Accuracy of CTA evaluations in daily clinical practice for large and medium vessel occlusion detection in suspected stroke patients

Diagnostic accuracy of large and medium vessel occlusions in acute stroke imaging by neurology residents and stroke fellows: A comparison of CT angiography alone and CT angiography with CT perfusion

INTRODUCTION

Neurology senior residents and stroke fellows are first to clinically assess and interpret imaging studies of patients presenting to the emergency department with acute stroke. The aim of this study was to compare the diagnostic accuracy of brain CT angiography (CTA) with and without CT perfusion (CTP) between neurology senior residents and stroke fellows.

METHODS

In this neuroimaging study, nine practitioners (four senior neurology residents (SNRs) and five stroke fellows (SFs)) clinically assessed and interpreted the imaging data of 50 cases (15 normal images, 21 large vessel occlusions (LVOs) and 14 medium vessel occlusions (MeVOs) in two sessions, 1 week apart in comparison to final diagnosis of experienced neuroradiologist and experienced stroke neurologist consensus. Interrater agreement of CTA alone and CTA with CTP was quantified using kappa statistics, sensitivity, specificity and overall accuracy.

RESULTS

Overall, arterial occlusions were correctly identified in 221/315 (70.1%) with CTA alone and in 266/315 (84.4%) with CTA and CTP (p < 0.001). The sensitivity of overall arterial occlusions detection with CTA alone was 94.2% (95% CI: 90.8%-96.6%) while with addition of CTP was 98% (95% CI: 95.6%-99.3%), The specificity of CTA alone was 74.7% (95% CI: 67.2%-81.3%) which increased with CTP to 84.4% (95% CI: 77.7%-89.8%). The likelihood of correct identification with CTA alone was 156/189 (82.54%) for LVOs and 65/126 (51.59%) for MeVOs. This increased to 169/189 (89.42%; p = 0.054) for LVOs and 97/126 (76.98%; p < 0.001) for MeVOs when the CTA images with CTP were viewed. There was good overall interrater agreement between readers when using CTA alone (k 0.71, 95% CI, 0.62-0.80) and almost perfect (k 0.85, 95% CI, 0.76-0.94) when CTP was added to the image for interpretation. CTA and CTP had a significantly lower median interquartile range (IQR) interpretation time than CTA alone (114 [IQR, 103-120] s vs 156 [IQR, 133-160] s, p < 0.001).

DISCUSSION

In cerebral arterial occlusions, the rate of LVO and MeVOs detections increases when adding CTP to CTA. The accuracy and time for diagnosing arterial occlusion can be significantly improved if CTP is added to CTA. As MeVOs are commonly missed by front-line neurology senior residents or stroke fellows, cases with significant deficits and no apparent arterial occlusions need to be reviewed with neuroradiological expertise.

ACR Appropriateness Criteria® Cerebrovascular Diseases-Stroke and Stroke-Related Conditions

Cerebrovascular disease encompasses a vast array of conditions. The imaging recommendations for stroke-related conditions involving noninflammatory steno-occlusive arterial and venous cerebrovascular disease including carotid stenosis, carotid dissection, intracranial large vessel occlusion, and cerebral venous sinus thrombosis are encompassed by this document. Additional imaging recommendations regarding complications of these conditions including intraparenchymal hemorrhage and completed ischemic strokes are also discussed. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

CTA and CTP for Detecting Distal Medium Vessel Occlusions: A Systematic Review and Meta-analysis

BACKGROUND

The optimal imaging method for detecting distal medium vessel occlusions (DMVOs) remains undefined.

PURPOSE

The objective of this study is to compare the diagnostic performance of CTA with CTP in detecting DMVOs.

DATA SOURCES

We searched PubMed, EMBASE, Web of Science Core Collection, and Cochrane Central Register of Controlled Trials up to March 31, 2023 (PROSPERO: CRD42022344006).

STUDY SELECTION

A total of 12 studies reporting accuracy values of CTA and/or CTP were included, comprising 2607 patients with 479 cases (18.3%) of DMVOs.

DATA ANALYSIS

Pooled sensitivity and specificity of both imaging methods were compared using a random-effects model. Subgroup analyses were performed based on the technique used in CTA (multi or single-phase) and the subtype of DMVOs (M2-only vs. M2 and other DMVOs). We applied Quality Assessment of Diagnostic Accuracy (QUADAS-2) tool and Grading of Recommendations, Assessment, Development and Evaluation (GRADE) quality assessment criteria.

