THE PHARMACOKINETICS OF HYPERPOLARIZED XENON - IMPLICATIONS FOR CEREBRAL MRI

In this work, a compartmental model to predict the concentration of hy perpolarized xenon (Xe) in the brain is developed based on the well es tablished kinetics of Xe and estimated T1 values for the compartments. For the gaseous compartments, T1 was sat to 12 seconds. Far the tissu e compartments, T1 was set to 6 seconds, Three gas delivery techniques were modeled: hyperventilation followed by breath-hold, continual bre athing, and hyperventilation followed by continual breathing. Based on Xe CT, it is estimated that the maximum concentration of Xe that coul d be breathed is 80%, Based on this value and the estimated maximum po larization of 50%, the peak gray matter concentration of hyperpolarize d Xe is calculated to be .036 mM. This leads to an estimated signal-to -noise ratio (SNR), at 2 T, for hyperpolarized Xe that is a factor of 50 lower than the SNR for proton MRI. The peak concentration of hyperp olarized Xe was also calculated over a wide range of gas and tissue T1 values, This model also predicts that the arterial blood will have a concentration of hyperpolarized Xe that is 10 times greater than the c oncentration in gray matter, An interactive version of the model can b e found on the World Wide Web at http://ric.uthscsa.edu/ staff/charles martinphd.html.