Multiphase CTA Research Articles

Optimal Imaging at the Primary Stroke Center.

Optimal Imaging at the Primary Stroke Center.

Abstract 77: Ongoing Leakage Revealed by Second Phase Spot Sign Volume Expansion in Multi-Phase Computed Tomography Angiography Strongly Predicts Intracranial Hemorrhage Growth

Background: CTA spot sign is a predictor of intracerebral hemorrhage (ICH) expansion. This sign can fluctuate in appearance, volume, and timing. Multiphase CTA (mCTA) can identify spot sign through 3 time-resolved images. We sought to identify a novel predictor of follow up total hematoma expansion using mCTA. Methods: This cohort study included patients with ICH between 2012-2019. Quantomo software was used to measure total hematoma volume (ml) from baseline CT & follow-up CT/MRI blinded to spot sign in 3 mCTA phases. Spot sign expansion was calculated by subtracting 1 st phase spot sign volume from 2 nd phase spot sign volume measured in microliters. Results: 199 patients [63% male, mean age 69 years, median NIHSS 11, IQR 6-20] were included. Median baseline ICH volume was 16.1 ml (IQR 5-29.9 ml). Amongst all three mCTA phases, spot sign was best detected on the 2nd phase (23% vs 17.5% 1 st phase vs 22% 3 rd phase). In multivariable regression, spot sign expansion was significantly associated with follow up total hematoma expansion (OR: 1.03 per microliter of spot sign expansion, p=0.01). Figure 1 shows the predicted total hematoma expansion by spot sign expansion. mCTA spot sign had a higher sensitivity for predicting total hematoma volume expansion than single-phase CTA (reported in meta-analysis of 14 studies), 86% vs 53%, respectively, while both having similar specificity, 87% vs 88%, respectively. Conclusion: Spot sign expansion on mCTA is a novel predictor of total hematoma expansion and could be used to select patients for immediate therapeutic intervention in future clinical trials. Using mCTA improves sensitivity while preserving specificity over single-phase CTA.

Displaying Multiphase CT Angiography Using a Time-Variant Color Map: Practical Considerations and Potential Applications in Patients with Acute Stroke.

Various imaging protocols exist for the identification of vessel occlusion and assessment of collateral flow in acute stroke. CT perfusion is particularly popular because the color maps are a striking visual indicator of pathology. Multiphase CTA has similar diagnostic and prognostic ability but requires more expertise to interpret. This article presents a new multiphase CTA display format that incorporates vascular information from all phases of the multiphase CTA series in a single time-variant color map, thereby facilitating multiphase CTA interpretation, particularly for less experienced readers. Exemplary cases of multiphase CTA from this new display format are compared with conventional multiphase CTA, CT perfusion, and follow-up imaging to demonstrate how time-variant multiphase CTA color maps facilitate assessment of collateral flow, detection of distal and multiple intracranial occlusions, differentiation of pseudo-occlusion from real occlusion, and assessment of flow relevance of stenoses, ante- and retrograde flow patterns, and clot permeability.

Clinical prognosis analysis of collateral circulation and vascular recanalization in patients with acute ischemic stroke based on multiphase CTA

Objective To evaluate the relationship between the status of collateral circulation provided by multiphase CT angiography and the benefit and risk of vascular recanalization in patients with middle cerebral artery (MCA) occlusion. Methods This retrospective study included 49 patients diagnosed with acute MCA occlusion and treated with rt-PA in the First Affiliated Hospital of Nanjing Medical University from October 2017 to September 2018. According to the ASPECTS collateral circulation score, the patients were divided into two groups: good collateral group (n=31) and poor collateral group (n=18). The benefits and risks after thrombolysis in the two groups were compared, including 24-h NIHSS score, 30-day mortality, 90-day modified rankin scale (mRS) score, and the incidence of symptomatic cerebral hemorrhage. Statistical analysis was performed using t test, corrected χ2 test, or Fisher's exact test. Results The 24-h NIHSS score and 90-day mRS score in the good collateral group were significantly lower than those in the poor collateral group (4.6±5.6 vs 12.5±8.4, P=0.00; 1.7±1.7 vs 3.1±1.5, P 0.05), but the 30-day mortality of the poor collateral group was still greater than that of the good collateral group (11.1% vs 0%). Conclusion For patients with acute MCA infarction and receiving vascular recanalization therapy, patients with good collateral circulation can achieve good clinical outcomes, restore better recent neurological function, and obtain lower incidence of symptomatic cerebral hemorrhage and lower disability and mortality rate. Key words: Retrospective studies; Acute ischemic stroke; Intravenous thrombolysis; Multiphase CT angiography; Collateral circulation

Collateral Scores in Acute Ischemic Stroke : Aretrospective study assessing the suitability of collateral scores as standalone predictors of clinical outcome.

