CA1164580A - Compton scatter diagnostic apparatus for determining structures in a body - Google Patents
Compton scatter diagnostic apparatus for determining structures in a bodyInfo
- Publication number
- CA1164580A CA1164580A CA000384328A CA384328A CA1164580A CA 1164580 A CA1164580 A CA 1164580A CA 000384328 A CA000384328 A CA 000384328A CA 384328 A CA384328 A CA 384328A CA 1164580 A CA1164580 A CA 1164580A
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- Prior art keywords
- scatter
- radiation
- detector
- signals
- primary
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Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/48—Diagnostic techniques
- A61B6/483—Diagnostic techniques involving scattered radiation
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/02—Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
- A61B6/03—Computerised tomographs
- A61B6/032—Transmission computed tomography [CT]
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/42—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis
- A61B6/4208—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector
- A61B6/4241—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector using energy resolving detectors, e.g. photon counting
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/48—Diagnostic techniques
- A61B6/482—Diagnostic techniques involving multiple energy imaging
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/58—Testing, adjusting or calibrating apparatus or devices for radiation diagnosis
- A61B6/582—Calibration
- A61B6/583—Calibration using calibration phantoms
Abstract
PHD 80.097 14 18.3.1981 ABSTRACT:
The invention relates to a Compton scatter diagnostic apparatus for determining the internal structure of a body. Like previously a reference body corresponding to the body, the body is irradiated with at least three different radiation energies in order to record reference scatter signals and scatter signals, respectively, with a primary radiation beam of small cross-section. The scatter signals and reference scatter signals are each time compared for one radiation energy, so that a set of formules consisting of at least three formules is formed for the quotient of the scatter sig-nals and reference scatter signals, so that the density distribution of the body can be determined therefrom.
The invention relates to a Compton scatter diagnostic apparatus for determining the internal structure of a body. Like previously a reference body corresponding to the body, the body is irradiated with at least three different radiation energies in order to record reference scatter signals and scatter signals, respectively, with a primary radiation beam of small cross-section. The scatter signals and reference scatter signals are each time compared for one radiation energy, so that a set of formules consisting of at least three formules is formed for the quotient of the scatter sig-nals and reference scatter signals, so that the density distribution of the body can be determined therefrom.
Description
P~D 80.097 l 18.3.1981 "Compton scatter diagnostic apparatus for determining structures in a body".
The invention relates to a diagnostic appara-tus for determining structures in a body, comprising a-t least one radiation source for generating a primary radia-tion beam of small cross-section which penetrates the body and which has at least three different radiat-ion energies~ at least one slit diaphragm which is situated outside the primary beam path and which com-prises a slit~shaped aperture which extends in a direct-ion approximately transversely of the primary radiation beam, a detector device which extends transversely of the longitudinal direction o* the slit and which com-prises separate detectors for the detection of scatter radiation which is produced in the body by the primary beam and which passes -through the slit-shaped aperture, and also comprising an electronic device for the pro-cessing and display of detector signals~
An apparatus of this kind is known from German Offenlegungsschrift 27 13 581. However, such an apparatus is suitable only for direc-tq~itative reproduction o~, ~0 for example, layer images of a three-dirnensional body if no additional correction steps are per~ormed For example, if the attenuation o~ the radiation along the pa-th ~ollowed by the primary beam or the scatter radiat-ion is also -to be taken into account, the measurement values obtained by means of the apparatus must be correct-ed in accordance with the correction methods which are also known from German Offenlegungsschrift 27 13 581, thus necessitating the use of a digital computer.
For the correction of the measurement of a slice of a body it is assumed, for example, that first aline in the bod~ slice is scanned whose scatter radiation reaches the ~etector device wi-thout attenuation by inter-... .
PHD 80.097 2 18.3.1981 mediate tissue. The scatter radiation emitted by thefirst cell of this line has not yet been attenuated, so it can be used directly as a measure for the density in this cell. Primary radiation reaching the second cell of this line has been attenuated by the energy converted into sca-tter radiation in the first cell and because this energy is known from the measurement of the first cell~ it can be taken into account by way of a corres-ponding increase of an output signal of the detec-tor associated with the second cell in comparison with the output signal of the detector associated with the first cell. Similarly?for a third cell of this line9 the atten-uation by the firsttwo cells must be taken into account, etc. For a first cell of a next line, the primary beam has not been attenuated either~ but the scatter radiat-ion from this cell is attenuated by the cells of tha preceding line which are situated between the slit and the relevant cell. Because the attenuation of -the radiat-ion by these cells, however~ has already been determined during the previous measurement~ the measurement ~alue associated with the first cell o~ the second line can be corrected accordingly. For the output signal of the de-tector which measures the scatter radiation produced in the second cell of the second line it is necessary to ta~e into accOunt on the one hand an attenuation of the primary beam by the first cell of this line and on the other hand the attenuation of the scatter radiation by the cells of adjacent lines.
Thus, this correction method enables completely corrected imaging of internal regions of body slices only if the outer regions of the body slice to be imaged are also ir~adiated. Furthermor0, if this correction methodsw~re used, only be the scatter radiation gen0rated in the body by the primary beam and extending substant~
ially in the plane of the body slice to be imaged should be measured, because then the corresponding attenuation coefficients for -the individual pixels of -the layer s ~ ~
PHD 80.097 3 18.3.1981 image will not be disturbed by any regions exhibiting strong absorption (bones, gas inclusions etc.) which are situated outside the body slice to be imaged.
