Detecting Brain Micrometastases Using Positron Emission Tomography

Metastasis of cancer to the brain is a leading cause of mortality in cancer patients, while early detection and treatment of micrometastases remains a difficult problem in oncology. In our study, we will use positron emission tomography (PET), a technique for imaging molecular events associated with cancer, to monitor a murine model of metastatic melanoma.  Because PET can detect radiotracers with nano- to picomolar concentrations, and because the resolution of PET is approximately the same size as the micrometastases, we hypothesize that a common molecular probe designed to image cell proliferation (3′-deoxy-3′-[₁₈F]fluorothymidine (FLT)) can be used to image micrometastases. We used an iterative algorithm to reconstruct 0.8mm and 0.4mm resolution images from three sets of mice PET scans.  For each reconstructed image set, coregistered magnetic resonance (MR) images provide a reference to locate micrometastases. We will measure the number of micrometastases visible in the reconstructed PET and MR scans and compare between different reconstruction resolutions and the MR images.  While preliminary qualitative observations indicated no difference in visibility of micrometastases, further results and future work with phantoms may provide more insight into the nature and detection of micrometastases. By improving early detection and treatment of metastases, rates of morbidity and mortality associated with metastatic cancer should improve.