Several collateral scores have been published for stroke in the middle cerebral artery territory, each considering different aspects of cerebral collateralization. Currently, there is no gold standard in CT-based collateral assessment. The aim of this retrospective study was to compare five collateral scores and determine whether they are able to predict clinical outcome after thrombectomy as standalone parameters. Inclusion criteria were M1occlusion, premorbid modified Rankin scale (mRS) of0-3, treatment with endovascular thrombectomy and groin puncture within 12 h after stroke onset. The Maas etal., Miteff etal., Tan etal., ASITN/SIR and mCTA collateral scores were retrospectively assessed in multiphase CTA images and correlated with 90-day mRS (90d-mRS) scores. Good outcome was defined as 90d-mRS0-2 or unchanged to premorbid mRS. In total, 108 patients were included of which 39.8% achieved agood outcome. The area under the curve (AUC) values of receiver operating characteristic (ROC) curve analysis for Maas etal., Miteff etal., Tan etal., ASITN/SIR and mCTA scores were 0.60 (0.51-0.70), 0.60 (0.52-0.68), 0.61 (0.51-0.70), 0.59 (0.49-0.70) and 0.61 (0.50-0.71), respectively. The correlation between 90d-mRS and Maas (r = -0.16, P = 0.091), Miteff (r = -0.25, P = 0.009), Tan (r = -0.26, P = 0.007), ASITN/SIR (r = -0.21, P = 0.030) and mCTA (r = -0.22, P = 0.021) scores was poor. Although collaterals are known to correlate with clinical outcome, none of the analyzed collateral scores sufficiently predicted outcome as astandalone parameter.

Correction to: Accuracy and Reliability of Multiphase CTA Perfusion for Identifying Ischemic Core.

Correction to: Clin Neuroradiol 2018 https://doi.org/10.1007/s00062-018-0717-x Unfortunately, the author list of the original version of this article contains amistake. The middle name of the author "Rani Gupta Sah" was erroneously tagged as part of the surname in the article's metadata.This mistake.

Comparison of CT angiography collaterals for predicting target perfusion profile and clinical outcome in patients with acute ischemic stroke

To compare collateral status on single-phase CT angiography (sCTA) and multiphase CT angiography (mCTA) and their ability to predict a target mismatch on CT perfusion (CTP) and clinical outcome in patients with acute ischemic stroke (AIS). Seventy-three AIS patients with stroke onset between 5 and 15h or with unclear onset time and occlusions in the M1/M2 segment of the middle cerebral artery and/or intracranial internal carotid artery underwent head non-contrast CT and CTP. Simulated sCTA and mCTA were reconstructed from CTP data and were compared for collaterals assessment. The ability to predict target mismatch on CTP (an ischemic core < 70ml, a mismatch ratio ≥ 1.8, and an absolute difference ≥ 15ml) and 90-day modified Rankin Scale (mRS) score of 0-2 was compared between sCTA and mCTA by using receiver operating curve analysis. sCTA underestimated the collateral status when compared with mCTA (p < 0.01). The ability of mCTA to predict target mismatch (AUC = 0.902, 95% confidence interval [CI] 0.809, 0.959) and clinical outcome (AUC = 0.771; 95% CI, 0.655, 0.864) was better than that of sCTA (p < 0.05 overall). A mCTA collateral score of > 3 best identified the target mismatch (sensitivity, 78.4%; specificity, 90.9%) and predicted 90-day mRS score of 0-2 (sensitivity, 84.8%; specificity, 69.4%). The collaterals were better estimated by mCTA compared with sCTA. A mCTA collateral score of > 3 optimized the prediction of a target mismatch on CTP and a good clinical outcome in patients with AIS. • Collateral circulation is a key determinant of ischemic core and penumbra. Better collaterals are associated with smaller ischemic core volumes and larger mismatch ratios on CT perfusion. • The collaterals can be better estimated by multiphase CTA compared with single-phase CTA. • A collateral score of > 3 on multiphase CTA best identifies patients with target mismatch on CT perfusion and predicts 90-day mRS score of 0-2.

