Mechanical thrombectomy for acute ischemic stroke in COVID-19 patients: multicenter experience in 111 cases.

BACKGROUND: Data on the frequency and outcome of mechanical thrombectomy (MT) for large vessel occlusion (LVO) in patients with COVID-19 is limited. Addressing this subject, we report our multicenter experience. METHODS: A retrospective cohort study was performed of consecutive acute stroke patients with COVID-19 infection treated with MT at 26 tertiary care centers between January 2020 and November 2021. Baseline demographics, angiographic outcome and clinical outcome evaluated by the modified Rankin Scale (mRS) at discharge and 90 days were noted. RESULTS: We identified 111 out of 11 365 (1%) patients with acute or subsided COVID-19 infection who underwent MT due to LVO. Cardioembolic events were the most common etiology for LVO (38.7%). Median baseline National Institutes of Health Stroke Scale score and Alberta Stroke Program Early CT Score were 16 (IQR 11.5-20) and 9 (IQR 7-10), respectively. Successful reperfusion (mTICI ≥2b) was achieved in 97/111 (87.4%) patients and 46/111 (41.4%) patients were reperfused completely. The procedure-related complication rate was 12.6% (14/111). Functional independence was achieved in 20/108 (18.5%) patients at discharge and 14/66 (21.2%) at 90 days follow-up. The in-hospital mortality rate was 30.6% (33/108). In the subgroup analysis, patients with severe acute COVID-19 infection requiring intubation had a mortality rate twice as high as patients with mild or moderate acute COVID-19 infection. Acute respiratory failure requiring ventilation and time interval from symptom onset to groin puncture were independent predictors for an unfavorable outcome in a logistic regression analysis. CONCLUSION: Our study showed a poor clinical outcome and high mortality, especially in patients with severe acute COVID-19 infection undergoing MT due to LVO.

Radiation exposure during angiographic interventions in interventional radiology - risk and fate of advanced procedures.

PURPOSE: Advanced angiographic procedures in interventional radiology are becoming more important and are more frequently used, especially in the treatment of several acute life-threatening diseases like stroke or aortic injury. In recent years, technical advancement has led to a broader spectrum of interventions and complex procedures with longer fluoroscopy times. This involves the risk of higher dose exposures, which, in rare cases, may cause deterministic radiation effects, e.g. erythema in patients undergoing angiographic procedures. Against this background, these procedures recently also became subject to national and international regulations regarding radiation protection. At the same time, individual risk assessment of possible stochastic radiation effects for each patient must be weighed up against the anticipated benefits of the therapy itself. Harmful effects of the administered dose are not limited to the patient but can also affect the radiologist and the medical staff. In particular, the development of cataracts in interventionalists is a rising matter of concern. Furthermore, long-term effects of repeated and prolonged x-ray exposure have long been neglected by radiologists but have come into focus in the past years. CONCLUSIONS: With all this in mind, this review discusses different efforts to reduce radiation exposition levels for patients and medical staff by means of technical, personal as well as organizational measures.

Feasibility of Ultra-High Resolution Supra-Aortic CT Angiography: An Assessment of Diagnostic Image Quality and Radiation Dose.

(1) Background: To evaluate diagnostic image quality and radiation exposure of ultra-high resolution cerebral Computed-Tomography (CT) angiography (CTA) obtained on an ultra-high resolution computed tomography scanner (UHR-CT). (2) Methods: Fifty consecutive patients with UHR-CTA were enrolled. Image reconstruction was processed with a 1024 × 1024 matrix and a slice thickness of 0.25 mm. Quantitative analyses comprising CT values, contrast-noise ratio (CNR) and signal-to-noise ratio (SNR) were performed. Subjective assessment of image quality, vessel contrast, noise, artefacts and delineation of different sized vessels were assessed by two readers on a 4-point scale. Radiation exposure was determined. (3) Results: Hounsfield values (ACI: 461.8 ± 16.8 HU; MCA: 406.1 ± 24.2 HU; BA: 412.2 ± 22.3 HU), SNR (ACI: 35.4 ± 13.1; MCA: 20.8 ± 12.4; BA: 23.7 ± 12.9) and CNR (ACI: 48.7 ± 21; MCA: 63.9 ± 26.9; BA: 48.1 ± 21.4) were remarkably high in all segments. Subjective analysis by two raters (fair agreement, k = 0.26) indicated excellent image qualities (image quality = 4; contrast = 4; noise = 3; artefacts = 4).Our analysis revealed a notably high traceability of the cerebral perforators (3 Points). Radiation exposure was at moderate dose levels (effective dose = 2.5 ± 0.6mSv). (4) Conclusions: UHR-CTA generates highly valuable image qualities that allow the depiction of vessels including cerebral perforators at acceptable dose levels. The UHR-CTA may therefore enhance the detection of small cerebral pathologies and may improve interpretability, especially in settings where high image qualities are crucial for the diagnostic accuracy.