It is an object of the invention to provide a Compton scatter diagnostic apparatus for the determinat-ion of the structure of a body which simply enables the ~ormation of improved layer images without using such a correction method.
This object is achieved in accordance ~ith the invention in that each detector supplies detector output signals which are dependent on the energy o~ the incident radiation and is connected to an electronic circuit for the ~ormation of scatter detector signals from the dif~erent primary radiation energies, the apparatus furthermore comprising an electronic memory for the storage of reference scatter signals which have been recorded ~or a known reference body by means of a similar diagnostic apparatus and in the same manner, said electronic memory being connec-ted to the electronic pro-cessing device which is adapted to perform a comparison of the scatter signals and the re~erence scatter signals at different radiation energies and to determine the internal structure of the body from the scatter signals and the reference scatter signals thus compared.
As has already been stated) the scatter signals ~S) and re~erence scatter signals (V) (radiation intensi-tie~) measured in a part of the body irradiated by the primary beam at a radiation energy are dependent on the electron density in the body region, on the attenuation of the primary radiation in the body preceding this body region, and on the attenuation of the scatter radiation in the body. These three variables are unknown ~uantities. When the scatter signals are compared with the reference scatter signals previously recorded for a known reference body, for example, by forming the quo-tient of the scatter signal and the reference scatter signal and therefrom the logarithm (1n(S/V~), the three -` ~ 3 645~V
PHD 80.097 ~ 18.3.1981 unknown varia'bles can be determined therefrom if the procedure is performed each time for a body point with at least three different radiation energies. The corres-ponding variables for the reference body are known. The comparison of a scat-ter signal with a reference scatter signal, however, should always be performed for -the same radiation energy. This ena'bles a simple determination of, for exarnple, the electron density distribution in the body region irradia-ted by the primary beam and hence the reproduction of, for example, layer images of' the body if this procedure is executed for a large number of, ~or e~ample, parallel beam paths situated in the plane of` the slice.
These layer images need no longer be corrected as regards the attenuation of the primary radiation or scatter radiation, Notably the reproduction of high-quality layer images of parts which are situated inside a body slice is thus also possible, without the nccessi-ty, i.e. to measure the total cross-section of the body.
Obviously9 layer images of a body which are not situated in one plane can also be formed.
It is also advantageous that~ for e~ample, variables such as the sensitivity of the detectors, the enargy dependency of the multiple scattering in the bo~y etc. no longer influence the quality of the re-constructed body slice or body structure. During the comparison of the scatter signals and the reference scatter signals these variables cancel one another if the body and the reference body have been measured by means of the same scatter diagnostic apparatus and in the same manner, i~e. if they have been irradiated with the same primary radiation. The body and the reference body should resemble one another as much as possible.
In a pref'erred embodiment in accordance with the invention, the radiation source consists of an X-ray source or of at least three substances emitting gamma rays of different energies.
o PHD 80.097 5 18.3.1981 It is thus achieved that the radiation of` at least three different radiation energies becomes simply available.
In a further embodiment in accordance with the invention, the detector device comprises several de-tectors each time in a row which extends through a de-tector and parallel to the principal direction of the slit-shaped aperture.
The scatter radiation each time measured by a detector on a line (detector row) is then us0d for the determination of the internal body structure, for example, the electron density of the bod~ substance at the corresponding body region which emits the scatter radiation. Subsequently, the electron densities thus obtained are averaged. For example, strongly absorbing body structures between the activated body region and the detectors can then be localized and taken into accourlt in that 9 for example, the electron densities associated with the corresponding detectors are suitably weighted for the averaging. The reconstruction accuracy can be improved by such a detector device. The image quality is additionally improved because a larger number of the scatter photons emitted by the scatter centre are measured. Because the ]ine-shaped detector described in DE 27 13 581 does not have local resolution in the line direction, it is not suitable for the re-construction of highly absorbing body struc-tures (bones, air inclusions~ etc.) which are situated between the activated body region and the detector device~ so that these structures cannot be taken into account~ with the result that the electron density in the activated body region is not properly reproduced.
The drawing shows embodiments in accordance with the invention.
Figure 1 is a sectional view of the diagnostic apparatus in accordance with the invention, Figure 2 shows a block diagram for the pro-5 ~ (~
PHD 80.0~7 6 18.3.1981 cessing of' the detector output signals of each time one detector, Figure 3 is a perspective view of the diagnos-tic apparatus, and Figure L~ shows a radiation source device com-prising three separate radiation sources of dif~erent radia-tion energies~
Eigure 1 is a sectional view of a diagnostic apparatus in accordance with the invention. It comprises~
for example, an X-ray source 1 whose polychromatic radiation is stopped down by means of a diaphragm 2 in order to form a primary beam 3 of small cross-section which irradiates a body 5 positioned on a table 4~ The primary beam 3 follows a primary beam path def`ined by lS this beam. The scatter radiation 6, 6~ produced in the region of the body 5 irradiated by the primary beam 3 reaches a detector device 9, 9~ each time via a sli-t diaphragm 7~ 7~ which is arranged on the opposite sides of the primary beam 3 and whose slit-shaped apertures 8, 8~ whose width is preferably adjustable extend per-pendicularly to the primary beam 3. The detector devices 9, 9~ consist of separate detectors 10, 10~ which are juxtaposed in a straight line which e~tends parallel to the primary beam 3. The detectors 10, 10l may be~ for example, strip-shaped and be arranged so that their principal dimension extends pa~allel to the slit-shaped apertures 8, 8'. ~or the scanning o~ diff'erent regions of the body, the body 5 and the diagnostic apparatus are arranged to be movable with respect to each other.
