Analysis And Comparison Of 3D-CRT And IMRT Dosimetry Of Locally Advanced Pancreatic Cancer

PurposeThrough the comparison of the homogeneity and conformal index of dose distribution and coverage in the target area, and the exposure dose and volume of the organ at risk between IMRT and 3D-CRT of locally advanced pancreatic cancer, this trial is to discuss the feasibility of using IMRT to treat locally advanced pancreatic cancer, and to evaluate the dosimetric advantages of IMRT plans compared with 3D-CRT plan of locally advanced pancreatic cancer.Method1. 10 cases of locally advanced pancreatic cancer patients were sleceted from First Affiliated Hospital of Soochou University for body position fixation, enhanced CT scan(layer thickness 3mm) and target delineation in radiotherapy, respectively. This trial defines general tumor region as GTV, extended 10 mm based on GTV as CTV, and extended 10 mm based on GTV and CTV respectively as PGTV and PCTV, meanwhile,stetch the images of organs at risk layer by layer. Images are transmitted into the three-dimensional treatment planning system(TPS), which can be used to formulate the homogeneity and conformal index of dose distribution and coverage in the target area, and the exposure dose and volume of the organ at risk of each radiotherapy plan for every patients.2. Through the analysis of dose volume histogram(DVH) of each radiotherapy plan,the comparison could be made in the homogeneity and conformal index of dose distribution and coverage in the target area, as well as the exposure dose and volume of the organ at risk and the target area of the radiotherapy plan to analyse the merits and demerits of each radiotherapy plan.Results1.Significant statistical difference could be found in conformal index(CI) of PGTV(P<0.05). IMRT plan had obvious advantages compared to the 3D-CRT plan,among them IMRT7 f and IMRT9 f have more advantages than IMRT5 f. Significant statistical difference could be found in homogenous index(HI) of PGTV(P<0.05). IMRT plans had better uniformity than the 3D-CRT plan. For PTV within CI and HI comparison, the IMRT plan had more advantage than the 3D-CRT plan. For the comparison of the maximum dose and minimum dose within CTV, there was a significant difference(P<0.05) between the IMRT plans and the 3D-CRT plan. However, there was no significant difference in the average dose.2.For comparison of V40 in spinal cord, each IMRT plan had better protection compared to the 3D-CRT plan, but there was no significant difference in the comparison of V10, V20 and V30 between different radiotherapy plans. For comparison of V40 in stomach, each IMRT plan had better protection compared to the 3D-CRT plan, but there was no significant difference in the comparison of V10, V20 and V30 between different radiotherapy plans. There was no significant difference between different radiotherapy plans in the comparison of the liver and small intestine. For the comparison of duodenal V40, each IMRT plan has better protection than the 3D-CRT plan. But there were no significant differences in the comparison of V20 and V30 in the duodenum. For the comparison of V10, V20, V30, V40 in the left kindey and V10, V20,V30 in the right kidney, IMRT plans had better protection than 3D-CRT plan.Conclusion1. For locally advanced pancreatic cancer, IMRT enjoy more advantages than 3D-CRT in target area conformal and homogeneity index. Seven field intensity modulated radiation therapy can receive better treatment gain ratio in the target area coverage and treatment time.2. For the protection of organs at risk, such as spinal cord, duodenum and stomach as well as bilateral kidneys, IMRT had better protection than 3D-CRT.3 Other organs at risk such as liver and small intestine showed no signs of difference in every radiotherapy plan.