(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: To compare the dosimetry between intensity-modulated radiotherapy (IMRT) and volumetric modulation arc therapy (VMAT) with different energy photons in the preoperative radiotherapy of rectal carcinoma.
Methods: The 5-field IMRT plans of 6MV and a single arc VMAT of 6MV and 10MV plans were designed to 18 rectal cancer patients with preoperative radiotherapy by planning treatment system (Eclipse 10.0), respectively. The dose-volume histogram (DVH) parameters, conformity indexes (CI), homogeneity indexes (HI) for PTV, organs-at-risk (OAR), monitor units (MUs) and treatment time (TT) were compared among the three plans.
Results: 10MV-VMAT Plans provided the better HI, V105 than 6MV-VMAT Plans (P<0.05), which had lower CI as compared with IMRT plans (P>0.05). The Dmean and V50 of small intestine in VMAT plans were higher than IMRT plans (P>0.05), however the Dmean, D5 and V40 in VMAT plans 10MV were lower than 6MV (P<0.05). The Dmean, D5, V30 of bladder in VMAT plans were higher than IMRT plans (P<0.05). In term of the protection of D5, 10MV-VMAT plans was superior to the 6MV-VMAT plans (P<0.05). The Dmean, V20 and V30 of femoral head in VMAT plans were significantly lower than IMRT plans (P<0.05). 6MV-VMAT and 10MV-VMAT plans reduced the MUs by 61% and 55% (365±21 and 427±53, P<0.05), and shorten the TT by 73% and 71% ((67±3)s and（72±6）s, P<0.05)), as compared with IMRT plans ((MU:940±177, TT:（247±28）s)).
Conclusion: All of the plans were clinically acceptable. Compared with 6MV-VMAT and IMRT plans, 10MV-VMAT plans showing better target coverage, small intestine, bladder and femoral head sparing, while reducing the MUs and shortening the TT.
Funding Support, Disclosures, and Conflict of Interest: This work was sponsored by National Natural Science Foundation of China (No.81602667).
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