The use of magnetic resonance imaging to assess slow fluid flow in a model cerebrospinal fluid shunt system.

Cerebrospinal fluid (CSF) shunt malfunction in patients with hydrocephalus is common and can result in prolonged hospitalisation, operative exploration or progressive neurologic damage. The evaluation of shunt function usually requires invasive techniques that can be inaccurate or cause complications. Magnetic Resonance Imaging (MRI), which has been used to study both intraluminal blood flow and intraventricular CSF flow, may offer an alternative noninvasive test of shunt function. The MR characteristics of flow related enhancement were studied in a model shunt system. A special section of tubing for MRI was inserted into the system proximal to the valve. Flow through the system could be varied from 0 to 20 ml/h. Multiple spin echo images were made (TR2000, TE20) transverse to the specialised tubing. The intensity of the intraluminal MR signal at specific locations along this tubing and from a 'no flow' standard were measured. The signal intensity varied as a linear function of flow rate from 2.5 ml/h to 20 ml/h. These results suggest that MRI has potential for evaluating the slow flow in CSF shunts.