This is a prospective, longitudinal study of MR imaging of intrathecally delivered gadolinium contrast (Magnevist, Gd-DTPA) in healthy adult male and female subjects. Subjects will be divided into two groups (20-50 years old and 51-80 years old) both of which will receive intrathecal injection of the drug Magnevist (Gd-DTPA), followed by serial MR imaging over the course of 10-12 hours. The purpose of the study is determine the transport kinetics of Central Nervous System (CNS) exposure to gadolinium contrast injected into the lumbar intrathecal space (lower back) and evaluate changes with age. This will allow investigators to evaluate the brain parenchymal penetration of gadolinium as an illustrative imaging marker that mirrors the glymphatic system. Investigators hypothesize the exposure and penetration patterns of the neuraxis to neurotherapeutic drugs can be modeled using gadolinium intrathecal contrast administered in the lumbar intrathecal space.