title: Quantitative comparison of 3D and 2.5D gamma analysis: introducing gamma angle histograms.
abstract: Comparison of dose distributions using the 3D gamma method is anticipated to provide better indicators for the quality assurance process than the 2.5D (stacked 2D slice-by-slice) gamma calculation, especially for advanced radiotherapy technologies. This study compares the accuracy of the 3D and 2.5D gamma calculation methods. 3D and 2.5D gamma calculations were carried out on four reference/evaluation 3D dose sample pairs. A number of analysis methods were used, including average gamma and gamma volume histograms. We introduce the concept of gamma-angle histograms. Noise sensitivity tests were also performed using two different noise models. The advantage of the 3D gamma method showed up as a higher proportion of points passing the tolerance criteria of 3% dose difference and 3 mm distance-to-agreement (DTA), with considerably lower average gamma values, a lower influence of the DTA criterion, and a higher noise tolerance. The 3D gamma approach is more reliable than the 2.5D approach in terms of providing comprehensive quantitative results, which are needed in quality assurance procedures for advanced radiotherapy methods.
authors.affiliation: The Centre for Imaging Sciences, Manchester Academic Health Sciences Centre, Stopford Building, The University of Manchester, Oxford Road, Manchester M13 9PT, UK. mohammad.alsad@manchester.ac.uk
authors.forename: M
authors.initials: M
authors.lastname: Al Sa'd
authors.forename: J
authors.initials: J
authors.lastname: Graham
authors.forename: G P
authors.initials: GP
authors.lastname: Liney
authors.forename: C J
authors.initials: CJ
authors.lastname: Moore
mesh_terms: D006258:Head and Neck Neoplasms / Q000532:radiotherapy; D006801:Humans; D011786:Quality Control; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*