CA1114074A - X-ray collimator, particularly for use in computerized axial tomography apparatus - Google Patents
X-ray collimator, particularly for use in computerized axial tomography apparatusInfo
- Publication number
- CA1114074A CA1114074A CA309,389A CA309389A CA1114074A CA 1114074 A CA1114074 A CA 1114074A CA 309389 A CA309389 A CA 309389A CA 1114074 A CA1114074 A CA 1114074A
- Authority
- CA
- Canada
- Prior art keywords
- radiation
- ray
- laminae
- swath
- source
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
- G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
- G21K1/02—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators
- G21K1/025—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators using multiple collimators, e.g. Bucky screens; other devices for eliminating undesired or dispersed 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
- A61B6/06—Diaphragms
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Abstract
ABSTRACT OF THE DISCLOSURE
An X-ray collimator for use in computerized axial tomography apparatus includes a plurality of substantially parallel X-ray absorbing laminae disposed in the plane of a wedge-shaped X-ray beam. The length and position of each lamina with respect to a divergent X-ray source is chosen to maximize the ratio of X-ray flux impinging upon a detector array to flux falling within the collimator's penumbra, outside the detector array.
An X-ray collimator for use in computerized axial tomography apparatus includes a plurality of substantially parallel X-ray absorbing laminae disposed in the plane of a wedge-shaped X-ray beam. The length and position of each lamina with respect to a divergent X-ray source is chosen to maximize the ratio of X-ray flux impinging upon a detector array to flux falling within the collimator's penumbra, outside the detector array.
Description
1~14074 This invention relates to X-ray collimators.
More particularly this invention relates to laminar X-ray collimation apparatus for producing wedge-shaped x-ray beams of adjustable thickness.
BACKGROUND OF THE INVENTION
Computerized apparatus for producing cross-section images of the body by the method of x-ray axial tomography are known, for example from United States Patent 3,788,614 issued December 11, 1973 and 3,866,047 issued February 11, 1975, both to Hounsfield. In one form of such apparatus a divergent beam of X-ray photons is directed from an X-ray source in a plane which passes through a body undergoing examination and there-after impinges on an array of X-ray detectors, which lie ~ , "
~- .
More particularly this invention relates to laminar X-ray collimation apparatus for producing wedge-shaped x-ray beams of adjustable thickness.
BACKGROUND OF THE INVENTION
Computerized apparatus for producing cross-section images of the body by the method of x-ray axial tomography are known, for example from United States Patent 3,788,614 issued December 11, 1973 and 3,866,047 issued February 11, 1975, both to Hounsfield. In one form of such apparatus a divergent beam of X-ray photons is directed from an X-ray source in a plane which passes through a body undergoing examination and there-after impinges on an array of X-ray detectors, which lie ~ , "
~- .
-2-MPHA 20,778 27-6-197~
in the plane of examination. The X-ray source and detec--~ tor array rotate (and in some embodirnents also translate) about the body to produce a series of one dimensional X-ray shadow-graphs which are combined in a digital com-5 puter, using well-known computational algorithms, to yield cross-section images of the examination plane.
Common X-ray sources, that is X-ray tube anodcs or radioisotope sources, generally produce X-ray beams which diverge through substantial solid angles. In com-10 puterized axial tomography (CAT) equipment mechanicalcollimation is generally utilized in conjunction with the X-ray source to limit the divergence of the X-ray beam to a wedge or fan-shaped swath which is confined to the examination plane and to the included angle of ; 15 the detector array. Unnecessary radiation dose to the patient and system noise from scattered X-ray photons is thereby re~uced The mechanical constraints of CAT equip-ment generally require thattsuch X-ray source collima-tors have minimum weight, to permit rapid motion, and 20 minimum length, to reduce the overall size of the ro-tating components and maximize the X-ray flux at the detector array.
Means are generally provided for adjusting the thickness of the X-ray beam, and thus the examination 25'plane, in CAT apparatus. In prior art collimators, which generally comprised one or more long channels through bodies of X-ray absorbing material, two sets of moveable jaws were generally utilized to control the thickness of the X-ray swath. Such multiple jaw sets were required to 30 limit the X-ray penumbra which would otherwise be pro-duced if a single set of jaws were utilized with an X-ray source of finite dimensions.
SUMMARY OF T~IE INVENTION
An X-ray collimator for producing a planar, 35 wedge-shal?ed swath of X-ray photons comprises a plurality - of substantially parallel X-ray absorbing laminae dis-posed in the plane of the X-ray beam and spaced one from ...~..~
, `-` 11~4~7dt the other. The extent and relative displacement of the laminae along the X-ray beam as well as the number of such laminae are determined to individual-ly maximize the ratio of X-ray flux within a defined beam thickness to X-ray flux outside the defined beam. X-ray photons at all points within the beam are generally confined to paths lying substantially parallel to the beam plane so that the beam thickness may be adjusted with a single set of moveable jaws with minimum X-ray flux in the penumbra. Collimators of the present invention are generally shorter and lighter than prior art, conventional collimators and are thus ideally suited for use in CAT
scanning apparatus.
It is therefore, an object of this invention to produce short, lightweight X-ray collimators for use in computerized axial tomography apparatus.
Another object of this invention is to allow adjustment of the thickness of a planar X-ray swath by means of a single set of moveable jaws.
Thus, in accordance with one broad aspect of the invention there is provided measurement apparatus for X-ray computerized axial tomography comprising, in combination:
a source of divergent X-ray radiation having a finite thickness;
an array of radiation detectors disposed to accept radiation in a substntially planar swath from said source, a beam path being defined by lines connecting points on said source with points on said array;
baffle means surrounding said beam path, along a limited portion of its length, having a perforation therein, which function to absorb radiation from said source which propagates outside of said beam path;
a plurality of planar radiation-absorbing laminae disposed in said perforation substantially parallel to the plane of said swath and spaced one from another;
one pair of moveable jaw means defining an elongate radiation transmitting slot parallel to said laminae therebetween, disposed across said swath between said laminae and said array, which function to absorb _ 3 radiation progagating outside said slot and thereby determine the thickness of said swath at said array; and ' means for moving said jaw means to adjust the thickness of said slot.
According to another broad aspect of the invention there is provided apparatus for producing a substantially planar swath of X-ray radiation, having adjustable thickness, along the width of a radiation detector array; comprising, in combination: a radiation source, a beam path being defined by lines connecting points on said source with points on said detector array; baffle means surrounding a limited portion of said path and defining a perforation thereon, which function to absorb radiation propagating outside of said path; a plurality of planar radiation-absorbing laminae disposed within said perforation substantially parallel to the plane of said swath; one pair of radiation absorbing jaws disposed between said laminae and said detector array which define an elongated slot parallel to said detector array and within said beam path; and means for moving said jaws to adjust the thickness of said slot.
BRIEF DESCRIPTION OF THE'DRAWINGS
!
The novel features believed to be characteristic of the present invention are set forth in the appended claims. The invention itself, together with further objects and advantages thereof, may be best understood by reference to the following de~ailed descriptions, taken in connection with the appended drawings in which:
~ Figure 1 schematically represents computerized axial tomography 'i apparatus which includes collimating components of the present invention;
Pigure 2 is a sectional view of a laminar collimator of the ( present invention;
,~ Figure 3 illustrates the design of a collimator; and Figure 4 is an enlarged sectional view of a portion of the collimator of Figure 2 illustrating the distribution of laminae therein.
i 30 DESCRIPTION OF THE'PREFER~ED'EMBODI~NTS
Figure 1 is an X-ray measurement system of the ....
111407~
, MP~I~.20.778 present inven-tion for use with computerized axial tomo-graphy apparatus. ~lectrons in an X-ray tube 10 impinge upon an anode 11 to produce a divergent X-ray beam 13 which emerges through a window 12. ~ collimator 14, more 5 particularly described bclow, is disposed in the X-ray beam 13 to procluce a planar, wedge-shaped exit beam 15.
The thickness of the wedge-shaped beam 15 is determined by the overall internal thickness o.f the collimator 14.
