Monitoring of pO₂ by Spin-Spin Relaxation Rate 1/T₂ of ¹⁹F in a Rabbit Abscess Model

Abstract

The purpose of this study was to confirm the relationship of T₁ and T₂ relaxation rate vs. pO₂ in vivo of ¹⁹F MR signal measured from intracellular perflubron. Our work to date has demonstrated that 1/T₂ is more sensitive to pO₂ than 1/T₁ in the in vitro environment. The advantage of 1/T₂ vs. 1/T₁ is the speed of measurement and sensitivity.

Seven alternating T₁ and T₂ measurements were obtained during a continuous acquisition using the TTISS pulse sequence. An abscess model was used for the in vivo experiments where rabbits were infused with 5ml/kg Oxygent™ HT 10 days prior to scanning The abscess model was used because it has been shown that perflubron accumulates in macrophages located in the abscess wall. This technique thus provided signal from the intracellular milieu.

The results of this study proved that pO₂ monitoring by measuring T₂ of ¹⁹F is feasible and can be used in-lieu of the T₁ measurement. Given that the T₂ measurement is much more rapid than the T₁ measurement and that T₂ changes are more sensitive than T₁ changes with alterations in pO₂, T₂ should prove to be practical and useful for monitoring transient rapid changes in pO₂.