1. Performance characterization of a MVCT scanner using multislice thick, segmented cadmium tungstate-photodiode detectors
- Author
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Satyapal Rathee, B. G. Fallone, P. F. Kirvan, and T. T. Monajemi
- Subjects
Physics ,Cone beam computed tomography ,business.industry ,General Medicine ,Iterative reconstruction ,Flat panel detector ,3. Good health ,030218 nuclear medicine & medical imaging ,Megavoltage Cone Beam Computed Tomography ,Detective quantum efficiency ,03 medical and health sciences ,0302 clinical medicine ,Optics ,Contrast-to-noise ratio ,030220 oncology & carcinogenesis ,Dosimetry ,business ,Nuclear medicine ,Image resolution - Abstract
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 wasmore » 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{sup 2} vs 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.« less
- Published
- 2009