title: "Edge-on" MOSkin detector for stereotactic beam measurement and verification.
abstract: Dosimetry in small radiation field is challenging and complicated because of dose volume averaging and beam perturbations in a detector. We evaluated the suitability of the "Edge-on" MOSkin (MOSFET) detector in small radiation field measurement. We also tested the feasibility for dosimetric verification in stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). "Edge-on" MOSkin detector was calibrated and the reproducibility and linearity were determined. Lateral dose profiles and output factors were measured using the "Edge-on" MOSkin detector, ionization chamber, SRS diode and EBT2 film. Dosimetric verification was carried out on two SRS and five SRT plans. In dose profile measurements, the "Edge-on" MOSkin measurements concurred with EBT2 film measurements. It showed full width at half maximum of the dose profile with average difference of 0.11mm and penumbral width with difference of ±0.2mm for all SRS cones as compared to EBT2 film measurement. For output factor measurements, a 1.1% difference was observed between the "Edge-on" MOSkin detector and EBT2 film for 4mm SRS cone. The "Edge-on" MOSkin detector provided reproducible measurements for dose verification in real-time. The measured doses concurred with the calculated dose for SRS (within 1%) and SRT (within 3%). A set of output correction factors for the "Edge-on" MOSkin detector for small radiation fields were derived from EBT2 film measurement and presented. This study showed that the "Edge-on" MOSkin detector is a suitable tool for dose verification in small radiation field.
authors.affiliation: Clinical Oncology Unit, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Wei Loong
authors.initials: WL
authors.lastname: Jong
authors.affiliation: Clinical Oncology Unit, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia. Electronic address: nm_ung@um.edu.my.
authors.forename: Ngie Min
authors.initials: NM
authors.lastname: Ung
authors.affiliation: Clinical Oncology Unit, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia; Oncology Department, Calmette Hospital, Phnom Penh, Cambodia.
authors.forename: Ath
authors.initials: A
authors.lastname: Vannyat
authors.affiliation: Clinical Oncology Unit, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia; Medical Physics Unit, University of Malaya Medical Centre, Malaysia.
authors.forename: Zulaikha
authors.initials: Z
authors.lastname: Jamalludin
authors.affiliation: Centre for Medical Radiation Physics, University of Wollongong, Wollongong, Australia.
authors.forename: Anatoly
authors.initials: A
authors.lastname: Rosenfeld
authors.affiliation: Department of Biomedical Imaging, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia; University of Malaya Research Imaging Centre, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Jeannie Hsiu Ding
authors.initials: JH
authors.lastname: Wong
mesh_terms: D002138:Calibration; D004867:Equipment Design; D006801:Humans; D016014:Linear Models; D011785:Quality Assurance, Health Care; D011874:Radiometry / Q000295:instrumentation*; D016634:Radiosurgery / Q000379:methods*; D015203:Reproducibility of Results
keywords: EBT2; Ionization chamber; MOSFET; Quality assurance; Radiochromic film; SRS diode; Small field dosimetry