The collimator 14 further functions to confine photon 10 propagation i.n the beam 15 to directions substantially parallel to the plane of the X-ray beam. The exit beam 15 then passes through a sl.ot 16 between a set of paral-lel X-ray absorbing jaws 17 and 18 (which may comprise tungsten plates) which are adjustable via a gear drive 15 19 to produce a wedge-shaped X-ray beam 20 having an e~fective thickness determined by the width of the slot 16. The X-ray beam 20 is directed through a body 21 where it is selecti.vely absorbed by tissues of varying density to produce a one-dimensional shadow-graph image~ of X-ray 20 intensi.ties. X-ray photons emergi..ng from thc body 21 pass through a slot 22 between a second set of parallel, X-ray absorbing jaws 23 and 24 wh:ich are adjusted by a gear mechanism to the same spacing as were the jaws 17 and 18.
The jaws 23 and 2~1 function to absorb X-ray photons which 25 are scattered by the body 21 or by other objects in the beam path and thus reduce noise in the X-ray measurement data.
The X-ray beam emerging from the slot 22 then passes through an X-ray absorbing aperture plate 25, 30 where it :is separated into beams 26 of equal cross-sec-tion, width and angular spacing; which serves to define the spa.tial resolution of the measurement .system. The indi~idual beams 26 exiting the aperture plate 25 then pass through a detector collimator 27, which functions to 35 reject scattered radiation, and impi.nge on an X-ray de-tector array 28 which may comprise scintillation crystals or any other type of radiation detectors which are common-ly used in X-ray tomography apparatus.
.
-: .
~5--MPI~A.20,778 Although any type of X-ray tube or other radi-ation source may be used, the tube 10 is most advantage-ously a lightweight X-ray tube having a *ixed anodc 11 which is disposed at an angle to both the electron beam 5 and the perpendicular window 12 of the tube. The anode focal spot produced by an electron beam of generally cir-cular cross-section is thus projected as an ellipse in 'the plane of the window 13 and is ideally suited for pro-ducing a fan or wedge-shaped X-ray swath.
The source collimator 1LI (Figs. 1 and 2) comprises an open ended hollow housing shell 32 having side walls 33 which act as a baffle and are spaced to define the maximum thickness of the emergent X-ray beam 15 and di-vergent end walls 34 which serve to limit the divergence 15 of the beam 15 to the width detector array 28. The hous-ing shell 32 contains a plurality of substantially paral-lel~ X-ray absorbing laminae 30 which are supported with-in the housing and spaced one from the other in a plura-lity of slots on the interior surface of the end walls 34.
20 The length of each lamina 30 as well as its position within the housing and its spacing from adjacent laminae are fixed to maximize the ratio of X-ray flux emer~ing within the defined exit beam 15 to flux falling within a penumbra of that beam. This design is most effectively 25 achieved with a digital computer following an iterative proeédure which functions to maximize the ratio for each lamina.
Figs. 1 and 3 illustrate the design principl~s for the collimator 14. The width of the channel between 30 the walls 34 Or the collimator housing is found by con-necting the outermost ends at each side of the focal spot 41 with the corresponding outermost ends 44 of the detec-`, tor array 28; the position of the` collimator 14 being fixed by such constraints as the dimensions of the X-ray 35 tube window and available space in the scanning mecha-nism. The spacing between the laminae 30 is then assumed --- and the central line A-A of the focal spot is divided in-to a great number of equidistant points. Each point is .
. ~ .
4S~
.
MPH~.20,77 assumed to radiate X-rays in all directions within the plane containing the central line of the ~ocal spot and the detector. For each point the radiative flux RD reach-ing the detector is calculated. Then the flux RP in the 5 penumbra (i.e. the flux passing through the collimator but not reaching tlle detector) is also calculated.
N
RD
n = 0 R = N
RP
, n = 0 is maximized by selecting values for the length and posi-tion of each lamina.
10 ~s an example, collimators having equally spaced, symmetrically disposed laminae were optimally desi,gned for a system' wherein the beam originated at a 15 mm thick focal spot and terminated at a 20 mm thick detector ar-ray approximately 1.2 meters from the focal spot. The 15 collimator lay between 59.5 and 139.7 millimeters from the focal ~pot. Table I summari,~es the calculated per-'' formance of collimators containing various numbers oflaminae as compared to a conventional collimator with the same exterior dimensions TABLE I
Number of ~ % R~)/RP
Laminae RD RP (~'~/RP)o .. . .. . .... ... . .
0 100 % 100 %
89 /29 o/o 3 . 01 X
9 73 % 10 % 7 . 05X
2513 70 % L~. 1 %17. 29X
17 61~% 3.8 o/o 16. 1X
21 55 % O,9 /0 62X
In all cases the laminae 30 comprised 0.1 mm dep]eted uraniums foil. Tungstcn laminae are also suitable and 30 allow less expensive fabrication. The collimator housing may, for example, comprise brass plate. A Fortran langu-age computer program which is useful for calculating lninae COllflgUratiO:Lls i5 set furt~ in Ap~endix A to - . :
~114C~
~PIIA.20,778 enable oth.ers to more easily practice the i.nvention.
Fig. 4 is an enlarged section of a collimator of Fig. 2 showing the spacing and extent of the laminae 30A-30K. By way of example Table II sets forth the spac-5 ing X, the distance between the lower end of the laminaand the housi.ng 32 exi.t end, Y1 an.d the distance between *he top of the lami.na and the housing exit end Y2, for an optimal collimator comprising 21 equally spaced laminae for the source and detector spacing above which produces 10 a convergent beam from a 15 mm focal spot to an 8 mm de-tector, TABLE II
Lamina ~ X(in) Y1(in) y2(in) 30 A 0 0 2.955
in the plane of examination. The X-ray source and detec--~ tor array rotate (and in some embodirnents also translate) about the body to produce a series of one dimensional X-ray shadow-graphs which are combined in a digital com-5 puter, using well-known computational algorithms, to yield cross-section images of the examination plane.
Common X-ray sources, that is X-ray tube anodcs or radioisotope sources, generally produce X-ray beams which diverge through substantial solid angles. In com-10 puterized axial tomography (CAT) equipment mechanicalcollimation is generally utilized in conjunction with the X-ray source to limit the divergence of the X-ray beam to a wedge or fan-shaped swath which is confined to the examination plane and to the included angle of ; 15 the detector array. Unnecessary radiation dose to the patient and system noise from scattered X-ray photons is thereby re~uced The mechanical constraints of CAT equip-ment generally require thattsuch X-ray source collima-tors have minimum weight, to permit rapid motion, and 20 minimum length, to reduce the overall size of the ro-tating components and maximize the X-ray flux at the detector array.
Means are generally provided for adjusting the thickness of the X-ray beam, and thus the examination 25'plane, in CAT apparatus. In prior art collimators, which generally comprised one or more long channels through bodies of X-ray absorbing material, two sets of moveable jaws were generally utilized to control the thickness of the X-ray swath. Such multiple jaw sets were required to 30 limit the X-ray penumbra which would otherwise be pro-duced if a single set of jaws were utilized with an X-ray source of finite dimensions.
SUMMARY OF T~IE INVENTION
An X-ray collimator for producing a planar, 35 wedge-shal?ed swath of X-ray photons comprises a plurality - of substantially parallel X-ray absorbing laminae dis-posed in the plane of the X-ray beam and spaced one from ...~..~
, `-` 11~4~7dt the other. The extent and relative displacement of the laminae along the X-ray beam as well as the number of such laminae are determined to individual-ly maximize the ratio of X-ray flux within a defined beam thickness to X-ray flux outside the defined beam. X-ray photons at all points within the beam are generally confined to paths lying substantially parallel to the beam plane so that the beam thickness may be adjusted with a single set of moveable jaws with minimum X-ray flux in the penumbra. Collimators of the present invention are generally shorter and lighter than prior art, conventional collimators and are thus ideally suited for use in CAT
scanning apparatus.
It is therefore, an object of this invention to produce short, lightweight X-ray collimators for use in computerized axial tomography apparatus.
Another object of this invention is to allow adjustment of the thickness of a planar X-ray swath by means of a single set of moveable jaws.
