Room: Exhibit Hall | Forum 8
Purpose: The first FDA-cleared 7T clinical MRI scanner was released in 4th quarter 2017. This paper describes initial experience with this new scanner technology, including siting/installation issues, development of a safety program, and quality testing/validation.
Methods: 7T MRI represents the largest jump in magnetic field strength since MRI was first introduced in the 1970â€™s. Integration of this new technology into a routine hospital environment involved alterations to conventional siting requirements for the larger magnet and associated equipment, facility ergonomics related to patient handling and throughput, and the need for new quality control testing and safety procedures.
Results: 124 mÂ² of facility space was used to comfortably house the magnet and additional equipment cabinets (for 3rd order B0 shimming, 2x cryocoolers, 8x 2kW RF amplifiers, control electronics for parallel Transmit, RF power meters). Up to 13 mm of steel shielding in the closest wall (3 m from isocentre) was required to reduce the fringe field to below 0.5 mT (5 G) in an adjacent public corridor. Modified QC test phantoms, with dielectric properties to ensure adequate coil loading and to minimize B1+ transmit non-uniformities, were used for image quality and specific absorption rate (SAR) validation. Modified facility safety procedures adopted a three-pronged approach to mitigating risk: ferromagnetic detectors at the door into Zone 4, pocket-less scrubs for staff working in Zones 3 and 4, and a ban on loose ferromagnetic items on open surfaces in Zone 3. Policies on the scanning of tattoos and passive implanted devices, and the mitigation of risk from patient instability due to vestibular activation (Bâ‚€ and strong field gradients), were developed.
Conclusion: The 7T scanner required a longer installation time compared to lower-field scanners and modified testing procedures. Additional safety concerns at 7T justify the adoption of additional operational and patient scanning safety procedures.