Each detector of the de-tector devices 9, 9 t supplies detector signals I(E) which are dependent on the energy E of the scatter radiation incident thereon.
The energy E o~ the scatter radiation is determiIled f'or a given energy E of the primary radia-tion and for a given scatter angle ~ at which the scatter radia-tion is scattered with respect to the primary beam 3 in accOr-dance with the generally known Compton equationO The 8 ~
, . ~ , PH~ 80.o97 7 18.3.1981 position of the slit diaphragms 7 t 7~ de~ines the angles e at which the scatter racliation is measured ~or any point on the primary beam 3. The energy-dependency o~ the scatter radlation, there~ore, is determined only by the energy-dependency of the primary radiation.
Figure 2 shows a block diagram for the pro-cessing of the de-tector output signals. A detector, for example~ the detector 10, is each time connected to an electronic circuit 11 which records scatter photons at only three different energies, that is to say I(E1), I(E2) and I(E3), on the basis o~ the scatter photons of di~ferent energy which arrive at the detector 10 and which are generated on the basis of the polychromatic X-rays. Scatter signals S(E1), S(E2), S(E3) are then form-ed from the de-tector output signals each time associated with one of the scatter radiation energies E1, E2, E3.
To this end, the electronic circuit 11 may comprise, for examplé, three circuits 12 which ~orm energy windows and which produce an output signal only if the input ~0 signal ~detector output signal) is within a given range which corresponds to a predetermined energy range of th~ scatter radiation. The output signals of the circuits 12 each time associated with an energy range are then added in order to produce the scatter signals S(E1), S(E2), S(E3); this operation can also be per~ormed in the electronic circuit 11.
A scatter signal recorded ~y means of a de-tector can be represented as follows:
S(El)~ N(E) ~ Yk [exp -~ /u(E1~ l1)dll~ .
[exp - f/u(E1, 12) dl2] (1) This formule (1) is applicable to all energies E1, E2~
E3 etc. As has already been stated, S(E1) is the intensi-ty of the scatter radiation with the energy E1, N(E1) being the intensity of the primary radiation outside the ``--` ~ 3 ~580 PHD 800097 8 18.3.1981 body 5 with the energy E1, d ~(EI)/d Q being the differential effective cross-section for the scatt~ring of the primary radiation, ~k being -the electron density o~ the body 5 in the body point P considered (see Figure 1), the rourth term being the at-tenuation of the primary beam 3 between the radiation source 1 and the relevan-t body point P (path l1), the ~ifth term being the attenuation of the scatter radiation be-tween the body point P and the detector measuring the scatter radiation (path 12).
In the case of biological material, for energies in excess of 100 KeV mainly the scattering con-tributes to the attenuation coefficient /u (see formule 1), so that i-t can be expressed as follows: , /u (E,l) = ~(E) . y(l) (2) Therein, ~(E) is the overall Klein-Nishina effective scatter cross-section and ~(l) is the location-dependent electron density.
After application of the formule (2) to -the ~ormule (1), the scatter signals S(E1), S(E2), S(E3) are applied to an electronic computer 13 whereto the electro-nic circuit 11 is electrically connected and which f'orms part of the electronic processing device 14. ~lso con-nected to the electronic computer 13 is an electronic memory 15 which stores re~erence scatter signals V(E1) 9 V(E2), V(E3) which corr0spond to the scatter signals S(E1), S(E2), S(E3) and which have bcen recorded under the same circumstances as the latter signals, that is to say with the same radiation energies E1, E2, E3, for a known reference body which corresponds to the body to be examined and by means o~ the same diagnostic apparatus.
The reference body (not shown) may be, for example, a water phantom.
The comparison between scatter signals and reference scatter signals in the computer 13 is executed so that each time for an energy E1, E2~ E3 the quotient S(E1)/V(El2) etc. of a scatter signal and a re~erence 5 8 ~
PHD 80.097 9 18.3.1981 scatter signal is formed and the logarithm -thereof is formed. Thus, a set of three formules with three un-knowns is obtained. The formule for the scatter radiation having the energy E1 is as follows:
ln ~ = ln ~ - ~(E1)~fk(11) - ~V(11)~ dl1 - ~(E1)~
[~k(l2) yv(12)~cl12 (3) Similar formules apply to E2 and E3. The index k denotes the body 5 to be examined, ~hilst the index ~ denotes reference bodyG
From the set of formules 3 (formules ~or El~ E2, E3) the elec-tron clensity ~k can thus be determined each time for a body point P irradia-ted by the primary beam 3.
'~he electron densities y~ (11) and ~V(12) of the reference body on the path 11 of the primary beam and the path 12 of the scatter radiation, respectively, are known, so also the Klein-Nishina effecti~e scatter cross-sections ~(E1), ~(E1) (similar for the energies E29 E3). As has already been stated, the energy of the scatter radiation E1 can be calculated from the energy E1 of the primary radiation via the Compton ~ormule. Obviously, photons can also be detected at more than three radiation energies.
The electronic circuit 11 would re~uire only more cir-cuits 12 (or additional channels of a multiple channel) for this purpose. 'rhe set of` ~ormules thus obtained would subsequently be suitably minimized.
