WO1985004959A1 - Procede et appareil de detection de photons gamma - Google Patents

Procede et appareil de detection de photons gamma Download PDF

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Publication number
WO1985004959A1
WO1985004959A1 PCT/AU1985/000094 AU8500094W WO8504959A1 WO 1985004959 A1 WO1985004959 A1 WO 1985004959A1 AU 8500094 W AU8500094 W AU 8500094W WO 8504959 A1 WO8504959 A1 WO 8504959A1
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WO
WIPO (PCT)
Prior art keywords
gamma
scintillant
elements
photonsensitive
photon
Prior art date
Application number
PCT/AU1985/000094
Other languages
English (en)
Inventor
Meir Lichtenstein
Gregory Mack Jost
Original Assignee
Meir Lichtenstein
Gregory Mack Jost
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Meir Lichtenstein, Gregory Mack Jost filed Critical Meir Lichtenstein
Publication of WO1985004959A1 publication Critical patent/WO1985004959A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/28—Measuring radiation intensity with secondary-emission detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/20—Measuring radiation intensity with scintillation detectors
    • G01T1/202—Measuring radiation intensity with scintillation detectors the detector being a crystal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/20—Measuring radiation intensity with scintillation detectors
    • G01T1/203—Measuring radiation intensity with scintillation detectors the detector being made of plastics
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/20—Measuring radiation intensity with scintillation detectors
    • G01T1/204—Measuring radiation intensity with scintillation detectors the detector being a liquid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T5/00—Recording of movements or tracks of particles; Processing or analysis of such tracks
    • G01T5/08—Scintillation chambers

