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Rapid portal imaging with a high‐efficiency, large field‐of‐view detector
Author(s) -
MoslehShirazi M. A.,
Evans P. M.,
Swindell W.,
SymondsTayler J. R. N.,
Webb S.,
Partridge M.
Publication year - 1998
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 - 10.1118/1.598443
Subject(s) - isocenter , imaging phantom , image quality , optics , image guided radiation therapy , detector , detective quantum efficiency , image resolution , physics , medical imaging , frame rate , field of view , cone beam computed tomography , beam (structure) , nuclear medicine , computer science , computer vision , artificial intelligence , medicine , computed tomography , image (mathematics) , radiology
The design, construction, and performance evaluation of an electronic portal imaging device (EPID) are described. The EPID has the same imaging geometry as the current mirror‐based systems except for the x‐ray detection stage, where a two‐dimensional (2D) array of 1 cm thick CsI(Tl) detector elements are utilized. The ∼ 18 % x‐ray quantum efficiency of the scintillation detector and its 30 × 40 cm 2field‐of‐view at the isocenter are greater than other area‐imaging EPIDs. The imaging issues addressed are theoretical and measured signal‐to‐noise ratio, linearity of the imaging chain, influence of frame‐summing on image quality and image calibration. Portal images of test objects and a humanoid phantom are used to measure the performance of the system. An image quality similar to the current devices is achieved but with a lower dose. With ∼ 1 cGy dose delivered by a 6 MV beam, a 2 mm diam structure of 1.3% contrast and an 18 mm diam object of 0.125% contrast can be resolved without using image‐enhancement methods. A spatial resolution of about 2 mm at the isocenter is demonstrated. The capability of the system to perform fast sequential imaging, synchronized with the radiation pulses, makes it suitable for patient motion studies and verification of intensity‐modulated beams as well as its application in cone‐beam megavoltage computed tomography.