Thus, in accordance with one broad aspect of the invention there is provided measurement apparatus for X-ray computerized axial tomography comprising, in combination:
a source of divergent X-ray radiation having a finite thickness;
an array of radiation detectors disposed to accept radiation in a substntially planar swath from said source, a beam path being defined by lines connecting points on said source with points on said array;
baffle means surrounding said beam path, along a limited portion of its length, having a perforation therein, which function to absorb radiation from said source which propagates outside of said beam path;
a plurality of planar radiation-absorbing laminae disposed in said perforation substantially parallel to the plane of said swath and spaced one from another;
one pair of moveable jaw means defining an elongate radiation transmitting slot parallel to said laminae therebetween, disposed across said swath between said laminae and said array, which function to absorb _ 3 radiation progagating outside said slot and thereby determine the thickness of said swath at said array; and ' means for moving said jaw means to adjust the thickness of said slot.
According to another broad aspect of the invention there is provided apparatus for producing a substantially planar swath of X-ray radiation, having adjustable thickness, along the width of a radiation detector array; comprising, in combination: a radiation source, a beam path being defined by lines connecting points on said source with points on said detector array; baffle means surrounding a limited portion of said path and defining a perforation thereon, which function to absorb radiation propagating outside of said path; a plurality of planar radiation-absorbing laminae disposed within said perforation substantially parallel to the plane of said swath; one pair of radiation absorbing jaws disposed between said laminae and said detector array which define an elongated slot parallel to said detector array and within said beam path; and means for moving said jaws to adjust the thickness of said slot.
BRIEF DESCRIPTION OF THE'DRAWINGS
!
The novel features believed to be characteristic of the present invention are set forth in the appended claims. The invention itself, together with further objects and advantages thereof, may be best understood by reference to the following de~ailed descriptions, taken in connection with the appended drawings in which:
~ Figure 1 schematically represents computerized axial tomography 'i apparatus which includes collimating components of the present invention;
Pigure 2 is a sectional view of a laminar collimator of the ( present invention;
,~ Figure 3 illustrates the design of a collimator; and Figure 4 is an enlarged sectional view of a portion of the collimator of Figure 2 illustrating the distribution of laminae therein.
i 30 DESCRIPTION OF THE'PREFER~ED'EMBODI~NTS
Figure 1 is an X-ray measurement system of the ....
111407~
, MP~I~.20.778 present inven-tion for use with computerized axial tomo-graphy apparatus. ~lectrons in an X-ray tube 10 impinge upon an anode 11 to produce a divergent X-ray beam 13 which emerges through a window 12. ~ collimator 14, more 5 particularly described bclow, is disposed in the X-ray beam 13 to procluce a planar, wedge-shaped exit beam 15.
The thickness of the wedge-shaped beam 15 is determined by the overall internal thickness o.f the collimator 14.
The collimator 14 further functions to confine photon 10 propagation i.n the beam 15 to directions substantially parallel to the plane of the X-ray beam. The exit beam 15 then passes through a sl.ot 16 between a set of paral-lel X-ray absorbing jaws 17 and 18 (which may comprise tungsten plates) which are adjustable via a gear drive 15 19 to produce a wedge-shaped X-ray beam 20 having an e~fective thickness determined by the width of the slot 16. The X-ray beam 20 is directed through a body 21 where it is selecti.vely absorbed by tissues of varying density to produce a one-dimensional shadow-graph image~ of X-ray 20 intensi.ties. X-ray photons emergi..ng from thc body 21 pass through a slot 22 between a second set of parallel, X-ray absorbing jaws 23 and 24 wh:ich are adjusted by a gear mechanism to the same spacing as were the jaws 17 and 18.
The jaws 23 and 2~1 function to absorb X-ray photons which 25 are scattered by the body 21 or by other objects in the beam path and thus reduce noise in the X-ray measurement data.
The X-ray beam emerging from the slot 22 then passes through an X-ray absorbing aperture plate 25, 30 where it :is separated into beams 26 of equal cross-sec-tion, width and angular spacing; which serves to define the spa.tial resolution of the measurement .system. The indi~idual beams 26 exiting the aperture plate 25 then pass through a detector collimator 27, which functions to 35 reject scattered radiation, and impi.nge on an X-ray de-tector array 28 which may comprise scintillation crystals or any other type of radiation detectors which are common-ly used in X-ray tomography apparatus.
.
-: .
~5--MPI~A.20,778 Although any type of X-ray tube or other radi-ation source may be used, the tube 10 is most advantage-ously a lightweight X-ray tube having a *ixed anodc 11 which is disposed at an angle to both the electron beam 5 and the perpendicular window 12 of the tube. The anode focal spot produced by an electron beam of generally cir-cular cross-section is thus projected as an ellipse in 'the plane of the window 13 and is ideally suited for pro-ducing a fan or wedge-shaped X-ray swath.
The source collimator 1LI (Figs. 1 and 2) comprises an open ended hollow housing shell 32 having side walls 33 which act as a baffle and are spaced to define the maximum thickness of the emergent X-ray beam 15 and di-vergent end walls 34 which serve to limit the divergence 15 of the beam 15 to the width detector array 28. The hous-ing shell 32 contains a plurality of substantially paral-lel~ X-ray absorbing laminae 30 which are supported with-in the housing and spaced one from the other in a plura-lity of slots on the interior surface of the end walls 34.
20 The length of each lamina 30 as well as its position within the housing and its spacing from adjacent laminae are fixed to maximize the ratio of X-ray flux emer~ing within the defined exit beam 15 to flux falling within a penumbra of that beam. This design is most effectively 25 achieved with a digital computer following an iterative proeédure which functions to maximize the ratio for each lamina.
Figs. 1 and 3 illustrate the design principl~s for the collimator 14. The width of the channel between 30 the walls 34 Or the collimator housing is found by con-necting the outermost ends at each side of the focal spot 41 with the corresponding outermost ends 44 of the detec-`, tor array 28; the position of the` collimator 14 being fixed by such constraints as the dimensions of the X-ray 35 tube window and available space in the scanning mecha-nism. The spacing between the laminae 30 is then assumed --- and the central line A-A of the focal spot is divided in-to a great number of equidistant points. Each point is .
. ~ .
4S~
.
MPH~.20,77 assumed to radiate X-rays in all directions within the plane containing the central line of the ~ocal spot and the detector. For each point the radiative flux RD reach-ing the detector is calculated. Then the flux RP in the 5 penumbra (i.e. the flux passing through the collimator but not reaching tlle detector) is also calculated.
N
RD
n = 0 R = N
RP
, n = 0 is maximized by selecting values for the length and posi-tion of each lamina.
10 ~s an example, collimators having equally spaced, symmetrically disposed laminae were optimally desi,gned for a system' wherein the beam originated at a 15 mm thick focal spot and terminated at a 20 mm thick detector ar-ray approximately 1.2 meters from the focal spot. The 15 collimator lay between 59.5 and 139.7 millimeters from the focal ~pot. Table I summari,~es the calculated per-'' formance of collimators containing various numbers oflaminae as compared to a conventional collimator with the same exterior dimensions TABLE I
Number of ~ % R~)/RP
Laminae RD RP (~'~/RP)o .. . .. . .... ... . .
0 100 % 100 %
89 /29 o/o 3 . 01 X
9 73 % 10 % 7 . 05X
2513 70 % L~. 1 %17. 29X
17 61~% 3.8 o/o 16. 1X
21 55 % O,9 /0 62X
In all cases the laminae 30 comprised 0.1 mm dep]eted uraniums foil. Tungstcn laminae are also suitable and 30 allow less expensive fabrication. The collimator housing may, for example, comprise brass plate. A Fortran langu-age computer program which is useful for calculating lninae COllflgUratiO:Lls i5 set furt~ in Ap~endix A to - . :
~114C~
~PIIA.20,778 enable oth.ers to more easily practice the i.nvention.
Fig. 4 is an enlarged section of a collimator of Fig. 2 showing the spacing and extent of the laminae 30A-30K. By way of example Table II sets forth the spac-5 ing X, the distance between the lower end of the laminaand the housi.ng 32 exi.t end, Y1 an.d the distance between *he top of the lami.na and the housing exit end Y2, for an optimal collimator comprising 21 equally spaced laminae for the source and detector spacing above which produces 10 a convergent beam from a 15 mm focal spot to an 8 mm de-tector, TABLE II
Lamina ~ X(in) Y1(in) y2(in) 30 A 0 0 2.955
3 B .,03 0 2.898 30 C .06 0.2l~2 2.15~
30 D .09 0.109 2.458 .. 30 E .12 0.00 2.955 30 F .15 0.00 1.902 3o G .18 0.00 - 2.167 3o H .21 0.00 2.955 30 I .24 ~ 0.00 2.955 3 J .27 0.00 2.898 30 K .30 0.00 o.606 ~ The present invention provi.des a low weight, short structure producing a wedge-shaped planar swath of X-rays used in computerized axial tomography apparatus.
