MRI/PET Machines Hit Mainstream

Design and structure improvements in PET and MRI scanners could soon alter how you practice nuclear medicine. These changes have made combining the scans for clinical treatment a possibility, according to a presentation at this week’s Society of Nuclear Medicine (SNM) annual meeting in San Antonio.

The PET/MRI combination scanner first appeared in the mid-1990s in mouse-model cancer research conducted at the University of California-Davis (UC-Davis), but using it clinically has been impossible until now. Not only have MRI magnets distorted colors and images from nearby PET scanners, but there also hasn’t been enough space inside an MRI to accommodate a PET. 

Those problems no longer exist. Using LCD screens instead of CRT screens in PET scanners prevents image distortion, and installing higher-performing gradients frees up space – 70 cm rather than 55 cm – to install a PET inside an MRI, says Bruce Rosen, M.D., Ph.D., radiology professor at Harvard Medical School and director of the Athinoula A. Martinos Center for Biomedical Imaging at Massachusetts General Hospital. The wider space also reduces anxiety for patients who are claustrophobic.

Given these changes, companies, including Siemens and GE, are now working to commercialize combination scanners.

“It’s important that the technology is now advanced so these scans can play well together,” says Rosen, who delivered the SNM’s PET/MRI presentation. “Running tests simultaneously lets radiologists diagnose a problem and see how it’s working real-time. It can also save patients the inconvenience of having tests at different times.”

Installing combination scanners, which have not yet received Food & Drug Administration approval, would bolster efforts to control radiation exposure, especially in pediatric patients, Rosen says. Additionally, a PET/MRI scan, rather than a PET/CT, would produce better images in the bone-dense pelvic, head, and neck areas, leading to more accurate diagnoses and treatments. The biggest advances, however, could eventually be in neuroscience, neurobiology, and neurological disease, specifically Alzheimer’s.

“There are many people who have biomarkers for the disease, but they are asymptomatic,” Rosen says. “Using a PET/MRI could help us diagnose people earlier so we can start treatment sooner. This could have a significant impact on how we view Alzheimer’s.”

It will take time, however, to learn when the PET/MRI would work best and when you should use the PET/CT instead, Rosen says.

Despite their potential clinical roles, the machines’ high cost and increased size would make it difficult for many practices to adopt the technology, says Simon Cherry, Ph.D., the UC-Davis biomedical engineer focused on molecular imaging who developed the PET/MRI prototype. He also cautions that the complexity of operating a combination scanner might require additional training for your technicians.

Cherry agrees, however, that using a PET/MRI could improve nuclear medicine protocols for radiologists, as well as enhance the treatment patients receive.

“It’s great to see something that started so long ago make it the patient,” Cherry says. “When we have the opportunity to improve patient health, it’s a fantastic thing. This is what all of us go into the field of imaging to do.”