Simultaneous 15O-PET and MRI of cerebral blood flow and cerebrovascular reserve

Continuous blood flow to the brain is needed for neural tissues to survive. Noninvasive imaging of cerebral blood flow (CBF) in humans is challenging, but is critically useful to understand normal brain physiology and to help patients with cerebrovascular disorders such as stroke.

Unfortunately, current accepted techniques to measure CBF with oxygen-15 positron emission tomography (PET) are not useful in clinical settings. These methods require specialized and costly hardware that is not available in most hospitals. On the other hand, MRI scanners are more readily available at these sites. Arterial spin labeling (ASL) is an emerging MRI technique that magnetically labels blood flowing into the brain to measure CBF. ASL is noninvasive and may provide higher-quality images of CBF compared to PET.

Before ASL can be widely adopted, however, it must be validated against PET, especially in patients with abnormal arteries. Thus, the main goal of the study is to provide an MRI tool to image CBF that has been validated against the PET reference standard.

To achieve this goal, we will use the new simultaneous MR-PET scanner at the Lucas Center for Imaging at Stanford, one of fewer than 50 such systems in the world. This unique system allows us to make simultaneous CBF measurements by MRI and by PET to avoid variability between scan sessions. We will study patients with Moyamoya disease, a progressive disorder in which arteries at the base of the brain are blocked, leading to high risk of stroke. Blood in these patients flows through diseased arteries in the brain that will allow us to test ASL even in the most challenging of cases.

This project represents a multidisciplinary effort of imaging scientists, radiochemists, radiation safety experts, and neurosurgeons. We aim to provide a robust, validated MRI method to image blood flow in the human brain. If ASL can replace PET for CBF measurements, clinicians and scientists would gain a valuable neuroscience tool to study brain function and how it is disturbed in disease.