PhD student, University of Manitoba


Evaluation of geometrical variables on the performance of positron emission tomography scanners

Medical imaging modalities can be divided into two groups: anatomical (e.g. magnetic resonance imaging or MRI) and functional imaging (e.g. positron emission tomography or PET) modalities. While an anatomical modality produces images regarding the structure of the body, functional imaging reveals information on the metabolism of each organ. PET is one of the most widely-used functional modalities which has clinical applications in areas such as oncology and neurology. To perform a PET scan, a radiotracer (a positron emitter radionuclide bound to a biologically active molecule such as glucose) is injected into the patient's body such that it accumulates in specific organs. As the decay of the radionuclide happens, gamma photons will be emitted which are being detected by rings of gamma detectors around the patient. The exact spatial and temporal information of the detected photons provides a basis for reconstructing an image of the radiotracer distribution which in turn represents the functionality of the target organ. The images obtained from a PET scan are typically difficult to interpret due to the absence of anatomical landmarks. Therefore, PET acquisition is often done along with an anatomical modality acquisition which is termed 'hybrid imaging'. The anatomical images provide invaluable information that can be used in clinical diagnosis. Also, the acquired anatomical images can be used to improve the quantitative accuracy of the reconstructed PET images. Simultaneous acquisition of PET and MRI (PET/MRI) is one of the most sophisticated techniques in state-of-the-art hybrid imaging. One of the approaches to simultaneous PET/MRI is to build a so-called 'PET insert' for an existing MRI machine. A PET insert is a PET scanner that can be retrofit into an existing MRI machine to facilitate simultaneous PET and MRI imaging. A PET insert has several advantages over a fully integrated PET/MRI, such as: it can be designed and built for any existing standalone MRI scanner and it is cost-effective. We are now designing a human brain-dedicated PET insert that can be retrofit into the Siemens Magnetom 7 Tesla Brain scanner (an ultra-high field brain-dedicated MRI scanner) located in London, Ontario, Canada. The specific goal of the project is to find the optimum set of geometrical variables for the PET insert 's detectors that can maximize the system resolution while maintaining other performance metrics of the scanner as high as possible.