Determination of transit dose profile for a ¹⁹²Ir HDR source

Abstract

The present work demonstrated that the transit dose correction based on average source speed fails to accurately correct the dose, indicating that the correct speed profile should be considered. The impact on total dose due to the transit dose correction near the dwell positions is significant and should be considered more carefully in treatments with high dose rate, several catheters, multiple dwell positions, small dwell times, and several fractions.

HDR 192Ir source speed measurements using a high speed video camera

“…The transit dose component of a brachytherapy source movement from the safe to the dwell positions, between the dwell positions, and when returning to the safe has been studied previously, [1][2][3][4][5][6][7] reporting differences up to a factor of 10 for the source speed for the same afterloader. 8 The effect of these differences on the transit dose component for clinical brachytherapy treatments performed with a HDR 192 Ir source was evaluated recently.…”

Impact of source position on high-dose-rate skin surface applicator dosimetry

“…HDR source transit dose has long been recognized and explored by many researchers using various methods [26,38–42]. Among them, Fonseca, et al have extensively evaluated the transit dose of the 192 Ir HDR afterloader, with respect to the source speed profiles, for a more realistic dose correction [38–40]. For the skin applicator however only one dwell position is used and the absolute transit dose contribution is a function of source activity only.…”

Development of a phantom to validate high‐dose‐rate brachytherapy treatment planning systems with heterogeneous algorithms

“…13 A single dwell position was selected in this work, as multiple dwell positions tend to increase the contribution of the 192 Ir transit dose. 43 In order to verify the accuracy of the HDR 192 Ir source for the specific dwell position, preliminary verifications with radiochromic film were performed. 44 The results demonstrated that our HDR afterloading system has a precision lower than 1 mm in the source positioning for a single dwell positioning case.…”

“…Following a similar approach used by Fonseca et al, 43 two separate simulations were done, air-kerma-strength (S k ) and the dose-to-water rate at 1 cm at 90 • . 2,3 All simulations were done according to the methodology proposed by Ballester et al 52 We obtained the value (1.111 ± 0.002) cGy.h −1 .U −1 which agrees within −0.49% with the updated consensus dose rate constant for the GammaMedplus iX source.…”