DE3031949A1 - SCREEN EXAMINATION ARRANGEMENT FOR DETERMINING THE INNER STRUCTURE OF A BODY - Google Patents

Description

PHILIPS PATENTVERWALTUNG GMBH PHD 8O-O97

"Scattered radiation examination arrangement for determining the internal structure of a body"

The invention relates to an examination arrangement for Determination of the internal structure of a body, with at least one radiation source for emission from the Primary radiation penetrating the body with at least three different radiation energies along a primary beam path with a small cross-section, at least one slit diaphragm located outside the primary beam with a slit-shaped opening that extends into a extends approximately perpendicular to the primary beam direction, with a transverse to the slot longitudinal direction, Detector arrangement containing individual detectors, which are generated by the primary beam in the body, the slit-shaped opening penetrating the straw radiation is taken, and with an electronic device for processing the means of the detectors received scatter signals as well as for the representation of the processed scatter signals.

Such an arrangement is already known from DE-OS 27 13 58I. With their help, however, it is only possible to generate qualitative representations of e.g. layer images of a three-dimensional body, if not additional ones Corrective action will be taken. If, for example, the attenuation of the radiation on the primary beam resp. the path traversed by streaks is also taken into account are obtained by means of the arrangement Measured values according to the DE-OS 27 I3 58I known correction procedures to correct what the

Requires use of a digital computer. 30th

INSPECTED

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For example, when correcting a plane of the body, one walks assume that the line of Körporebcmo is scanned, the scattered radiation of which the detector arrangement reached without weakening by intervening tissue, then that is from the first cell The scattered radiation emitted in this line has not yet been subjected to any attenuation and can therefore be directly classified as Measure of the density in this cell can be used. The primary ray reaching the second cell of this row is weakened by the portion that is converted into scattered radiation in the first cell, and because this is Portion is known from the measurement of the first cell, it can be increased by correspondingly increasing the output signal of the detector associated with the second cell compared to the output signal of the one associated with the first cell Detector are taken into account. In the third cell of this line, the weakening must then be caused by the two first cells are taken into account, etc. - The first cell of the following row is the primary ray although it is also not weakened, the scattered radiation from this cell is caused by the one between the slit and cells of the previous row lying in this cell are weakened. Because the weakening of the radiation by but these cells were already determined in the previous measurement, that of the first cell of the second The measured value assigned to the line must be corrected accordingly. At the output signal of the detector, which is in the second cell of the second row measures the scattered radiation generated, must on the one hand the attenuation of the primary beam by the adjacent first cell and on the other hand the weakening of the scattered radiation by the cells of the line above must be taken into account, etc.

With this correction procedure, inner areas of body layers are only then displayed completely corrected

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if the outer areas of the body layer to be represented are also irradiated. Furthermore, when using this correction procedure only that generated by the primary beam in the body and running almost in the plane of the body layer to be placed

Scattered radiation can be measured, since then the corresponding attenuation coefficients for the individual pixels of the layer image not by possibly lying outside the body layer to be represented , Q Areas with strong absorption (bones, gas inclusions etc.) are falsified.

The object of the invention is to provide an anti-scatter arrangement to determine the internal structure of a body, with the help of which without the use of such Correction procedure in a simplified manner among other things, improved slice images can be generated.

This object is achieved according to the invention in that each detector supplies detector output signals that are dependent on the energy of the incident radiation and is connected to an electronic circuit, which is derived from the detector output signals assigned in each case to a primary radiation energy Scatter signals is formed by an electronic memory for storing comparison scatter signals is provided with the same examination arrangement and in the same way as the scattered signals from one irradiated with the primary radiation, known reference bodies are included that the electronic circuit and the electronic memory are connected to the electronic processing device, and that the electronic processing device is designed in such a way that with it a comparison of the scatter and comparison scatter signals in each case one

Radiant energy feasible and from the so with each other

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compared scatter or comparison scatter signals the internal structure of the body can be determined.