Definitions

  • This invention relates to gamma photon detection apparatus, especially such apparatus for use in nuclear medicine.
  • Koslow Technologies Corporation discloses a radiation imaging system comprising an array of parallel conventional s ⁇ intillator detector crystals optically coupled at opposite ends to respective planar or curved arrays of parallel luminescent light-conducting channels.
  • the channels of the respective arrays extend in mutually orthogonal directions: when the arrays are curved,, the system is said to have application as a positron ring camera.
  • This imaging system has a number of disadvantages.
  • the scintillator crystals are said to be conventional and may thus typically comprise thallium activated sodium iodide.
  • gamma photon detection apparatus comprising: an ordered array of elongate gamma photonsensitive elements each arranged to generate within the element a confined primary current of light photons in response to a received gamma photon; and an ordered array of elongate scintillant elements extending angularly with respect to said gamma photonsensitive elements and each responsive to the receipt of light photons transversely emitted by said gamma photonsensitive elements to generate within the respective scintillant element a confined secondary current of light photons or electrons; whereby a set of . said currents are jointly indicative of the location of an event which was caused by the received gamma photon and gave rise to the detected currents.
  • the gamma photonsensitive elements and/or the scintillant elements may comprise elongate solid bodies of scintillant or elongate tubes containing liquid scintillant.
  • the light photon absorption wavelength of the scintillant elements matches the light photon emission wavelength of the gamma photonsensitive elements.
  • said array of gamma photonsensitive elements is sandwiched between respective arrays of said scintillant elements.
  • the scintillant elements of one of these arrays preferably extend at a substantial angle to the scintillant elements of the other of said arrays.
  • the invention further provides a method of detecting a gamma photon, comprising: arranging for said photon to cause a Compton event; confining a first proportion of the resultant light photons as a primary current; absorbing in a scintillant a second proportion of said resultant light photons emitted transversely of said current; emitting further light photons in response to such absorption; confining a fraction of the further light photons as a secondary current; and detecting said currents; whereby a set of said currents are jointly indicative of the location of an event which was caused by the respective gamma photon and gave rise to the detected currents .
  • Figure 1 is a schematic .representation of a segment of gamma photon detection apparatus according to the invention
  • Figure 2 is a diagram illustrating detection of a gamma photon by the apparatus of Figure 1;
  • FIG 3 is a partly sectioned schematic view of a positron camera comprising gamma photon detection apparatus according to the invention.
  • a simplified orthogonal arrangement according to the invention is depicted in Figures 1 and 2 for purposes of illustration.
  • This arrangement includes a primary array 10 of elongate gamma photonsensitive elements 12 consisting of co-planar parallel tubes filled with liquid gamma photonsensitive scintillant 13, viz, toluene containing 2, 5 diphenyloxazole, commonly referred to as PPO.
  • a secondary array 14 of co-planar, parallel elongate scintillant elements 16 is arranged adjacent array 10 so that elements 16 extend orthogonally with respect to tubes 12.
  • Each scintillant element 16 consists of a glass tube filled with the liquid light photonsensitive scintillant (17) 1, 4 bis(2-5( ⁇ henyloxazole) ) benzene, commonly referred to as POPOP.
  • Tubes 12, 16 are conveniently 2cm in diameter and the respective concentrations of the scintillants are 5gms/l and lgm/1.
  • the absorption wavelength of POPOP matches the emission band of PPO, so that the POPOP can absorb light emitted by PPO at a wavelength of interest and re-emit it equally in all directions at a longer wavelength, but the converse cannot occur.
  • An example is the absorption of the PPO emission at 370nm and its re-emission by the POPOP at 440nm.
  • Each tube 12, 16 terminates at one end at a photo ultiplier tube (PMT) 18.
  • PMT photo ultiplier tube
  • Each PMT is coupled to its respective tube, using silicone grease, by a flat piece of glass glued at the end of the tube by means of epoxy resin.
  • the output of each PMT 18 is fed to a fast co-incidence detector via an amplifier and also into a multi channel analyser.
  • tubes 12, 16 are in close proximity but do not touch.
  • tubes 12, 16 need not be glass but may be formed in a suitable plastics material, e.g. fused plastics film. 5
  • tubes 12 and 16 need not be of the same size or shape.
  • L5 scintillant 13 is confined by total internal reflection within the respective tube 12 as a primary current 33 of light photons which travels away from the Compton event in both directions and is detected by the associated PMT
  • the secondary tubes 16 are of substantially smaller diameter than the primary tubes 12, say 1mm and 5mm respectively.
  • m pipes 12 as primary and n pipes 14 as _ secondary in this hypothetical two-dimensional detector
  • the number of PMTs can be further reduced because the end of each tube end can be connected to a PMT.
  • Many tube ends connect to each PMT.
  • the number of PMTs can be reduced to 2 m + 2n .
  • n 100 tubes.
  • groups of 10 adjacent tubes can be coupled to each of 10 PMTs, and at the other end of the array, every 10th tube can be connected to a PMT.
  • an output in 2 of 20 tubes defines in which of the 100 tubes the event occurred.
  • the detector must analyze the timing and location of the multiple Compton events to determine the position and timing of the first event.
  • the chronological order of Compton scatters can be determined for distances greater than 15cm, by spacing out the layers of the detector such that inter Compton distances greater than 15cm become common.
