Open Collections

Sample, Caleb

University of British Columbia

The complexity of radiotherapy techniques for treating head and neck cancer has significantly advanced over the previous two decades. However, it remains common for patients to finish treatment with a severe loss in salivary function, causing significantly diminished quality of life assessments. The overall goal of research endeavours in this thesis is to develop innovative techniques that lead to better understanding and consideration of salivary glands during head and neck radiotherapy planning. This goal is approached along a multitude of paths using various imaging modalities and treatment planning techniques. A method is demonstrated for enhancing prostate specific membrane antigen (PSMA) positron emission tomography (PET) images and intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) using neural networks. PSMA PET shows high expression in salivary glands, and its relationship with functional importance can be more accurately assessed after image enhancement. IVIM MRI is a promising diffusion protocol for investigating functional heterogeneity in salivary glands, but suffers from reproducibility issues. Image enhancement methods and a new model-independent approach to quantifying diffusion are shown to improve the utility, and potentially the reproducibility, of IVIM MRI. PSMA PET uptake heterogeneity in parotid glands is quantified, demonstrating a consistent bias towards lateroposterior aspects. Uptake patterns are compared with literature-models of subregional parotid gland importance, revealing an anticorrelation between PSMA PET uptake and relative importance. A model is developed for predicting subregional importance using PSMA PET / computed tomography (CT) radiomic features. A method for tailoring importance estimates using patient-specific data is presented. An autosegmentation methodology is created for localizing the newly discovered "tubarial" salivary glands on CT images. Tubarial glands are only known to be visible on PSMA PET which is not typically acquired for head and neck cancer patients. Therefore a method of localizing the glands on CT images is necessary for tubarial glands to be considered during radiotherapy treatment planning. Lastly, a technique for translating subregional parotid gland importance data into spatially varying dose constraints during radiotherapy treatment planning is demonstrated. A retrospective planning study showed improvements in predicted salivary output at one year post-radiotherapy using this method.

Text

2024-04-04

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87682

Physics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/