Abstract:Objective To investigate the dosimetric difference in the application of RapidArc using 6 and 15 MV X-rays for radiotherapy of multiple hepatic malignancy. Methods A total of 12 cases with multiple hepatic tumors (primary 5 cases and secondary 7 cases) were selected. All patients underwent the three dimensional CT simulation in free breathing. For each patient, RapidArc plans with single or two 358° arcs using 6 or 15 MV X-rays were designed respectively, the prescription dose was 2Gy per fraction×25 fractions. The dosimetric differences were compared among RapidArc plans. Results All of RapidArc plans could meet the clinical requirement. There were no significant differences in the conformity index (CI), homogeneity index (HI), the maximum dose and the minimum dose of PTV among RapidArc plans (P>0.05). All the CI could get to 0.91 and HI could get to 0.88. In the RapidArc plans with two 358° arcs, the V5, V10, V15 of normal liver were higher than with single arc, while V20, V25, V30, V35, V40 were lower than with single arc. There were no significant differences in the different radiation dose of normal liver, stomach, duodenum and spinal cord among different plans (P>0.05). The monitor units of RapidArc plans using 6 MV X-rays increased 12% compared to 15 MV averagely. Conclusion The 6 MV X-ray would be selected chiefly in the radiotherapy of multiple haptic tumor using RapidArc with whole arc(s).

Key words:Liver neoplasms,Radiation dosage,Radiotherapy