The scatter (S) or comparative scatter signals (V) (radiation intensities) measured with a radiation energy for a body area through which the primary beam irradiates are, as already mentioned, of the Electron density in the corresponding area of the body, from the weakening of the primary radiation in the body to

jQ to this area of the body and from the weakening there Scattered radiation in the body dependent. These three quantities represent unknowns. These are now the scatter signals compared with comparison scatter signals that were previously recorded on a known comparison body,

J5 by, for example, the quotient of the scatter signal and the Comparative scatter signal and from this the logarithm is formed (ln (S / V)), then this can, if this happens for one point on the body with at least three different radiation energies, the three unknowns be determined. The corresponding sizes for the reference body are known. The comparison a scatter signal with a comparison scatter signal must, however, with the same radiation energy in each case be made. In this way a simple determination of e.g. the electron density distribution in the Body area penetrated by the primary beam and thus a representation of e.g. slice images of the body possible if this is carried out for a large number of beam paths lying in the layer plane, e.g. parallel beam paths. will lead.

These Schiclitbilder no longer need with regard to the Attenuation of the primary or scattered radiation can be corrected. In particular, therefore, is also a representation It is possible to use high-quality slice images lying inside a body plane, i.e. it is not necessary

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more to be measured the entire cross-sectional plane of the body. Of course, body images can also be generated that are not in one plane.

It is also advantageous that, for example, variables such as sensitivity the detectors, the energy dependence of the multiple scattering in the body, etc., no longer have any influence on the quality of the reconstructed body layer or structure. They fall when comparing the Streuig or comparison scatter signals with one another if the body and the comparison body with the same scattered radiation examination arrangement are recorded in the same way, i.e. irradiated with the same primary radiation are. The body and the reference body should be as similar as possible.

According to an advantageous embodiment of the invention, the radiation source consists of an X-ray source or from at least three different δ rays Substances emitting energy.

This ensures that the radiation with at least three different radiation energies for. Can be provided.

After oirier advantageous Weitorbildung dw invention, the detector arrangement has in each case one by a detector and parallel to the main extension direction of the slit-shaped opening line a plurality of detectors.

The signals from one detector on each line (detector line) The measured scattered radiation is then used to determine the internal structure of the body, e.g. the electron density of the Body substance to the corresponding, the scattered radiation

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emitting body area, used. The electron densities obtained in this way are then averaged. Dcibei can Siert strongly absorbing body structures between the excited body portion and the detectors lokali _g and for example be taken into account by providing the corresponding detectors associated electron densities with suitable weights in the averaging, for example. The accuracy of the reconstruction can be increased by means of such a detector arrangement. In addition, the image-IQ quality is improved in that an increased number of the scattered photons emitted by the scattering center is measured.

/ * - In contrast, with a cellular detector, such as it is used in DE-OS 27 13 581, only one reduced image quality. This detector has no spatial resolution in the line direction. Consequently neither can any strongly absorbing ones lying between the excited body region and the detector arrangement Body structures (bones, air pockets, etc.) localized or are taken into account, so that they falsify the actual electron density in the excited body area.

The drawing shows exemplary embodiments of the invention.

Show it:
"~" 25

Fig. 1 is a section through the Un t he such ting h-

anordnuiig according to the invention, Fig. 2 is a block diagram for processing

the detector output signals from each detector,

Fig. 3 is a perspective view of the

Examination arrangement, and FIG. K shows a radiation source arrangement with three

Individual radiation sources of different Radiant energy.

