JPH0542135A - X-ray inspection apparatus - Google Patents

Abstract

PURPOSE: To accurately position an absorbing means, and reduce an excessively exposed region of an X-ray image by a method wherein a sub-region of the X-ray image wherein an absorption value is a specified threshold value or lower, is detected, and a position of the absorbing means to increase the absorption value of the sub-region to the specified value, is calculated, and the absorbing means is made to displace to the calculated position. CONSTITUTION: A signal from a television camera tube 6 is digitized by an image processing unit 13, and is accumulated under a form of a matrix of a gray value. Then, a detecting means 14 determines a contour wherein the gray value is larger than a specified threshold value in an X-ray image. Then, an operation means 16 calculates the position of an absorbing means 11 where a region on the outside of the contour of the X-ray image can be masked by the absorbing means 11 as much as possible. Then, the absorbing means 11 is moved to the calculated position by a control-driving means 17. At this time, the absorbing means 11 is guided to an X-ray beam 3 so that the X-ray beam 3 may be damped at a previously determined position. By this method, the absorbing means can be accurately positioned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an X-ray emitting X-ray beam.
To the x-ray source, the x-ray detector being arranged to face the x-ray source and serving to form an x-ray image of the object to be placed between the x-ray source and the x-ray detector; Power supply device connected to the X-ray source for supplying the current and voltage, absorption means that can be arranged between the X-ray source and the X-ray detector for attenuating the X-ray beam, and absorption values arranged in a matrix. The present invention relates to an X-ray inspection apparatus including an image processing unit connected to an X-ray detector for accumulating X-ray images.

[0002]

2. Description of the Prior Art An X-ray inspection device of this kind is known from European patent specification EP-B 1157688.

The cited patent specification discloses that substantial differences in contrast can occur in the x-ray image formed by the exposure of the object to x-rays. Since some of the X-rays do not pass through the object to be examined and are incident directly on the X-ray detector, or because the object to be emitted shows a substantial difference in absorption,
These differences in brightness of the x-ray image can occur. In medicine,
In the case of organs exhibiting high absorption, such as the heart being relatively transparent to X-rays, such as the lungs, the contrast within the organ in question is between the brightest and darkest areas of the entire X-ray image. A low X-ray image is obtained as compared with the contrast. A known method between the x-ray image and the object to be radiated by the absorbing means in order to create a dynamic range of the x-ray image which is as close as possible to the contrast between the brightest and darkest regions of the organ in question. Will be placed in. For this purpose, a first X-ray exposure is projected onto the object as a light image, via the X-ray image intensifier tube, the television camera cooperating with the exit window of the X-ray image intensifier tube, and the projection device. Is done. Therefore, an absorbing means for the x-rays, which has a light absorption proportional to its absorbed power, is manually guided into the light beam of the projected x-ray image to achieve the desired reduction of the dynamic range of the x-ray image. Such a method of positioning the absorber means is relatively cumbersome since it requires the use of an additional projection device, adds to the complexity of the X-ray examination apparatus and involves manual operation. Furthermore, due to the difference in the interaction of the X-rays and the light in question, the desired X-rays when the absorbing means occupy the position producing the desired optical attenuation.
The line attenuation is simply approximated.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an X-ray examination apparatus in which the absorption means are accurately positioned and the overexposed areas of the X-ray image are reduced. Another object of the present invention is to provide an X-ray image inspection apparatus in which the contrast of the X-ray image is accurately limited to a predetermined limit.

[0005]

[Means for Solving the Problems] To achieve this,
In the X-ray inspection apparatus according to the present invention, the image processing unit includes a detection unit that detects a sub-region of the X-ray image whose absorption value is less than or equal to a predetermined threshold, and an absorption value of the sub-region of the X-ray image up to a predetermined value. The image processing unit is connected to a drive unit for displacing the absorbing means to the position calculated by the image processing unit.

