Improved SNR in phase contrast velocimetry with five-point balanced flow encoding

Kevin M. Johnson, Michael Markl

Research output: Contribution to journalArticlepeer-review

114 Scopus citations


Phase contrast velocimetry can be utilized to measure complex flow for both quantitative and qualitative assessment of vascular hemodynamics. However, phase contrast requires that a maximum measurable velocity be set that balances noise and phase aliasing. To efficiently reduce noise in phase contrast images, several investigators have proposed extended velocity encoding schemes that use extra encodings to unwrap phase aliasing; however, existing techniques can lead to significant increases in echo and scan time, limiting their clinical benefits. In this work, we have developed a novel five-point velocity encoding scheme that efficiently reduces noise with minimal increases in scan and echo time. Investigations were performed in phantoms, demonstrating a 63% increase in velocity-to-noise ratio compared to standard four-point encoding schemes. Aortic velocity measurements were performed in healthy volunteers, showing similar velocity-to-noise ratio improvements. In those volunteers, it was also demonstrated that, without sacrificing accuracy, low-resolution images can be used for the fifth encoding point, reducing the scan time penalty from 25% down to less than 1%.

Original languageEnglish (US)
Pages (from-to)349-355
Number of pages7
JournalMagnetic resonance in medicine
Issue number2
StatePublished - Feb 2010


  • Flow quantification
  • Phase contrast
  • Signal to noise
  • Vascular hemodynamics
  • Velocity mapping

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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