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Purpose: The aim of this study was to assess the atherosclerotic plaques in a large asymptomatic population stratified based on age and sex.Methods: [18F]-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT of 100 men and 100 women, divided in four age groups were examined to assess FDG-accumulating active, calcified inactive and mixed atherosclerotic plaques in eight defined vessel segments.Results: There was a high correlation between the total number of cardiovascular risk factors and the number of FDG-accumulating active plaques as well as the number of calcified inactive plaques. There was a significant difference in the number of plaques between all age-groups except for active plaques in age groups 60-70 and 80-90 years.Conclusions: There is a correlation between the number of cardiovascular risk factors and the number of FDG-accumulating atherosclerotic lesions in this patient material. Statin-treatment was associated with significantly lower numbers of active plaques. [ABSTRACT FROM AUTHOR]

Purpose: Application of standardised and automated assessments of head computed tomography (CT) for neuroprognostication after out-of-hospital cardiac arrest., Methods: Prospective, international, multicentre, observational study within the Targeted Hypothermia versus Targeted Normothermia after out-of-hospital cardiac arrest (TTM2) trial. Routine CTs from adult unconscious patients obtained > 48 h ≤ 7 days post-arrest were assessed qualitatively and quantitatively by seven international raters blinded to clinical information using a pre-published protocol. Grey-white-matter ratio (GWR) was calculated from four (GWR-4) and eight (GWR-8) regions of interest manually placed at the basal ganglia level. Additionally, GWR was obtained using an automated atlas-based approach. Prognostic accuracies for prediction of poor functional outcome (modified Rankin Scale 4-6) for the qualitative assessment and for the pre-defined GWR cutoff < 1.10 were calculated., Results: 140 unconscious patients were included; median age was 68 years (interquartile range [IQR] 59-76), 76% were male, and 75% had poor outcome. Standardised qualitative assessment and all GWR models predicted poor outcome with 100% specificity (95% confidence interval [CI] 90-100). Sensitivity in median was 37% for the standardised qualitative assessment, 39% for GWR-8, 30% for GWR-4 and 41% for automated GWR. GWR-8 was superior to GWR-4 regarding prognostic accuracies, intra- and interrater agreement. Overall prognostic accuracy for automated GWR (area under the curve [AUC] 0.84, 95% CI 0.77-0.91) did not significantly differ from manually obtained GWR., Conclusion: Standardised qualitative and quantitative assessments of CT are reliable and feasible methods to predict poor functional outcome after cardiac arrest. Automated GWR has the potential to make CT quantification for neuroprognostication accessible to all centres treating cardiac arrest patients., (© 2024. The Author(s).)

Introduction: Several studies have addressed technical aspects of endovascular thrombectomy (EVT), but it is not well known how procedural factors contribute to technical success in routine healthcare. The aim was to explore factors associated with technically successful EVT on nationwide scale., Methods: We did an observational register-based study assessing factors associated with technical success off anterior circulation EVT in Sweden. The main outcome was successful recanalization defined as modified treatment in cerebral ischemia score 2b-3. The association between baseline and treatment variables and successful recanalization were explored using Chi-square(d) test and univariable logistic regression. Multivariable logistic regression was used to define predictors of successful recanalization., Results: The study included 3211 patients treated during 2015 to 2020. Successful recanalization was achieved in 83.1% (2667) with a gradual improvement in technical outcome over the period. After adjustment for age and occlusion location, thet use of general anesthesia, balloon guide catheter (BGC) and an operator with an overall success rate of >85% were independent predictors of successful recanalization. An overall operator success rate of <80% or 80-85%, and an annual center volume lower than 50 were predicitors of recanalization failure., Conclusion: This study illustrates factors associated with procedural success in endovascular thrombectomy on a nationwide scale including the use of general anesthesia, BGC, annual center volumes >50 cases per year and the overall success rate of the individual operator. It highlights the potential benefit of systematic performance measurements, benchmarking, and continuous training to bring all centers and operators to the highest level of performance., Competing Interests: Declaration of conflicting interestsThe authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: JW is a founder and shareholder of Uman Sense AB and has received speaker honoraria from Siemens Healthineers, BALT group and Medtronic Inc. TA is a consultant for Anaconda, Cerenovus, Optimize Neurovascular and Rapid Medical, and a shareholder in Ceroflo. TU received honoraria from ASTRA ZENECA for an expert group assignment, and speaker honoraria from Siemens Healthineers.

Objective: To systematically evaluate the ability of the CINA® LVO software to detect large vessel occlusions eligible for mechanical thrombectomy on CTA using conventional neuroradiological assessment as gold standard., Methods: Retrospectively, two hundred consecutive patients referred for a brain CTA and two hundred patients that had been subject for endovascular thrombectomy, with an accessible preceding CTA, were assessed for large vessel occlusions (LVO) using the CINA® LVO software. The patients were sub-grouped by occlusion site. The original radiology report was used as ground truth and cases with disagreement were reassessed. Two-by-two tables were created and measures for LVO detection were calculated., Results: A total of four-hundred patients were included; 221 LVOs were present in 215 patients (54 %). The overall specificity was high for LVOs in the anterior circulation (93 %). The overall sensitivity for LVOs in the anterior circulation was 54 % with the highest sensitivity for the M1 segment of the middle cerebral artery (87 %) and T-type internal carotid occlusions (84 %). The sensitivity was low for occlusions in the M2 segment of the middle cerebral artery (13 % and 0 % for proximal and distal M2 occlusions respectively) and in posterior circulation occlusions (0 %, not included in the intended use of the software)., Conclusions: LVO detection sensitivity for the CINA® LVO software differs largely depending on the location of the occlusion, with low sensitivity for detection of some LVOs potentially eligible for mechanical thrombectomy. Further development of the software to increase sensitivity to all LVO locations would increase the clinical usefulness., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

Introduction: Radiological assessment is necessary to diagnose spontaneous intracerebral hemorrhage (ICH) and traumatic brain injury intracranial hemorrhage (TBI-bleed). Artificial intelligence (AI) deep learning tools provide a means for decision support. This study evaluates the hemorrhage segmentations produced from three-dimensional deep learning AI model that was developed using non-contrast computed tomography (CT) imaging data external to the current study., Methods: Non-contrast CT imaging data from 1263 patients were accessed across seven data sources (referred to as sites) in Norway and Sweden. Patients were included based on ICH, TBI-bleed, or mild TBI diagnosis. Initial non-contrast CT images were available for all participants. Hemorrhage location frequency maps were generated. The number of estimated haematoma clusters was correlated with the total haematoma volume. Ground truth expert annotations were available for one ICH site; hence, a comparison was made with the estimated haematoma volumes. Segmentation volume estimates were used in a receiver operator characteristics (ROC) analysis for all samples (i.e., bleed detected) and then specifically for one site with few TBI-bleed cases., Results: The hemorrhage frequency maps showed spatial patterns of estimated lesions consistent with ICH or TBI-bleed presentations. There was a positive correlation between the estimated number of clusters and total haematoma volume for each site (correlation range: 0.45-0.74; each p -value < 0.01) and evidence of ICH between-site differences. Relative to hand-drawn annotations for one ICH site, the VIOLA-AI segmentation mask achieved a median Dice Similarity Coefficient of 0.82 (interquartile range: 0.78 and 0.83), resulting in a small overestimate in the haematoma volume by a median of 0.47 mL (interquartile range: 0.04 and 1.75 mL). The bleed detection ROC analysis for the whole sample gave a high area-under-the-curve (AUC) of 0.92 (with sensitivity and specificity of 83.28% and 95.41%); however, when considering only the mild head injury site, the TBI-bleed detection gave an AUC of 0.70., Discussion: An open-source segmentation tool was used to visualize hemorrhage locations across multiple data sources and revealed quantitative hemorrhage site differences. The automated total hemorrhage volume estimate correlated with a per-participant hemorrhage cluster count. ROC results were moderate-to-high. The VIOLA-AI tool had promising results and might be useful for various types of intracranial hemorrhage., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 MacIntosh, Liu, Schellhorn, Beyer, Groote, Morberg, Poulin, Selseth, Bakke, Naqvi, Hillal, Ullberg, Wassélius, Rønning, Selnes, Kristoffersen, Emblem, Skogen, Sandset and Bjørnerud.)

