Premium
Detector and electronics design considerations for an emission–transmission medical imaging system
Author(s) -
Heanue Joseph A.
Publication year - 1996
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.597838
Subject(s) - cadmium zinc telluride , detector , collimator , photon counting , optics , data acquisition , transmission (telecommunications) , semiconductor detector , energy (signal processing) , physics , materials science , computer science , telecommunications , operating system , quantum mechanics
Capable of simultaneous x‐ray and nuclear‐medicine imaging, the emission–transmission computed tomography (ETCT) system is a unique approach to the problems of quantitation and localization in radionuclide measurements. Several potential improvements to the ETCT front‐end are assessed in terms of their benefit for quantitative measurements. First, a “triple‐mode” readout circuit has been designed to improve scatter rejection without sacrificing flexibility. The circuit can be operated in three modes: a slow pulse‐counting mode for detection of radionuclide events with excellent energy resolution, a fast pulse‐counting mode for simultaneous acquisition of emission and transmission data or for collection of dual‐energy x‐ray data at high rates with moderate energy resolution; and current‐mode operation for acquisition of x‐ray transmission data. Next, cadmium‐telluride and cadmium‐zinc‐telluride detectors are evaluated. These materials offer room‐temperature operation, large size, and good stopping efficiency; however, they also exhibit limited energy resolution and poor charge collection. It is shown that their most serious limitation is low photopeak efficiency. Thus, methods for reduction of charge‐trapping losses are proposed. Finally, the benefits of excellent scatter rejection are assessed. Although scatter introduces a measurable error, the effects of attenuation and collimator blur are more significant. In addition, at an energy resolution of several keV, the error due to scatter is small compared to the statistical uncertainty in quantitative measurements.