In vitro evaluation of CSF shunt function by radionuclides

An in vitro study of clearance of a radiolabeled marker was conducted on nine commonly used shunting devices. Clearance of 0.5 ml of113mIn-diethylenetriamine-pentaacetic acid (DTPA) injected into the chamber, by water infused through the system at constant rate (0.034–0.46 ml/min), was measured by monitoring activity over the chamber and accumulating counts at 5-s intervals on a multichannel analyzer. Each flow rate was triplicated, and a graph of log value of counts versus time made. A mean t1/2 was computed for each flow rate and a new graph constructed. A best-fit curve constructed for the graph of each shunt system allows determination of flow rate for a known half time of isotope clearance.