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Dosimetric Comparison Between Static IMRT and VMAT for Cervical Cancer

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M Kang

M Kang1*, J Dai1, M Huang2, Y Xu1, J An2, (1) Department of Radiation Oncology Cancer Hospital & Institute, Chinese Acadmey of Medical Sciences, China, Beijing, 100021 (2) Department of Gynecological Oncology, Cancer Institute & Hospital, Chinese Academy of Medical Sciences, China, Beijing,100021

SU-E-T-619 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To evaluate the plan quality of static IMRT and VMAT for cervical cancer from comparing the dosimetric characteristic of IMRT and VMAT plans.

Methods:For 16 patients with cervical cancer,7-field step & shoot IMRT plan and 360° dual-arc VMAT plan were optimized using Pinnacle 9.0 TPS(prescribed 95% PTV dose 50Gy).Plans were evaluated according to CI(conformity index),HI (homogeneity index),volume of the OARs and dose of the normal tissues from DVH.

Results:The CI and HI of IMRT and VMAT plans were 0.82,0.86 and 1.09,1.09,respectively.Both of IMRT and VMAT could achieve the same homogeneity,while the VMAT had a better performance in conformity than IMRT.The V20,V30and V40 of rectum for VMAT were 1.4%,6.9% and 4.5% less than those for IMRT,and the mean dose was lower by 1.3Gy.In VMAT,the V20,V30and V40 of bladder were 4.3%,6.5% and3.5% less than those for IMRT plans,and mean dose was reduced by 1.6Gy.The V5 and V50 of rectum and bladder for IMRT and VMAT were comparable with less than 1% in difference.The V10 and V20 of intestine for VMAT were 11% and 4.5% less than those for IMRT,while the V10 of colon for VMAT was 6.6% higher than that for IMRT plans.For sigmoid the V30 and V40 of VMAT were 3.2% and 5.3% less than of IMRT,but the V50 of VMAT was slightly higher than that of IMRT by 1.3%.The V50 of pelvic for VMAT was 5.2% higher than that for IMRT,but the mean dose was reduced by 0.4Gy.For normal tissues,the V10 of VMAT was2% higher than that of IMRT,while the V20 of VMAT was 5.4% less than that of IMRT.

Conclusion:The dosimetric comparison indicated that VMAT can deliver prescribed dose more conformity onto the patient and spare rectum and bladder better than IMRT. Considering advantages of fewer MUs and faster treatment, the VMAT is a better choice for cervical cancer.

Funding Support, Disclosures, and Conflict of Interest: National Natural Foundation of China

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