ESTRO 2024 - Abstract Book

S328

Beachytherapy - Physics

ESTRO 2024

Figure. Technique of measurements. A – View of program VeriSoft 8.0 during collecting signal in some dwell position of Ir-192 radiation source. B – Fixation of Venezia 22 (Flexitron, Elekta) applicator on 2D-dimentional array. C – Concept of source position precise calculation based on 3x3 detectors readings around over all array maximal reading detector.

Results:

The table shows the measured positions of the 1st and 2nd channels of radiation sources of the Venezia22 brachytherapy applicators and their comparison with the positions of the library of applicator sources.

We found the accuracy of this method to be quite good (~0.1mm). This conclusion can be drawn based on repeated measurements of the same applicator with a slightly random misalignment of the fixation of the applicator on the matrix (offset ~ 1 mm), when the resulting result (the overall arrangement of 21 source positions) was an exact copy of the first measurement.

The described technique “opens our eyes” to interesting options for the movement of the source inside the applicator, reflecting the unpredictable nature of friction in the channel:

1. Step size of the source dwell-stop point can differ (~±50%) from 1 mm step size of expected library value. 2. Overall angular working range (pos“280”- pos.”300”) of Venezia22 channel can be longer or shorter by factor 1-2 mm than expected by library.

Mismatching of measured-library dwell-positions are less than declared 2 mm, but uncomfortably close to this tolerance value.

Table. Measured positions of radiation source 1 and 2 channels of Venezia22 brachytherapy applicators and its mismatching with applicator source library positions.