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•Benchmark Dataset for Clot Detection in Ischemic Stroke Vessel-Based Imaging: CODEC-IV.•Dataset with 159 vessel-enhanced CT patient datasets, annotated by experts.•Ongoing benchmarking resource to develop and assess automated clot detection tools.•Initiative towards improvement and standardization of clot detection algorithms. We present an annotated dataset for the purposes of creating a benchmark in Artificial Intelligence for automated clot detection. While there are commercial tools available for automated clot detection on computed tomographic (CT) angiographs, they have not been compared in a standardized manner whereby accuracy is reported on a publicly available benchmark dataset. Furthermore, there are known difficulties in automated clot detection – namely, cases where there is robust collateral flow, or residual flow and occlusions of the smaller vessels – and it is necessary to drive an initiative to overcome these challenges. Our dataset contains 159 multiphase CTA patient datasets, derived from CTP and annotated by expert stroke neurologists. In addition to images where the clot is marked, the expert neurologists have provided information about clot location, hemisphere and the degree of collateral flow. The data is available on request by researchers via an online form, and we will host a leaderboard where the results of clot detection algorithms on the dataset will be displayed. Participants are invited to submit an algorithm to us for evaluation using the evaluation tool, which is made available at together with the form at https://github.com/MBC-Neuroimaging/ClotDetectEval.

There is much uncertainty about the effects of early lowering of elevated blood pressure (BP) after acute intracerebral haemorrhage (ICH). Our aim was to assess the safety and efficiency of this treatment, as a run-in phase to a larger trial. Patients who had acute spontaneous ICH diagnosed by CT within 6 h of onset, elevated systolic BP (150–220 mm Hg), and no definite indication or contraindication to treatment were randomly assigned to early intensive lowering of BP (target systolic BP 140 mm Hg; n=203) or standard guideline-based management of BP (target systolic BP 180 mm Hg; n=201). The primary efficacy endpoint was proportional change in haematoma volume at 24 h; secondary efficacy outcomes included other measurements of haematoma volume. Safety and clinical outcomes were assessed for up to 90 days. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00226096. Baseline characteristics of patients were similar between groups, but mean haematoma volumes were smaller in the guideline group (12·7 mL, SD 11·6) than in the intensive group (14·2 mL, SD 14·5). From randomisation to 1 h, mean systolic BP was 153 mm Hg in the intensive group and 167 mm Hg in the guideline group (difference 13·3 mm Hg, 95% CI 8·9–17·6 mm Hg; p<0·0001); from 1 h to 24 h, BP was 146 mm Hg in the intensive group and 157 mm Hg in the guideline group (10·8 mm Hg, 95% CI 7·7–13·9 mm Hg; p<0·0001). Mean proportional haematoma growth was 36·3% in the guideline group and 13·7% in the intensive group (difference 22·6%, 95% CI 0·6–44·5%; p=0·04) at 24 h. After adjustment for initial haematoma volume and time from onset to CT, median haematoma growth differed between the groups with p=0·06; the absolute difference in volume between groups was 1·7 mL (95% CI −0·5 to 3·9, p=0·13). Relative risk of haematoma growth ≥33% or ≥12·5 mL was 36% lower (95% CI 0–59%, p=0·05) in the intensive group than in the guideline group. The absolute risk reduction was 8% (95% CI −1·0 to 17%, p=0·05). Intensive BP-lowering treatment did not alter the risks of adverse events or secondary clinical outcomes at 90 days. Early intensive BP-lowering treatment is clinically feasible, well tolerated, and seems to reduce haematoma growth in ICH. A large randomised trial is needed to define the effects on clinical outcomes across a broad range of patients with ICH. National Health and Medical Research Council of Australia.

