TLD extrapolation for skin dose determination in vivo

Area of Science:

• Medical Physics
• Radiation Oncology
• Dermatology

Background:

• Accurate prediction of skin reactions in radiation therapy necessitates understanding radiation dose distribution within human skin.
• Thermoluminescence dosimetry (TLD) is a key technique for measuring absorbed radiation doses.

Purpose of the Study:

• To develop and validate a method for measuring skin entrance and exit doses using TLDs.
• To identify factors influencing skin dose during patient irradiation, specifically in breast irradiation.

Main Methods:

• Utilized thermoluminescence dosimeters (TLDs) of varying thicknesses for dose extrapolation and interpolation.
• Designed a specialized TLD holder for in-vivo patient measurements during radiation treatment.
• Conducted a pilot study on 18 breast cancer patients undergoing irradiation.

Main Results:

• The TLD measurement system demonstrated a day-to-day variability of +/-7%.
• The angle of incidence of the radiation beam was identified as the most significant factor affecting skin entrance dose.
• Beam exit dose was consistently higher, contributing approximately 50% more to the surface dose than the entrance dose.

Conclusions:

• The developed TLD method provides reliable in-vivo measurements of skin doses during radiation therapy.
• Understanding the influence of beam angle and exit dose is critical for optimizing treatment planning and minimizing skin toxicity.
• This dosimetry approach aids in predicting and managing patient skin reactions.