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Figure 1 Segmental distribution of radiation dose. (a) Segment of full-dose irradiation with >90% of reference dose at 1-mm vessel depth (= reference isodose length [RIL]). (b) Segment between end of injury and end of RIL receiving full-dose radiation with >90% of reference dose at 1-mm vessel depth (= safety margin). (c) Segment of dose fall-off with 10% to 90% of reference dose at 1-mm vessel depth (= edge of irradiation). This segment was assumed 4.5, 2.0, and 2.5 mm proximal and distal to the end of the active source for ¹⁹²Ir, ³²P, and ⁹⁰Sr/Y application, respectively (11). (d) Segment of negligible irradiation with <10% of reference dose at 1 mm vessel depth.