MONITORING OF PO(2) BY SPIN-SPIN RELAXATION RATE 1 T-2 OF F-19 IN A RABBIT ABSCESS MODEL/

The purpose of this study was to confirm the relationship of T1 and T2 relaxation rate vs. pO(2) in vivo of F-19 MR signal measured from int racellular perflubron. Our work to date has demonstrated that 1/T2 is more sensitive to pO(2) than 1/T1 in the in vitro environment. The adv antage of 1/T2 vs. 1/T1 is the speed of measurement and sensitivity. S even alternating T1 and T2 measurements were obtained during a continu ous acquisition using the TTISS pulse sequence. An abscess model was u sed for the in vivo experiments where rabbits were infused with 5 ml/k g Oxygent(R) HT 10 days prior to scanning, The abscess model was used because it has been shown that perflubron accumulates in macrophages l ocated in the abscess wall. This technique thus provided signal from t he intracellular milieu. The results of this study proved that pO(2) m onitoring by measuring T2 of 19F is feasible and can be used in-lieu o f the T1 measurement. Given that the T2 measurement is much more rapid than the T1 measurement and that T2 changes are more sensitive than T 1 changes with alterations in pO(2), T2 should prove to be practical a nd useful for monitoring transient rapid changes in pO(2).