DE2653465A1 - METHOD AND DEVICE FOR COMPUTER TOMOGRAPHY - Google Patents

Description

Pa ΐ e η t attorney

PHA 20751

-13, 41 , 76

PHILIPS MEDICAL SYSTEMS INC.

"Method and Device for Computed Tomography".

Scope of the invention

The general scope of the invention is tomography, i.e. it relates to generation radiological layer images of inner parts of a Body in one plane of this body by means of X-ray film recording devices. In particular, it relates to the area of the invention referred to as transyer tomography the method and the device for irradiating a plane of a body with an X-ray or gamma rays, to determine the absorption

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tion of each bundle when irradiating a part of the body and using the calculated multiple measured values for the reconstruction of individual absorption coefficients for each element of a certain element matrix in the plane of the body. State of the art

The description of a known method and a known device for transverse tomography is given in U.S. Patent 3,778,614. This pa tentschrift describes a reconstruction technique for a cross section through a body from a series of transmission measurements made by translational Moving a radiation source and a detector across the body and through Repetition of this translational movement for several angular orientations in the plane of the Average are determined.

The purpose of these measurements is, after computer analysis, of thousands of unprocessed information Bit about radiation attenuation by the Level of the body the absorption coefficient determine which is to be assigned to each element of a matrix defined in the plane of the body. This Method is useful for describing the interior of any body but first for the identification of inner ones

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PIIA 20751 I9.II.76

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Deviations in the human body. The absorption coefficients are different for normal body tissues, tumors, fat, etc., and thus result identif izleruiig ^v sdaten on soft tissue in a human body. Since tomography by means of computer reconstruction is particularly suitable for the identification of brain diseases and abnormalities, the disadvantages of the troubles that the patient feels during his illness through brain examination using pneumography, angiography and scanning with radioactive isotopes are eliminated.

In the known method, an X-ray tube X and a detector D, which are located on opposite sides Positions are fixed, moved linearly in translation, so that the X-ray radiation a Body B interspersed. With the help of collimators, a narrow bundle of rays is placed at the exit of the X-ray tube X and determined at detector B, so that the readings of the X-ray detector D at each translational and rotational position a measure of the total absorption along the specific path of the Each detector reading is saved for later computer processing Each linear scan is followed by a rotation of the X-ray tube * -detector combination around an axis,

PHÄ 20751

which is perpendicular to the plane of the body. The above description is graphical in FIGS. La and 1b shown.

In the known method, the scanning signals are processed in such a way that they are visual information messages and give values of the radiation absorption coefficients in the cross section of the body. Scanning signals from the detectors D arrive at a Analog-digital converter AD for converting the analog scanning signals into a digital form, which Signals are proportional to each radiation absorption, and are then stored in a storage unit-S saved. Computer analysis of the entire matrix of sampling signals, in one particular case, for example 28,000 points, results in absorption coefficients which are assigned to an element matrix that is suitable for the plane of the body B is defined. These absorption coefficients are based on the localized physical properties in the plane of the Body B related. After processing in the computer K, the absorption coefficients are stored in a memory unit S and then the conversion into analog signals with the aid of a Digital-to-analog converter DA. These signals control a display unit V, e.g. a cathode ray tube, with the information content that the absorption

Jt-

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tion coefficients for each matrix are leniently represented as an image. A permanent record of the picture provides a camera C. Fig. 2 shows an arrangement as described above.

A disadvantage of the known method and the known device is that a Scanning the entire cross-section of the body is required before the localized value of the Absorption coefficients can be derived. This is done by influencing the calculation of the Absorption coefficients at each point of the cross-section by the readings at each point of the X-ray beam caused. Therefore, the entire cross-section through the body has to be scanned and this scan cannot be limited to any particular important area. Farther are concerned with the stability of the X-ray tube and detector systems as well as with the mechanical precision high demands are made of the systems, since the calculation of the place values is carried out during the entire sampling time related to the absorption coefficient. Data need to be determined. Reconstruction problems can also occur moving parts of the body. A scanning movement resulting from a translational Movement with subsequent rotation is impractical and causes mechanical

I - - ■ ■

PHA 20751

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Vibrations and Versclileisst :. The occurring mechanical Problems further complicate the succession of translatory and rotary movement for Accelerate shortening of the sampling time. Further disadvantages relate to the complexity of the Restoring and refining the necessary program parts required Komputerprogramin »

Provides for eliminating the disadvantages of the known method and the known devices the invention described below has a significant advantage in that it is a new and fast scanning method indicates the acceleration large masses such as x-ray sources and detectors inherent to carry out the known Level of linear translational scanning are required, avoids.

Another important advantage of the invention is that it enables a reconstruction of Areas of the plane of the body with a limited number of transmission data that can be used in an environment containing the mentioned area have been determined.

Another advantage of the invention is that it creates a quasi-moment measurement of the site absorption constants as the scanning process progresses.

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265346S

A further advantage of the invention is that it results in a control of the scanning device with higher precision.
Presentation of the invention

These advantages are offered by a new method and a new device for examining a thin layer or a plane through a body by irradiating the plane of the body with X-rays or gamma rays. For investigation purposes, the plane of the body is represented as a two-dimensional matrix of elements which are defined by several concentric circles that form concentric rings. The outer ring is designated with the R-ring, the second outermost ring with the RI, etc. The elements in the rings are formed by distributing each of the rings into JSTr elements with the same sector angle. In this way, the designation N _R indicates a number equal to two or more than two elements of the outermost R ring j ^, while the RT ring is divided into iKL · elements, etc.

The method for determination of individual absorption or transmission coefficient for each item in the particular matrix element begins with the rotation of X-rays or gamma rays over 36O ⁰ around the outside of the body, wherein a beam for each concentric ring pre-

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1st seen, the dez-art in the to be examined Level is directed that it is continuously in contact with the associated ring.

From everyone stepping out of the Köx-per The bundle of rays becomes at N discrete angular intervals when rotating through 3 ^ 0 ° of the bundle of rays recorded a discrete output signal representing the Sum of the absorptions of the elements in each individual concentric from the relevant bundle of rays represents interspersed ring.

For the outermost R-ring, the N _n discrete output signals of the beam contacting the R-ring are used to derive signals proportional to the individual absorption or transmission elements, which elements are assigned to each of the N elements in the R-ring.

On the basis of the N _n discrete output

YES-I

signals of the beam touching the R-1 ring and the signals proportional to the individual absorption coefficients associated with the elements assigned in the R-ring, through which the beam comes into contact with the R-1-ring at each of the

N _{n Λ} discrete angular intervals, Signaxi— 1

Ie, which are proportional to the individual absorption coefficients assigned to each of the N _{n 1} elements in the R-1 ring.

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This process is repeated for each subsequent ring: for the R-2 ring towards the center of the concentric circles. For each concentric ring, signals are derived proportional to the individual ^{absorption coefficients assigned to each of the N elements in the 5} ring on the basis of the N discrete output signals of the beam contacting this ring and the previously derived signals that are proportional to the individual absorption or transmission coefficients that correspond to the Are assigned to elements in all outer rings through which the bundle of rays passes at each of the N discrete angular intervals,

According to a further advantage of the invention, certain beam measurements are concentric First rings according to a different coordinate system concentric rings translated, u.zw. around a point P in the plane of the body, and after that used to derive a signal that corresponds to the absorption coefficient at the location of a point P is proportional, creating a reconstruction process in an optional area of the plane of the Body is created.