Purpose: Reduction in iodinated contrast medium (CM) dose is highly motivated. Our aim was to evaluate if a 50% reduction of CM, while preserving image quality, is possible in brain CT angiography (CTA) using virtual monoenergetic images (VMI) on spectral CT. As a secondary aim, we evaluated if VMI can salvage examinations with suboptimal CM timing., Methods: Consecutive patients older than 18 years without intracranial stenosis/occlusion were included. Three imaging protocols were used: group 1, full CM dose; group 2, 50% CM dose suboptimal timing; and group 3, 50% CM dose optimized timing. Attenuation, noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were measured in the internal carotid artery, M2 segment of the middle cerebral artery, and white matter for conventional images (CI) and VMI (40-200 keV). Qualitative image quality for CI and VMI (50 and 60 keV) was rated by 4 experienced reviewers., Results: Qualitatively and quantitatively, VMI (40-60 keV) improved image quality within each group. Significantly higher attenuation and CNR was found for group 3 VMI 40-50 keV, with unchanged SNR, compared to group 1 CI. Group 3 VMI 50 keV also received significantly higher rating scores than group 1 CI. Group 2 VMI (40-50 keV) had significantly higher CNR compared to group 3 CI, but the subjective image quality was similar., Conclusion: VMI of 50 keV with 50% CM dose increases qualitative and quantitative image quality over CI with full CM dose. Using VMI reduces non-diagnostic examinations and may salvage CTA examinations deemed non-diagnostic due to suboptimal timing., (© 2023. The Author(s).)

Background: Perforator aneurysms of the basilar artery (PABA) are rare causes of subarachnoid haemorrhage (SAH) and challenging to diagnose. We present two cases of SAH caused by PABA diagnosed by cone beam computed tomography angiography (CBCTA) and a novel non-invasive method - 7T magnetic resonance imaging (7T MRI)., Methods: Two patients with SAH, diagnosed with PABA, were imaged on day 9 and 13 after onset, respectively, with CBCTA and 7T MR angiography (MRA) performed on the day after and at follow-up at 3 months., Results: All four 7T MRI examinations in the two patients were technically successful with fully diagnostic images. No endovascular treatment was performed and control with 7T MRA at 3 months showed no remaining aneurysms., Conclusion: PABA can be imaged with 7T MRI - a novel non-invasive method, allowing non-invasive follow-up to monitor this rare cause of SAH.

Background: Endovascular thrombectomy (EVT) for ischemic stroke (IS) beyond 6 hours has been proven effective in randomized controlled trials. We present data on implementation and outcomes for EVT beyond 6 hours in Sweden., Methods: We included all cases of anterior circulation IS caused by occlusion of the intracranial carotid artery, and the M1 or M2 segment of the middle cerebral artery, registered in two nationwide quality registers for stroke in 2015-2020. Three groups were defined from onset-to-groin-puncture (OTG) time: early window (<6 hours), late window (6-24 hours) known onset, late window last seen well (LSW). Favorable outcome (modified Rankin Scale (mRS) 0-2) and all-cause mortality at 90 days were the main outcomes, and symptomatic intracerebral hemorrhage (sICH) was the safety outcome., Results: Late window EVT increased from 0.3% of all IS in 2015 to 1.8% in 2020, and from 17.4% of all anterior circulation EVTs in 2015 to 32.9% in 2020. Of 2199 patients, 76.9% (n=1690) were early window EVTs and 23.1% late window EVTs (n=509; 141 known onset, 368 LSW). Median age was 73 years, and 46.2% were female, with no differences between groups. Favorable outcome did not differ between groups (early window 42.4%, late window known onset 38.9%, late window LSW 37.3% (p=0.737)) and remained similar when adjusted for baseline differences. sICH rates did not differ (early window 4.0%, late window known onset 2.1%, late window LSW 4.9% (p=0.413))., Conclusion: Late window EVTs have increased substantially over time, and currently account for one third of anterior circulation treatments. Early and late window patients had similar outcomes., Competing Interests: Competing interests: BN has received honoraria from AstraZeneca for serving on the DSMB for the THALES trial. TU has received honoraria from AstraZeneca for an expert group assignment. JW is a shareholder for UmanSense AB. FA has received grants from Stryker and Cerenovus. MvE receive honoraria from the Committee for Clinical Therapy Research. TA received honoraria from Anaconda, Cerenovus, Stryker. TA also received honoraria for serving on the DSMB for the Excellent registry, SPERO and Solonda studies, and is a shareholder on Rapid Medical and Ceroflo. PW is a clinical adjudication member in Portico 1 and Portico IDE phase IV studies supported from Abbott., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Acute ischemic lesions are challenging to detect by conventional computed tomography (CT). Virtual monoenergetic images may improve detection rates by increased tissue contrast., Purpose: To compare the ability to detect ischemic lesions of virtual monoenergetic with conventional images in patients with acute stroke., Material and Methods: We included consecutive patients at our center that underwent brain CT in a spectral scanner for suspicion of acute stroke, onset <12 h, with or without (negative controls) a confirmed cortical ischemic lesion in the initial scan or a follow-up CT or magnetic resonance imaging. Attenuation was measured in predefined areas in ischemic gray (guided by follow-up exams), normal gray, and white matter in conventional images and retrieved in spectral diagrams for the same locations in monoenergetic series at 40-200 keV. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Visual assessment of diagnostic measures was performed by independent review by two neuroradiologists blinded to reconstruction details., Results: In total, 29 patients were included (January 2018 to July 2019). SNR was higher in virtual monoenergetic compared to conventional images, significantly at 60-150 keV. CNR between ischemic gray and normal white matter was higher in monoenergetic images at 40-70 keV compared to conventional images. Virtual monoenergetic images received higher scores in overall image quality. The sensitivity for diagnosing acute ischemia was 93% and 97%, respectively, for the reviewers, compared to 55% of the original report based on conventional images., Conclusion: Virtual monoenergetic reconstructions of spectral CIs may improve image quality and diagnostic ability in stroke assessment.

