The effect of dose rate dependence of p-type silicon detectors on linac relative dosimetry.
Cumulative radiation damage to silicon semiconductor diode detectors can induce dose rate dependent sensitivity, a concern in the pulsed beam of a linac. Two p-Si diode photon detectors were used in this study, diodes A and B. Both were preirradiated by the supplier to 5 kGy, with diode A receiving an estimated 8 kGy from measurements, and diode B, 25 kGy. At 6 MV, the PDD measured with diode B was lower (by 4.4% at a depth of 25 cm) than diode A. Using SSD to vary the dose per pulse from 0.02 to 0.64 mGy/pulse, diode A was dose rate independent (within 2%), while the sensitivity of diode B changed by 13%. Silicon diode detectors should be checked regularly against ionization chambers in the pulsed beam of a linac, especially older high-resistivity diodes that have accumulated dose from high-energy photon beams.
Wilkins
D
D
Ottawa Regional Cancer Centre, Ontario, Canada. dwilkins@octrf.on.ca
Li
X A
XA
Cygler
J
J
Gerig
L
L
D055592:Biophysical Phenomena; D001703:Biophysics; D003037:Cobalt Radioisotopes; D006801:Humans; D010315:Particle Accelerators; D011874:Radiometry / Q000295:instrumentation*; D011880:Radiotherapy Planning, Computer-Assisted; D011882:Radiotherapy, High-Energy; D012666:Semiconductors; D012825:Silicon
D003037:Cobalt Radioisotopes; D012825:Silicon