A new apparatus for performing this method is described. A rotating one Frame, which in a fixed frame by means of -ei * -

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nes ball bearing is arranged is by a motor driven. An X-ray or gamma-ray source is fixed on an iron with the rotating frame connected arm mounted. The source generates one or more bundles of rays in a plane perpendicular on the * axis of rotation. The bundles of rays come in a system of detectors mounted on a second arm attached to the rotating frame. The bundles of rays are or gamma ray source as well as collimators assigned to the detector system and such aligned so that they touch with concentric rings around the axis of rotation of the rotating frame are defined in a plane of the body which is in or near the axis of rotation between the Source and the detector system is arranged.

In a preferred embodiment of the detector system, a reference crystal detector and several measuring crystal detectors are provided in groups, which groups can be brought into different positions on a path in order to collect different beams penetrating the body at different rotations of the rotating frame. For each measuring crystal detector, photomultiplier tubes are arranged to generate electrical signals , which signals the corresponding

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are proportional to the radiation intensity. To the magne tables store the radiation absorption signals Funds are provided in digital form. A digital computer with a memory program is for deriving of signals proportional to the absorption or transmission coefficient for the particular element enmatr Ix arranged in the plane of the body. These signals are stored and are then used for obtaining a reference of the absorption characteristics of the plane of the body.

The invention is described below with reference to the * Drawing explained in more detail, for example. Show it

Figs. 1 (a) and i (b) show a known method and a known device for performing transverse tomography,

2 shows a known plant for milling from absorption or transmission coefficients of a known, specific element matrix a series of transverse radiation measurements,

3 the orientation of an X-ray or a gamma radiation source and a detector in the device according to the invention for the rotation of a beam pattern around a body, in which defines an element matrix by concentric circles with linearly extending radii is,

: ■ - .: ... -7 Q 9: 8 2 3/0 6 95.

PHA 20751 19-11.76

FIG. K shows in detail the defined element matrix in the device according to the invention for determining absorption coefficients in a plane of a body,

5 shows another defined element matrix in the device according to the invention for determining the absorption coefficient at a certain Point,

6 shows the perspective image of a device according to the invention for rotating a radiation pattern through a plane of a body and to determine the radiation absorption after the passage of the Beam,

7 shows the radiation propagation of an X-ray tube according to the invention during the rotation thereof Tube around a body to be examined,

8 schematically shows the generation and detection of a beam according to the invention,

9 schematically shows another embodiment of the generation and detection according to the invention a bundle of rays,

10 schematically the according to the invention Collection, storage and processing of measurement data,

11 shows a block diagram for the compilation of a computer program for the Procedure of location-specific reconstruction according to the

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PHF 20751 11/19/76

Invention.

Scanning with concentric rings

a. Uniform scanning of a body FIG. 3 shows the sketch of a plane 101 of a body 111, which has to be examined by means of transverse tomography according to the invention. The body 111 is located between an X-ray or gamma-ray source 300 and a detector 301, which can be a scintillator and a photomultiplier and preferably also contains a collimator. For the sake of clarity, it is assumed that the detector 301 is along a path. 302 can move in such a way that beam bundles 310, 311 »312, 313 can be detected, which penetrate the body 111 at different angles from the source. Multiple detectors, each with an assigned collimator, can of course be used as detectors 301, 301 ', 301' ^! etc., or multiple detectors can be moved on track 302. The X-ray source 300 and the detectors 30I are connected to a C-shaped rotating ring 303 which can be rotated about an axis 0 perpendicular to the plane 101. In FIG. 3, the axis 0 is in the center of the body 111, but the body 111 can also be at any other point in the region of the beam 300 and

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of the detector 301 can be arranged.

As shown in Fig. 3, a series of concentric circles around the axis of rotation 0 are clearly defined. During the rotation of the ring 303 about the axis of rotation 0 is the X-ray beam or are the x-rays uninterrupted (as shown with an orientation rotation angle) directed perpendicular to the successive rays from the axis 0 to a point P. Through this is a bundle of rays, e.g. 310, always with the rope ring around the center 0 when the system is rotating Radiation source - detector 3OO-30I under control.

4 shows in detail the concentric system which is clearly defined about the axis of rotation 0. The beam 30I is shown with a special orientation during its rotation around the body 11 and is perpendicular to "a certain radius vector r at point P. By suitable collimation, an approximation of the concentric ring width Δ r through the beam width W can be achieved ^ The example shown in Fig. 4 shows the bundle of rays 310 when passing through the outermost concentric ring (i). The bundle of rays 310 is perpendicular to the radius vector r when passing through those with j = n.-1, n., 1, 2 and 3 designated elements shown-

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PHA 2075 19-11.76

They are elements from the totality of n th elements in the i-ring.

To describe the interior of the body 111 according to the element matrix, which is defined by concentric Rings and radius vectors according to Fig. 4 is formed, each small element is an unknown value assigned to the absorption coefficient. For example, this is the absorption coefficient for the element j = 1 in the i-ring with / u. specified; / u. for

/ 1.1 / l, iC

the element j = 2; / u. . for the j. Element. the The determined radiation absorption for the beam 310 is given by the sum of the mean value of the linear absorption constant for each given by the beam penetrated element.

During the rotation around the axis 0, the absorption of radiation between the source 300 and the detector is determined at 3OI n. Different positions, of which only one is shown in Fig. H. The radiation absorption for each with / ->. , designated measurement is simply the

t 1 y JtC

Sum of the linear absorption constants for each element penetrated by the beam, multiplied with a single geometrical factor created by the intersection of the bundle of rays is determined with each element. The rotation measurement steps of the beam 310 during

PHA 20751 11/19/76

the increase in the source 300 and the detector 30I 0 are denoted by an index Ic. This index k gells in steps equal to 1 from 1 up to k = 11. and is equal to the number of elements in the i-ring. The measurement of the radiation absorption in each position of the first dux-chsclinitteeile ring thus leads to the Equations

4 = 1

where k = 1, 2, ..., n.

The term (X.. Is the geometric Fak-XjJ —Ic

tor, created by cutting through the bundle of nerves 3IO is determined with each element j, where the bundle of rays 310 in contact with in k stages the ring i rotates.

Since j is assumed to be equal to k, i.e. the number of elements in the i-ring is equal to j and the Number of measurements on ring i is equal to k, equation (1) gives a system of k equations, where k equals n. with j = n. unknown parameters / u. . is. Solving the system of equations (i) returns the values / U assigned to each element in the ring with index i.

In the following scanning ring, the ring with the

J 0

- "Wf -

PHA 20751

November 19-76

Index i-1, performs the measurement of radiation absorption to a new system of equations

η. τ
x-1 n.

j = l J = I

where k = 1,2, ... n. _,

t ■ -

wherein. p (is the geometric factor given by

1, jk
the intersection of the bundle with the new ring with the index i-1, for example the bundle of rays 311 according to FIG. 3> with the elements of the outermost ring i, is determined.

