Optimization of reconstruction methods and injected activity for whole body [18F]FDG PET/CT imaging

Abstract

[18F]Fluorodeoxyglucose ([18F]FDG) Positron Emission Tomography/Computed Tomography (PET/CT) imaging is a powerful tool in the diagnosis of cancer and subsequent treatment planning. New state-of-the-art PET/CT scanners have the capacity to generate images of superb quality. The new scanners feature detectors with increased sensitivity and a new generation of reconstruction algorithms that produce higher quality images than the scanners they are replacing. In addition to the scanner, the scan duration, amount of administered [18F]FDG activity, and the anatomy of the patients themselves are also determining factors of image quality. There is evidence suggesting that [18F]FDG PET image quality is significantly reduced for larger patients, jeopardizing lesion detection. Two possible solutions to this problem are to (i) increase injected activity or (ii) increase scan duration. Increasing scan duration is preferable but not always possible in a busy clinic. Increasing injected activity is necessary but a proper scaling regimen with patient size must be determined in order to achieve consistent image quality. The aim of the work presented in this thesis was to achieve higher quantification accuracy and consistent image quality for all patients scanned with [18F]FDG PET. Because quantitative PET/CT images require corrections for image degrading effects, for which attenuation correction is the main contributor and is performed based on CT images, the first step in this project was to develop software tools to automate the analysis of phantom images for CT quality assurance. The next step was to optimize the reconstruction parameters for whole body [18F]FDG PET based on a phantom experiment. Finally, a retrospective study was conducted using patient [18F]FDG PET images to characterize the relationship between patient anatomical characteristics and image quality. This work concludes by suggesting optimized reconstruction parameters and a scaling regimen for injected [18F]FDG activity. With the implementation of these recommendations it can be possible to obtain images with increased quantitative value while delivering less dose to patients and maintaining a uniform level of image quality between different patients.