Optimization of collateral grading on computer tomography angiography.

BACKGROUND: As compared to single-phase CTA (sCTA), multi-phase CTA (mCTA) has been shown to more accurately estimate collateral flow in acute ischemic stroke (AIS). We sought to determine the characterization of poor collaterals across the three different phases of the mCTA. We also attempted to establish the optimal arterio-venous contrast timing parameters on sCTA that would prevent false positive reads of poor collateral status. METHODS: We retrospectively screened consecutive patients admitted for possible thrombectomy from February 2018 to June 2019. Only cases with intracranial internal carotid artery (ICA) or main trunk of the middle cerebral artery (MCA) occlusion and both baseline mCTA and CT Perfusion available were included. Mean Hounsfield units (HU) of torcula and torcula/patent ICA ratio were used for the arterio-venous timing analysis. RESULTS: Of the 105 patients included, 35 (34%) received IV-tPA treatment and 65 (61.9%) underwent mechanical thrombectomy. A total of 20 patients (19%) had poor collaterals on the third-phase CTA (ground-truth). The first-phase CTA often underestimated collateral score (37/105 [35%], p < 0.01), however there were no significant differences across the second- and third-phases (5/105[5%], p = 0.06. Venous opacification Youden's J point for identifying suboptimal sCTAs was found to be 207.9HU in the torcula (65% sensitivity,65% specificity) and 66.74% for torcula/patent ICA ratio (51% sensitivity,73% specificity). CONCLUSION: A dual-phase CTA is significantly similar to a mCTA assessment of collateral score and may be applied at community-based centers. Absolute or relative thresholds for torcula opacification may be used to identify poor bolus-scan timing thus preventing erroneous assumptions of poor collaterals on sCTA.

ASPECTS is a predictor of favorable CT perfusion in acute ischemic stroke.

BACKGROUND AND PURPOSE: Computed tomography perfusion (CTP) is used by some stroke centers to stratify stroke patients who may potentially benefit from endovascular treatment. Our aim is to identify predictors of a favorable CTP in acute ischemic stroke patients evaluated within 8h from symptoms onset for possible endovascular treatment. MATERIALS AND METHODS: We reviewed records of patients who had CTP studies between August 2010 and September 2012. We included all patients with anterior circulation strokes with evidence of large vessel disease. All patients had CT head and CT angiography head and neck as part of our protocol. Favorable CTP was defined as core infarct size less than one third the middle cerebral artery distribution and penumbra>20% of infarct size. The patients were divided into two groups based on favorable CTP or not. Baseline characteristics, time parameters, laboratory data and radiological data were compared between both groups. For statistical analysis, we used independent and Fisher's exact tests and a multivariate logistic regression model. RESULTS: During this period, 60 patients met the inclusion criteria. Patients with favorable CTP were likely to be ≥ 80 years (33% vs 9%, P = 0.026), have Alberta Stroke Program early CT score (ASPECTS) > 7 (81% v. 21%, P ≤ 0.001) and lower mean time from symptom onset to CTP (234 ± 91 vs 305 ± 122, P = 0.015). On regression analysis, ASPECTS was the only independent predictor of a favorable CTP (OR = 16.2, CI: 4.3-62.2, P < 0.001). CONCLUSION: ASPECT score may be used as a tool to predict a favorable CTP. Larger studies are needed to confirm our findings.

Exploiting the keratin 17 gene promoter to visualize live cells in epithelial appendages of mice.

Keratin genes afford, given their large number (>50) and differential regulation, a unique opportunity to study the mechanisms underlying specification and differentiation in epithelia of higher metazoans. Moreover, the small size and regulation in cis of many keratin genes enable the use of their regulatory sequence to achieve targeted gene expression in mice. Here we show that 2 kilobases of 5' upstream region from the mouse keratin 17 gene (mK17) confers expression of green fluorescent protein (GFP) in major epithelial appendages of transgenic mice. Like that of mK17, onset of [mK17 5']-GFP reporter expression coincides with the appearance of ectoderm-derived epithelial appendages during embryonic development. In adult mice, [mK17 5']-GFP is appropriately regulated within hair, nail, glands, and oral papilla. Tracking of GFP fluorescence allows for the visualization of growth cycle-related changes in hair follicles, and the defects engendered by the hairless mutation, in live skin tissue. Deletion of an internal 48-bp interval, which encompasses a Gli-responsive element, from this promoter results in loss of GFP fluorescence in most appendages in vivo, suggesting that sonic hedgehog participates in K17 regulation. The compact mK17 gene promoter provides a novel tool for appendage-preferred gene expression and manipulation in transgenic mice.