ESTRO 2022 - Abstract Book

S1609

Abstract book

ESTRO 2022

Figure. Scheme of setup for measurement of source position lagging effect. 1- Strength measuring tool; 2 – elastic parts; 3 – needle mandrel; 4 – radiation source; 5 – source position check ruler; 6 – source cable; 7 – afterloader. Results On the table you can see averaged value for Δ (radiation source position deviation/lag from its nominal location) measured with 3 different hardness of elastic parts, which correspond ≤ 30g, ≤ 100g and ≤ 300g braking force ranges. As you see, lag effect is more distinctive ( Δ = 1.5 mm) for the first 20 g braking strength, and for the rest part its approximately linear up to “obstruction” source cable strength value ~300 g with rate 0.9 mm/100 g. Source cable strength range values (as we now preliminary estimate) for Ring ( ≤ 50g) and Venezia ( ≤ 120g) applicators are mentioned too in the table.

Table. Measured Δ values (radiation source position deviation/lag from its nominal place) in mm. Ù 50 g, Ù100 g - braking strength ranges of Ring and Venezia applicators correspondingly. Conclusion Measured values for source position lag effect for known cable strength are essential basic data for calculation/creation user’ model of library applicator in quality assurance procedure for verification manufacture applicator library files.

PO-1805 Dwell positions of the source in Ring Applicator (“z-coordinate”) in HDR brachytherapy commissioning

V. Stserbakov 1 , A. Tsizik 1 , N. Saveljev 1

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

Purpose or Objective For creating adapted to clinical user applicator library (Oncentra Brachy 4.6 treatment planning system, Flexitron afterloading machine) to collect data about behaviour/traveling position of the Ir-192 radiation source inside source guiding channel of most questionable Ring Applicator Ø 26 mm. Materials and Methods Technique of autoradiography, when X-ray film have been used to visualize actual position of the radiation source inside the applicator source travel path, in direction parallel to tandem (“z-coordinate”, Fig., Z+), in this case do not applicable for technical reason. Thus for the solving this problem the manipulation/handling with dummy source inside source travel