title: Characterization of responses and comparison of calibration factor for commercial MOSFET detectors.
abstract: A commercial metal oxide silicon field effect transistor (MOSFET) dosimeter of model TN502-RD has been characterized for its linearity, reproducibility, field size dependency, dose rate dependency, and angular dependency for Cobalt-60 (60Co), 6-MV, and 15-MV beam energies. The performance of the MOSFET clearly shows that it is highly reproducible, independent of field size and dose rate. Furthermore, MOSFET has a very high degree of linearity, with r-value>0.9 for all 3 energies. The calibration factor for 2 similar MOSFET detectors of model TN502-RD were also estimated and compared for all 3 energies. The calibration factor between the 2 similar MOSFET detectors shows a variation of about 1.8% for 60Co and 15 MV, and for 6 MV it shows variation of about 2.5%, indicating that calibration should be done whenever a new MOSFET is used. However, the detector shows considerable angular dependency of about 8.8% variation. This may be due to the variation in radiation sensitivity between flat and bubble sides of the MOSFET, and indicates that positional care must be taken while using MOSFET for stereotactic radiosurgery and stereotactic radiotherapy dosimetric applications.
authors.affiliation: Division of Medical Physics and Lasers, Department of Physics, Anna University, Chennai, India.
authors.forename: Ganesan
authors.initials: G
authors.lastname: Bharanidharan
authors.forename: Durai
authors.initials: D
authors.lastname: Manigandan
authors.forename: Krishnamurthy
authors.initials: K
authors.lastname: Devan
authors.forename: Vellaiyan
authors.initials: V
authors.lastname: Subramani
authors.forename: Natanasabapathi
authors.initials: N
authors.lastname: Gopishankar
authors.forename: Tharmar
authors.initials: T
authors.lastname: Ganesh
authors.forename: Rakeshchander
authors.initials: R
authors.lastname: Joshi
authors.forename: Gourakishore
authors.initials: G
authors.lastname: Rath
authors.forename: Jagadeesan
authors.initials: J
authors.lastname: Velmurugan
authors.forename: Prakasarao
authors.initials: P
authors.lastname: Aruna
authors.forename: Singaravelu
authors.initials: S
authors.lastname: Ganesan
mesh_terms: D002138:Calibration; D006801:Humans; D019047:Phantoms, Imaging; D011867:Radioisotope Teletherapy; D011874:Radiometry / Q000295:instrumentation*; D016634:Radiosurgery; D011879:Radiotherapy Dosage; D015203:Reproducibility of Results