Single arc volumetric-modulated arc therapy is sufficient for nasopharyngeal carcinoma: a dosimetric comparison with dual arc VMAT and dynamic MLC and step-and-shoot intensity-modulated radiotherapy

Radiation Oncology

Hong-Lei Pei³  Yang Han²  Jin Huang²  Wen-Dong Gu²  Qi-Lin Li²  Xiao-Dong Li¹  Jian-Xue Jin³  Jin-Ming Mu²  Zhong-Hua Ning² 

[1] Department of Oncology, The Third Affiliated Hospital, Soochow University, 185 Juqian Road, Changzhou 213003, China;Department of Radiation Oncology, The Third Affiliated Hospital, Soochow University, 185 Juqian Road, Changzhou 213003, China;Department of Radiation Physics, Elekta China Co. Ltd, 27 North Fourth Ring Mid Road, Chaoyang District, Beijing 100101, China

关键词: Dosimetry;    Plan evaluation;    Nasopharyngeal carcinoma;    Intensity modulated;    Radiotherapy;    Volumetric modulated arc therapy;    Radiotherapy;   

Others  :  1152786
DOI  :  10.1186/1748-717X-8-237

 received in 2013-05-27, accepted in 2013-10-05,  发布年份 2013

【 摘 要 】

Background

The performance of single arc VMAT (VMAT1) for nasopharyngeal carcinoma (NPC) on the Axesse linac has not been well described in previous studies. The purpose of this study is to assess the feasibility of VMAT1 for NPC by comparing the dosimetry, delivery efficiency, and accuracy with dual arc VMAT (VMAT2), dynamic MLC intensity-modulated radiotherapy (dIMRT), and step-and-shoot intensity-modulated radiotherapy (ssIMRT).

Methods

Twenty consecutive patients with non-metastatic NPC were selected to be planned with VMAT1, VMAT2, dIMRT and ssIMRT using Monaco 3.2 TPS on the Axesse™ linear accelerator. Three planning target volumes (PTVs), contoured as high risk, moderate risk and low risk regions, were set to receive median absorbed-dose (D_50%) of 72.6 Gy, 63.6 Gy and 54 Gy, respectively. The Homogeneity Index (HI), Conformity Index (CI), Dose Volume Histograms (DVHs), delivery efficiency and accuracy were all evaluated.

Results

Mean HI of PTV_72.6 is better with VMAT1(0.07) and VMAT2(0.07) than dIMRT(0.09) and ssIMRT(0.09). Mean HI of PTV_63.6 is better with VMAT1(0.21) and VMAT2(0.21) than dIMRT and ssIMRT. Mean CI of PTV_72.6 is also better with VMAT1(0.57) and VMAT2(0.57) than dIMRT(0.49) and ssIMRT(0.5). Mean CI of PTV_63.6 is better with VMAT1(0.76) and VMAT2(0.76) than dIMRT(0.73) and ssIMRT(0.73). VMAT had significantly improved homogeneity and conformity compared with IMRT. There was no significant difference between VMAT1 and VMAT2 in PTV coverage. Dose to normal tissues was acceptable for all four plan groups. VMAT1 and VMAT2 showed no significant difference in normal tissue sparring, whereas the mean dose of the parotid gland of dIMRT was significantly reduced compared to VMAT1 and VMAT2. The mean delivery time for VMAT1, VMAT2, dIMRT and ssIMRT was 2.7 min, 3.9 min, 5.7 min and 14.1 min, respectively. VMAT1 reduced the average delivery time by 29.8%, 51.1% and 80.8% compared with VMAT2, dIMRT and ssIMRT, respectively. VMAT and IMRT could all be delivered accurately based on our quality assurance standards.

Conclusions

In the treatment of NPC using the Axesse™ linear accelerator, single arc VMAT has shown superiority to double arc VMAT, dIMRT and ssIMRT in delivery efficiency, without compromise to the PTV coverage. However, there is still room for improvement in terms of OAR sparing.

【 授权许可】

   
2013 Ning et al.; licensee BioMed Central Ltd.

【 图 表 】

Figure 1.

Figure 2.

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