PHOTON ENERGY-DEPENDENCE OF THE SENSITIVITY OF RADIOCHROMIC FILM AND COMPARISON WITH SILVER-HALIDE FILM AND LIF TLDS USED FOR BRACHYTHERAPY DOSIMETRY
PHOTON ENERGY-DEPENDENCE OF THE SENSITIVITY OF RADIOCHROMIC FILM AND COMPARISON WITH SILVER-HALIDE FILM AND LIF TLDS USED FOR BRACHYTHERAPY DOSIMETRY
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DOI：
10.1118/1.596630
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发表时间：
1991-07-01
期刊：
影响因子：
3.8
通讯作者：
MCLAUGHLIN, WL
中科院分区：
文献类型：
--
作者：
MUENCH, PJ;MEIGOONI, AS;MCLAUGHLIN, WL
有一种新的辐射变色膜，是一种高度均匀的薄（100 μ m）探测器，其敏感层（6 μ m厚）在暴露于电离辐射时通过染料聚合而不经处理从无色变为蓝色。由于近距离放射治疗源周围的剂量梯度是陡峭的，由薄膜剂量测定提供的高空间分辨率是优于其他探测器（诸如热释光剂量计（TLD））的优势。这比较了GafChromic胶片、银验证胶片（Kodak X-Omat V胶片）和氟化锂TLD（Harshaw）在近距离放射治疗中感兴趣的光子能量范围28 keV至1.7 MeV内的灵敏度的光子能量依赖性。当有效光子能量从1710 keV（4-MV X射线）降低到28 keV（60-kV X射线，2-mm Al滤光片）时，观察到辐射变色膜的灵敏度降低约30%。相比之下，验证膜的灵敏度提高了980%，LiF TLD的灵敏度提高了41%。辐射变色胶片的灵敏度随光子能量的变化比银胶片小得多，与LiF TLD的灵敏度相似，但方向相反。辐射变色胶片，如LIF TLD，在低于127 keV时不表现出银胶片所表现出的剧烈灵敏度变化。剂量分布在附近的高活性（370 GBq）近距离治疗的Ir-192源已被映射使用辐射变色膜，并说明这种新技术的适用性，近距离治疗剂量测定。
There is a new radiochromic film, a highly uniform, thin (100-mu-m) detector whose sensitive layer (6-mu-m thick) changes from colorless to blue by dye polymerization without processing, upon exposure to ionizing radiation. Because the dose gradients around brachytherapy sources are steep, the high spatial resolution offered by film dosimetry is an advantage over other detectors such as thermoluminescent dosimeters (TLDs). This compares the photon energy dependence of the sensitivities of GafChromic film, silver halide verification film (Kodak X-Omat V Film), and lithium fluoride TLDs (Harshaw), over the photon energy range 28 keV to 1.7 MeV, which is of interest in brachytherapy. Sensitivity of the radiochromic film is observed to decrease by about 30% as effective photon energy decreases from 1710 keV (4-MV x rays) to 28 keV (60-kV x rays, 2-mm Al filter). In contrast, the sensitivity of verification film increases by 980% and that of LiF TLDs increases by 41%. The variation of the sensitivity of radiochromic film with photon energy is considerably less than that for silver halide film and similar to that for LiF TLDs, but in the opposite direction. Radiochromic film, like LIF TLDs, does not exhibit the drastic sensitivity changes below 127 keV that silver halide film exhibits. Dose distribution in the immediate vicinity of a high activity (370 GBq) brachytherapy Ir-192 source has been mapped using radiochromic film and is presented to illustrate the applicability of this new technology to brachytherapy dosimetry.