US3777148A - Collimator - Google Patents

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US3777148A
US3777148A US00156926A US3777148DA US3777148A US 3777148 A US3777148 A US 3777148A US 00156926 A US00156926 A US 00156926A US 3777148D A US3777148D A US 3777148DA US 3777148 A US3777148 A US 3777148A
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collimator
sides
longitudinal axis
longitudinal
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F Miraldi
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01TMEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/29Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation
    • G01T1/2914Measurement of spatial distribution of radiation
    • G01T1/2985In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis)
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01TMEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16Measuring radiation intensity
    • G01T1/161Applications in the field of nuclear medicine, e.g. in vivo counting
    • G01T1/164Scintigraphy
    • G01T1/1641Static instruments for imaging the distribution of radioactivity in one or two dimensions using one or several scintillating elements; Radio-isotope cameras
    • G01T1/1642Static instruments for imaging the distribution of radioactivity in one or two dimensions using one or several scintillating elements; Radio-isotope cameras using a scintillation crystal and position sensing photodetector arrays, e.g. ANGER cameras
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/02Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03Computerised tomographs
    • A61B6/037Emission tomography

Definitions

  • ABSTRACT A collimator having a front and rear and a longitudinal axis passing from the front to the rear. Spaced septa between the front and the rear defining openings and including a plurality of longitudinal sides parallel to the longitudinal axis and converging downwardly at different angles to form channels which converge to a single focal line.
  • the septa further includes spaced parallel sides transverse to the longitudinal axis and intersecting with the longitudinal sides. The parallel sides form transverse channels which are non-focusing along the focal line.
  • the radioactive material which is commonly used gives off gamma rays. It is usually easier and more effective to change the gamma rays to visible light radiation than to try to detect the gamma rays directly.
  • the detection and conversion of gamma rays has its own difficulties. These problems include the discrimination between radiation resulting from photoelectric effect and compton effect and a determination of the location of the radiation within the source of radiation.
  • Scintillation cameras which generally. observe an area rather than a point have sought to solve the excessive time problem of the scanner. They have been relatively successful in this respect since they take much less time than a scanner to observe a given area.
  • the scintillation camera such as that disclosed in the Anger US. Pat. No. 3,011,057 also has its limitations. Because it must observe a relatively large twodimensional area at one time, the resolution is not as good as a scanner. This results because the phototubes in the Anger patent observe a large scintillation crystal and it views some scattering of light.
  • the present invention relates to a radiation scanning device and, more particularly, to a device which is well adapted for mapping radioisotope distributions within a human body.
  • a number of schemes have been developed for utilizing gamma detecting scintillation crystals for scanning selected portions of the human body to determine radioisotope distributions. Most schemes however produce a two-dimensional representation of the three-dimensional distribution. This results in a decreased resolution of a lesion because of superimposing and overlying activity. To enhance the resolution, the use of body-section scanning is proposed.
  • the layer-bylayer analysis which can be attained by tomoscanning allows a significant enhancement of detail and contrast by elimination of the superimposing and obscuring activity.
  • This invention has combined the advantages of a camera and a scanner in order to provide a threedimensional well defined image which can be formed in a relatively short amount of time.
  • This invention provides for the use of an elongated collimator and a scintillation crystal which usually view the entire width of the source. A single longitudinal scan enables the collimator to view the entire area of the source. A second scan from a different direction provides enough additional information for determining the depth of the source.
  • This invention also provides a means and technique for detecting the locations of scintillations in a crystal with a high degree of accuracy in order to provide good resolution of the source of the radiation. This improved resolution is obtained by means of a system utilizing logarithms of the amplitudes of the pulses emanating from photomultiplier tubes.
  • This invention is directed to a collimator which focuses to a single focal line. It includes a body having a front and rear and a longitudinal axis passing therebetween. Spaced septa define openings and include a plurality of longitudinal sides parallel to the longitudinal axis which converge downwardly at different angles to form channels. The septa further include spaced parallel sides transverse to the longitudinal axis and intersecting with the longitudinal sides which form transverse channels which are non-focusing along the focal line.
  • FIG. 1 is a schematic representation of the use of the invention of this application.
  • FIG. 2 is a block diagram of the elements of this radiation sensitive device.
  • FIG. 3 is a perspective view of the collimator used in this system.
  • FIG. 4 is a cross-sectional view of an alternate type of collimator.
  • FIG. 5 is a top sectional view of still another alternate type of collimator.
  • FIG. 6 is a perspective view of the scintillation crystal.