Abstract TP77: Collateral- vs Perfusion-Based Selection Paradigm of Late Window (6-24 hours) Patients With Acute Ischemic Stroke a Comparative Study of Decision Making Using Multi-Phase CTA and CT Perfusion

Purpose: To compare the performance of collateral- vs perfusion-based imaging paradigms in late window stroke patients. Methods: In the prospective international (PRove-IT) study, patients had baseline CT head, multi-phase CTA (mCTA) and CTP. Patients presenting 6-24 hours of onset were included. We retrospectively selected patients for EVT based on 1) Collaterals: ASPECTS ≥5, plus proximal intracranial occlusion, plus good mCTA collaterals; 2) Perfusion: using DEFUSE-3, or DAWN trial criteria. CTP was processed using RAPID software. The performance of each paradigm to predict outcomes was assessed using the area under the receiver operating characteristic curve (AUC) of logistic regression models adjusting for age, NIHSS, sex, onset to CT time, EVT treatment, and interaction of EVT and the imaging paradigm. Results: We included 83 patients; medians of age 71, NIHSS 12, ASPECTS 9, and onset/ last seen well to CT of 576 minutes. Occlusions were: ICA, M1, M2-MCA (81.9 %), distal (8.4%) and none (9.6%). 35 patients received EVT (all without IV tPA), 10 IV tPA, and 38 treated conservatively. TICI 2b-3 was achieved in 71.4% of EVT patients. mRS≤2 at 90 days was achieved in 47% (51.4% with EVT: 72% of TICI2b/3 patients). Table 1 shows 90-day mRS according to the imaging paradigm for the entire cohort. Among 10 patients who were EVT-eligible according to mCTA but not DEFUSE-3, 70% achieved mRS≤2. Among 31 who were EVT-eligible per mCTA but not DAWN, 61% achieved mRS≤2. For 5 patients who were EVT-eligible per DEFUSE-3 but not mCTA, 60% achieved mRS≤2. No patients were EVT-eligible per DAWN but not per mCTA. All paradigms had comparable AUCs for 90-day mRS≤2. In the EVT subgroup, mCTA had AUC of 0.80 vs 0.79 for DAWN, and 0.78 in DEFUSE-3 paradigms. Conclusion: The mCTA-defined collateral paradigm performs similarly well for EVT selection in the late time window. It also may include additional patients with possible benefit from ECT who would have been excluded by CTP-based imaging selection.

Abstract WP66: CT and Multiphase CTA Alone Can Identify Thrombectomy Candidates Beyond 6 Hours

Introduction: Current stroke guidelines recommend CT Perfusion (CTP) or MRI to identify thrombectomy candidates beyond 6 hours from stroke onset. The efficacy of more readily available NCCT and CTA in the identification of such patients is unknown. In this study, we compared the accuracy of arterial phase CTA only (sCTA) and multi-phase CTA (mCTA) with MRI in patients beyond 6 hours from onset. Methods: We retrospectively reviewed 45 consecutive patients, presenting 6 to 24 hours from stroke onset, with known ICA or M1 occlusions. All patients had pre-treatment CTA and MRI, with diffusion weighted (DWI) and perfusion weighted imaging (PWI). MRI images were processed using RAPID. Five experienced readers independently scored ASPECTS (0-10), sCTA collateral score (0-5), and whether patients would have met DAWN or DEFUSE-3 MRI imaging criteria. After a one-month delay, grading was repeated by the same readers using NCCT and mCTA. The sensitivity and specificity for DAWN and DEFUSE-3 eligibility was examined for both sCTA and mCTA. We also examined the median DWI volume based on the combination of NCCT ASPECTS and collateral score, for both sCTA and mCTA. Results: Sensitivity and specificity for DAWN eligibility was 91.4% and 74.8% for sCTA; 87.2% and 76.8% for mCTA. For DEFUSE-3, sensitivity and specificity was 92.3% and 46.3% for sCTA; 94.5% and 57.5% for mCTA. The higher specificity for DAWN is likely due to the more restrictive imaging criteria used in that trial. For DWI volume, the results are summarized in the graph, and show that the combination of mCTA collateral score and NCCT ASPECTS is significantly more correlated with DWI volume than sCTA (p=.0018). Conclusions: In conclusion, the combination of NCCT ASPECTS and mCTA collateral score has high sensitivity and moderate specificity for identifying patients who meet DAWN or DEFUSE-3 criteria. NCCT ASPECTS and Multi-phase CTA collateral score are significantly more correlated with DWI volume than single-phase.