The values / u. . are determined by solving equations (i). The solution to the system of equations .. (2) gives the values / u. . in the

/ i-l, J

Ring with the index i-1. The measurement in each scanning ring with decreasing radius gives a system of equations equal to (2) with terms on the right Page that · known values for / u. in the elements which refer to the outermost rings. It is clear that the number of elements of each outermost 'ring necessary for absorption lengthways of an inner ring, decreases rapidly the closer the scanning radius approaches point 0, i.e. the more the scanning beam approaches the center of rotation.- - ■

The characteristics of each location

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are therefore completely determined when each scanning ring is completed, without the overall scanning of the Cross-section of the body must be awaited.

The number of equations in each system equal to the system of equations (2) is quite small and can be reduced with the measurement of the inner rings as the radius decreases. If, for example, it is assumed that a scanning radius of the outer ring is in the order of 150 mm and an element width in the order of 3, each independent system of equations for the outermost rings consists of only several hundred equations. The solution for the unknown ax for each ring successively from the outermost ring to the inner rings requires a much shorter computing time than known X-ray tomographic systems. The further inward is measured, the more the number of measurements along the ring can be reduced (ie it can be determined that η. For the inner rings is smaller than for the outer rings, whereby the dimension of the element remains approximately constant), so that the size of the system of equations becomes smaller. The computing time is reduced accordingly when solving the / u of the inner ring.

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b. Ortsbe s timmte Reko nstruktio n

The method ztii "Determination of the absorption coefficient for the elements which are determined uniquely as elements in concentric rings around the axis of rotation (Fig. K), requires that all of the radiation absorption data, in the solutions of the equations of consecutive rings, especially for a particular element near Axis 0. Often, however, a diagnostician is initially interested in examining a specific point in plane 101 of body 111. It is possible to use the radiation absorption data as described above to reconstruct an absorption matrix around a point P in the cross section through the body, the is not centered on axis 0.

Fig. 5 shows the body 111 being scanned by rotating bundles of rays, of which only one bundle of rays -310 is shown. To a particular one Point P is a succession more concentric Circles shown with uniformly spaced radii. Determine these circles a number of rings, which are also spaced at a radius r. apart from each other. Of the The radius for each circle from the center point P is therefore

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(3)

rin j = 0,1,2, ...

Even if radiation absorption data is defined for a concentric one around the center 0 Ring system are collected, this data can be dtirch Coordinate conversion in dcis concentric ring system which is determined by the center point P and with radii defined by equation (3) is. The absorption value of a beam in contact with a ring with the radius and the center P coincides with a bundle of rays, the one with the ring with the center 0 with a radius r according to the equation

r = Ο + r cos (9-9) (k)

/ Pp

is in contact, in which equation θ is the angular coordinate of the point of contact and r, θ are the pole coordinates of P. With the aid of equation (4), the measured values f £ of the radiation absorption in the concentric ring system around the center 0 can be translated with a computer so that a series of radiation samples in contact with the concentric rings around P are obtained. These values are provided with the index j. represent radiation absorption values, the 3

completely along concentric circles 0 = Jr ₁

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would be measured around P.

These radiation absorption values along the ring j are at full? Summation over the ring j equals the sum of the intersections over
all rings outside the ring j. This relationship is written as follows

2 / Γ

d9 ₌

0 => Jr ₁ J 9. ^ _{+ 17} U _1x (5)

where θ. ,. "is a geometric parameter, ge-J jh-y + I

give through

-ι /. t 1 J VI

j, h-

The parameter θ is a measure of the path length between the circle with the radius h and the
Circle with radius h + 1.

From the equation (5), an expression Ax becomes the desired absorption coefficient · in P, as
follows written

j = 1

wherein / "of ^A bsorptionswert k, the coefficients of a radiation beam by Po. are given by

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577 ⁽¹ - ^Θ 1,2 id, I.

θ. J

J-1.2 - ¹¹ J-

For capital j, ^ Icj = -. -j (9)

k.
The coefficients τ "· from / -> . In the G-lei-

chung (7) decrease asymptotically with j . As a result, in a quasi-uniform distribution of the value of j over the cross section to be examined through the body, the contribution of the calculation of / U of the values of P. in areas surrounding P decreases essentially with j, ie the sampling of a

The area at a distance P from P influences I. ο

the computation of / u proportional with r ^J. This slow decrease in the effect of surrounding areas on the computation of / u at each point would make it necessary to use uniform scanning of the entire cross-section through the body in order to arrive at the image reconstruction. The solution for / u at point P, given in equation (7), indicates that the limitation of the sampling

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on a limited area of the cross-section the body to an = error in the reconstruction of the Image, unless the boundary of the area partially coincides with the boundary of the cross-section through the body together.

On the other hand, when calculating the difference in values for / u between two points, influenced the scanning in the surrounding areas as the difference

1 _ 1
¹ I 2

where r and r represent the distances between an area of a cross section through the body and the two points. For high values for r ₁ and r 1, the effect of the sampling in the surrounding area increases

_2

Areas essentially with r _{1 Q.} This rapid decrease enables the use of a differential approximation in the image reconstruction of a part of the cross-section to be examined through the body, without a complete, uniform scanning of the cross-section through the body being necessary. To continue this approximation, the mean value / u in a circle with a radius JY is first calculated with the aid of the following equation

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PHA 20751 19-11-76

⁼ lh J

h = o

With the help of equation (5) the equation (1O) converted as follows

& fit

(11)

ι r _2i

i, j " Q ^ _Λ V

(12)

where k ^ ^ - "ι ^ j - ο. ... λ-. ₁

ι, J if

^k i 1

1.1

, j Gj ^ ₁ ^ Ij 1, je, 1 J-1,2 ej-1j

(15)

The coefficients k. in equation (7) and k.

J ^e , J

in equation (ii) satisfy the following asymptotis marriage condition

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The equations (7) and (ii) thus result

λ,

- W ^ J

where ßf. . = - (-77- .Ic.. + Ic.)

. = -τ (4y. .k. - k.) (18)

The coefficient 0. takes along asymptotically

^e > J
_3
j ab and this rapid decrease allows a restriction on the number of terms in the second sum on the right side of equation (17) for the computation of ax - / U. This means that it is possible to restrict the scanning method to an area of the cross-section through the body which surrounds the area in which the reconstruction from / U to / u has to be carried out. Table 1 below contains numerical values for k. as

Function from j = 1 to 3 = 95 J for k. . as a function of

j from j = 1 to j = 10 (/ = 1θ) and for k. as a function

^e » 3

from j from j = 11 to j = 95j and for 0.. as a function

¹ y

from 3 from j = 1 to j = 10 C ^ = 10) and for 0. as

^e > J

Function of j from j = 11 to j = 95

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K.
■ 1 TABLE 1 . Iv.
1, J. • 76142E + 02 0.. and 0
ι ,, Ι e,, 1 fi t -.1O449E-O2 j .57735E + OO .6OI72E + OI .58689E-J-OO -.78441E-O3 1 • 32826e + 00 K. and K
ι., Ι e, j . ϊ 54664ε + 01 .17424E + 00 -.60305E-03 2 .22153E + 00 .II547E + OI .5O184E + O1 .84126E-01 -.47279E-03 3 .16542E + 00 • 24454E + 01 .46459E + O1 ■ 5172OE-OI -3768äE-O3 4th .13153E + OO • 37332E + O1 »43303E + 01 .36715E-01 - · 3θ46θΕ-θ3 5 .10903E + 00 .50167E + 01 TC .286O8E-OI 5 6th • 73064ε-01 .62974E + 01 XV.
e, J .23748E-O1 7th .81161E-O1 • 75764E + O1 .2061IE-OI 8th .71953E-O1 .88542E + 01 / .1847OE-O1 9 .64621E-O1 .10131E + 02 .I6944E-OI 10 .58645E-O1 .114O7E + O1 -.23816E-OI • 11 .53681E-O1 .12683E + 02 -.94539E-O2 12th .49493E-01 .38795E + 02 -.50385E-02 13th .45912E _r 01 .20222E + 02 -.30383E-02 14th .42814E-01 .13914E + O2 -.20470E-02 15th .4O1O9E-O1 .1O779E + O2 16 .37725E-O1 .88958E + OI 17th .3561OE-O1 .76298E + OI 18th .33719E-01 19th .32O19E-O1 20th O0482E.01 21 .29O87E-O1 22nd

