| Author: | Tam, Kei Tai |
| Title: | To evaluate the feasibility of minimizing ovarian dose in irradiation of abdominal and pelvic malignancies by applying block and optimal margin in helical tomotherapy |
| Degree: | M.Sc. |
| Year: | 2018 |
| Subject: | Hong Kong Polytechnic University -- Dissertations Radiation -- Dosage Digestive organs -- Cancer Uterus -- Cancer |
| Department: | Department of Health Technology and Informatics |
| Pages: | 63 pages : color illustrations |
| Language: | English |
| Abstract: | Aims: This study aimed to evaluate the dosimetric impact on target volume and organs at risk (OARs) in irradiation of abdominal and pelvic malignancies with and without block and margin (B&M) added. Based on the results, optimal margins for ovaries will be recommended. Materials and Methods: The ovaries of 16 patients were contoured by tracing the ovarian veins in CTs. Reference plans (Plan(ref)) were generated following the original physician dose prescriptions. Another 16 plans (Plan(B&M)) with Peters N., suggested margins of 2.2cm and 2.9cm for left (Lt) and right (Rt) ovaries respectively were generated by adding directional or complete block to the ovarian margin. The differences between Plan(ref) and Plan(B&M) in ovaries Dmax, target quality and OARs doses were compared by 2 tailed paired t-tests. A one tailed one sample t-test was used to test if the mean ovary Dmax in Plan(B&M) could be lowered than 2Gy. If not, the lowest achievable ovarian dose would be found out by subsequent t-tests. Optimal ovarian margins for ovaries <3Gy based on the ovarian margin doses calculation in Plan(B&M) would be estimated. Results: There were significant difference between the 2 sets of plans in Lt/Rt ovary Dmax, Lt /Rt ovarian margin Dmax, target Dmin and conformation index (CI), but not for the target Dmax, homogeneity index (HI) and all OARs. No significant difference between 2Gy and Lt/Rt ovarian Dmax with B&M. Subsequent t-tests showed that the lowest achievable dose of at least one ovary was 5Gy. The optimal ovarian margins was 1.91cm and 2.57cm for Lt and Rt ovaries respectively. Conclusion: After B&M added, the ovaries doses could be significantly reduced without much affecting target quality. The ovarian dose ≤3Gy could be achieved with the suggested ovarian margin. B&M application offered advantage of lowering the ovarian dose in unilateral small volume target. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| 991022173537803411.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 1.99 MB | Adobe PDF | View/Open |
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