Relative output factor measurements of a 5 mm diameter radiosurgical photon beam using polymer gel dosimetry

Pappas, E; Petrokokkinos, L; Angelopoulos, A; Maris, TG; Kozicki, M; Dalezios, I; Kouloulias, V

dc.contributor.author	Pappas, E	en
dc.contributor.author	Petrokokkinos, L	en
dc.contributor.author	Angelopoulos, A	en
dc.contributor.author	Maris, TG	en
dc.contributor.author	Kozicki, M	en
dc.contributor.author	Dalezios, I	en
dc.contributor.author	Kouloulias, V	en
dc.date.accessioned	2014-03-01T02:43:29Z
dc.date.available	2014-03-01T02:43:29Z
dc.date.issued	2005	en
dc.identifier.issn	0094-2405	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/31442
dc.subject	Dosimetry	en
dc.subject	Output factors	en
dc.subject	Polymer gel	en
dc.subject	Radiosurgery	en
dc.subject.classification	Radiology, Nuclear Medicine & Medical Imaging	en
dc.subject.other	polymer	en
dc.subject.other	conference paper	en
dc.subject.other	dosimetry	en
dc.subject.other	gel	en
dc.subject.other	ionization chamber	en
dc.subject.other	light	en
dc.subject.other	mathematical analysis	en
dc.subject.other	nuclear magnetic resonance imaging	en
dc.subject.other	priority journal	en
dc.subject.other	radiation beam	en
dc.subject.other	radiosurgery	en
dc.subject.other	X ray film	en
dc.subject.other	Calibration	en
dc.subject.other	Gels	en
dc.subject.other	Ions	en
dc.subject.other	Magnetic Resonance Imaging	en
dc.subject.other	Particle Accelerators	en
dc.subject.other	Phantoms, Imaging	en
dc.subject.other	Photons	en
dc.subject.other	Polymers	en
dc.subject.other	Radiation Dosage	en
dc.subject.other	Radiometry	en
dc.subject.other	Radiosurgery	en
dc.subject.other	Radiotherapy Dosage	en
dc.subject.other	Radiotherapy, High-Energy	en
dc.title	Relative output factor measurements of a 5 mm diameter radiosurgical photon beam using polymer gel dosimetry	en
heal.type	conferenceItem	en
heal.identifier.primary	10.1118/1.1916048	en
heal.identifier.secondary	http://dx.doi.org/10.1118/1.1916048	en
heal.language	English	en
heal.publicationDate	2005	en
heal.abstract	Besides the fine spatial resolution inherent in polymer gel-magnetic resonance imaging (MRI) dosimetry, the method also features the potential for multiple measurements of varying sensitive volume in a single experiment by integrating results in MRI voxels of finite dimensions (i.e., in plane resolution by slice thickness). This work exploits this feature of polymer gel dosimetry to propose an experimental technique for relative output factor (OF) measurements of small radiosurgical beams. Two gel vials were irradiated with a 5 and 30 mm diameter 6 MV radiosurgery beam and MR scanned with the same slice thickness and three different in plane resolutions. Using this experimental data set, 5 mm OF measurements with the PinPoint ion chamber are simulated by integrating results over a sensitive volume equal to that of the chamber. Results are found in agreement within experimental uncertainties with actual PinPoint measurements verifying the validity of the proposed experimental procedure. The polymer gel data set is subsequently utilized for OF measurements of the 5 mm beam with varying sensitive volume to discuss the magnitude of detector volume averaging effects. Seeking to correct for volume averaging, results are extrapolated to zero sensitive volume yielding a 5 mm OF measurement of (0.66 +/- 5%). This result compares reasonably with corresponding ionometric and radiographic film measurements of this work and corresponding, limited, data in the literature. Overall, results suggest that polymer gel dosimetry coupled with the proposed experimental procedure helps overcome not only tissue-equivalence and beam perturbation implications but also volume averaging and positioning uncertainties which constitute the main drawback in small radiosurgical beam dosimetry. (c) 2005 American Association of Physicists in Medicine.	en
heal.publisher	AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS	en
heal.journalName	Medical Physics	en
dc.identifier.doi	10.1118/1.1916048	en
dc.identifier.isi	ISI:000229908600008	en
dc.identifier.volume	32	en
dc.identifier.issue	6	en
dc.identifier.spage	1513	en
dc.identifier.epage	1520	en