Purpose: Hematoma volume is the strongest predictor of patient outcome after intracerebral hemorrhage (ICH). The aim of this study was to validate novel fully automated software for quantification of ICH volume on non-contrast computed tomography (CT)., Methods: The population was defined from the Swedish Stroke Register (RS) and included all patients with an ICH diagnosis during 2016-2019 in Region Skåne. Hemorrhage volume on their initial head CT was measured using ABC/2 and manual segmentation (Sectra IDS7 volume measurement tool) and the automated volume quantification tool (qER-NCCT) by Qure.ai. The first 500 were examined by two independent readers., Results: A total of 1649 ICH patients were included. The qER-NCCT had 97% sensitivity in identifying ICH. In total, there was excellent agreement between volumetric measurements of ICH volumes by qER-NCCT and manual segmentation by interclass correlation (ICC = 0.96), and good agreement (ICC = 0.86) between qER-NCCT and ABC/2 method. The qER-NCCT showed volume underestimation, mainly in large (> 30 ml) heterogenous hemorrhages. Interrater agreement by (ICC) was 0.996 (95% CI: 0.99-1.00) for manual segmentation., Conclusion: Our study showed excellent agreement in volume quantification between the fully automated software qER-NCCT and manual segmentation of ICH on NCCT. The qER-NCCT would be an important additive tool by aiding in early diagnostics and prognostication for patients with ICH and in provide volumetry on a population-wide level. Further refinement of the software should address the underestimation of ICH volume seen in a portion of large, heterogenous, irregularly shaped ICHs., (© 2022. The Author(s).)

Purpose: Conventional computed tomography (CT) images are severely affected by metal artifacts in patients with intracranial coils. Monoenergetic images have been suggested to reduce metal artifacts.The aim of this study was to assess metal artifacts in virtual monoenergetic images (VMIs) reconstructed from spectral brain CT., Methods: Thirty-two consecutive patients with intracranial coils examined by spectral non contrast brain CT (NCCT) at our center between November 2017 and April 2019 were included. Attenuation and standard deviations were measured in regions of interest (ROIs) at predefined areas in artifact-free and artifact-affected areas. Measurements were performed in conventional polyenergetic images (CIs) and the corresponding data for VMIs were retrieved through spectral diagrams for the each ROI. Subjective analysis was performed by visual grading of CIs and specific VMIs by two neuroradiologists, independently., Results: In artefact-affected image areas distal from the metal objects, the attenuation values decreased with higher energy level VMIs. The same effect was not seen for artefact-affected image areas close to the metal.Subjective rating of the artefact severity was significantly better in VMIs at 50 keV for one of the two reviewers compared to the CIs. Overall image quality and tissue differentiation scores were significantly higher for both reviewers in VMIs at 60 and 70 keV compared to CIs., Conclusion: Our quantitative and qualitative image analysis shown that there is a small significant reduction of intracranial coils artifacts severity by all monoenergetic reconstructions from 50 to 200 keV with preserved or increased overall subjective image quality compared to conventional images., Competing Interests: None of the authors have any conflicts of interests related to the study. JW is a founder and shareholder of Uman Sense AB and has received speaker honoraria from Siemens Healthineers, BALT group and Medtronic Inc., (© 2023 The Authors.)

Background: Endovascular thrombectomy (EVT) is standard of care for anterior circulation acute ischemic stroke (AIS) caused by large vessel occlusion (LVO), but data on nationwide performance in routine healthcare are sparse. The study aims were to describe EVT patients with LVO AIS, analyze mortality and functional outcome, and compare results with randomized controlled trials (RCTs)., Methods: Data from the Riksstroke and the Swedish Endovascular Treatment of Acute Stroke Registry (RSEVAS) on pre-stroke independent patients, with LVO AIS in 2017-2019, defined as occlusion of the intracranial internal carotid artery, or the M1 or M2 segments of the middle cerebral artery, and groin puncture <6 h of onset, were compared to aggregated HERMES collaboration RCT data. We assessed 90-day survival and function, defined by the modified Rankin Scale. Specific analyzes were stratified by occlusion location., Results: In all, 1011/2560 of RSEVAS patients matched RCT inclusion criteria. Compared with RCT data, patients were older (73 vs. 68), fewer received intravenous thrombolysis (63.1% vs. 83%), and M2 occlusions were more common (24.5% vs. 8%). 90-day survival in RSEVAS was 85.3%, 42.8% achieved good outcome and 5% had symptomatic intracerebral hemorrhage (sICH). Corresponding outcomes in RCT data were 84.7% survival, 46% good outcome, and 4.4% sICH. Functional outcome was most favorable following M2 occlusions., Conclusions: EVT patients from our large real-world national dataset differed from RCT patients in several baseline factors including distribution of vascular occlusion site. However, the overall outcome of EVT in our Swedish cohort appeared to well match the pivotal trial findings.

Intracerebral hemorrhage (ICH) accounts for 10-20% of all strokes worldwide and is associated with serious outcomes, including a 30-day mortality rate of up to 40%. Neuroimaging is pivotal in diagnosing ICH as early detection and determination of underlying cause, and risk for expansion/rebleeding is essential in providing the correct treatment. Non-contrast computed tomography (NCCT) is the most used modality for detection of ICH, identification of prognostic markers and measurements of hematoma volume, all of which are of major importance to predict outcome. The strongest predictors of 30-day mortality and functional outcome for ICH patients are baseline hematoma volume and hematoma expansion. Even so, exact hematoma measurement is rare in clinical routine practice, primarily due to a lack of tools available for fast, effective, and reliable volumetric tools. In this educational review, we discuss neuroimaging findings for ICH from NCCT images, and their prognostic value, as well as the use of semi-automatic and fully automated hematoma volumetric methods and assessment of hematoma expansion in prognostic studies., (© 2022. The Author(s).)

Background: Chronic subdural hematoma (cSDH) is one of the most common neurosurgical disorders and the incidence is rising. The routine treatment is neurosurgical hematoma evacuation, which is associated with recurrence rates up to 10-25%. In recent years, endovascular embolization of the middle meningeal artery (eMMA) has garnered much attention due to recurrence rates as low as < 5%. Several randomized controlled trials are planned or ongoing. In most of these trials, conventional neurosurgical treatment with or without adjunctive endovascular embolization is compared. The proposed trial aims to conduct a head-to-head comparison between neurosurgical and endovascular treatment as stand-alone treatments., Methods: The trial is academically driven and funded within existing public healthcare systems and infrastructure. Patients with uni- or bilateral cSDH, presenting with mild-to moderate symptoms, and admitted to neurosurgery on clinical grounds will be offered participation. Subjects are randomized 1:1 between conventional neurosurgical treatment (control) and endovascular embolization of the middle meningeal artery (intervention). Primary endpoint is reoperation due to clinically and/or radiologically significant recurrence within 3 months. Secondary endpoints include safety, technical success rate, neurological disability, and quality of life., Discussion: There are mounting retrospective data suggesting eMMA, as sole treatment or as an adjunctive to neurosurgery for cSDH, is safe and effective with a reoperation rate lower than neurosurgical hematoma evacuation alone. If randomized controlled trials confirm these findings, there is a potential for a paradigm shift in the treatment of cSDH where a minimally invasive procedure can replace open surgery in a large and oftentimes old and fragile patient cohort., Trial Registration: ClinicalTrials.gov, ClinicalTrials.gov Identifier NCT05267184 . Registered March 4, 2022., (© 2022. The Author(s).)

