Transit dose of an Ir-192 high dose rate brachytherapy stepping stone

Wong, T, Fernando, W, Johnston, P and Bubb, I 2001, 'Transit dose of an Ir-192 high dose rate brachytherapy stepping stone', Physics in Medicine and Biology, vol. 46, pp. 323-331.

Document type: Journal Article
Collection: Journal Articles

Title Transit dose of an Ir-192 high dose rate brachytherapy stepping stone
Author(s) Wong, T
Fernando, W
Johnston, P
Bubb, I
Year 2001
Journal name Physics in Medicine and Biology
Volume number 46
Start page 323
End page 331
Total pages 8
Publisher IOP Publishing
Abstract Clinical dosimetry for high dose rate (HDR) brachytherapy with a single stepping source generally neglects the transit dose. This study investigates the effects of the transit dose in the target volume of an HDR brachytherapy stepping source. A video method was used to analyse the entrance, exit and the interdwell transit speed of the source for different path lengths and step sizes ranging from 2.5 mm to 995 mm. The transit speed was found to vary with the step size and path length. For the travelled distances of 2.5, 5.0, 10.0, 230 and 995 mm, the average transit speeds were 54, 72, 233, 385 and 467 mm s-1 respectively. The results also show that the manufacturer has attempted to compensate for the effects of interdwell transit dose by reducing the actual dwell time of the source. A well-type chamber was used to determine the dose differences between two sets of measurements, one being the stationary dose only and the other being the sum of stationary and transit doses. Single catheters of active lengths of 20 and 40 mm, different dwell times of 0.5, 1, 2 and 5 s and different step sizes of 2.5, 5 and 10mmwere used in the measurements with the well-type chamber. Most of the measured dose differences between stationary and stationary plus interdwell sourcemovement were within 2%. The additional dose due to the source transit can be as high as 24.9% for the case of 0.5 s dwell time, 10 mm step size and 20 mm active length. The dose difference is mainly due to the entrance and exit source movement but not the interdwell movement.
Copyright notice Copyright 2001 IOP Publishing Ltd
ISSN 0031-9155
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