SHUNT FLOW MEASUREMENT AND EVALUATION OF VALVE OSCILLATION WITH A SPIN-ECHO PHASE-CONTRAST MR SEQUENCE

PURPOSE: To present a spin-echo phase-contrast (SEPC) magnetic resonan ce pulse sequence designed to measure the very slow flow in ventricula r shunt tubing. MATERIALS AND METHODS: A flow phantom constructed of s hunt tubing and incorporating no valve or a high-, medium-, or low-pre ssure valve was connected to a flow pump. Flow rates were 0.05-1.00 mL /min (72-1,440 mL/d). Flow measurement was performed with the thin-sec tion SEPC sequence. RESULTS: The flow rates measured with SEPC imaging correlated closely with the pump flow rate for the entire physiologic spectrum of shunt flow rates. This was true for all valves, resulting in overall R(2)s of .974 at 4 cm/sec and .980 at 2 cm/sec. Shunt flow was pulsatile with valves in place. There was a linear relationship b etween flow rate and the frequency of valve opening and closing. CONCL USION: The SEPC technique is an accurate and noninvasive method of mea suring shunt flow.