| Author: | Ng, Sin Yu |
| Title: | Evaluation of matching time and dosimetric impact of using cone beam computed tomography and orthogonal planar X‐ray images for positional verification in radiotherapy of prostate cancer |
| Advisors: | Wu, W. C. Vincent (HTI) |
| Degree: | M.Sc. |
| Year: | 2018 |
| Subject: | Hong Kong Polytechnic University -- Dissertations Radiation dosimetry Radiotherapy -- Positioning Prostate -- Cancer -- Radiotherapy |
| Department: | Department of Health Technology and Informatics |
| Pages: | xii, 60 pages : color illustrations |
| Language: | English |
| Abstract: | Introduction: In routine practice of modern radiotherapy, cancer patients are scanned with a computer tomography (CT) scanner to obtain a set of CT images (planning CT) for treatment planning. Before treatment delivery, patient is positioned with the help of the laser system in the treatment room in which the position should correspond to that in the planning CT. To perform treatment verification, On-Board Imager (OBI) mounted on the gantry of the linear accelerator provides two imaging techniques, which are conventional orthogonal planar image (OPI) and Cone Beam Computed Tomography (CBCT), for matching with the planning CT. CBCT provides three-dimensional information for accurate positional verification but the drawback is that it delivers a higher radiation dose to the patients. Methods: Fifteen prostate cancer patients positioned with CBCT during radiotherapy were recruited retrospectively. OPI were simulated using CBCT. 3D-3D matching on CBCT/planning CT and 2D-2D matching on simulated OPI/DRR were performed. Time spent on matching were recorded. Treatment plans were created on CBCT and the matching results were applied for dose calculation. The two positional verification methods where compared in terms of Iso-displacement vector (IDV), resulted dose distribution and matching time. Results: Significant difference was found in IDV of CBCT-based and OPI-based positional verifications. The use of CBCT resulted in higher dose conformity and homogeneity of the prostate bed and PTV than OPI for positional verification. Dosimetrically, CBCT was superior than OPI in terms of bladder dose but inferior than OPI in terms of rectum dose for positional verification. Radiobiologically, CBCT yielded a higher tumour control probability and normal tissue complication probability of rectum than OPI for positional verification. The time spent on performing 3D-3D matching on CBCT-based positional verification was approximately 2.5 minutes more than that on 2D-2D matching for OPI-based positional verification. Conclusion: CBCT-based positional verification yields a significant different IDV and is dosimetrically beneficial comparing with OPI-based positional verification in radiotherapy treatment of prostate cancer. However, in additional to CBCT acquisition, CBCT-based positional verification requires a longer matching time than OPI-based positional verification. |
| Rights: | All rights reserved |
| Access: | restricted access |
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| File | Description | Size | Format | |
|---|---|---|---|---|
| 991022173537903411.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 936.75 kB | Adobe PDF | View/Open |
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