In vivo measurements with MOSFET detectors in oropharynx and nasopharynx intensity-modulated radiation therapy.
OBJECTIVE
To evaluate the feasibility of in vivo measurements with metal oxide semiconductor field effect transistor (MOSFET) dosimeters for oropharynx and nasopharynx intensity-modulated radiation therapy (IMRT).


METHODS
During a 1-year period, in vivo measurements of the dose delivered to one or two points of the oral cavity by IMRT were obtained with MOSFET dosimeters. Measurements were obtained during each session of 48 treatment plans for 21 patients, all of whom were fitted with a custom-made mouth plate. Calculated and measured values were compared.


RESULTS
A total of 344 and 452 measurements were performed for the right and left sides, respectively, of the oral cavity. Seventy percent of the discrepancies between calculated and measured values were within +/-5%. Uncertainties were due to interfraction patient positions, intrafraction patient movements, and interfraction MOSFET positions. Nevertheless, the discrepancies between the measured and calculated means were within +/-5% for 92% and 95% of the right and left sides, respectively. Comparison of these discrepancies and the discrepancies between calculated values and measurements made on a phantom revealed that all differences were within +/-5%.


CONCLUSIONS
Our experience demonstrates the feasibility of in vivo measurements with MOSFET dosimeters for oropharynx and nasopharynx IMRT.
Marcié
Serge
S
Department of Radiation Oncology, Centre Antoine-Lacassagne, Nice, France. serge.marcie@cal.nice.fnclcc.fr
Charpiot
Elisabeth
E
Bensadoun
René-Jean
RJ
Ciais
Gaston
G
Hérault
Joel
J
Costa
André
A
Gérard
Jean-Pierre
JP
D002138:Calibration; D005240:Feasibility Studies; D006801:Humans; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D009959:Oropharyngeal Neoplasms / Q000532:radiotherapy*; D011874:Radiometry / Q000295:instrumentation; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000379:methods* / Q000592:standards; D012666:Semiconductors