A detector 10, 101 is thus each time connected to an electronic circuit 11, only one o~ which is shown in Figure 2, all said circuits 11 being connected to the same computer 13. The memory 15 also contains the refer~
en¢e scatter signals f`or all points on the primary beam 3 passing through the reference body. The electron densi-ties ~k determined by the computer 13, or the ~ariablesderi~ed therefrom, can be displayed on a moni-tor 16 or be stored in a bulk memory 17 (magnetic tape~ memory disk ~l~9~
PHD 80.097 10 18.3~1981 or similar).
Figure 3 is a perspec-tive view of the scatter diagnostic apparatus in accordance with the invention.
The slit diaphragm 7 has an elonga-te slit-shaped aper-ture 8 9 90 -that a scatter radiation beam 6 having a very large angle o~ aperture ~ which starts from the body point P is activated by the primary radiation beam 3.
The scatter radiation beam 6 reaches a detector row which consists of separte detectors 10a, b etc~ which are situated in a row which extends parallel to the slit-shaped aperture 8 which ex-tends perpendicularly to the primary beam 3. In an extreme case, -the complete detec-tor device 9 or the slit diaphragm 7 can alternatively completely enclose the primary beam, for example, in a lS cylindrical manner, so tha-t the primary beam 3 extends along the cylinder axis. ~ach ~eparatedetector of the de-tector device 9 (shaped as a cylinder or a two-dimensional detector matrix) is then connected to its own electronic circuit 11 (not shown~ via the connec-tions a-d~ etc. ~
variable, f`or example 9 the electron density k which cha-racterizes the internal structure of the body 5 can then each time be derived by means of a detector of the de-tector device. The electron densities of each detector row then relate to the same body point P. An improved electron density at the body point P can be determined from these densitiesa for e~ample~ ~y weighted av0raging .
Ob~iously, the detectors 10a, b etc. o~ a de-tector row can also be replaced by a single, rod-shaped detector which has a local resolution in the direction of the row, so that the scatter radiation intensity can be measured for different row sections (see Figure 2).
For this purpose~ use can be made of, for example~ rod-shaped scintillators comprising pho-tomul-tipliers which are arranged at the ends o~ the rod, the outpu-t signals of said photomultipliers being processed in accordance with the Anger camera principle. The longitudinal direct-5 8 ~) PHD 80-097 11 18.3.1981 ion of the rod should be parallel to the slit-shaped aperture 8 or perpendicular to the primary beam 3c A ~urther radiation source 1~ for -the emission o~ primary radiation with at least three dif~erent radiation energies is shown in ~igure 4. The radiation source 1~ comprises three radiation sources 18a-c which emit gamma rays, ~or example, one o~ 137Cs (o.66 Me~), 203Hg (0-28 MeV) and 57~o(0.12 ~e~). The three separate radiations sources 18a-c are situated, for example, inside a rotating disk 19 which has a radial duct 20 to the radiation exit ~or each separate radiation source.
The disk 19 rotates about a sha~t 21 at the correct angular velocity, so that the separate radiation sources 18a-c are successively positioned in ~ront of an exit opening 22 o~ a housing 23 which shields the radiation.
The primary radiation beam 24 each time passing through the exit aperture 22 is collimated by means of a diaphragm 25. The electronic circuit 11 then comprises three circuits 12 which ~orm energy windows, ~or example, pulse amplitude analyzers, which are adapted to the radiation energies o~ the separate radiation sources 18a-c.
Ob~iously, the separate radiation sources 18a-c can also be arranged or displaced with respect to the radiation exit aperture in another manner, ~or example, linearly. For the ~urther radiation source use can alternatlvely be made o~ a mixture o~ said three su~stances emitting gamma rays, said mixture being arranged in the rotating disk 19 at the area o~ one o~
the radiation sources 18a-c.
The invention relates to a diagnostic appara-tus for determining structures in a body, comprising a-t least one radiation source for generating a primary radia-tion beam of small cross-section which penetrates the body and which has at least three different radiat-ion energies~ at least one slit diaphragm which is situated outside the primary beam path and which com-prises a slit~shaped aperture which extends in a direct-ion approximately transversely of the primary radiation beam, a detector device which extends transversely of the longitudinal direction o* the slit and which com-prises separate detectors for the detection of scatter radiation which is produced in the body by the primary beam and which passes -through the slit-shaped aperture, and also comprising an electronic device for the pro-cessing and display of detector signals~
An apparatus of this kind is known from German Offenlegungsschrift 27 13 581. However, such an apparatus is suitable only for direc-tq~itative reproduction o~, ~0 for example, layer images of a three-dirnensional body if no additional correction steps are per~ormed For example, if the attenuation o~ the radiation along the pa-th ~ollowed by the primary beam or the scatter radiat-ion is also -to be taken into account, the measurement values obtained by means of the apparatus must be correct-ed in accordance with the correction methods which are also known from German Offenlegungsschrift 27 13 581, thus necessitating the use of a digital computer.
For the correction of the measurement of a slice of a body it is assumed, for example, that first aline in the bod~ slice is scanned whose scatter radiation reaches the ~etector device wi-thout attenuation by inter-... .