Abstract WMP15: Flat Panel Detector CT Assessment in Stroke to Reduce Times to Intra-Arterial Treatment (FAST-IA): A Study of Multi-Phase CTA in the Angiography Suite to Bypass Conventional Imaging

Background: Bypassing the emergency department (ED) and the CT suite by directly transporting to the neuroangiography suite for imaging assessment and treatment may shorten reperfusion times while maintaining proper patient selection. Methods: Single-center prospective study of consecutive patients with anterior circulation LVO strokes transferred to our facility for consideration of endovascular therapy (ET) from 5/2016 to 12/2017. Those with basilar strokes and/or presenting to the ED were excluded. Patients were categorized into two groups: (1) F lat-Panel Detector CT A ssessment in S troke to Reduce T imes to I ntra- A rterial Treatment (FAST-IA) group, with patients transferred directly to the suite for Flat-Panel Detector multiphase CT angiography (FD-mCTA); and (2) Patients undergoing standard protocol including CT+/-CTA/CTP. The groups were matched for age, baseline NIHSS and pre-treatment glucose. Baseline characteristics, time metrics and outcomes were compared. Results: Out of 419 patients that underwent ET over the study period, 210 patients fit inclusion criteria, with 54 (25.7%) in the FAST-IA group. After matching, 49 FAST-IA/Control pairs were generated and analyzed. Baseline characteristics were well-balanced. FAST-IA patients had significantly shorter median door-to-puncture (33[26.5-47] vs 55[44.5-66] minutes, p&lt;0.001), door-to-reperfusion (85[57.5-115.5]vs110[80-153],p=0.005) and picture-to-puncture (18[13.5-22.5]vs 42[32-47.5]minutes, p&lt;0.001)times. There were no differences in rates of successful reperfusion (mTICI 2b-3, 95.9% vs 100%, p=0.5), parenchymal hematomas type-2 (4.1% vs 2%, p=1.00), good outcome (90-day mRS-0-2, 44.9% vs 40.8%, p=0.68) and 90-day mortality (14.3% vs 22.4%,p=0.30). Conclusions: Directly transferring patients to angiography and using FD-mCTA to determine eligibility for ET is safe and results in significant reduction in treatment times. Future larger studies are warranted.

Acute Occlusion of the Distal Internal Carotid Artery : Single Center Experience in 46Consecutive Cases, review of the literature and proposal of aclassification.

The acute distal intracranial occlusion of the internal carotid artery (ICA) is a very complex heterogeneous pathology, characterized by various patterns. Aim of this work is to identify the different types and propose a classification. Among the patients admitted for stroke in the anterior circulation from august 2014 to October 2017, 46 (25%) presented with intracranial distal carotid artery occlusion. The mean age of the patients was 71 (SD 13.7), 65,2% female. The protocol included general and specific neurological examinations, CT, CT-Angiography with multiphase CTA, followed by Angiography. The occlusion was treated by aspiration device alone or associated with stent-retriever. NIHSS at the admission, at discharge and modified ranking Scale (mRS) at four months were examined. The occlusions presented with various patterns. Depending on its site (located at the distal ICA bifurcation or more proximal at the level of the ophthalmic segment of ICA, with or without extent to ICA bifurcation) taking also into account the various involvement of the cerebral vessels and anatomic variations of Circle of Willis, three groups of occlusion types could be identified (T1, T2 and T3). The collateral circulation, and the possibilities of the endovascular revascularization important for the final outcome, were clearly connected with the type of occlusion. NIHSS at admission was 19.1 (Range from 8 to 30, SD 4.4). Good outcome defined as mRS 0-2 at for months was obtained in 17 patients (37%). The proposed classification reproduces more precisely the complexity and heterogeneity of this pathology, being useful in the diagnosis and treatment of these patients.

Validation of collateral scoring on flat-detector multiphase CT angiography in patients with acute ischemic stroke.