DATA SYNTHESIS

CTA demonstrated significantly lower sensitivity compared to CTP in detecting DMVOs [0.74, 95%CI (0.63-0.82) vs. 0.89, 95% CI (0.82-0.93), P < 0.01]. When subgrouped into single-phase and multi-phase CTA, multi-phase CTA exhibited higher sensitivity for DMVO detection than single-phase CTA [0.91, 95%CI (0.85-0.94) vs. 0.64, 95%CI (0.56-0.71), P < .01], while reaching similar levels to CTP. The sensitivity of single-phase CTA substantially decreased when extending from M2 to other non-M2 DMVOs [0.74, 95%CI (0.63-0.83) vs. 0.61, 0.95%CI (0.53-0.68), P = .02].

LIMITATIONS

We identified an overall high risk of bias and low quality of evidence, attributable to the design and reference standards of most studies.

CONCLUSIONS

Our findings highlight a significantly lower sensitivity of single-phase CTA compared to multi-phase CTA and CTP in diagnosing DMVOs.

The diagnostic performance of artificial intelligence algorithms for identifying M2 segment middle cerebral artery occlusions: A systematic review and meta-analysis

BACKGROUND

Artificial intelligence (AI)-based algorithms have been developed to facilitate rapid and accurate computed tomography angiography (CTA) assessment in proximal large vessel occlusion (LVO) acute ischemic stroke, including internal carotid artery and M1 occlusions. In clinical practice, however, the detection of medium vessel occlusion (MeVO) represents an ongoing diagnostic challenge in which the added value of AI remains unclear.

PURPOSE

To assess the diagnostic performance of AI platforms for detecting M2 occlusions.

METHODS

Studies that report the diagnostic performance of AI-based detection of M2 occlusions were screened, and sensitivity and specificity data were extracted using the semi-automated AutoLit software (Nested Knowledge, MN) platform. STATA (version 16 IC; Stata Corporation, College Station, Texas, USA) was used to conduct all analyses.

RESULTS

Eight studies with a low risk of bias and significant heterogeneity were included in the quantitative and qualitative synthesis. The pooled estimates of sensitivity and specificity of AI platforms for M2 occlusion detection were 64% (95% CI, 53 to 74%) and 97% (95% CI, 84 to 100%), respectively. The area under the curve (AUC) in the SROC curve was 0.79 (95% CI, 0.74 to 0.83).

CONCLUSION

The current performance of the AI-based algorithm makes it more suitable as an adjunctive confirmatory tool rather than as an independent one for M2 occlusions. With the rapid development of such algorithms, it is anticipated that newer generations will likely perform much better.

Spatial CT perfusion data helpful in automatically locating vessel occlusions for acute ischemic stroke patients

Introduction

Locating a vessel occlusion is important for clinical decision support in stroke healthcare. The advent of endovascular thrombectomy beyond proximal large vessel occlusions spurs alternative approaches to locate vessel occlusions. We explore whether CT perfusion (CTP) data can help to automatically locate vessel occlusions.

Methods

We composed an atlas with the downstream regions of particular vessel segments. Occlusion of these segments should result in the hypoperfusion of the corresponding downstream region. We differentiated between seven-vessel occlusion locations (ICA, proximal M1, distal M1, M2, M3, ACA, and posterior circulation). We included 596 patients from the DUtch acute STroke (DUST) multicenter study. Each patient CTP data set was processed with perfusion software to determine the hypoperfused region. The downstream region with the highest overlap with the hypoperfused region was considered to indicate the vessel occlusion location. We assessed the indications from CTP against expert annotations from CTA.

Results

Our atlas-based model had a mean accuracy of 86% and could achieve substantial agreement with the annotations from CTA according to Cohen's kappa coefficient (up to 0.68). In particular, anterior large vessel occlusions and occlusions in the posterior circulation could be located with an accuracy of 80 and 92%, respectively.

Conclusion

The spatial layout of the hypoperfused region can help to automatically indicate the vessel occlusion location for acute ischemic stroke patients. However, variations in vessel architecture between patients seemed to limit the capacity of CTP data to distinguish between vessel occlusion locations more accurately.

Practice enhancements with FastStroke ColorViz analysis in acute ischemic stroke

In acute ischemic stroke (AIS), large vessel occlusion (LVO) and the status of pial collaterals are important factors in decision-making for further treatment such as endovascular therapy. Multiphasic CT Angiogram (mCTA) is the mainstay of AIS imaging, allowing detection of LVO, evaluation of intracranial arterial dynamics, and quantification of pial collaterals. However, thorough mCTA evaluation entails scrutiny of multiple image datasets, individually and then simultaneously, which can be time-consuming, causing a potential delay in treatment. ColorViz (FastStroke, GE Healthcare, Milwaukee, Wisconsin) is a novel CT application which combines mCTA information into a single color-coded dataset for quick, unequivocal evaluation of pial collaterals. In our practice, ColorViz is both time-saving and increases the diagnostic accuracy of LVO and pial collaterals as well as medium vessel, multivessel and posterior circulation occlusions. In this article, we discuss the practical aspects of ColorViz in patients presenting with AIS.