Optimizing endovascular stroke treatment: removing the microcatheter before clot retrieval with stent-retrievers increases aspiration flow.

BACKGROUND: Flow control during endovascular stroke treatment with stent-retrievers is crucial for successful revascularization. The standard technique recommended by stent-retriever manufacturers implies obstruction of the respective access catheter by the microcatheter, through which the stent-retriever is delivered. This, in turn, results in reduced aspiration during thrombectomy. In order to maximize aspiration, we fully retract the microcatheter out of the access catheter before thrombectomy-an approach we term the 'bare wire thrombectomy' (BWT) technique. We verified the improved throughput with systematic in vitro studies and assessed the clinical effectiveness and safety of this method. METHODS: We compared aspiration flow of water through various access catheters (5-8 F) with a Rebar microcatheter (0.18 inch and 0.27 inch) and a Trevo stent-retriever using the standard technique and the BWT technique in vitro. We also retrospectively analyzed 302 retrieval maneuvers in 117 patients who received endovascular treatment with a stent-retriever between February 2010 and April 2015. RESULTS: In the in vitro experiment, removal of the microcatheter in all tested settings resulted in significantly increased aspiration flow through the access catheter (p<0.001). This effect was particularly pronounced in access catheters with a diameter of ≤7 F. In the clinical study, the revascularization rate (Thrombolysis In Cerebral Infarction ≥2b) was 91%. There were no complications associated with the BWT technique in 302 retrieval maneuvers. CONCLUSIONS: The BWT technique results in improved aspiration flow rates compared with the standard deployment technique. Our clinical data show that the BWT technique is effective and safe.

Radiation dose reduction in perfusion CT imaging of the brain: A review of the literature.

Perfusion CT (PCT) of the brain is widely used in the settings of acute ischemic stroke and vasospasm monitoring. The high radiation dose associated with PCT is a central topic and has been a focus of interest for many researchers. Many studies have examined the effect of radiation dose reduction in PCT using different approaches. Reduction of tube current and tube voltage can be efficient and lead to a remarkable reduction of effective radiation dose while preserving acceptable image quality. The use of novel noise reduction techniques such as iterative reconstruction or spatiotemporal smoothing can produce sufficient image quality from low-dose perfusion protocols. Reduction of sampling frequency of perfusion images has only little potential to reduce radiation dose. In the present article we aimed to summarize the available data on radiation dose reduction in PCT imaging of the brain.

Effects of radiation dose reduction in Volume Perfusion CT imaging of acute ischemic stroke.

PURPOSE: To examine the influence of radiation dose reduction on image quality and sensitivity of Volume Perfusion CT (VPCT) maps regarding the detection of ischemic brain lesions. METHODS AND MATERIALS: VPCT data of 20 patients with suspected ischemic stroke acquired at 80 kV and 180 mAs were included. Using realistic reduced-dose simulation, low-dose VPCT datasets with 144 mAs, 108 mAs, 72 mAs and 36 mAs (80 %, 60 %, 40 % and 20 % of the original levels) were generated, resulting in a total of 100 datasets. Perfusion maps were created and signal-to-noise-ratio (SNR) measurements were performed. Qualitative analyses were conducted by two blinded readers, who also assessed the presence/absence of ischemic lesions and scored CBV and CBF maps using a modified ASPECTS-score. RESULTS: SNR of all low-dose datasets were significantly lower than those of the original datasets (p < .05). All datasets down to 72 mAs (40 %) yielded sufficient image quality and high sensitivity with excellent inter-observer-agreements, whereas 36 mAs datasets (20 %) yielded poor image quality in 15 % of the cases with lower sensitivity and inter-observer-agreements. CONCLUSION: Low-dose VPCT using decreased tube currents down to 72 mAs (40 % of original radiation dose) produces sufficient perfusion maps for the detection of ischemic brain lesions. KEY POINTS: • Perfusion CT is highly accurate for the detection of ischemic brain lesions • Perfusion CT results in high radiation exposure, therefore low-dose protocols are required • Reduction of tube current down to 72 mAs produces sufficient perfusion maps.