PHD 80.097 2 18.3.1981 mediate tissue. The scatter radiation emitted by thefirst cell of this line has not yet been attenuated, so it can be used directly as a measure for the density in this cell. Primary radiation reaching the second cell of this line has been attenuated by the energy converted into sca-tter radiation in the first cell and because this energy is known from the measurement of the first cell~ it can be taken into account by way of a corres-ponding increase of an output signal of the detec-tor associated with the second cell in comparison with the output signal of the detector associated with the first cell. Similarly?for a third cell of this line9 the atten-uation by the firsttwo cells must be taken into account, etc. For a first cell of a next line, the primary beam has not been attenuated either~ but the scatter radiat-ion from this cell is attenuated by the cells of tha preceding line which are situated between the slit and the relevant cell. Because the attenuation of -the radiat-ion by these cells, however~ has already been determined during the previous measurement~ the measurement ~alue associated with the first cell o~ the second line can be corrected accordingly. For the output signal of the de-tector which measures the scatter radiation produced in the second cell of the second line it is necessary to ta~e into accOunt on the one hand an attenuation of the primary beam by the first cell of this line and on the other hand the attenuation of the scatter radiation by the cells of adjacent lines.
Thus, this correction method enables completely corrected imaging of internal regions of body slices only if the outer regions of the body slice to be imaged are also ir~adiated. Furthermor0, if this correction methodsw~re used, only be the scatter radiation gen0rated in the body by the primary beam and extending substant~
ially in the plane of the body slice to be imaged should be measured, because then the corresponding attenuation coefficients for -the individual pixels of -the layer s ~ ~
PHD 80.097 3 18.3.1981 image will not be disturbed by any regions exhibiting strong absorption (bones, gas inclusions etc.) which are situated outside the body slice to be imaged.
It is an object of the invention to provide a Compton scatter diagnostic apparatus for the determinat-ion of the structure of a body which simply enables the ~ormation of improved layer images without using such a correction method.
This object is achieved in accordance ~ith the invention in that each detector supplies detector output signals which are dependent on the energy o~ the incident radiation and is connected to an electronic circuit for the ~ormation of scatter detector signals from the dif~erent primary radiation energies, the apparatus furthermore comprising an electronic memory for the storage of reference scatter signals which have been recorded ~or a known reference body by means of a similar diagnostic apparatus and in the same manner, said electronic memory being connec-ted to the electronic pro-cessing device which is adapted to perform a comparison of the scatter signals and the re~erence scatter signals at different radiation energies and to determine the internal structure of the body from the scatter signals and the reference scatter signals thus compared.
As has already been stated) the scatter signals ~S) and re~erence scatter signals (V) (radiation intensi-tie~) measured in a part of the body irradiated by the primary beam at a radiation energy are dependent on the electron density in the body region, on the attenuation of the primary radiation in the body preceding this body region, and on the attenuation of the scatter radiation in the body. These three variables are unknown ~uantities. When the scatter signals are compared with the reference scatter signals previously recorded for a known reference body, for example, by forming the quo-tient of the scatter signal and the reference scatter signal and therefrom the logarithm (1n(S/V~), the three -` ~ 3 645~V
PHD 80.097 ~ 18.3.1981 unknown varia'bles can be determined therefrom if the procedure is performed each time for a body point with at least three different radiation energies. The corres-ponding variables for the reference body are known. The comparison of a scat-ter signal with a reference scatter signal, however, should always be performed for -the same radiation energy. This ena'bles a simple determination of, for exarnple, the electron density distribution in the body region irradia-ted by the primary beam and hence the reproduction of, for example, layer images of' the body if this procedure is executed for a large number of, ~or e~ample, parallel beam paths situated in the plane of` the slice.
These layer images need no longer be corrected as regards the attenuation of the primary radiation or scatter radiation, Notably the reproduction of high-quality layer images of parts which are situated inside a body slice is thus also possible, without the nccessi-ty, i.e. to measure the total cross-section of the body.
Obviously9 layer images of a body which are not situated in one plane can also be formed.
It is also advantageous that~ for e~ample, variables such as the sensitivity of the detectors, the enargy dependency of the multiple scattering in the bo~y etc. no longer influence the quality of the re-constructed body slice or body structure. During the comparison of the scatter signals and the reference scatter signals these variables cancel one another if the body and the reference body have been measured by means of the same scatter diagnostic apparatus and in the same manner, i~e. if they have been irradiated with the same primary radiation. The body and the reference body should resemble one another as much as possible.
In a pref'erred embodiment in accordance with the invention, the radiation source consists of an X-ray source or of at least three substances emitting gamma rays of different energies.
o PHD 80.097 5 18.3.1981 It is thus achieved that the radiation of` at least three different radiation energies becomes simply available.
In a further embodiment in accordance with the invention, the detector device comprises several de-tectors each time in a row which extends through a de-tector and parallel to the principal direction of the slit-shaped aperture.
The scatter radiation each time measured by a detector on a line (detector row) is then us0d for the determination of the internal body structure, for example, the electron density of the bod~ substance at the corresponding body region which emits the scatter radiation. Subsequently, the electron densities thus obtained are averaged. For example, strongly absorbing body structures between the activated body region and the detectors can then be localized and taken into accourlt in that 9 for example, the electron densities associated with the corresponding detectors are suitably weighted for the averaging. The reconstruction accuracy can be improved by such a detector device. The image quality is additionally improved because a larger number of the scatter photons emitted by the scatter centre are measured. Because the ]ine-shaped detector described in DE 27 13 581 does not have local resolution in the line direction, it is not suitable for the re-construction of highly absorbing body struc-tures (bones, air inclusions~ etc.) which are situated between the activated body region and the detector device~ so that these structures cannot be taken into account~ with the result that the electron density in the activated body region is not properly reproduced.
The drawing shows embodiments in accordance with the invention.
