant output signal according to DT-OS 25 55 675, which is here through Electron beam control is easy to carry out, means both a further dose saving for the Patients as well as a significant improvement in the image.

In a preferred embodiment, the collimator is designed in such a way that the effective X-ray beam each Scanning always runs along mutually parallel lines and the detector is accordingly elongated executed. If necessary, you can use a simple detector that is not sensitive to the location, or a Use a location-sensitive detector or a detector sequence. When using a non-sensitive Detector is the location information from the deflection position of the electron beam in the

809850/0694

PHN.8815 i 2.12.77

X-ray tube derived. A receiving tube, which is to be scanned in the form of a cell, with an impingement plate that is sensitive to the X-rays can also be used as a detector.
In a further preferred embodiment, the X-ray tube is equipped with a two-dimensionally extended target plate and the detector is equipped with a two-dimensionally extended input screen, preferably in the form of an X-ray-sensitive pick-up tube that is to be scanned here in the form of a grid. By synchronizing the deflection means of the X-ray tube with those of the detecting tube, a location for the measured values can be determined in a simple manner.

In a further preferred embodiment the arrangement contains several, preferably arranged on a circular path around an object to be examined X-ray tracers each with an elongated anode target and a detector is assigned to each emitter. Here, for example, half a circumference can be replaced by a Anode target and the other half of the circumference be occupied by a detector entrance area. Both can also fill an entire circular path. For the last embodiment, a cathode ray tube in the form of a funnel can be used in which the electron beam between a double run

809850/0694

- * f- PH.f.8815

12.12.77 ttir

Wall of the radiator and that of the electron beam generated X-ray is directed to the axis of the funnel shape.

Some preferred embodiments according to the invention are shown below with reference to the drawing explained in more detail. It shows

Pig. 1 is an extremely schematic diagram of an X-ray examination arrangement with one according to the invention writing x-ray,

2 and 3 very schematically X-ray tracers for such an arrangement,

Fig. H shows a preferred embodiment

according to the invention with several, here two, X-ray era and associated X-ray detectors, Fig. 5 shows a preferred embodiment with a two-dimensional extended anode and adapted detectors,

6 shows an arrangement according to the invention in the form of a funnel-shaped X-ray emitter. According to an X-ray examination arrangement Fig.1 contains an X-ray tracer 1, a collimator and a detector 5. The X-ray tracer 1 is as Cathode ray tube with an electron beam generation system 7 for generating an electron beam 9 with Beam deflection in 11 and with an impingement anode I3 for

809850/0694

PHN. 8815 12/12/77

run the electron beam. The electron beam 9 here scans the impingement anode 13 in a cell-like manner under the influence of the deflection coils 11. In the impingement anode, the electrons accelerated by up to> 150 kV, for example, generate X-ray radiation which at least partially leaves the impingement anode on an outside of the tube. For this X-ray beam, the collimator comprising, for example, 30Ö channels in the scanning direction a narrow beam write ~ \ h, which is directed to a body under examination or an object I5 on the detector 5 selected here. As a result of the scanning movement of the electron impact area, the x-ray beam 14 carries out a scanning movement over the body 15 within an angle formed by two outermost rays 16.

The detector can be read on-line. At the end of a scanning phase, the X-ray tracer is combined with the detector with the aid of a drive 17 is rotated along a holder 19 by an angle, and it is opened a subsequent sampling phase is recorded in a corresponding manner. After a preferably stepped rotation Over a total angle of 180, for example, in 60 steps, there are sufficient measurement data for reconstruction an absorption image of the irradiated plane has been emitted.

8Ό9850 / 0694

ΡΗΚ ^Τ .8315 12/12/77

For adapting the radiation geometry to the size of the object to be examined can the emitter together with the detector in the direction of the connecting line 18 between the emitter j and the detector with the aid of a drive 21 longitudinally a holder 23 can also be moved, by the way With the scanning amplitude, a radiation geometry adapted to the size of the object is very simple be realized.

