Simultaneous PET/MRI images acquired with an RF-transmissive PET insert

The combination of PET´s high sensitivity for visualizing and quantifying molecular signatures and MRI´s exquisite anatomical soft tissue contrast holds great promise for improving diagnosis and characterization of disease. However, the prohibitively high cost of integrated clinical PET/MRI systems presents a significant barrier to entry for simultaneous PET/MRI imaging studies. To address this problem, a prototype brain-size PET insert that can be placed in the bore of any existing MRI without modifications to the latter has been designed. It comprises a ring of 16 electrically floating battery-powered detector modules separated by small gaps, thereby allowing RF signals from the MRI to pass through the PET ring with relatively little attenuation. Currently, the MRI body coil is used to both transmit and receive RF signals through the PET insert. The insert transmits PET data out of the MRI bore using electro-optical signal transmission technology, employing optical fibers that aren´t susceptible to MRI interference. A 3D printed resolution phantom with cold and hot rods was imaged with 4 out of 16 complete PET detector modules in the bore of a 3T clinical MRI system, during various MRI pulse sequences. Results of the first simultaneous PET/MRI imaging trials with this technology indicate that PET tomographic image data can be successfully acquired during a variety of different MRI pulse sequence types, with some effect on PET image quality. The PET insert´s simultaneous imaging capability and compatibility with existing MRI systems could allow much wider accessibility to simultaneous PET/MRI imaging.