Figure 1 is a sectional view of the diagnostic apparatus in accordance with the invention, Figure 2 shows a block diagram for the pro-5 ~ (~
PHD 80.0~7 6 18.3.1981 cessing of' the detector output signals of each time one detector, Figure 3 is a perspective view of the diagnos-tic apparatus, and Figure L~ shows a radiation source device com-prising three separate radiation sources of dif~erent radia-tion energies~
Eigure 1 is a sectional view of a diagnostic apparatus in accordance with the invention. It comprises~
for example, an X-ray source 1 whose polychromatic radiation is stopped down by means of a diaphragm 2 in order to form a primary beam 3 of small cross-section which irradiates a body 5 positioned on a table 4~ The primary beam 3 follows a primary beam path def`ined by lS this beam. The scatter radiation 6, 6~ produced in the region of the body 5 irradiated by the primary beam 3 reaches a detector device 9, 9~ each time via a sli-t diaphragm 7~ 7~ which is arranged on the opposite sides of the primary beam 3 and whose slit-shaped apertures 8, 8~ whose width is preferably adjustable extend per-pendicularly to the primary beam 3. The detector devices 9, 9~ consist of separate detectors 10, 10~ which are juxtaposed in a straight line which e~tends parallel to the primary beam 3. The detectors 10, 10l may be~ for example, strip-shaped and be arranged so that their principal dimension extends pa~allel to the slit-shaped apertures 8, 8'. ~or the scanning o~ diff'erent regions of the body, the body 5 and the diagnostic apparatus are arranged to be movable with respect to each other.
Each detector of the de-tector devices 9, 9 t supplies detector signals I(E) which are dependent on the energy E of the scatter radiation incident thereon.
The energy E o~ the scatter radiation is determiIled f'or a given energy E of the primary radia-tion and for a given scatter angle ~ at which the scatter radia-tion is scattered with respect to the primary beam 3 in accOr-dance with the generally known Compton equationO The 8 ~
, . ~ , PH~ 80.o97 7 18.3.1981 position of the slit diaphragms 7 t 7~ de~ines the angles e at which the scatter racliation is measured ~or any point on the primary beam 3. The energy-dependency o~ the scatter radlation, there~ore, is determined only by the energy-dependency of the primary radiation.
Figure 2 shows a block diagram for the pro-cessing of the de-tector output signals. A detector, for example~ the detector 10, is each time connected to an electronic circuit 11 which records scatter photons at only three different energies, that is to say I(E1), I(E2) and I(E3), on the basis o~ the scatter photons of di~ferent energy which arrive at the detector 10 and which are generated on the basis of the polychromatic X-rays. Scatter signals S(E1), S(E2), S(E3) are then form-ed from the de-tector output signals each time associated with one of the scatter radiation energies E1, E2, E3.
To this end, the electronic circuit 11 may comprise, for examplé, three circuits 12 which ~orm energy windows and which produce an output signal only if the input ~0 signal ~detector output signal) is within a given range which corresponds to a predetermined energy range of th~ scatter radiation. The output signals of the circuits 12 each time associated with an energy range are then added in order to produce the scatter signals S(E1), S(E2), S(E3); this operation can also be per~ormed in the electronic circuit 11.
A scatter signal recorded ~y means of a de-tector can be represented as follows:
S(El)~ N(E) ~ Yk [exp -~ /u(E1~ l1)dll~ .
[exp - f/u(E1, 12) dl2] (1) This formule (1) is applicable to all energies E1, E2~
E3 etc. As has already been stated, S(E1) is the intensi-ty of the scatter radiation with the energy E1, N(E1) being the intensity of the primary radiation outside the ``--` ~ 3 ~580 PHD 800097 8 18.3.1981 body 5 with the energy E1, d ~(EI)/d Q being the differential effective cross-section for the scatt~ring of the primary radiation, ~k being -the electron density o~ the body 5 in the body point P considered (see Figure 1), the rourth term being the at-tenuation of the primary beam 3 between the radiation source 1 and the relevan-t body point P (path l1), the ~ifth term being the attenuation of the scatter radiation be-tween the body point P and the detector measuring the scatter radiation (path 12).
In the case of biological material, for energies in excess of 100 KeV mainly the scattering con-tributes to the attenuation coefficient /u (see formule 1), so that i-t can be expressed as follows: , /u (E,l) = ~(E) . y(l) (2) Therein, ~(E) is the overall Klein-Nishina effective scatter cross-section and ~(l) is the location-dependent electron density.
After application of the formule (2) to -the ~ormule (1), the scatter signals S(E1), S(E2), S(E3) are applied to an electronic computer 13 whereto the electro-nic circuit 11 is electrically connected and which f'orms part of the electronic processing device 14. ~lso con-nected to the electronic computer 13 is an electronic memory 15 which stores re~erence scatter signals V(E1) 9 V(E2), V(E3) which corr0spond to the scatter signals S(E1), S(E2), S(E3) and which have bcen recorded under the same circumstances as the latter signals, that is to say with the same radiation energies E1, E2, E3, for a known reference body which corresponds to the body to be examined and by means o~ the same diagnostic apparatus.
The reference body (not shown) may be, for example, a water phantom.
The comparison between scatter signals and reference scatter signals in the computer 13 is executed so that each time for an energy E1, E2~ E3 the quotient S(E1)/V(El2) etc. of a scatter signal and a re~erence 5 8 ~
PHD 80.097 9 18.3.1981 scatter signal is formed and the logarithm -thereof is formed. Thus, a set of three formules with three un-knowns is obtained. The formule for the scatter radiation having the energy E1 is as follows:
ln ~ = ln ~ - ~(E1)~fk(11) - ~V(11)~ dl1 - ~(E1)~
[~k(l2) yv(12)~cl12 (3) Similar formules apply to E2 and E3. The index k denotes the body 5 to be examined, ~hilst the index ~ denotes reference bodyG
From the set of formules 3 (formules ~or El~ E2, E3) the elec-tron clensity ~k can thus be determined each time for a body point P irradia-ted by the primary beam 3.