  • FIG. 7 is a schematic representative of the combined scintillation crystal and collimator.
  • this invention generally relates to a device for sensing radiation from a source which can be an organ of a human body.
  • a source which can be an organ of a human body.
  • An individual will, after taking a radioactive substance in medication, have a concentration of radiation in a given organ 11.
  • the detector 12 In a given position, the detector 12 has a rectangular field 14 of sensing.
  • the plane 14 In actual practice, the plane 14 has a given depth so there is actually a wedge-shaped channel viewing the source at any given moment.
  • the detector 12 is able to move in either direction across the source and thus detect the radiation.
  • the detector 12 has a definite viewing angle that can be varied in order to view the source from different directions. As explained in more detail hereinafter viewing the radioactive source from different directions allows an investigation of different reference planes within the source. This type of study is generally referred to as tomography.
  • FIG. 2 A block diagram of the system for the tomographic scanner of this invention is illustrated in FIG. 2.
  • a collimator 16 intercepts radiation normally gamma rays from a source and allows transmission of part to a scintillation crystal 18 which is usually in close proximity thereto.
  • the scintillation crystal converts to gamma rays to visible light.
  • Means for converting the visible light to electrical pulses includes photomultiplier tubes 20 and 22 which are located at each end of the scintillation crystal 18. The electrical pulses are subsequently transmitted respectively to the amplifiers 24 and 26.
  • the collimator, scintillation crystal, means for converting the visible light to electrical pulses and necessary physical and/or electrical connections make up the essentials of means for detecting radiation from a source of radiation.
  • the amplifiers 24 and 26 transmit their signals to a pulse height selector and a position selector which combines for a read out on a cathode ray tube.
  • the amplifiers as will be explained in more detail below change the amplitudes of the electrical pulses from the photomultiplier tubes to logarithms of the amplitudes before transmitting them to the pulse height selector.
  • the amplifier which converts the amplitudes to logarithms of the amplitudes, pulse height selector and the necessary electrical connections make up a means for operating on the output of the amplitudes of the electrical pulses in order to produce a substantially constant output for radiation of given energy levels regardless of the position of scintillations in the crystals.
  • Means for determining the positions of scintillations in the crystal include a position selector 28 which is basically circuitry for subtracting the logarithms transmitted by the amplifier 24 and 26.
  • the position selector 28 further includes mechanisms for scanning the source while recording information concerning the radiation and relative positions of the scanner and source.
  • a known circuit 34 triggers a cathode ray tube 32 when the pulse height selector accepts a signal. Simultaneously the position selector gives information to the cathode ray tube 32 in order to properly place the pulse on coordinate axes.
  • the collimator 16, illustrated in FIG. 3 has a front 36, rear 38 and sides 39 and 40 A longitudinal axis passes from the front to the rear. Septa 42 are generally parallel to each other from the front 36 and to the rear 38. In this respect the septa form a non-focusing system in the longitudinal direction of the collimator 16.
  • the septa 42 form openings or channels 44 with longitudinal sides 46 which are parallel to the longitudinal axis and which converge downwardly to a single focal line 48.
  • FIG. 4 An alternate embodiment of the collimator is illustrated in FIG. 4 and has pairs of openings 50, 51, 52 and 53 defined by sides which converge downwardly to different focal lines 54, 56, 58 and 60 respectively.
  • the focal lines 54, 56, 58 and 60 are formed along a plane perpendicular to the plane of the collimator in order to allow the collimator to be aimed.
  • a cross-section of the collimator is illustrated in FIG. 4, and focal lines 54, 56, 58 and 60 of the collimator extend the length of the collimator. Bu utilization of focal lines at different distances from the collimator different depths and areas of viewing can be made simultaneously. With the use of the collimator of FIG. 4, however, it would be necessary to use a pair of scintillation crystals for each pair of openings 50 which meets at a common focal line.
  • the dimensions of the collimator are selected to provide a desired resolution distance at the focal line and to have a field of view which is as uniform as possible. In practice, focal lengths of 6 to 20 cm have been found to be successful.
  • This collimator is of a general design which is a cross between a focusing collimator and a straight through or non-focusing collimator because it is focusing in one direction and non-focusing in the per pendicular direction. In general collimators are com-v posed of a heavy dense material such as lead.
  • FIG. 5 An alternate embodiment of the multiplane collimator of FIG. 4 is shown in FIG. 5 where the shape is circular and a series of channels in a ring form the set that refers to one plane.
  • gamma ray detection consists of a thin circular crystal and an array of photomultipliers as illustrated by the Anger U.S. Pat. No. 3,011,037 which is incorporated by reference herein.
