Flow velocity measurement with ac gradients

• Published in: Magnetic resonance in medicine Vol. 4; no. 3; p. 274
• Main Authors: Walton, J H, Conradi, M S
• Format: Journal Article
• Language: English
• Published: United States 01-03-1987
• Subjects: Blood Flow Velocity - methods; Fourier Analysis; Magnetic Resonance Spectroscopy - methods; Mathematics; Models, Structural; Rheology - methods
• ISSN: 0740-3194
• DOI: 10.1002/mrm.1910040308

Two NMR experiments are described that use ac field gradients to measure flow velocities. Both experiments perform no spacial localization; instead, fluid velocity is converted to a resonance frequency shift. Thus, by Fourier transformation of a single FID or echo train the distribution of velocities is available. The first experiment uses only one rf pulse but requires a homogeneous static field. The second experiment uses the CPMG multiple-pulse sequence to refocus the effects of field inhomogeneity and chemical shifts. Results are shown for both experiments using a simple flowing phantom. Applications of the techniques to time-resolved blood flow measurement are discussed.