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KMID : 1164220190310010033
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Journal of Korean Society for Radiotherapeutic Technology
2019 Volume.31 No. 1 p.33 ~ p.41
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Effectiveness Assessment on Jaw-Tracking in Intensity Modulated Radiation Therapy and Volumetric Modulated Arc Therapy for Esophageal Cancer
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Oh Hyeon-Taek
Yoo Soon-Mi
Jeon Soo-Dong
Kim Min-Su
Song Heung-Kwon
Yoon In-Ha
Back Geum-Mun
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Abstract
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Purpose : To evaluate the effectiveness of Jaw-tracking(JT) technique in Intensity-modulated radiation therapy(IMRT) and Volumetric-modulated arc therapy(VMAT) for radiation therapy of esophageal cancer by analyzing volume dose of perimetrical normal organs along with the low-dose volume regions.
Materials and Method : A total of 27 patients were selected who received radiation therapy for esophageal cancer with using VitalBeamTM(Varian Medical System, U.S.A) in our hospital. Using Eclipse system(Ver. 13.6 Varian, U.S.A), radiation treatment planning was set up with Jaw-tracking technique(JT) and Non-Jaw-tracking technique(NJT), and was conducted for the patients with T-shaped Planning target volume(PTV), including Supraclavicular lymph nodes(SCL). PTV was classified into whether celiac area was included or not to identify the influence on the radiation field. To compare the treatment plans, Organ at risk(OAR) was defined to bilateral lung, heart, and spinal cord and evaluated for Conformity index(CI) and Homogeneity index(HI). Portal dosimetry was performed to verify a clinical application using Electronic portal imaging device(EPID) and Gamma analysis was performed with establishing thresholds of radiation field as a parameter, with various range of 0 %, 5 %, and 10 %.
Results : All treatment plans were established on gamma pass rates of 95 % with 3 mm/3 % criteria. For a threshold of 10 %, both JT and NJT passed with rate of more than 95 % and both gamma passing rate decreased more than 1 % in IMRT as the low dose threshold decreased to 5 % and 0 %. For the case of JT in IMRT on PTV without celiac area, V5 and V10 of both lung showed a decrease by respectively 8.5 % and 5.3 % in average and up to 14.7 %. A Dmean decreased by 72.3±51 cGy, while there was an increase in radiation dose reduction in PTV including celiac area. A Dmean of heart decreased by 68.9±38.5 cGy and that of spinal cord decreased by 39.7±30 cGy. For the case of JT in VMAT, V5 decreased by 2.5 % in average in lungs, and also a little amount in heart and spinal cord. Radiation dose reduction of JT showed an increase when PTV includes celiac area in VMAT.
Conclusion : In the radiation treatment planning for esophageal cancer, IMRT showed a significant decrease in
V5, and V10 of both lungs when applying JT, and dose reduction was greater when the irradiated area in low-dose field is larger. Therefore, IMRT is more advantageous in applying JT than VMAT for radiation therapy of esophageal cancer and can protect the normal organs from MLC leakage and transmitted doses in low-dose field.
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KEYWORD
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Esophageal cancer, Low dose area, Jaw-Tracking
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