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SU‐FF‐T‐166: Dose Measurement to ICD Outside the Treatment Fields Using Optically Stimulated Luminescence
Author(s) -
Chan M,
Dauer L,
Burman C
Publication year - 2007
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2760825
Subject(s) - dosimeter , optically stimulated luminescence , thermoluminescent dosimeter , dosimetry , ionization chamber , materials science , diode , nuclear medicine , optics , bolus (digestion) , dose profile , thermoluminescence , luminescence , ionization , optoelectronics , physics , medicine , ion , surgery , quantum mechanics
Purpose: To determine relative sensitivity factors for optically stimulated luminescence (OSL) dosimeters (microStar™ DOT, Landauer), as a function of distance from the field edge, to be applied when measuring dose at any out‐of‐field point. Method and Materials: OSL dosimeters have been used to measure the radiation dose to patient's implantable cardioverter defibrillator (ICD) outside the treatment fields. ICDs have a thin outer case made of 0.4–0.6 mm thick titanium (∼2‐mm tissue equivalent) and are usually implanted 3‐mm underneath skin. Approximate 5‐mm bolus thickness is about the equivalent depth of the sensitive electronics. The responses of the dosimeters with and without bolus were measured per unit dose to water at off‐axis distances up to 15‐cm. Doses were measured by an ionization chamber located at various depths for 6 and 15 MV using a Varian Clinac‐iX linear accelerator. The relative sensitivity of the OSL dosimeters was determined as the ratio of the sensitivity at each off‐axis distance to that at central axis. Results: The OSL results were compared with those of other detectors in our previous studies [1]. The detector sensitivity as a function of distance from the field edge changed little for LiF TLD (∼2%) and OSL (∼7%); decreased by 12% and 17% for the ISORAD photon diode (Sun Nuclear Corp.); increased 11% and 14% for the skin QED diode (Sun Nuclear Corp.) for 6 MV and 15 MV, respectively. Conclusions: Compared to other detectors studied, OSL dosimeter has the closest out‐of‐field dosimetric characteristics to TLD. OSL dosimeters should be calibrated out‐of‐field and preferably with bolus equal in thickness to the depth of interest. This can be readily performed at each institution.