CINE MAGNETIC-RESONANCE-IMAGING AND COLOR DOPPLER FLOW MAPPING DISPLAYS OF FLOW VELOCITY, SPATIAL ACCELERATION, AND JET FORMATION - A COMPARATIVE IN-VITRO STUDY

To study the effects of flow acceleration and high-velocity jets on th e display characteristics of cine magnetic resonance imaging compared with color Doppler flow mapping, a custom-designed in vitro flow model was developed. This model consisted of a funnel segment tapering to a n orifice (0.78 CM2) that leads into a confined receiving chamber with a second, discrete orifice (0.78 CM2) at its distal end. Cine magneti c resonance images obtained at varying flow rates (1.5 to 27.2 L/min) demonstrated loss of signal intensity throughout the tapering zone of spatial acceleration and a small zone of more marked signal loss immed iately proximal to the second orifice (always <50% of the signal inten sity within the tapering funnel zone) associated with more rapid spati al acceleration. A formed jet was imaged distal to the first orifice, and the turbulence area surrounding the laminar central jet core corre lated well with flow rate (r = 0.98), as did the distance from the ori fice to the subsequent onset of flow relaminarization (r = 0.96). A tu rbulent spray area was always seen distal to the second, discrete orif ice. Comparative observations with color Doppler flow mapping and cont inuous wave Doppler demonstrated that signal intensity on cine magneti c resonance imaging is reduced by both spatial acceleration, and the h igh-velocity and turbulent jets associated with obstructive and regurg itant lesions. In vitro evaluation of cine magnetic resonance imaging allows comparative observations to be made about the flow characterist ics of cine magnetic resonance imaging and color Doppler flow mapping and provides a more rational basis for the interpretation of cine magn etic resonance imaging in the clinical setting.