A modified geometric factor approach to internal gamma ray dosimetry

Area of Science:

• Medical Physics
• Radiation Dosimetry

Background:

• Conventional geometric factor approach in internal gamma-ray dosimetry yields significant errors at low energies.
• The "effective absorption coefficient" is often used irrespective of source energy, leading to inaccuracies.

Purpose of the Study:

• To modify the geometric factor approach for increased accuracy in internal gamma-ray dosimetry.
• To extend the applicability of the method to low-energy gamma-ray sources.
• To maintain the inherent simplicity of the geometric factor method.

Main Methods:

• Replaced the "effective absorption coefficient" with energy-appropriate attenuation coefficients.
• Incorporated the effects of multiple scattering using a point source build-up factor.
• Applied the modified method to the dosimetry of a sphere.

Main Results:

• The modified method shows excellent agreement with Monte Carlo computations at higher energies.
• A departure of only around 15% was observed at lower energies, compared to 400% error with the conventional method.

Conclusions:

• The modified geometric factor approach significantly enhances accuracy in internal gamma-ray dosimetry, particularly at low energies.
• This improved method offers a simpler and more accurate alternative to conventional techniques for various source geometries.