Application of Scatter-to-primary Dose Ratio to Proton Dosimetry

概要

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The dose distribution of proton beams with depth exhibits a strong Bragg peak at the end of the range, beyond which the dose rapidly falls to zero. These qualities make these beams particularly suitable for tumors situated near critical organs, where there is a high demand for accurate dose delivery. In proton dosimetry, we studied the scatter-to-primary dose ratio(SPR), which is used for dose evaluation in high-en-ergy photon beams. The formula for SPR calculation was developed by Ceberg et al. The maximum energy of the proton beam used in this study was 70 MeV, produced by an isochronous cyclotron. We assumed that SPR could by separated into longitudinal and lateral components that are dependent on depth(Z)and field radius(R), such that SPR(Z, R)=SPR(Z)・SPR(R). In particular, the effect of the longitudinal component on the shift of the spread-out Bragg peak(SOBP)was examined. The results showed that SPR(Z)of the lonitudinal component decreased with decreasing water depth and SPR(R) of the lateral component decreased with decreasing field size.
公益社団法人日本放射線技術学会の論文
2000-04-20