Abstract
This study aimed to compare fixed‐field, intensity‐modulated radiotherapy (f‐IMRT) with intensity‐modulated arc therapy (IMAT) treatment plans in dosimetry and practical application for cervical esophageal carcinoma. For ten cervical esophageal carcinoma cases, f‐IMRT plan (seven fixed‐fields) and two IMAT plans, namely RA (coplanar 360° arcs) and RAx (coplanar 360° arcs without sectors from 80° to 110°, and 250° to 280°), were generated. DVHs were adopted for the statistics of above parameters, as well as conformal index (CI), homogeneity index (HI), dose‐volumetric parameters of normal tissues, total accelerator output MUs and total treatment time. There were differences between RAx and f‐IMRT, as well as RA in PTV parameters such as HI, V95% and V110%, but not in CI. RAx reduced lung V5 from (50.9%± 9.8% in f‐IMRT and (51.4%± 10.8% in RA to (49.3%± 10.4% in RAx (p<0.05). However, lung V30,V40,V50 and MLD increased in RAx. There was no difference in the mean heart dose in three plans. Total MU was reduced from 1174.8±144.6 in f‐IMRT to 803.8±122.2 in RA and 736.2±186.9 in RAx (p<0.05). Compared with f‐IMRT, IMAT reduced low dose volumes of lung and total MU on the basis of meeting clinical requirements.PACS numbers: 87.55.D, 87.55.dk, 87.55.ne
Highlights
49 Yin et al.: RapidArc in EC radiotherapy dynamic MLC while the accelerator gantry rotates continuously, and accompanied by variable dose rate
planning target volume (PTV) coverage As summarized in Table 1, statistical difference of HI, D2% and V110% were observed as comparison of RAx with f-IMRT and RapidArc arcs (RA) (p < 0.05), which meant that the high-dose volume of RAx enlarged
HI in RAx increased from 13.19 ± 1.40 in f-IMRT and from 13.38 ± 0.98 in RA to 14.36 ± 1.28; D2% increased from 68.18 ± 0.96 Gy in f-IMRT and 68.09 ± 0.84 Gy in RA to 68.61 ± 0.87 Gy; and V110% increased from 11.0% ± 6.8% in f-IMRT and 11.6% ± 8.6% in RA to 14.3% ± 6.8%
Summary
49 Yin et al.: RapidArc in EC radiotherapy dynamic MLC while the accelerator gantry rotates continuously, and accompanied by variable dose rate. The Anisotropic Analytical Algorithm (AAA) was used It showed that the calculation of the dose distribution can be performed with a clinically acceptable accuracy using a resolution of 2.5 mm or better.[7] Court et al[8] concluded that pencil-beam algorithm, used in chest tumor dose calculation, would underestimated the lung dose. Both f-IMRT plan and RapidArc plans used AAA for dose calculation. F-IMRT and RapidArc plans were compared for cervical esophageal cancer cases, and the application of the techniques was discussed
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