The measurement signals from the detector 5 are fed to an amplifier converter 25 in which the Signals can be amplified, corrected and transformed as required. The output signals of the amplifier- Converter 25 are fed to a computer 27 in which the local distribution of the absorption of the body to be examined is calculated from the collected signals The absorption values determined in this way can be stored in a recording unit 29 and for a desired cross-section through the object

^ O are displayed on a monitor 31. Arrangements with this type of signal processing is now generally known and does not require any detailed information here Description. For controlling and synchronizing the displacement of the X-ray tube and the detection a control arrangement 33 is provided, the one

809850/0694

-JL0-. PHN. 8815

12/12/77

-73

Zext adjustment between the arrival of the measurement signals and the position of the X-ray source in relation to the object to be examined. This tax arrangement is also with a control feed arrangement for the deflection coils 11 of the X-ray tube for synchronization the detection coupled with the electron beam scanning.

In the illustrated embodiment the detector 5 is mechanically coupled to the X-ray tracer so that they are always related to each other move onto the object to be measured. The collimator is also mechanically coupled to the X-ray beam *. This ensures that the writing x-ray beam 14 is always directed onto the detector.

The detector itself is designed here as a single-channel detector. For example, for correction measurements and the like, however, the detector can contain several measuring channels, for example a central channel for measuring the actual signal, i.e. the absorption value, and in the plane of the drawing next to it or perpendicular to the plane of the drawing offset one or more secondary channels for the measurement of signals with which the absorption channel can be corrected or the dynamics of the detector can be expanded. The next can Detector for the simultaneous measurement of two or more measurement signals for simultaneous irradiation several. Cross-sections in the object to be examined

809850/0694

-JJT- PHN. 881 5

12/12/77

be executed. Such an essentially single-channel detector can, compared to a detector, which contains a sequence of e.g. 300 elements, with a comparatively low atif wall and a high one Sensitivity and reliability are used. Also is compared to a compound Detector makes the necessary electronics simpler and therefore more reliable. For detection can be found here For example, a detector of simple design according to the description in the German patent application P 28 11 328.8 of the applicant can be used.

In this preferred embodiment, the X-ray tube the shape of a flat cathode ray tube connected to a Electron gun with, for example, a indirectly heated subsequent cathode for the Generation of an electron beam is equipped with a relatively high current density. Are more fit

the electron beam generating systems and beam deflection means analogous to the known designs, for example for television display tubes or for oscilloscope tubes. Compared to a television display tube, the X-ray tube used here has flat dimensions in a direction perpendicular to the plane of the drawing, for example 1 to 5 ^cm * ^ ^{11 of} the plane of the drawing, the dimension near the target is 30 cm, for example.

809850/0 694

~ 9έ-- PHN. 3815

12/12/77

-75

The X-ray tube is on the target side with an anode target, for example with a depth of 5 cm and a width of 50 cm in shape one with the hollow side facing outward circular arc j completed. The anode target contains a target made of gold or tungsten, for example with a thickness of, for example, approximately 25Ο / um and a window plate made of a material such as aluminum that only slightly absorbs the X-rays, Beryllium or titanium. The thickness of the target is chosen so that seen in the thickness direction a relatively large part of the X-ray radiation is generated in the side facing the window plate. Some of the electrons pass the target but they are intercepted by the window panel.

A considerable part of the X-rays directed towards the window plate pass through the Window plate out. A write beam can then be selected from this beam with the collimator.