  • a modification to the Anger summing circuit is necessary, however, in order to obtain depth information with this collimator.
  • the Anger method yields coordinate positions X and y of a scintillation as noted in FIG. 5. If, for example, it is desired to consider depth layer 56 of FIG. 4, then only the response for the set'of channels 51 is wanted.
  • the output of the Anger system must be transmitted to electrical circuits which add the information as X plus y If this sum has a value between A and A then the scintillation must have occurred from the set of channels 51. In a similar manner any other level can be determined.
  • the use of the collimator of FIG. 5 and known circuitry can convert a two-dimensional camera such as Angers to a tomographic camera.
  • the scintillation crystal 86 has agenerally rectangular cross-section which is uniform along its length. A rectangular cross-section was chosen because of favorable attenuation. Other configurations where the cross-sectional height is different than the width would also be acceptable.
  • the height 88 is greater than the width 90. A range of heights of 1 inch to 2 inches for sodium iodide has been successfully used in this invention. It is anticipated, however, that deviations from this height may also prove successful.
  • the width of the scintillation crystal is approximately one-half inch and some deviation may also be made from this dimension.
  • a coating 92 of highly reflective material such as magnesium oxide covers the scintillation crystal 86 in order to decrease the attenuation of radiation within the crystal.
  • the scintillation crystal 86 is mounted in proximity to the collimator as illustrated in FIG. 7.
  • the collimator 88 is focused to converge at a focal line 92.
  • Radiation received within the wedge-shaped channel 94 is received by and transmitted through the collimator 88 to the scintillation crystal 86 where a scintillation occurs which changes gamma radiation to visible light.
  • the wedge is really a complex configuration. Its sides converge in a nearly linear fashion but are slightly curved. After the focal line the sides diverge more rapidly than they converged.
  • the shape of the scintillation crystals was chosen to give an attenuation factor which would produce an acceptable slope to give realistic differences of the logarithms of the amplitudes so they could be detected as well as to give enough amplitudes to maintain an acceptable uncertainty.
  • the scintillation crystal was chosen to have a rectangular shape with a height of approximately I to 2 inches and a width of approximately one-half inch. This particular shape gave an attenuation constant which was satisfactory.
  • the scintillation crystal was covered with a high reflective coating such as magnesium oxide.
  • a collimator comprising: a body having a front and rear and a longitudinal axis passing from the front to therear; spaced septa between the front and the rear defining openings and including a plurality of longitudinal sides parallel to the longitudinal axis, said longitudinal sides converging downwardly at different angles to form channels which converge to a single focal line which is parallel to the longitudinal axis of the collimator and the septa further including spaced parallel sides transverse to the longitudinal axis and intersecting with the longitudinal sides, the parallel sides forming transverse channels which are non-focusing along the focal line.
  • the longitudinal sides are symmetric about either side of a line passing from the front to the rear and are substantially perpendicular to the parallel sides.

Abstract

A collimator having a front and rear and a longitudinal axis passing from the front to the rear. Spaced septa between the front and the rear defining openings and including a plurality of longitudinal sides parallel to the longitudinal axis and converging downwardly at different angles to form channels which converge to a single focal line. The septa further includes spaced parallel sides transverse to the longitudinal axis and intersecting with the longitudinal sides. The parallel sides form transverse channels which are non-focusing along the focal line.

Description

United States Patent 1 Miraldi COLLIMATOR [75] Inventor: Floro D. Miraldi, Cleveland Heights,
Ohio
[73] Assignee: Case Western Reserve University, Cleveland, Ohio [22] Filed: June 25, 1971 [21] Appl. No.: 156,926
Related (1.8. Application Data [62] Division of Ser. No. 48,166, June 22, 1970, Pat. No.
[ Dec. 4, 1973 OTHER PUBLICATIONS Tomographic Gamma-Ray Scanner by Anger, UCRL 16899 May 1966 pages 4-7 Longitudinal Tomographic by McAfee et al., Journal of Nuclear Medicine, Vol. 10, No. 10 page 654, October 1969.
Primary Examiner-Harold A. Dixon Attorney-Fay, Sharpe & Mulholland [57] ABSTRACT A collimator having a front and rear and a longitudinal axis passing from the front to the rear. Spaced septa between the front and the rear defining openings and including a plurality of longitudinal sides parallel to the longitudinal axis and converging downwardly at different angles to form channels which converge to a single focal line. The septa further includes spaced parallel sides transverse to the longitudinal axis and intersecting with the longitudinal sides. The parallel sides form transverse channels which are non-focusing along the focal line.
