document: The effect of voxel size on the accuracy of dose-volume histograms of prostate / sup 125/I seed implants Cumulative dose-volume histograms -LRB- DVH -RRB- are crucial in evaluating the quality of radioactive seed prostate implants . When calculating DVHs , the choice of voxel size is a compromise between computational speed -LRB- larger voxels -RRB- and accuracy -LRB- smaller voxels -RRB- . We quantified the effect of voxel size on the accuracy of DVHs using an in-house computer program . The program was validated by comparison with a hand-calculated DVH for a single 0.4-U iodine-125 model 6711 seed . We used the program to find the voxel size required to obtain accurate DVHs of five iodine-125 prostate implant patients at our institution . One-millimeter cubes were sufficient to obtain DVHs that are accurate within 5 % up to 200 % of the prescription dose . For the five patient plans , we obtained good agreement with the VariSeed -LRB- version 6.7 , Varian , USA -RRB- treatment planning software 's DVH algorithm by using voxels with a sup-inf dimension equal to the spacing between successive transverse seed implant planes -LRB- 5 mm -RRB- . The volume that receives at least 200 % of the target dose , V/sub 200 / , calculated by VariSeed was 30 % to 43 % larger than that calculated by our program with small voxels . The single-seed DVH calculated by VariSeed fell below the hand calculation by up to 50 % at low doses -LRB- 30 Gy -RRB- , and above it by over 50 % at high doses -LRB- > 250 Gy -RRB-
doc_bio_tags: O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O B I I I O O O O O O O O B I O O O O B I O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
extractive_keyphrases: radioactive seed prostate implants voxel size computational speed
abstractive_keyphrases: cumulative dose-volume histograms prostate /sup 125/i seed implants in-house computer program hand-calculated dose-volume histograms single-seed dose-volume histograms /sup 125/i model /sup 125/i prostate implant patients variseed treatment planning software's dose-volume histogram algorithm i