Perfusion-Derived Dynamic 4D CT Angiography Identifies Carotid Pseudo-Occlusion in Hyperacute Stroke

Differentiation of Acute Internal Carotid Artery Occlusion Etiology on Computed Tomography Angiography: Diagnostic Tree for Preparing Endovascular Treatment

BACKGROUND AND PURPOSE

This study aimed to identify the imaging characteristics and discriminate the etiology of acute internal carotid artery occlusion (ICAO) on computed tomography angiography (CTA) in patients with acute ischemic stroke.

MATERIALS AND METHODS

We retrospectively evaluated consecutive patients who underwent endovascular thrombectomy for acute ICAO. Contrast filling of the extracranial ICA in preprocedural CTA was considered apparent ICAO. Non-contrast filling of the extracranial ICA was evaluated according to the contrast-filled lumen configuration, lumen margin and location, Hounsfield units of the non-attenuating segment, and presence of calcification or an intimal flap. Digital subtraction angiography findings were the reference standard for ICAO etiology and the occlusion site. A diagnostic tree was derived using significant variables according to pseudo-occlusion, atherosclerotic vascular disease (ASVD), thrombotic occlusion, and dissection.

RESULTS

A total of 114 patients showed apparent ICAO (n = 21), pseudo-occlusion (n = 51), ASVD (n = 27), thrombotic occlusion (n = 9), or dissection (n = 6). Most pseudo-occlusions (50/51, 98.0%) showed dependent locations with ill-defined contrast column margins and classic flame or beak shapes. The most common occlusion site of pseudo-occlusion was the petro-cavernous ICA (n = 32, 62.7%). Apparent ICAO mainly appeared in cases with occlusion distal to the posterior communicating artery orifice. ASVD showed beak or blunt shapes in the presence of low-density plaques or dense calcifications. Dissection revealed flame- or beak-shaped appearances with circumscribed margins. Thrombotic occlusions tended to appear blunt-shaped. The decision-tree model showed a 92.5% overall accuracy.

CONCLUSIONS

CTA characteristics may help diagnose ICAO etiology. We provide a simple and easy decision-making model to inform endovascular thrombectomy.

Single vs. Multiphase Computed Tomography angiography in acute internal carotid artery occlusion: An accuracy and interobserver agreement study

OBJECTIVE

Accurate differentiation between the intracranial and extracranial location of the acute internal carotid artery (ICA) occlusion is essential for guiding treatment decisions and mechanical thrombectomy planning. Multiphase Computed Tomography angiography (mCTA) appears to be superior to Single-phase Computed Tomography angiography (sCTA) in the evaluation of acute ICA occlusions. The main objective of our research is to study the accuracy of mCTA compared to sCTA in distinguishing isolated acute intracranial ICA occlusion from extracranial or tandem occlusion.

METHODS

Two observers independently analyzed sCTA and mCTA of patients with acute ICA occlusion at two different time points. The location of the occlusion was categorized as intracranial or extracranial for both imaging techniques and then compared with digital subtraction angiography (gold standard). Sensitivity and specificity rates for isolated intracranial ICA occlusion on sCTA and mCTA were calculated. Kappa statistics were used to assess interobserver agreement.

RESULTS

The sensitivity of sCTA and mCTA was 48.28% (28.36%-68.19%) and 79.31% (62.84%-95.78%) respectively for the diagnosis of isolated intracranial ICA occlusion, with an almost perfect interobserver agreement between both observers (p < 0.001).

CONCLUSIONS

Our research suggests that mCTA is more accurate than sCTA in distinguishing isolated intracranial occlusions from extracranial or tandem occlusions.

Outcomes in acute ischemic stroke patients undergoing endovascular thrombectomy: Cervical internal carotid artery pseudo-occlusion vs. true occlusion

Background and purpose

Pseudo-occlusion of the cervical internal carotid artery (cICA) refers to an absence of intraluminal contrast on computed tomography angiography (CTA), while the artery is patent on digital subtraction angiography during endovascular thrombectomy. We aimed to compare the outcomes between the cICA pseudo-occlusion and true occlusion after thrombectomy.

Methods

We retrospectively analyzed patients with apparent cICA occlusion on CTA who underwent thrombectomy between January 2016 and August 2021, and divided them into the pseudo-occlusion and true occlusion groups based on angiographic exploration. Recanalization failure was defined as a modified Thrombolysis in Cerebral Infarction score of 0-2a. Poor outcome was defined as a 90-day modified Rankin Scale score of 3-6. Propensity score matching was performed to compare the outcomes. Sensitivity analysis using multivariate-adjusted regression in the original cohort was conducted to test the robustness of the findings.