According to the present invention, when a part of the X-ray beam is incident on the X-ray detector without passing through an object arranged between the X-ray source and the detector, the X-ray image has a clear contour. , In which the image of the emitted object is visible, and outside that the recognition of the fact that the X-ray image is overexposed.
This automatic detection of the contour is realized, for example, by determining the gradient of each point of the X-ray image or by an image part based on a threshold, which is for example part of the maximum absorption value. Through contour detection, the position of the absorber of the X-ray beam in which the overexposed areas of the X-ray image are masked can be calculated and then this position can be adjusted automatically. The visibility of the relevant details is improved because the overexposed areas can no longer hurt the observer and, on average, have less scattered radiation due to the reduction of the x-ray beam. X
When a line image intensifier is used as an X-ray detector,
“Beering glare (ve
iling glare) is reduced if the absorber is in place. "Beering glare" is caused by scattered X-rays, scattered electrons and protons in an X-ray image intensifier tube, and is veil-like throughout the X-ray image. Besides the positioning of the absorber outside the contour of the X-ray image, it is usually advantageous to increase the contrast of the sub-regions located within the contour of the X-ray image by reducing the dynamic range of the sub-regions with respect to each other. To this end, very bright sub-regions can be automatically re-determined and the position of the absorber member with locally variable absorption, eg a radiation absorption wedge, can be adjusted automatically. This adjustment can be performed accurately by calculating the total absorption of the object and the absorption means.

Due to the automatic positioning of the absorbing means for the full absorption or partial transmission of X-rays, the positioning in the first case is based on the contour determination and in the second case on the absorption calculation.
Optimal adjustments for these measures can be obtained quickly. This is X
The ease of operation of the X-ray inspection apparatus and the quality of the X-ray image are improved.

An embodiment of the X-ray detection apparatus according to the present invention is
The absorbing means is substantially opaque to the X-rays, the detecting means comprises a contour calculation unit for calculating the contours of the sub-regions of the X-ray image, and the computing means of the absorbing means in the X-ray image on which the contour is located. It is suitable for calculating the smallest projection.

The position where the absorbing means covers the smallest X-ray beam is calculated by using the calculating means for the different positions of the absorbing means of the X-ray image where the projection is sufficiently outside the contour, and the projection of the absorbing means. Can be determined by This is the optimum position of the absorption means whose optimum position is adjusted via the drive unit.

One embodiment of the X-ray inspection apparatus according to the present invention is
The absorbing means comprises a first pair of slats having parallel straight sides and located on a laterally extending first surface of the x-ray beam, the slats being first in the lateral direction of the measurement. Displaceable in the plane of, and rotatable together in a first plane about the axis of rotation, the absorbing means further having parallel straight sides and extending parallel to the first plane. A second pair of slats located on a second surface of the second slats, the second pair of slats being displaceable within the second surface in the lateral lateral direction, the axis of rotation of the second surface. It is characterized by being freely rotatable around.

The optimum position of the absorption means is known, for example, by determining the intersection in the X-ray image between the contour and the first line extending through the center of the X-ray image, the intersection being stored in the image processing unit. It is given by the coordinates of a matrix of absorption values. Through the intersection found, it is determined whether it intersects or is tangent to the contour of a further point with respect to a second line extending perpendicularly to the line passing through the intersection center and the point of intersection. If the contours intersect at a second line, the same method extends parallel to the second line but repeated for further lines located closer to the edge of the image; perpendicular to the first line. And so on until a line is found that extends to and touches the contour without intersecting it. Therefore, for different angular positions of the first line through the center, a pair of parallel tangents extending perpendicular to the first line and tangent to the contour are calculated. By determining the two pairs of tangents surrounding the smallest area, the position of the absorbing means at which the projection of the plane of the slat coincides with the found tangent is known as the optimum position of the absorbing means. The drive unit rotates the angle absorbing means equal to the angle perpendicular to the tangent pair found in the completed coordinate system from the image matrix, and the translation of the slat by the drive unit results in the distance between the line pair and the center of the X-ray image. Compare.

A further embodiment of the X-ray examination apparatus according to the invention is characterized in that the absorption means consist of a circular diaphragm.

In this case, the optimum position of the absorbing means is determined by, for example, the smallest circle that surrounds the contour of the X-ray image and has the center of the X-ray image as its center.

In a further embodiment of the X-ray examination apparatus according to the invention, the absorption means consist of an absorption member exhibiting locally varying absorption, the power supply supplying the voltage and current generated by the power supply during the exposure time. Connected to the control unit to adjust,
The image processing unit is characterized in that it receives the adjusted exposure time, voltage value and current value and is connected to a control unit for applying these values to the computing means for determining the position of the absorbing means.