Purpose: We present the first nationwide study on endovascular therapy for basilar artery occlusion (BAO) from early hospital management to 3-month outcome., Methods: Data were collected on all acute ischaemic stroke patients registered 2016-2019 in the two national quality registers for stroke care and endovascular therapy (EVT), receiving EVT for BAO and subclassified into proximal, middle and distal., Results: In all, 251 patients were included: 69 proximal, 73 middle and 109 distal BAO. Patients with proximal BAO were younger (66, middle 71, distal 76, p < 0.0001), less often female (27.5%, middle 47.9%, distal 47.7%, p = 0.015), more often smokers (28.6%, middle 20.3%, distal 11.5%, p < 0.0001), and fewer had atrial fibrillation (13.2%, middle 24.7%, distal 48.6%, p < 0.0001). Level of consciousness and NIHSS score did not differ by BAO subtype and 52.2% were alert on admission. Time from groin puncture to revascularization was significantly longer in patients with proximal BAO (71, middle 46, distal 42 min, p < 0.0001), and angioplasty and/or stenting was more often performed in patients with proximal (43.4%) and middle (27.4%) than distal (6.4%) BAO (p < 0.0001). Cumulative 90-day mortality was 38.6% (proximal 50.7%, middle 32.9%, distal 34.9%, p = 0.02). Older and pre-stroke dependent patients had higher mortality, as did patients in whom angioplasty/stenting was performed., Conclusion: We confirm a serious outcome in BAO despite endovascular therapies, and demonstrate important differences relating to occlusion location in baseline characteristics, procedural time, therapeutic measures and outcome. Further in-depth analyses of factors affecting outcome in BAO are warranted., (© 2021. The Author(s).)

Histology is a long standing and well-established gold standard for pathological characterizations. In recent years however, synchrotron radiation-based micro-computed tomography (SRμCT) has become a tool for extending the imaging of two-dimensional thin sections into three-dimensional imaging of tissue blocks, enabling so-called virtual histology with arbitrary clipping planes, volumetric rendering and automatic segmentation. In this study, we present a thorough characterization of human carotid plaques after endarterectomy of patients with stroke or transient ischemic attack (TIA), investigating several different pathologic structures using both SRμCT and histology. Phase-contrast SRμCT was performed with two different magnifications (voxel sizes 6.5 μm and 0.65 μm, respectively), and histology was performed with multiple different stainings (Alpha-actin, Glycophorin A, von Kossa, Movat, CD68). The 0.65 μm high-resolution SRμCT was performed on selected areas with plaque typical relevant morphology, identified on the 6.5 μm low-resolution SRμCT. The tomography datasets were reconstructed with additional 3D volume rendering and compared to histology. In total, nine different regions with typical pathologic structures were identified and imaged with high-resolution SRμCT. The results show many characteristics typical for advanced atherosclerotic plaques, clinically relevant, namely ruptures with thrombosis, neo-vascularization, inflammatory infiltrates in shoulder regions, lipid rich necrotic cores (LRNC), thin fibrous cap, calcifications, lumen irregularities, and changes in vessel wall structures such as the internal elastic membrane. This method's non-destructive nature renders details of micro-structures with an excellent visual likeness to histology, with the additional strength of multiplanar and 3D visualization and the possibility of multiple re-scans., Competing Interests: The authors have declared that no competing interests exist.

This review describes the evolution of endovascular treatment for acute ischemic stroke, current state of the art, and the challenges for the next decade. The rapid development of endovascular thrombectomy (EVT), from the first attempts into standard of care on a global scale, is one of the major achievements in modern medicine. It was possible thanks to the establishment of a scientific framework for patient selection, assessment of stroke severity and outcome, technical development by dedicated physicians and the MedTech industry, including noninvasive imaging for patient selection, and radiological outcome evaluation. A series of randomized controlled trials on EVT in addition to intravenous thrombolytics, with overwhelmingly positive results for anterior circulation stroke within 6 h of onset regardless of patient characteristics with a number needed to treat of less than 3 for any positive shift in outcome, paved the way for a rapid introduction of EVT into clinical practice. Within the "extended" time window of 6-24 h, the effect has been even greater for patients with salvageable brain tissue according to perfusion imaging with a number needed to treat below 2. Even so, EVT is only available for a small portion of stroke patients, and successfully recanalized EVT patients do not always achieve excellent functional outcome. The major challenges in the years to come include rapid prehospital detection of stroke symptoms, adequate clinical and radiological diagnosis of severe ischemic stroke cases, enabling effective recanalization by EVT in dedicated angiosuites, followed by personalized post-EVT stroke care., (© 2021 The Authors. Journal of Internal Medicine published by John Wiley & Sons Ltd on behalf of Association for Publication of The Journal of Internal Medicine.)

Purpose: The purpose of this study was to systematically search for long-term complications, including Nephrogenic Systemic Fibrosis (NSF), in patients who were previously administered the gadolinium-based contrast agent Gadofosveset at our institute., Materials and Methods: All patients who were administered Gadofosveset at our institute between 2006 and 2009 were identified in our Radiological Information System (RIS). Clinical data such as cause of death during follow-up, and dermatological or nephrological diseases were systematically searched for in electronic patient records (EPR)., Results: During 2006-2009, Gadofosveset was administered a total of 67 times to 62 patients. One patient was unavailable for follow-up. The remaining 61 patients were followed up for up to 14 (median 12) years based on RIS and EPR data. There were 13 deaths among the 61 patients, all assessed as unrelated to Gadofosveset administration. No dermatological or renal disease suggestive of NSF, or potentially related to Gadofosveset administration, was found. At the time of examination, six patients were diagnosed with various stages of renal insufficiency, three of whom were on hemodialysis. Another three patients were diagnosed with renal insufficiency during the follow-up period, but none of these diagnoses were suspected to be related to the administration of Gadofosveset., Conclusions: Based on the results of this retrospective safety analysis of up to 14 years following 1-2 exposures, we conclude that Gadofosveset in clinical practice is safe in the long-term., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Carotid atherosclerotic plaques with intraplaque hemorrhage (IPH) are associated with elevated stroke risk. IPH is predominantly imaged based on paramagnetic properties of the upstream hemoglobin degradation product methemoglobin. This is an explorative observational study to test the feasibility of a spoiled gradient echo based T2* weighted MRI sequence (3D MEDIC) for carotid plaque imaging, and to compare signs suggestive of the downstream degradation product hemosiderin on 3D MEDIC with signs of methemoglobin on a T1wBB sequence., Methods: Patients with recent TIA or stroke were selected based on the presence on non-calcified plaque components on CTA to promote an enriched prevalence of IPH in the material. Patients (n = 42) underwent 3T MRI with 3D MEDIC and 2D turbo spin echo T1w black blood (T1wBB). Images were independently evaluated by two neuroradiologists and Cohens Kappa was used for inter-reader agreement for each sequence., Results: The technical feasibility for 3D MEDIC, was 34/42 patients (81%). Non-calcified plaque components with susceptibility effect without simultaneous T1-shortening-a combination suggestive of hemosiderin, was seen in 13/34 of the plaques. An equally large group display elevated T1w signal in combination with signal loss on 3D MEDIC, a combination suggestive of both hemosiderin and methemoglobin. Cohen's kappa for inter-reader agreement was 0.64 (CI 0.345-0.925) for 3D MEDIC and 0.94 (CI 0.81-1.00) for T1wBB., Conclusions: 3D MEDIC shows signal loss, without elevated T1w signal on T1wBB, in non-calcified tissue in many plaques in this group of patients. If further studies, including histological verification, confirm that the 3D MEDIC susceptibility effect is indeed caused by hemosiderin, 3D MEDIC could aid in the detection of IPH, beyond elevation of T1w signal., (© 2021. The Author(s).)

