Dosimetric analysis of intracavitary brachytherapy applicators: a practical study

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Intracavitary brachytherapy is a key treatment for gynecological cancers.
• Current dose calculation protocols, like AAPM TG-43, do not fully account for applicator attenuation effects.

Purpose of the Study:

• To investigate the impact of high-dose rate (HDR) brachytherapy applicators on dose distribution.
• To measure the attenuation effects of various brachytherapy applicators on radiation beams.

Main Methods:

• Utilized Gafchromic films and a well-type ionization chamber for in vitro dose measurements.
• Executed treatment plans using varying central tandem angulations and vaginal cylinder diameters.
• Measured charge collection and film dosimetry on applicator assemblies.

Main Results:

• Brachytherapy applicators, specifically central tandems and vaginal cylinders, increase beam attenuation.
• Maximum attenuation observed with a 300° tandem and 35mm vaginal cylinder.
• Minimum attenuation observed with a 0° tandem and 20mm vaginal cylinder.

Conclusions:

• Applicator attenuation significantly affects dose distribution in gynecological brachytherapy.
• Discrepancies between planned and actual doses necessitate consideration of these attenuation effects.
• Accurate dose estimation for targets and organs-at-risk requires accounting for applicator-induced attenuation.