lutetium-orthosilicate has been researched along with cadmium-telluride* in 1 studies
1 other study(ies) available for lutetium-orthosilicate and cadmium-telluride
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Effects of system geometry and other physical factors on photon sensitivity of high-resolution positron emission tomography.
We are studying two new detector technologies that directly measure the three-dimensional coordinates of 511 keV photon interactions for high-resolution positron emission tomography (PET) systems designed for small animal and breast imaging. These detectors are based on (1) lutetium oxyorthosilicate (LSO) scintillation crystal arrays coupled to position-sensitive avalanche photodiodes (PSAPD) and (2) cadmium zinc telluride (CZT). The detectors have excellent measured 511 keV photon energy resolutions (=12% FWHM for LSO-PSAPD and =3% for CZT) and good coincidence time resolutions (2 ns FWHM for LSO-PSAPD and 8 ns for CZT). The goal is to incorporate the detectors into systems that will achieve 1 mm(3) spatial resolution ( approximately 1 mm(3), uniform throughout the field of view (FOV)), with excellent contrast resolution as well. In order to realize 1 mm(3) spatial resolution with high signal-to-noise ratio (SNR), it is necessary to significantly boost coincidence photon detection efficiency (referred to as photon sensitivity). To facilitate high photon sensitivity in the proposed PET system designs, the detector arrays are oriented 'edge-on' with respect to incoming 511 keV annihilation photons and arranged to form a compact FOV with detectors very close to, or in contact with, the subject tissues. In this paper, we used Monte Carlo simulation to study various factors that limit the photon sensitivity of a high-resolution PET system dedicated to small animal imaging. To optimize the photon sensitivity, we studied several possible system geometries for a fixed 8 cm transaxial and 8 cm axial FOV. We found that using rectangular-shaped detectors arranged into a cylindrical geometry does not yield the best photon sensitivity. This is due to the fact that forming rectangular-shaped detectors into a ring produces significant wedge-shaped inter-module gaps, through which Compton-scattered photons in the detector can escape. This effect limits the center point source photon sensitivity to <6% for a cylindrical system with rectangular-shaped blocks, 8 cm diameter and 8 cm axial FOV, and a 350-650 keV energy window setting. On the other hand, if the proposed rectangular-shaped detectors are arranged into an 8 x 8 x 8 cm(3) FOV box configuration (four detector panels), there are only four inter-module gaps and the favorable distribution of these gaps yields >8% photon sensitivity for the LSO-PSAPD box configuration and >15% for CZT box geometry, using a 350-65 Topics: Animals; Cadmium Compounds; Computer Simulation; Crystallization; Equipment Design; Image Processing, Computer-Assisted; Lutetium; Monte Carlo Method; Photons; Positron-Emission Tomography; Sensitivity and Specificity; Silicates; Tellurium; Transducers; Zinc | 2007 |