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KMID : 1164220080200020109
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Journal of Korean Society for Radiotherapeutic Technology
2008 Volume.20 No. 2 p.109 ~ p.113
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Evaluation of Detector Dependency on Collimator in SRS: Compared Detectors; CC01, CC13, SFD
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Bae Yong-Ki
Bang Dong-Wan
Park Byung-Moon
Kang Min-Young
Kim Yon-Lae
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Abstract
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Purpose: To evaluate the detector dependency in the various collimator size for Stereotactic Radiosugery (SRS).
Materials and Methods: This study was performed with 6 MV photon beam (Varian 21EX, Varian, US) and the measurement detectors are used by ion chamber CC01, CC13 (Wellhofer, Germany) and stereotactic diode detector (SFD, Wellhofer, Germany). SRS collimator size was used by φ5, 10, 20, 30 mm (Brain Lab, Germany). Percentage depth dose (PDD) was measured at SSD 100 cm and field size 10×10 cm from individual detectors. Ouput factor was measured by using same setup of PDD and with maximum dose depth. Data was normalized at field size . Beam profile was measured at SSD 100 cm in SRS collimator φ10, 30 mm and field 10×10cm and a comparison of FWHM (full width half maximum), penumbra width (20~80%).
Results: The CC13 detector was overestimated 16% than other detectors from the PDD in the 5 mm collimator. Output factors were underestimated CC01 28%, CC13 72% in the 5 mm collimator and CC01 9.6%, CC13 25% in the 10 mm collimator than the SFD. Maximum difference was 3% at the FWHM of the dose profile in the 10 mm collimator and difference of the 30 mm collimator was 0% at the FWHM. Penumbra width was increased CC01 122%, CC13 194% in the 10 mm collimator and CC01 68%, CC13 185% in the 30 mm collimator than the SFD.
Conclusion: It is very important for accurate dosimetry to select a detector in small field. The SFD was considered with the most accurate dosimeter for small collimator dosimetry in this study.
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KEYWORD
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stereotactic radiosugery (SRS), ion chamber, stereotactic diode detector (SFD)
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