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 5.156e+7 Gy/C under labratory conditions. The temperature
in the clinic at the time of measurement was 22.1oC and the pressure was 752.9 mmHg. The
average electrometer readings at bias voltages of 150 V, -150 V, and -300 V are 10.7783 nC,
-10.7898 nC, and -10.8447 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 56.38%)
**All values, unless stated within the problem, should be obtained using the TG-51 report.