Anoxic Brain Injury Detection with the Normalized Diffusion to ASL Perfusion Ratio: Implications for Blood-Brain...

Anoxic brain injury is a result of prolonged hypoxia. We sought to describe the nonquantitative arterial spin-labeling perfusion imaging patterns of anoxic brain injury, characterize the relationship of arterial spin-labeling and DWI, and evaluate the normalized diffusion-to-perfusion ratio to differentiate patients with anoxic brain injury from healthy controls.

We identified all patients diagnosed with anoxic brain injuries from 2002 to 2019. Twelve ROIs were drawn on arterial spin-labeling with coordinate-matched ROIs identified on DWI. Linear regression analysis was performed to examine the relationship between arterial spin-labeling perfusion and diffusion signal. Normalized diffusion-to-perfusion maps were generated using a custom-built algorithm.

Thirty-five patients with anoxic brain injuries and 34 healthy controls were identified. Linear regression analysis demonstrated a significant positive correlation between arterial spin-labeling and DWI signal. By means of a combinatory cutoff of slope of >0 and R² of > 0.78, linear regression using arterial spin-labeling and DWI showed a sensitivity of 0.86 (95% CI, 0.71-0.94) and specificity of 0.82 (95% CI, 0.66-0.92) for anoxic brain injuries. A normalized diffusion-to-perfusion color map demonstrated heterogeneous ratios throughout the brain in healthy controls and homogeneous ratios in patients with anoxic brain injuries.

In anoxic brain injuries, a homogeneously positive correlation between qualitative perfusion and DWI signal was identified so that areas of increased diffusion signal showed increased ASL signal. By exploiting this relationship, the normalized diffusion-to-perfusion ratio color map may be a valuable imaging biomarker for diagnosing anoxic brain injury and potentially assessing BBB integrity.