A volunteer exercised on the treadmill before being placed on cushions that molded to her body during at-rest MR imaging. The test was conducted on a prototype system developed by Ohio State University. Video courtesy of Orlando Simonetti, PhD, and Ohio State University.
"It is important that not only are the patients' respective heart rates at a level that indicates they are at maximum stress, but that the stress-induced defects have not disappeared," Simonetti said.
OSU researchers have tested the MRI treadmill on more than 100 patients. To gauge the efficacy of the technology, they evaluated 43 patients between the ages of 25 and 81 who underwent imaging procedures with both technetium-99m SPECT and gadolinium-enhanced cardiac MRI at stress and at rest.
The results, published July 2010 in the Journal of Cardiovascular Magnetic Resonance, found that stress cine cardiac MRI was completed in 68 ± 14 seconds following the end of exercise, while stress perfusion cardiac MRI was completed in 88 ± 8 seconds.
First-pass MRI perfusion immediately following maximum treadmill exercise stress. Image indicates prominence of septal perfusion defect induced by exercise stress. Image courtesy of Orlando Simonetti, PhD.
Accuracy in patients who underwent coronary angiography was seven of eight (87%) patients for cardiac MR and five of eight (63%) patients for SPECT. Follow-up at six months indicated there were no cardiac events for 29 of 29 (100%) patients who had a negative cardiac MRI and for 33 of 34 (97%) patients with negative SPECT results.
The study, led by Dr. Subha Raman, concluded that exercise stress cardiac MR including wall motion and perfusion "is feasible in patients with suspected ischemic heart disease."
The authors added that larger clinical trials should be conducted to compare the efficacy of the stress imaging system with other stress imaging modalities.
Simonetti and three other OSU co-inventors of the MRI treadmill have taken their technology toward the commercial arena by forming EXCMR. The company received a small business technology transfer grant from the U.S. National Institutes of Health in September 2009, just three months after hiring its first employee.
In August 2010, EXCMR was awarded a grant from the Ohio Third Frontier Medical Imaging Program, which provided $1.4 million and an additional $1.4 million in matching funds from collaborators.
The grant will fund a multicenter trial in which MRI-compatible treadmills will also be installed at Case Western Reserve University, University of Pittsburgh Medical Center, and the Christ Hospital in Cincinnati.
The trial will seek to scan approximately 450 patients with this technique in a head-to-head comparison with SPECT, using coronary angiography as the gold standard.