Perfusion Profiles in Patients with Chronic and Acute Internal Carotid Artery Occlusion

Background
It is important to identify patients with acute internal carotid artery occlusion (ICAO) from chronic ICAO, and there is still no easily applicable and consistent method for differentiation.
Aims
To determine whether the MR perfusion profile differs between acute and chronic ICAO, and to propose a diagnostic algorithm based on MR perfusion findings.
Methods
We included 38 chronic and 48 acute ICAO patients. Perfusion parameters were compared quantitatively and qualitatively between the two groups. Based on the qualitative ratings, a decision tree was built to differentiate acute from chronic ICAO.
Results
Chronic ICAO patients had smaller Tmax delay lesions than acute patients. A cutoff of >2ml of tissue with Tmax>10s had the highest sensitivity (0.979, 95% CI 0.875-0.998) and specificity (0.974, 95% CI=0.845-0.998) for identifying a chronic occlusion. The perfusion profile of chronic ICAO patients was characterized by symmetric mean transit time (MTT) (97.4%) and symmetric cerebral blood flow (CBF) (94.7%). While acute ICAO patients was characterized by Tmax delay (100%), prolonged MTT (97.9%), and decreased CBF (81.2%). When provided with a decision tree based on these profiles, independent raters could differentiate between acute and chronic ICAO with 96.5-98.8% accuracy and excellent inter-rater reliability (agreement coefficient=0.89, 95% CI 0.82-0.97).
Conclusions
Perfusion imaging shows promise for distinguishing acute from chronic ICAO with high accuracy. These results need to be validated in an external dataset.