True coincidence count (TCC) and noise equivalent count (NEC) curves were measured with a standardized 20-cm-diameter nylon cylinder for five different CTI/Siemens PET (positron emission tomography) scanners with several scanner-collimator combinations: (1) 831/08-12 with 1-mm collimator septa; (2) 933/08-12 and 933/08-16 with 3 to 1-mm tapered collimator septa; and (3) 931/08-12 with 3 to 1-mm tapered and a 1-mm collimator septa and the 931/08-16 with 3 to 1-mm tapered collimator septa In addition, TCC and NEC curves on the 933/08-12 were compared with those from an Alderson brain phantom In general, it is found that the TCC curves indicated peak count rates and activity levels that were as much as 50% higher than the corresponding values from NEC curves The primary factor causing this difference is the noise effect of the randoms component It is demonstrated that, compared to the Alderson brain phantom, the standard 20-cm cylinder is a poor predictor of count rate performance for PET brain imaging >

Measuring PET scanner sensitivity: relating countrates to image signal-to-noise ratios using noise equivalents counts

Coded aperture imaging in high energy astronomy represents an important technical advance in instrumentation over the full energy range from X- to γ-rays and is playing a unique role in those spectral ranges where other techniques become ineffective or impracticable due to limitations connected to the physics of interactions of photons with matter. The theory underlying this method of indirect imaging is of strong relevance both in design optimization of new instruments and in the data analysis process. The coded aperture imaging method is herein reviewed with emphasis on topics of mainly practical interest along with a description of already developed and forthcoming implementations.

Coded aperture imaging in X- and gamma-ray astronomy

Cerium‐activated phosphors are characterized by their fast luminescence decay. Gadolinium orthosilicate (Gd2SiO5) is a material possessing a high atomic number, and can also play host to the cerium activator. Cerium‐doped Gd2SiO5 single crystals were grown by the Czochralski technique, and their luminescence properties were examined. The light output was 1.3 times larger than that of the best Bi4Ge3O12, and the decay constant was 60 ns at room temperature.

Cerium‐activated Gd2SiO5 single crystal scintillator

Non-invasive method of forming prostheses of skeletal structures internal to a body for use in reconstructive surgery. The selected internal skeletal structure is measured by subjecting the body to radiant energy to produce radiant energy responses that are detected to obtain representations delineating the skeletal structure. Three dimensional coordinate data defining the skeletal structure is generated from the obtained representations. The coordinate data is employed to control a sculpting tool to form the prosthesis.

Method of forming implantable prostheses for reconstructive surgery

The trend in the design of scanners for positron emission computed tomography has traditionally been to improve the transverse spatial resolution to several millimeters while maintaining relatively coarse axial resolution (1-2 cm). Several scanners are being built with fine sampling in the axial as well as transverse directions, leading to the possibility of the true volume imaging. The number of possible coincidence pairs in these scanners is quite large. The usual methods of image reconstruction cannot handle these data without making approximations. It is computationally most efficient to reduce the size of this large, sparsely populated array by back-projecting the coincidence data prior to reconstruction. While analytic reconstruction techniques exist for back-projected data, an iterative algorithm may be necessary for those cases where the point spread function is spatially variant. A modification of the maximum likelihood algorithm is proposed to reconstruct these back-projected data. The method, the iterative image space reconstruction algorithm (ISRA), is able to reconstruct data from a scanner with a spatially variant point spread function in less time than other proposed algorithms. Results are presented for single-slice data, simulated and actual, from the PENN-PET scanner.

An Iterative Image Space Reconstruction Algorthm Suitable for Volume ECT

PURPOSE:To enable the measurement of absorption correction and sensitivity of detector, by turning the gumma line source for absorption correction having specific amplitude in specific system around the rotary shaft of detector, in the repetitive scanning type positron CT. CONSTITUTION:The detector 4 is located on the entire plane on the circle 4' surrounding the inspected body and can be rotationable. The gamma line source 1 for absorption correction has the size of one sector, when the circle 1' where source 1 is positioned is divided equally into N. Two to three gamma ray sources are located on the circle 1' in equal distance. While the detector turnes once, the gamma ray source 1 is turned in the rate of M/N rotation. But M<N, and M and N do not have any common divisor. The rotation is made with the planet gear set. The full information required for absorption correction is obtained by N rotation of detector and measurement at the same time. Thus, the correction for absorption and correction for relative sensitivity for detector can be made.

Positron ct unit

PURPOSE:To detect annihilating gamma rays effectively and to improve the sensitivity of a positron CT by using multilayered reflection films for the rectangular parallelopiped Bi4Ge3O12 scintillator crystal of which only the surface facing a photoelectric multiplier is roughly polished. CONSTITUTION:Only the side of a rectangular parallelopiped crystal 1' of Bi4 Ge3O12 opposit from a photoelectric multiplier 6 side is roughly polished (about #400-#100 roughness in JIS), and all the other surfaces are made specular. In the case of spraying a reflecting agent 3' to the crystal surface first, only the pure BaSO4 is dissolved in an aq. soln. and the soln. is coated thinly by compressed air. A slight binder (for example, polyvinyl alcohol) is included in the 2nd layer to be spray-coated after the moisture of the pure BaSO4 layer of the 1st layer has throughly evaporated. After the evaporation of the moisture of the 2nd layer, a slightly larger amt. of the binder is included in the 3rd layer and the soln. is sprayed. Thereafter, the binder is increased successively and about 7-12 layers of reflection films are formed.

Gamma ray detector for positron ct

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

A whole body Positron CT has been developed. The system has a gantry consisting of 4 detector-rings and provides 7 slice-images simultaneously. The continuously rotating scan method is employed in this system. Each detector-ring consists of 192 gamma-ray detectors using BGO scintillation crystals (12×24×24 mm). A dual rectangular photomultiplier tube has been developed to increase the detector packing factor and to improve detector performance. Spatial resolution for reconstructed image is equal to 7.6 mm FWHM at the center of FOV. In a 20 cm-dia. cylindrical phantom, sensitivities are 33.9 kcps/(?Ci/cc) and 52.0 kcps/(?Ci/cc) in the in-plane and cross-plane, respectively. These include scattered coincidence events. By using the "projection background cutting method", scatter coincidence counts are estimated as 21.6 % and 23.3 % of the total coincidence counts in the in-plane and cross-plane, respectively.

Performance Study of the Whole-Body, Multilayer Positron Computed Tomograph. - PCTW-II -

OF THE DISCLOSURE An apparatus for optially transmitting signals from a rotatable body to a stationary side or vice versa in a non-contact manner, includes a plurality of light emitting elements excited by a PCM signal from a signal source and a plurality of light receiving elements disposed in opposition with the light emitting elements for receiving light therefrom. A plurality of sets each including plural light receiving or emitting elements are provided at the stationary side in association with the respective light emitting or receiving elements disposed at the rotatable body side. Alternatively, a plurality of sets each including plural light emitting elements are provided at the rotatable body side in associated with the respective light receiving elements disposed at the stationary side. The elements in such plural sets are selected in accordance with the rotation of the rotatable body.

Kenji Ishimatsu

Papers

Positron ct unit

Gamma ray detector for positron ct

Position detector for radiant ray

Performance Study of the Whole-Body, Multilayer Positron Computed Tomograph. - PCTW-II -

Optical signal transmission apparatus