BackgroundThe pivotal impact of collateral circulation on outcomes in endovascular therapy has fueled the development of numerous CTA collateral scales, yet synchronized validation with conventional angiography has never occurred. We validated multiphase flat-detector CTA (mpFDCTA) for collateral imaging in patients undergoing endovascular stroke treatment.Materials and methodsConsecutive acute ischemic stroke patient data, including mpFDCTA shortly followed by digital subtraction angiography (DSA), in the setting of acute ICA- or MCA-occlusions were analyzed. An independent core lab scored mpFDCTA with an established collateral scale and separately graded American Society of Interventional and Therapeutic Neuroradiology (ASITN) collateral score on DSA, blind to all other data.Results24 consecutive cases (age 76.7 ± 7.3 years; 58.3% women; baseline NIHSS median 17 (4–23)) of acute ICA- or MCA-occlusion were analyzed. Time from mpFDCTA to intracranial DSA was 23.04 ± 7.6 minutes. Median mpFDCTA collateral score was 3 (0–5) and median DSA ASITN collateral score was 2 (0–3), including the full range of potential collateral grades. mpFDCTA and ASITN collateral score were strongly correlated (r = 0.86, p<0.001). mpFDCTA provided more complete collateral data compared to selective DSA injections in cases of ICA-occlusion. ROC analyses for prediction of clinical outcomes revealed an AUC of 0.76 for mpFDCTA- and 0.70 for DSA ASITN collaterals.ConclusionsmpFDCTA in the angiography suite provides a validated measure of collaterals, offering distinct advantages over conventional angiography. Direct patient transfer to the angiography suite and mpFDCTA collateral grading provides a novel and reliable triage paradigm for acute ischemic stroke.

Accuracy and Reliability of Multiphase CTA Perfusion for Identifying Ischemic Core.

Acute stroke treatment requires simple, quick and accurate detection of early ischemic changes to facilitate treatment decisions guided by published selection criteria. The aim of this study was to determine the accuracy and reliability of multiphase computed tomography angiography (mCTA) perfusion hypoattenuation for detecting early severe ischemia. Non-contrast CT (NCCT), mCTA for regional leptomeningeal score (mCTA-rLMC), and mCTA perfusion lesion visibility (mCTA-arterial and mCTA-venous) were assessed blinded to clinical information in patients treated with endovascular therapy (EVT). The extent of early ischemia defined by regions of hypoattenuation was evaluated by the Alberta Stroke Program Early CT Score (ASPECTS). The ASPECTS scores were dichotomized based on the American Heart Association (AHA) guidelines for EVT selection, ASPECTS ≥6 vs. <6. The diagnostic accuracy was calculated by comparison to 24-h magnetic resonance imaging (MRI) or CT ASPECTS. Inter-observer reliability of NCCT and mCTA ASPECTS was evaluated. Machine learning models were used to predict the clinical follow-up outcome, e.g. National Institutes of Health Stroke scale (NIHSS) and modified Rankin scale (mRS) from baseline imaging data and patient information. A total of 89acute stroke patients (68 ± 15years of age) were analyzed (33TICI-0, 56TICI-2b or 3). Median baseline NIHSS was 17. The mCTA-venous had alarge effect on accurately identifying early ischemia when dichotomized for ASPECTS ≥6 vs <6 (likelihood ratio [LR+] > 10 vs. [LR-] < 0.29) compared to the moderate effect of NCCT ([LR+] = 6.7; [LR-] = 0.56) and mCTA-rLMC [(LR+ = 8.0; (LR-) = 0.83)]. The inter-observer reliability in mCTA-venous was almost perfect for all ASPECTS regions except the internal capsule. The machine learning support factor regression model identified mCTA-venous as the most important imaging covariate for predicting 24-h NIHSS and 90-day mRS. The assessment of mCTA-venous permits amore accurate detection of early ischemia than NCCT and mCTA-rLMC score and is predictive of clinical outcome. We would recommend the inclusion of mCTA perfusion lesion in future endovascular trials aiming at extending current AHA guidelines for EVT in stroke patients with low ASPECTS.

