Table 1.

Technical requirements, performance, and costs/availability for motion correction methods.

METHOD	System Requirements	Motion tracking (temporal and spatial resolution)	B0 field tracking (temporal and spatial resolution)	Performance, costs and availability
Retrospective: Post-processing	Custom post-processing software	No localization update	Temporal resolution is determined by the TR of MRS sequence	Lower cost of software solution
Prospective: Navigators	Custom MR sequence, on-line reconstruction and real-time feedback	0.05–0.1 mm & 0.05–0.1 deg tracking accuracy, 300–1000 ms update rate	0.05–0.1 mm & 0.05–0.1 deg tracking accuracy, 300–1000 ms update rate	Lower cost of software solution
Prospective: External tracking (optical and NMR probes	Additional hardware and software, integration with MR scanner	0.005–0.1 mm & 0.003–0.1 deg tracking accuracy, 12–30 ms update rate	No field update is possible without additional frequency navigators	Higher costs for commercial and custom-made systems
Prospective: NMR probes	Additional hardware and software, integration with MR scanner	0.01–0.1 mm & 0.01–0.1 deg tracking accuracy, 300–1000 ms update rate	Field is measured outside the head, and computational EM modelling can approximate the internal field with limited accuracy.	Higher costs for commercial and custom-made systems