.27813E-0 1 .40591E + 01 HtA 20751
11/19/76 .26647E-O1 .38230E + 01 2653465 23 .25575E-O1 .36153E + 01 -.24945E-03 24 .24585E-O1 .34310E + 01 -.20616E-03 25th .23670E-01 .32661E + 0T -.17216E-03 26th .22820E-01 .31176E + 01 -.14500E-03 27 .22029E-01 .29830E + 01 -.T23O7E-O3 28 .2129IE-01 .286o4E + O1 «-. 10519E-03 29 .20601E-01 .27482E + 01 -.9O485E-O4 30th .19955E-Ol .26451E + 01 -.7829IE-04 31 .19348E-O1 .25499E + OI -.68105E-O4 32 .18776E-01 .24617E + 01 -.59541E-O4 33 .18238E-01 .23798E + OI -.52293E-04 34 .17729E-01 .23Ö34E + OI -.46126E-O4 35 .17248E-OT .2232IE + OI -.4o849E-o4 36 .16793E-01 .21652E + 01 -.36311E-04 37 .1636 TE-01 .2IO52E + OI -.32391E-04 38 .I595IE-OI .20434E + 01 -.28990E-04 ' 39 .I556OE-OI .I9878E + OI -. '26027E-04 40 .I5I89E-OI .19352E + O1 -.23435E-04 41 .14834E-O1 .18854E + O1 -.21160E-04 42 .14496E-01 .I8383E + OI -.19155E-O4 43 .14193E-O1 .I7935E + OI -.17384E-O4 44 .13864E-O1 .I75O9E + OI -.15814E-O4 45 .13569E-01 . 171O4E + O1 -.14419E-O4 46 .13285E-OI
■ -'- ■ -7 0-9 8 2-3X0 . 16718E + 01
£ -9l5 -... i :::::.: .. -.13174E-04 47 -.12062E-04 48 -.11065E-04

SO .13Ο14Ε-Ο1 .16349E ₊ Oi Ρ11Λ 20571
19-11.76
2653465 49 .12753Ε-01 .15997Ε + 01 -.ιοι69Ε-ο4 50 .12502Ε-01 .1566ΟΕ + Ο1 -.93627Ε-05 51 .Ι226ΙΕ-ΟΙ . 153-38Ε + 01 -.8635ΟΕ-Ο5 52 .Ι2029Ε-ΟΙ .15029Ε + 01 -.79768Ε-Ο5 53 .ΙΙ8Ο6Ε-ΟΙ .14732Ε + Ο1 -.738Ο4Ε-Ο5 54 .ΙΙ59ΙΕ-ΟΙ .14447Ε + Ο1 -.68389Ε-Ο5 55 .11384Ε-Ο1 , ι4ι74ε + οι -.63463Ε-Ο5 56 .ΙΙΙ83Ε-ΟΙ .13911Ε + Ο1 -.58975Ε-Ο5 51 .ΙΟ99ΟΕ-ΟΙ ■ .13657Ε + Ο1 -.54877Ε-Ο5 58 .1Ο8ο4Ε-Ο1 .13413Ε + Ο1 -.5113ΟΕ-Ο5 59 .10623Ε-01 .13178Ε + Ο1 -.47699Ε-05 6ο .1Ο449Ε-Ο1 .12951Ε + 01 -.44551Ε-Ο5 61 .10280Ε-01 • 12731Ε + 01 -.4166ΟΕ-Ο5 62 , -10117Ε-01 -. 12520Ε + 01 -.39ΟΟΟΕ-Ο5 63 • 99583Ε-02 .12315Ε + 01 -.36549Ε-05 64 • 98Ο48Ε-Ο2 .12117Ε + 01 -.34288Ε-05 65.. .9656ΟΕ-Ο2 .11926Ε + 01 -.32200Ε-05 66 • 95117Ε-02 .1174ΟΕ + Ο1 -.30269Ε-05 67 _ • 93716Ε-Ο2 .1156ΟΕ + Ο1 -.28481Ε-05 68 • 92356Ε-02 .11386Ε + Ο1 -.26823Ε-05 69 • 91Ο35Ε-Ο2 .11217Ε + 01 -.25284Ε-05 70 .89751Ε-02 .11053Ε + 01 -.23855Ε-Ο5 71 .88502Ε-02 .1Ο894Ε + Ο1 -.22525Ε-05 72 .87288Ε-02 .1Ο74ΟΕ + Ο1 -.21286Ε-05 73 .86107Ε-02 .1Ο59ΟΕ + Ο1 -.20132Ε-05 74 ■ - ■ · - -7 0 9 823-ZO: eS - -19Ο55Ε-Ο5

PHA. 20571 19-11-76

26S3465

75 .84953E-O2 .1O444E + O1 -.18050E-05 76 .83838E-02 .10302E + 01 -.17110E-05 77 .82748E-O2 .1O164E + O1 -.16230E-05 78 .8I68OE-02 .10029E + 01 -.15406E-05 79 .8065IE-02 .98986E + OO -.14634E-O5 80 .79641E-O2 .97713E + OO -.13910E-05 81 .78657E-02 • 96472E + OO -.13230E-05 82 .77697E-02 .95262E + 00 -.12591E-05 83 .76760E-02 .94083E + 00 -.II99IE-05 84 • 75845E-O2 .92933E + OO -.11426E-05 85 .74952E-O2 • 91812E + OO -.10893E-05 86 .74079E-02 .90717E + 00 -.10392E-05 87 .73227E-02 .89648E + OO -.99189E-06 88 • 72394E-O2 .88605E + 00 -.94726E-06 89 .71579E-02 .87586E + OO -.90511E-06 90 .70783E-02 .86590E + 00 -.86528E-06 91 .70005E-02 .85617E + OO -.82762E-06 92 .69243E-02 .84666E + OO -.79200E-06 93 .68498E-O2 .83736E + OO. -.75827E-06 9h .67768E-02 .82826E + 00 -.72631E-06 95 .67054E-02 .81936E + OO -.69603E-06

An important property of both equation (7) and equation (17) is uniformity Averaging the absorption measurements over each ring of the image reconstruction sequence,

709 8 2 3/0695

PIIA 20751 19 11-76

which results from the integration over 2 Ht . The influence of the statistical fluctuations of the individual measurements from A is thus uniformly minimal for the entire reconstruction area.

