Mean transit time on Aquilion ONE and its utilization in patients undergoing acute stroke intervention

Abstract

Background—Neuroimaging techniques have been beneficial in identifying patients with salvageable
penumbra. We sought to validate the mean transit time (MTT) map on computed tomography perfusion
(CTP) imaging utilizing an Aquilion ONE computed tomography (CT) scanner running a singular value
decomposition plus algorithm in patients with acute large vessel ischemic stroke who underwent endovascular therapy.
Methods—We conducted a retrospective analysis of consecutive patients presenting to the emergency
room who met the following criteria: 1) had a large vessel acute ischemic stroke; 2) had a high-quality
whole-brain CTP; 3) treated with endovascular therapy; and 4) received a follow-up MRI with diffusionweighted imaging (DWI) within 48 h. A blinded neurologist, neuroradiologist, and neurosurgeon utilized
the Vitrea software to process the images independently using an infarct perimeter method.
Results—Twelve patients met the inclusion criteria. A comparison was made between the volumes of
infarct core (IC) utilizing MTT and DWI after accounting for other co-founding factors (i.e., recanalization
rate, time between CT and MRI, time to achieve recanalization, and IV t-PA administration). MTT was
redefined as capillary MTT (cMTT) which represented evolving capillary flow influenced by hypoxia
induced vasodilation/vasoconstriction. We divided the patients into two groups based on the degree of
reperfusion: A) patients with a TICI score of IIb or III and B) patients with a TICI score of I or IIa. We
compared the two groups and found that the rate of reperfusion significantly affected the volume of the
infarct on MTT when compared with a follow-up MRI (p value < 0.04). Furthermore, we found a strong
positive correlation R
2
= 0.6 between the average MTT infarct volume and the final DWI MR volumes. In
addition, the averaged MTT IC volumes were 84% of the final averaged DWI IC volumes.
Conclusion—Although further studies are required to validate this retrospective study, preliminary data
suggest that cMTT maps can be a valuable and accurate tool in the assessment of patients with acute stroke
who may benefit from aggressive endovascular therapy.