'~he electron densities y~ (11) and ~V(12) of the reference body on the path 11 of the primary beam and the path 12 of the scatter radiation, respectively, are known, so also the Klein-Nishina effecti~e scatter cross-sections ~(E1), ~(E1) (similar for the energies E29 E3). As has already been stated, the energy of the scatter radiation E1 can be calculated from the energy E1 of the primary radiation via the Compton ~ormule. Obviously, photons can also be detected at more than three radiation energies.
The electronic circuit 11 would re~uire only more cir-cuits 12 (or additional channels of a multiple channel) for this purpose. 'rhe set of` ~ormules thus obtained would subsequently be suitably minimized.
A detector 10, 101 is thus each time connected to an electronic circuit 11, only one o~ which is shown in Figure 2, all said circuits 11 being connected to the same computer 13. The memory 15 also contains the refer~
en¢e scatter signals f`or all points on the primary beam 3 passing through the reference body. The electron densi-ties ~k determined by the computer 13, or the ~ariablesderi~ed therefrom, can be displayed on a moni-tor 16 or be stored in a bulk memory 17 (magnetic tape~ memory disk ~l~9~
PHD 80.097 10 18.3~1981 or similar).
Figure 3 is a perspec-tive view of the scatter diagnostic apparatus in accordance with the invention.
The slit diaphragm 7 has an elonga-te slit-shaped aper-ture 8 9 90 -that a scatter radiation beam 6 having a very large angle o~ aperture ~ which starts from the body point P is activated by the primary radiation beam 3.
The scatter radiation beam 6 reaches a detector row which consists of separte detectors 10a, b etc~ which are situated in a row which extends parallel to the slit-shaped aperture 8 which ex-tends perpendicularly to the primary beam 3. In an extreme case, -the complete detec-tor device 9 or the slit diaphragm 7 can alternatively completely enclose the primary beam, for example, in a lS cylindrical manner, so tha-t the primary beam 3 extends along the cylinder axis. ~ach ~eparatedetector of the de-tector device 9 (shaped as a cylinder or a two-dimensional detector matrix) is then connected to its own electronic circuit 11 (not shown~ via the connec-tions a-d~ etc. ~
variable, f`or example 9 the electron density k which cha-racterizes the internal structure of the body 5 can then each time be derived by means of a detector of the de-tector device. The electron densities of each detector row then relate to the same body point P. An improved electron density at the body point P can be determined from these densitiesa for e~ample~ ~y weighted av0raging .
Ob~iously, the detectors 10a, b etc. o~ a de-tector row can also be replaced by a single, rod-shaped detector which has a local resolution in the direction of the row, so that the scatter radiation intensity can be measured for different row sections (see Figure 2).
For this purpose~ use can be made of, for example~ rod-shaped scintillators comprising pho-tomul-tipliers which are arranged at the ends o~ the rod, the outpu-t signals of said photomultipliers being processed in accordance with the Anger camera principle. The longitudinal direct-5 8 ~) PHD 80-097 11 18.3.1981 ion of the rod should be parallel to the slit-shaped aperture 8 or perpendicular to the primary beam 3c A ~urther radiation source 1~ for -the emission o~ primary radiation with at least three dif~erent radiation energies is shown in ~igure 4. The radiation source 1~ comprises three radiation sources 18a-c which emit gamma rays, ~or example, one o~ 137Cs (o.66 Me~), 203Hg (0-28 MeV) and 57~o(0.12 ~e~). The three separate radiations sources 18a-c are situated, for example, inside a rotating disk 19 which has a radial duct 20 to the radiation exit ~or each separate radiation source.
The disk 19 rotates about a sha~t 21 at the correct angular velocity, so that the separate radiation sources 18a-c are successively positioned in ~ront of an exit opening 22 o~ a housing 23 which shields the radiation.
The primary radiation beam 24 each time passing through the exit aperture 22 is collimated by means of a diaphragm 25. The electronic circuit 11 then comprises three circuits 12 which ~orm energy windows, ~or example, pulse amplitude analyzers, which are adapted to the radiation energies o~ the separate radiation sources 18a-c.
Ob~iously, the separate radiation sources 18a-c can also be arranged or displaced with respect to the radiation exit aperture in another manner, ~or example, linearly. For the ~urther radiation source use can alternatlvely be made o~ a mixture o~ said three su~stances emitting gamma rays, said mixture being arranged in the rotating disk 19 at the area o~ one o~
the radiation sources 18a-c.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A diagnostic apparatus for determining struc-tures in a body, comprising at least one radiation source for generating a primary radiation beam of small cross-section which penetrates the body and which has at least three different radiation energies, at least one slit diaphragm which is situated outside the primary radiation beam path and which comprises a slit shaped aperture which extends in a direction approximately transversely of the primary radiation beam, a detector device which extends transversely of the longitudinal direction of the slit and which comprises separate detectors for the detection of scatter radiation which is produced in the body by the primary beam and which passes through the slit-shaped aperture, and also comprising an electronic device for the processing and display of detector signals, characterized in that each detector supplies detector output signals which are dependent on the energy of the incident radiation and is connected to an electronic circuit for the formation of scatter detector signals from the different primary radiation energies, the appa-ratus furthermore comprising an electronic memory for the storage of reference scatter signals which have been recorded for a known reference body by means of a similar diagnostic apparatus and in the same manner, said electro-nic memory being connected to the electronic processing device which is adapted to perform a comparison of the scatter signals and the reference scatter signals at different radiation energies and to determine the in-ternal structure of the body from the scatter signals and the reference scatter signals thus compared.