X-ray photon flux in the beam emerging from the collima-tor is substantially parallel to the X-ray beam plane so ,30 that beam thickness may be effectively controlled with a single set of moveable jaws and minimal penumbra effects.
The i.nvention has been described in detail herein in accord with certain embodiments thereof, yet many modifications and changes therein may be effected bv , 35 those skilled i.n the art. Accordingly, it is intended by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention. .
.
.
.
.
~14~74 .
MPHA.20,778 APPENDIX A
0001 REAL HM(21), GM(21) 0002 R13AL PHMI (21,16), PHM2 (21, 16) 0003 REAL AD(3), AT(2) ooo4 CO~MON/A/AL2(16~, AL3(16), PH1(21,16),PH2(21, 16) H(21), G(21) 0005 COMMON/~s/RP, RPO, RD, RI)O
ooo6 COMMON/C/IIMX(21), CMX(21),PHMN1(21,16), PHMX2 (21,16) 0007 COMMON/D/DE,TO,RMX,RDMX, RPMX,DMP,N,HCL,X7,X4E13 0008 COMMON/E/X(16),D1(21),AL1(16),AL4(16),IM,I,H2,KM
0009 DATA DH,DC.H1,H2,H3/3,375,3.375, 59.5, 139.7,1193.8 0010 DATA HCL,XCL,X4,X /444.5(3.430835-7.5,10.
0011 DATA KM,LMX,IM,K/16, 5.1, 1/
0012 X6 = (E11 ~çXCL-X4~ (HCL-H1)/HCL
0013 X7 = (1-123~XCL-X43~(HCL-1-12)/HCL
0014 XS _ (XCL~H3-X8~11CL)/(H3-HCL) 0015 X3 =-X6 0016 X2 =-X7 0017 X1 =-X8 0018 X(1) = X
0019 100 AL1(K) - ATAN2((X7-X(K)), H2) 0020 AL2(K) = ATAN2((X8-X(K)),H3) 0021 IF(X(K),GT,XS)AL2(K) = ATAN2((XCL-X(K)),HCL) 0023 AL4(K) = ATAN2((X2-X(K)), H2) 0024 AL3(K)= ATAN2((X1-X(K)), H3) 0025 ~ IE(X(K).LT.-XS)AL3(K)=A'rAN2((-XCL-X(K)),HCL) 0027 RPO=RPO+AL1(K)-AL2(K)~AL3(K)-AL4(K) 0028 RDO=RDO~AL2(K)-AL3(K) 0029 K =K~1 0030 X(K)=X(K-1)-2.~FX4/15.
0031 IF(K.LE.KM;)GOT0100 0033 R=RDO/RPO
oo34 CALL DATE(AD) 0035 CALL TIME(AT) oo36 WRITE(69104)(AD(I),I=1.3)~(AT(i),I= 1,2) 0037 104 FORMAT(14HICOLLIMATOR 3A4, 3X,2A~
30 D .09 0.109 2.458 .. 30 E .12 0.00 2.955 30 F .15 0.00 1.902 3o G .18 0.00 - 2.167 3o H .21 0.00 2.955 30 I .24 ~ 0.00 2.955 3 J .27 0.00 2.898 30 K .30 0.00 o.606 ~ The present invention provi.des a low weight, short structure producing a wedge-shaped planar swath of X-rays used in computerized axial tomography apparatus.
X-ray photon flux in the beam emerging from the collima-tor is substantially parallel to the X-ray beam plane so ,30 that beam thickness may be effectively controlled with a single set of moveable jaws and minimal penumbra effects.
The i.nvention has been described in detail herein in accord with certain embodiments thereof, yet many modifications and changes therein may be effected bv , 35 those skilled i.n the art. Accordingly, it is intended by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention. .
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MPHA.20,778 APPENDIX A
0001 REAL HM(21), GM(21) 0002 R13AL PHMI (21,16), PHM2 (21, 16) 0003 REAL AD(3), AT(2) ooo4 CO~MON/A/AL2(16~, AL3(16), PH1(21,16),PH2(21, 16) H(21), G(21) 0005 COMMON/~s/RP, RPO, RD, RI)O
ooo6 COMMON/C/IIMX(21), CMX(21),PHMN1(21,16), PHMX2 (21,16) 0007 COMMON/D/DE,TO,RMX,RDMX, RPMX,DMP,N,HCL,X7,X4E13 0008 COMMON/E/X(16),D1(21),AL1(16),AL4(16),IM,I,H2,KM
0009 DATA DH,DC.H1,H2,H3/3,375,3.375, 59.5, 139.7,1193.8 0010 DATA HCL,XCL,X4,X /444.5(3.430835-7.5,10.
0011 DATA KM,LMX,IM,K/16, 5.1, 1/
0012 X6 = (E11 ~çXCL-X4~ (HCL-H1)/HCL
0013 X7 = (1-123~XCL-X43~(HCL-1-12)/HCL
0014 XS _ (XCL~H3-X8~11CL)/(H3-HCL) 0015 X3 =-X6 0016 X2 =-X7 0017 X1 =-X8 0018 X(1) = X
0019 100 AL1(K) - ATAN2((X7-X(K)), H2) 0020 AL2(K) = ATAN2((X8-X(K)),H3) 0021 IF(X(K),GT,XS)AL2(K) = ATAN2((XCL-X(K)),HCL) 0023 AL4(K) = ATAN2((X2-X(K)), H2) 0024 AL3(K)= ATAN2((X1-X(K)), H3) 0025 ~ IE(X(K).LT.-XS)AL3(K)=A'rAN2((-XCL-X(K)),HCL) 0027 RPO=RPO+AL1(K)-AL2(K)~AL3(K)-AL4(K) 0028 RDO=RDO~AL2(K)-AL3(K) 0029 K =K~1 0030 X(K)=X(K-1)-2.~FX4/15.
0031 IF(K.LE.KM;)GOT0100 0033 R=RDO/RPO
oo34 CALL DATE(AD) 0035 CALL TIME(AT) oo36 WRITE(69104)(AD(I),I=1.3)~(AT(i),I= 1,2) 0037 104 FORMAT(14HICOLLIMATOR 3A4, 3X,2A~
4~)74 ;
MPHA. 20,77s oo38 WRITE(6,10s) (AL1 (K) ,AL2(K),AL3(K),AL~I(K) ~K=l KMD,R,RDO,RPO
oo39 105 FoRMAT(16(1H 7X,4F11.7/)/1H 7X,3F11.7) oo40 TO=SFCNDS(1 o) 0041 GOT06sO
0042 345 CAIL Sl oo43 350 R=RD/RP
oo44 IF(R.LE.RMD COTOR370 oo46 RM=R
oo47 RDM=RD
oo4s RPM=RP
oo4g Do3s6 L=1, 1M
o95o HM(L) = lI(L) 1 GM(L) = G(L) 0052 D035s K=1, KM
oo53 PHM1(L,K)=PI-I1(L,K) oo54 355 PHM2(L,K) = PI-12 (L,K) oo55 356 CONTINUE
oo5~ 370 IF(G(1)+DG.GT.H2-H1-H(1))GOT0380 0058 G(I)=G(I)~DG
oo59 IE`(H(I) .EQ.O.)G(I)=O
0061 H(I+I)=~I(I) 0062 G( I+I ) =G( I ) ; oo63 IF(H(I).EQ.O)GOT0380 0065 GOT034s oo66 380 Do3s6 L=I, I+ 1 oo67 H(L)=HM(L) oo6s G(L)=GM(L) oo69 Do3ss K=1,KM
0070 PIIl (L,K)=PHM1(L,K) 0071 385 PH2(L,K)=PHM2(L,K) oo73 N=N~ 1 0074 IF(RM.LE.RMX)GOT0603 oo76 RMX=RM
oo77 XDMX=RDM
0078 RPMX=RPM
oo79 Do450 L=1, IM
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ill4~;)7~
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MPHA.20 ~ 778 0080 HMX(L)=HM(L) 0081 GMX(L)=GM(L~) 0082 Do42s K=1 ~ KM
oos3 PHMX1 (L,K)=PHM1 (L,K) oos4 425 PHMX2(L,K)=PHM2(L,K) ooss 450 CONTINUE
oos6 603 IF(RM.LT.RMO)DHP= DHP/2.