2 Claims, 7 Drawing Figures PATENTED SHEEI 2 0F 3 PATENTED BEE 41975 sum 3 or 3 PHOTQMULTIPLIER I I COLLIMATOR BACKGROUND OF THE INVENTION In order to study human or other organs the practice has developed of making such organs radioactive. The patient usually takes medication containing amounts of radioactive material.
The radioactive material which is commonly used gives off gamma rays. It is usually easier and more effective to change the gamma rays to visible light radiation than to try to detect the gamma rays directly. However, the detection and conversion of gamma rays has its own difficulties. These problems include the discrimination between radiation resulting from photoelectric effect and compton effect and a determination of the location of the radiation within the source of radiation.
Many types of radiation scanners have been developed in order to detect a radiation pattern within the organs. In this respect, the following articles have been published:
l. Anger, H. 0.: The Scintillation Camera for Radioisotope Localization. [In] Radioisotope in der Localizationsdiagnostik, ed. by G. Hoffman and K. Scheer. Stuttgard, F. K. Schottauer, 1967.
2. Anger, H. 0.: Tomograhic Gamma-Ray Scanner with Simultaneous Readout of Several Planes. UCRL-l6899 Rev., April 1967.
3. Brownell, G. I...: Theory of Radioisotope Scanning. Internat. J. Appl. Radiation & Isotopes 3: 181-192, August 1958 4. Cassen, B., Gass, H., and Crandell, P.: Improved- Resolution Fast-Section Scanner. (abst.) J. Nuclear Med. 9:307, June 1968.
5. Cassen, B.: Nonfocused COllimator Channel Systems in Cross-Time Correlation Three- Dimensional Scanning. (abst.) J. Nuclear Med. :391,June 1969.
6. Davis, T. P., and Martone, R. J.: The Hybrid Radioisotope Scanner. J. Nuclear Med. 7:114-127,
. February 1966.
7. Glass, H. 1.: A Depth-Focusing Collimator for the Investigation of the Brain Cortex. [In] Medical Radiosiotope Scanning: Proc.Symp. on M. Radioisotope Scanning, Athens, Apr. -24, 1964. Vienna, IAEA, 1965, Vol. I, pp. 243-252.
8. Hisada, K. -I., Hiraki, T., Ohba, S., and Matsudaira, M.: Simultaneous Performance of Isosensitive Scanning and Bilaminoscanning. Radiology 882129-134, January 1957.
9. Kuhl, D. E., and Edwards, R. 0.: Image Separation Radioisotope Scanning. Radiology 80:653-661, April 1963.
10. Kuhl, D. E., and Edwards, R. 0.: Rapid Brain Scanner with Self-Contained Computer and CRT Display for Both Rectilinear and Transverse Section Viewing. (abst.) J. Nuclear Med. 9:332, June 1968.
11. McRae, J and Anger, H. 0.: Initial Clinical Results Obtained with the Multiplane Tomograph ic Gamma-Ray Scanner. (abst.) U. Nuclear Med. 10: 356-257, June 1969.
12. Miraldi, F., DiChiro, G., and Skoff, G.: Evaluation of Current Methods of Radioisotope Tomography and Design of a New Device: The Tomoscanner. (abst.) K. J. Nuclear Med. 10: 358-359,
1me1969. l3. Patton, J., Brill, A. B., Erickson, J., Cook, W. E., and Johnston, R. E.: A New Approach to Mapping Three-Dimensional Radionuclide Distributions.
(abst.) J. Nuclear Med. 102363, June 1969. 14. Rotenberg, A. D.: Body Scanning. PhD. Thesis,
,Univ. of Toronto, November 1962, pp. 73-76. Past radiation sensitive scanners have been able to obtain relatively good resolution but have inherent limitations. They are normally designed to be focused at a single point or very small area passing through the source. Investigation of a large source requires an excessive amount of time in order to scan the entire area under observation. As a practical matter, patients may the and move during the scan thus jeopardizing the investigation.
Scintillation cameras which generally. observe an area rather than a point have sought to solve the excessive time problem of the scanner. They have been relatively successful in this respect since they take much less time than a scanner to observe a given area. However, the scintillation camera such as that disclosed in the Anger US. Pat. No. 3,011,057 also has its limitations. Because it must observe a relatively large twodimensional area at one time, the resolution is not as good as a scanner. This results because the phototubes in the Anger patent observe a large scintillation crystal and it views some scattering of light.
