MULTIPHASE SEGMENTED K-SPACE VELOCITY MAPPING IN PULSATILE FLOW WAVE-FORMS

The aim of the present study was to obtain the precision of flow measu rement in breath-hold segmented k-space flow sequences. The results ar e based on studies of pulsatile how in a phantom tube, The ultimate pu rpose is to use these sequences to measure coronary flow. In abdominal and cardiothoracic magnetic resonance imaging the image quality is de graded due to respiratory motion, In the segmented k-space acquisition method, one obtains many phase-encoding steps or views per cardiac ph ase. This shortens imaging time in the order of phase-encoding lines a nd makes it possible to image in a single breath-hold, thereby elimina ting respiratory artefacts and improving edge detection. With breath-h old multiframe cine flow images it is possible to evaluate flow in all abdominal and cardiothoracic areas, including the coronary arteries. Our study shows that velocity curves shift in time when the number of k-space k(y)-lines per segment (LPS) are varied; this shift is linear as a function of LPS. The mean velocity V-mean in the center of mass o f the pulsatile peak is constant (V-mean = 40.1 +/- 2.9 cm/s) and time t = -10.1 x LPS + 268 (r = 0.993, p < 0.0001). Correlation between th eoretical and experimental flow curves is also linear as a function of LPS: C = -0.977 LPS (r = 0.987, p < 0.0001). It is concluded that v elocity curves move with LPS and are smoothed when the breath-hold vel ocity mapping is used. The more LPS is gathered the more inaccurate re sults are. LPS 7 or more cannot be considered clinically relevant. (C) 1998 Elsevier Science Inc.