Program Information

Enhanced Radiation Attenuation with Multi-Layer Foils

L Warmington*, Y Watanabe , University of Minnesota, Minneapolis, MN

Presentations

SU-E-T-151 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:
To evaluate the effect of increasing the number of thin high Z foils on the dose enhancement and the overall radiation attenuation with a 24MV photon beam.

Methods:
DOSXYZnrc was used to perform Monte Carlo simulations of multi-layer lead foil configurations. The foil size was 7cm x 7cm. and the foil thickness was adjusted to give a combined thickness of 1mm. The number of foils used was 4, 6, 8, and 10. The separation between foils was also varied from 3 to 9 mm. The Mohan 24MV energy spectrum was used as a photon source. The field size was 5cm x 5cm and SSD was 100 cm. The phantom size was 16cm x 16cm x 28cm. The number of histories ranged from 1 to 2 billion. The percentage difference of the dose between the medium with foils and the homogeneous water was computed along the beam axis. The minimum dose enhancement and the change of integrated dose between the foils were determined.

Results:
Increasing the number of foils resulted in a decrease in the minimum dose enhancement. The highest dose region occurred in the last section for the 4 and 6 foil cases, whereas the 8 and 10 foil configurations showed the maximum dose region towards the center of the foil group. Increasing the number of foils increased the total integrated dose between foils. For example, the total integrated dose increase between the first and the last foils with a 3mm foil separation were 34.2, 43.4, 57.4, and 64.7% for 4, 6, 8 and 10 foils, respectively.

Conclusion:
This work showed the degree of dose enhancement around multiple thin lead foils. The results suggest that the total attenuation of photon beam can be increased by increasing the number of foils with a fixed total foil thickness.

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