1 shows a section through an examination arrangement according to the invention. It has, for example, an X-ray source 1, the polychromatic radiation of which is masked out by means of a diaphragm 2 to form a primary beam 3 with a thin cross-section, which irradiates a body 5 lying on a table k. The primary beam 3 runs along a primary beam path defined by it. The scattered radiation 6, 6 'generated in the area of the body 5 penetrated by the primary beam 3

ig achieved by one on opposite sides of the Primary beam 3 arranged slit diaphragm 7 »7'j their slot-shaped openings 8, 8 ', preferably adjustable in width, run perpendicular to the primary beam 3, one detector arrangement 9, 9 'each · The detector arrangements

9) 9 'consist of individual detectors 10, 10' that are side by side are arranged on a straight line parallel to the primary beam 3. The detectors 10, 10 'can, for example, be strip-shaped and be arranged so that their main direction of extent is parallel to the slot-shaped openings 8, 8 ' runs. In order to scan different areas of the body, the body 5 and the examination arrangement are relative to one another movably arranged.

Each detector of the detector arrangements 9i 9 ¹ supplies detector output signals I (E) which are dependent on the energy E of the scattered radiation impinging on it. The energy E of the scattered radiation is determined for a certain energy E of the primary radiation and for a certain scattering angle Θ at which the scattered radiation is scattered to the primary beam 3, according to the well-known Compton equation. The position of the slit diaphragms 7 ₅ 7 ¹ defines the angles Θ at which the scattered radiation is measured for each point on the primary beam 3. The energy dependence of the scattered radiation is therefore determined solely by the energy dependence of the Priniü rs trahlurxg.

y ** ' _: . :: .- ■. ".-%; : ο Jo I 94

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FIG. 2 shows a block diagram for processing the detector output signals. In each case one detector, e.g. detector 10, is connected to an electronic circuit 11, which registers scattered photons at only three different energies from the scattered photons of different energies impinging on the detector 10, which are generated due to the polychromatic X-ray radiation, namely I (El) , I (E2) and I (E3). From each of these scattered radiation energies E1, E2, E3 assigned

1Q detector output signals are then scattered signals S (El), S (E2), S (E3) formed. For this purpose, the electronic circuit 11 can have, for example, three circuits 12 forming energy windows, which only generate an output signal when the input signal (detector output signal) is within of a certain size range, which corresponds to a predetermined energy range of the scattered radiation. The output signals of the circuits 12 assigned to an energy range are then used to generate the Scatter signals S (E1), S (E2), S (E3) are added, which can also take place in the electronic circuit 11.

A scatter signal, which is recorded by means of a detector, can be represented in the following form:

(D

S (ElWN (El) / fexp- Γ / u (El, 11) dll |. | Exp- f Ai (El, 12) dl2 ά SL ' ^K \ _ J' JLJ ⁷ J

This equation 1 applies to all energies El, E2, E3 etc. Here, as already mentioned, S (El) is the intensity of the scattered radiation with the energy El, N (El) is the intensity of the primary radiation outside the body 5 with the Energy El, d Θ * (El) / d SL the differential cross-section for the scattering of the primary radiation, * J _Λ the electron density of the body 5 in the body point P under consideration (cf. Fig. 1), the fourth expression the weakening of the

• ψ ψ -

χ *

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Primary beam 3, the attenuation of the scattered radiation between the body and the point P, the scattered radiation measured _g detector between the radiation source 1 and the considered point P. body (path 11), and the fifth term (route 12).

For energies above 3.00 KeV, biological material contributes mainly the spread to the attenuation coefficient yU (cf. Eq. 1) at, so that this is in the form

can be written. Here Θ * (E) is the total Klein-Nishina scattering cross-section and j (l) is the position-dependent electron density. ·

After considering equation 2 in equation 1, the scatter signals S (E1), S (E2), S (Ej). to., an electronic computer 13 to which _: the electronic circuit is electrically connected, and the part of the electronic processing device .14 is. With the. Electronic computer 13 is connected to an electronic memory at the same time, in which yergleichs streusignale V (El), V (E2), V (E3) are stored, die.den scatter signals S (El), S (E2), S (E3) and correspond under the same conditions as these, ie with the same - radiant energies. El _is . Eg ^ cE3 ¥ 'än ~' e in a known comparison body similar to the body to be examined with the same. ·, Examination arrangement are included. The comparison body (not shown) can be, for example, a water phantom ».

