title: Dosimetric evaluation of a MOSFET detector for clinical application in photon therapy.
abstract: Dosimetric characteristics of a metal oxide-silicon semiconductor field effect transistor (MOSFET) detector are studied with megavoltage photon beams for patient dose verification. The major advantages of this detector are its size, which makes it a point dosimeter, and its ease of use. In order to use the MOSFET detector for dose verification of intensity-modulated radiation therapy (IMRT) and in-vivo dosimetry for radiation therapy, we need to evaluate the dosimetric properties of the MOSFET detector. Therefore, we investigated the reproducibility, dose-rate effect, accumulated-dose effect, angular dependence, and accuracy in tissue-maximum ratio measurements. Then, as it takes about 20 min in actual IMRT for the patient, we evaluated fading effect of MOSFET response. When the MOSFETs were read-out 20 min after irradiation, we observed a fading effect of 0.9% with 0.9% standard error of the mean. Further, we applied the MOSFET to the measurement of small field total scatter factor. The MOSFET for dose measurements of small field sizes was better than the reference pinpoint chamber with vertical direction. In conclusion, we assessed the accuracy, reliability, and usefulness of the MOSFET detector in clinical applications such as pinpoint absolute dosimetry for small fields.
authors.affiliation: Particle Therapy Division, Research Center for Innovative Oncology, National Cancer Center Hospital East, Kashiwa-shi, Chiba, Japan. rkohno@east.ncc.go.jp
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kohno
authors.forename: Eriko
authors.initials: E
authors.lastname: Hirano
authors.forename: Teiji
authors.initials: T
authors.lastname: Nishio
authors.forename: Tomoko
authors.initials: T
authors.lastname: Miyagishi
authors.forename: Tomonori
authors.initials: T
authors.lastname: Goka
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Kawashima
authors.forename: Takashi
authors.initials: T
authors.lastname: Ogino
mesh_terms: D002138:Calibration; D006801:Humans; D019047:Phantoms, Imaging; D017785:Photons / Q000627:therapeutic use*; D019904:Polymethyl Methacrylate / Q000737:chemistry; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012666:Semiconductors; D012680:Sensitivity and Specificity; D014173:Transistors, Electronic
chemical_list: D019904:Polymethyl Methacrylate
references.citation: Int J Radiat Oncol Biol Phys. 1997 Mar 1;37(4):959-64
references.pmid: 9128975
references.citation: Med Phys. 2002 Jun;29(6):1109-15
references.pmid: 12094980
references.citation: Med Phys. 1994 Apr;21(4):567-72
references.pmid: 8058024
references.citation: Radiother Oncol. 2006 Sep;80(3):288-95
references.pmid: 16916563
references.citation: Phys Med Biol. 1999 May;44(5):1125-32
references.pmid: 10368006
references.citation: Int J Radiat Oncol Biol Phys. 2005 Apr 1;61(5):1603-6
references.pmid: 15817369
references.citation: Phys Med Biol. 2006 Dec 7;51(23):6077-86
references.pmid: 17110771
references.citation: Radiat Prot Dosimetry. 2005;113(1):40-6
references.pmid: 15728424
references.citation: Phys Med Biol. 1998 Nov;43(11):3235-59
references.pmid: 9832014
references.citation: Phys Med Biol. 2004 Sep 7;49(17):4031-48
references.pmid: 15470921
references.citation: Phys Med Biol. 1998 Oct;43(10):2755-68
references.pmid: 9814515
references.citation: Phys Med Biol. 1997 Dec;42(12):2383-91
references.pmid: 9434295
references.citation: Med Phys. 2004 Mar;31(3):609-15
references.pmid: 15070261
references.citation: Med Phys. 2004 May;31(5):1003-8
references.pmid: 15191284