Research Of Image Guided Radiotherapy Target And OARs Dosimetry Changes And Clinical Application

Part one:Research of image guided radiotherapy target and OARsdosimetry changeObjective: To study the target and normal tissue dosimetric change in image guided thoracic and abdominal tumor radiotherapy plan.Methods: The CT data of 10 liver cancer patients were used to design 3 groups of treatment plan: IMRT plan, single arc(RA1) Rapid Arc plan and dual arc(RA2) Rapid Arc plan. Liver tumor tracking each phase plans for ten liver cancer patients were compared to the 3D plans with a merged target volume based on 4DCT image in radiation treatment planning system(TPS). Ten patients with primary middle thoracic esophageal carcinoma were selected retrospectively. Ten 3D-CRT and IMRT lung cancer plans were analyzed retrospectively. A clinical treatment planning system was employed for plan CT and KV CBCT image to dose calculation and subsequent comparisons. Five patients diagnosed with NSCLC were treated with three-dimensional conformal radiotherapy(3DCRT) and 10 daily KV CBCT image sets were acquired for each patient. The planning target volume(PTV) dosimetry distribution and the organs at risk(OAR) dose were compared.Results: For the values of V5, V10 and V15 of healthy tissue of Rapid Arc group plan were higher than IMRT plan. But the values of V20, V25 and V30 of healthy tissue of Rapid Arc group plan were lower than IMRT plan. Compared to 3D CRT, radiation volume for the liver V5, V10, V15, V20, V25, V30, V35 and V40 by using the 4D tracking tumor plans have a significant decrease(P﹤0.05). The targets of new CT(GTV2) were significantly smaller than those of old CT(GTV1). The maximum dose of the spinal cord in the DA plans were average 27.96% less than the CT plans. The mean dose for the left, right and total lung in the DA plans were reduced by 13.80%, 23.65% and 12.96 % respectively.Conclusions: Rapid Arc plan showed improvements in conformity index and healthy tissue sparing with uncompromised target coverage. 4D tracking tumor radiotherapy allow a data support for reduction in PTV volume and dose reduction in the OARs for liver tumor patients. It is necessary to have another CT scanning and replan during the mid-thoracic esophageal carcinoma radiotherapy. The adaptive 3DCRT based on the deformable registration can reduce the dose to the lung and the spinal cord with the same PTV dose coverage. Moreover, it provides a method for further adaptive radiotherapy exploration.Part two:Study of the functional molecular imaging guided tumorstaging and clinical response evaluationObjective: To quantitatively compare the characteristics derived from ~18F-FDG and ~18F-FLT PET and assess their capacities in staging of esophageal squamous cell carcinoma(ESCC)and to investigate the change of ~18F-fluorodeoxyglucose positron emission tomography(~18F-FDG PET) uptake in target lesions provided by ~18F-FDG PET to assess patient’s imaging response to radiochemotherapy in non-small cell lung cancer(NSCLC).Methods: 26 patients with newly diagnosed ESCC who underwent both ~18F-FDG and ~18F-FLT PET were included in this study. Different image-derived indices including the standardized uptake value(SUV), gross tumor length and texture features were compared using Paired T-test. 34 patients with newly diagnosed NSCLC treated with combined radiochemotherapy were involved in this study. Patients were categorized under three headings: non responders(NR), partial responders(PR) and complete responders(CR) by experienced radiologists on the basis of Response Evaluation Criteria in Solid Tumors(RECIST) according two PET/CT scans between pretreatment and 1 month after treatment. We analyzed the standard uptake value(SUV) of ~18F-FDG PET changes. The capability of SUV changes to assess patients was evaluated using Kruskal-Wallis test(P<0.05). Specificity and sensitivity were derived using receiver operating characteristic curve(ROC).Results: Taken the histopathologic examination as the gold standard, the extracted indices’ capacities in staging of ESCC were assessed by Kruskal-Wallis test and Mann-Whitney test. The uptake of ~18F-FDG(SUVmax: ~18F-FDG 11.48; SUVmean: 6.09) was significantly higher than ~18F-FLT(SUVmax: ~18F-FLT: 6.07; SUVmean: 3.80)(P<0.001). Gross tumor volume(P=0.019), texture Correlation(P=0.030), shape feature Eccentricity(P=0.017) showed statistically significant difference when compared ~18F-FDG and ~18F-FLT using Paired T-test results. A series of ~18F-FDG and ~18F-FL PET characteristics to classify ESCC stage were significantly different according to Kruskal-Wallis test and Mann-Whitney test results. There were distinct SUV changes between different responder groups, non-responders’ maximum SUVmax and SUVmean change 1.38±4.32 and 0.99±1.89, partial-responders’ SUVmax and SUVmean change-3.31±4.12 and-1.16±0.75, complete responders SUVmax and SUVmean change-4.75 ±2.67 and-1.35±1.13. SUVmax was capable of differentiating only NR from PR and CR(P=0.020).SUVmean was also a significant factor(P=0.016) in capability of differentiating NR, CR and PR.Conclusions: ~18F-FDG image-derived characteristics: Textural features, SUV and shape feature allow for better stratification AJCC and TNM than ~18F-FLT PET in ESCC patients. SUV changes on baseline ~18F-FDG PET scans provided robust, discriminative stratification in assessing response to combined radiochemotherapy.