The present invention relates to a radiation scanning device and, more particularly, to a device which is well adapted for mapping radioisotope distributions within a human body. A number of schemes have been developed for utilizing gamma detecting scintillation crystals for scanning selected portions of the human body to determine radioisotope distributions. Most schemes however produce a two-dimensional representation of the three-dimensional distribution. This results in a decreased resolution of a lesion because of superimposing and overlying activity. To enhance the resolution, the use of body-section scanning is proposed. The layer-bylayer analysis which can be attained by tomoscanning allows a significant enhancement of detail and contrast by elimination of the superimposing and obscuring activity. Although many approaches to section scanning have been suggested and tried, all may be grouped intothe general procedure of scanning with collimators inclined to the plane of interest. This method was initiated by others and often goes by the name longitudinal section scanning. The general procedure is to obtain separate scans with a collimator at various angles to the plane of interest. The resulting separate scans are superimposed to give a reinforcement at a given plane.
This invention has combined the advantages of a camera and a scanner in order to provide a threedimensional well defined image which can be formed in a relatively short amount of time. This invention provides for the use of an elongated collimator and a scintillation crystal which usually view the entire width of the source. A single longitudinal scan enables the collimator to view the entire area of the source. A second scan from a different direction provides enough additional information for determining the depth of the source.
This invention also provides a means and technique for detecting the locations of scintillations in a crystal with a high degree of accuracy in order to provide good resolution of the source of the radiation. This improved resolution is obtained by means of a system utilizing logarithms of the amplitudes of the pulses emanating from photomultiplier tubes.
SUMMARY OF THE INVENTION This invention is directed to a collimator which focuses to a single focal line. It includes a body having a front and rear and a longitudinal axis passing therebetween. Spaced septa define openings and include a plurality of longitudinal sides parallel to the longitudinal axis which converge downwardly at different angles to form channels. The septa further include spaced parallel sides transverse to the longitudinal axis and intersecting with the longitudinal sides which form transverse channels which are non-focusing along the focal line.
FIG. 1 is a schematic representation of the use of the invention of this application.
FIG. 2 is a block diagram of the elements of this radiation sensitive device.
FIG. 3 is a perspective view of the collimator used in this system.
FIG. 4 is a cross-sectional view of an alternate type of collimator.
FIG. 5 is a top sectional view of still another alternate type of collimator.
FIG. 6 is a perspective view of the scintillation crystal.
FIG. 7 is a schematic representative of the combined scintillation crystal and collimator.
PREFERRED EMBODIMENT General System As illustrated in FIG. 1, this invention generally relates to a device for sensing radiation from a source which can be an organ of a human body. An individual will, after taking a radioactive substance in medication, have a concentration of radiation in a given organ 11.
The radiation emanating from the source 11, usually gamma rays, is sensed by a detector 12. In a given position, the detector 12 has a rectangular field 14 of sensing. In actual practice, the plane 14 has a given depth so there is actually a wedge-shaped channel viewing the source at any given moment.
The detector 12 is able to move in either direction across the source and thus detect the radiation. The detector 12 has a definite viewing angle that can be varied in order to view the source from different directions. As explained in more detail hereinafter viewing the radioactive source from different directions allows an investigation of different reference planes within the source. This type of study is generally referred to as tomography.
A block diagram of the system for the tomographic scanner of this invention is illustrated in FIG. 2. A collimator 16 intercepts radiation normally gamma rays from a source and allows transmission of part to a scintillation crystal 18 which is usually in close proximity thereto. The scintillation crystal converts to gamma rays to visible light. Means for converting the visible light to electrical pulses includes photomultiplier tubes 20 and 22 which are located at each end of the scintillation crystal 18. The electrical pulses are subsequently transmitted respectively to the amplifiers 24 and 26. The collimator, scintillation crystal, means for converting the visible light to electrical pulses and necessary physical and/or electrical connections make up the essentials of means for detecting radiation from a source of radiation.
The amplifiers 24 and 26 transmit their signals to a pulse height selector and a position selector which combines for a read out on a cathode ray tube. The amplifiers as will be explained in more detail below change the amplitudes of the electrical pulses from the photomultiplier tubes to logarithms of the amplitudes before transmitting them to the pulse height selector. The amplifier which converts the amplitudes to logarithms of the amplitudes, pulse height selector and the necessary electrical connections make up a means for operating on the output of the amplitudes of the electrical pulses in order to produce a substantially constant output for radiation of given energy levels regardless of the position of scintillations in the crystals.
