N. J. Pelc is a coauthor with D. R. Enzmann of a 1991 study that used phase-contrast magnetic resonance imaging to measure cerebrospinal fluid motion through the cardiac cycle. The work illustrates how magnetic resonance imaging can provide a time-dependent physiological measurement rather than only an anatomical picture.[ref]
Normal flow patterns of intracranial and spinal cerebrospinal fluid defined with phase-contrast cine MR imaging by D. R. Enzmann and others. Radiology178,467–474(1991), originating byline and abstract.
The investigators studied ten healthy volunteers and four patients whose conventional magnetic-resonance images were normal. Peripheral cardiac gating divided the measurement into 16 flow-encoded images per cycle. The flow encoding distinguished opposite directions of cerebrospinal fluid motion, and measurements at several locations showed that the timing of the motion differed between the ventricular system and surrounding spaces.[ref]
Normal flow patterns of intracranial and spinal cerebrospinal fluid defined with phase-contrast cine MR imaging by D. R. Enzmann and others. Abstract: participant groups,16 cardiac phases, directional encoding and regional timing.
For an illustrative one-second cycle, 16 equally spaced phases would separate samples by seconds. The paper's number of cardiac phases therefore matters: an average over the entire cycle could hide changes of direction within it. Conversely, sixteen phases are a temporal sampling scheme, not evidence of sixteen independent subjects. This example explains the measurement design without assigning an unreported individual contribution to either coauthor.
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