Equations (7) and (17) give the solution to the reconstruction problem and equation (17) in particular determines the approximation for a location-specific measurement and reconstruction of / u. It is clear that an independent measurement of / u is required in equation (17). The measurement of / U only requires a rough scan of the cross-section to be examined through the body with not too strict demands on the statistical properties of the associated absorption measurements. Concentric ring scanner

Fig. 6 shows in perspective a concentric ring scanner. A fixed frame 60O carries a rotating frame 60I that rotates about an axis of rotation 602 is freely rotatable. A motor drive 624 is located in the fixed frame 6OO for driving the Rotating frame 60I. Two arms 603 and 604 which are approximately 180 ° apart are attached to the rotating frame 60I. Arm 603 carries an x-ray tube 6O5 and an associated x-ray tube collimator controller 606. The arm 6o4 carries a detector structure 607 with associated detector collimators.

PHA 20751 11/19/76

A slide 608 is provided so that a part of a human body 11 can be positioned in an opening 701 between the X-ray tube 606 / X-ray eye collimator control 606 and the detection structure 607. The carriage 608 is supported by a carrier 6O9. A control 610 for the slide ensures that the slide 608 executes a translational movement parallel to the axis of rotation 602 and thereby moves the body 11 to a point at which the beam from the X-ray tube 605 can penetrate a desired plane 101 of the body 111. In addition, the control 6IO allows the slide 608 to perform a translatory movement in each direction in a plane perpendicular to the axis of rotation, the axis of rotation being close to the desired area of the body 111.

Since the X-ray tube 6O5 around the rotation ■ axis 602 can rotate, are means for the tube cooling and for supplying the tube with electrical High voltage provided during rotation. These resources, presented in modular form, exist from a rotating water cooling system 611 and a high voltage slip ring structure 612. There is also means for controlling command signals and control signals to the X-ray tube 605

-7 0 9

PHA 207 * 51 19-11.76

26S3465

and the assigned collimator structure as well as the Ko 1.1 ima tor s belonging to detectors 6O7 are required during the rotation. Command and control slip ring structure 6ik is arranged for this purpose. Furthermore, a slip ring structure 613 for data transport is arranged in order to create a means for the transport of data signals from the detector structure 607 during the rotation.

7 shows a preferred orientation of an x-ray tube 656 and the associated collima Gate control 606 in relation to the detector and detector-collimator structure 6θ7

As indicated in FIG. 6, the X-ray tube 605 and the detector structure 607 are firmly connected to one another on the rotating frame 60I via arms 603 and 604. Rotation of the frame 60I about the rotation axis 602 (point 0 in FIG. 7) causes the X-ray pattern 700 to have a configuration that covers almost every body to be scanned arranged in the opening 701. In a preferred embodiment, the fan-shaped bundle of rays covers an angle 703 of approximately 30 °, the structure of the X-ray tube detector being rotated at a speed of one revolution per second for at least ten revolutions. The diameter of the opening 701 is approximately 65 cm. The length of the

PHA 20731 19-11.76

Arms 6θ3 and 6θ4 with the x-ray tube attached 605 including detector structure 607 is approximately 75 cm. The rotating frame 60I -will be used in relation to the Fixed frame 600 from a single precision ball bearing with an approximate diameter of 90 cm carried.

8 shows the scanning according to the invention with multiple radiation. The X-ray tube 6O5 continuously transmits a fan-shaped series of X-rays come out, but this series has to be collimated to form bundles of rays so that those already before are applicable. The collimators 806 and 800 are for generating a number arranged by bundles of rays, which have a cross section of a body 111 arranged in the opening 701 radiate through. For the sake of clarity, three pairs of detector systems are shown in position I, the consist of crystal scintillators and photomultipliers (811, 820; 812, 821; 813, 822). A reference oscillator 810 with associated photomultiplier 823 are stationary. The detector pairs remain in position X for the duration of the first rotation of the rotating frame 60I (FIG. 6). -At the beginning of the second The detector system pairs are rotated over the path 302 into position II for absorption coefficient detection of bundles of rays passing through

PHA 20751 19-11-76

go to this position, postponed. The detectors are moved at the beginning of the third -Umlaufs in the position III, etc. This shift of detectors at the end of a cycle and at the beginning of a following ensures that the whole _s in the opening 701 placed in body 111 can be scanned.

A preferred embodiment of the scanning system according to FIG. 8 consists of a device which can scan a test object which is located in a circle with a diameter of 50 cm around the axis of rotation 0. Thirteen detector units are provided, one of which is the reference 'pair 810-823 and the other twelve are displaceable in ten positions over the detector track 302. Each detector system is used to scan a 2 g ° sector of the entire scanning area, with ten revolutions through the X-ray tube / detector system for scanning the entire body 111 are executed.

The crystal detector 810 / photomultiplier 823 is used to generate a reference radiation absorption signal for all others. Detectors to determine possible temporal fluctuations in the radiation intensity of the radiation beam emerging from the X-ray tube 6O5. In Fig. 8

PHA 20751 11/19/76

the tube collimator 8o6 collimates a certain bundle of rays 855 that passes through one outside of the Location of the body to be examined Attenuator 850 goes. The absorption characteristics of the attenuator 85O are preferably chosen so that they are similar to the characteristics of the body to be examined. Tissue equivalent egg " Plastic is an example of an absorbent material that is suitable for this purpose. That Detector pair 810-823 generates a signal, the intensity of which corresponds to the X-ray intensity; proportional is after the beam from the attenuator 850 and from the collimator 800 has passed has been.

Each pair of detectors for the beam, which radiate through the body 111 to be examined generates a radiation of a certain intensity proportional signal after this radiation beam has penetrated the body. The crystal scintillators deliver a high frequency signal (visible light spectrum) that is proportional to the number of photons in the incident X-rays or gamma rays is. The ones assigned to each crystal scintillator -Photo-multiplying tubes that respond to the light energy of their individual scintillators an electrical signal proportional to the on

PHA 20751

11/19/70

the scintillators falling radiation intensity. For example, an electrical signal is proportional to the intensity of the beam 856 am Output of the photomultiplier tube 820 is generated. Likewise, crystal scintillator / photomultiplier pairs produce output signals proportional to intensity other beam in position I, in position II, etc. for the entire beam pattern after successive rotations of the X-ray tube / detector system.

In a preferred embodiment of this invention, the X-rays generated in the X-ray tube 605 are collimated with the aid of a 15 cm long collimator 806 on the X-ray source and a 20 cm long collimator 8OO on the detector structure 60h . This collimation at the X-ray source and at the detector determines bundles of rays with a rectangular profile of 1: 5 now width, as measured by scanning a corner of a lead plate in the middle of the "beam path".

The range of values at which the photomultiplier must respond can by covering of the body to be examined can be reduced with a material whose absorption is known, so that radiation intensities received in the detectors are kept as constant as possible

709823/0695

PHA 20751

11/19/76

after they have penetrated the body.

Fig. 9 shows another imple mentation SfOX ¹ IIi of the detector orientation. The detectors 910 and 910 are located on the path 901 and the detectors 920 and 921 on the path 902. According to the drawing, the detectors 9IO and 9II determine radiation absorption along circular rings that lie around the axis of rotation 0 and differ from those along those of detectors 920 and 921 is measured. Multiple positions can be determined on each track and the detectors can be pushed into place with each rotation until a defined ring matrix is completely scanned and detected. With the same purpose as in FIG. 8, collimators 906 are also arranged here in the X-ray tube 605 and the collimators 930 in the detectors.