Means for determining the positions of scintillations in the crystal include a position selector 28 which is basically circuitry for subtracting the logarithms transmitted by the amplifier 24 and 26. The position selector 28 further includes mechanisms for scanning the source while recording information concerning the radiation and relative positions of the scanner and source.
A known circuit 34 triggers a cathode ray tube 32 when the pulse height selector accepts a signal. Simultaneously the position selector gives information to the cathode ray tube 32 in order to properly place the pulse on coordinate axes.
COLLIMATOR The collimator 16, illustrated in FIG. 3 has a front 36, rear 38 and sides 39 and 40 A longitudinal axis passes from the front to the rear. Septa 42 are generally parallel to each other from the front 36 and to the rear 38. In this respect the septa form a non-focusing system in the longitudinal direction of the collimator 16. The septa 42 form openings or channels 44 with longitudinal sides 46 which are parallel to the longitudinal axis and which converge downwardly to a single focal line 48.
An alternate embodiment of the collimator is illustrated in FIG. 4 and has pairs of openings 50, 51, 52 and 53 defined by sides which converge downwardly to different focal lines 54, 56, 58 and 60 respectively. The focal lines 54, 56, 58 and 60 are formed along a plane perpendicular to the plane of the collimator in order to allow the collimator to be aimed. A cross-section of the collimator is illustrated in FIG. 4, and focal lines 54, 56, 58 and 60 of the collimator extend the length of the collimator. Bu utilization of focal lines at different distances from the collimator different depths and areas of viewing can be made simultaneously. With the use of the collimator of FIG. 4, however, it would be necessary to use a pair of scintillation crystals for each pair of openings 50 which meets at a common focal line.
The dimensions of the collimator are selected to provide a desired resolution distance at the focal line and to have a field of view which is as uniform as possible. In practice, focal lengths of 6 to 20 cm have been found to be successful. This collimator is of a general design which is a cross between a focusing collimator and a straight through or non-focusing collimator because it is focusing in one direction and non-focusing in the per pendicular direction. In general collimators are com-v posed of a heavy dense material such as lead.
An alternate embodiment of the multiplane collimator of FIG. 4 is shown in FIG. 5 where the shape is circular and a series of channels in a ring form the set that refers to one plane. In this collimator system gamma ray detection consists of a thin circular crystal and an array of photomultipliers as illustrated by the Anger U.S. Pat. No. 3,011,037 which is incorporated by reference herein. A modification to the Anger summing circuit is necessary, however, in order to obtain depth information with this collimator. The Anger method yields coordinate positions X and y of a scintillation as noted in FIG. 5. If, for example, it is desired to consider depth layer 56 of FIG. 4, then only the response for the set'of channels 51 is wanted. In order to obtain this response, the output of the Anger system must be transmitted to electrical circuits which add the information as X plus y If this sum has a value between A and A then the scintillation must have occurred from the set of channels 51. In a similar manner any other level can be determined. The net result is that the use of the collimator of FIG. 5 and known circuitry can convert a two-dimensional camera such as Angers to a tomographic camera.
SCINTILLATION CRYSTAL As illustrated in FIGS. 6 and 7, the scintillation crystal 86 has agenerally rectangular cross-section which is uniform along its length. A rectangular cross-section was chosen because of favorable attenuation. Other configurations where the cross-sectional height is different than the width would also be acceptable. The height 88 is greater than the width 90. A range of heights of 1 inch to 2 inches for sodium iodide has been successfully used in this invention. It is anticipated, however, that deviations from this height may also prove successful. The width of the scintillation crystal is approximately one-half inch and some deviation may also be made from this dimension. A coating 92 of highly reflective material such as magnesium oxide covers the scintillation crystal 86 in order to decrease the attenuation of radiation within the crystal.
In use, the scintillation crystal 86 is mounted in proximity to the collimator as illustrated in FIG. 7. The collimator 88 is focused to converge at a focal line 92. Radiation received within the wedge-shaped channel 94 is received by and transmitted through the collimator 88 to the scintillation crystal 86 where a scintillation occurs which changes gamma radiation to visible light.
While the channel 94 is wedge-shaped, the wedge is really a complex configuration. Its sides converge in a nearly linear fashion but are slightly curved. After the focal line the sides diverge more rapidly than they converged.
