Solutio in silico

TG-51 Practice Problems

A medical physicist is performing absolute dose calibration for a 60Co photon beam. All measurements were taken with a NE2505/3,3A model ion chamber. The ion chamber-electrometer unit was calibrated to measure 5.208e+7 Gy/C under labratory conditions. The temperature in the clinic at the time of measurement was 22.3oC and the pressure was 768.8 mmHg. The average electrometer readings at bias voltages of 150 V, -150 V, and -300 V are 11.0852 nC, -11.1045 nC, and -11.1470 nC, respectively. Each measurement was taken after 100 machine monitor units (MU) had been delivered. What is the value of the absorbed dose to water at dmax for an SSD setup, in cGy/MU? (The PDD for this beam at clinical setup is 55.30%)

**All values, unless stated within the problem, should be obtained using the TG-51 report.

cGy/MU