The x-ray tube suitable for the particular embodiment as described above is a modified version of a Philips I60 kV Beryllium Window Tube Model MCN 160 (Philips I60 kV Beryllium window tube type MCN I60).

Suitable "detectors" include scintillation detectors such as NaI, CaF, BGO as well as proportional counters such as high pressure xenon detectors and solid matter detectors.

709823/0695

PHA 20751 19-11 -76

Flg. 10 indicates how the radiation absorption data, which have been determined by the detector systems, are processed with the photomultiplier acherii 1000, 1000, ... 1000 during the rotary scanning of a body. In each photomultiplier, a data signal is generated for each uniquely determined increment for each rotation of the x-ray source / detector system. These signals are individually amplified by amplifiers 10101, 10102, ... 10103, recorded one after the other by a multiplex system 1020, converted into digital form by the analog-digital converter 1030 and stored in a data storage medium 1040, such as a magnetic tape, disk or drum or stored in a solid storage tank. This data collection continues throughout the rotation for each detector position for each uniquely determined incidence level. During the data collection or after this process, a computer 1050 processes the collected data on the basis of a stored program in accordance with the method already mentioned earlier in this description. The output of computer 1050 is a sequence of digital data proportional to the absorption coefficients of each element in the particular circular ring matrix. These signals are stored in a data storage unit

-—-- ^ 70-9823 / 0695 -

PIiA. 20751 11/19/76

1060, which are identical to the unit 10 ^ 10, or can be the same. The digital output signals can can then be printed and / or converted into an analog form and used for a reproduction on a cathode ray tube, with the absorption coefficient for the specific matrix can be given in the cross section through the body to be examined.

FIG. 11 shows a block diagram which is used as a floor plan for the compilation of a computer program for localized reconstruction according to this description.

Explanation of the block diagram (flow chart) according to FIG. 11.

- After START 500, the determined absorption values and the required constants are read in at 501 or 502,

- it follows at 503 the reading of parameters for the image reconstruction, such as number of rings, Elements, etc.,

- at 30h or 505 an introduction of the program variable L or J follows,

- at 506 the coordinates (r, θ) of a re- construction point and the value /? · from the

Determined absorption values,

- at 507 the coordinates (r, θ) and

ο 9 g 2

-J0V -

PHA 20751 19-11-76

determined using the compensation formula ;,

- with 508 or 509 the given ία calculations dur clige runs,

- at 510 / u,, u - / u and / u are calculated, after which at 511 numbers or drawings are output,

- the calculations come to an end at STOP 512,

- The parts 520 and 530 indicate return coupling loops AA, BB, which are run through when the
Conditions according to 521 or 531 are not (n) met.

It will be clear that within the scope of the invention many modifications are given to those skilled in the art.

709823/0695

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Claims (1)

