Perfusion imaging with a freely diffusible hyperpolarized contrast agent

Contrast agents that can diffuse freely into or within tissue have numerous attractive features for perfusion imaging. Here we present preliminary data illustrating the suitability of hyperpolarized ¹³C labeled 2‐methylpropan‐2‐ol (also known as dimethylethanol, tertiary butyl alcohol and tert‐butanol) as a freely diffusible contrast agent for magnetic resonance perfusion imaging. Dynamic ¹³C images acquired in rat brain with a balanced steady‐state free precession sequence following administration of hyperpolarized 2‐methylpropan‐2‐ol show that this agent can be imaged with 2–4s temporal resolution, 2 mm slice thickness, and 700 μm in‐plane resolution while retaining adequate signal‐to‐noise ratio. ¹³C relaxation measurements on 2‐methylpropan‐2‐ol in blood at 9.4T yield T₁ = 46 ± 4s and T₂ = 0.55 ± 0.03s. In the rat brain at 4.7T, analysis of the temporal dynamics of the balanced steady‐state free precession image intensity in tissue and venous blood indicate that 2‐methylpropan‐2‐ol has a T₂ of roughly 2–4s and a T₁ of 43 ± 24s. In addition, the images indicate that 2‐methylpropan‐2‐ol is freely diffusible in brain and hence has a long residence time in tissue; this in turn makes it possible to image the agent continuously for tens of seconds. These characteristics show that 2‐methylpropan‐2‐ol is a promising agent for robust and quantitative perfusion imaging in the brain and body. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.