vertical_mri [Neurosurgery Wiki]

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[[Patient]]s with active [[implant]]s such as [[deep brain stimulation]] (DBS) devices are often denied access to [[MRI]] due to [[safety]] concerns associated with the [[radiofrequency]] (RF) heating of their [[electrode]]s. The majority of studies on RF heating of conductive [[implant]]s have been performed in horizontal close-bore MRI scanners. Vertical MRI scanners which have a 90° rotated transmit coil generate fundamentally different electric and magnetic field distributions, yet very little is known about RF heating of implants in this class of scanners. Kazemivalipour et al. performed numerical simulations as well as phantom experiments to compare RF heating of DBS implants in a 1.2T vertical scanner (OASIS, Hitachi) compared to a 1.5T horizontal scanner (Aera, Siemens).

Simulations were performed on 90 lead models created from post-operative CT images of patients with DBS implants. Experiments were performed with wires and commercial DBS devices implanted in an anthropomorphic phantom.

They found a significant reduction of 0.1 g-averaged specific absorption rate (30-fold, P < 1 × 10-5 ) and RF heating (9-fold, P < .026) in the 1.2T vertical scanner compared to the 1.5T conventional scanner.

Vertical MRI scanners appear to generate lower RF heating around DBS leads, providing potentially heightened safety or the flexibility to use sequences with higher power levels than on conventional systems
((Kazemivalipour E, Bhusal B, Vu J, Lin S, Nguyen BT, Kirsch J, Nowac E, Pilitsis J, Rosenow J, Atalar E, Golestanirad L. Vertical open-bore MRI scanners generate significantly less radiofrequency heating around implanted leads: A study of deep brain stimulation implants in 1.2T OASIS scanners versus 1.5T horizontal systems. Magn Reson Med. 2021 May 7. doi: 10.1002/mrm.28818. Epub ahead of print. PMID: 33961301.))
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Golestanirad L, Kazemivalipour E, Lampman D, Habara H, Atalar E, Rosenow J,
Pilitsis J, Kirsch J. RF heating of deep brain stimulation implants in open-bore 
[[vertical MRI]] systems: A simulation study with realistic device configurations.
Magn Reson Med. 2019 Nov 2. doi: 10.1002/mrm.28049. [Epub ahead of print] PubMed 
PMID: 31677308.