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KMID : 1164220180300010161
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Journal of Korean Society for Radiotherapeutic Technology
2018 Volume.30 No. 1 p.161 ~ p.167
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Evaluation of the Modified Hybrid-VMAT for multiple bone metastatic cancer
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Jung Il-Hun
Cho Yoon-Jin
Chang Won-Suk
Chang Won-Suk
Kim Sei-Joon
Ha Jin-Sook
Jeon Mi-Jin
Jung In-Ho
Kim Jong-Dae
Shin Dong-Bong
Lee Ik-Jae
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Abstract
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Purpose : This study evaluates the usefulness of the Modified Hybrid-VMAT scheme with consideration of background
radiation when establishing a treatment plan for multiple bone metastatic cancer including multiple tumors on the same axis.
Materials and Methods : The subjects of this study consisted of five patients with multiple bone metastatic cancer on the same axis. The planning target volume(PTV) prescription dose was 30 Gy, and the treatment plan was established using Ray Station(Ray station, 5.0.2.35, Sweden). In the treatment plan for each patient, two or more tumors were set as one isocenter. A volumetric modulated arc therapy(VMAT) plan, a hybrid VMAT(h) plan with no consideration of background radiation, and a modified hybrid VMAT(mh) with consideration of background radiation were established. Then, using each dose volume histogram(DVH), the PTV maximum dose(Dmax), mean dose(Dmean), conformity index(CI), and homogeneity index(HI) were compared among the plans. In addition, the organ at risk(OAR) of each treatment site was evaluated, and the total MU(Monitor Unit) and treatment time were also analyzed.
Results : The PTV Dmax values of VMAT, VMAT(h) and VMAT(mh) were 3188.33 cGy, 3526 cGy, and 3285.67 cGy, the Dmean values were 3081 cGy, 3252 cGy, and 3094 cGy; the CI values were 1.35±0.19, 1.43±0.12, and 1.30±0.06; the HI values were 1.06±0.01, 1.14±0.06, and 1.09±0.02; and the VMAT(h) OAR value was increased 3 %, and VMAT(mh) OAR value was decreased 18 %, respectively. Furthermore, the mean MU values were 904.90, 911.73, and 1202.13, and the mean beam on times were 128.67±10.97, 167.33±7.57, and 190.33±4.51 respectively.
Conclusions : Applying Modified Hybrid-VMAT when treating multiple targets can prevent overdose by correcting the overlapping of doses. Furthermore, it is possible to establish a treatment plan that can protect surrounding normal organs more effectively while satisfying the inclusion of PTV dose. Long-term follow-up of many patients is necessary to confirm the clinical efficacy of Modified Hybrid-VMAT.
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KEYWORD
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multiple target, VMAT, background radiation, Hybrid-VMAT
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