Results

Of the 146 patients included, 79 patients (54.1%) had cICA pseudo-occlusion and 67 patients (45.9%) had true occlusion. Following 1:1 propensity score-matched analysis, patients with pseudo-occlusion had an increased likelihood of recanalization failure (OR, 3.18; 95% CI, 1.06-9.59; P = 0.040) and poor outcome (OR, 2.80; 95% CI, 1.07-7.30; P = 0.035) compared with patients with true occlusion. Sensitivity analysis showed that cICA pseudo-occlusion remained independently associated with recanalization failure (OR, 2.55; 95% CI, 1.07-6.09; P = 0.036) and poor outcome (OR, 2.48; 95% CI, 1.08-5.67; P = 0.032).

Conclusions

Patients with cICA pseudo-occlusion on CTA treated with thrombectomy had an increased risk of reperfusion failure and poor outcome compared with true occlusion patients.

The additional value of high-resolution vessel wall imaging in screening suitable chronic internal carotid artery occlusion candidates for endovascular recanalization: comparison with digital subtraction angiography

BACKGROUND

High-resolution vessel wall imaging (HR-VWI) can provide information about exact occluded length, etiology, and the presence of intraluminal thrombus or residual cavity.

PURPOSE

To investigate the extra value of HR-VWI in screening patients with chronic internal carotid artery occlusion (CICAO) for recanalization suitability in comparison with digital subtraction angiography (DSA).

MATERIAL AND METHODS

We retrospectively reviewed patients who underwent endovascular recanalization with no internal carotid artery signal on magnetic resonance angiography (MRA) and whose both preoperative DSA and HR-VWI data were available. Patients were classified into type I (focal occlusion distal to ophthalmic artery), type II or III (occlusion proximal or at/distal to clinoid segment), and near-occlusion. Occlusion etiology and suitability for recanalization were analyzed both on preoperative DSA and HR-VWI. Accuracy of occlusion classification and differences in the modified Rankin scale scores between the baseline and follow-up were estimated.

RESULTS

A total of 20 patients were included. With intraoperative DSA as the gold standard, we found HR-VWI could additionally show intraluminal thrombi. Preoperative DSA misclassified one near-occlusion, one type I occlusion, and one type II occlusion as type III occlusions, and one near-occlusion as a type II occlusion. Therefore, compared with the preoperative DSA, three additional cases were successfully recanalized based on HR-VWI. The accuracy of HR-VWI was higher than preoperative DSA (100% vs. 80%). Prognosis improvement of type I was significantly better than type II and near-occlusion (P<0.05).

CONCLUSION

HR-VWI can identify occluded etiology, extent, and classification of CICAO. This information is potentially useful in screening candidates for endovascular recanalization and helpful to indicate prognosis.

Delayed Contrast-Enhanced MR Angiography for the Assessment of Internal Carotid Bulb Patency in the Context of Acute Ischemic Stroke: An Accuracy, Interrater, and Intrarater Agreement Study

BACKGROUND AND PURPOSE

CTA has shown limited accuracy and reliability in distinguishing tandem occlusions and pseudo-occlusions on initial acute stroke imaging. The utility of early and delayed contrast-enhanced MRA in this setting is unknown. We aimed to assess the accuracy and reliability of early and delayed contrast-enhanced MRA for carotid bulb patency in patients with acute ischemic stroke.

MATERIALS AND METHODS

We retrospectively reviewed patients who had ICA occlusion and underwent thrombectomy with preprocedural early and delayed contrast-enhanced MRA in a single comprehensive stroke center. During 2 sessions, 10 raters independently assessed 32 cases with early contrast-enhanced MRA (with an additional delayed contrast-enhanced MRA sequence during the second reading session). Their judgments were compared with DSA as a reference standard. Accuracy and interrater agreement were measured. Five raters undertook a third reading session to assess intrarater agreement.

RESULTS

Accuracy for the assessment of carotid bulb patency with early contrast-enhanced MRA was limited (69%; 95% CI, 59%-79%), with moderate interrater agreement (κ = 0.42; 95% CI, 0.27-0.55). The second reading with an additional delayed contrast-enhanced MRA sequence improved both accuracy (82%; 95% CI, 73%-91%; P < .001) (raters corrected 43%-77% of incorrect diagnoses with early contrast-enhanced MRA alone; mean = 59%) and interrater agreement (κ = 0.56; 95% CI, 0.41-0.73; P = .07). Intrarater agreement was almost perfect, substantial, and moderate for 3, 1, and 1 raters.