Based on the current and voltage of the X-ray source, the exposure time of the X-rays emitted by the X-ray source, the energy fluence, can be calculated in the control unit. During radiation of the object, the X-ray beam is attenuated by its interaction with the atoms of interest, which interaction may be the photoelectric effect or Compton or Rayleigh scattering. X-rays not detected by the X-ray detector after scattering contribute to the contrast of the X-ray image, while X-rays detected after scattering are detected.
Lines adversely affect contrast. The scattering of X-rays depends on the thickness of the radiated object. For the energy fluence detected at the detector by scattering, the following holds:

[0016]

[Equation 1]

Where X is the thickness of the object to be radiated, ρ ₀
Is the energy fluence from the source and μ is the linear attenuation coefficient for X-rays. The coefficient k (x) indicates the contribution of scattered X-rays to the detected energy. The factor k (x) depends on the geometry of the X-ray examination apparatus and the target thickness X of the possible presence of the scattering grid in front of the X-ray detector. Using equation (1), the thickness of the emitted object can be calculated from the exposure time and the measured energy fluences ρ _d and ρ ₀ calculated with the voltage and current applied to the x-ray source. Then the total thickness of the object and the absorption means at which the desired attenuation occurs in the X-ray image can be calculated. The effect of the position of the absorber on the contrast of the X-ray image is known relatively accurately, since the X-ray scattering of the absorber is determined by this calculation.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of an X-ray inspection apparatus according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an X-ray examination apparatus for medical applications, for example a fluoroscope or angiography. From the focus, the X-ray source 2 produces a beam of X-rays 3 which is incident on the X-ray detector 5. Due to the absorption difference of the object 7, the X-ray beam is locally intensity-modulated such that a projected image of the object 7 is produced on the entrance screen 4 of the X-ray detector 5. The X-ray detector 5 is an X-ray image intensifier tube which in this case emits light on an entrance screen whose X image is made of CsI, whereby the X-ray image is converted into an optical image. At the photocathode, the light image is accelerated by an electronic device to, for example, 20 keV and emits electrons that are focused on the exit screen 7'of the X-ray image intensifier tube 5 provided with the light-emitting layer. A reduced and increased brightness image of the entrance screen 4 of the X-ray image intensifier 5 is produced on the exit screen 7 '. X
Through the television camera tube 6 cooperating with the exit screen 7 ′ of the line image intensifier tube 5, the light image is converted into an electrical signal applied to the image processing unit 13. In the image processing unit 13, the signal from the television camera tube 6 is digitized and stored in the form of a matrix of gray values. In the X-ray image, the detection means 14 determines a contour whose gray value is larger than a predetermined threshold value. The calculation means 16 uses X
Areas outside the contour of the line image are masked by the absorbing means 11 as well as possible. The position of the absorbing means 11 is calculated. The calculating means 16 is the absorbing means 1 which completely absorbs the X-rays in this case.
The drive means 17 is then controlled to move 1 to the desired position. In addition to the restriction of the X-ray beam 3 by the absorption means 11,
Absorbing means 1 for attenuating the beam at a predetermined position
It is desirable to direct 1 to the beam. For this purpose, the calculation means 16 is connected to the control unit 15 which controls the power supply device 9 and adjusts the exposure time, voltage and current of the X-ray source 2.
The calculating means 16 is, for example, via the keyboard 17, the distance between the focal points of the X-ray source 2 and the entrance screen 4, the image reduction coefficient of the X-ray image intensifier 5, the exit screen 7'and the television camera tube 6. Information about a hole in a diaphragm (not shown) disposed between and. Above all, on the basis of the exposure time, the voltage and the current of the X-ray source 2, the calculation means 16 in this case, for example, a perspex.
A desired position of the absorbing means 11 composed of a wedge is calculated.

In FIG. 2, the absorbing means 11 and the housing 20 are attached. Iris diaphragm 22 and lead slats 2
4, 25, 26 and 27 are shown schematically. The drive unit 17 includes four step motors 17a, 17b, 17c,
It is formed by 17d. Via the stepper motor 17a the lead slats 24 and 25 can be displaced together in the direction of the axis 29, in which case the positions of the lead slats 24 and 25 are symmetrical with respect to the axis 29. Step motor 17b
Via the gear wheel 30, the lead slats 24 and 25 can rotate about an axis 29. The same applies to lead slats 26 and 27.

