[Dose distribution of pendulum fields in the field border plane].

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Physics

Background:

• Understanding isodose distributions is crucial for effective radiotherapy.
• Pendulum irradiation techniques offer unique dose delivery advantages.
• Accurate dose assessment in off-central planes is essential for treatment safety.

Purpose of the Study:

• To investigate and compare isodose distributions for various pendulum irradiation methods.
• To analyze dose variations in planes parallel to the central ray plane at field borders.
• To evaluate the impact of monoaxial and biaxial pendulum techniques on dose distribution.

Main Methods:

• Utilized calculations from the SIDOS-U2 program.
• Performed LiF (lithium fluoride) thermoluminescent dosimetry measurements.
• Conducted experiments within a cylindrical water phantom.
• Examined dose distributions in planes intersecting field borders at the central axis depth.

Main Results:

• Dose values in border planes differ significantly between pendulum irradiation methods compared to the central ray plane.
• Monoaxial pendulum methods at small angles resulted in maximum border plane doses less than 50% of the central plane maximum.
• The relative maximum dose in the border plane shifted to greater depths with monoaxial methods.
• Biaxial pendulum methods showed maximum border plane doses potentially exceeding 50% of the central plane maximum.

Conclusions:

• Pendulum irradiation method choice critically influences off-axis dose distribution.
• Monoaxial pendulum techniques may spare tissues adjacent to the primary beam at the border plane.
• Biaxial pendulum techniques can deliver substantial doses to tissues at the border plane, requiring careful consideration in treatment planning.