Premium
Sci—Thurs PM: Planning—04: Evaluation of Dosimetric Differences between Dose‐to‐Water and Dose‐to‐Medium for Head and Neck Patients Treated with Electron Beams
Author(s) -
Gil E,
Clark B,
Cygler JE
Publication year - 2009
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 - 10.1118/1.3244175
Subject(s) - stopping power , monte carlo method , nuclear medicine , dosimetry , head and neck , electron , cathode ray , radiation treatment planning , beam (structure) , materials science , medicine , physics , radiology , radiation therapy , optics , mathematics , surgery , nuclear physics , statistics , detector
Monte Carlo based treatment planning systems have made it possible to calculate and evaluate dose‐distributions in terms of dose‐to‐medium, D m , as opposed to the traditional dose‐to‐water, D w . For electron beams, differences between the two methods have been reported to exceed 10% in some cases. These differences are greatest in materials whose electron densities are furthest from water, such as bone and lung. This has raised the question of which approach is more appropriate. The purpose of this study is to investigate the dosimetric differences between plans calculated using the D mversus D win clinical head and neck cases treated with electron beams. The analysis included plans for phantoms containing hard bone inhomogeneities as well as retrospective head and neck cases treated with electron beams. Differences between plans calculated using D mand D wwere evaluated by means of the dose profiles and isodose distributions. For phantoms and head and neck patients, dose to the bone was larger by up to 10% when calculating dose‐to‐water rather than dose to medium. Differences between plans depend on beam energy, as well as the location of the tumor and organs at risk, and are consistent with the differences between water‐to‐bone stopping power ratios.