The comparison between scatter and comparison signals in the computer 13 is carried out in such a way. ,, that at each an "energy El, E2, E3 der -. Quoti.ent S (El) / V (El) - etc. from a scatter signal and a comparison scatter signal

ÖAD ORIGINAL

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is formed and logarithmized. So you get one Theorem of three equal lengths with three unknowns. The equation for scattered radiation with energy El reads:

(3)

7J dll - ^ (El) / f / ^ U2, - ^ _U 2>]

= ¹ V-ZT- ^ Ei) /-.Un-yT (χι) _djL1 - (T (El) Γ (12, -Zf (I ₂ ) cU2

Corresponding equations apply for E2 and E3. The index k stands for the body 5 to be examined, while the index ν stands for the reference body.

From the system of equations 3 (equations for E1, E2, E3), the electron density Jr can thus be determined for each point P on the body through which the primary beam 3 irradiates. The electron densities ^ ⁷ (11) and ψ (12) of the reference body along the path 11 of the primary radiation and the path 12 of the scattered radiation are known, as are the Klein-Nishina scattering cross sections ^ (El), 6 ^ (El) (corresponding to the energies E2, E3). As already mentioned, the energy of the scattered radiation El can be calculated from the energy El of the primary radiation using the Compton equation. Of course, photons with more than three radiation energies can also be detected. The electronic circuit 11 would only have to have additional circuits 12 (or additional channels of a multichannel). The equation system obtained in this way would then be minimized in a suitable manner.

In each case a detector 10, 10 'etc. is thus with a electronic circuit 11, of which only one is shown in Fig. 2, connected, which in turn all are connected to the computer 13. The Memory 15 stores the comparison scatter signals for all points the primary beam passing through the reference body

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3. The determined by the computer 13 electron densities / or variables derived therefrom then can be displayed or store 16 temporarily in a bulk memory 17 (magnetic tape, disk or the like.) On a monitor.

In (.lor Fig. 3 LsL a perspective view of it Invention shown on anti-scatter arrangement. The slit diaphragm 7 has a long slot-shaped opening 8, so that a point P starting from the body and the scattered beam 6 excited by the primary beam 3 is generated with a very large opening angle Ot will. This scattered beam 6 hits a detector line which consists of individual detectors 10a, b, etc. which are parallel to the slot-shaped opening 8, which runs perpendicular to the primary beam 3. the The entire detector arrangement 9 or the slit diaphragm 7 can, in extreme cases, also completely surround the primary beam, e.g. cylinder-like, so that the primary beam 3 runs on the cylinder axis. Every single one of the detectors of the Detector arrangement 9 (cylindrical or as a two-dimensional Detector matrix) is then equipped with its own electronic circuit 11 (not shown) connected via the connections a-d etc. By means of one detector of the detector arrangement, one is then the internal structure of the body 5, e.g. the electron density /,, derivable. The electron densities each of a detector line relate to the same point P on the body Averaging determine an improved electron density at body point P.

Of course, the detectors 10a, b, etc. of a detector line can also be represented by a single rod-shaped detector be replaced, which in the direction of the line contains a local

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Has solvency, so that the scattered radiation intensity for different line sections i (: te been raised can (see. Fig. 2). For this purpose, e.g. rod-shaped scintillators with photo- _ are used to multiply their output signals processed according to the Anger camera principle. The longitudinal direction of the rod would then be parallel to the slot-shaped one Opening 8 or perpendicular to the primary beam 3

