Ultra-high field MRI (3 teslas and more)
Learning objectives
After reading this chapter, you should be able to:
- State the consequences of increasing the magnetic field on signal-to-noise ratio, relaxation times, SAR, artifacts, acoustic noise
- Describe the necessary adaptations in sequence parameters and equipment
- Set out the advantages and disadvantages of increasing magnetic field
- List the potential fields of application of ultra high field MRI
Key points
3,0 T vs 1,5 T | Advantages & Applications | Disadvantages & Solutions | |
SNR | ↑ | ↑ image quality ↑ speed ↑ spatial resolution | ↑ |
T1 | ↑ ~ | ↑ blood/tissue contrast TOF MRA ↓ Gadolinium doses | ↑ TR or ↓ signal Modification of tissue contrasts Magnetization preparation (inversion, MP…) |
T2 | ? | ↑ | Drop in signal ↓ TE |
SAR | ↑↑ | ↑ | RF energy deposited (SAR limit) Parallel acquisition ↓ flip angle, echo train, number of slices ↑ TR |
Chemical shift | ↑ | ↑ differences in resonance frequency Better fat suppression Spectroscopy | Chemical shift artifacts ↑ bandwidth Fat signal suppression Adaptation of in-phase / out-of-phase TE |
Magnetic susceptibility | ↑↑ | Greater sensitivity to magnetic susceptibility Better detection of hemorrhages Perfusion MRI (DSC MRI) Functional MRI (BOLD) | Magnetic susceptibility artifacts Parallel acquisition ↓ TE |
Dielectric effects | ↑ | ↑ | RF heterogeneities, variable signal loss in the image Optimization of coils, Parallel RF transmission |
Acoustic noise | ↑ | ↑ | Vacuum magnet housing Headphones, gradient downgrade |
References
- Willinek and Kuhl. 3.0 T neuroimaging: technical considerations and clinical applications. Neuroimaging clinics of North America. 2006 May;16(2):217-28, ix.
- Tanenbaum. Clinical 3T MR imaging: mastering the challenges. Magnetic resonance imaging clinics of North America. 2006 Feb;14(1):1-15.
- Heidemann, Seiberlich. Perspectives and limitations of parallel MR imaging at high field strengths. Neuroimaging clinics of North America. 2006 May;16(2):311-20, xi.
- Voss, Zevin. Functional MR imaging at 3.0 T versus 1.5 T: a practical review. Neuroimaging clinics of North America. 2006 May;16(2):285-97, x.
- Merkle and Dale. Abdominal MRI at 3.0 T: the basics revisited. Ajr. 2006 Jun;186(6):1524-32.
- Mosher. Musculoskeletal imaging at 3T: current techniques and future applications. Magnetic resonance imaging clinics of North America. 2006 Feb;14(1):63-76.
- Gutberlet, Noeske. Comprehensive cardiac magnetic resonance imaging at 3.0 Tesla: feasibility and implications for clinical applications. Investigative radiology. 2006 Feb;41(2):154-67.