New Chemistry Techniques Improve Hybrid Scanner Performance

"Our system shows great promise because it is able to simultaneously provide the complementary strengths of PET and MRI in imaging rats and small animals," said Mitsuaki Tatsumi, associate professor of radiology at Osaka University Graduate School of Medicine and Medical Hospital, Osaka, Japan. "This ability opens up exciting new opportunities in research in terms of increased understanding of kinetics, biodistribution of radiopharmaceuticals and, eventually, disease characteristics and physiological processes. Next steps include imaging body tumors in rats or mice and developing PET/MRI systems that can image people."

A combined PET/MRI system delivers specific molecular information related to cell surface reactors, enzymes and gene expression that PET provides as well as important anatomical data, soft-tissue contrast and information about perfusion and permeability shown in MRI—at the same time.

The new combined PET/MRI system is a step forward from previous combined systems because it can image the bodies of rats and mice rather than just the brains. The system consists of depth-of-interaction block detectors and a permanent magnet for MRI.

In the study, researchers injected rats with the radionuclide C-11 methionine for PET imaging and with Gadoxetate for contrast MRI imaging. Simultaneous PET and MR imaging was performed from head to abdomen. PET, MR and co-registered fusion images were then evaluated for image quality.

The simultaneous PET/MRI system provided quality images in spite of the short half-life of C-11. The images showed excellent mapping of the liver and kidneys. C-11 methionine is known to accumulate in the pancreas, but it would have been difficult to image without clear mapping MR images. The use of Gadoextate as a contrast agent enhanced the power of the integrated PET/MRI system.