Magnetic resonance angiography techniques

R. R. Price, J. L. Creasy, C. H. Lorenz, C. L. Partain

Research output: Contribution to journalArticlepeer-review


After a radio frequency pulse, the decay of the magnetic resonance (MR) signal is described by two relaxation processes, T1 and T2. T1 describes the rate at which the magnetization realigns itself along the external magnetic field direction (M(L)), and T2 describes the rate of decay of the magnetization component along the transverse axis (M(T)). Magnetic resonance angiography (MRA) sequences have been developed that encode flow as changes in the apparent T1 or T2 of the moving blood relative to stationary tissues. MRA sequences typically use either time-of-flight (TOF) techniques to encode T1 or phase-contrast techniques to encode T2. TOF techniques encode flow as an apparent T1 shortening through the wash-in of fully relaxed blood from outside the image volume. The shorter T1 produces an enhancement of vascular structures relative to stationary tissues. TOF methods may use either sequential two-dimensional, three-dimensional, or multi-slab three- dimensional imaging sequences to produce a three-dimensional MRA data set. Phase-contrast methods use additional magnetic field gradients to encode flow as shifts in the phase of M(T). Both TOF and phase-contrast methods use maximum intensity projection (MIP) images displayed in a cine format to aid in the visualization of three-dimensional vascular structures.

Original languageEnglish (US)
JournalInvestigative Radiology
Issue numberSUPPL. 2
StatePublished - 1992
Externally publishedYes


  • magnetic resonance angiography
  • phase contrast
  • time of flight

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology


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