008s IF(RM.NE.RMo)GoTo6os 0090 IF(NP.GT. 1 )GoTo620 0092 NP=NP~ 1 oo93 605 IF(H(I)+DHP.GE.H2-H1)DHP=+ABS(DHP)/2.
oo 95 RMO =RM
oog6 IF(H(I)+DlIp.LE~o)DHp=-ABs(DHp)/2~
oog8 IF(H(I)+DHP.LT.O.OR.H(I)+DHP.GT.H2-H1)GOT0605 0100 IF(ABS(DHP).LTØ5)GOT0620 0102 610 H(I)=H(I)+DHP
0103 G(I)=-DG
0105 620 DlIP=DlI
o 1 o6 NP=O
0107 RM=O
0108 I=I+2 0109 H(I)=O
o11o IF(I+I.LE.IM)GOT0610 01 12 NN=NN+ 1 0113 I=O
0114 IF(NN.LE.2)GOT0620 0118 IF(IM.EQ. IMX)GOTO 9oo 0120 650 IM=IM+4 0121 RMX=O
0122 RMO=O
0 123 RM=O
0124 DD1=2~(AMINl (x7~x6) )/(IM- 1) 0125 D1 (1)-0 0126 H ( 1 ~ ~H2 -H 1 " 1114()'74 MPHA.20,778 0127 I=2 0128 DHP=D~I
0129 GoTo670 0130 660 D0800 I=3,IM,2 0131 DI(I)=DI(I-2)~DDl 0132 DI(I-1)=-DI(I) o133 H(I)=O
0~134 H(I-1)=~
0135 G(I)=O
0136 G(I-1)=G(I) 0137 ~70 D0700 K=1,KM
0138 PH1(I,K)=ATAN2((DI(I)-X(K)),(H2-G(I)-H(I))) 0139 PM1(I-1~K)=ATAN2((DI(I-1)-x(K))~(H2-G~ H(I-1))) 0140 PH2(I,K)=ATAN2((DI(I)-X(K)),(H2-G(I))) 0141 700 PH2(I-l,K)=ATAN2((DI(I-1)-X(K)),(lI2-G(I-1))) 0142 IF(I.EQ.2)GOT0660 0145 I=2 o1Ll6 GoTo345 -0147 900 CALL DATE(AD) ; 0148 CALL TIME(AT) 0149 WRITE(6,904)(AD(I),I=1,3)~(AT(I)~ 2) 0150 904 EoRMAT(/3X,3A4,3X,2A4) ' ~'' , .
' ~ 111~(~7~
MPHA.20,778 0002 REAL W1(21,2), W2(21,2),B(2,21) 0003 REAL C(2,21), D(2,21), E(2,21) ooo4 COMMON/A/AL2(16)~AL2(16),PH1(21,16),PH2(21,16) H(21), G(21) 0005 COM~ION/B/RP,RPO, RD,RDO
ooo6 COMMON/E/X(16),DI(21),AL1(16),AL4(16),IM,I,M3,KM
0007 160 K=1 0008 RP=RPO
0009 ` RD=RDO
0010 170 L=O
0011 L1=0 0012 L2=0 0013 180 IF(L.EQ.IM)GOT0190 0015 L=L+1 0016 IF(L.l'r.I.O~.L.GT.I-~1)GOT0182 0018 PIl1(L,K)=ATAN2((D1(I)-X(K),(H2-C(L)-~I(L))) 0019 PH2(L,K)=ATAN2((Dl(L)-X(K)~ 2-G(L))) 0020 182 IF(PH1(L,K).~Q.PH2(L,K))GOT0180 0022 IF(l'lll(L,K).GT.O)GOT0200 0024 L2=L2~1 0025 Wl(L2,2)=ABS(PH1(L,K) 0026 W2(L,2,2)=ABS(PH2(L,K) 0028 200 L1=Ll~l 0029 W1(L1,1)=P111(L,K) 0030 W2(L1.1)=PI12(L,K) 0032 190 HlO
0033 JF=Ll oo34 NU=l 0035 A1=1.570795 oo36 210 IF(M.EQ.JF)GOT0220 0038 L=O
0039 230 IF(L.EQ.JF)GOT0240 0041 L=L~1 oo4~ IF(W1(L,NU).GT.Al)GOT0230 :, , . , . . . - ~ . , :
~ 4074 M~'~IA . 2 0 . 778 l 27-6-l 978 ¦ ~ oo44 IF(M.EQ.O)GOT0250 oo46 IF(W1( L , NU ) . LF . B ( NU , M ) GOT0230 1 0048 250 Al=W1 (L~NU) oo49 A2=W2(L,NU) 0051 240 M=N+1 j 0052 B(NU,M)=A1 oo53 C(NU,M)=A2 oos4 A1=1.s7o7ss 0056 220 IF(NU.EQ.2)GOT0260 0058 M=0 NU=2 ; oo60 JF=L2 oo61 A1 = 1 . 570795 0062 L=O
oo63 IF(L2.EQ~o)GoTo2so ~ 0065 GOT0210 I oo66 260 M=JF
0067 L=1 ! oo6s 265 D(NU,L)=B(NU,M) oo69 E(NU,L)=C(NU,M) --0070 270 IF(M~EQ.1)GoTo2so 0072 M=H-1 IF(N(NU,M).GE.E(NU,L))GOT0275 L=L+1 0076 GoTo265 275 IF(G(NU,M) .LT.E(NU,L))E(NU,L)=C(NU,M) 0080 280 IF(NU.EQ. 1 )GOTO=~O
008~ NU= 1 0083 JF=L1 oos4 M2=L
008 5 IF (L1. NE.0) GOT02 60 0087 L=O
~ 0088 300 M-0 ( ~ ~ 0089 310 IF(M.EQ.L)GOT0335 MPHA.20,778 0091 M=M~1 0092 B(NU,M)=-E(NU~M) oog3 IF(Nu~EQ.l)B(Nu~M)=D(~u~M) 0095 C(NU,M)=-D(NU,M) oog6 IF(NU,EQ.l)C(NU,M)=E(NU,M) 0098 P=C(NU,M) 0099 IF(P.LT.A12(K)GOT0320 ~0!1 o 1 IF(P.GE.A11(K)GOT0310 0103 315 Q=AMIN1(All(K),B(NU,M)) o 1 ol~ RP=RP-(Q-P) 0106 320 IF(C(NU,M).LT.Al3(K))GOT0330 0108 325 Q=AMIN1(A12(K),B(NU,M)) 010g RD=RD-(Q-P) 0110 P=AL2(K) 0111 IF(B(Nu~M)~LT~Al2(K))GoTo31o 0114 330 P=AMAX1(Al4(K),C(NU,M)) 0115 Q=AMIN1(Al3(K)~B(Nu~M)) 0116 RP=RP--(Q-P) 0117 P=Al3(K) 01i8 IF(B(NU,M).LT~P)~OT0310 0121 335 IF(NU.NE.1)GOT0340 0123 NU=2 0124 L=M2 0125 ` M=O
0127 3l10 IF(K.EQ.KM)RETURN
0129 K=K+1 .
~ fl~
MPHA .20,778 0002 INTEGER IV(202) 0003 COMMON/C/IIMX(21) ,GMX(21) ,PHMX(21,16)PHMX2(21,16) ooo4 COMMON/D/DE,TO.RMX,RDMX,RPMX,DMP,N,IlCL,X7,X4,H3 0005 COMMON/E/X(16) ,DI(21) ,AL1 (16) ,AL4(16) ,IM,I,H2,KM
ooo6 600 FORMAT(//6F12.3/~;6F12.3)) 0007 601 FORMAT(3F12.3,3112) 0008 602 FORMAT(//2F12.3/(3214)) 0009 DE= ( SECNOS (1. O ) -TO ) /60.
