PET/MR challenges PET/CT as ‘go to’ modality in oncology

A new hybrid technology emerged at radiology’s mega conference in Chicago earlier this month, one that may dislodge decade-old PET/CT from its prominent berth for the diagnosis and monitoring of cancer patients. This new modality combines the positron-imaging component of PET/CT with oncology’s premier anatomic modality, MR, opening the door to cancer images with unprecedented clarity and clinical value.

Siemens, GE, and Philips showed versions of the new hybrid at the 2010 meeting of the Radiological Society of North America. Siemens displayed the most elegant design with its Biograph mMR (molecular MR) that has a PET ring detector built into the bore of a 3T magnet. Head-to-toe images fused MR and PET data to show anatomy and function in the brain, spine, abdomen, and extremities and to demonstrate potential in oncology, as well as pediatric and neuro imaging.

“This is the world’s first fully integrated whole-body molecular MR system,” said Walter Mrzendorfer, chief executive officer of Siemens MR, “meaning that a solid-state PET camera is integrated into the isocenter of a 3T MR scanner, allowing simultaneous acquisition of MR and PET data.”

Philips took a different design approach with its Ingenuity TF PET/MR, lining up two scanners, one for MR and the other for PET, with a patient table in between. In a scene reminiscent of a railroad roundhouse, a patient table was mounted atop a turntable embedded in the floor of the Philips RSNA booth. The table turned 90° from a neutral patient-loading position to slide into one scanner. It then retracted, turned 180°, and slid into the other scanner. The scanner then retracted, and the patient table finally turned 90° back to the neutral, patient-loading position.

Images displayed in the Philips booth, obtained by investigators in early tests using the experimental Ingenuity TF PET/MR, clearly showed breast and prostate cancers. “There is no mistaking where the lesions are,” said Dominic Smith, Philips’ global vice president for CT and nuclear medicine. He noted that luminaries are also looking into characterizing plaques found in blood vessels and at brain anatomy and function.

The in-line Philips system is not yet commercially available in the U.S. and will remain a work-in-progress pending FDA review, according to the company, as will Siemens’ Biograph mMR. The Siemens PET/MR may be commercially available first under a CE label in the European Union in the second half of 2011.

Unlike Siemens and Philips, GE is actively selling its version of PET/MR, thanks to a patient table that docks with the company’s FDA-cleared MR and PET/CT scanners. Where the MR and PET/CT scanners are located doesn’t matter so long as the patient can be rolled from one to the other on the table. GE’s software does the heavy lifting, registering and fusing the data sets from the two exams.

Combining just the data rather than the equipment offers a “financially responsible solution for our customers,” said Vivek Bhatt, GE’s general manager of PET. Freestanding scanners can be used flexibly within a department, applying the PET/CT and MR pieces individually to handle routine clinical cases, then using them together to conduct research.