Choice of material for HVL measurements in megavoltage x-ray beams.
The relative sensitivity of the half-value layer (HVL) method as a quality index for megavoltage x-ray beams is examined by theoretical calculation and experimental measurements for 4-, 6-, 10-, and 25-MV x-ray beams. It is shown that lower atomic number materials are more sensitive to beam quality changes than higher atomic number materials, and that aluminum is a reasonable choice of material for HVL measurements in megavoltage x-ray beams. Further, it was found that the HVL in aluminum or polystyrene is a more sensitive index of spectral quality than the ionization ratio method, recommended by recent dosimetry protocols.
D000535:Aluminum; D004583:Electrons; D005374:Filtration; D006801:Humans; D007854:Lead; D008953:Models, Anatomic; D011137:Polystyrenes; D011827:Radiation; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000379:methods*
D011137:Polystyrenes; D007854:Lead; D000535:Aluminum