Quantitative contrast-enhanced ultrasound measurement of cerebrospinal fluid flow for the diagnosis of ventricular shunt malfunction

Abstract

OBJECT Cerebral shunt malfunction is common but often difficult to effectively diagnose. Current methods are invasive, involve ionizing radiation, and can be costly. The authors of this study investigated the feasibility of quantitatively measuring CSF flow in a shunt catheter using contrast-enhanced ultrasound. METHODS A syringe pump was used to push a solution of gas-filled microbubbles at specific flow rates through a shunt catheter while a high-frequency ultrasound imaging system was used to collect ultrasound images for offline processing. Displacement maps and velocity profiles were generated using a speckle-tracking method based on a cross-correlation algorithm. An additional correction factor, to account for a predictable underestimation and to adjust the measured flow rates, was calculated based on the geometry of the ultrasound imaging plane and assuming a simple model of laminar flow. RESULTS The developed method was able to differentiate between physiologically relevant flow rates, including no flow and 0.006 to 0.09 ml/min, with reasonable certainty. The quantitative measurement of flow rates through the catheter using this method was determined to be in good agreement with the expected flow rate. CONCLUSIONS This study demonstrated that contrast-enhanced ultrasound has the potential to be used as a minimally invasive and cost-effective alternative method for outpatient shunt malfunction diagnosis.