Surface dose extrapolation measurements with radiographic film

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiological Imaging

Background:

• Accurate surface dose assessment is critical for optimizing radiotherapy outcomes.
• Current methods may require precise calibration and can be complex.
• Understanding dose distribution both inside and outside treatment fields is essential.

Purpose of the Study:

• To evaluate the efficacy of radiographic film and an extrapolation technique for surface dose assessment.
• To compare film-based surface dose measurements with parallel plate ionization chamber results.
• To develop a method for creating a two-dimensional surface dose map.

Main Methods:

• Utilized radiographic film layers and an extrapolation technique for surface dose assessment.
• Employed high-energy X-ray beams in open field configurations.
• Performed measurements for various square field sizes (10 cm, 20 cm, 30 cm).
• Ensured film calibration curves were irradiated with similar field sizes to the experimental films.

Main Results:

• Radiographic film estimation of surface percentage dose was within +/-3% of parallel plate ionization chamber measurements.
• Extrapolated percentage doses at the central axis for 10, 20, and 30 cm fields were 15%, 29%, and 38%, respectively.
• Surface doses outside the treatment field, attributed to scattered electron contamination, were also measured.
• The method produced results relatively uniform across the treatment field.

Conclusions:

• Radiographic film with an extrapolation technique provides an accurate and viable method for surface dose assessment in radiotherapy.
• This technique allows for detailed surface dose mapping, enhancing treatment planning and verification.
• The findings support the use of film-based dosimetry for quality assurance in radiation oncology.