| Objective:To compare two radiotherapy techniques of SIB-Rapid Arc and SIB-IMRT in the target dosimetry,exposure dose organs of at risk and the number of machine units in radiotherapy for rectal cancer.Methods:10 cases of locally advanced rectal cancer were selected from the oncology Department of Changde First People’s Hospital from August 2015 to November 2016.All of them were confirmed by pathology.All patients had completed concurrent neoadjuvant chemoradiotherapy,and the radiotherapy was SIB-IMRT.10 cases of patients were first used to locate the large aperture of SIEMENS CT.After the positioning,the target area was drawn by two radiation therapist through the TPS transmission to the workstation.After the target area was outlined,the doctor was submitted to the doctor for review.After the review,the IMRT and Rapid Arc radiotherapy plan was CO produced by two physicists.The optimal plan was selected to make the 95%PTV meet the prescription dose.The dosage of the prescription was pGTV 54Gy/25 times,2.16Gy/times,PTV 45Gy/25 times and 1.8Gy/times.The dose restriction levels were PTV,small intestine,bladder and bilateral femoral head.PTV,in>35Gy,small intestinal limit D5%less than 50Gy,Dmax<55Gy;bladder limit D5%= 50Gy,Dma,less than 55Gy;bilateral femoral head D5%less than Dmax.After the Rapid Arc plan is completed,the difference between the two sets of plans is obtained through comparing the data with the IMRT plan.Results:dose distribution:all patients plan to meet the clinical requirements through the two radiation techniques of 7F-IMRT and Rapid-Arc,and can meet the total coverage of the volume of 100%PTV by the.95%ISO dose curve.For PTV Dean,Rapid Arc is slightly higher than IMRT(P=0.03),V95Gy and V105Gy of the two groups,Rapid Arc is higher than IMRT.Risk of organ damage:7F-IMRT and Rapid-Arc,which are two kinds of radiological techniques,can better protect organs and meet clinical requirements.The Dmean,V1OGy,V20Gy,and Rapid-Arc of the small intestine were slightly lower than IMRT(P=0.02,P=0.04,P=0.01),but for V30Gy in the small intestine,V40Gy Rapid-Arc was slightly lower than that of IMRT,but the difference was not statistically significant.For bladder,the V30Gy of Rapid-Arc is lower than that of IMRT(P=0.02),while that of remaining Dmean,V20Gy and V40Gy is not statistically significant.For the evaluation of bone marrow,Dmean,V5Gy,V10Gy and V20Gy of Rapid-Arc were lower than IMRT(P=0.01,P=0.04,P=0.01,P=0.01)and residual V30Gy.There was no statistical difference between them.The Dmean of Rapid Arc was slightly higher than that of IMRT(P=0.00),while V45Gy was quite similar(P=0.00).For both femoral head assessment,the data were approximately the same,but the difference was not statistically significant.MU evaluation:the machine hopping Rapid-Arc plan is significantly lower than the IMRT plan,with an average of 627.9MU,1586.7MU,P=0.000.Conclusion:the target area of the volume rotation intensity technique(Rapid Arc)plan is smaller in the low dose volume area that endanger the small intestine and bone marrow,and can significantly reduce the number of machine jumps and reduce the time of treatment compared with IMRT.Therefore,Rapid-Arc technology can be used as a new adjuvant radiotherapy option for rectal cancer. |
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