Design Consideration for a Continuously Rotating Positron Computed Tomograph
TL;DR: In this article, the design of a whole-body, multislice Positron CT with three detector rings, 160 BGO crystal/ring, and a continuously rotating scan is described.
Abstract: Design consideration for a whole-body, multislice Positron CT having 3 detector rings, 160 BGO crystal/ring, and a continuously rotating scan is described. The one detector ring has 40 "BGO Quad-detectors", each of which consists of 4 BGO crystals and two photomultipliers. Improvements in the BGO crystal and the photomultiplier have been accomplished. Geometrical configuration of the collimator was determined through optimization of the main performances of both the inplane and cross-plane images, utilizing the formulae for a cylindrical phantom with uniform activity. A continuously rotating scan (0.5-1rps) with unequally spaced the Quad-detector units is used. Along with this scan, a 32-channel rotary photo-coupler was developed for contact-free data transmission.
Citations
More filters
TL;DR: In this article, the light output was 1.3 times larger than that of the best Bi4Ge3O12, and the decay constant was 60 ns at room temperature.
Abstract: 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.
342 citations
TL;DR: The ECAT ART provides a viable alternative to conventional full ring PET scanners without compromising the performance required for clinical PET imaging.
Abstract: Advances in fully three-dimensional (3D) image reconstruction techniques have permitted the development of a commercial, rotating, partial ring, fully 3D positron emission tomographic (PET) scanner, the ECAT ART. The system has less than one-half the number of bismuth germanate detectors compared with a full ring scanner with the equivalent field of view, resulting in reduced capital cost. The performance characteristics, implications for installation in a nuclear medicine department, and clinical utility of the scanner are presented in this report. The sensitivity (20 cm diameter×20 cm long cylindrical phantom, no scatter correction) is 11400 cps·kBq−1·ml−1. This compares with 5800 and 40500 cps·kBq−1·ml−1 in 2D and 3D respectively for the equivalent full ring scanner (ECAT EXACT). With an energy window of 350–650 keV the maximum noise equivalent count (NEC) rate was 27 kcps at a radioactivity concentration of ~15 kBq·ml−1 in the cylinder. Spatial resolution is ~6 mm full width at half maximum on axis degrading to just under 8 mm at a distance of 20 cm off axis. Installation and use within the nuclear medicine department does not appreciably increase background levels of radiation on gamma cameras in adjacent rooms and the dose rate to an operator in the same room is 2 µSv·h−1 for a typical fluorine-18 fluorodeoxyglucose (18F-FDG) study with an initial injected activity of 370 MBq. The scanner has been used for clinical imaging with18F-FDG for neurological and oncological applications. Its novel use for imaging iron-52 transferrin for localising erythropoietic activity demonstrates its sensitivity and resolution advantages over a conventional dual-headed gamma camera. The ECAT ART provides a viable alternative to conventional full ring PET scanners without compromising the performance required for clinical PET imaging.
101 citations
Cites background from "Design Consideration for a Continuo..."
...A design for a partial ring, continuously rotating bismuth germanate (BGO) based tomograph was proposed in the early 1980s [22]....
[...]
TL;DR: In this article, a position-sensitive photodiode/BGO detector for high-resolution, multilayer positron emission tomography (PET) is presented, where position sensitivity is achieved by dividing the 3 mm*20 mm rectangular photosensitive area along the diagonal to form two triangular segments.
Abstract: The authors present initial results for a position-sensitive photodiode/BGO (bismuth germanate) detector for high-resolution, multilayer positron emission tomography (PET). Position sensitivity is achieved by dividing the 3 mm*20 mm rectangular photosensitive area along the diagonal to form two triangular segments. Each segment is individually connected to a low-noise charge amplifier. The photodiodes and crystals are cooled to -100 degrees C to reduce dark current and increase the BGO signal. With an amplifier peaking time of 17 mu s, the sum of the signals (511-keV photopeak) was 3200 electrons with a full width at half maximum (FWHM) of 750 electrons. The ratio of one signal to the sum determined the depth of interaction with a resolution of 11 mm FWHM. >
61 citations
TL;DR: In this article, a pseudo-continuous ring of BGO and analog type position sensing has been constructed using 360 2 × 3 × 0.4cm BGO detector elements, a light guide 1 × 1.6 × 51cm ID and 90 2cm diameter PM tubes.
Abstract: A detector employing a pseudo-continuous ring of BGO and analog type position sensing has been constructed. It is fabricated using 360 2 × 3 × 0.4cm BGO detector elements, a light guide 1 × 1.6 × 51cm ID and 90 2cm diameter PM tubes. The position of a scintillation event is identified using logic based on a maximum likelihood estimator. A stationary high spatial resolution high detection efficiency tomograph is achieved using this approach.
29 citations
TL;DR: PCR-I has been designed and built to demonstrate the concept of analog coding to provide high resolution positron tomographic images without interpolative motion and Parameters related to dead time and random and prompt scatter coincidences have been studied.
Abstract: PCR-I has been designed and built to demonstrate the concept of analog coding to provide high resolution positron tomographic images without interpolative motion. The instrument uses 360 bismuth germanate (BGO) detectors coupled through a lucite light pipe to 90 phototubes. The measured resolution at the center is 4.8 mm. A straightforward extension of the concept will lead to a tomograph capable of obtaining resolution below 3 mm for low energy positron emitters. The sensitivity of PCR-I is 46 000/s for a 20 cm diameter phantom uniformly filled with 1 μCi/cc of a positron emitter. Parameters related to dead time and random and prompt scatter coincidences have been studied. Phantom measurements demonstrate the resolution and uniformity of PCR-I. Animal studies carried out to date include 18F in rat skeleton, 11C-palmitate and 11C-labeled red cells in dog heart and blood flow, and blood volume in monkey brain using C15O2 and C15O.