CONCLUSIONS

Early contrast-enhanced MRA has limited accuracy and repeatability for the evaluation of carotid bulb patency in acute ischemic stroke. The additional delayed contrast-enhanced MRA sequence may improve accuracy and reliability.

Single rotation CTA of extracranial carotids integrated with cerebral CTP provides sufficient quality for decision making in patients with ischaemic stroke

PURPOSE

Large volume computed tomography scanners with 16 cm Z-axis single rotation coverage enable joggle-mode scanning of cerebral computed tomography perfusion and single rotation computed tomography angiography of cervical arteries. Our study aims to evaluate the feasibility of scanning cervical arteries, acquired with single rotation computed tomography angiography during computed tomography perfusion in ischaemic stroke patients.

MATERIALS AND METHODS

A total of 143 patients were scanned with a single contrast medium injection of 60 ml. Hounsfield units of the cervical arteries and veins were objectively measured and carotid bifurcations were subjectively reviewed. The incidence of artefacts and supra-aortic vessel coverage was recorded.

RESULTS

Single rotation computed tomography angiography of the neck demonstrated supra-aortic vessels to their origins in 58 (40.6%) patients. Ninety-nine per cent (1140/1152) of arterial segments were adequately opacified (≥150 Hounsfield units). Arteries were adequately contrasted compared to veins in 81.3% (915/1126) of segments. However, the opacification was reversed in 14.0% (158/1126) of segments, indicating a delayed timing of acquisition; 95.5% (273/286) of carotid bifurcations were of good image quality. Measurement of internal carotid artery stenosis in single rotation computed tomography angiography according to the North American Symptomatic Carotid Endarterectomy Trial correlated well with digital subtraction angiography (R=0.87, P<0.05). Significant artefacts resulted from metal/dental implants (10.5%), contrast in central veins (7.7%) and the shoulder region (4.9%).

CONCLUSION

Single rotation computed tomography angiography of the neck incorporated into cerebral computed tomography perfusion with single contrast medium administration revealed adequate image quality for further decision-making in our patient sample. The main drawbacks were inadequate coverage of supra-aortic arteries and possible delay in timing of the joggle.

Assessment of Apparent Internal Carotid Tandem Occlusion on High-Resolution Vessel Wall Imaging: Comparison with Digital Subtraction Angiography

BACKGROUND AND PURPOSE

Not all tandem occlusions diagnosed on traditional vascular imaging modalities, such as MRA, represent actual complete ICA occlusion. This study aimed to explore the utility of high-resolution vessel wall imaging in identifying true ICA tandem occlusions and screening patients for their suitability for endovascular recanalization.

MATERIALS AND METHODS

Patients with no signal in the ICA on MRA were retrospectively reviewed. Two neuroradiologists independently reviewed their high-resolution vessel wall images to assess whether there were true tandem occlusions and categorized all cases into intracranial ICA occlusion, extracranial ICA occlusion, tandem occlusion, or near-occlusion. DSA classified patient images into the same 4 categories, which were used as the comparison with high-resolution vessel wall imaging. The suitability for recanalization of occluded vessels was evaluated on high-resolution vessel wall imaging compared with DSA.

RESULTS

Forty-five patients with no ICA signal on MRA who had available high-resolution vessel wall imaging and DSA images were included. Among the 34 patients (34/45, 75.6%) with tandem occlusions on DSA, 18 cases also showed tandem occlusions on high-resolution vessel wall imaging. The remaining 16 patients, intracranial ICA, extracranial ICA occlusions and near-occlusions were found in 2, 6, and 8 patients, respectively, on the basis of high-resolution vessel wall imaging. A total of 20 cases (20/45, 44.4%) were considered suitable for recanalization on the basis of both DSA and high-resolution vessel wall imaging. Among the 25 patients deemed unsuitable for recanalization by DSA, 11 were deemed suitable for recanalization by high-resolution vessel wall imaging.

CONCLUSIONS

High-resolution vessel wall imaging could allow identification of true ICA tandem occlusion in patients with an absence of signal on MRA. Findings on high-resolution vessel wall imaging can be used to screen more suitable candidates for recanalization therapy.

