AbstractID: 8025 Title: A Method To Quickly Check The Dose Calculation In HDR Brachytherapy Of
Prostate
In HDR brachytherapy treatment of prostate cancer, dose calculation and isodose distribution are
performed by the use of computers. A quick check of the validity of the dose calculations is
necessary before the treatment is initiated. In HDR brachytherapy of prostate, CT images are
taken for localization of the catheters and delineation of the tumor bed. The Nucletron Plato
planning system was used for the computation of the dose and dose-volume histograms. In
parallel with the Manchester system of volume implant, a parameter Ci.s/Gy was calculated for
each implant, where Ci is the source strength in curie, s is the total dwell time in seconds and Gy
is the tumor dose in Gray. Data were collected on over four hundred patients treated with HDR
brachytherapy in our clinic with target volume ranging from 28 to 115 cm3. The data showed a
linear variation of Ci.s/Gy with volume, which are also compared with similar values from the
Paterson-Parker table. The linear fit is given by : y = 3.96 V + 132, with a correlation coefficient
(r2) of 0.943, where y is Ci.s/Gy and V is the volume in cm3. Rearranging this, the total dwell
time , s = (Gy/Ci) x [3.96 V + 132 ]. These findings have been utilized in the clinic by comparing
the computer derived dwell time with the estimated dwell time from the formula above and can
be used as a quick check of the dose calculation in HDR brachytherapy of prostate.