Background and Aims: Histopathology is the gold standard for analysis of atherosclerotic plaques but has drawbacks due to the destructive nature of the method. Ex vivo MRI is a non-destructive method to image whole plaques. Our aim was to use quantitative high field ex vivo MRI to classify plaque components, with histology as gold standard., Methods: Surgically resected carotid plaques from 12 patients with recent TIA or stroke were imaged at 11.7 T MRI. Quantitative T1/T2* mapping sequences and qualitative T1/T2* gradient echo sequences with voxel size of 30 × 30 × 60 μm 3 were obtained prior to histological preparation, sectioning and staining for lipids, inflammation, hemorrhage, and fibrous tissue. Regions of interest (ROI) were selected based on the histological staining at multiple levels matched between histology and MRI. The MRI parameters of each ROI were then analyzed with quadratic discriminant analysis (QDA) for classification., Results: A total of 965 ROIs, at 70 levels matched between histology and MRI, were registered based on histological staining. In the nine plaques where three or more plaque components were possible to co-localize with MRI, the mean degree of misclassification by QDA was 16.5 %. One of the plaques contained mostly fibrous tissue and lipids and had no misclassifications, and two plaques mostly contained fibrous tissue. QDA generally showed good classification for fibrous tissue and lipids, whereas plaques with hemorrhage and inflammation had more misclassifications., Conclusion: 11.7 T ex vivo high field MRI shows good visual agreement with histology in carotid plaques. T1/T2* maps analyzed with QDA is a promising non-destructive method to classify plaque components, but with a higher degree of misclassifications in plaques with hemorrhage or inflammation., Competing Interests: The authors report no declarations of interest., (© 2021 The Author(s).)

Purpose: Onyx® embolization causes severe artifacts on subsequent CT-examinations, thereby seriously limiting the diagnostic quality.The purpose of this work was to compare the diagnostic quality of the tailored metal artifact reducing algorithms iMAR to standard reconstructions of CTA in patients treated with Onyx® embolization., Method: Twelve consecutive patients examined with Dual Energy CTA after Onyx® embolization were included. One standard image dataset without iMAR, and eight image datasets with different iMAR algorithms were reconstructed. Mean attenuation and noise were measured in the aorta or iliac arteries close to the Onyx® glue-cast and compared to the reference level in the diaphragmatic aorta. Mean attenuation and noise were also measured in the psoas muscle close to the Onyx®-glue and compared to the reference level in the psoas muscle at the level of the diaphragm.Subjective image quality and severity of artifacts was assessed by two experienced interventional radiologists blinded to reconstruction details., Results: All iMAR reconstructions had less distortion of the attenuation than the standard reconstructions and were also rated significantly better than the standard reconstructions by both interventional radiologists., Conclusion: The iMAR algorithms can significantly reduce metal artifacts and improve the diagnostic quality in CTA in patients treated with Onyx® embolization, in many cases restoring non-diagnostic examinations to acceptable diagnostic quality., Competing Interests: The authors report no declarations of interest., (© 2020 The Author(s).)

Background: Magnetic resonance imaging (MRI) serves as a cornerstone in defining stroke phenotype and etiological subtype through examination of ischemic stroke lesion appearance and is therefore an essential tool in linking genetic traits and stroke. Building on baseline MRI examinations from the centralized and structured radiological assessments of ischemic stroke patients in the Stroke Genetics Network, the results of the MRI-Genetics Interface Exploration (MRI-GENIE) study are described in this work. Methods: The MRI-GENIE study included patients with symptoms caused by ischemic stroke ( N = 3,301) from 12 international centers. We established and used a structured reporting protocol for all assessments. Two neuroradiologists, using a blinded evaluation protocol, independently reviewed the baseline diffusion-weighted images (DWIs) and magnetic resonance angiography images to determine acute lesion and vascular occlusion characteristics. Results: In this systematic multicenter radiological analysis of clinical MRI from 3,301 acute ischemic stroke patients according to a structured prespecified protocol, we identified that anterior circulation infarcts were most prevalent (67.4%), that infarcts in the middle cerebral artery (MCA) territory were the most common, and that the majority of large artery occlusions 0 to 48 h from ictus were in the MCA territory. Multiple acute lesions in one or several vascular territories were common (11%). Of 2,238 patients with unilateral DWI lesions, 52.6% had left-sided infarct lateralization ( P = 0.013 for χ 2 test). Conclusions: This large-scale analysis of a multicenter MRI-based cohort of AIS patients presents a unique imaging framework facilitating the relationship between imaging and genetics for advancing the knowledge of genetic traits linked to ischemic stroke., (Copyright © 2020 Drake, Frid, Hansen, Wu, Giese, Schirmer, Donahue, Cloonan, Irie, Bouts, McIntosh, Mocking, Dalca, Sridharan, Xu, Giralt-Steinhauer, Holmegaard, Jood, Roquer, Cole, McArdle, Broderick, Jiménez-Conde, Jern, Kissela, Kleindorfer, Lemmens, Meschia, Rundek, Sacco, Schmidt, Sharma, Slowik, Thijs, Woo, Worrall, Kittner, Mitchell, Rosand, Golland, Lindgren, Rost and Wassélius.)

Purpose: Reports from 3-T vessel wall MRI imaging have shown contrast enhancement following thrombectomy for acute stroke, suggesting potential intimal damage. Comparisons have shown higher SNR and more lesions detected by vessel wall imaging when using 7 T compared with 3 T. The aim of this study was to investigate the vessel walls after stent retriever thrombectomy using high-resolution vessel wall imaging at 7 T., Methods: Seven patients with acute stroke caused by occlusion of the distal internal carotid artery (T-occlusion), or proximal medial cerebral artery, and treated by stent retriever thrombectomy with complete recanalization were included and examined by 7-T MRI within 2 days. The MRI protocol included a high-resolution black blood sequence with prospective motion correction (iMOCO), acquired before and after contrast injection. Flow measurements were performed in the treated and untreated M1 segments., Results: All subjects completed the MRI examination. Image quality was independently rated as excellent by two neuroradiologists for all cases, and the level of motion artifacts did not impair diagnostic quality, despite severe motion in some cases. Contrast enhancement correlated with the deployment location of the stent retrievers. Flow data showed complete restoration of flow after treatment., Conclusion: Vessel wall imaging with prospective motion correction can be performed in patients following thrombectomy with excellent imaging quality at 7 T. We show that vessel wall contrast enhancement is the normal post-operative state and corresponds to the deployment location of the stent retriever.

Background: Follow-up with computed tomographic angiography is recommended after endovascular aneurysm repair, exposing patients to significant levels of radiation and iodine contrast medium. Dual-energy computed tomography allows virtual noncontrast (VNC) images to be reconstructed from contrast-enhanced images using a software algorithm. If the VNC images are a good-enough approximation of true noncontrast (TNC) images, a reduction in radiation dose can be ensured through omitting a TNC scan., Purpose: To compare image quality of VNC images reconstructed from arterial phase and venous phase dual-energy computed tomographic angiography to TNC images and to assess which one is more suitable to replace TNC images., Methods: Sixty-three consecutive patients were examined using a dual-energy computed tomography as elective follow-up after endovascular aneurysm repair. The examination protocol included 1 unenhanced and 2 contrast-enhanced scans (80 kV/Sn140 kV) of the aorta. Virtual noncontrast data sets were reconstructed from the arterial (A-VNC) and venous (V-VNC) phase scans, respectively. Mean attenuation and image noise were measured for TNC, A-VNC, and V-VNC images within regions of interest at 2 levels in the aorta, the liver, retroperitoneal fat, and psoas muscle. Subjective image quality was assessed on a 4-point scale by 2 blinded readers., Results: The differences between A-VNC and TNC, and between A-VNC and V-VNC, were substantial aorta at the level of diaphragm and aorta at the level of renal arteries. The difference between V-VNC and TNC was, on the other hand, very small and not statistically significant for the renal artery aorta. For liver, fat, and muscle tissue, there were significant differences between both A-VNC and V-VNC compared with TNC, but findings were similar between A-VNC and V-VNC., Conclusions: Virtual noncontrast images based on venous-phase scans appear to be a more accurate representation of TNC scans than VNC images based on arterial-phase scans.

