Multidimensional dosimetry of 106Ru eye plaques using EBT3 films and its impact on treatment planning. Issue 10 (15th September 2015)

• Record Type: Journal Article
• Authors: Heilemann, G.; Nesvacil, N.; Blaickner, M.; Kostiukhina, N.; Georg, D.
• Is Part Of: Medical physics. Volume 42:Issue 10(2015)
• Page Start: 5798
• Page End: 5808
• Publication Date: 2015-09-15
• Subjects: brachytherapy -- dosimetry -- eye -- Monte Carlo methods -- radioactive sources -- tumours; Dose‐volume analysis -- Applications -- Dosimetry/exposure assessment -- Therapeutic applications, including brachytherapy -- Radioactive sources -- Cancer; Radiation therapy -- Radioactive sources -- Scintigraphy -- Radioactive sources other than neutron sources (radioactive dressings A61M36/14); brachytherapy -- eye plaque -- radiochromic film -- dosimetry -- quality assurance; Dosimetry -- Cancer -- Monte Carlo methods -- Medical treatment planning -- Silicon detectors -- Brachytherapy -- Diamond -- Calibration -- Photons -- Active layer; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4929564
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: The purpose of this study was to establish a method to perform multidimensional radiochromic film measurements of 106 Ru plaques and to benchmark the resulting dose distributions against Monte Carlo simulations (MC), microdiamond, and diode measurements. Methods: Absolute dose rates and relative dose distributions in multiple planes were determined for three different plaque models (CCB, CCA, and COB), and three different plaques per model, using EBT3 films in an in‐house developed polystyrene phantom and themcnp6 MC code. Dose difference maps were generated to analyze interplaque variations for a specific type, and for comparing measurements against MC simulations. Furthermore, dose distributions were validated against values specified by the manufacturer (BEBIG) and microdiamond and diode measurements in a water scanning phantom. Radial profiles were assessed and used to estimate dosimetric margins for a given combination of representative tumor geometry and plaque size. Results: Absolute dose rates at a reference depth of 2 mm on the central axis of the plaque show an agreement better than 5% (10%) when comparing film measurements (mcnp6 ) to the manufacturer's data. The reproducibility of depth‐dose profile measurements was <7% (2 SD) for all investigated detectors and plaque types. Dose difference maps revealed minor interplaque deviations for a specific plaque type due to inhomogeneities of the active layer. The evaluation of dosimetric margins showed that for a majority of the investigated cases, the tumor was not completely covered by the 100% isodose prescribed to the tumor apex if the difference between geometrical plaque size and tumor base ≤4 mm. Conclusions: EBT3 film dosimetry in an in‐house developed phantom was successfully used to characterize the dosimetric properties of different 106 Ru plaque models. The film measurements were validated against MC calculations and other experimental methods and showed a good agreement with data from BEBIG well within published tolerances. The dosimetric information as well as interplaque comparison can be used for comprehensive quality assurance and for considerations in the treatment planning of ophthalmic brachytherapy.