A two-dimensional photon position encoder system (10) and process which includes a detector (20) for enhancing the spatial resolution of the situs of the origin of incident photons of gamma rays. A plurality of scintillator material members (22) interact with the incident photons and produce a quantifiable number of photons which exit the scintillation material members. A tuned light guide (68) having a plurality of radiation barriers (92) of predetermined lengths define slots which are operatively associated with one of the scintillator material members. These slots (90) serve to enhance the predictability of the statistical distribution of photons along the length of the slotted light guide (68). A detector (20) detects the distribution of the photons at preselected locations along the length of the slotted light guide. In one embodiment, this detector (20) comprises a photomultiplier (70) which gathers information concerning the photoelectrons which are then counted. The statistical distribution of these photoelectrons is processed by an improved pattern recognition technique such that the positioning information can be determined.

Two-dimensional photon counting position encoder system and process

A positron emission tomography camera having a plurality of detector rings positioned side-by-side or offset by one-half of the detector cross section around a patient area to detect radiation therefrom. Each ring contains a plurality of scintillation detectors which are positioned around an inner circumference with a septum ring extending inwardly from the inner circumference along each outer edge of each ring. An additional septum ring is positioned in the middle of each ring of detectors and parallel to the other septa rings whereby the inward extent of all the septa rings may be reduced by one-half and the number of detectors required in each ring is reduced. Each detector ring or offset ring includes a plurality of photomultiplier tubes and a plurality of scintillation crystals are positioned relative to the photomultiplier tubes whereby each tube is responsive to more than one crystal. Each alternate crystal in the ring is offset by one-half or less of the thickness of the crystal such that the staggered crystals are seen by more than one photomultiplier tube. This sharing of crystals and photomultiplier tubes allows identification of the staggered crystal and the use of smaller detectors shared by larger photomultiplier tubes thereby requiring less photomultiplier tubes, creating more scanning slices, providing better data sampling, and reducing the cost of the camera. The offset detector ring geometry combined with the additional septa reduces the cost of the positron camera and improves its performance.

Positron emission tomography camera

A radiation detector comprising a scintillator array for emitting scintillation light upon incidence of radiation to a scintillator and distributing the scintillation light to the other scintillators at a predetermined distribution ratio and plural photomultiplier tubes optically coupled to the scintillator array for converting the scintillation light into an amplified electrical signal representing an incident position of the radiation to the scintillator array. The scintillator array comprises plural scintillators, and each pair of neighboring scintillators have coupling surface on both of confronting surfaces thereof for optically coupling the neighboring scintillators therethrough, each of the coupling surfaces having at least one of a roughened surface and a mirror-polished surface having different transmissivities to light passing therethrough to thereby adjust the distribution ratio of the scintillation light transmitted from one of the scintillators to another.

Radiation detector using scintillator array

A radioisotope camera (10) having an array (12) of scintillation crystals (13) arranged in N rows and M columns and adapted to be struck by gamma-rays from a subject, a separate solid state photodetector (15 ) optically coupled to each crystal (13), and N+M amplifiers (24) connected to the photodetectors (15) to distinguish the particular row and column of an activated photodetector. One of the anode or cathode leads (33 or 34) of each photodetector (15) is coupled to the row amplifier (24) associated with the row containing that photodetector while the other of the two leads (34 or 33) is coupled to the column amplifier (24) associated with the column containing that photodetector.

Readout system for multi-crystal gamma cameras

A method, system and a radiation detector system for use therein are provided for determining the depth distribution of radiation-emitting material distributed in a source medium, such as a contaminated field, without the need to take samples, such as extensive soil samples, to determine the depth distribution. The system includes a portable detector assembly with an x-ray or gamma-ray detector having a detector axis for detecting the emitted radiation. The radiation may be naturally-emitted by the material, such as gamma-ray-emitting radionuclides, or emitted when the material is struck by other radiation. The assembly also includes a hollow collimator in which the detector is positioned. The collimator causes the emitted radiation to bend toward the detector as rays parallel to the detector axis of the detector. The collimator may be a hollow cylinder positioned so that its central axis is perpendicular to the upper surface of the large area source when positioned thereon. The collimator allows the detector to angularly sample the emitted radiation over many ranges of polar angles. This is done by forming the collimator as a single adjustable collimator or a set of collimator pieces having various possible configurations when connected together. In any one configuration, the collimator allows the detector to detect only the radiation emitted from a selected range of polar angles measured from the detector axis. Adjustment of the collimator or the detector therein enables the detector to detect radiation emitted from a different range of polar angles. The system further includes a signal processor for processing the signals from the detector wherein signals obtained from different ranges of polar angles are processed together to obtain a reconstruction of the radiation-emitting material as a function of depth, assuming, but not limited to, a spatially-uniform depth distribution of the material within each layer. The detector system includes detectors having different properties (sensitivity, energy resolution) which are combined so that excellent spectral information may be obtained along with good determinations of the radiation field as a function of position.

