食管癌VMAT与IMRT的剂量学比较

目的 比较食管癌VMAT与静态IMRT的剂量学差异,探索VMAT的可行性。

The application of volumetric modulated arc therapy in esophageal carcinoma

Objective To compare the dosimetric difference between volumetric modulated arc therapy (VMAT) and static intensity modulated radiotherapy (IMRT) for esophageal carcinoma. Methods Thirty patients were selected in this study, including 5 cases in the cervical, 5 the lower thorax, 10 the upper thorax and 10 the middle thorax. VMAT plans with a single arc and IMRT plans with five fields designed for each patients. Planning target volume (PTV) were prescribed to 60 Gy in 30 fractions. Delta 4 was used to verifie the dosimetric of treatment plans. Using paired t-test or Wilcoxon signed-test to compare the dose distribution on planning and organs at risk (OAR). The monitor units and treatment time were also evaluated to measure the treatment efficiency. Results All the VMAT and IMRT plans can satisfy the clinical dosimetry requirements. VMAT had better conformal index for PTV than IMRT (P=0.008). VMAT was better than IMRT by reducing the D_max of spinal cord (P=0.032),while the V₃₀,V₄₀ and D_mean of heart were significantly higher (P=0.041,0.012,0.002).For cervicals, the V₅, V₁₀, V₁₅ and mean dose of lung were significant higher in VMAT than those in IMRT (P=0.002- 0.002,0.002). For uppers, the values of heart V₃₀ and D_mean were significantly larger in VMAT than IMRT (P=0.030,0.026). However, the D_max of spinal cord in VMAT was lower than IMRT (P=0.006). For middles, VMAT reduced V₁₀, V₁₅, V₂₀ of lung (P=0.015,0.028,0.041). There were no significant differences between VMAT and IMRT in the lowers (P=0.262- 0.998). The 3 mm/3% γ pass rate was 92.75% for VMAT and 92.98% for IMRT (P=0.826). The average MU of VMAT (460.66 MU) was reduced by 11.84%compared with IMRT (522.55 MU)(P=0.001). The delivery time of VMAT (139.6 s)compared with IMRT (298.73 s) was reduced by an average of 53.27%(P=0.000). ConclusionsCompared with IMRT, VMAT improved the OARs dose sparing and the target CI with similar dose distribution to the target. VMAT required fewer MU, shorten the treatment time significantly. The implementation of Synergy is stable and reliable.