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Analysis of Small-Field Dosimetry with Various Detectors
Prog. Med. Phys. 2018;29(4):164-172
Published online December 31, 2018
© 2018 Korean Society of Medical Physics.

So-Yeon Park, Byeong Geol Choi, Dong Myung Lee, Na Young Jang

Department of Radiation Oncology, Veterans Health Service Medical Center, Seoul, Korea
Correspondence to: Na Young Jang (mumuki79@gmail.com)
Tel: 82-2-2225-4647  Fax: 82-2-2225-4640
Received November 30, 2018; Revised December 14, 2018; Accepted December 14, 2018.
This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
We evaluated the performance of various detectors for small-field dosimetry with field sizes defined by a high-definition (HD) multileaf collimator (MLC) system. For small-field dosimetry, diodes referred to as “RAZOR detectors,” MOSFET detectors, and Gafchromic EBT3 films were used in this study. For field sizes less than 1×1 cm2, percent depth doses (PDDs) and lateral profiles were measured by diodes, MOSFET detectors, and films, and absolute dosimetry measurements were conducted with MOSFET detectors. For comparison purposes, the same measurements were carried out with a field size of 10×10 cm2. The dose distributions were calculated by the treatment planning system Eclipse. A comparison of the measurements with calculations yielded the percentage differences. With field sizes less than 1×1 cm2, it was shown that most of the percentage difference values were within 5% for 6-MV and 15-MV photon beams with the use of diodes. The measured lateral profiles were well matched with those calculated by Eclipse as the field sizes increased. Except for the depths of 0.5 cm and 20 cm, there was agreement in terms of the absolute dosimetry within 10% when MOSFET detectors were used. There was good agreement between the calculations and measurements conducted using diodes and EBT films. Both diode detectors and EBT3 films were found to be appropriate options for relative measurements of PDDs and for lateral profiles.
Keywords : Small-field dosimetry, Diode, MOSFET detector, Gafchromic EBT3 film


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