Beyond the collaterals: Additional value of multiphase CTA in acute ischemic stroke evaluation

PURPOSE

Multiphase computed tomography angiography (MP-CTA) is an innovative imaging tool that can give those managing acute ischemic stroke temporal information on degree and extent of pial collateral arterial filling in the affected brain. We sought to estimate the incidence of false-positive or -negative evaluation of the carotid bifurcation or intracranial thrombus on single-phase CTA (SP-CTA) compared with MP-CTA.

MATERIAL AND METHODS

A single-center, retrospective consecutive review was conducted of imaging and clinical records of 150 patients in two months who presented with neurological symptoms with a National Institutes of Health Stroke Scale score ≥ 2 and who received an MP-CTA as part of their investigative work-up. The cohort consisted of 52.3% male and 47.7% female patients. Median individual age was 68 years (interquartile range 60-79). Extracranial and intracranial vessel images of the initial early arterial phase were evaluated and compared with late arterial and early venous phase images.

RESULTS

In the cohort of 150 patients, in three patients (2%) SP-CTA would have led to an incorrect diagnosis and management without MP-CTA-acquired source imaging. The three scenarios represented differentiating a carotid string sign from internal carotid artery occlusion, determining the appearance and extent of thrombus in carotid T-occlusion, and differentiating slow flow and contrast mixing-related artifacts from intraluminal thrombus.

CONCLUSIONS

In addition to improving assessment of collateral circulation in acute stroke patients, MP-CTA is also useful in assessing specific flow-related scenarios for which SP-CTA may give spurious results.

Diagnostic accuracy of emergency CT angiography for presumed tandem internal carotid artery occlusion before acute endovascular therapy

BACKGROUND

Extracranial internal carotid artery (ICA) occlusion can be overestimated on emergent single phase CT angiography (CTA) of stroke patients with isolated intracranial ICA occlusion. We aimed to measure the ability of identifying the extracranial site of presumed tandem ICA occlusions on pre-procedural CTA relative to catheter angiography during acute endovascular stroke therapy.

METHODS

Retrospective study of patients with intracranial ICA occlusion, with or without extracranial ICA occlusion, who underwent single phase CTA before acute endovascular treatment. Two neuroradiologists reviewed CTA images for the presence or absence of extracranial ICA occlusion, blinded to the catheter angiography results. The sensitivity, specificity, and predictive values of presumed extracranial ICA occlusions on CTA were calculated in reference to catheter angiography.

RESULTS

91 stroke patients with acute intracranial ICA occlusion met the inclusion criteria for the study. 24% of patients (22/91) had tandem ICA occlusion confirmed on catheter angiography. Single phase CTA had a sensitivity of 95.5% (95% CI 77.2 to 99.9%) and a specificity of 69.6% (95% CI 57.3 to 80.1%) for concomitant extracranial ICA occlusion (false positive rate 30.4%). The positive and negative predictive values of single phase CTA for extracranial ICA occlusion in the presence of a distal ICA occlusion were 50% (95% CI 34.2 to 65.8%) and 98% (95% CI 89.1 to 100%), respectively.

CONCLUSIONS

Emergency single phase CTA is highly sensitive but has reduced specificity to identify extracranial ICA occlusion in patients with intracranial ICA occlusion, which may confound planning for acute endovascular stroke therapy and cause over exclusion of patients with isolated ICA terminus occlusion from clinical trials.

Automatic centerline extraction of cerebrovascular in 4D CTA based on tubular features

Vascular centerlines have crucial significance in reconstruction, registration, segmentation and vascular parameter analysis. The extraction of vessel structures remains a difficult problem in the completeness and continuity of results. In this paper, we present a novel method to extract cerebrovascular centerlines from four-dimensional computed tomography angiography images. Tubular features and vascular directions are used to extract initial centerlines, and the offset correction is introduced in the vascular orthogonal plane. In addition, we also present a post-processing method to connect interruptions of centerlines. We perform a quantitative validation using clinical images and public data sets of MRA brain images. Our experimental results demonstrate that the proposed algorithm not only shows higher accuracy in complicated vessel structures, but also outperforms previous approaches in terms of high validity and universality.

Pseudo-Occlusion of the Internal Carotid Artery Predicts Poor Outcome After Reperfusion Therapy

Background and Purpose—

This study aimed to evaluate the occurrence rate of the internal carotid artery pseudo-occlusion (ICA-PO) on 4-dimensional–computed tomography angiography and to investigate its relationship with clinical outcome after reperfusion therapy.