Background: Computed tomographic angiography (CTA) may require a non-contrast enhanced dataset for the diagnostic workup. By using dual-energy acquisition, it is possible to obtain a virtual non-contrast-enhanced (VNC) dataset, thereby possibly eliminating the non-contrast acquisition and reducing the radiation dose., Purpose: To compare image quality of VNC images reconstructed from arterial phase dual-energy CTA to true non-contrast (TNC) images, and to assess whether VNC images were of sufficient quality to replace TNC images., Material and Methods: Thirty consecutive patients with suspected abdominal aortic aneurysm, aortic dissection, or subacute control after EVAR/TEVAR were examined with dual-energy CT (DECT). The examination protocol included a single-energy TNC, DECT arterial phase (80 kV/Sn140 kV), and single-energy in venous phase of the aorta. A VNC dataset was obtained from the DE acquisition from arterial phase scans. Mean attenuation and image noise were measured within regions of interest at three levels in the aorta in TNC and VNC images. Comparison of the TNC and VNC images for artefacts was made side-by-side. Subjective evaluation included overall image quality on a 4-grade scale, and quantitative analysis of algorithm-induced artefacts by two experienced readers., Results: For all cases, the aortic attenuation was significantly higher at VNC than at TNC. Image noise measured quantitatively was also significantly higher at VNC than at TNC. Subjective image quality was lower for VNC (mean = 3.1 for VNC, 3.7 = for TNC) but there were no cases rated non-diagnostic., Conclusion: VNC images based on arterial phase CTA have significantly higher mean attenuation and higher noise levels compared to TNC.

Background High-quality non-invasive imaging of the deep venous system in the thorax is challenging, but nevertheless required for diagnosis of vascular pathology as well as for patient selection and preoperative planning for endovascular procedures. Purpose To compare the diagnostic quality of Gadofosveset-enhanced thoracic magnetic resonance venography, seven consecutive patients with suspected or known disease affecting the central thoracic veins were compared to seven consecutive magnetic resonance venography using conventional gadolinium-based contrast agents. Materials and methods Diagnostic capability, defined as the ability to assess vessel patency and pathologic conditions, for the major thoracic deep venous segments was assessed by two-independent readers. Both reviewers rated the overall subjective image quality on a four-graded scale, and inter-rater variability was analyzed using unweighted and weighted Cohen's kappa values. Results Diagnostic capability was generally considerably higher in the Gadofosveset group for all examined vessel segments. The overall images quality rating was significantly higher for the Gadofosveset group with a mean rating of 2.9 and 2.7 for the two-independent readers, compared to 1.2 and 1.0 for the control croup. Inter-rater variability showed less variability for the Gadofosveset group with a quadratic-weighted Cohen's Kappa value of 0.58 compared to 0.36 for the control group. Conclusion Our results show that Gadofosveset-enhanced magnetic resonance venography of the central thoracic veins is a reliable technique in clinical routine practice that results in diagnostic images, superior to conventional gadolinium-based contrast medium.

The treatment of choice of vein of Galen aneurysmal malformation (VGAM) involves endovascular procedures that can be difficult to perform in high-flow fistulas. We describe the use of rapid ventricular pacing (RVP), a well-known cardiologic technique, to safely treat a high-flow fistula in an infant with VGAM.

Purpose This study was performed to compare the diagnostic quality of Gadofosveset-enhanced magnetic resonance venography with Gadobutrol-enhanced magnetic resonance venography and computed tomography venography for the deep veins of the lower extremities in patients with iliocaval venous pathology. Materials and methods Diagnostic capability and image quality were assessed by two independent readers. Inter-reader variability was analyzed by unweighted and quadratic weighted Cohen's kappa values. Results The diagnostic capability was equal to or higher in the Gadofosveset group for all examined vessel segments compared with both control groups. The image quality score was significantly higher for the Gadofosveset group compared to both control groups. Inter-reader variability expressed by quadratic weighted Cohen's kappa value (k) showed less variability in the Gadofosveset group compared to the control groups. Conclusion Our results show that Gadofosveset-enhanced magnetic resonance venography is a reliable technique in clinical routine practice, with image quality superior to both Gadobutrol-enhanced magnetic resonance venography and computed tomography venography.

Background: Follow-up of endovascular aneurysm repair (EVAR) with life-long computed tomography angiography (CTA) surveillance exposes patients with impaired renal function to repeated risks of contrast medium-induced nephropathy (CIN)., Purpose: To retrospectively compare vascular attenuation, image noise, contrast-to-noise ratio (CNR), subjective image quality and effective radiation dose (mSv) for CTA with a 16-multirow detector CT (MDCT) equipment at 80 kVp after EVAR using a contrast medium (CM) dose that is half of that used at 120 kVp., Material and Methods: Forty patients with estimated glomerular filtration rate (eGFR) <45 mL/min underwent 80-kVp CTA with 160 mg I/kg, and 40 patients with eGFR ≥45 mL/min 120-kVp CTA with 320 mg I/kg (maximum dose weight, 80 kg). Arterial phase analysis included vascular attenuation, image noise and CNR, and calculated effective dose. Subjective image quality was assessed on a 4-point scale by two blinded readers at three different levels as well as overall., Results: Median values in the 80/120 kVp cohorts were: age, 74-75 years; body weight, 77/80 kg; BMI 24/27 kg/m(2); CM dose, 13/25 gram-iodine; gram-iodine/GFR ratio, 0.35/0.38; mean aortic attenuation, 313/326 HU; image noise, 26/32 HU; CNR 10-11; subjective image quality score, 3.0-3.5 (Reader 1) and 3.0-3.3 (Reader 2); number of non-diagnostic examinations, 0/1; and effective dose, 4.5/5.1 mSv. There was no statistically significant difference in aortic CNR and effective dose between the 80 and 120 kVp cohorts., Conclusion: 80 kVp 16-MDCT with halved CM dose tailored to body weight for CTA follow-up of EVAR may provide satisfactory diagnostic results compared to common standards and be beneficial for patients at risk of CIN, though the present CT equipment may limit the use of the method to patients below 90 kg or with a BMI below 35 kg/m(2)., (© The Foundation Acta Radiologica 2015.)

