¹⁰³Pd strings: Monte Carlo assessment of a new approach to brachytherapy source design

Abstract

By design, the CivaString and CivaThin sources have novel dosimetric characteristics in comparison to Ti-encapsulated (103)Pd seeds. The dosimetric characterization has determined the reasons for these differences through analysis using Monte Carlo-based radiation transport simulations.

A directional 103Pd brachytherapy device: Dosimetric characterization and practical aspects for clinical use

“…The author has BT dosimetry experience with this user code (18), recently for 103 Pd sources (8,19), and also with MCNP6 (20). In general, the simulation approach described in detail by Rivard for BT sources was followed (21).…”

“…To characterize the CivaSheet dose distribution as a combination of CivaDots for practical treatment planning (37), tests of the suitability of single-source dose superposition were made in a similar manner as that previously reported (8). Specific to the CivaSheet, 6×6, 6×12, and 6×18 arrays of CivaDots were modeled and the dose distributions were compared to those obtained from the sum of individual CivaDots located at the same positions as in the arrays.…”

“…The focus is on estimating the uncertainty in dose calculations at depths of 0.5 cm and 1.0 cm as well as for g MC (0.5 cm), s K , and Λ. For brevity, details are given only for some of the uncertainty components because the majority of the items have been previously examined for the 103 Pd CivaString ® and were assumed to be applicable to the 103 Pd CivaSheet (8). …”

“…While dose anisotropy for a single source does not correspond to dose uniformity for a volumetric implant, it has been shown that sources with less dose anisotropy can improve target dose uniformity while minimizing the irradiation of adjacent healthy tissues (6). Taking this concept further, elongated sources have been developed (7,8) to address dose uniformity for volumetric targets.…”

Physics: Low-Energy Brachytherapy Physics

“…An 8 % change of the DRC of the source was determined by Monte Carlo calculations, while only small relative dose distribution parameters were identified. Rivard et al calculated the TG43 parameters using the Monte Carlo method for a new Pd-103 source design, with the source available in lengths from 1.0 cm up to 6.0 cm, at 1.0 cm steps [26]. They found minimal variations of the normalized source strength as a function of source lengths.…”