Intrathecal 99mTc‐DTPA imaging of molecular passage from lumbar cerebrospinal fluid to brain and periphery in humans

Abstract Introduction Cerebrospinal fluid (CSF) molecular exchange with brain interstitial fluid (ISF) and periphery is implicated in neurological disorders but needs better quantitative clinical assessment approaches. Methods Following intrathecal (ITH) dosing via lumbar puncture, Technetium‐99 m (99mTc‐) diethylenetriaminepentaacetic acid (DTPA) imaging was used to quantify neuraxial spread, CSF‐brain molecular exchange, and CSF‐peripheral clearance in 15 normal human volunteers. The effect of experimental convection manipulation on these processes was also assessed. Results Rostral cranial 99mTc‐DTPA exposures were influenced by the volume of artificial CSF in the formulation. Signal translocation to the cranial cisterns and the brain parenchyma was observable by 3 hours. 99mTc‐DTPA penetrated cortical ISF but showed lower signal in deeper structures. Urinary 99mTc‐DTPA signal elimination was accelerated by higher formulation volumes and mechanical convection. Discussion Widely used for detecting CSF leaks, ITH 99mTc‐DTPA imaging can also become a useful clinical biomarker for measuring molecular exchange physiology between the CSF, brain, and periphery.