Dosimetric comparison of single and double collimator stereotactic body radiotherapy plans usingCyber Knife for carcinoma prostate

This study was conducted to evaluate single collimator (sc) anddouble collimator (dc) plans with respect to dosimetric analysis, calculateddose delivery to oar and treatment time in carcinoma prostate patientstreated with cyberknife. materials and methods: a retrospective study wasconducted among twenty low and intermediate risk carcinoma prostatepreviously treated with cyberknife. ptv was created and oars weredelineated. the prescribed dose was set as 37.5 gy in 5 fractions and a baseplan (bp), followed by three reduction plans (time, beam and node) weregenerated for both single and double collimators with sequential optimizationmodule. the sc and dc plans were compared for the above-said variables.the mean differences were compared using paired t-test. a p-value of <0.05was taken as statistically significant. results: the median age of the patientswas 63 years. dc plans had tighter isodose lines. the means of minimumdoses did not vary significantly across the plans but the mean and maximumdoses, ptv d2 and v95 means were significantly higher in single collimatorplan. the mean ci and hi values were better in dc plans. the doses to oarwere comparable in both single and double collimator plans in terms ofmaximum doses. the mean doses received by oar’s were significantly lesserin dc plans.sc plans resulted in lesser beams, nodes, mu and treatment time.conclusion: double collimator plans were better in producing good dosimetricresults and reduced oar doses with lesser estimated treatment efficiency.