Thick phosphor screens for on‐line portal imaging
作者:
B. Wowk,
S. Shalev,
期刊:
Medical Physics
(WILEY Available online 1998)
卷期:
Volume 21,
issue 8
页码: 1269-1276
ISSN:0094-2405
年代: 1998
DOI:10.1118/1.597209
出版商: American Association of Physicists in Medicine
数据来源: WILEY
摘要:
Gd2O2S phosphor screens between 250 and 1000 mg/cm2thick were evaluated for use in megavoltage imaging systems. The phosphor layers were placed on brass plates ranging from 1 to 5 mm thick, each with and without an optical back reflector (white paint). Light output and spatial resolution were measured at 6‐ and 23‐MV x‐ray energies. Light output was found to increase linearly with phosphor thickness up to 500 mg/cm2, reaching a plateau at 1000 mg/cm2. Spatial resolution [modulation transfer function (MTF)] decreased exponentially with phosphor thickness up to 750 mg/cm2, where a minimum was reached. The variation of MTF with phosphor thickness was found to obey a simple empirical relation.
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