  • a graded absorber greatly reduces the body scattered radiation (low energy gammas) while affecting the 511KeV to only a slight extent. Such an absorber needs to be used to reduce detection of gamma rays already scattered in the body.
  • the camera is arranged as a cylinder 8, 40cms long with a radius of 25cms and containing a depth of scintillator of 20cms.
  • the tubes 12' of primary scintillant are arranged in concentric layers 10' and each tube runs parallel to the long axis of the cylinder. If n is the number of such tubes then the
  • these primary tubes are made of 0.5cms solid plastics scintillant, then the camera would use 5600 separate tubes 12' and 150 high speed PMTs arranged into 40 layers for the primary photosensitive system alone. This number can be reduced.
  • the average depth of the tubes (in the radial direction) is increased to 1cm so that only 20 layers are used. The number of tubes is halved. It may be useful to grade the tubes from less than 1cm in diameter on the inside to more than 1cm in diameter on the outside.
  • the width (circumferential) of the primary tubes can be markedly increased if only the secondary tubes 16* are used to provide precise localization. If, for example, the average width is 5cms then the number of primary tubes is approximately 600 and the number of high speed PMTs is just 50.
  • Tubes 12* then provide precise energy and timing information, and only approximate positional information, enough to prevent ambiguity when reading the precise positions of multiple events using an array of secondary scintillant elements, as explained below.
  • the secondary scintillant tubes 16' need not be connected to the higher speed PMTs as they are not being used to provide fast timing information, thus reducing cost.
  • a layer 14' of secondary tubes 16' is placed between each pair of concentric layers 10' of primary tubes 12' and the tubes 16' extend at an angle of 45° to the long axis of the cylinder.
  • Each secondary tube thus traces the path of a helix. The direction of the helix alternates from one layer 14* to the next so that each Compton event in a tube 12' contributes photons to two groups of secondary tubes, one above and one below, which are at 90° to each other and so provide precise positional information.
  • the ideal form for a secondary tube 16' is that of a ribbon, 5mm wide and very thin, of solid plastics scintillant. There may be excessive attentuation of light transmission along such a thin layer of plastic so the alternative may be to use groups of thin glass or plastics tubes filled with liquid scintillator. The number of secondary units is then approximately 6200 and the corresponding PMT number is 158.
  • a 40cm long x 25cm internal radius detector therefore uses 600 pieces of 40cm x 5cm x 1cm strips of plastics scintillant for the primary tubes 12* with just 50 high speed PMTs. It uses 6200 secondary scintillant units and 160 sensitive PMTs. Note that this does not involve sealing 6200 light tubes. Simply sharply bending (180°) the light tubes at high temperature will be adequate.
  • the same result may be achieved by using a hexagonal detector with all pipes now being straight or of composite straight segments.
  • the detector area is larger, being 40 x 2 x 25cms, which equals 0.62 square metres for the dimensions proposed above. This is more than twice that of other designs based on PMTs arranged in rings, but the major advantage with this detector is that there are no lead septa between rings. The detector is able to accept coincidences between any two regions of the detector, i.e.
  • the detector unlike those with lead septa is able to detect photon pairs emerging from the body at any angle providing they are covered by the detector. This enables full use of the detector to be obtained. It has a large solid angle of acceptance, about 0.6 x 4/3 ⁇ r , compared to conventional detectors.
  • Intra-detector resolution is equal to the separation between tube centres. This produces an intra-patient resolution of approximately half this, i.e. between 2.5mm and 3.7mm for 5mm tube thus enabling utilization of the small positron path lengths of 18p(15) positron. This is superior to the best figures quoted for ring detector systems with the order of 4.8mm (which is not in all axes) . Use of time of flight is highly advantageous and possible although this is not essential.
  • the number of PMTs can be around 300 or less, depending on design, which is less than the number in conventional multi ring systems. There is no loss of energy resolution compared to any of the conventionally used detectors other than Nal.
  • the front part of the detector using liquid or plastics scintillant, and have the back part of sodium iodide, and only choose these sequences that have one event in the organic scintillator and the remainder in the solid sodium iodide detector at the back.
  • Most SllKeV photons are forward scattered after Compton reactions.
  • Another alternative approach to the use of thick primary and thin secondary tubes is to use tubes of the same diameter and fill them with a high concentration of primary scintillant together with a low concentration of thin secondary scintillant. If an event occurs in one tube, some of the light flash produced at the primary scintillant wavelength will be converted in the first tube to the longer wavelength and then transmitted along it, but provided the low secondary scintillant concentration is small enough, some of the primary scintillant light will escape to be converted in the adjacent tube which runs at an angle. Likewise, transfer can occur from the second tube to the first. This arrangement would simplify construction as all tubes are of the same thickness but the cost would be a loss of sensitivity and therefore count rate and energy resolution.
  • isotopes produce a photon as well as a positron.
  • a high efficiency detector can detect this gamma photon as well as the annihillation photons and an approximate plane of its origin can be calculated. * In many cases this could supplement or replace TOF in providing positional information on the emitting isotope. This plane is in fact the surface of a cone.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Molecular Biology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Nuclear Medicine (AREA)