22 citations
References
More filters
TL;DR: The ECAT was designed and developed as a positron imaging system capable of providing high contrast, high resolution, quantitative images in two-dimensional (2-D) and tomographic formats and significantly reduces errors caused by motion and detector instability.
Abstract: The ECAT was designed and developed as a positron imaging system capable of providing high contrast, high resolution, quantitative images in two-dimensional (2-D) and tomographic formats. The flexibility in its variety of imaging problems. High (HR), medium (MR), and low (LR) tomographic resolutions are 0.95 +/- 0.1, 1.3 +/- 0.1, and 1.7 +/- 0.1 cm FWHM; high, medium, and low resolutions in 2-D images are 0.85 +/- 0.1, 1.3 +/- 0.1 and 1.7 +/- 0.1, depending on resolution mode employed. ECT system efficiency is 30,100, 15,900, and 9,200 c/sec/muCi/cc with a 20-cm diameter phantom at LR, MR, and HR. Because of the geometric, detector, electronic and shielding design of the system, count-rate capability and linearity are high, with minimum detection of scattered radiation and random coincidence. Measured error agrees well with theoretical statistical predictions down to a level of 1.4% standard deviation. The redundant sampling scheme of this system significantly reduces errors caused by motion and detector instability. Scan times are variable from 10 sec to several min/slice and multiple levels are automatically performed by computer control of patient bed. A variety of human studies illustrate image quality, resolution, and efficiency of both ECT and 2-D imaging mode. Examples of the noninvasive study method have been made possible through development of ECT.
280 citations
TL;DR: The basic imaging properties of the Donner 280-BGO-Crystal positron tomograph were measured and compared with the same system when it was equipped with 280 NaI(T1) crystals, which results in an overall reduction in the fraction of accidental events recorded.
Abstract: The basic imaging properties of the Donner 280-BGO-Crystal positron tomograph were measured and compared with the same system when it was equipped with 280 NaI(T1) crystals. The NaI(T1) crystals were 8 mm × 30 mm × 50 mm deep, sealed in 10 mm wide stainless steel cans. The BGO crystals are 9.5 mm wide × 32 mm × 32 mm deep and as they are not hygroscopic do not require sealed cans. With a shielding gap of 3 cm (section thickness 1.7 cm FWHM) the sensitivity of the BGO system is 55,000 events per sec for 1 ?Ci per cm3 in a 20 cm cylinder of water, which is 2.3 times higher than the NaI(T1) system. For a 200 ?Ci/cm line source on the ring axis in a 20 cm diameter water cylinder, the BGO system records 86% of the scatter fraction and 66% of the accidental fraction of the NaI(T1) system. The lower light yield and poorer time resolution of BGO requires a wider coincidence timing window than NaI(T1); however, the ability to use full-energy pulse height selection with a 2.3-fold improvement in sensitivity results in an overall reduction in the fraction of accidental events recorded. The in-plane resolution of the BGO system is 9-10 mm FWHM within the central 30 cm diameter field, and the radial elongation at the edge of the field in the NaI(T1) system has been nearly eliminated.
119 citations
TL;DR: In this paper, a whole body positron emission transaxial tomograph (PETT III) has been designed, constructed and is presently under clinical evaluation and the design of PETT III spatial resolution and sensitivity of annihilation coincidence detection (ACD), sampling considerations and importance of proper shielding are evaluated.
Abstract: A whole body positron emission transaxial tomograph (PETT III) has been designed, constructed and is presently under clinical evaluation. The design of PETT III spatial resolution and sensitivity of annihilation coincidence detection (ACD), sampling considerations and importance of proper shielding are presented to evaluate some design considerations for an ACD tomograph. Tomographic studies of the brain and heart with human subjects are presented to demonstrate the image quality of PETT III under clinical conditions. (auth)
94 citations
TL;DR: A positron emission tomograph capable of providing seven slices of the human body simultaneously and permits rapid and accurate three-dimensional imaging of the head and body is designed, built, and tested.
Abstract: We designed, built, and tested a positron emission tomograph (PETT IV) capable of providing seven slices of the human body simultaneously. PETT IV utilizes a moving hexagonal array of 48 scintillation detectors placed around the subject. Each detector consists of a cylindrical activated sodium iodide crystal optically coupled to two photomultiplier tubes. The multislice capability is achieved by comparing the light outputs of the two photomultiplier tubes in each detector. The images are displayed either as transverse or as longitudinal tomographic sections. This system provides high sensitivity and resolution, and permits rapid and accurate three-dimensional imaging of the head and body.
80 citations
TL;DR: The performance of a new positron imaging device designed for high resolution dynamic studies on the human brain is described, which is the first to exploit the high photoelectric efficiency of bismuth germanate (BGO) detectors which are almost 3 times as dense as NaI.
Abstract: The performance of a new positron imaging device designed for high resolution dynamic studies on the human brain is described. This unit is the first to exploit the high photoelectric efficiency of bismuth germanate (BGO) detectors which are almost 3 times as dense as NaI. In the first 4 months of clinical use some 300 patient studies have been performed. The detector performance and design criteria are discussed. The principles of operation of the coincidence circuit and computer programs are described. Finally some clinical studies are presented to demonstrate its imaging capabilities.
65 citations