0010 TO=SECNDS (1.0) 0011 WRITE(6.600)RMX,RDMX,RPMX, (HMX(L) ,GMX(L) ,DI(L), L=1,1M) 0012 WRITE(6,601)DE,DHP,RMX,IM,I,N
0013 U=HCL
0014 Do608 L=1,2 0015 XL= ( X7 -X4) /H27~U~X4 0016 XY=-1,01~XL
0017 Do646 J=1 ,201 0018 IV(J)=O
0019 XY=XY~XL/ 100 0020 Do644 K=1,KM
0021 ANC=ATAN2(XY-X(K) ) ,U) 0022 IF)ANG.GT.AL1 (K) .OR.ANG.LT.AL~i(K) )GoTo644 ooz4 Do642 I= 1, IM
0025 IF(ABS(ANG) .LT.ABS(Pl-IMX2(I,K) ) )GoTo642 0027 IF(ABS(ANG) .GT~ABS(PHMX1 (I,K) ) )GoTo642 0029 IF ( ANC~PHMX 1 ( I, K ) . GT .0) GoTo644 0032 IV(J)=IV(J)+
oo34 646 CONTINUE
0035 WRITE(6,602)U,XL, (IV(J),J=1 .201) oo36 648 U=B3 oo38 END
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MPHA. 20,77s oo38 WRITE(6,10s) (AL1 (K) ,AL2(K),AL3(K),AL~I(K) ~K=l KMD,R,RDO,RPO
oo39 105 FoRMAT(16(1H 7X,4F11.7/)/1H 7X,3F11.7) oo40 TO=SFCNDS(1 o) 0041 GOT06sO
0042 345 CAIL Sl oo43 350 R=RD/RP
oo44 IF(R.LE.RMD COTOR370 oo46 RM=R
oo47 RDM=RD
oo4s RPM=RP
oo4g Do3s6 L=1, 1M
o95o HM(L) = lI(L) 1 GM(L) = G(L) 0052 D035s K=1, KM
oo53 PHM1(L,K)=PI-I1(L,K) oo54 355 PHM2(L,K) = PI-12 (L,K) oo55 356 CONTINUE
oo5~ 370 IF(G(1)+DG.GT.H2-H1-H(1))GOT0380 0058 G(I)=G(I)~DG
oo59 IE`(H(I) .EQ.O.)G(I)=O
0061 H(I+I)=~I(I) 0062 G( I+I ) =G( I ) ; oo63 IF(H(I).EQ.O)GOT0380 0065 GOT034s oo66 380 Do3s6 L=I, I+ 1 oo67 H(L)=HM(L) oo6s G(L)=GM(L) oo69 Do3ss K=1,KM
0070 PIIl (L,K)=PHM1(L,K) 0071 385 PH2(L,K)=PHM2(L,K) oo73 N=N~ 1 0074 IF(RM.LE.RMX)GOT0603 oo76 RMX=RM
oo77 XDMX=RDM
0078 RPMX=RPM
oo79 Do450 L=1, IM
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ill4~;)7~
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MPHA.20 ~ 778 0080 HMX(L)=HM(L) 0081 GMX(L)=GM(L~) 0082 Do42s K=1 ~ KM
oos3 PHMX1 (L,K)=PHM1 (L,K) oos4 425 PHMX2(L,K)=PHM2(L,K) ooss 450 CONTINUE
oos6 603 IF(RM.LT.RMO)DHP= DHP/2.
008s IF(RM.NE.RMo)GoTo6os 0090 IF(NP.GT. 1 )GoTo620 0092 NP=NP~ 1 oo93 605 IF(H(I)+DHP.GE.H2-H1)DHP=+ABS(DHP)/2.
oo 95 RMO =RM
oog6 IF(H(I)+DlIp.LE~o)DHp=-ABs(DHp)/2~
oog8 IF(H(I)+DHP.LT.O.OR.H(I)+DHP.GT.H2-H1)GOT0605 0100 IF(ABS(DHP).LTØ5)GOT0620 0102 610 H(I)=H(I)+DHP
0103 G(I)=-DG
0105 620 DlIP=DlI
o 1 o6 NP=O
0107 RM=O
0108 I=I+2 0109 H(I)=O
o11o IF(I+I.LE.IM)GOT0610 01 12 NN=NN+ 1 0113 I=O
0114 IF(NN.LE.2)GOT0620 0118 IF(IM.EQ. IMX)GOTO 9oo 0120 650 IM=IM+4 0121 RMX=O
0122 RMO=O
0 123 RM=O
0124 DD1=2~(AMINl (x7~x6) )/(IM- 1) 0125 D1 (1)-0 0126 H ( 1 ~ ~H2 -H 1 " 1114()'74 MPHA.20,778 0127 I=2 0128 DHP=D~I
0129 GoTo670 0130 660 D0800 I=3,IM,2 0131 DI(I)=DI(I-2)~DDl 0132 DI(I-1)=-DI(I) o133 H(I)=O
0~134 H(I-1)=~
0135 G(I)=O
0136 G(I-1)=G(I) 0137 ~70 D0700 K=1,KM
0138 PH1(I,K)=ATAN2((DI(I)-X(K)),(H2-G(I)-H(I))) 0139 PM1(I-1~K)=ATAN2((DI(I-1)-x(K))~(H2-G~ H(I-1))) 0140 PH2(I,K)=ATAN2((DI(I)-X(K)),(H2-G(I))) 0141 700 PH2(I-l,K)=ATAN2((DI(I-1)-X(K)),(lI2-G(I-1))) 0142 IF(I.EQ.2)GOT0660 0145 I=2 o1Ll6 GoTo345 -0147 900 CALL DATE(AD) ; 0148 CALL TIME(AT) 0149 WRITE(6,904)(AD(I),I=1,3)~(AT(I)~ 2) 0150 904 EoRMAT(/3X,3A4,3X,2A4) ' ~'' , .
' ~ 111~(~7~
MPHA.20,778 0002 REAL W1(21,2), W2(21,2),B(2,21) 0003 REAL C(2,21), D(2,21), E(2,21) ooo4 COMMON/A/AL2(16)~AL2(16),PH1(21,16),PH2(21,16) H(21), G(21) 0005 COM~ION/B/RP,RPO, RD,RDO
ooo6 COMMON/E/X(16),DI(21),AL1(16),AL4(16),IM,I,M3,KM
0007 160 K=1 0008 RP=RPO
0009 ` RD=RDO
0010 170 L=O
0011 L1=0 0012 L2=0 0013 180 IF(L.EQ.IM)GOT0190 0015 L=L+1 0016 IF(L.l'r.I.O~.L.GT.I-~1)GOT0182 0018 PIl1(L,K)=ATAN2((D1(I)-X(K),(H2-C(L)-~I(L))) 0019 PH2(L,K)=ATAN2((Dl(L)-X(K)~ 2-G(L))) 0020 182 IF(PH1(L,K).~Q.PH2(L,K))GOT0180 0022 IF(l'lll(L,K).GT.O)GOT0200 0024 L2=L2~1 0025 Wl(L2,2)=ABS(PH1(L,K) 0026 W2(L,2,2)=ABS(PH2(L,K) 0028 200 L1=Ll~l 0029 W1(L1,1)=P111(L,K) 0030 W2(L1.1)=PI12(L,K) 0032 190 HlO
0033 JF=Ll oo34 NU=l 0035 A1=1.570795 oo36 210 IF(M.EQ.JF)GOT0220 0038 L=O
0039 230 IF(L.EQ.JF)GOT0240 0041 L=L~1 oo4~ IF(W1(L,NU).GT.Al)GOT0230 :, , . , . . . - ~ . , :
~ 4074 M~'~IA . 2 0 . 778 l 27-6-l 978 ¦ ~ oo44 IF(M.EQ.O)GOT0250 oo46 IF(W1( L , NU ) . LF . B ( NU , M ) GOT0230 1 0048 250 Al=W1 (L~NU) oo49 A2=W2(L,NU) 0051 240 M=N+1 j 0052 B(NU,M)=A1 oo53 C(NU,M)=A2 oos4 A1=1.s7o7ss 0056 220 IF(NU.EQ.2)GOT0260 0058 M=0 NU=2 ; oo60 JF=L2 oo61 A1 = 1 . 570795 0062 L=O
oo63 IF(L2.EQ~o)GoTo2so ~ 0065 GOT0210 I oo66 260 M=JF
0067 L=1 ! oo6s 265 D(NU,L)=B(NU,M) oo69 E(NU,L)=C(NU,M) --0070 270 IF(M~EQ.1)GoTo2so 0072 M=H-1 IF(N(NU,M).GE.E(NU,L))GOT0275 L=L+1 0076 GoTo265 275 IF(G(NU,M) .LT.E(NU,L))E(NU,L)=C(NU,M) 0080 280 IF(NU.EQ. 1 )GOTO=~O
008~ NU= 1 0083 JF=L1 oos4 M2=L
008 5 IF (L1. NE.0) GOT02 60 0087 L=O
~ 0088 300 M-0 ( ~ ~ 0089 310 IF(M.EQ.L)GOT0335 MPHA.20,778 0091 M=M~1 0092 B(NU,M)=-E(NU~M) oog3 IF(Nu~EQ.l)B(Nu~M)=D(~u~M) 0095 C(NU,M)=-D(NU,M) oog6 IF(NU,EQ.l)C(NU,M)=E(NU,M) 0098 P=C(NU,M) 0099 IF(P.LT.A12(K)GOT0320 ~0!1 o 1 IF(P.GE.A11(K)GOT0310 0103 315 Q=AMIN1(All(K),B(NU,M)) o 1 ol~ RP=RP-(Q-P) 0106 320 IF(C(NU,M).LT.Al3(K))GOT0330 0108 325 Q=AMIN1(A12(K),B(NU,M)) 010g RD=RD-(Q-P) 0110 P=AL2(K) 0111 IF(B(Nu~M)~LT~Al2(K))GoTo31o 0114 330 P=AMAX1(Al4(K),C(NU,M)) 0115 Q=AMIN1(Al3(K)~B(Nu~M)) 0116 RP=RP--(Q-P) 0117 P=Al3(K) 01i8 IF(B(NU,M).LT~P)~OT0310 0121 335 IF(NU.NE.1)GOT0340 0123 NU=2 0124 L=M2 0125 ` M=O