Whether intravenous tissue plasminogen activator (alteplase) is effective beyond 3 h after onset of acute ischaemic stroke is unclear. We aimed to test whether alteplase given 3–6 h after stroke onset promotes reperfusion and attenuates infarct growth in patients who have a mismatch in perfusion-weighted MRI (PWI) and diffusion-weighted MRI (DWI). We prospectively and randomly assigned 101 patients to receive alteplase or placebo 3–6 h after onset of ischaemic stroke. PWI and DWI were done before and 3–5 days after therapy, with T2-weighted MRI at around day 90. The primary endpoint was infarct growth between baseline DWI and the day 90 T2 lesion in mismatch patients. Major secondary endpoints were reperfusion, good neurological outcome, and good functional outcome. Patients, caregivers, and investigators were unaware of treatment allocations. Primary analysis was per protocol. This study is registered with ClinicalTrials.gov, number NCT00238537. We randomly assigned 52 patients to alteplase and 49 patients to placebo. Mean age was 71·6 years, and median score on the National Institutes of Health stroke scale was 13. 85 of 99 (86%) patients had mismatch of PWI and DWI. The geometric mean infarct growth (exponential of the mean log of relative growth) was 1·24 with alteplase and 1·78 with placebo (ratio 0·69, 95% CI 0·38–1·28; Student's t test p=0·239); the median relative infarct growth was 1·18 with alteplase and 1·79 with placebo (ratio 0·66, 0·36–0·92; Wilcoxon's test p=0·054). Reperfusion was more common with alteplase than with placebo and was associated with less infarct growth (p=0·001), better neurological outcome (p<0·0001), and better functional outcome (p=0·010) than was no reperfusion. Alteplase was non-significantly associated with lower infarct growth and significantly associated with increased reperfusion in patients who had mismatch. Because reperfusion was associated with improved clinical outcomes, phase III trials beyond 3 h after treatment are warranted. National Health and Medical Research Council, Australia; National Stroke Foundation, Australia; Heart Foundation of Australia.

Diffusion-weighted imaging (DWI) is commonly used to assess irreversibly infarcted tissue but its accuracy is challenged by reports of diffusion lesion reversal (DLR). We investigated the frequency and implications for mismatch classification of DLR using imaging from the EPITHET (Echoplanar Imaging Thrombolytic Evaluation Trial) and DEFUSE (Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution) studies. In 119 patients (83 treated with IV tissue plasminogen activator), follow-up images were coregistered to acute diffusion images and the lesions manually outlined to their maximal visual extent in diffusion space. Diffusion lesion reversal was defined as voxels of acute diffusion lesion that corresponded to normal brain at follow-up (i.e., final infarct, leukoaraiosis, and cerebrospinal fluid (CSF) voxels were excluded from consideration). The appearance of DLR was visually checked for artifacts, the volume calculated, and the impact of adjusting baseline diffusion lesion volume for DLR volume on perfusion-diffusion mismatch analyzed. Median DLR volume reduced from 4.4 to 1.5 mL after excluding CSF/leukoaraiosis. Visual inspection verified 8/119 (6.7%) with true DLR, median volume 2.33 mL. Subtracting DLR from acute diffusion volume altered perfusion—diffusion mismatch (Tmax>6 seconds, ratio>1.2) in 3/119 (2.5%) patients. Diffusion lesion reversal between baseline and 3 to 6 hours DWI was also uncommon (7/65, 11%) and often transient. Clinically relevant DLR is uncommon and rarely alters perfusion—diffusion mismatch. The acute diffusion lesion is generally a reliable signature of the infarct core.

Thrombolysis was first shown to be effective for treating acute ischemic stroke around 15 years ago, but therapeutic uptake worldwide has been modest to date. Here, Donnan et al . outline the various strategies that are being explored to optimize the use of thrombolysis, including enhancement of thrombolytic efficacy, extension of the therapeutic time window, reduction in the risk of intracerebral hemorrhage, and improvements in prehospital and in-hospital patient management. Around 15 years have now elapsed since thrombolysis was first shown to be effective for treating acute ischemic stroke, but therapeutic uptake has been modest. As outlined in this Review, research efforts are being directed towards rectifying this situation in a number of ways. First, strategies to enhance thrombolytic efficacy are being tested; these include intravenous and intra-arterial bridging protocols, sonothrombolysis, and the use of alternative thrombolytic agents. Second, means of extending the 4.5-h therapeutic time window up to 6 h, or even up to 9 h in patients selected on the basis of imaging, are being investigated in clinical trials. Prolongation of the time window using neuroprotection to 'freeze' penumbral tissue is also being attempted. Third, attempts are underway to reduce the risk of symptomatic intracerebral hemorrhage (currently affecting about 7% of cases) by refining imaging selection criteria, and through the use of alternative thrombolytic agents, lower doses of tissue plasminogen activator, blood-based biomarkers, and neuroprotectants. Last, in an effort to include more people within the currently accepted therapeutic time window, improvements in prehospital management strategies are being introduced. Elimination of prehospital and in-hospital delays is an urgent priority. Key Points Administration of intravenous tissue plasminogen activator (tPA) 0–90 min after stroke onset approximately doubles the odds of near-complete recovery compared with administration at 3.0–4.5 h Newer thrombolytic agents being tested in phase II and III clinical trials include desmoteplase and tenecteplase Penumbral criteria to select patients with viable brain tissue up to 9 h after stroke onset are now being entered into trials of thrombolysis Hypothermia in combination with tPA may be the most effective way to 'freeze' the ischemic penumbra and needs to be tested by clinical trial Bridging protocols using combined intravenous and intra-arterial approaches with tPA may increase recanalization rates An urgent need exists to increase therapeutic uptake of thrombolysis by use of public education campaigns, and by improving prehospital and in-hospital management

