Custom MRI Tracks Blood Flow During Exercise

A standard MRI test can measure a stationary patient’s blood flow at rest. After several years of collaboration a new method of blood flow measurement has been developed: a type of MRI that uses an imaging test for patients who are not lying still. In 1997 Stanford obtained a vertically open MRI, and Charles Taylor, PhD, professor of surgery and mechanical engineering and Robert Herfkens, MD, professor of radiology began work on developing a custom exercise cycle for the machine. They assigned the project to an engineering class at Stanford, and the final prototype was completed by Chris Cheng, a doctoral student, in 2003.

The cycle, made of mostly beech wood and high-density plastic, is streamlined and light weight at 80 pounds. The design allows the patient to pedal at various speeds therefore increasing their heart-rate and blood flow. In previous methods of obtaining blood flow measurements at accelerated heart rates, such as the insertion of invasive probes and catheters in the femoral artery, the presence of the probes could disrupt the current or course of the blood being monitored. Another strategy attempting this feat involved an MRI immediately succeeding a patient’s workout, although this often yielded inconsistent or inaccurate results.

This revolutionary method allows for the noninvasive study, observation, and comparison of differences in blood flows between healthy patients and those ailed with various vascular diseases. Some vascular disorders show normal blood flow activity in the patient’s inactive state but symptoms or abnormal activity when stimulated by exercise. This new MRI model involves a belt-like device to stabilize the patient’s torso against the plastic seat and a coil to detect and monitor the movement of blood in the thoracic and abdominal aorta. The data gathered can be deciphered and interpreted by Cheng’s specialized software into how quickly the blood is passing through the artery (spacial description) and the amount of force exerted.

The cycle is now being used on patients with intermittent claudication – a condition that involves an obstruction in the blood flow to the legs causing pain and stiffness, and on children diagnosed with congenital cardiovascular disease to monitor blood flow after treatment. In the future this technique may be used to diagnose patients with vascular diseases, claudication, or weakness of the heart at earlier stages in the disorder’s development or prior to much pain.

Stanford Report, January 22, 2003

http://news-service.standard.edu/news/2003/january22/mri.html