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Performance characterization of a MVCT scanner using multislice thick, segmented cadmium tungstate‐photodiode detectors
Author(s) -
Kirvan P. F.,
Monajemi T. T.,
Fallone B. G.,
Rathee S.
Publication year - 2010
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 - 10.1118/1.3273032
Subject(s) - detective quantum efficiency , optics , imaging phantom , tomotherapy , detector , nuclear medicine , scanner , image resolution , dosimetry , physics , dot pitch , cone beam computed tomography , dosimeter , radiation , image quality , pixel , medicine , radiology , computer science , radiation therapy , computed tomography , artificial intelligence , image (mathematics)
Purpose Megavoltage computed tomography (MVCT) and megavoltage cone beam computed tomography (MVCBCT) can be used for visualizing anatomical structures prior to radiation therapy treatments to assist in patient setup and target localization. These systems are less susceptible to metal artifacts and provide better CT number linearity than conventional CT scanners. However, their contrast is limited by the properties of the megavoltage photons and the low detective quantum efficiency (DQE) of flat panel detector systems currently available. By using higher DQE, thick, segmented cadmium tungstate detectors, the authors can improve the low contrast detectability of a MVCT system. This in turn would permit greater soft tissue visualization for a given radiation dose, allowing MVCT to be used in more clinical situations. Methods This article describes the evaluation of our prototype system that uses thick, segmented detectors. In order to create images using a dose that would be acceptable for day to day patient imaging, the authors evaluated their system using the low intensity bremsstrahlung component of a 6 MeV electron beam. The system was evaluated for its uniformity, high contrast resolution, low contrast detectability, signal to noise ratio, contrast to noise ratio, and CT number linearity. Results The prototype system was found to have a high contrast spatial resolution of about 5 line pairs per cm, and to be able to visualize a 15 mm 1.5% contrast target with 2 cGy of radiation dose delivered.SNR 2vs radiation dose and mean pixel value vs electron density curves were linear. Conclusions This prototype system shows a large improvement in low contrast detectability over current MVCBCT systems.