Ultrahigh field MRI

Ultrahigh field (UHF) magnetic resonance imaging refers to imaging done on any MRI scanner with a main magnetic field (B0) strength of 7 tesla or greater. Until recently purely a research tool, following the introduction of the first 7 T clinical scanner in 2017, there are now a slowly increasing number of academic centers worldwide with ultrahigh field scanners in clinical use. Several research scanners with even higher field strength than 7 T are in operation .

Advantages

• increased signal-to-noise ratio (SNR)
  • increased spatial resolution
  • increased contrast resolution
  • decreased acquisition time
• increased magnetic susceptibility
  • improved T2*, SWI, BOLD sequences
• increased T1 relaxation time
  • improved time of flight (TOF) MRA
• decreased T2/T2* relaxation time
  • improved BOLD, SWI

Disadvantages

• increase in side effects: dizziness, nausea, metallic dysgeusia, vertigo
• increased magnetic susceptibility
  • image degradation artifacts
• increased specific absorption rate (SAR)
  •  smaller flip angles, longer TRs, prolonged breath holds, decreased slices
• increased T1 relaxation time
  • prolonged acquisition time
• decreased T2/T2* relaxation time
  • DWI/DTI more difficult
• increased data may become computationally heavy