Positron emission tomography (PET) is a sensitive imaging method to study biochemical and molecular mechanisms of health and diseases in the human body. A drawback is the lack of details (resolution) in the PET images. Hybrid PET/CT scanner acquire PET and high resolution CT images of the same patient back-to-back so that PET images can be overlaid on CT images to allow correlation of anatomy with biochemical and molecular function. We are also exploiting another synergy of PET/CT scanners.

T.-Y. Lee
PET imaging, tracer kinetics modeling, stroke imaging
A. So
Cardiac Imaging
E.E. Stewart
cancer (liver) imaging
G. Wisenberg
J.A. White

Cyclotron & PET Radiochemistry
Molecular Imaging


Future Directions

Compartment analysis of acquired PET dynamic data is required to maximize the information derived from PET scanning. We are investigating the approach of using CT perfusion to estimate the delivery and transfer rate of PET probes across the endothelial barrier to reduce the number of parameters to be estimated from the compartmental analysis and hence improve the reliability of estimate parameters.

With improved compartmental analysis, we will investigate the involvement of the sympathetic nervous pathways in heart failure.

Key Accomplishments

The CT scanner in a hybrid PET/CT scanner can be used to measure tissue perfusion which can be used to complement the biochemical and molecular function from PET scanning. We are exploiting this synergy of the hybrid scanner in the following applications:

Assessing tumour hypoxia in cancers:  Hypoxia, which upregulates a number of molecular processes in tumours, can lead to resistance to treatment and metastatic spread. There is a lack of simple imaging procedures to image tumour hypoxia. PET hypoxic probes are not approved for clinical tumour imaging. In contrast, [18F]fluorodeoxyglucose (FDG) is now widely used to detect cancer via increased glycolytic activity of tumours. Our hypothesis is that increased glycolytic activity (usage of oxygen) coupled with low perfusion (delivery of oxygen) will lead to hypoxia. Figure demonstrates the mismatch between perfusion and FDG uptake (glycolytic activity) in a rabbit liver tumour model.

Investigating the mechanisms of vascular cognitive impairment.  Stroke and dementia are known risk factors for each other. We will use CT Perfusion and PET imaging with the new ligands, 11C-[R]-PK11195 and AV-45 to measure brain perfusion and to assess inflammation and amyloid burden in the brain of stroke patients serially. These imaging markers will be correlated with psychometric testing to dissect the interaction among ischemia, inflammation and amyloid toxicity in the induction of cognitive decline in stroke patients.

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