ESTRO 2023 - Abstract Book

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ESTRO 2023

Figure. Scheme of setup for measurement of the force braking down the dummy source when it moves inside the applicator. 1- brachytherapy applicator; 2- dummy source; 3- holder for applicator; 4- load cell of digital scale; 5- Digital scales 0.01-200g, MH-200, fixated on chamber holder block of positioning assembly; 6- dummy cable; 7- depth positioning assembly of water phantom WP-3840 (CNMC); 8- manual/remote motor drive; 9- ruler; 10- pointer; A- “cable free space” zone. Results On the table you can see measured braking force values for some popular brachytherapy applicators. Coordinate of dummy source, when it breaks against end of canal inside applicator, was chosen as “10 cm” coordinate. In this point resistance force starts dramatically increase. Coordinate “0 cm” corresponds position of dummy source when it located on applicator entrance (for Ring applicator). If we compare applicators between each other, for the region 9-10 cm we have got unexpected results: braking force for new type applicator (Venezia) is ~2 times higher than for old type applicator (Ring), although, as it would seems that, the idea of developing new generation of applicators was to reduce resistance force inside applicator in order to reduce uncertainty in source position.

Table. Measured braking force values for some brachytherapy applicators (Ring, Venezia)

Conclusion Measured values for source cable strength inside applicator are essential basic data for calculation/creation user’ model of library applicator in quality assurance procedure for verification manufacture applicator library files in clinical QA programme. Unexpected results for Venezia applicator can stimulate introducing enhancements in construction of applicator.

PO-2165 Measurement of the temperature dependence calibration factor of PTW INVIVO rectum probe type 9112

V. Stserbakov 1

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

Purpose or Objective