Impact of Multiphase Computed Tomography Angiography for Endovascular Treatment Decision-Making on Outcomes in Patients with Acute Ischemic Stroke

Cerebrovascular circulation; Ischemia; Ischemic strokeCirculació cerebrovascular; Isquèmia; Ictus isquèmicCirculación cerebrovascular; Isquemia; Ictus isquémicoBackground and Purpose Various imaging paradigms are used for endovascular treatment (EVT) decision-making and outcome estimation in acute ischemic stroke (AIS). We aim to compare how these imaging paradigms perform for EVT patient selection and outcome estimation. Methods Prospective multi-center cohort study of patients with AIS symptoms with multi-phase computed tomography angiography (mCTA) and computed tomography perfusion (CTP) baseline imaging. mCTA-based EVT-eligibility was defined as presence of large vessel occlusion (LVO) and moderate-to-good collaterals on mCTA. CTP-based eligibility was defined as presence of LVO, ischemic core (defined on relative cerebral blood flow, absolute cerebral blood flow, and cerebral blood volume maps) 1.8, absolute mismatch >15 mL. EVT-eligibility and adjusted rates of good outcome (modified Rankin Scale 0-2) based on these imaging paradigms were compared. Results Of 289/464 patients with LVO, 263 (91%) were EVT-eligible by mCTA-criteria versus 63 (22%), 19 (7%) and 103 (36%) by rCBF, aCBF, and CBV-CTP-criteria. CTP and mCTA-criteria were discordant in 40% to 53%. Estimated outcomes were best in patients who met both mCTA and CTP eligibility-criteria and were treated with EVT (62% to 87% good outcome). Patients eligible for EVT by mCTA-criteria and not by CTP-criteria receiving EVT achieved good outcome rates of 53% to 57%. Few patients met CTP-criteria and not mCTA-criteria for EVT. Conclusions Simpler imaging selection criteria that rely on little else than detection of the occluded blood vessel may be more sensitive and less specific, thus resulting in more patients being offered EVT and arguably benefiting from it.This study was supported by a grant from the Canadian Institute of Health Research. The authors are most grateful to all enrolling sites

Testing ASPECTS Reliability Using Color Coded Algorithm Enhanced Gray- White Matter Non Contrast CT

The Alberta Stroke Program Early CT Score (ASPECTS) is widely used to assess and diagnose Acute Ischemic Stroke Patients (AIS). Inter-rater reliability for ASPECTS however, is very poor even amongst physicians with extensive expertise. Much of this limitation has to do with the lack of agreement amongst physicians in identifying Early Ischemic Changes (EIC) on Non- Contrast Computed Tomography (NCCT) scans. This lack of agreement is due to the extremely subtle findings that the human eye is exposed to on gray scale NCCT scans during the acute period of ischemia. We therefore sought to use post processing algorithms to develop Color- Coded Algorithm Enhanced Gray- White Matter (AEGWM) NCCT scans. Increased differentiation between Gray- White matter on AEGWM NCCT scans was developed to act as a powerful imaging tool allowing for better delineation of EIC for AIS patients. In this thesis I investigated the utility of AEGWM NCCT scans for the purposes of detecting EIC in AIS patients. Overall, we found that AEGWM scans performed better as opposed to gray scale NCCT scans when using DWI as ground truth. In addition, inter rater agreement increased consistently across raters of all levels of expertise while using AEGWM scans. Although with some limitations, the use of AEGWM scans may be a promising research direction to pursue for future work

White Matter Structural Connectivity Is Not Correlated to Cortical Resting-State Functional Connectivity over the Healthy Adult Lifespan

Structural connectivity (SC) of white matter (WM) and functional connectivity (FC) of cortical regions undergo changes in normal aging. As WM tracts form the underlying anatomical architecture that connects regions within resting state networks (RSNs), it is intuitive to expect that SC and FC changes with age are correlated. Studies that investigated the relationship between SC and FC in normal aging are rare, and have mainly compared between groups of elderly and younger subjects. The objectives of this work were to investigate linear SC and FC changes across the healthy adult lifespan, and to define relationships between SC and FC measures within seven whole-brain large scale RSNs. Diffusion tensor imaging (DTI) and resting-state functional MRI (rs-fMRI) data were acquired from 177 healthy participants (male/female = 69/108; aged 18–87 years). Forty cortical regions across both hemispheres belonging to seven template-defined RSNs were considered. Mean diffusivity (MD), fractional anisotropy (FA), mean tract length, and number of streamlines derived from DTI data were used as SC measures, delineated using deterministic tractography, within each RSN. Pearson correlation coefficients of rs-fMRI-obtained BOLD signal time courses between cortical regions were used as FC measure. SC demonstrated significant age-related changes in all RSNs (decreased FA, mean tract length, number of streamlines; and increased MD), and significant FC decrease was observed in five out of seven networks. Among the networks that showed both significant age related changes in SC and FC, however, SC was not in general significantly correlated with FC, whether controlling for age or not. The lack of observed relationship between SC and FC suggests that measures derived from DTI data that are commonly used to infer the integrity of WM microstructure are not related to the corresponding changes in FC within RSNs. The possible temporal lag between SC and FC will need to be addressed in future longitudinal studies to better elucidate the links between SC and FC changes in normal aging