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The effect of voxel size on the accuracy of dose‐volume histograms of prostate 125 I seed implants
Author(s) -
Corbett JeanFrançois,
Jezioranski John,
Crook Juanita,
Yeung Ivan
Publication year - 2002
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1477417
Subject(s) - voxel , nuclear medicine , imaging phantom , dosimetry , histogram , dose volume histogram , mathematics , volume (thermodynamics) , radiation treatment planning , computer science , medicine , radiation therapy , artificial intelligence , radiology , physics , quantum mechanics , image (mathematics)
Cumulative dose‐volume histograms (DVH) 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 (larger voxels) and accuracy (smaller voxels). 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 (version 6.7, Varian, USA) treatment planning software's DVH algorithm by using voxels with a sup‐inf dimension equal to the spacing between successive transverse seed implant planes (5 mm). The volume that receives at least 200% of the target dose, V 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 (30 Gy), and above it by over 50% at high doses (>250 Gy).