Abstract WP55: Low Predictive Value of Multiphase CT Angiography for CT Perfusion Defined Ischemic Penumbra

Introduction: Multiphase CT angiography (mCTA) has been proposed as an alternative to CT Perfusion (CTP) for identification of acute stroke patients with the potential for salvage after reperfusion therapy. We tested the hypothesis that poor collateral patterns on mCTA are predictive of large CTP defined ischemic cores. Methods: Multiphase CTA was generated from CTP source images (peak arterial, +8 and +16 s). Two expert raters assessed the collateral pattern on mCTA (absent/moderate/good). An Alberta Stroke Program Early CT (ASPECT) score was also assessed on the first and last phase of the mCTA as well as the non-contrast CT (NCCT). Hypoperfused regions were defined as those without vessel enhancement on the first phase. Core regions were defined as those without vessel enhancement on the final phase and/or NCCT changes. An ASPECTS mismatch score was calculated as a penumbral estimate. Penumbral tissue on CTP was defined as regions with a Delay Time (DT) &gt;3 seconds, and ischemic core was defined as a combination of DT&gt;3 seconds and relative CBF&lt;40% of the contralateral hemisphere. Results: Of 141 patients, 79(56%) had penumbral patterns on CTP. Of these, 71(90%) had moderate/good collaterals. The mean penumbral volume in all patients was 20.8±26.6 ml and that in patients with large vessel occlusions (LVO; n=40) was 44.0±30.5 ml. At an ASPECTS mismatch score threshold of 2, mCTA predicted CTP defined penumbral patterns with a sensitivity of 77% and specificity of only 10%. The positive and negative predictive values were 57.7% and 61.5% respectively. In large vessel occlusion patients, mCTA predicted penumbra with 95.8% sensitivity and 43.8% specificity. The positive predictive value for penumbral patterns was 71.7%, and the negative predictive value was 87.5%. Eight patients were found to have a large core (&gt;70 ml) on CTP, 3 of whom had moderate/good collaterals and 2 of whom also had a NCCT ASPECTS&gt;5. Four large core patients had a mCTA penumbral score ≥ 2. Discussion: mCTA predicts penumbra with relatively high sensitivity, particularly in LVO patients. In some patients, however, mCTA can incorrectly classify penumbral patterns despite the presence of large cores on CTP. In non-LVO patients, mCTA is neither sensitive, nor specific for penumbral patterns.

Abstract WP51: Currency of Collaterals: Validation and Clinical Utility of a Novel Imaging Paradigm for Triage to Endovascular Therapy

Background: The pivotal impact of collateral circulation on outcomes in endovascular therapy has fueled the development of numerous single and multiphase CTA collateral scales, yet synchronized validation with conventional angiography has never occurred. Multiphase flat detector CT angiography (mpFDCTA) enables direct patient transfer to the angiography suite and rapid collateral triage. We validated this novel collateral imaging paradigm and potential clinical utility for endovascular stroke treatment. Methods: Consecutive acute ischemic stroke patient data, including mpFDCTA followed within few minutes by digital subtraction angiography (DSA), in the setting of ICA or proximal MCA occlusions were analyzed. An independent core lab scored mpFDCTA with an established multiphase CTA collateral scale and separately graded ASITN collateral status on DSA, blind to all other data. Results: 24 consecutive cases (age 76.7 ± 7.3 years; 58.3% women; baseline NIHSS median 17 (4-23)) of acute stroke due to ICA or proximal MCA occlusion were analyzed with simultaneous mpFDCTA and DSA. Arterial occlusion sites included 18 M1 MCA, 5 ICA, 1 M2 MCA. ASPECTS was median 8 (4-10). Time from first noncontrast FDCT to intracranial DSA was 23.04 ± 7.6 minutes with mTICI ≥ 2b reperfusion in 91.7% of cases. mpFDCTA collateral score was median 3 (0-5) and DSA ASITN was median 2 (0-3), including the full range of potential collateral grades. mpFDCTA and ASITN were highly correlated (r=0.86, p&lt;0.001). mpFDCTA provided more complete collateral data compared to selective DSA injections in cases of ICAO. ROC analyses for prediction of clinical outcomes revealed an AUC of 0.76 for mpFDCTA collaterals and 0.70 for DSA ASITN collateral grades. Conclusions: Multiphase flat detector CT angiography (mpFDCTA) in the angiography suite provides a validated measure of collaterals, offering distinct advantages over conventional angiography. Direct patient transfer to the angiography suite and mpFDCTA collateral grading provides a novel and reliable triage paradigm for acute ischemic stroke.

Split-bolus single scan CTA for evaluation of mesenteric ischemia.