Objective: The aim of this study was to determine the potential of different high-Z elements to act as contrast media (CMs) alongside iodine (I) in dual-CM, dual-energy (DE) computed tomography examinations., Methods: Gadolinium (Gd), tantalum (Ta), wolfram (W), gold (Au), and bismuth (Bi) in addition to I were examined at all available kilovolt settings in a DE computed tomography scanner. Dual-energy ratios were calculated by dividing attenuation at low kilovolt by attenuation at high kilovolt. Dual-energy data sets were loaded into material decomposition software to evaluate separation of the elements from I., Results: The DE ratios of Ta, W, and Au ranged between 0.9 and 1.2, being considerably lower than I at 1.9 to 2.6. These elements were completely separated from I using material decomposition. Gadolinium and Bi were more similar to I at 1.4 to 1.9. However, separation was nearly complete for Bi and suboptimal for Gd., Conclusions: Tantalum, W, and Au are ideal candidates for dual-CM examinations, whereas Bi is a slightly weaker candidate.

Mesenteric vein thrombosis may induce intestinal ischemia and gangrene. In severe cases, it is necessary to restore venous outflow from the small intestine rapidly. We describe a severe case of mesenteric vein thrombosis that was resolved successfully by mechanical thrombectomy from a transjugular approach followed by selective simultaneous venous and arterial thrombolysis via the superior mesenteric vein and artery. In conclusion, the transjugular intrahepatic portosystemic approach was a feasible and safe access for mechanical thrombectomy and thrombolysis of the mesenteric vein in our patient., (Copyright © 2014 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this retrospective study was to systematically search for acute adverse reactions and long-term complications in all patients that had been administered gadofosveset at our hospital., Materials and Methods: We identified 67 gadofosveset administrations during 2006-2009 in 62 patients from 8 to 84years of age. Radiological information system (RIS) and clinical patient records were analyzed for suspected acute adverse reactions and long-term complications including nephrogenic systemic fibrosis (NSF). The gadofosveset doses ranged between 0.024 and 0.060mmol/kg bodyweight with a mean dose of 0.031-mmol/kg bodyweight. Follow-up time of the patients ranged from less than 1year up to 4years with a mean follow-up time of 2.1years., Results: No acute adverse events or technical failures related to the contrast medium were recorded in the RIS. No dermatological and nephrological diseases related to the gadofosveset administration were found in the clinical patient records. Four patients died during follow-up without any apparent relation to the gadofosveset exposure., Conclusions: Based on our clinical material we conclude that gadofosveset is safe for a mixed patient population with no acute adverse events or any indications of long-term complications during the follow-up time up to four years., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Cystatins are present in mammals, birds, fish, insects, plants, fungi and protozoa and constitute a large protein family, with most members sharing a cysteine protease inhibitory function. In humans 12 functional cystatins exist, forming three groups based on molecular organisation and distribution in the organism. The type 1 cystatins (A and B) are known as intracellular, type 2 cystatins (C, D, E/M, F, G, S, SN and SA) extracellular and type 3 cystatins (L- and H-kininogen) intravascular proteins. The present paper is focused on the human cystatins and especially those of type 2, which are directed (with signal peptides) for cellular export following translation. Results indicating existence of systems for significant internalisation of type 2 cystatins from the extracellular to intracellular compartments are reviewed. Data showing that human neuroblastoma cell lines generally secrete high levels, but also contain high amounts of cystatin C are presented. Culturing of these cells in medium containing cystatin C at concentrations found in body fluids resulted in increased intracellular cystatin C, as a result of an uptake process. At immunofluorescence cytochemistry a pronounced vesicular cystatin C staining was observed. The simplistic denotation of the type 2 cystatins as extracellular inhibitors is thus challenged, and possible biological functions of the internalised cystatins are discussed. To illustrate the special case of high cellular cystatin content seen in cells of patients with hereditary cystatin C amyloid angiopathy, expression vectors for wild-type and L68Q mutated cystatin C were used to transfect SK-N-BE(2) cells. Clones overexpressing the two variants showed increased secreted levels of cystatin C. Within the cells the L68Q variant appeared to mainly localise to the endoplasmic reticulum rather than to acidic vesicular organelles, indicating limitations in the transport out from the cell rather than increased uptake as explanation for the elevated cellular cystatin levels seen in hereditary cystatin C amyloid angiopathy., (Copyright © 2010 Elsevier Masson SAS. All rights reserved.)

Unlabelled: Graft infection is a serious complication to vascular surgery. The aim of this study was to assess (18)F-FDG uptake in vascular grafts in patients with or without symptoms of graft infection., Methods: In all 2,045 patients examined by PET/CT at our clinic, 16 patients with synthetic aortic grafts were identified and reevaluated for (18)F-FDG accumulation. Clinical and biochemical data were obtained from patient records., Results: High (18)F-FDG uptake was found in 10 of 12 grafts in the patients who underwent open surgery and in 1 of 4 grafts in patients who underwent endovascular aneurysm repair. On the basis of biochemical and clinical data, it was concluded that 1 of the 16 patients had a graft infection at the time of investigation., Conclusion: (18)F-FDG uptake in vascular grafts was found in the vast majority of patients without graft infection. The risk of a false-positive diagnosis of graft infection by (18)F-FDG PET/CT is evident.

Background: As a secreted protein, cystatin C is assumed to play its role in the extracellular compartment, where it can inhibit virtually all cysteine proteases of families C1 (cathepsin B, L, S) and C13 (mammalian legumain-related proteases). Since many of its potential target enzymes in the eye reside in intracellular compartments, we sought evidence for a cellular uptake of the inhibitor in ocular tissues., Methods: Fluorescence-labeled human cystatin C was injected intravitreally into normal rat eyes. Ocular tissues were subsequently examined using ELISA, fluorescence microscopy, and immunohistochemistry. Cystatin C uptake was additionally studied in an in vitro retina model., Results: Cystatin C administered intravitreally in vivo is taken up into cells of the corneal endothelium and epithelium, the epithelial cells lining the ciliary processes, and into cells in the neuroretina (mostly ganglion cells) and the retinal pigment epithelium. The uptake is demonstrable also in vitro and was, in the neuroretina, found to be a high-affinity system, inhibited by cooling the specimens or by adding the microfilament polymerization inhibitor, cytochalasin D, to the medium., Conclusions: There is an active, temperature-dependent uptake system for cystatin C into several cell types in the cornea, ciliary body, and retina. The cell types that take up cystatin C are generally the same that contain endogenous cystatin C, suggesting that much or all cystatin C seen intracellularly in the normal eye may have been taken up from the surrounding extracellular space. The uptake indicates that the inhibitor may exert biological functions in intracellular compartments. It is also possible that this uptake system may regulate the extracellular levels of cystatin C in the eye.

Background: Optic nerve transection results in degeneration of axotomized retinal ganglion cells followed by the activation of resident microglial cells., Methods: An organotypic culture of neonatal rat retina was used to examine the temporal aspect of retinal ganglion cell death and microglial cell recruitment. Retinas were fixed at various times after explantation and prepared for immunohistochemistry and lectin staining., Results: Terminal deoxytransferase dUTP nick-end labeling (TUNEL) and immunohistochemistry for cleaved caspase-3 demonstrated a massive cascade of cell death in the ganglion cell layer (GCL) within hours after explantation. The rate of cell death in this layer was high and continued over a period of 48 h. In contrast, the rate of cell death was low in the outer nuclear layer (ONL) and apoptotic cells were evident after 6 days in vitro. Increases in the density of microglial cells in the GCL appeared to be recruited by proliferation within hours after explantation. In parallel, resident microglial cells also acquired an activated morphology as revealed by isolectin B(4) staining. Microglial cell activation in the GCL also included an upregulated expression for the lysosomal protein ED-1 and the cysteine protease inhibitor cystatin C. After 1 week of culture, immunolabeling for ED-1 demonstrated the presence of activated microglial cells also in the ONL., Conclusion: These data show rapid microglial cell recruitment and activation following the axotomy-induced cell death of differentiated ganglion cells. The processes of microglial cell activation and cell death are slower in the outer retina.

