ABSTRACT
Objective:To explore the dose distribution characteristics between RapidArc and five-field intensity modulated radiotherapy(5F-IMRT) plans in the treatment of locally advanced pancreatic carcinoma,and to provide reference for selecting the appropriate radiation technique in clinic.Methods:Ten patients with locally advanced pancreatic carcinoma were selected.The patients were scanned by simulation CT, and the targets and organs at risk were contoured. RapidArc plan and 5F-IMRT plan were designed respectively.The treatment time and the differences of dose distribution in the targets and organs at risk of RapidArc and 5F-IMRT plans were compared.Results:The conformal index (CI) of RapidArc plan was superior than that of 5F-IMRT plan(P=0.01).The homogeneity index (HI) of targets were similar between two plans (P>0.05).RapidArc plan decreased the maximum dose (Dmax) of the spinal cord(P=0.005);RapidArc plan decreased the mean dose(Dmean) of stomach(P=0.019);5F-IMRT plan decreased the V20 of kidney(P=0.043);RapidArc plan decreased the mean dose(Dmean) of small intestine(P=0.011).The small intestine V10 and V20 of RapidArc plan were lower than those of 5F-IMRT plan(P=0.015,P=0.14);the monitor unit (MU) of RapidArc plan was significantly lower than that of 5F-IMRT plan,with a 18% reduction from the MU level of the latter one,and the treatment time was reduced by 70.3%.RapidArc plan had the smaller doses at liver and kidney compared with 5F-IM RT plan.Conclusion:For the patients with locally advanced pancreatic carcinoma,RapidArc plan has higher CI. RapidArc plan shows the advantages in the protection of organs.Compared with 5F-IMRT,RapidArc plan has less treatment time and significantly improves the curative efficiency.In clinic, the RapidArc plan is recommended.
ABSTRACT
Objective To compare the planning quality and acute toxicity between RapidArc and fixed gantry angle dynamic intensity modulated radiotherapy (IMRT) in the postoperative radiotherapy for cervical cancer patients.Methods All 35 patients with cervical cancer who had received postoperative radiotherapy were studied,including 17 patients with RapidArc and 18 patients with IMRT.All plans were prescribed 50 Gy in 25 fractions.The dose-volume histogram data,the conformity index and homogeneity index of the targets,the monitor units (MUs) and delivery time were compared.During the treatment,the incidence of acute intestinal and bladder side effects were also compared.Results Compared to IMRT,the conformity index of RapidArc was better(t =3.13,P ＜ 0.05),but the homogeneity index was slightly worse (t =-4.25,P ＜ 0.05).The V20 and V30 of femoral head planned by RapidArc was significantly lower than that by IMRT (t =2.56,2.34,P ＜ 0.05).The mean MU for RapidArc was reduced by 52.1％ compared with IMRT.The mean treatment time for RapidArc was decreased by 46.8％ compared with IMRT.There was no difference in the incidence of acute intestinal and bladder toxicity between the two groups.Conclusion For patients with cervical cancer who need prophylactic postoperative radiotherapy,both RapidArc and IMRT plan can achieve equal target coverage and organs at risk(OAR) sparing.There is no significant difference in dosimetric parameters and acute toxicity between the two groups.Compared with IMRT,RapidArc plan has fewer MUs and less treatment time and significantly improves the treatment efficiency.
ABSTRACT
Objective:To evaluate the performance of RapidArc technique on cervical cancer patients with various filling status of the bladder. Methods: Conventional fixed field intensity modulation radiated therapy (IMRT) is used as the benchmark. In 10 fe-males suffering from cervical cancer, two CT scans were performed for treatment planning:one with an empty bladder and the other with filled bladder. The prescribed dose was 50 Gy. The images of that with an evacuated bladder and that with filled bladder were planned in the dual-arc RapidArc and the 7-field IMRT, respectively. The implementor of the plan was the Varian TrueBeam linear ac-celerator. Dose-volume histogram was used to evaluate the data from each plan. Results:When the bladder was filled, IMRT and Rapi-dArc homogeneity were 1.05 and 1.04 (P>0.05), respectively. When the bladder was emptied, the homogeneity was 1.04 for both plans (P>0.05). With or without bladder filling, the conformity index was 0.71 and 0.73 for IMRT and RapidArc (P>0.05), respectively. The effect of V30 and V40 (volume for receiving doses of 30 and 40 Gy) on the intestine and the bladder was more favorable in a full than in an empty bladder. No significant difference between the two plans was observed. IMRT exhibited improved V30 on the rectum and on the bladder. RapidArc was much better in terms of monitor unit (MU) and deliver time. Conclusion:No significant differences in the homogeneity and conformity index between dual-arc RapidArc and 7-field IMRT were observed. Filled bladder is better than empty bladder in intestine and bladder protection in both RapidArc and IMRT. IMRT is better on V30 of the rectum and the bladder, whereas RapidArc improved MU and deliver time.