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KMID : 1164220150270010031
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Journal of Korean Society for Radiotherapeutic Technology
2015 Volume.27 No. 1 p.31 ~ p.43
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A Study of volumetric modulated arc therapy for stereotactic body radiation therapy in case of multi-target liver cancer using flattening filter free beam
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Yeom Mi-Suk
Yoon In-Ha
Hong Dong-Ki
Back Geum-Mun
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Abstract
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Purpose : Stereotactic body radiation therapy (SBRT) has proved its efficacy in several patient populations with primary and metastatic limited tumors. Because SBRT prescription is high dose level than Conventional radiation therapy. SBRT plan is necessary for effective Organ at risk (OAR) protection and sufficient Planning target volume (PTV) dose coverage. In particular, multi-target cases may result excessive doses to OAR and hot spot due to dose overlap. This study evaluate usefulness of Volumetric modulated arc therapy (VMAT) in dosimetric and technical considerations using Flattening filter free (FFF) beam.
Materials and Methods : The treatment plans for five patients, being treated on TrueBeam STx(VarianTM, USA) with VMAT
using 10MV FFF beam and Standard conformal radiotherapy (CRT) using 15MV Flattening filter (FF) beam. PTV, liver,
duodenum, bowel, spinal cord, esophagus, stomach dose were evaluated using the dose volume histogram(DVH). Conformity index(CI), homogeneity index(HI), Paddick’s index(PCI) for the PTV was assessed. Total Monitor unit (MU) and beam on time was assessed.
Results : Average value of CI, HI and PCI for PTV was 1.381±0.028, 1.096±0.016, 0.944±0.473 in VMAT and 1.381±0.042, 1.136±0.042, 1.534±0.465 in CRT respectively. OAR dose in CRT plans evaluated 1.8 times higher than VMAT. Total MU in VMAT evaluated 1.3 times increase than CRT. Average beam on time was 6.8 minute in VMAT and 21.3 minute in CRT.
Conclusion : VMAT for SBRT in multi-target liver cancer using FFF beam is effective treatment techniqe in dosimetric and technical considerations. VMAT decrease intra-fraction error due to treatment time shortening using high dose rate of FFF beam.
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KEYWORD
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FFF, VMAT
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