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Shunt flow measurement and evaluation of valve oscillation with a spin-echo phase-contrast MR sequence
A M Norbash1, N J Pelc, A Shimakawa
1Department of Radiology, Stanford University School of Medicine, CA 94305-5105.
Purpose:
To present a spin-echo phase-contrast (SEPC) magnetic resonance pulse sequence designed to measure the very slow flow in ventricular shunt tubing.
Materials And Methods:
A flow phantom constructed of shunt tubing and incorporating no valve or a high-, medium-, or low-pressure 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-section 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 R2s 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 between flow rate and the frequency of valve opening and closing.
Conclusion:
The SEPC technique is an accurate and noninvasive method of measuring shunt flow.