Purpose: Cystatin C is a mammalian cysteine protease inhibitor. This study describes the localization of cystatin C in the anterior segment of normal rat and mouse eyes. Cysteine proteases play an important role in protein degradation (e.g. of photoreceptor outer segments in the retinal pigment epithelium) and the balance between these proteases and their specific inhibitors is therefore of great interest., Methods: Cells containing cystatin C were identified by immunohistochemistry and quantified by ELISA. Messenger RNA levels were analysed by quantitative real-time polymerase chain reaction., Results: Cystatin C is present at biologically significant levels in the corneal epithelium, endothelium and stromal keratinocytes, lens epithelium, epithelial cells in the ciliary processes, aqueous humour and iris stromal cells. In the rat anterior segment, the highest cystatin C concentrations were found in the ciliary epithelium., Conclusions: Cystatin C is present in several cell types and is probably locally produced. The inhibitor is likely to be an important regulator of cysteine proteases in the retinal pigment epithelium, ciliary epithelium, aqueous humour, lens epithelium and in the corneal endothelium and epithelium.

Background: Cathepsin B is a mammalian cysteine protease. The enzyme has been suggested to participate in the patophysiological processes of keratoconus as well as in the corneal response to infectious agents. This study describes the localization of cathepsin B in the rat eye., Methods: Cathepsin B was identified in rat ocular tissues by Western blotting and immunohistochemistry. Cathepsin B mRNA levels were analyzed in the tissues by quantitative real-time cDNA amplification (QRT-PCR)., Results: Cathepsin B is present in the epithelium, in stromal cells and in the endothelium of the cornea. It is also present in the epithelium lining the ciliary processes, in occasional stromal cells in the iris, in the anterior subcapsular lens epithelium and in various cell types in the retina. At all locations cathepsin B is present in cytoplasmic granules, presumably lysosomes. QRT-PCR analysis detected cathepsin B mRNA in all these tissues in amounts correlating to the immunodetection results, suggesting that the enzyme detected is locally produced., Conclusions: Cathepsin B is present in several tissues and cell types throughout the rat eye. It is localized to cytoplasmic granules, presumably lysosomes. Our results suggest that it is probably also produced in the same cell types.

Cystatin F is a cysteine peptidase inhibitor recently discovered in haematopoietic cells by cDNA cloning. To further investigate the expression, distribution and properties of the native human inhibitor the promyeloid cell line U937 has been studied. The cells expressed relatively large quantities of cystatin F, which was found both secreted and intracellularly. The intracellular levels were unusually high for a secreted cystatin ( approximately 25% of the cystatin F in 2- or 4-day culture medium). By contrast, U937 cells contained only 3-4% of the related inhibitor, cystatin C. Cystatin F purified from lysates of U937 cells showed three major forms carrying two, one or no carbohydrate chains. Immunocytochemistry demonstrated a marked cytoplasmic cystatin F staining in a granular pattern. Double staining with a marker for endoplasmic reticulum revealed no colocalization for cystatin F. Analysis of the promoter region of the cystatin F gene (CST7) showed that it, like that of the cystatin C gene (CST3), is devoid of typical TATA- and CAAT-box elements. In contrast to the cystatin C promoter, it does not contain multiple Sp1 binding sites, but has a unique site for C/EBPalpha, possibly explaining the restricted expression of the cystatin F gene. Cells stimulated with all-trans retinoic acid to differentiate them towards a granulocytic pathway, showed a strong ( approximately 18-fold) down-regulation of intracellular cystatin F and almost abolished secreted levels of the inhibitor. Stimulation with tetradecanoyl phorbol acetate, causing monocytic differentiation, also resulted in down-regulation (two fold to threefold) of cystatin F expression, whereas the cystatin C expression was essentially unaltered in both experiments. The results suggest that cystatin F as an intracellular cysteine peptidase inhibitor with readily regulated expression, may be a candidate to control the cysteine peptidase activity known to be essential for antigen presentation in different blood cell lineages.

Müller cell morphology and degree of activation in adult retinal transplants have, to our knowledge, never been reported previously. We transplanted adult rabbit neuroretinal full-thickness sheets, prepared under strict control, to the subretinal space of adult rabbits. After surviving 6-174 days, eyes were examined in the light microscope, and grafts displaying the normal laminated morphology were labeled with antibodies against vimentin and glial fibrillary acidic protein (GFAP). Müller cells in the grafts displayed the normal vertical arrangement, from outer limiting membrane to vitread endfeet. They showed an initial degree of activation, evident by GFAP upregulation, which diminished with increasing survival times, and was absent in the oldest specimens. In the host retina, Müller cells in the transplant area became progressively more disorganized with increasing survival times, and their degree of activation increased. Our results suggests that adult full-thickness neuroretinal grafts are structurally stable, even in long-term specimens, and thrive in spite of their allogeneic environment. The gliotic change seen in the host retina covering the graft is identical to the one seen in earlier reported eyes receiving embryonic grafts, and is due to the merangiotic nature of the rabbit neuroretina., (Copyright 2002 Wiley-Liss, Inc.)

Purpose: Cystatin C is a mammalian cysteine protease inhibitor, synthesized in various amounts by many kinds of cells and appearing in most body fluids. There are reports that it may be synthesized in the mammalian retina and that a cysteine protease inhibitor may influence the degradation of photoreceptor outer segment proteins. In the current study cystatin C was identified, quantitated, and localized in mouse, rat, and human retinas., Methods: Enzyme-linked immunosorbent assay (ELISA), reverse transcription-polymerase chain reaction (RT-PCR), DNA sequencing, Western blot analysis, and immunohistochemistry have been used on mouse, rat, and human retinas (pigment epithelium included)., Results: Cystatin C is present in high concentrations in the normal adult rat retina, as it is throughout its postnatal development. Its concentration increases to a peak at the time when rat pups open their eyes and then remains at a high level. It is mainly localized to the pigment epithelium, but also to some few neurons of varying types in the inner retina. Cystatin C is similarly expressed in normal mouse and human retinas., Conclusions: Cystatin C was identified and the localization described in the retinas of rat, mouse, and human using several techniques. Cystatin C is known to efficiently inactivate certain cysteine proteases. One of them, cathepsin S, is present in the retinal pigment epithelium and affects the proteolytic processing by cathepsin D of diurnally shed photoreceptor outer segments. Hypothetically, it appears possible that retinal cystatin C, given its localization to the pigment epithelium and its ability to inhibit cathepsin S, could be involved in the regulation of photoreceptor degradation.

Acetylcholine is well established as the neurotransmitter of starburst amacrine cells in the vertebrate retina but their function is poorly understood. We compared the distribution of muscarinic m2 receptors in the rat retina with the localization of the starburst cell processes. mAChR2 immunoreactivity appeared in a central band in the inner plexiform layer, which did not co-localize with the processes of the cholinergic amacrine cells. We found co-labelling of VAChT and ChAT making it highly unlikely that there are undetected cholinergic neurons in rat retina. Most mAChR2 receptors were located far from the cholinergic neurons, suggesting that most of them are unlikely to be associated with conventional cholinergic synapses.