[Influence of respiration and pulsatility on the accuracy of MR-phase contrast flow measurements: "in vitro" evaluation].
OBJECTIVE
Determination of the influence of pulsatility of blood flow and respiration-induced vascular motion on the accuracy of MR phase contrast flow measurements.


METHODS
Flow measurements in phantoms were performed with the phase contrast technique in a 1.5 Tesla MRI system using different flow volumes, varying degrees of flow pulsatility and a varying number of image phases. To determine the influence of respiratory motion on flow measurement accuracy, flow data was collected during motion of the whole phantom.


RESULTS
Flow measurements based on 6 and 16 image phases were significantly more accurate (p < 0.05) than those based on one phase. An increase in the degree of pulsatility resulted in a widening of the error range. Hence, increasing pulsatility demands an increase in the number of acquired phases to maintain sufficient measurement accuracy. Simulated respiratory motion with an excursion depth of only 5 mm resulted in a significant overestimation of true flow ranging between 22.9 and 42.1%. Measurements without simulated respiratory motion were more accurate (p < 0.001). An excursion depth of 15 mm led to a vast increase in the apparent vessel size in excess of 100%. Flow volume measurements increased accordingly to 1126 ml/min (true flow = 720 ml/min).


CONCLUSIONS
Accurate phase-contrast based flow measurements require an adjustment of acquisition parameters to correspond to the physiology of the vessel under consideration. Flow data in vessels subject to respiratory motion should only be collected in apnoea.
Schoenenberger
A W
AW
Departement Medizinische Radiologie, Universitätsspital, Zürich.
Debatin
J F
JF
D001783:Blood Flow Velocity; D003287:Contrast Media; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D012119:Respiration
D003287:Contrast Media