Corrected relationship between %dd(10)x and stopping-power ratios.
Kosunen and Rogers [Med. Phys. 20, 1181-1188 (1993)] presented a linear equation relating the Spencer-Attix water/air stopping power ratio to %dd(10)x, the photon component of the percentage depth-dose at 10 cm depth for a 10x10 cm2 field on the surface of a phantom at SSD=100 cm. This relationship has been used to calculate extensive tables of kQ factors for use with dosimetry protocols based on absorbed-dose calibration factors. Unfortunately, the original paper contained an error which has recently been assessed (Yang et al.). The present paper presents a corrected form of this relationship, viz.: (L/p)water(air)=1.275-0.00231[%dd(10)x] which is based on corrected values of %dd(10)x. It is shown that despite changes of up to 2% in calculated values of %dd(10)x, the net effect on calculated values of kQ is less than 0.2%.
Rogers
D W
DW
Ionizing Radiation Standards, Institute for National Measurement Standards, National Research Council of Canada, Ottawa, Ontario.
Yang
C L
CL
D003037:Cobalt Radioisotopes / Q000627:therapeutic use; D017785:Photons / Q000627:therapeutic use; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results
D003037:Cobalt Radioisotopes