PHA 20751 11/19/76 PATENT CLAIM: 1. J method of examining a thin cross-section or plane of a body with X-rays or gamma rays, which plane is represented for investigation purposes as a two-dimensional matrix of elements with a number of concentric circles forming a number of concentric rings, where the outermost ring is designated with R-ring, the second outermost ring with R-1 ~ ring, etc., whereby each of the mentioned rings is divided into N elements, where the designation N "is a number of one- represents an equal sector angle of one of the included elements of the mentioned R-ring, wherein the R-1-ring is distributed into N ₁ elements, etc., which method comprises the following steps the turning of X-rays or gamma rays over 36O ⁰ around the outside of said body, wherein each beam is emitted outside of said body through one of said concentric rings and into continuous contact with said concentric ring, the recording of a discrete output signal for each of the beams emerging from the mentioned * body with N discrete winds intervals during the rotation of the rays 7098 23/06 95 ORIGINAL INSPSGTSD PIIA 20751 19.H .76 bundle over 3 ^ 0 °, which output signal is the total absorption the * x-ray or gamma tx numbers through the Represents elements in each individual concentric ring, which is penetrated by the corresponding bundle of rays, deriving signals proportional to the individual absorption coefficients associated with each of the K _n elements in the aforementioned R-ring, on the basis of the aforementioned N direct output signals from the beam in contact with the R-ring, deriving signals proportional to the individual, each of the N elements in the above R-1 ring assigned absorption coefficients on the basis of the mentioned N discrete out- κ— ι output signals from the beam in contact with the RI ring and, on the basis of the signals mentioned, proportional to the individual absorption coefficients assigned to the elements in the said R ring, by which R ring the beam is in contact with the R-1 —Ring goes at each of the N _n discrete angular intervals, and repeating the previous step for each subsequent concentric ring of the R-2 ring to the center of the mentioned concentric circles for deriving signals for each concentric 709823/0695 PlIA 20751 ι 9. 1 ι · 7.6 265346 Ring what signals are proportional to the individual each of the N elements in the ring are assigned absorption coefficients, based on the N discrete 'r Output signals from the one in contact with this ring standing beam and on the basis of the previously derived signals proportional to the individual absorption coefficients assigned to the elements in all outermost rings, through which Rings the bundle of rays at each of the N discrete angles. 2. The method according to claim 1, characterized in that that each ring in an equal number of N elements is distributed.
r 3. The method according to claim 1, characterized in that that the mentioned rotation step with successive rotations of the mentioned X-rays or gamma rays continue, with at least one beam on at least one particular one Ring on the first turn over 3 ^ 0 ° around the outside of the mentioned body is directed, and realigning the beam on at least one specific additional ring for each subsequent rotation over 3 ^ 0 ° around the outside of the body mentioned. 4. The method according to claim 1, characterized in that to derive N unknown derivatives 17 0 PHA 20751 19-part 76 Sorption or transmission coefficient if a digital ¹ computer is used to process the electrical signals, which represent a system of N equations. 5. The method according to claim 1, characterized in that that it further comprises the following step : generating a representation of the absorption of the elements of the plane of the body on the base of said signals proportional to the individual absorption coefficients associated with each of the N elements in each ring. 6. Method according to claim 5j, characterized in that that each ring in an equal number of N elements is distributed.
r 7. A method of examining a thin cross-section or plane of the body by means of X-rays or gamma rays, which plane is represented for examination purposes as a two-dimensional matrix of elements with a number of concentric circles forming a number of concentric rings, the outermost ring with R-ring, the second outermost ring with R-1-ring, etc., whereby each of the mentioned rings is divided into N elements, whereby the designation N _R includes a number of an equal sector angle- PIIA 20731 11/19/76 sender represents elements of the mentioned R-ring, where the R-1 ring is distributed into H elements, and so on κ— ι is, which includes the following steps: rotating the x-ray or gamma rays over 36O ⁰ to the outer side of said ICörper-s, wherein each beam is radiated outside of said body through one of said concentric rings and into continuous contact with the said concentric annular " recording a discrete output signal for each of the bodies emerging from the mentioned body Ray bundle with W discrete angle Intervals during the rotation of the bundles of rays over 360 °, which output signal represents the total absorption of the x-rays or gamma rays by the elements in each individual concentric ring which is penetrated by the corresponding bundle of rays, ' converting the aforementioned output signals into a system of translated signals proportional to the Radiation absorption measurements that go through concentric rings around a point P that is not coincides with the mentioned axis of rotation, and deriving a signal proportional to the absorption associated with the mentioned point P -70: 98 2 370 6 95 PIIA 20751 19-11.76 tion coefficients from the system of translated signals for a predetermined number of concentric rings to P.
ο 8. The method according to claim 7j, characterized in that the deriving of a signal proportional to the absorption coefficient is repeated for a number of points P in said plane of the body, and wherein on the basis of a number of signals proportional to those associated with said number of points P Absorption coefficients a representation of the absorption of points P in the plane of the body is generated. Apparatus for examining a thin cross-section or plane of a body with the aid of X-rays or gamma rays, which plane is represented for examination lines as a two-dimensional matrix of elements with a number of concentric circles forming a number of concentric rings form, the outermost ring being referred to as R-ring, the second outermost ring being referred to as R-1-ring, etc., each of the rings mentioned being distributed into N elements, the designation N _{n being} a number equal to one Secondary Jx represent gate angle enclosing elements of the mentioned R-ring, wherein the R-1-ring in N _n -tv- I Elements etc. is distributed which device -W- PIIA 20751 11/19/76 contains the following Means for rotating X-ray or gamma ray übei- 36O ⁰ around the outside of the body, each beam is atisgestrahlt outside the body through one of the concentric rings and into continuous contact with the concentric ring, Means for recording a discrete output signal for each of those emerging from the body Bundles of rays with N discrete ¥ angular Intervals during the rotation of the beams above 360 °, which output signal is the total absorption the x-rays or gamma rays through the elements in each individual concentric ring, the is penetrated by the corresponding beam, represents, Means for deriving signals proportional the individual, each of the N elements mentioned above Jk. R-ring assigned absorption coefficients on the basis of the mentioned N _n discrete output signals XV. nale from the one in contact with the R-ring Bundle of rays, " Means for deriving signals proportional to the individual _{absorption coefficients assigned to each of the N n Λ} elements in the mentioned R-1 ring on the basis of the mentioned N _{n Λ} discrete 709823/0695 PHF 20751 19-11.76 Output signals from the beam in contact with the R-1 ring and, on the basis of the aforementioned signals, proportional to the individual absorption coefficients assigned to the elements in the aforementioned R-ring through which ring the beam in contact with the R-1 ring passes through each of the N _Λ discrete angular indices, and Means for repeating the previous step for each subsequent concentric ring of the R-2 ring to the center of the aforementioned concentric circles for deriving signals for each concentric Ring, the individual absorption coefficients assigned to each of the N elements in the ring are proportional, based on the N discrete outputs from the one in contact with this ring standing beam, and proportional on the basis of the signals that have already been derived the individual absorption coefficients assigned to the elements in all the outermost rings, through which rings the beam passes at each of the N discrete angular intervals. 10. The device according to claim 9 j, characterized in that that further means for generating a representation of the absorption of the elements of the Level of the body on the basis of the mentioned sig- PHA 20751 11/19/76 nale proportional to the individual, each of the N elements absorption coefficients assigned to each ring are provided, 11. Device according to. Claim 10, characterized in that that the mentioned means for rotating X-rays or gamma rays over 3 ^ 0 ° around the outside the following parts of the body contain a fixed frame, a rotating frame carried by a ball bearing with respect to the stationary frame, wherein the rotating frame can be rotated about an axis of rotation by a motor with respect to the stationary frame, and an X-ray or gamma ray source, which is on a first, with the mentioned rotating frame Fixed arm mounted and set up to emit rays that are concentric Rings are in contact in a plane of one stationary body are determined, which is arranged in or near the mentioned axis of rotation. 12. The device according to claim 11, characterized in that that said means for recording each of the bundles of rays emanating from the body step out, contain the following parts a detector system mounted on a second arm, which second arm with the rotating 7 0 9823/0695 PHA 20751 men in an orientation of about 180 ° with respect to firmly attached to the first arm and in the path of the rays from the X-ray or gamma-ray source is arranged, which is mounted on the first arm, wherein the detector systems have absorption signals proportional to the total X-ray or gamma ray absorption generated by bundles of rays that pass through the concentric rings that are in the plane of the body is determined on dislorinated increments of rotation are, while the X-ray or gamma-ray source and the detectors are around the axis of rotation turn, Means for converting the signals into digital signals in accordance with the absorption signals, and Means for storing the digital signals. 13 · Device according to claim 1T, characterized in that that it also contains collimating means between the X-ray; or gamma ray source and the stationary body are arranged to form the beams. 14. The device according to claim 12, characterized in that that the detection system is a reference detector for determining the X-ray or gamma-ray absorption of a beam which not penetrated the body, and a group of one or more measuring detectors working in one . ■■ --- 1-709823 / 0695. . -. PHA 20751 11/1976 Number of positions to be brought on a track which is mounted on the zveite.n arm, which positions correspond to the positions which coincide with the bundles of rays. going through the various groups of concentric rings, which are determined in the body around the mentioned axis of rotation, and for each of the mentioned measuring detectors a photomultiplier tube, the input signal to each tube being the detector signal and the output of each photomultiplier tube of the detected absorption of one of the aforementioned Body penetrating radiation beam corresponds. 15. Device according to claim 14, characterized in that that it contains further collimating means between the body and the detectors is arranged to form the bundle of rays before their absorption is determined by the detector system. 