Absorbed dose delivered by alpha particles calculated in cylindrical geometry.

Area of Science:

• Medical Physics
• Radiation Dosimetry
• Computational Biology

Background:

• Accurate dosimetry is crucial for understanding radiation effects in biological tissues.
• Previous calculations of alpha particle dosimetry in the tracheobronchial tree relied on data from NRC and ICRP.
• Investigating the impact of different stopping power models (water vs. tissue) is important for refining dosimetry calculations.

Purpose of the Study:

• To develop a semi-analytical method for calculating alpha particle absorbed dose in cylindrical geometries.
• To reproduce established dose conversion coefficients and absorbed fractions for the tracheobronchial tree.
• To compare the effects of using water stopping power versus tissue stopping power.

Main Methods:

• Calculated linear stopping powers for alpha particles in tissue and air.
• Established stopping power dependence on traveled distance.
• Developed a geometry model considering near-wall and far-wall cases.
• Utilized numerical integration of a triple integral to determine total energy imparted.

Main Results:

• The absorbed dose was found to be independent of the sphere diameter used in calculations.
• Results showed good agreement with previously published data from NRC and ICRP66.
• The semi-analytical method successfully reproduced dose conversion coefficients and absorbed fractions.
• Using tissue stopping power resulted in slightly lower dose conversion coefficients in the bronchial region compared to water stopping power.

Conclusions:

• The developed semi-analytical method provides a reliable approach for alpha particle dosimetry in cylindrical geometries.
• The findings validate existing dosimetry data for the tracheobronchial tree.
• Tissue stopping power should be considered for more accurate dosimetry in bronchial tissues.