Methods—

In this case–control study, we retrospectively reviewed our prospectively collected database for consecutive acute ischemic stroke patients who received reperfusion therapy between June 2009 and February 2017. ICA-PO was defined when the arterial segment was not opacified on peak arterial phase yet was subsequently patent after artery peak phase on 4-dimensional–computed tomography angiography. Poor outcome was defined as 3-month modified Rankin Scale of 4 to 6. Binary logistic regression was used to investigate the relationship of ICA-PO with poor outcome and the rate of reperfusion, respectively.

Results—

A total of 143 patients with isolated middle cerebral artery occlusion were included and 30 (21.0%) had ICA-PO. Patients with ICA-PO were more likely to have poor outcome (80.0% versus 37.2%; P <0.001) and a lower rate of reperfusion (45.8% versus 69.0%; P =0.033) than those without. Binary logistic regression revealed that ICA-PO was independently associated with poor outcome (odds ratio, 7.957; 95% confidence interval, 1.655–34.869; P =0.009) and reperfusion at 24 hours (odds ratio, 0.150; 95% confidence interval, 0.045–0.500; P =0.002) after adjustment. Among patients with no reperfusion, all ICA-PO patients obtained poor outcome, whereas only 45.2% non-PO patients underwent poor outcome ( P =0.001).

Conclusions—

Four dimensional-computed tomography angiography is a useful noninvasive technique to identify ICA-PO. Patients with ICA-PO are prone to undergo poor outcome from reperfusion therapy, especially when reperfusion is not achieved.

Accuracy of CT Angiography for Differentiating Pseudo-Occlusion from True Occlusion or High-Grade Stenosis of the Extracranial ICA in Acute Ischemic Stroke: A Retrospective MR CLEAN Substudy

BACKGROUND AND PURPOSE

The absence of opacification on CTA in the extracranial ICA in acute ischemic stroke may be caused by atherosclerotic occlusion, dissection, or pseudo-occlusion. The latter is explained by sluggish or stagnant flow in a patent artery caused by a distal intracranial occlusion. This study aimed to explore the accuracy of CTA for differentiating pseudo-occlusion from true occlusion of the extracranial ICA.

MATERIALS AND METHODS

All patients from the Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands (MR CLEAN) with an apparent ICA occlusion on CTA and available DSA images were included. Two independent observers classified CTA images as atherosclerotic cause (occlusion/high-grade stenosis), dissection, or suspected pseudo-occlusion. Pseudo-occlusion was suspected if CTA showed a gradual contrast decline located above the level of the carotid bulb, especially in the presence of an occluded intracranial ICA bifurcation (T-occlusion). DSA images, classified into the same 3 categories, were used as the criterion standard.

RESULTS

In 108 of 476 patients (23%), CTA showed an apparent extracranial carotid occlusion. DSA was available in 46 of these, showing an atherosclerotic cause in 13 (28%), dissection in 16 (35%), and pseudo-occlusion in 17 (37%). The sensitivity for detecting pseudo-occlusion on CTA was 82% (95% CI, 57-96) for both observers; specificity was 76% (95% CI, 56-90) and 86% (95% CI, 68-96) for observers 1 and 2, respectively. The κ value for interobserver agreement was .77, indicating substantial agreement. T-occlusions were more frequent in pseudo- than true occlusions (82% versus 21%, P < .001).

CONCLUSIONS

On CTA, extracranial ICA pseudo-occlusions can be differentiated from true carotid occlusions.

Cervical ICA pseudo-occlusion on single phase CTA in patients with acute terminal ICA occlusion: what is the mechanism and can delayed CTA aid diagnosis?

Background

Single-phase CT angiography (CTA) forms the basis of hyperacute stroke imaging but many patients with terminal internal carotid artery (ICA) occlusion exhibit a pseudo-occlusion of the cervical ICA whereby a column of unopacified blood mimics a tandem cervical ICA lesion. We aimed to investigate the utility of a delayed phase acquisition to aid identification of a pseudo-occlusion and investigated the mechanism for this imaging artefact.

Methods

Thirteen patients with a pseudo-occlusion were compared with 13 patients without. CT, CTA, and digital subtraction angiographic images were reviewed by two interventional neuroradiologists for extension of thrombus into the ophthalmic segment, filling of the posterior communicating artery and ophthalmic artery, and for extension of contrast beyond the cervical segment and outline of the proximal clot surface by contrast on delayed imaging performed at 40 or 80 s.