FIG. 3 shows an X-ray image of the hand. Since the X-ray is incident on the X-ray image intensifier tube 5 without being attenuated, the contour 32 is obtained.
The outer area is overexposed. In the present example, overexposure is achieved when the lead slats 24, 25, 26 and 27 are placed in the positions shown in which the distance from the image center 34 is the same for the masking lead slats 24, 25, 26 and 27. Substantially prevented. The position of the lead slats 26 along the line 36 is optimal when the lead slats 24, 25, 26 and 27 are independently displaceable with respect to the image center 34. In this case, a step motor 17 for displacing each lead slat is provided.

FIG. 4 schematically shows the calculation of the optimum positions of the lead slats 24, 25, 26 and 27 by the computing means 16 after the determination of the contour 32 of the digital image matrix 40 by the contour calculation unit and the intersection with the contour 32. Is determined along a line 1 extending through the image center 34 and surrounding the angle α with respect to the X axis. From the points of intersection 35 and 36 it is determined whether one or more points of the contour lie on this line, along a line extending perpendicular to the line l. In that case, this operation is repeated for additional lines that extend perpendicular to line 1 but are located closer to the edge of the image. Therefore, the positions of the lead slats 24 and 25 are known. The same method works for the line m surrounding the angle β with respect to the X axis.
To the positions of the lead slats 26 and 27. The area surrounded by the lead slats at this position is q
-It is given by p-sin (β-α). Where q and p are the lengths of the lead slats 24, 25, 26 and 27 on either side of the oblique projection. By calculating the surface area at a given angle β for a certain (eg 90) angle α, the setting can be known for the lead slats 24, 25, 26 and 27 with the smallest surface area. After finding the smallest surface area, the lead slats are rotated about the axis 29 by the desired angles α and β, after which they are displaced with respect to the center of the X-ray image.

FIG. 5 shows the absorption means 11, the lead slats being displaced by variable absorption, for example absorption members 43, 44, 45 and 46 with perspex wedges. The rotation of the wedges 43, 44, 45 and 46 about the axis 29 can be combined so that one of the stepper motors 17b and 17d that drives it in rotation can be omitted. These absorbing means make it possible to reduce the difference in intensity of the sub-regions located within the contour 32, as shown in FIGS. For this purpose, the calculation means 16 of the image processing unit 13 calculates the energy fluence ρ ₀ from the predetermined values of the exposure time, voltage and current of the X-ray source as follows: ρ ₀ (df) = 36J. tirr · (T / 100) ^2.1 / df ² (2) where: −df is the distance between the point at which the energy fluence represented by m is observed and the focal point of the X-ray source 2; −tirr is S -J is the current from the cathode to the anode of the X-ray source represented by mA; -T is the maximum voltage at which the electrons of the electron source represented by kVp are accelerated; ρ ₀ is given by nJmm ^-2 .

Without considering the radiation, after the radiation of interest with thickness Xp and absorption coefficient μ (m ⁻¹ ), the energy fluence ρ ₀ of the detector is :

[0025]

[Equation 2]

Using this equation, the thickness X of the radiated object is
p can be obtained by permuting the values for ρ ₀ (df) obtained by the equation (2). When the absorption value is very low in the sub-region of the X-ray image and the energy fluence of the detector should be reduced to ρ _d '(df) by a filter with thickness Xf, the thickness of the fielder can be easily calculated from can get:

[0027]

[Equation 3]

The dynamic range of the X-ray detector is the thickness X
The projection of a portion of the wedge with f can be effectively used by converting the absorbing wedge of the X-ray beam to a position that coincides with the over-luminance sub-region of the X-ray image.

