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3T MRI

Ultra-high field MRI (3 teslas and more)

Denis Hoa

學習目標

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

重點

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

參考資料

  1. Willinek and Kuhl. 3.0 T neuroimaging: technical considerations and clinical applications. Neuroimaging clinics of North America. 2006 May;16(2):217-28, ix.
  2. Tanenbaum. Clinical 3T MR imaging: mastering the challenges. Magnetic resonance imaging clinics of North America. 2006 Feb;14(1):1-15.
  3. 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.
  4. 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.
  5. Merkle and Dale. Abdominal MRI at 3.0 T: the basics revisited. Ajr. 2006 Jun;186(6):1524-32.
  6. Mosher. Musculoskeletal imaging at 3T: current techniques and future applications. Magnetic resonance imaging clinics of North America. 2006 Feb;14(1):63-76.
  7. 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.