Volumetric velocity measurements in restricted geometries using spiral sampling: a phantom study.
OBJECTIVE
The aim of this study was to evaluate the accuracy of maximum velocity measurements using volumetric phase-contrast imaging with spiral readouts in a stenotic flow phantom.


METHODS
In a phantom model, maximum velocity, flow, pressure gradient, and streamline visualizations were evaluated using volumetric phase-contrast magnetic resonance imaging (MRI) with velocity encoding in one (extending on current clinical practice) and three directions (for characterization of the flow field) using spiral readouts. Results of maximum velocity and pressure drop were compared to computational fluid dynamics (CFD) simulations, as well as corresponding low-echo-time (TE) Cartesian data. Flow was compared to 2D through-plane phase contrast (PC) upstream from the restriction.


RESULTS
Results obtained with 3D through-plane PC as well as 4D PC at shortest TE using a spiral readout showed excellent agreements with the maximum velocity values obtained with CFD (<1 % for both methods), while larger deviations were seen using Cartesian readouts (-2.3 and 13 %, respectively). Peak pressure drop calculations from 3D through-plane PC and 4D PC spiral sequences were respectively 14 and 13 % overestimated compared to CFD.


CONCLUSIONS
Identification of the maximum velocity location, as well as the accurate velocity quantification can be obtained in stenotic regions using short-TE spiral volumetric PC imaging.
Department of Medical Radiation Physics, Lund University, Lund, Sweden, anders.nilsson@med.lu.se.
Anders
A
Nilsson
Johan
J
Revstedt
Einar
E
Heiberg
Freddy
F
Ståhlberg
Karin Markenroth
KM
Bloch
D000465:Algorithms; D001157:Arterial Occlusive Diseases / Q000473:pathology / Q000503:physiopathology*; D001158:Arteries / Q000473:pathology / Q000503:physiopathology*; D001783:Blood Flow Velocity; D001810:Blood Volume; D001811:Blood Volume Determination / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D018401:Sample Size; D012680:Sensitivity and Specificity