The shape of the scintillation crystals was chosen to give an attenuation factor which would produce an acceptable slope to give realistic differences of the logarithms of the amplitudes so they could be detected as well as to give enough amplitudes to maintain an acceptable uncertainty. In order to accomplish these ends the scintillation crystal was chosen to have a rectangular shape with a height of approximately I to 2 inches and a width of approximately one-half inch. This particular shape gave an attenuation constant which was satisfactory. In order to keep the amplitude of the pulses within the scintillation crystal at a relatively high level so they could be detected with acceptable uncertainty the scintillation crystal was covered with a high reflective coating such as magnesium oxide.
It should be understood that while the above described preferred embodiments give specific details, modifications will be available to those knowledgeable in the art. For example, scintillation crystals could possibly be replaced by more sophisticated, solid state items which translate gamma radiation to visible light radiation. I claim: 1. A collimator comprising: a body having a front and rear and a longitudinal axis passing from the front to therear; spaced septa between the front and the rear defining openings and including a plurality of longitudinal sides parallel to the longitudinal axis, said longitudinal sides converging downwardly at different angles to form channels which converge to a single focal line which is parallel to the longitudinal axis of the collimator and the septa further including spaced parallel sides transverse to the longitudinal axis and intersecting with the longitudinal sides, the parallel sides forming transverse channels which are non-focusing along the focal line. 2. The collimator of claim 1 wherein the longitudinal sides are symmetric about either side of a line passing from the front to the rear and are substantially perpendicular to the parallel sides.

Claims (2)

1. A collimator comprising: a body having a front and rear and a longitudinal axis passing from the front to the rear; spaced septa between the front and the rear defining openings and including a plurality of longitudinal sides parallel to the longitudinal axis, said longitudinal sides converging downwardly at different angles to form channels which converge to a single focal line which is parallel to the longitudinal axis of the collimator and the septa further including spaced parallel sides transverse to the longitudinal axis and intersecting with the longitudinal sides, the parallel sides forming transverse channels which are non-focusing along the focal line.
2. The collimator of claim 1 wherein the longitudinal sides are symmetric about either side of a line passing from the front to the rear and are substantially perpendicular to the parallel sides.
US00156926A 1970-06-22 1971-06-25 Collimator Expired - Lifetime US3777148A (en)

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US3886367A (en) * 1974-01-18 1975-05-27 Us Energy Ion-beam mask for cancer patient therapy
US3988585A (en) * 1974-06-11 1976-10-26 Medical Data Systems Corporation Three-dimensional rectilinear scanner
US4079259A (en) * 1973-07-18 1978-03-14 Blum Alvin S Tomographic apparatus and method
FR2400881A1 (en) * 1977-08-26 1979-03-23 Cardiac Med Sciences COLLIMATOR FOR FORMING AN IMAGE OF A PART OF A HUMAN ORGAN WITH A RADIATION DETECTOR CAMERA
US4240440A (en) * 1977-11-17 1980-12-23 Siemens Gammasonics, Inc. Method and apparatus for nuclear kymography providing a motion versus time display of the outer transverse dimensions of an organ
US4823017A (en) * 1986-12-19 1989-04-18 Siemens Gammasonics, Inc. Scintillation camera and multifocal fan-beam collimator used therein
US4849638A (en) * 1987-03-20 1989-07-18 Siemens Gammasonics, Inc. Single-focus collimator and scintillation camera system and method for using it
US4910759A (en) * 1988-05-03 1990-03-20 University Of Delaware Xray lens and collimator
WO2003073087A1 (en) * 2002-02-26 2003-09-04 Yxlon International Security Gmbh Simultaneous multifocal coherent x-ray scanning (cxrs)
US20040075058A1 (en) * 2002-10-22 2004-04-22 Ira Blevis Gamma camera
WO2007017846A2 (en) * 2005-08-11 2007-02-15 Navotek Medical Ltd. Localization of a radioactive source
US20070055090A1 (en) * 2004-08-12 2007-03-08 Navotek Medical Ltd. Medical Treatment System and Method