Using the simple model for X-ray attenuation by the object as described above, the relationship between the fluence of the energy detected by the detector and the thickness of the object radiated cannot usually be determined sufficiently accurately. Dependence of the acceleration voltage of the X-ray source on the extinction coefficient μ The scattered radiation effect and the possible presence of a scattering grid between the emitted object and the X-ray detector have an effect on the energy fluence measured by the detector. The attenuation coefficient μ can be expressed as follows: μ = t + s (5) where t is the contribution to the attenuation by the photoelectric effect, s is the contribution to the attenuation by scattering, and s is a constant, while t is the lower It can be expressed as: t = t _ref · (T / E _ref ) ^−2.75 (6) where t _ref is a calibration value of the attenuation due to the photoelectric effect for energy E _ref , and the value is, for example, E _ref = For 100 kV, t _ref = 0.0008 m ⁻¹ . Furthermore, a pre-groove is made between the source and the object to be radiated by the A1 of the Ca filter in order to filter the low energy X-rays which do not contribute to the image formation from the X-ray beam. When the object is radiated, the low energy x-ray absorption of the object is greater than the high energy x-ray absorption, which increases the average energy of the x-ray beam as the object is further transmitted by x-ray (beam hardening). .. A relatively accurate expression of the energy fluence ρ _P behind a large number of i-radiated objects (filters, objects to be inspected, etc.) is: ρ _P (df) = ρ ₀ (df) exp [−3.2 (Σt _i · x _i ) ^0.63 −Σs _i x _i −0.3] (7) where X _i is the thickness of the material i in the direction of the radiation and df is the energy fluence ρ _P Is the distance between the point at which is observed and the focus of the x-ray source. The subscript p indicates that primary radiation, i.e. unscattered radiation, is involved. In addition to primary radiation,
Scattered radiation also contributes to the energy fluence of the X-ray detector. The contribution by Rayleigh scattering, where the X-ray dose is scattered over a small angle without energy loss, is given by: ρ _r (di) = ρ _P (di) × _P σr (sin ρ _m ) ^Er (8) Where: −ρ _r is the energy fluence of the Rayleigh scattered X-ray dose expressed in nJmm ⁻² ; −di is the distance between the focus of the X-ray source 2 and the entrance screen of the X-ray image intensifier 5; −X _P Is the thickness of the radiated object represented by m; -ρ _r is the linear interaction coefficient for Rayleigh scattering, eg 0.002 _m ^-1 ; -ρ _m is between the object edge and the center of the X-ray detector Angle; -Er is an experimentally determined constant value, for example Er = 0.
It is 2.

The model on which equation (8) is based is a flat disk of matter with an absorption equal to that of water.

The following equation holds for Compton scattered X-rays in which a loss of X-ray energy occurs: ρ _C (dp) = ρ _P (dp) 1 / 2s ² x _P G / (s + at) (9) where , Dp is the distance between the focal point of the X-ray source 2 and the point originating from the object 7 from which the Compton radiation was emitted. The factor of 1/2 is given for thin objects because the Compton scatter radiates on both sides. G is an empirically determined coefficient having a value between 0.5 and 2.0, which depends on the ratio of the thickness of the radiated object to the transverse dimension, and a is empirically determined. Constant term, where
a = 0.6.

Compton radiation reaching the X-ray detector ρ _C (d
The following equation holds for i): ρ _C (di) = ρ _C (dp) sin ² (ρ _m ) (10) From the surface where the Compton scattered X-ray faces the X-ray detector, cos
The coefficient sin ² (ρ _m ) is derived as it exits the radiated object with the angular distribution given by (ρ). Here, ρ is the angle surrounded by the ray 1 of FIG. 6 extending between the plane emitting Compton radiation and the center of the X-ray detector 5 with respect to the axis passing through the center of the X-ray detector 5. The integral over the discoid is the term
produces sin ² (ρ _m ).

From equations (7), (8) and (9), the following equation can be obtained for the energy fluence ρ _S (di) of the scattered X-rays of the detector: ρ _S (di) = ρ _C (di) + ρ _r (di) = ρ _C ( _d p) sin ² (ρ _m ) + ρ _P (di). x _P (sin ρ _m ) ^Er ρ _S (di) = ρ _P (dp) 1 / 2s ² Gsin ² (ρ _m ) / (s + at) + ρ _P (di). x _P (sin ρ _m ) ^Er (11) where ρ _P (dp) / ρ _P (di) = di ² / d p ²
Since is the inverse square decay, equation (11) can be applied: ρ _S (di) / ρ _P (di) = 1 / 2s ² x _P Gsin ² (ρ _m ) (di ² / dp ² ) (s + at) + x _The radiation detected by the _P (sin ρ _m ) ^Er (12) X-ray detector can be expressed as: ρ _d (di) = ρ _P (di) + ρ _S (di) = ρ _P (di ) (1 + ρ _S (di) / ρ _P (di)) ρ _d (di) = k (x _P ) ρ _P (di) (13) For example, the solution of the equation (13) by iterative adaptation of the target thickness x _{P. Yields} the thickness of the object x _P and then the thickness of the absorption means required to obtain the desired damping can be calculated. If the desired thickness of the absorption means is known as an excess bright sub-region of the X-ray image, the absorption means is displaced by the displacement means 17 so that the projection of the part of the absorption means exhibiting the desired thickness coincides with the relevant sub-region. Is displaced and rotated by. The absorbing means shown in FIGS. 2 and 5 are used simultaneously to absorb the absorbing means 24-27 and 43-4.
Obviously, 6 are preferably housed in the same housing 20.