0127 3l10 IF(K.EQ.KM)RETURN
0129 K=K+1 .
~ fl~
MPHA .20,778 0002 INTEGER IV(202) 0003 COMMON/C/IIMX(21) ,GMX(21) ,PHMX(21,16)PHMX2(21,16) ooo4 COMMON/D/DE,TO.RMX,RDMX,RPMX,DMP,N,IlCL,X7,X4,H3 0005 COMMON/E/X(16) ,DI(21) ,AL1 (16) ,AL4(16) ,IM,I,H2,KM
ooo6 600 FORMAT(//6F12.3/~;6F12.3)) 0007 601 FORMAT(3F12.3,3112) 0008 602 FORMAT(//2F12.3/(3214)) 0009 DE= ( SECNOS (1. O ) -TO ) /60.
0010 TO=SECNDS (1.0) 0011 WRITE(6.600)RMX,RDMX,RPMX, (HMX(L) ,GMX(L) ,DI(L), L=1,1M) 0012 WRITE(6,601)DE,DHP,RMX,IM,I,N
0013 U=HCL
0014 Do608 L=1,2 0015 XL= ( X7 -X4) /H27~U~X4 0016 XY=-1,01~XL
0017 Do646 J=1 ,201 0018 IV(J)=O
0019 XY=XY~XL/ 100 0020 Do644 K=1,KM
0021 ANC=ATAN2(XY-X(K) ) ,U) 0022 IF)ANG.GT.AL1 (K) .OR.ANG.LT.AL~i(K) )GoTo644 ooz4 Do642 I= 1, IM
0025 IF(ABS(ANG) .LT.ABS(Pl-IMX2(I,K) ) )GoTo642 0027 IF(ABS(ANG) .GT~ABS(PHMX1 (I,K) ) )GoTo642 0029 IF ( ANC~PHMX 1 ( I, K ) . GT .0) GoTo644 0032 IV(J)=IV(J)+
oo34 646 CONTINUE
0035 WRITE(6,602)U,XL, (IV(J),J=1 .201) oo36 648 U=B3 oo38 END
.
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS
1. Measurement apparatus for X-ray computerized axial tomography comprising, in combination:
a source of divergent X-ray radiation having a finite thickness;
an array of radiation detectors disposed to accept radiation in a substantially planar swath from said source, a beam path being defined by lines connec-ting points on said source with points on said array;
baffle means surrounding said beam path, along a limited portion of its length, having a perforation therein, which function to absorb radiation from said source which propagates outside of said beam path;
a plurality of planar radiation-absorbing laminae disposed in said perforation substantially paral-lel to the plane of said swath and spaced one from an-other;
one pair of moveable jaw means defining an elongate radiation transmitting slot parallel to said laminae therebetween, disposed across said swath between said laminae and said array, which function to absorb radiation propagating outside said slot and thereby de-termine the thickness of said swath at said array; and means for moving said jaw means to adjust the thickness of said slot.
a source of divergent X-ray radiation having a finite thickness;
an array of radiation detectors disposed to accept radiation in a substantially planar swath from said source, a beam path being defined by lines connec-ting points on said source with points on said array;
baffle means surrounding said beam path, along a limited portion of its length, having a perforation therein, which function to absorb radiation from said source which propagates outside of said beam path;
a plurality of planar radiation-absorbing laminae disposed in said perforation substantially paral-lel to the plane of said swath and spaced one from an-other;
one pair of moveable jaw means defining an elongate radiation transmitting slot parallel to said laminae therebetween, disposed across said swath between said laminae and said array, which function to absorb radiation propagating outside said slot and thereby de-termine the thickness of said swath at said array; and means for moving said jaw means to adjust the thickness of said slot.
2. The apparatus of Claim 1, wherein the position and extent of each of said laminae along said beam path is optimized to maximize the ratio of the X-ray flux impinging on said detector array to the X-ray flux in a penumbra Or said baffle means.
3. The apparatus of Claim 2, wherein said laminae are equally spaced, one from another.
4. The apparatus of Claim 2, wherein said laminae comprise tungsten.
5. The apparatus of Claim 2, wherein said laminae comprise uranium.
6. The apparatus of Claim 2, wherein said baffle means comprise a brass housing which supports said laminae.
7. The apparatus of Claim 2, wherein said jaw means comprise tungsten plates.
8. Apparatus for producing a substantially planar swath of X-ray radiation, having adjustable thickness, along the width of a radiation detector array; comprising, in combination: a radiation source, a beam path being defined by lines connecting points on said source with points on said detector array; baffle means surrounding a limited portion of said path and defining a perforation thereon, which function to absorb radiation propagating outside of said path; a plurality of planar radiation-absorbing laminae disposed within said perforation substantially parallel to the plane of said swath; one pair of radiation absorbing jaws disposed between said laminae and said detector array which define an elongated slot parallel to said detector array and within said beam path;
and means for moving said jaws to adjust the thickness of said slot.
and means for moving said jaws to adjust the thickness of said slot.
9. The apparatus of Claim 8, wherein the position and extent of each lamina, along said path, is optimized to maximize the ratio of the radiation flux impinging on said detector array to the radiation flux within a penumbra of said baffle means.