In a preferred embodiment of a · indungsgemässen X-ray source erf of FIG. 2 is a at a Auftreffsexte kl an impingement k used "} out kicking X-ray 45th This causes the tube need in a lying behind the impingement wall part kf no conditions for radiation

809850 / 069A

PIIN. 8815 12/12/77

Transmission to be set. In the embodiment shown, the target, which can also consist of tungsten or gold here, is attached to a copper or silver anode carrier kS. The anode support is provided on the side facing away from the impact plate with a cooling structure 51 according to the description in GB-PS 1 ^ 29066, a cooling liquid can be pumped along the anode support via a supply line 53 and a discharge line 55. A shielding plate 57 can optionally be resiliently mounted relatively close to the elevations 59 of the cooling structure, which ensures good cooling. The tube is provided with an exit window 60, which here also consists, for example, of aluminum, beryllium or titanium and opposite or on which a collimator can be mounted. The difference in the path length for the electron beam between positions 61 and 63 can be compensated for by dynamic focusing of the electron beam, which is known per se. In this way, optimal focusing of the electron beam can be achieved over the entire anode target. The difference in the path length for the X-ray beam of positions 61 and 63 to the window or possibly to a detector can be compensated for by an adapted mounting of the tube in relation to the detector. If such a

809850/069 4

ΡΙίΝ.8815 12/12/77

If there are assembly problems, a difference in intensity can occur due to this difference in distance in the X-ray beam at the location of the detector through the use of an adapted current modulation of the Electron beam are balanced.

Of a further preferred embodiment of an X-ray emitter according to the invention, a part comprising the impact plate is shown in FIG. 3. Each anode target 71 of the X-ray tube contains an target electrode 73 made of gold or tungsten, a cooling body 75, preferably made of silver, which is preferably also provided with a cooling structure 77 and can be cooled with a cooling liquid via a supply line 79 and a discharge line 81. An electron beam 83 impinging on the impingement electrode 73 is sketched here with a single line, but the beam can have an elongated cross section 85 on the impingement plate, for example, which in practical cases approximates, for example, an elliptical shape, for which an electron gun according to the description in deT US- PS 388II36 can be used. In the impact area 85, the electrons extinguish an X-ray beam 87, at least a portion of which exits through an exit window 89.

The window 89 is for optimal transmission for the

809850/0 69 4

PIIN. 8815 12/12/77

to be generated X-rays composed of a light material. For example, for 50 kV X-rays with a beryllium window with a thickness of 250 ... 500 / um can be worked. With an adapted collimator, for example, too

Adapted to the elongated shape of the electron impact area, a write beam can be selected from the X-ray beam 87 in the manner already described. In a preferred embodiment, the collimator forms a unit with the exit window of the X-ray source. This means that the window, which is now firmly supported, can be made much thinner. Incidentally, the collimator can be mounted both on the outside and on the inside of the window. In the latter case, the collimator is thus added \ _k) in the tube.

The preferred ones described so far

Embodiments imben in common that an anode on target is scanned in the form of cells and that an X-ray beam may be selected for examination using a collimator, which means that measurements can be taken on-line. There is already mentioned the possibility of each sampling phase with each other parallel writing beams to work. A preferred one

Embodiment of a device operating in this way Untersuchungsanordiiung is shown in Fig. K.

809850/0694

-> 6- PIL · :. 8815

12/12/77

The arrangement shown is provided with two X-ray emitters 91, both of which are different from the one already described Art and are equipped with a parallel collimator 93. Opposite every X-ray tracer there is a ; Detector 95 arranged, which is also here as required

may be readable in a location-sensitive manner. After each sampling phase, the unit consisting of emitters and detectors is rotated here. In this arrangement, the two beams can be arranged in such a way that they measure a cross-section together and therefore reduce the number of mechanical displacements per cross-section to half or by a factor of 3 or 4 when using 3 or k emitters and detectors instead of 2 can be. The emitters with assigned detectors can, however, also be offset from one another in a direction perpendicular to the zoom plane in such a way that each emitter-detector combination measures a different cross section. As already mentioned, the X-ray tracers according to this description can also be equipped for the simultaneous measurement of several, for example 3 or 5, cross-sections to which the detectors are then adapted. If, for example, 3 emitters and detectors are used, 9 to 15 cross-sections can be measured at the same time. For different investigations one can manage with such a number of cross-sections that there are no axial shifts for inclusion in the system

809850 / 069A

ΡΗλ ^τ . 8815 12/12/77

need to be carried out. An additional advantage is that the mutual location of the different cross-sections is determined very precisely.

