ISMRM presentations demonstrate expanding reach of MR

May 29, 2007

Research developments showcased the future of MR last week in Berlin, as Siemens demonstrated the feasibility of creating a hybrid of this modality with PET, while GE Healthcare exhibited the potential of 3T MR in virtual colonography.

Research developments showcased the future of MR last week in Berlin, as Siemens demonstrated the feasibility of creating a hybrid of this modality with PET, while GE Healthcare exhibited the potential of 3T MR in virtual colonography.

Siemens Medical Solutions displayed the first brain images produced with a prototype MR/PET scanner at its booth at the International Society for Magnetic Resonance in Medicine meeting. The prototype, currently in development at a Siemens laboratory, integrates a PET detector into the bore of a 3T scanner.

In a Trio MR scanner, five LSO-APD block detectors formed 32 cassettes that were arranged axially, creating a field-of-view of 19 cm and an inner ring diameter of 35.5 cm. A standard bird cage transmit/receive head coil was mounted on the scanner bed and placed inside the PET detector to allow the simultaneous acquisition of PET and MR data.

Phantom and human studies conducted at the lab by researchers from the University of Tübingen, the Max Planck Institute for Brain Research in Frankfurt, and the University of Tennessee proved the feasibility of the hybrid scanner. Because the PET detector appeared invisible during MR data acquisition, images showed only the MR and PET data. The detector also had no effect on either MR spectroscopy or MR signal-to-noise ratios, the researchers said. More extensive testing using clinical subjects is expected to begin later this year.

The colonography study documented that parallel imaging at 3T produces spatial resolution sufficient to image the entire colon, capturing artifact-free images with breath-hold scans. Although MR colonoscopy uncovered fewer lesions than optical imaging, the researchers demonstrated that the MR-based procedure was feasible by generating high-resolution diagnostic colonography images without significant motion or parallel imaging artifacts.

"The reconstructed parallel imaging data exhibited diagnostic image quality with no visible SNR degradation," said Anja C.S. Brau, Ph.D., senior scientist in the MR body and vascular group at the global applied science laboratory of GE Healthcare.

Four men and three women at high risk for colon cancer because of prior polyps or family history underwent MR scans at Stanford University. The scans included oblique coronal 2D single-shot fast spin-echo scouts for monitoring colonic water insufflation (approximately 2000 mL) and a dedicated colonic 3D steady-state free precession (SSFP) volume to obtain high-quality localization and diagnostic images. One-D and 2D-accelerated 3D T1-weighted fat-suppressed spoiled gradient echo data were then acquired in the oblique coronal plane before and after intravenous contrast administration.

Brau and colleagues next plan to investigate the potential of MR colonoscopy with higher acceleration factors and correlate the findings with conventional colonoscopy.