Abstract

Un appareil de détection de photons gamma comporte un réseau (10) d'éléments allongés sensibles aux photons gamma (12) disposés chacun pour produire à l'intérieur de l'élément un courant primaire captif de photons lumineux en réponse à un photon gamma reçu. Un réseau (14) d'éléments scintillants allongés (16) s'étend angulairement par rapport aux éléments sensibles aux photons gamma. Chaque élément scintillant (16) répond à la réception des photons lumineux émis transversalement par les éléments sensibles aux photons gamma afin de produire dans l'élément scintillant respectif un courant secondaire captif de photons lumineux. Une série de ces courants indique conjointement l'emplacement d'un événement causé par le photon gamma reçu et ayant provoqué le courant détecté.
PCT/AU1985/000094 1984-04-26 1985-04-26 Procede et appareil de detection de photons gamma WO1985004959A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPG4713/84 1984-04-26
AU471384 1984-04-26

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4942302A (en) * 1988-02-09 1990-07-17 Fibertek, Inc. Large area solid state nucler detector with high spatial resolution
US5103098A (en) * 1989-11-09 1992-04-07 Board Of Regents, The University Of Texas System High resolution gamma ray detectors for positron emission tomography (pet) and single photon emission computed tomography (spect)
WO1993009447A1 (fr) * 1991-10-29 1993-05-13 Board Of Regents, The University Of Texas System Detecteur de rayons gamma sensible a la position
US5334839A (en) * 1991-10-29 1994-08-02 The Board Of Regents, The University Of Texas System. Position sensitive radiation detector
US5374824A (en) * 1994-01-05 1994-12-20 Board Of Regents, The University Of Texas System Method and apparatus for determining and utilizing cross-talk adjusted scintillating fibers
WO2017077164A1 (fr) * 2015-11-04 2017-05-11 Consejo Superior De Investigaciones Científicas (Csic) Système de caméra compton à rayons gamma avec mesure de temps de vol
CN110709133A (zh) * 2017-07-21 2020-01-17 瓦里安医疗系统粒子疗法有限责任公司 粒子束监测系统和方法
EP4239376A1 (fr) * 2022-03-03 2023-09-06 Seethru AI Inc. Systèmes, dispositifs et procédés pour un scanner à rayons x à faisceau crayon

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3873838A (en) * 1974-04-22 1975-03-25 Atomic Energy Commission Two-dimensional readout system for radiation detector
JPS57104873A (en) * 1980-12-23 1982-06-30 Toshiba Corp Radiation detector
WO1983003683A1 (fr) * 1982-04-18 1983-10-27 Koslow Techn Corp Grands reseaux de detecteurs discrets de radiation ionisante multiplexes utilisant des convertisseurs optiques fluorescents

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3873838A (en) * 1974-04-22 1975-03-25 Atomic Energy Commission Two-dimensional readout system for radiation detector
JPS57104873A (en) * 1980-12-23 1982-06-30 Toshiba Corp Radiation detector
WO1983003683A1 (fr) * 1982-04-18 1983-10-27 Koslow Techn Corp Grands reseaux de detecteurs discrets de radiation ionisante multiplexes utilisant des convertisseurs optiques fluorescents

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4942302A (en) * 1988-02-09 1990-07-17 Fibertek, Inc. Large area solid state nucler detector with high spatial resolution
US5103098A (en) * 1989-11-09 1992-04-07 Board Of Regents, The University Of Texas System High resolution gamma ray detectors for positron emission tomography (pet) and single photon emission computed tomography (spect)
US5281821A (en) * 1989-11-09 1994-01-25 Board Of Regents, The University Of Texas System Position sensitive gamma ray detector
WO1993009447A1 (fr) * 1991-10-29 1993-05-13 Board Of Regents, The University Of Texas System Detecteur de rayons gamma sensible a la position
US5334839A (en) * 1991-10-29 1994-08-02 The Board Of Regents, The University Of Texas System. Position sensitive radiation detector
WO1994023312A1 (fr) * 1993-03-26 1994-10-13 Board Of Regents, The University Of Texas System Detecteur de rayonnement sensible a la position
US5374824A (en) * 1994-01-05 1994-12-20 Board Of Regents, The University Of Texas System Method and apparatus for determining and utilizing cross-talk adjusted scintillating fibers
WO2017077164A1 (fr) * 2015-11-04 2017-05-11 Consejo Superior De Investigaciones Científicas (Csic) Système de caméra compton à rayons gamma avec mesure de temps de vol
CN110709133A (zh) * 2017-07-21 2020-01-17 瓦里安医疗系统粒子疗法有限责任公司 粒子束监测系统和方法
EP4239376A1 (fr) * 2022-03-03 2023-09-06 Seethru AI Inc. Systèmes, dispositifs et procédés pour un scanner à rayons x à faisceau crayon

Also Published As

Publication number Publication date
EP0179095A1 (fr) 1986-04-30

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