In another preferred embodiment according to the invention according to the sketched illustration in FIG 5, the X-ray tracer 100 is provided with a two-dimensionally expanded anode target plate 102. As a result, the X-ray tracer has taken on the shape of a television tube. An exit screen 104, which is formed, for example, by the anode target is, here is a rectangle with a rib, the length of which corresponds to a dimension of an object to be examined is adapted. For medical purposes, for example, it can be 25 cm especially for head and organ examinations and for example 50 cm for the examination of a whole Be body. The X-ray tube is equipped with an electron gun 106 and with a Beam deflection unit 108 is provided with which the entire target plate is scanned according to any desired pattern can be. Cellular scanning can be thought of here, for example, with the scanning lines have a mutual distance of, for example, 0.2 to 2.0 cm and the electron beam has a cross section with a corresponding length in a direction perpendicular to the scan lines. By pulsing the

809850/0694

Λβ- PIIN. 8815 12/12/77

Electron gun in connection with the scanning can also with a line-shaped Scanning a line under any direction across the. Target plate as well as a circle or other figure to be written. Thus, in the figure there is a diagonally directed line 110 which generates X-rays Impact anode specified. By equipping the output screen a collimator can be used to ensure that from each electrode impingement point (or cell) only a single elementary ray, like rays 112, over an object or body 114 to a detector achieved. Successively, these form elementary rays a diagonally directed detection line 118 on an input screen 120 of a detector in the form of a Cathode ray tube. The detector is here sensitive to the X-rays to be used Formed recording tube and is equipped with an input screen 120 in the X-ray quanta, for example Due to the photoconductive properties of the layer, a potential field can be created by a scanning Electron beam 122 can be read. A control arrangement 124 provides the synchronization between the scanning of an X-ray generating beam in the X-ray beam and the scanning of the exit beam 122 in the pickup tube. Obtained from the pickup tube

809850/0694

-Vf- '12/12/77

Signals can now also be processed on-line by a computing arrangement 126 and stored in a memory 120 written or on a monitor 130 for each cross-section being represented. If necessary, several x-ray emitter-detector pairs can be used in an arrangement according to FIG. 1, for example be included. The emitter-detector system according to Pig. 5 rotatable around that to be measured Object 114 must be mounted. If in an arrangement in the form of a regular polygon with an even number of ribs A radiator and a detector can be recorded opposite one another with this arrangement Absorption values in many consecutive cross-sections can be measured without performing mechanical movements. It can be for example wisely think of a regular hexagon, octagon or decagon, with half of the Sides is formed by radiators and the other half by receiving tubes. For a good separation between the elementary X-rays to each other it can be advantageous already for the electron beam to use some collimation by incorporating the anode target material into a matrix whose walls go through both to the outside and to the inside of the X-ray tube.

The walls are preferably made of lead or a

809850/0694

PRN.8815 _ 12/12/77

other, highly radiation-absorbing material. Dar-like materials also absorb electrons in sufficient mass. A two-dimensionally expanded detector according to FIG ) Dutch patent application 770329 ^ · used will.

In a preferred embodiment according to FIG. 6, the X-ray tracer is formed by a funnel-shaped cathode ray tube 1 ho with a stem part 142 in which there is an electron beam generation system ikh and in which or around which a beam deflection unit 146 is located. A funnel-shaped part 148 of the tube is double-walled, and an electron beam 150 moves between walls 152 and 15 ^ of this part of the tube in order to generate X-rays. At an end facing away from the electron beam generation system, the funnel is provided with a revolving anode target plate I56, for example in accordance with the description on the basis of FIG Axis I60 of the funnel is directed. An object 162 to be examined is arranged around the axis 160 of this system.