To evaluate split-bolus single scan CTA protocol for evaluation of acute mesenteric ischemia. In this HIPAA-compliant IRB-approved study, consecutive patients evaluated for mesenteric ischemia between 11/2015 and 10/2016 were included. Patients scanned prior to 4/2016 were scanned with multiphasic CTA protocol and after with split-bolus single scan CTA. Objective and subjective evaluation was performed by three board-certified readers. Findings were correlated to composite clinical reference outcome. Eighty patients were included: 40 with split-bolus and 40 with multiphasic CTA protocol with similar age (60.3±16.2years vs. 64.7±17.0years, p=0.19) and BMI (28.0±6.7 vs. 27.0±8.7, p=0.56). SMA attenuation was higher in multiphasic protocol compared to split-bolus protocol (336.5±97.5HU vs. 258.0±67.3HU, p<0.001) with similar SMV attenuation (multiphasic 213.7±58.4HU vs. split-bolus 194.2±52.2HU, p=0.14). Optimal phase of bowel, liver, and spleen enhancement was seen in similar high proportion (94-99%) in both protocols. There were 8/40 (20%) positive cases of mesenteric ischemia in each group. There was no difference in the diagnostic confidence of the readers for evaluation of the mesenteric vessels and bowel ischemia. There were no missed cases of mesenteric ischemia in either group. Mean effective dose was 42% lower in the split-bolus group, p<0.001. There was a higher number of axial images to review in multiphasic protocol compared to split-bolus protocol (437.9±48.7 vs. 263.5±31.2, p<0.001). The split-bolus protocol for evaluation of mesenteric ischemia is clinically feasible with confident and accurate diagnostic ability, while reducing number of images and decreasing radiation exposure to the patient.

Added value of multiphase CTA imaging for thrombus perviousness assessment

PurposeThrombus perviousness has been associated with favorable functional outcome in acute ischemic stroke (AIS) patients. Measuring thrombus perviousness on CTA may be suboptimal due to potential delay in contrast agent arrival in occluded arteries at the moment of imaging. Dynamic sequences acquired over time can potentially overcome this issue. We investigate if dynamic CTA has added value in assessing thrombus perviousness.MethodsProspectively collected image data of AIS patients with proven occlusion of the anterior or posterior circulation with thin-slice multi-phase CTA (MCTA) and non-contrast CT were co-registered (n = 221). Thrombus attenuation increase (TAI; a perviousness measure) was measured for the arterial, venous, and delayed phase of the MCTA and time-invariant CTAs (TiCTA). Associations with favorable clinical outcome (90-day mRS ≤ 2) were assessed using univariate and multivariable regressions and calculating areas under receiver operating curves (AUC).ResultsTAI determined from the arterial phase CTA was superior in the association with favorable outcome with OR = 1.21 per 10 HU increase (95%CI 1.04–1.41, AUC 0.62, p = 0.014) compared to any other phase (venous 1.14(95%CI 1.01–1.30, AUC 0.58, p = 0.033), delayed 1.046(95%CI 0.919–1.19, AUC 0.53, p = 0.50)), and TiCTA (1.15(95%CI 1.02–1.30, AUC 0.60, p = 0.022). In the multivariable model, only TAI on arterial phase was significantly associated with favorable outcome (aOR 1.59, 95%CI 1.04–2.43, p = 0.032).ConclusionAssociation between TAI with functional outcome was optimal on arterial-phase CTA such that dynamic CTA imaging has no additional benefits in current thrombus perviousness assessment, thereby suggesting that the delay of contrast arrival at the clot is a key variable for patient functional outcome.

Improved Detection of Anterior Circulation Occlusions: The "Delayed Vessel Sign" on Multiphase CT Angiography.

Multiphase CTA, a technique to dynamically assess the vasculature in acute ischemic stroke, was primarily developed to evaluate collateral filling. We have observed that it is also useful in identifying distal anterior circulation occlusions due to delayed anterior circulation opacification on multiphase CTA, an observation we term the "delayed vessel sign." We aimed to determine the usefulness of this sign by comparing multiphase CTA with single-phase CTA. All 23 distal anterior circulation occlusions during a 2-year period were included. Ten M1-segment occlusions and 10 cases without a vessel occlusion were also included. All patients had follow-up imaging confirming the diagnosis. Initially, the noncontrast CT and first phase of the multiphase CTA study for each patient were blindly evaluated (2 neuroradiologists, 2 radiology trainees) for an anterior circulation occlusion. Readers' confidence, speed, and sensitivity of detection were recorded. Readers were then educated on the "delayed vessel sign," and each multiphase CTA study was re-examined for a vessel occlusion after at least 14 days. There was significant improvement in the sensitivity of detection of distal anterior circulation vessel occlusions (P < .001), overall confidence (P < .001), and time taken to interpret (P < .001) with multiphase CTA compared with single-phase CTA. Readers preferred MIP images compared with source images in >90% of cases. The delayed vessel sign is a reliable indicator of anterior circulation vessel occlusion, particularly in cases involving distal branches. Assessment of the later phases of multiphase CTA for the delayed vessel sign leads to a significant improvement in the speed and confidence of interpretation, compared with single-phase CTA.