US20070205373A1 (en) * 2004-08-12 2007-09-06 Navotek Medical Ltd. Localization of a Radioactive Source Within a Body of a Subject
US20100042041A1 (en) * 2008-08-18 2010-02-18 Navotek Medical Ltd. Implantation device for soft tissue markers and other implants
US8886293B2 (en) 2010-11-24 2014-11-11 Mayo Foundation For Medical Education And Research System and method for tumor analysis and real-time biopsy guidance
WO2013168111A3 (en) * 2012-05-08 2015-02-05 Biosensors International Group, Ltd. Nuclear medicine tomography systems, detectors and methods
US9060732B2 (en) 2011-12-16 2015-06-23 Mayo Foundation For Medical Education And Research Multi-segment slant hole collimator system and method for tumor analysis in radiotracer-guided biopsy

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US4079259A (en) * 1973-07-18 1978-03-14 Blum Alvin S Tomographic apparatus and method
US3886367A (en) * 1974-01-18 1975-05-27 Us Energy Ion-beam mask for cancer patient therapy
US3988585A (en) * 1974-06-11 1976-10-26 Medical Data Systems Corporation Three-dimensional rectilinear scanner
FR2400881A1 (en) * 1977-08-26 1979-03-23 Cardiac Med Sciences COLLIMATOR FOR FORMING AN IMAGE OF A PART OF A HUMAN ORGAN WITH A RADIATION DETECTOR CAMERA
US4181839A (en) * 1977-08-26 1980-01-01 Cardiac Medical Sciences Corp. Multi-view collimator
US4240440A (en) * 1977-11-17 1980-12-23 Siemens Gammasonics, Inc. Method and apparatus for nuclear kymography providing a motion versus time display of the outer transverse dimensions of an organ
US4823017A (en) * 1986-12-19 1989-04-18 Siemens Gammasonics, Inc. Scintillation camera and multifocal fan-beam collimator used therein
US4849638A (en) * 1987-03-20 1989-07-18 Siemens Gammasonics, Inc. Single-focus collimator and scintillation camera system and method for using it
US4910759A (en) * 1988-05-03 1990-03-20 University Of Delaware Xray lens and collimator
WO2003073087A1 (en) * 2002-02-26 2003-09-04 Yxlon International Security Gmbh Simultaneous multifocal coherent x-ray scanning (cxrs)
EP1347287A1 (en) * 2002-02-26 2003-09-24 YXLON International X-Ray GmbH Simultaneous multi-focus coherent X-ray scattering (CXRS)
US20050105685A1 (en) * 2002-02-26 2005-05-19 Yxlon International Security Gmbh Simultaneous multifocal coherent x-ray scanning (cxrs)
US20040075058A1 (en) * 2002-10-22 2004-04-22 Ira Blevis Gamma camera
US6906330B2 (en) * 2002-10-22 2005-06-14 Elgems Ltd. Gamma camera
US20050218331A1 (en) * 2002-10-22 2005-10-06 Elgems Ltd. Gamma camera
US7102138B2 (en) 2002-10-22 2006-09-05 Elgems Ltd. Gamma camera
US20070205373A1 (en) * 2004-08-12 2007-09-06 Navotek Medical Ltd. Localization of a Radioactive Source Within a Body of a Subject
US8198600B2 (en) 2004-08-12 2012-06-12 Navotek Medical Ltd. Localization of a radioactive source
US8239002B2 (en) 2004-08-12 2012-08-07 Novatek Medical Ltd. Guiding a tool for medical treatment by detecting a source of radioactivity
US20070055090A1 (en) * 2004-08-12 2007-03-08 Navotek Medical Ltd. Medical Treatment System and Method
US20090127459A1 (en) * 2004-08-12 2009-05-21 Navotek Medical Ltd. Localization of a Radioactive Source
US8198588B2 (en) 2004-08-12 2012-06-12 Navotek Medical Ltd. Localization of a radioactive source within a body of a subject
US7847274B2 (en) 2004-08-12 2010-12-07 Navotek Medical Ltd. Localization of a radioactive source within a body of a subject
US8164064B2 (en) 2004-08-12 2012-04-24 Navotek Medical Ltd. Localization of a radioactive source within a body of a subject
US7952079B2 (en) 2004-08-12 2011-05-31 Navotek Medical Ltd. Localization of a radioactive source
WO2007017846A3 (en) * 2005-08-11 2007-09-07 Navotek Medical Ltd Localization of a radioactive source
WO2007017846A2 (en) * 2005-08-11 2007-02-15 Navotek Medical Ltd. Localization of a radioactive source
US7942843B2 (en) 2008-08-18 2011-05-17 Navotek Medical Ltd. Implantation device for soft tissue markers and other implants
US20100042041A1 (en) * 2008-08-18 2010-02-18 Navotek Medical Ltd. Implantation device for soft tissue markers and other implants
US8886293B2 (en) 2010-11-24 2014-11-11 Mayo Foundation For Medical Education And Research System and method for tumor analysis and real-time biopsy guidance
US9060732B2 (en) 2011-12-16 2015-06-23 Mayo Foundation For Medical Education And Research Multi-segment slant hole collimator system and method for tumor analysis in radiotracer-guided biopsy
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