Effects of physiologic waveform variability in triggered MR imaging: theoretical analysis.

Department of Medical Biophysics, University of Western Ontario, Canada.
Journal of Magnetic Resonance Imaging (Impact Factor: 2.79). 11/1994; 4(6):853-67. DOI: 10.1002/jmri.1880040618
Source: PubMed

ABSTRACT One of the assumptions inherent in most forms of triggered magnetic resonance (MR) imaging is that the pulsatile waveform (be it cardiac, respiratory, or some other) is purely periodic. In reality, the periodicity condition is rarely met. Physiologic waveform variability may lead to image artifacts and errors in velocity or volume flow rate estimates. The authors analyze the effects of physiologic waveform variability in triggered MR imaging. They propose that this variability be treated as a modulation of the underlying motion waveform. This report concentrates on amplitude modulation of the velocity waveform, which results in amplitude and phase modulation of the transverse magnetization. Established Fourier and modulation theory and the recently described principles of (k,t)-space were used to derive the appearance of physiologic waveform variability artifacts in triggered MR images and to predict errors in time-averaged and instantaneous velocity estimates that may result from such motion effects, including effects such as ghost overlap. Simulations and experimental results are provided to confirm the theory.

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    • "Variability is especially important in ungated procedures such as magnetic resonance angiography (MRA) (Nishimura 1990, Dumoulin 1989) and cardiac-gated cine MRI flow measurements (Pelc et al 1991). In these investigations, data collection may occur over hundreds of cardiac intervals, and cycle-to-cycle variations can lead to artefacts in the final data (Hangiandreou et al 1993, Hofman et al 1993, Lauzon et al 1994, Rogers and Shapiro 1993). We are interested in experimental investigations and numerical simulations of blood flow through the carotid bifurcation. "
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