PET/MR will start in oncology, then move to cardiology
Mount Sinai has been alpha and beta testing the hybrid system for two years in collaboration with Philips. Fayad and colleagues, along with researchers at the University Hospital of Geneva in Switzerland, submitted data to the FDA in November from 75 oncology cases comparing the new modality to PET/CT.
"We have evaluated the system for the optimization of imaging protocols and acquisition of diagnostic quality whole-body images in a clinically acceptable timeframe," said Fayad, director of the Translational and Molecular Imaging Institute and a professor of radiology and cardiology at Mount Sinai. "The results are promising."
The Ingenuity TF hybrid combo is actually two separate scanners in one room with a table that rotates 180 degrees for sequential imaging in either scanner. It is the first such whole-body scanner to receive approval in any market. The cost is upwards of $4 million.
"From the patients' perspective, it is ideal. They need only deal with one scheduler and one appointment, because it is one test essentially," he said.
But Fayad's research heart is, well, in the heart. He said the combination of PET and 3T MRI is ideal for imaging atherosclerosis.
"PET will show us the amount of inflammation that is present in arterial plaque, the metabolic activity, while MRI, with its high spatial resolution and excellent tissue contrast, will help characterize the plaque into its various components, such as lipids and collagen," he said.
"We feel the two modalities are extremely synergistic and additive and together they resolve disadvantages inherent to each test when used alone."
In addition, MRI can evaluate viability and other functional parameters to determine if "hot spots" on PET correlate with decreased or compromised cardiac ability.
Fayad said that the hybrid system will initially make its cardiovascular mark in the carotid vasculature, and then move on to the coronary arteries.
While there has been momentum as of late to better characterize plaque with optical coherence tomography (OCT) and virtual histology intravascular ultrasound (VH-IVUS), those techniques are invasive and require patients to be admitted to the hospital.
"With PET/MR, the patient can walk into the outpatient center, be scanned and go home within an hour," Fayad said. "It's a powerful model and, quite frankly, paradigm shifting."
At the 2010 Radiological Society of North America (RSNA) conference in Chicago, Siemens Healthcare showcased its entry into the PET/MR market, the Biograph mMR, a combination 3T MRI and PET scanner housed in one unit. Unlike the Philips model, which scans patients sequentially, the Siemens hybrid scanner images patients simultaneously or separately. The company expects CE mark in late 2011. It is not yet approved in the U.S.
Also at last year's RSNA meeting, GE Healthcare showcased software that seamlessly fused images from a separate FDA-approve MRI scanner and an FDA-approved PET/CT scanner. The two scanners are placed in close proximity and the table is wheeled between them.
Osman M. Ratib, MD, PhD, chair of radiology and head of nuclear medicine at University Hospital of Geneva, presented preliminary results at the 2010 RSNA meeting from the Ingenuity TF PET/MR system being used in several oncologic indications including lymphomas, head and neck tumors, prostate and breast tumors as well as lung and colon cancers.
He reported no differences in image quality or identification of abnormal lesions between PET/MR and PET/CT.