[Brief description of drawings]

1 shows an X-ray examination apparatus for medical applications, for example a fluoroscope or angiography.

FIG. 2 is a diagram schematically showing an absorbing means, an iris diaphragm attached to a housing, and a lead slat.

FIG. 3 is a diagram showing an X-ray image of a hand in which an area located outside the contour is overexposed because the X-ray is incident on the X-ray image intensifier tube without being attenuated.

FIG. 4 is a diagram schematically showing calculation of an optimum position of a lead slat by a calculation means.

FIG. 5 is a diagram showing an absorbing means in which a lead slat is variably absorbed, for example, displaced by an absorbing member having a perspex wedge.

FIG. 6 is a diagram showing the relationship between Compton scattered radiation and the center of an X-ray source.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 X-ray inspection apparatus 2 X-ray source 3 X-ray beam 4 Incident screen 5 X-ray detector 6 Television camera tube 7 Target 7'Exit screen 11 Absorption means 13 Image processing unit 14 X-ray image detection means 15 Control unit 16 Calculation Means 17 Control driving means 17a, 17b, 17c, 17d Step motor 20 Housing 22 Iris diaphragm 24, 25, 26, 27 Lead slat 29 Axis 32 Contour 34 Image center 36 Line 40 Digital image matrix 43, 44, 45, 46 Absorption Element

Claims (6)

[Claims] 1. An X-ray source (2) which emits an X-ray beam (3) and is arranged to face the X-ray source (2) and should be arranged between the X-ray source and the X-ray detector. An X-ray detector (5) useful for forming an X-ray image of the object (7), and a power supply (9) connected to the X-ray source for supplying current and voltage to the X-ray source (2). , Absorption means (11) which can be arranged between the X-ray source (2) and the X-ray detector (5) for attenuating the X-ray beam and X as an absorption value arranged in a matrix.
An image processing unit (13) connected to the X-ray detector for accumulating the X-ray image, the image processing unit (13) detecting a sub-region of the X-ray image whose absorption value is equal to or less than a predetermined threshold value. The image processing unit (1) comprises a detection means (14) and a calculation means (16) for calculating the position of the absorption means (11) for increasing the absorption value of the sub-region of the X-ray image to a predetermined value.
3) X-ray examination apparatus, characterized in that it is connected to a drive unit (17) for displacing the absorption means (11) to the position calculated by the image processing unit (13). 2. The absorbing means (11) is substantially opaque to X-rays, and the detecting means (14) comprises a contour calculating unit for calculating the contours of sub-regions of the X-ray image, and computing means (16). 2) is suitable for calculating the smallest projection of the absorption means (11) in the X-ray image on which the contour is located. 3. Absorption means (11) having parallel straight sides and a first pair of slats (24), (25) in which the x-ray beam is located in a laterally extending first surface. The slats are displaceable in a first plane in the lateral direction of the side and are rotatable together in a first plane about an axis of rotation (29), the absorbing means (11) Further comprises a second pair of slats (26), (27) having parallel straight sides and located on a second surface extending parallel to the first surface, said second slats being (26) and (27) are the second in the lateral direction on the side.
3. The X-ray inspection apparatus according to claim 2, wherein the X-ray inspection apparatus is displaceable in the plane of, and rotatable about the axis of rotation of the second plane. 4. X-ray examination apparatus according to claim 2, characterized in that the absorption means (11) consist of a circular diaphragm (22). 5. The absorbing means (11) comprises absorbing members (43), (44), (45), which exhibit locally varying absorption.
(46), the power supply (9) is connected to a control unit (15) that adjusts the voltage and current generated by the power supply during the exposure time, and the image processing unit (13) is adjusted exposure time, voltage. 5. A unit according to any one of claims 1 to 4, characterized in that it is connected to a control unit (15) for receiving values and current values and applying these values to the computing means for determining the position of the absorbing means. The X-ray inspection apparatus described. 6. The X-ray examination apparatus according to claim 5, wherein the absorbing member is formed as a wedge, and the absorbing member can be arranged on two surfaces extending laterally of the X-ray beam.