10. The apparatus of Claim 9, wherein said laminae are equally spaced, one from another.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US825,590 | 1977-08-18 | ||
| US05/825,590 US4277684A (en) | 1977-08-18 | 1977-08-18 | X-Ray collimator, particularly for use in computerized axial tomography apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1114074A true CA1114074A (en) | 1981-12-08 |
Family
ID=25244399
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA309,389A Expired CA1114074A (en) | 1977-08-18 | 1978-08-15 | X-ray collimator, particularly for use in computerized axial tomography apparatus |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US4277684A (en) |
| JP (1) | JPS5443488A (en) |
| BE (1) | BE869762A (en) |
| CA (1) | CA1114074A (en) |
| DE (1) | DE2835583A1 (en) |
| FR (1) | FR2400717A1 (en) |
| GB (1) | GB2004448B (en) |
| IL (1) | IL55362A0 (en) |
| IT (1) | IT1098094B (en) |
| NL (1) | NL7808438A (en) |
Families Citing this family (37)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2932182A1 (en) * | 1979-08-08 | 1981-02-26 | Siemens Ag | LAYER DEVICE FOR PRODUCING TRANSVERSAL LAYER IMAGES |
| NL7906634A (en) * | 1979-09-05 | 1981-03-09 | Philips Nv | DEVICE FOR DETERMINING LOCAL ABSORPTION DIFFERENCES IN AN OBJECT. |
| US4361902A (en) * | 1980-07-07 | 1982-11-30 | General Electric Company | Collimator for x-ray diagnostic apparatus |
| FI67465C (en) * | 1981-04-24 | 1985-03-11 | Instrumentarium Oy | INSTALLATION FOER AOSTADKOMMANDE AV RADIOGRAFISKA SKIKTBILDER |
| DE3149723A1 (en) * | 1981-12-15 | 1983-07-21 | Siemens AG, 1000 Berlin und 8000 München | DENTAL X-RAY DIAGNOSTIC |
| US4466112A (en) * | 1982-01-29 | 1984-08-14 | Technicare Corporation | Variable detector aperture |
| US4472828A (en) * | 1982-07-23 | 1984-09-18 | Minnesota Mining And Manufacturing Company | X-Ray filter for chest X-rays |
| JPS5993510U (en) * | 1982-12-14 | 1984-06-25 | 株式会社日立メデイコ | X-ray flux aperture device |
| US4672648A (en) * | 1985-10-25 | 1987-06-09 | Picker International, Inc. | Apparatus and method for radiation attenuation |
| US4905268A (en) * | 1985-10-25 | 1990-02-27 | Picker International, Inc. | Adjustable off-focal aperture for x-ray tubes |
| US4872191A (en) * | 1987-11-19 | 1989-10-03 | Bio-Imaging Research, Inc. | Cam-controlled automatic dynamic focusing for computed tomography |
| US4910759A (en) * | 1988-05-03 | 1990-03-20 | University Of Delaware | Xray lens and collimator |
| US5239568A (en) * | 1990-10-29 | 1993-08-24 | Scinticor Incorporated | Radiation collimator system |
| US5418832A (en) * | 1993-11-05 | 1995-05-23 | Barnes; Gary T. | Scanning radiographic device with slit, slot and grid |
| US5563924A (en) * | 1994-02-04 | 1996-10-08 | Siemens Aktiengesellschaft | X-ray apparatus having an adjustable primary radiation diaphragm |
| GB2289983B (en) * | 1994-06-01 | 1996-10-16 | Simage Oy | Imaging devices,systems and methods |
| US6035013A (en) * | 1994-06-01 | 2000-03-07 | Simage O.Y. | Radiographic imaging devices, systems and methods |
| US5604353A (en) * | 1995-06-12 | 1997-02-18 | X-Ray Optical Systems, Inc. | Multiple-channel, total-reflection optic with controllable divergence |
| DE19741184A1 (en) | 1997-09-18 | 1999-03-25 | Basf Ag | Reducing residual monomer content of e.g. acrylic polymers |
| GB2341301B (en) * | 1998-08-28 | 2003-04-09 | Elekta Ab | Collimator for radiotherapy apparatus |
| IL130318A0 (en) * | 1999-06-06 | 2000-06-01 | Elgems Ltd | Pet and spect systems with attenuation correction |
| SE522484C2 (en) * | 2000-09-28 | 2004-02-10 | Xcounter Ab | Collimation of radiation from linear sources for ionizing radiation and related detection of flat beams |
| US6711235B2 (en) | 2002-05-31 | 2004-03-23 | General Electric Cormpany | X-ray inspection apparatus and method |
| US20040120464A1 (en) * | 2002-12-19 | 2004-06-24 | Hoffman David Michael | Cast collimators for CT detectors and methods of making same |
| US7343039B2 (en) * | 2003-06-13 | 2008-03-11 | Microsoft Corporation | System and process for generating representations of objects using a directional histogram model and matrix descriptor |
| US7683333B2 (en) * | 2004-10-15 | 2010-03-23 | Koninklijke Philips Electronics N.V. | Detector for nuclear medicine |
| US8242453B2 (en) * | 2004-10-15 | 2012-08-14 | Koninklijke Philips Electronics N.V. | Imaging system for nuclear medicine |
| DE102004058007B4 (en) * | 2004-12-01 | 2009-02-12 | Siemens Ag | X-ray computed tomography |
| CN100454039C (en) * | 2005-09-22 | 2009-01-21 | 同方威视技术股份有限公司 | Beam-guide-box structure integrated with ray source and front, rear collimator |
| ATE522908T1 (en) * | 2007-03-13 | 2011-09-15 | Koninkl Philips Electronics Nv | ADDITIONAL X-RAY COLLIMATOR FOR ASYMMETRIC BEAM COLLIMATION |
| US8385499B2 (en) * | 2009-12-28 | 2013-02-26 | General Electric Company | 2D reflector and collimator structure and method of manufacturing thereof |
| US9357973B2 (en) * | 2011-06-30 | 2016-06-07 | Koninklijke Philips N.V. | X-ray beam transmission profile shaper |
| GB201407826D0 (en) | 2014-05-02 | 2014-06-18 | Johnson Matthey Plc | Apparatus and method for scanning a structure |
| US10082473B2 (en) | 2015-07-07 | 2018-09-25 | General Electric Company | X-ray filtration |
| US20170143284A1 (en) * | 2015-11-25 | 2017-05-25 | Carestream Health, Inc. | Method to detect a retained surgical object |
| US11257653B2 (en) | 2020-03-27 | 2022-02-22 | The Boeing Company | Integrated aperture shield for x-ray tubes |
| US11169098B2 (en) * | 2020-04-02 | 2021-11-09 | The Boeing Company | System, method, and apparatus for x-ray backscatter inspection of parts |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2492031A (en) * | 1948-07-22 | 1949-12-20 | Ritter Co Inc | X-ray machine shutter control mechanism |
| US3428802A (en) * | 1966-04-11 | 1969-02-18 | Ibm | External standard method of x-ray diffraction analysis for determining the percentage of compounds in cement clinker |
| GB1462861A (en) * | 1973-02-24 | 1977-01-26 | Emi Ltd | Radiography |
| DE2548531A1 (en) * | 1975-06-30 | 1977-01-27 | Gary T Barnes | Radio diagnostic technique with improved picture contrast - using beam splitting slit screens above and below object |
| US4096389A (en) * | 1976-05-10 | 1978-06-20 | G. D. Searle & Co. | Apparatus for minimizing radiation exposure and improving resolution in radiation imaging devices |
| US4066901A (en) * | 1976-09-13 | 1978-01-03 | Varian Associates, Inc. | Tomographic scanning apparatus with improved collimator structure |
-
1977
- 1977-08-18 US US05/825,590 patent/US4277684A/en not_active Expired - Lifetime
-
1978
- 1978-08-14 DE DE19782835583 patent/DE2835583A1/en not_active Withdrawn
- 1978-08-15 IL IL7855362A patent/IL55362A0/en unknown
- 1978-08-15 GB GB7833344A patent/GB2004448B/en not_active Expired
- 1978-08-15 NL NL7808438A patent/NL7808438A/en not_active Application Discontinuation
- 1978-08-15 CA CA309,389A patent/CA1114074A/en not_active Expired
- 1978-08-16 FR FR7823876A patent/FR2400717A1/en active Granted
- 1978-08-16 BE BE189903A patent/BE869762A/en unknown
- 1978-08-16 IT IT26780/78A patent/IT1098094B/en active
- 1978-08-17 JP JP9959778A patent/JPS5443488A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| IL55362A0 (en) | 1978-10-31 |
| IT1098094B (en) | 1985-08-31 |
| NL7808438A (en) | 1979-02-20 |
| JPS5443488A (en) | 1979-04-06 |
| IT7826780A0 (en) | 1978-08-16 |
| US4277684A (en) | 1981-07-07 |
| FR2400717B1 (en) | 1983-08-05 |
| FR2400717A1 (en) | 1979-03-16 |
| DE2835583A1 (en) | 1979-03-01 |
| GB2004448B (en) | 1982-02-10 |
| BE869762A (en) | 1979-02-16 |
| GB2004448A (en) | 1979-03-28 |
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| MKEX | Expiry |