16. The device according to claim 10, characterized in that the means for deriving the Absorption coefficients as digital signals based on the aforementioned recorded radiation absorption signals from a computer with a stored program for solving a system of N linear ones There are equations with N variables. 17 · Device according to claim 16, characterized in that - _ :: .- 17 ο PHA 20751 11/1976 indicates that it continues to be a storage unit for storing the digital signals containing the absorption coefficients for each element of the matrix represent in the plane of the body. 18. The device according to claim 17 j dadux-ch characterized, that the storage unit is a magnetic drum. 19 · Device according to Anspx-uch 17 »characterized in that that the game is more of a * unit than a magnetic disk, is. 20. The apparatus according to claim 17> characterized in that the storage unit is a magnetic tape system. . 21. The device according to claim 17 »characterized in that that the storage unit is a solid storage system. 22. The device according to claim 17s, characterized in that that the means for generating a representation of the. Absorption of the elements of the plane of the body contains the following Means for converting the stored digital signals representing the absorption coefficients, into corresponding analog signals that are proportional to the mentioned absorption coefficient are and a cathode ray tube assembly based on 709823/0695 PlIA 20751 19 «11.76 2S53465 the analog signals for generating an image display of the element matrix responding to the mentioned plane of the body by reproducing each element with an intensity which is jaroportional to the analog signal strength of the absorption coefficient. 23 · Device for examining a thin cross-section or plane of the body with the help of X-rays or gamma rays, which plane. is represented for research purposes as a two-dimensional matrix of elements with a number of concentric circles forming a number of concentric rings, the outermost ring being labeled R-ring, the second outermost ring being labeled R-1-ring, etc., each of the mentioned rings is distributed in N elements, where the designation N represents a number of elements of the mentioned R-ring that enclose an equal sector angle, the R-1-ring in N ₁ , 'elements, etc. distributed .κ— ι is, the device includes the following parts Means for rotating the X-rays or gamma rays over 360 ⁰ around the outside of the erwähntr th body, wherein each beam outside of said body through one of said concentric rings is broadcast therethrough and in continuous contact with said concentric ring, -709823706 ^ 5 PHA * 2O751 19.η-76 Means for recording a discrete output signal each of the bundles of rays emerging from the body mentioned, with N discrete angular 'r Intervals during rotation of the beams above 36Ο ⁰ , which output represents the total absorption of the X-ray odex gamma rays by the elements in each individual concentric ring radiated by the corresponding beam, Means for converting the mentioned output signals in a system signals proportional to the Radiation absorption measurements carried out by concentric rings around a point P, which does not coincide with the mentioned axis of rotation, and Means for deriving the signal proportional to the absorption coefficient corresponding to the one mentioned Point P is assigned, from the mentioned system of translated signals for a predetermined number concentric rings around P. Zk. Apparatus according to claim 23> characterized in that it further includes the following Means for repeating the deriving of the signal proportional to the absorption coefficient for a number of points P with the mentioned plane of the body, and _A. 45 PHA 20751 Means for generating a representation of the absorption of points P in the plane of the body on the basis of a number of signals proportional to those associated with said number of points P Absorption coefficient. That the mentioned means contain 25 · A device according to claim 24, characterized in that for rotating the X-rays or gamma rays over 36O ⁰ following around the outside of said body a fixed frame, a rotating frame supported by a ball bearing with respect to the aforementioned stationary frame, which is rotatable with respect to the stationary frame about an axis of rotation of a motor, and an x-ray or gamms. radiation source which is firmly connected on a first, men with said Drehrahrr arm is mounted _s wherein the above-mentioned X-ray or GammastrahlenqueHe is to designed to emit beams with concentric rings in contact, which are determined in a plane of a stationary body , which is arranged in or near the mentioned axis of rotation. 26. The device according to claim 25 j, characterized in that that the mentioned means of -709823/0695 PHA 20751 19-11.76 draw each of the lieraustx-etenden from the body Beam contains the following a detection system mounted on a second arm that is in one with the drill frame Orientation of about 180 ° with respect to the first arm and in the path of the · rays from the X-ray or Gamma ray source test is connected, which is mounted on the first arm, with the detector system Absorption signals proportional to the total x-ray or gamma ray absorption of beams that go through the concentric rings that are discrete in the plane of the body Rotation increments are determined while rotate the x-ray or gamma-ray source and detectors around the axis of rotation. Means for converting the signals into digital signals corresponding to the absorption signals, and Means for storing the digital signals. 27 · " Device according to claim 25, characterized in that it further contains collimating agents which are arranged between the X-ray or gamma ray source and the stationary body for forming the beam. 28. Device according to claim 26, characterized in that -jrr - PIIA 20751 11/19/76 indicates that the detector system is a reference detector for determining the X-ray gamma ray absorption of a beam that does not affect the body interspersed, and a group of one or more measuring detectors, the group of detectors in a number of positions on a track mounted on a second arm can determine which positions correspond to the positions that coincide with the bundles of rays passing through the various groups of concentric rings which are determined in the body around the axis of rotation, and contains a photomultiplier tube for each of the aforementioned measuring detectors, the input signal at each tube the detector signal and the output signal from each, photomultiplier tube corresponds to the measured absorption of a beam penetrating the body mentioned. 2 ° ·· Device according to claim 28, "characterized that it further contains collimating means between the body and the detectors arranged to 'form the beam before determining their absorption by the detector system are. 30. The device according to claim 24, characterized in that that the means for deriving signals PHA 20751 19-11.76 iiale proportional to the absorption coefficient, which are assigned to the points P, atis the system translated Signals for a predetermined number of concentric rings around points P from a digital computer with a saved Px "ogranim exist. 31. The device according to claim 30, characterized in that that it further contains a memory unit for storing digital signals that are proportional to the absorption coefficients assigned to the points P. 32. Device according to claim 31> characterized in that that the storage unit is a magnetic drum. 33 · Device according to claim 31 _}, characterized in that the storage device is a magnetic disk. 3 ^. Apparatus according to claim 31> characterized in that the storage unit is a magnetic tape system. · 35 · Device according to claim 31 »characterized in that the storage unit is a solid storage system is. 36. Device according to claim 319, characterized in that that the means for generating a representation of the absorption of points P in the 7Q9823 / 0695 PJIA 20/51 19.II.76 Level of body ex ^ s based on the number of signals proportional to the absorption coefficient assigned to the number of points P contain Means for converting the digital signals proportionally to those associated with the points P mentioned Absorption coefficients in corresponding analog signals proportional to those assigned to the points P. Absorption coefficients, and a cathode ray tube assembly responsive to the analog signals for producing an image representation of the matrix of elements of the points P in the plane of the body by rendering each point P with an intensity proportional to the analog signal strength of the absorption coefficient. 37 Device for examining a thin cross-section or plane of the body with the aid of X-rays or gamma rays, which plane is represented for examination purposes as a two-dimensional matrix of elements with a number of concentric circles forming a number of concentric rings, the outermost ring with R-ring, the second outermost ring with R-1 ring, etc., whereby each of the mentioned rings is divided into N elements, the designation N _D includes a number of ep.nen equal sector angles PHA 20751 Represents elements of the mentioned concentric R-ring, the R-1-ring in · N _T elements, etc. ± t— I is distributed, which device contains the following Means for rotating the x-rays or gamma rays through 3 <~> 0 ° around the outside of the body, each beam emitting outside the body through one of the concentric rings and in continuous contact with the concentric ring. will. . _: =. -. ::. .... ·; _l:; :: · _ · - .: Detector means proportional to each of the beams for deriving an analog signal the X-ray or gamma-ray absorption of the beam passed by the elements in each single concentric ring with which the bundle of rays goes at each discrete yangle interval is in contact at N discrete ¥ angular intervals during the rotation of the beam over 360 ° ,. Amplification means associated with each of the detector means for amplifying the analog signals are, Multiplexing means associated with the amplifying means for deriving analog signals in time Sequence are coupled according to the following sequence: first the N "signals, produced ι .. "7 o 9 PHA 20751 11/1976 conducts the R-ring, then the N signals, derived in the R-1 ring, iisw-. , Analog-digital conversion means for converting the analog signals into digital ones in chronological order Signals with the same time sequence, Means with the analog-to-digital conversion means are coupled to store the digital signals, Means for retrieving the N _p discrete signals from the storage means, which signals belong to radiation measurement values from the R-ring, and for deriving signals therefrom which are associated with the individual, each of the N _n elements in the R-ring Xv. Absorption coefficients are proportional, Means for recovering the N _n discrete output signals from the storage means, which signals are associated with the radiation measurements from the R-1 ring, and for deriving signals proportional to the individual associated with each of the N ₁ elements in the mentioned R-1 ring Absorption coefficients from the discrete output signals as well as from the signals proportional to the individual absorption coefficient assigned to the elements in the R-ring, through which the beam in contact with the R-1 ring at each of the '"N _x , _Λ discrete' κ— ι Angular intervals goes, PHA 20751 11/19/76 Means for repeating the previous step for each subsequent concentric ring from the ring R-2 to the center of the mentioned concentric Circles for deriving signals for each concentric Ring, the individual absorption coefficients assigned to each of the N elements in the ring are proportional, based on the N discrete outputs of the in contact with that ring standing beam and on the basis of the previously derived signals, which the individual, assigned to the elements in all outermost rings Absorption coefficients are proportional, through which rings the beam passes at each of the N discrete fin intervals, and Means for generating a representation of the absorption of the elements on the plane of the body the basis of the signals mentioned proportional to the individual absorption coefficients of the N elements in every ring. 82: 3X0-6..3 5