ESTRO 2022 - Abstract Book

S1608

Abstract book

ESTRO 2022

Fig. 2: OAR D1 doses for SLIM with PA of ± {1;3}mm with SAA or NSAA.

Conclusion The SAA algorithm is able to correct the remaining needles to achieve better planning outcomes in terms of plan robustness and sparing of OARs. Its implementation into the workflow is the last missing piece of assembling a fully robotic LRD-BT, which might now enable safe and rapid minimally invasive therapy of liver tumors. [1] P. Aumüller, A. Rothfuss, M. Polednik, Y. Abo-Madyan, M. Ehmann, F.A. Giordano, S. Clausen, Multiple direction needle-path planning and inverse dose optimization for robotic low-dose rate brachytherapy, Zeitschrift für Medizinische Physik. (2021). https://doi.org/https://doi.org/10.1016/j.zemedi.2021.06.003.

PO-1804 Brachytherapy HDR afterloader examination for measurement source position lagging effect

V. Stserbakov 1

1 North-Estonia Medical Center Foundation , Radiotherapy, Tallinn, Estonia

Purpose or Objective Brachytherapy QA programme suppose verification accuracy of applicator library built-in into treatment planning system, which is provided by the manufacture. One method to create the user` own model of brachytherapy applicator is to measure mechanical characteristics of afterloader and applicators separately and based on that to calculate parameters/behavior of joined the afterloader-applicator connection. The purpose of this work is do all required measurements for in clinical use Flexitron (Elekta) afterloader or, as first step/side of QA project, to investigate effect of radiation source position lagging from its nominal d-well place caused by braking strength affected on radiation source movement inside brachytherapy applicator. Materials and Methods In figure you can see the idea of measurement setup based on using manufacture (Flexitron, Elekta) source position check ruler 5. Mechanical resistance to moving of the source 4 through source travelling path makes mandrel 3, inserted into source travel path, which is connected with elastic parts 2 (in this role can be used, for example, rubber strips, springs or whatever) for producing needed increasing resistance force. Later, when source lag was measured, the breaking force scaled by strength measuring tool 1 (for this case we used Scale 500g 0.1g LCD Display Digital Weight Measuring Tool). To perform more accurate measurements for different strength ranges we use 3 types of elastic parts: „hard” – for 0-300 g force; „moderate” – for 0-100 g and „soft”- for 0-30 g. For all these elastic parts types breaking force should be produced in source position range of ruler from ”200” source dwell-position to “300” (i.e. for clinically most popular gynecologic applicators).