^ g Another radiation source 1 'for emitting primary radiation with at least three different radiation energies is shown in Fig. k . The radiation source 1 'has three individual radiation sources l8a-c emitting ζ) rays, e.g. one each of .__ Cs (0.66 MeV), Hg (0.28 MeV) and __Co (0.12 MeV). The three individual radiation sources 18a-c are located, for example, in the interior of a rotating disk 19j which has a radial channel 20 for the radiation exit for each individual radiation source. The disk 19 rotates about an axis at a suitable angular velocity. ¹ 21, so that one after the other the individual radiation sources 18a-c arrive in front of an outlet opening 22 of a radiation protection housing 23 which shields the radiation. The primary beam 24 passing through the outlet opening 22 is then collimated again by means of a diaphragm 25. The electronic circuit II bos.L tv.t in this case three circuits 12 forming energy windows, for example pulse height analyzers, which are matched to the radiation energies of the individual radiation sources 18a-c.

Of course, the individual radiation sources 18a-c can also be used in another suitable manner relative to a radiation exit opening can be arranged or moved, e.g. linearly. However, a

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Mixture of the three mentioned ζ) -beam emitting substances can be used, which is arranged for example in the rotating disk 19 at the location of one of the radiation sources l8a-c.

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Claims (1)

303 1 9A9 PHD 80-097 PATENT CLAIMS: 1. Investigation order for the investigation the internal structure of a body (5)? with at least one radiation source (1, 1 ') for the application of primary radiation penetrating the body with at least three different radiation energies along a primary beam path with a small cross-section, at least one slit diaphragm (7) located outside the primary beam with a slit-shaped opening (8) which is located in a direction running approximately perpendicular to the primary beam (3), with a detector arrangement (9) running transversely to the longitudinal direction of the slot, containing individual detectors (10), which is struck by the scattered radiation generated by the primary beam in the body and penetrating the slot-shaped opening, and with a electronic device (l ^ l) for processing the scattered radiation signals obtained by means of the detectors and for displaying the processed scattered radiation signals, characterized in that each detector supplies detector output signals dependent on the energy of the incident radiation and with an electro Niche circuit (ll) is connected, which forms scatter signals (S (El), S (E2), S (E3)) from the detector output signals (I (El), I (E2), I (E3)) assigned to a primary radiation energy that an electronic memory (15) is provided for storing comparison scatter signals (V (El), V (E2), V (E3)) which are known with the same examination arrangement and in the same way as the scatter signals from a known Comparative bodies are included that the electronic circuit and the electronic Λ PHD 80-097 Memory with the electronic processing device (l4) are connected, and that the electronic processing device is designed such that it is used to compare the scatter and comparison scatter signals (S (El), V (El); S (E2), V (E2); S (E3), V (E3)) can be carried out with one radiation energy each and from the so the internal structure of the body can be determined by comparing scatter or comparison scatter signals. 2. Arrangement according to claim 1, characterized in that the radiation source (l) is an X-ray source. 3. Arrangement according to claim 1, characterized indicates that the radiation source consists of at least three q consists of substances emitting different energies. k. Arrangement according to claim 3 ₅ characterized shows that three substances emitting rays are arranged separately from one another and can be guided one after the other in front of a collimator arrangement (22, 25) to mask out the primary beam. 5 · Arrangement according to claim 3 or 4, characterized characterized in that the substances emitting ^ rays are .__ Cs (0.66 MeV), Hg (0.28 MeV) and Co (0.12 MeV). 1 JI dU j ρ / 6 ο arrangement according to claim 1, characterized shows that the detector arrangement (9) has melu-oro detectors (10a, b) running through a cinon detector and parnllol to the main direction of expansion of the slit-shaped opening (8). PIlD 80-097 7. Arrangement according to claim 1, characterized in that the detectors consist of rod-shaped scintillators with photomultipliers arranged at the rod ends, and that the longitudinal direction of the rod runs parallel to the main direction of extent of the slot-shaped opening (8). 8. Arrangement according to one or more of the Claims 1 to 7, characterized in that the slit diaphragm (7) and the detector arrangement (§) surround the primary beam (3) like a cylinder, the primary beam running along the cylinder axis.