Document Detail

Measurement of relative output factors for the 8 and 4 mm collimators of Leksell Gamma Knife Perfexion by film dosimetry.
MedLine Citation:
PMID:  19544795     Owner:  NLM     Status:  MEDLINE    
Three types of films, Kodak EDR2, Gafchromic EBT, and Gafchromic MD-V2-55, were used to measure relative output factors of 4 and 8 mm collimators of the Leksell Gamma Knife Perfexion. The optical density to dose calibration curve for each of the film types was obtained by exposing the films to a range of known doses. Ten data points were acquired for each of the calibration curves in the dose ranges from 0 to 4 Gy, 0 to 8 Gy, and 0 to 80 Gy for Kodak EDR2, Gafchromic EBT, and Gafchromic MD-V2-55 films, respectively. For the measurement of relative output factors, five films of each film type were exposed to a known dose. All films were scanned using EPSON EXPRESSION 10000 XL scanner with 200 dpi resolution in 16 bit gray scale for EDR2 film and 48 bit color scale for Gafchromic films. The scanned images were imported in the red channel for both Gafchromic films. The background corrections from an unexposed film were applied to all films. The output factors obtained from film measurements were in a close agreement both with the Monte Carlo calculated values of 0.924 and 0.805 for 8 and 4 mm collimators, respectively. These values are provided by the vendor and used as default values in the vendor's treatment planning system. The largest differences were noted for the Kodak EDR 2 films (-2.1% and -4.5% for 8 and 4 mm collimators, respectively). The best agreement observed was for EBT Gafchromic film (-0.8% and +0.6% differences for 8 and 4 mm collimators, respectively). Based on the present values, no changes in the default relative output factor values were made in the treatment planning system.
Josef Novotny; Jagdish P Bhatnagar; Mubina A Quader; Greg Bednarz; L Dade Lunsford; M Saiful Huq
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Publication Detail:
Type:  Comparative Study; Evaluation Studies; Journal Article    
Journal Detail:
Title:  Medical physics     Volume:  36     ISSN:  0094-2405     ISO Abbreviation:  Med Phys     Publication Date:  2009 May 
Date Detail:
Created Date:  2009-06-23     Completed Date:  2009-07-15     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0425746     Medline TA:  Med Phys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1768-74     Citation Subset:  IM    
Department of Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213, USA.
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MeSH Terms
Computer-Aided Design
Energy Transfer
Equipment Design
Equipment Failure Analysis
Film Dosimetry / instrumentation*,  methods*
Radiosurgery / instrumentation*
Radiotherapy Dosage
Reproducibility of Results
Sensitivity and Specificity

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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