The Cancer Imaging Research Program at Robarts is focused on two areas of research: (1) developing new medical imaging acquisition and analysis tools, and (2) developing new molecular “probes” targeted to detecting specific types of cancer. Both research foci are aimed at providing new information for cancer diagnosis, for cancer treatment and to help develop new cancer treatments.
Molecular Imaging Probes
The aim is to adapt medical imaging methods to improve the specificity – ensuring that the probe preferentially reaches the correct target cancer and not non-target tissue, and sensitivity – improving signal levels so that smaller tumours can be detected. Robarts researchers and colleagues are adapting magnetic resonance imaging and computed tomography to improve earlier detection of tumours of the prostate and liver, when tumours are small and therapy can be more effective. They also are using novel MR methods to track single cells of the immune system, which is early research aimed at using the body's own cells to enhance immunity to target and attack the tumour.
Breast cancer is the most common cancer afflicting Canadian women and the second leading cause of cancer death. It is anticipated that one in eight Canadian women will develop breast cancer in their life-times. The cancer imaging program is developing novel parallel Magnetic Resonance (MR) imaging approaches particularly for younger women for whom conventional X-ray mammography is often inconclusive due to dense tissue. MR imaging does not use ionizing radiation and provides excellent soft tissue contrast and multi-planar cross-sectional images which have been shown to be useful for distinguishing malignant and benign lesions using quantitative dynamic gadolinium-enhanced MR imaging. Unfortunately, the temporal demands placed on dynamic MR imaging methods results in a loss of spatial information (i.e. coverage), which can result in a missed lesion or an incomplete bilateral breast examination, particularly important for directing a breast biopsy. Parallel MRI strategies are being developed to speed up image acquisition and thus allow rapid and quantitative bilateral dynamic contrast enhanced imaging of the entire breast.
When prostate cancer is diagnosed early it is curable, but once the tumour has extended beyond the prostate, the risk of metastases and locally aggressive cancer increases. The cancer imaging program is developing new imaging probes to improve the sensitivity of detection of prostate cancer using magnetic resonance imaging (MRI). In two approaches the probe is bound or trapped within the cancer cells. The probe increases the signal intensity of nearby water molecules enabling detection of the tumour. In a third approach, hyperpolarized carbon-13 contrast agents provide a unique signal that does not have to compete with background signals in the body, and offers the potential to enable detection of aggressive cancers at a much earlier stage. This probe enables direct imaging of elements (e.g. pyruvate) in the metabolic pathways within cells, which are upregulated in aggressive cancer long before the tumour has reached significant size. Robarts researchers are also key participants in the CHIR Team in Image Guidance for Prostate Cancer developing integrated multi-modality imaging for prostate cancer diagnosis and therapy.
Life expectancy for patients with cirrhosis of the liver and hepatocellular carcinoma is short, with fewer than half of patients surviving two years. A factor contributing to poor survival is the inability to detect the cancer when the tumour is less than two centimetres in diameter when patients have a better chance of survival following surgery or a transplant. The aim of this project is to develop more sensitive detection of blood flow in the diseased liver using computed tomography (CT). Hepatocellular carcinoma progresses from cirrhotic nodules to pre-cancerous, regenerative nodules, before becoming cancer. The blood supply for cirrhotic nodules and regenerative nodules is the same as for the normal liver, which is blood flowing out of the gut, whereas hepatocellular carcinoma derives its blood supply from the aorta and its branches. Use of CT will allow the detection of changes in the blood flow pattern that signal the change from pre-cancerous regenerative nodules to liver cancer.
There is considerable interest in harnessing the body’s own immune system to target and attack cancer, and harvested immune cells can be re-introduced into the body (“cell based immunotherapy”) to boost the immune system. There is early evidence that these cell-based vaccines are technically feasible in humans and non-toxic; however, significant barriers remain to be overcome before the use of cell-based vaccines is reliable. The aim of this research is to analyze the trafficking and accumulation of human immune cells in vivo using high resolution MRI and iron oxide based cell labels. For dendritic cell therapy, the team plans to use this strategy to monitor the ability of dendritic cells to boost the immune system. For natural killer cell therapy, they aim to use cell tracking to optimize the accumulation and invasion of these cells in tumours.