Regional Comparison of Multiphase Computed Tomographic Angiography and Computed Tomographic Perfusion for Prediction of Tissue Fate in Ischemic Stroke.

Within different brain regions, we determine the comparative value of multiphase computed tomographic angiography (mCTA) and computed tomographic perfusion (CTP) in predicting follow-up infarction. Patients with M1-middle cerebral artery occlusions were prospectively included in this multicenter study. Regional analysis was performed for each patient within Alberta Stroke Program Early CT Score regions M2 to M6. Regional pial vessel filling was assessed on mCTA in 3 ways: (1) Washout of contrast within pial vessels; (2) Extent of maximal pial vessel enhancement compared with contralateral hemisphere; (3) Delay in maximal pial vessel enhancement compared with contralateral hemisphere. Cerebral blood flow, cerebral blood volume, and Tmax data were extracted within these Alberta Stroke Program Early CT Score regions. Twenty-four- to 36-hour magnetic resonance imaging/CT was assessed for infarct in each Alberta Stroke Program Early CT Score region (defined as >20% infarction within that region). Mixed effects logistic regression models were used to compare mCTA and CTP parameters when predicting brain infarction. Area under the receiver operating characteristics was used to assess discriminative value of statistical models. Seventy-seven patients were included. mCTA parameter washout and CTP parameter Tmax were significantly associated with follow-up infarction in all models (P<0.05). The area under the receiver operating characteristic for mCTA models ranged from 92% to 94% and was not different compared with all CTP models (P>0.05). Mean Tmax and cerebral blood volume values were significantly different between each washout score (P<0.01) and each delay score category (P<0.01). Mean Tmax, cerebral blood flow, and cerebral blood volume values were significantly different between each extent score category (P<0.05). Similar to CTP, multiphase CTA can be used to predict tissue fate regionally in acute ischemic stroke patients.

Abstract WMP21: The Delayed Vessel Sign in Multiphase CT Angiography: Facilitating the Rapid On-table Confirmation of Acute Ischaemic Stroke

Objective: The “delayed vessel sign” refers to the presence of relative unilateral delayed enhancement of a vessel or vessels in the anterior circulation on delayed phases of a multiphase CTA (MPCTA) distal to the point of vessel occlusion. We aimed to determine if educating radiologists on the “delayed vessel sign” would improve sensitivity, confidence and speed in the detection of distal anterior circulation vessel occlusions in the suspected stroke patient. Methods: Non-contrast CT (NCCT) and MPCTA studies of 53 individual patients, who presented with signs/symptoms of acute anterior circulation stroke, were retrospectively selected by an independent radiologist. 15 cases without a vessel occlusion, 15 cases with a M1 occlusion and 23 cases with a distal anterior circulation (A2/M2/M3) occlusion were included. Initially, NCCT and single phase CTA (SPCTA) studies were independently interpreted by four observers (two neuroradiologists, two radiology trainees) and observers’ confidence (scale 1-5), speed and sensitivity of detection were recorded. Observers were then educated on the “delayed vessel sign” and each study was re-examined after an interval of at least 14 days. Results: There was a significant improvement in the sensitivity of detection of distal anterior circulation vessel occlusions on MPCTA compared to SPCTA (p=0.0003) and this was also true for M1 occlusions (p=0.045). Overall confidence was 4.0 for SPCTA and 4.88 with MPCTA (p&lt;0.0001). Average time taken to interpret each case on SPCTA was 85.5s and decreased to 40.1s with MPCTA (p&lt;0.0001). Conclusion: The “delayed vessel sign” is a reliable indicator of ipsilateral vessel occlusion, and is particularly useful in cases involving distal MCA branches where the occlusion is not easily identified on the initial angiographic phase. We have found this sign facilitates the rapid on-table confirmation of acute ischemic stroke, even when small vessels are involved and the clinical diagnosis is uncertain.