Assessing arterial blood flow and vessel area variations using real-time zonal phase-contrast MRI.
OBJECTIVE
To measure peripheral artery function using a real-time phase-contrast (PC)-MRI sequence with tailored image-processing algorithms for flow computation.


METHODS
An approach to real-time flow measurements was developed based on two-dimensional spatially selective excitation pulses and consecutive tailored processing of the data to derive blood flow and vessel area variations. The data acquisition strategy allows for flow measurements at high spatial and temporal resolutions of 1 mm(2) and 50 msec, respectively. In postprocessing the vessel area is automatically extracted using correlation measures in conjunction with morphological image operators. By means of in vitro and in vivo validations, it is shown that the current methods provide accurate and reproducible measurements of flow and vessel area variations.


RESULTS
In vitro the comparison between the lumen area measured with the presented method and the values obtained by caliper gauge measurement showed a difference of 3.4% +/- 3.4% (mean +/- 2 SD). Similarly, the comparison between the stroke volumes determined with the presented method and by stopwatch and bucket measurements yielded a difference of 6.1% +/- 2.1%. In vivo the results from the real-time measurements for lumen area and stroke volume were compared with those from a gated PC-MRI technique with differences of 4.8% +/- 14% and 3.0% +/- 24.7%, respectively.


CONCLUSIONS
The presented method constitutes a reliable tool set for quantifying the variations of blood flow and lumen area in the superficial femoral artery during reactive hyperemia and for studying their correlation with cardiovascular risk factors.
Oelhafen
Markus
M
Institute for Biomedical Engineering, University of Zurich and Swiss Federal Institute of Technology Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland.
Schwitter
Juerg
J
Kozerke
Sebastian
S
Luechinger
Roger
R
Boesiger
Peter
P
D000465:Algorithms; D001783:Blood Flow Velocity / Q000502:physiology*; D005263:Femoral Artery / Q000502:physiology*; D006801:Humans; D006940:Hyperemia / Q000175:diagnosis; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015203:Reproducibility of Results