Results

Those with a pseudo-occlusion demonstrated more frequent thrombus extension into the ophthalmic segment (100% vs 23%, P=0.0001), less frequent filling of the posterior communicating artery (15% vs 85%, P=0.0012), and less frequent filling of the ophthalmic artery (15% vs 92%, P=0.0002) compared with those without a pseudo-occlusion. Delayed CTA imaging showed contrast beyond the cervical segment and meeting the proximal clot face in 2/11 patients. Each of these two patients showed patency of the posterior communicating artery origin.

Conclusion

Thrombus extension into the ophthalmic segment and patency of the posterior communicating artery and ophthalmic artery seem to govern whether a patient with a terminal ICA occlusion exhibits a pseudo-occlusion. Delayed imaging was of limited value in identification of a pseudo-occlusion.

Mid-cervical flame-shaped pseudo-occlusion: diagnostic performance of mid-cervical flame-shaped extracranial internal carotid artery sign on computed tomographic angiography in hyperacute ischemic stroke

PURPOSE

Flame-shaped pseudo-occlusion of the extracranial internal carotid artery (ICA) is a flow-related phenomenon that creates computed tomographic angiography (CTA) and digital subtraction angiography (DSA) findings that mimic tandem intracranial-extracranial ICA occlusion or dissection. We aim to determine the diagnostic performance of mid-cervical flame-shaped extracranial ICA sign on CTA in hyperacute ischemic stroke patients.

METHODS

We retrospectively included consecutive anterior circulation ischemic stroke patients presenting within 6 h of symptom onset who underwent 4D brain CTA and arterial-phase neck CTA using a 320-detector CT scanner during August 2012 to July 2015. Two blinded readers independently reviewed arterial-phase neck CTA and characterized the extracranial ICA configurations into mid-cervical flame-shaped, proximal blunt/beak-shaped, and tubular-shaped groups. 4D whole brain CTA was used as a reference standard for intracranial ICA occlusion detection. Diagnostic performance of the mid-cervical flame-shaped extracranial ICA sign and interobserver reliability were calculated.

RESULTS

Of the 81 cases, 11 had isolated intracranial ICA occlusion, and 6 had true extracranial ICA occlusion. Mid-cervical flame-shaped extracranial ICA sign was found in 45.5% (5/11) of isolated intracranial ICA occlusions but none in the true extracranial ICA occlusion group. The sensitivity, specificity, PPV, NPV, and accuracy of the mid-cervical flame-shaped extracranial ICA sign for the detection of isolated intracranial ICA occlusion were 45.5, 100, 100, 92.1, and 92.6%, respectively. Interobserver reliability was 0.90.

CONCLUSION

The mid-cervical flame-shaped extracranial ICA sign may suggest the presence of isolated intracranial ICA occlusion and allow reliable exclusion of tandem extracranial-intracranial ICA occlusion in hyperacute ischemic stroke setting.

4D-CTA improves diagnostic certainty and accuracy in the detection of proximal intracranial anterior circulation occlusion in acute ischemic stroke

INTRODUCTION

In acute ischemic stroke, imaging of the cranio-cervical vessels is essential for intra-arterial treatment selection. Fast, reliable and easy accessible imaging is necessary 24 hours a day, 7 days a week. Radiologists in training and non-expert readers often perform initial reviewing. In this pilot study, the potential benefit of adding 4Dimensional-CT Angiography (4D-CTA) to the patient selection protocol for intra-arterial therapy is investigated.

MATERIALS AND METHODS

Twenty-five datasets of prospectively recruited patients, eligible for intra-arterial treatment, were enrolled. Four radiologists-in-training consecutively reviewed CTA, CT-Perfusion and 4D-CTA (post-processed from CTP datasets) and scored: occlusion-presence and diagnostic certainty (scale 1-10). Time-to-diagnosis was registered.

RESULTS

Arterial occlusion was present in 8 patients. Accuracy improved from 88-92% after CTA and CTP assessment to 96-100% after 4D-CTA assessment (P-values >0,05). Mean diagnostic certainty improved from 7,2-8,6 to 8,8-9,3 (P-values all < 0,05). Mean time to diagnosis increased from 3, 5, 5 and 4 minutes after CTA to 9, 14, 12, and 10 minutes after 4D-CTA.

CONCLUSION

4D-CTA as an additive to regular CTA and CT-Perfusion in patients with acute ischemic stroke eligible for intra-arterial treatment shows a tendency to increase diagnostic accuracy and improves diagnostic certainty, when reviewed by radiologist in training, while only mildly prolonging time to diagnosis.