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Proceedings Paper

Electronic portal imaging using Cherenkov radiation
Author(s): Isuru C. Silva; G. Pang
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Paper Abstract

Most electronic portal imaging devices (EPIDs) developed so far use a Cu plate/phosphor screen to absorb x rays. The main problem with this approach is that the Cu plate/phosphor screen must be thin (~ 2 mm) in order to obtain a high spatial resolution, resulting in a low quantum efficiency (QE) for megavoltage (MV) × rays (typically 2-4%). In addition, the phosphor screen contains high atomic number (high-Z) materials, resulting in an over-response of the detector to low energy x rays in dosimetric verification. Our overall goal is to develop a new high QE MV x-ray detector made of a low-Z material for both geometric and dosimetric verification in radiotherapy. Our approach is based on radiation-induced light (Cherenkov radiation) in optical fibers to convert x-ray energy into light. With our approach, a thick (~ 10-30 cm) fiber-optic taper (FOT) consisting of a matrix of optical fibers aligned with the incident x rays is used to replace the thin Cu plate/phosphor screen to dramatically improve the QE. In this work, we demonstrated that the predominant light source in optical fibers under irradiation of a MV beam is indeed Cherenkov radiation, and thus validated the feasibility of using Cherenkov radiation as the primary light source in our proposed Cherenkov detector. A prototype Cherenkov detector array was also built and images were obtained.

Paper Details

Date Published: 18 March 2008
PDF: 11 pages
Proc. SPIE 6913, Medical Imaging 2008: Physics of Medical Imaging, 69130A (18 March 2008); doi: 10.1117/12.772023
Show Author Affiliations
Isuru C. Silva, Sunnybrook Health Sciences Ctr., Univ. of Toronto (Canada)
G. Pang, Sunnybrook Health Sciences Ctr., Univ. of Toronto (Canada)
Odette Cancer Ctr., Univ. of Toronto (Canada)

Published in SPIE Proceedings Vol. 6913:
Medical Imaging 2008: Physics of Medical Imaging
Jiang Hsieh; Ehsan Samei, Editor(s)

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