PRESAGE 3D dosimetry accurately measures Gamma Knife output factors. Phys Med Biol 2014 Dec 07;59(23):N211-20
Date
11/05/2014Pubmed ID
25368961Pubmed Central ID
PMC4285621DOI
10.1088/0031-9155/59/23/N211Scopus ID
2-s2.0-84910644198 (requires institutional sign-in at Scopus site) 9 CitationsAbstract
Small-field output factor measurements are traditionally very difficult because of steep dose gradients, loss of lateral electronic equilibrium, and dose volume averaging in finitely sized detectors. Three-dimensional (3D) dosimetry is ideal for measuring small output factors and avoids many of these potential challenges of point and 2D detectors. PRESAGE 3D polymer dosimeters were used to measure the output factors for the 4 mm and 8 mm collimators of the Leksell Perfexion Gamma Knife radiosurgery treatment system. Discrepancies between the planned and measured distance between shot centers were also investigated. A Gamma Knife head frame was mounted onto an anthropomorphic head phantom. Special inserts were machined to hold 60 mm diameter, 70 mm tall cylindrical PRESAGE dosimeters. The phantom was irradiated with one 16 mm shot and either one 4 mm or one 8 mm shot, to a prescribed dose of either 3 Gy or 4 Gy to the 50% isodose line. The two shots were spaced between 30 mm and 60 mm apart and aligned along the central axis of the cylinder. The Presage dosimeters were measured using the DMOS-RPC optical CT scanning system. Five independent 4 mm output factor measurements fell within 2% of the manufacturer's Monte Carlo simulation-derived nominal value, as did two independent 8 mm output factor measurements. The measured distances between shot centers varied by ± 0.8 mm with respect to the planned shot displacements. On the basis of these results, we conclude that PRESAGE dosimetry is excellently suited to quantify the difficult-to-measure Gamma Knife output factors.
Author List
Klawikowski SJ, Yang JN, Adamovics J, Ibbott GSAuthor
Slade J. Klawikowski PhD Assistant Professor in the Radiation Oncology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Phantoms, ImagingRadiometry
Radiosurgery
Radiotherapy Dosage
Reproducibility of Results
