| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2000: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1999: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
In order to measure the spatial dose distribution in the immediate vicinity of brachytherapy sources, we have newly developed a wide and high-resolution themoluminescent (TL) sheet, which is a teflon homogeneously mixed with small powders of thermoluminescent BaSO_4 : Eu doped, and its spatial dose distribution readout system.
In this work, the spatial resolution and accuracy of this TL sheet were investigated.
1. The spatial resolution of the TL sheet was 62μm corresponding to 8.1 line pairs/mm. Also, the spatial resolution was 13 line pairs/mm measured at the 5% level of the modulation transfer function. This suggests that TL sheet is useful to measure the spatial dose distribution near in the radiation field with large dose gradients over small area.
2. With brachytherapy sources I-125 (Model 6711 and Model 6702), and Pd-103 (Model 200) of low energy photon emitters , the radial dose functions and anisotropy constants with TL sheet were agreed well with those with LiF-TLD.Anisotropy functions on brachytherapy sources could easily be mapped using TL sheet. Also, anisotropy functions were symmetric on the long axes of sources, and clearly delineated the dosimetric characteristics of the source edges.
3. As a result, this high resolutional TL sheet may provide a convenient and accurate means of measuring the dose distribution near brachytherapy sources, because the TL sheet has been found to have a linear response with a very wide dynamic range from at least 0.002 cGy to 5000 cGy absorbed dose.
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