809850/0694

12/12/77

When the collimation of the X-ray beam is like this it is carried out that from each point of impact one in the funnel plane encompasses the entire object Fan beam is transmitted, if detected with a position-sensitive detector, is a

half the circular path of the electron beam 150 for the Measurement of a cross section is sufficient. When the X-ray beam is exactly in the plane of the funnel there would be no place to place a ^ detector. XJm solving this problem, the The target plate is designed so that only about an X-ray beam is generated in a semicircle, or it can be a comb-shaped unit made of target and detector are formed. If desired, tj with a fully circulating x-ray beam To be able to work, the X-ray beam can move somewhat out of the due to the geometry of the anode target Funnel level are directed, whereby an anode impingement ring and detector ring are arranged side by side can be. The non-perpendicular passage of the object through the X-rays can, for example be electronically corrected in the case of computerized tomography, by the way, this embodiment is, albeit very useful, for example, for head examinations, in particular, for example, for material analysis, for the

809850/0694

PHN. 8315 12/12/77

Locations of irregularities in ¥ tick and the same suitable.

In particular in all of the described

related preferred embodiments in which detection is carried out on-line, i.e. the one from this point of view first generation scanning X-ray examination arrangements, it is beneficial both for dose savings for the patient and for increasing the image quality, to work with a constant output signal, and thus the intensity of the X-ray beam to the

adjust the determined absorption. In x-ray tubes of the type described, this can be done quite simply by controlling the current of the X-ray radiation generating Electron beam can be carried out. For more details on this principle can refer to the DT-OS 2555675 should be referenced.

8Ό9 85 0/0 6-9 4

ε e r s η I

Claims (1)

PiIN. 8815 12.12.77 PATENT CLAIMS : 1. Arrangement for determining local Absorption differences in an object with the help of a scanning X-ray beam and an X-ray detector, characterized in that the X-ray source with an anode target, which at least has a large detection area in one direction, and having an electron beam deflection assembly for translating an electron impact leak across the Anode plate is equipped for generating an X-ray door scanning the object to be examined. 2. Arrangement according to claim 1, characterized in that that the X-ray beam is collimated for on-line reading from each point of impact onto the. same detector is directed. 3. Arrangement according to claim 1 or 2, characterized in that from several on tref f leak positions per electron beam scan of the anode target X-rays running parallel to each other are collimated. H. Arrangement according to one of Claims T, 2 or 3> characterized in that the X-ray tracer in relation 1st arranged rotatably on an object to be examined. 0985 0/0694 ORfQfNAL PIIN. 8815 Λλ. Λ2..ΊΊ 5. Arrangement according to one of claims 1, 2 or j, characterized in that it contains several X-ray emitters. 6. Arrangement according to one of the preceding claims, characterized in that it has a Contains site sensitive detector. 7 · Arrangement according to one of the preceding Claims, characterized in that the anodes- The target is provided with a cooling device. 8. Arrangement according to claim 1, characterized in that the anode impingement plate in two Directions has a large detection area. 9. Arrangement according to claim 8, characterized in that that the detector has the shape of a television tube and the scanning in the X-ray tracer and are coupled to one another in the detector tube. 10. The arrangement according to claim 1, characterized in that the X-ray tracer has a funnel! "Orin has, in which an at least partially circumferential anode target in an enlarged part of the Funnel received and a scanning X-ray beam to be generated is directed to the axis of the funnel. 11. The arrangement according to claim 20, characterized in that the anode impingement plate to one generating X-ray beam from a funnel 809850/06 . 881 5 12.12 J77 end face directed that he rubbed one of the anodes— hits the detector arranged on the target. 12. The arrangement according to claim 10, characterized in that a ring of the funnel partially from one Anode target and partly from an X-ray detector is captured. 13 · Arrangement according to claim 10, characterized by that a in the anode target ring Detector ring that can be irradiated on both sides is located and the arrangement has means for determining differential signals contains signal obtained from two detectors mounted diametrically in the ring. ß 0 9 8 ^r > 0/0694