2. An apparatus as claimed in Claim 1, character-ized in that the radiation source is an X-ray source.
3. An apparatus as claimed in Claim 1, character-ized in that the radiation source comprises at least three substances which emit gamma rays of different ener-gies.
4. An apparatus as claimed in Claim 3, character-ized in that three substances emitting gamma rays are separately accommodated and can be successively positioned in front of a collimator device for the stopping down of a primary beam.
5. An apparatus as claimed in Claim 3 or 4, char-acterized in that the substances emitting gamma rays are 137Cs (0.66 MeV), 203Hg(0.28 MeV) and 57Co(0.12 MeV).
6. An apparatus as claimed in Claim 1, character-ized in that the detector device comprises several detec-tors each time in a row extending through a detector and parallel to the long direction of the slit shaped aper-ture.
7. An apparatus as claimed in Claim 1, character-ized in that the detectors comprise rod-shaped scintil-lators with photomultipliers which are arranged on the extremities of the rod, the longitudinal direction of the rod extending parallel to the long direction of the slid-shaped aperture.
8. An apparatus as claimed in Claim 1, 6 or 7, characterized in that the slit diaphragm and the detector device cylindrically surround the primary beam, the prim-ary beam following the cylinder axis.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3031949.4 | 1980-08-25 | ||
| DE19803031949 DE3031949A1 (en) | 1980-08-25 | 1980-08-25 | SCREEN EXAMINATION ARRANGEMENT FOR DETERMINING THE INNER STRUCTURE OF A BODY |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1164580A true CA1164580A (en) | 1984-03-27 |
Family
ID=6110312
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000384328A Expired CA1164580A (en) | 1980-08-25 | 1981-08-20 | Compton scatter diagnostic apparatus for determining structures in a body |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5772049A (en) |
| CA (1) | CA1164580A (en) |
| DE (1) | DE3031949A1 (en) |
| FR (1) | FR2488995B1 (en) |
| GB (1) | GB2082873B (en) |
| SE (1) | SE8104960L (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0640077B2 (en) * | 1983-10-12 | 1994-05-25 | 松下電器産業株式会社 | Radiation image receiving method |
| FR2565022A1 (en) * | 1984-05-23 | 1985-11-29 | Ephrati James | Device for multipoint emission of penetrating radiation |
| CA1280224C (en) * | 1987-08-27 | 1991-02-12 | Daniel Gagnon | Method and circuit for processing narrow band signals located in a wide band having disturbance |
| US5933473A (en) * | 1996-04-04 | 1999-08-03 | Hitachi, Ltd. | Non-destructive inspection apparatus and inspection system using it |
| US8837677B2 (en) | 2007-04-11 | 2014-09-16 | The Invention Science Fund I Llc | Method and system for compton scattered X-ray depth visualization, imaging, or information provider |
| JP6299033B2 (en) * | 2014-05-12 | 2018-03-28 | 一般財団法人電力中央研究所 | Nondestructive inspection method and apparatus |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3974386A (en) * | 1974-07-12 | 1976-08-10 | Wisconsin Alumni Research Foundation | Differential X-ray method and apparatus |
| DE2544354A1 (en) * | 1975-10-03 | 1977-04-14 | Siemens Ag | METHOD OF DETERMINING THE DENSITY OF BODIES BY MEANS OF PENETRATING RAYS AND EQUIPMENT FOR ITS IMPLEMENTATION |
| DE2713581C2 (en) * | 1977-03-28 | 1983-04-14 | Philips Patentverwaltung Gmbh, 2000 Hamburg | Arrangement for the representation of a plane of a body with gamma or X-rays |
| DE2944147A1 (en) * | 1979-11-02 | 1981-05-14 | Philips Patentverwaltung Gmbh, 2000 Hamburg | ARRANGEMENT FOR DETERMINING THE SPREAD DENSITY DISTRIBUTION IN A LEVEL EXAMINATION AREA |
| DE3023263C2 (en) * | 1980-06-21 | 1986-08-14 | Philips Patentverwaltung Gmbh, 2000 Hamburg | Arrangement for determining the internal structure of a body by means of monoenergetic radiation |
-
1980
- 1980-08-25 DE DE19803031949 patent/DE3031949A1/en not_active Ceased
-
1981
- 1981-08-20 CA CA000384328A patent/CA1164580A/en not_active Expired
- 1981-08-21 SE SE8104960A patent/SE8104960L/en not_active Application Discontinuation
- 1981-08-21 GB GB8125582A patent/GB2082873B/en not_active Expired
- 1981-08-22 JP JP56130869A patent/JPS5772049A/en active Pending
- 1981-08-24 FR FR8116151A patent/FR2488995B1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2488995A1 (en) | 1982-02-26 |
| JPS5772049A (en) | 1982-05-06 |
| FR2488995B1 (en) | 1985-06-14 |
| GB2082873B (en) | 1984-03-14 |
| DE3031949A1 (en) | 1982-04-01 |
| SE8104960L (en) | 1982-02-26 |
| GB2082873A (en) | 1982-03-10 |
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