[A fast algorithm for homogeneous Ir-192--afterloading irradiation of cylindrical surfaces]

Area of Science:

• Medical Physics
• Radiation Oncology
• Brachytherapy

Background:

• Brachytherapy requires precise dose homogenization around applicators for effective cancer treatment.
• Current methods for Ir-192 afterloading may lack efficiency in dose distribution control.

Purpose of the Study:

• To develop a fast algorithm for dose homogenization on a cylinder mantle around a single straight Ir-192 applicator.
• To derive an approximation formula for predicting dwell time adjustments for uniform dose distribution.

Main Methods:

• Derivation of an approximation formula for dwell time homogenization around linear applicators.
• Calculation of dwell times (tEnd and tMitte) based on applicator and optimization parameters.
• Validation using Thermoluminescent Dosimetry (TLD) measurements and comparison with a commercial planning system.

Main Results:

• The derived formula accurately predicts required dwell time at the applicator end (tEnd), independent of applicator length.
• Central dwell times (tMitte) become largely independent of catheter length and proportional to the optimization radius.
• TLD measurements and planning system comparisons confirm the algorithm's applicability and accuracy.

Conclusions:

• The developed algorithm provides a fast and reliable method for dose homogenization in Ir-192 afterloading.
• It ensures uniform dose distribution even with variations in application length or optimization distance.
• The algorithm serves as an independent tool for verifying brachytherapy treatment planning system results.