Method and system for determining depth distribution of radiation-emitting material located in a source medium and radiation detector system for use therein

An apparatus for a detecting the location of incident radiation comprises at least one pair of assembly comprised of a scintillation crystal consisting of a plurality of crystal segments, a pair of photo-multiplier tubes optically coupled to the scintillation crystal so as to be able to detect a scintillation produced in any one of these crystal segments. These plural crystal segments are coupled to each other in such manner that any scintillation produced in any single crystal segment will cause the photo-multiplier tubes to deliver substantially a same output irrespective of the illuminating position within this crystal segment, and also that scintillations produced in the respective crystal segments will cause the photo-multiplier tubes to deliver outputs which are different in level for the respective crystal segments.

Apparatus for detecting the location of incident radiation

PURPOSE: To reduce the number of component parts such as the photomultiplier tube and the like, by connecting the outputs of the photomultiplier tubes provided across the scintillator group in which plural numbers of scintillators are connected together optically to the position detecting circuit which specifies the scintillator detected the radiant rays. CONSTITUTION: The scintillators 3 composed of the BGO crystal are joined together in e.g. four units to form the bartype scintillator group. And the photomultiplier tubes 4 and 4 are attached across the scintillator group. The outputs of these tubes 4 and 4 are connected to the circuit which consisists of the time signal generating part, the energy selecting part and the position detecting part each and then specifies the scintillator which detected the radiant rays and via the preamplifier. Thus the position detector is formed. A number of units of such position detectors are disttibuted close and vertically onto the paper surface to obtain the detector group of the position CT or the like. In this case, the right and left thicknesses of the scintillator prescribe the thickness of each dislocation or the space for each dislocation. As a result, the number of component parts can be reduced for the photomultiplier tubes and the like without lowering the reliability for decision of position, at the same time securing a close distribution of parts. COPYRIGHT: (C)1981,JPO&Japio

Position detector for radiant ray

PURPOSE:To improve the resolution of positions without increasing radiation detectors by providing a movalbe member consisting of a radiation shielding material between an object to be inspected and the detectors, and providing the apertures of said members at 1/N of the detection areas of the radiation detectors. CONSTITUTION:A detector ring 10 consists of many radiation detectors which are arrayed annularly around an axis O. Each of the radiation detectors themselves consists of, for example, a scintillation crystal 11A and a photoelectron multiplier 11B. A movable member 12 is supported so as to be made rotatable around the axis O on the inner side of the detector ring, and the member itself is constituted of an X-ray shielding material, for example, tungsten. Apertures of the number corresponding to the number of the radiation detectors are provided at equal intervals on the periphery of the movable member, so that radiations can be made incident to the radiation detectors only through these apertures. The apertures have the circumferential length occupying 1/N of the detection areas of the radiation detectors.

Scanner of positron emission ct device

This paper describes evaluation and correction of count rate characteristics of POSITOLOGICA II, a multi-slice whole body positron emission tomography system. The present study was performed using three phantoms; a 5 cm inner diameter, water-filled lucite cylinder, a 20 cm inner diameter, water-filled lucite cylinder and a chest phantom. After injection of high activity (about 1.85 GBq (50 mCi] of 13N ammonia into each phantom, rates of true coincidence, random coincidence and single photon detections were measured during decay of the isotope through more than two orders of magnitude of activity. At very high levels of activity, count rate characteristics of the system were saturated and limited to 660 kcps of total coincidence rate, which was the sum of rates in on-time and off-time windows, by the FIFO (first-in first-out) output frequency. Below those levels of activity the relationship between count loss and true coincidence rate was not unique but depended on the phantom configurations, suggesting that count loss correction using the above relationship was inadequate for quantitative study. However, the relationship between count loss and single rate was almost independent of the phantom configurations. Thus in conclusion count loss could be corrected using single rate for POSITOLOGICA II. A practical method of count loss correction was also proposed.

[Count rate characteristics and count loss correction of Positologica II: a whole body positron emission tomograph].

PURPOSE:To uniformize sampling frequency distribution, by successively positioning the arrangement center of a ring detector on the circumference of a circle having a center being that of a visual field and arbitrarily combining the radius and moving speed of the ring detector. CONSTITUTION:A shaft member 25 having a U-shaped cross-section is integrally provided at the leading end of a rotary shaft 35a driven by a motor by molding and an output shaft 33 and an outer frame member 34 are engaged with the inner and outer surfaces of the shaft member 35 through bearings 37, 36. The center of the output shaft 33 is made eccentric with respect to the center of the shaft member 35 and that of the outer frame member 34 and the pinion 32 fixed to the output shaft 33 is meshed with the gear 31 provided to the opening part of the outer frame member 34 in one side. The output shaft 33 is fixed to a holding plate supporting a ring detector so as to freely move the same before and behind and left and right and the outer frame member 34 is fixed to the support member of the ring detector. When the shaft 35a is driven by the motor, the output shaft 33, therefore, the ring detector moves as shown by the curve of a drawing. By this method, the distribution of sampling frequency is uniformized and its diagnosis is made accurate.

Akira Ogushi

Papers

Apparatus for detecting the location of incident radiation

Position detector for radiant ray

Scanner of positron emission ct device

[Count rate characteristics and count loss correction of Positologica II: a whole body positron emission tomograph].

Scanning apparatus for positron emission ct