RPS 1411b - Stroke

Purpose:

To investigate the value of CT-perfusion obtained before and immediately after mechanical thrombectomy (MT) for the outcome prediction in patients with acute ischaemic stroke.

Methods and materials:

CT-perfusion was performed both before and immediately after MT in 42 patients. Perfusion maps (CBV, CBF, MTT, TMax, and TTP) were calculated and areas of hypoperfusion were segmented in the baseline exam. Quantitative data was extracted from the segmented area at baseline and the corresponding area after MT. Full clinical and interventional data was available. Patient outcome was defined with the modified Rankin scale (mRS) at 90 days into mRS≤2 (good outcome) and mRS>2 (bad outcome). Multivariable logistic regression was performed to assess the value of baseline clinical data, ASPECTS, TICI score, and pre- and post-treatment CT-perfusion parameters for predicting the treatment outcome.

Results:

Inclusion of both pre- and post-treatment CT-perfusion (in addition to clinical parameters, ASPECTS, and TICI score) yielded the best performance with an AUC of 0.903 (95% CI, 0.802-1.000). Specifically, pre- and post-treatment TTP (OR=0.401/1.51, p=0.012/0.029) as well as age (OR=1.113, p=0.041) were independent predictors of treatment failure. The performance of this model was significantly higher (p=0.013) compared to a model that included only pre-treatment characteristics (baseline CT-perfusion, clinical parameters, and ASPECTS) with an AUC of 0.830 (95% CI, 0.699-0.961). Models without CT-perfusion parameters performed significantly worse with an AUC of 0.780 (95% CI, 0.642-0.918) when based on clinical/angiographic parameters and ASPECTS only (p=0.023).

Conclusion:

CT-perfusion parameters obtained immediately after MT improve the treatment outcome prediction in patients with acute ischaemic stroke beyond baseline clinical/angiographic parameters, ASPECTS, and pre-treatment CT-perfusion parameters.

Limitations:

The small patient sample and lack of multicentric data.

Ethics committee approval

Approval obtained prior to analysis.

Funding:

No funding was received for this work.

Purpose:

Why does mechanical thrombectomy (MT) of the posterior circulation sometimes fail? Failed MT in the posterior circulation has not been investigated and leads to a fatal outcome in most cases, while reasons for failed MT in the anterior circulation have been recently well defined.

Methods and materials:

In this retrospective analysis of an institutional review board-approved prospective stroke database in a comprehensive stroke centre, we compared patients with successful and failed MT of the posterior circulation from March 2009-April 2019 (group A: mTICI 0-1 vs group B: mTICI 2-3). Cases of failed recanalisation were further investigated for reasons of MT failure. Statistical analysis included univariate and multivariate analysis for investigating clinical or interventional predictors of MT failure.

Results:

225 patients were analysed (group A: 30 and group B: 195). Group A showed a significantly lower follow-up pASPECTS after MT, a higher NIHSS at discharge, and a higher mRS 90 days after the stroke onset. The main reasons for a failed recanalisation were futile vascular access, a failed passage of the occluded vessel, and complications after passing the occlusion. Stent-assisted PTA was an independent predictor for MT failure and played a decisive role in most of the failed MTs atherosclerosis.

Conclusion:

For the first time, this study depicts futile vascular access, failed passage of the vessel occlusion, and interventional complications to be main reasons for recanalisation failure in MT of the posterior circulation. Atherosclerosis and the struggle with stent-assisted PTA in the posterior circulation are, opposed to failed MT in the anterior circulation, the main sources of revascularisation failure.

Limitations:

The mono-centre retrospective approach.

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

Can quantitative measurements in vascular territories of the brain in multiphase CT angiography (MP-CTA) provide the same information as CT-perfusion (CTP) and be used to identify ischaemic regions after cerebral stroke?

Methods and materials:

Patients were included on the basis of having undergone MP-CTA and CTP on a local dual-energy CT on suspicion of cerebral stroke. Another criteria was for the spectral-based images to be available for retrospective analysis. 9 patients were found, 5 without detected perfusion deficits on CTP and 4 with. Iodine density and HU, corresponding to a conventional 120 kV image and to a virtual mono-energetic image using 40 keV-photons, were measured in vascular territories of the brain for all phases of the MP-CTA exam and in the non-contrast CT. Iodine density and HU were plotted as functions of the imaged phase. The plots were evaluated by comparing the left and right hemispheres. Delayed arrival of the contrast material was deemed indicative of ischaemia. These results were then compared to the results of the CTP in order to see if a correlation could be found.

Results:

Patients without detected perfusion deficits displayed little or no difference between hemispheres. Patients with perfusion deficits showed signs of ischaemia in some or all regions as the CTP. Iodine density generated a larger separation between healthy and ischaemic tissue than HU.

Conclusion:

Quantitative analysis of MP-CTA shows the potential for being able to provide the same information as the CTP. Measurements performed on iodine density, instead of HU, generated a larger separation between sick and healthy tissue making it a more sensitive method.

Limitations:

The limited patient material and data acquisition based on vendor-specific software.

Ethics committee approval

This study was approved by the ethics committee.

Funding:

No funding was received for this work.

Purpose:

This retrospective single-centre study compared three threshold settings for automated analysis of the ischemic core (IC) and penumbral volumes using computed tomographic perfusion (CTP) and their accuracy for predicting final infarct volume (FIV) in patients with anterior circulation acute ischaemic stroke (AIS).

Methods and materials:

52 consecutive AIS patients undergoing mechanical thrombectomy (November 2015–March 2018) were included. Perfusion images were retrospectively analysed using a single CT neuro perfusion application (syngo.via 4.1, Siemens Healthcare GmbH). 3 threshold values (S1–S3) were derived from another commercial package (RAPID; iSchema View) (S1), up-to-date syngo.via default values (S2), and adapted values for syngo.via from a reference study (S3). The results were compared with FIV determined by follow-up non-contrast CT.

Results:

The median IC volume (mL) was 24.6 (interquartile range: 13.7-58.1), with S1 and 30.1 (20.1-53.1) with S2/S3. After removing the contralateral hemisphere from the analysis, the median IC volume decreased by 1.33 (0-3.14), with S1 versus 9.13 (6.24-14.82) with S2/S3. The median penumbral volume (mL) was 74.52 (49.64-131.91), 77.86 (46.56-99.23), and 173.23 (125.86-200.64) for S1, S2, and S3, respectively. Limiting the analysis to the affected hemisphere, the penumbral volume decreased by 1.6 (0.13-9.02), 19.29 (12.59-26.52), and 58.33 mL (45.53-74.84) for S1, S2, and S3, respectively. The correlation between IC and FIV was highest in patients with successful recanalisation in <113 min (r=0.881 for S1; r=0.877 for S2/S3).

Conclusion:

Optimising threshold settings significantly improves the accuracy of the estimated IC and penumbral volumes. International consensus guidelines based on larger multicentre studies should be established to support the standardisation of volumetric analysis in clinical decision-making.

Limitations:

The small patient population and CTP brain coverage limited to 10 cm leading to potential underestimation of IC or penumbral volume.

Ethics committee approval

Approved by the Hospital Research Ethics Board.

Funding:

Governmental funding from the Hospital Research Commission.