= N. J. Pelc
{c}
\b[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.<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.]{ref}
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.<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.]{ref}
For an illustrative one-second cycle, 16 equally spaced phases would separate samples by $1/16=0.0625$ 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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