Premium
A real‐time in vivo dosimetric verification method for high‐dose rate intracavitary brachytherapy of nasopharyngeal carcinoma
Author(s) -
Qi ZhenYu,
Deng XiaoWu,
Cao Xinping,
Huang ShaoMin,
Lerch Michael,
Rosenfeld Anatoly
Publication year - 2012
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 - 10.1118/1.4758067
Subject(s) - brachytherapy , dosimeter , dosimetry , imaging phantom , nuclear medicine , radiation treatment planning , dose profile , medicine , nasopharyngeal carcinoma , calibration , radiation therapy , radiology , physics , quantum mechanics
Purpose: A real‐time in vivo dosimetric verification method using metal‐oxide‐semiconductor field effect transistor (MOSFET) dosimeters has been developed for patient dosimetry in high‐dose rate (HDR) intracavitary brachytherapy of nasopharyngeal carcinoma (NPC). Methods: The necessary calibration and correction factors for MOSFET measurements in 192 Iridium source were determined in a water phantom. With the detector placed inside a custom‐made nasopharyngeal applicator, the actual dose delivered to the tumor was measured in vivo and compared to the calculated values using a commercial brachytherapy planning system. Results: Five MOSFETs were independently calibrated with the HDR source, yielding calibration factors of 0.48 ± 0.007 cGy/mV. The maximum sensitivity variation was no more than 7% in the clinically relevant distance range of 1–5 cm from the source. A total of 70 in vivo measurements in 11 NPC patients demonstrated good agreement with the treatment planning. The mean differences between the planned and the actually delivered dose within a single treatment fraction were −0.1% ± 3.8% and −0.1% ± 3.7%, respectively, for right and left side assessments. The maximum dose deviation was less than 8.5%. Conclusions: In vivo measurement using the real‐time MOSFET dosimetry system is possible to evaluate the actual dose to the tumor received by the patient during a treatment fraction and thus can offer another line of security to detect and prevent large errors.