Oblique Surface Dose Calculation in High-Energy X-ray Therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Radiation therapy can cause severe skin damage due to high incident radiation oblique to the skin surface.
• Accurate assessment of absorbed radiation dose is essential for predicting and mitigating skin damage.

Purpose of the Study:

• To determine dose variation and angular dependence of small optically stimulated luminescence dosimeters (OSLDs) for accurate oblique surface dose calculation.
• To derive a new calculation formula for oblique surface dose using OSLDs.

Main Methods:

• Utilized a high-energy (4 MV) X-ray system and small OSLDs for personal exposure dosimetry.
• Quantified dose variation using the coefficient of variation.
• Measured angular dependence by comparing dose ratios in vertical and oblique directions.

Main Results:

• The maximum coefficient of variation for 66 small-field OSLDs was 1.71%, indicating minimal dose variation.
• The maximum angular dependence (dose ratio) was 1.37.
• A new equation was derived, calculating oblique surface dose within an error range of -7.7% to 5.1%.

Conclusions:

• The developed OSLD dosimetry method and calculation formula provide accurate assessment of oblique surface radiation doses.
• This advancement can lead to better prediction and management of radiation-induced skin damage in patients undergoing radiation therapy.