In the study by Sposato and colleagues, subsequent cardiac CT or transoesophageal echocardiography was required for confirmation of thrombus. [...]an approach has also major appeal to bypass the difficulty of access to in-hospital echocardiogram, which has been identified as a potential delay to discharge by about 85% of surveyed stroke physicians in a national study done in Australia. 4 Therefore, we argue that a full cardiac CT imaging protocol, either paced to the cardiac rhythm (gated) or not paced (two phase non-gated cardiac) CT, in the hyperacute stroke phase would have strengthened the results of the DAYLIGHT study. Achieving full cardiac chamber imaging could have increased the diagnostic yield and clarified the true nature of the cardioaortic thrombi deemed highly suspected, which accounted for 31% of the potential thrombi seen in the group of patients who received extended CT angiography.

We hypothesized that pretreatment magnetic resonance imaging (MRI) diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) lesion volumes may have influenced clinical response to thrombolysis in the Echoplanar Imaging Thrombolytic Evaluation Trial (EPITHET). In 98 patients randomized to intravenous (IV) tissue plasminogen activator (tPA) or placebo 3 to 6 h after stroke onset, we examined increasing acute DWI and PWI lesion volumes (Tmax—with 2-sec delay increments), and increasing PWI/DWI mismatch ratios, on the odds of both excellent (modified Rankin Scale (mRS): 0 to 1) and poor (mRS: 5 to 6) clinical outcome. Patients with very large PWI lesions (most had internal carotid artery occlusion) had increased odds ratio (OR) of poor outcome with IV-tPA (58% versus 25% placebo; OR=4.13, P=0.032 for Tmax +2-sec volume >190 mL). Excellent outcome from tPA treatment was substantially increased in patients with DWI lesions <18 mL (77% versus 18% placebo, OR=15.0, P<0.001). Benefit from tPA was also seen with DWI lesions up to 25 mL (69% versus 29% placebo, OR=5.5, P=0.03), but not for DWI lesions >25 mL. In contrast, increasing mismatch ratios did not influence the odds of excellent outcome with tPA. Clinical responsiveness to IV-tPA, and stroke outcome, depends more on baseline DWI and PWI lesion volumes than the extent of perfusion–diffusion mismatch.

Background Many aspects of CSF dynamics are poorly understood due to the difficulties involved in quantification and visualization. In particular, there is debate surrounding the route of CSF drainage. Our aim was to quantify CSF flow, volume, and drainage route dynamics in vivo in young and aged spontaneously hypertensive rats (SHR) using a novel contrast-enhanced computed tomography (CT) method. Methods ICP was recorded in young (2–5 months) and aged (16 months) SHR. Contrast was administered into the lateral ventricles bilaterally and sequential CT imaging was used to visualize the entire intracranial CSF system and CSF drainage routes. A customized contrast decay software module was used to quantify CSF flow at multiple locations. Results ICP was significantly higher in aged rats than in young rats (11.52 ± 2.36 mmHg, versus 7.04 ± 2.89 mmHg, p  = 0.03). Contrast was observed throughout the entire intracranial CSF system and was seen to enter the spinal canal and cross the cribriform plate into the olfactory mucosa within 9.1 ± 6.1 and 22.2 ± 7.1 minutes, respectively. No contrast was observed adjacent to the sagittal sinus. There were no significant differences between young and aged rats in either contrast distribution times or CSF flow rates. Mean flow rates (combined young and aged) were 3.0 ± 1.5 μL/min at the cerebral aqueduct; 3.5 ± 1.4 μL/min at the 3rd ventricle; and 2.8 ± 0.9 μL/min at the 4th ventricle. Intracranial CSF volumes (and as percentage total brain volume) were 204 ± 97 μL (8.8 ± 4.3%) in the young and 275 ± 35 μL (10.8 ± 1.9%) in the aged animals (NS). Conclusions We have demonstrated a contrast-enhanced CT technique for measuring and visualising CSF dynamics in vivo. These results indicate substantial drainage of CSF via spinal and olfactory routes, but there was little evidence of drainage via sagittal sinus arachnoid granulations in either young or aged animals. The data suggests that spinal and olfactory routes are the primary routes of CSF drainage and that sagittal sinus arachnoid granulations play a minor role, even in aged rats with higher ICP.

Trials of the efficacy and safety of endovascular thrombectomy in patients with large ischemic strokes have been carried out in limited populations. We performed a prospective, randomized, open-label, adaptive, international trial involving patients with stroke due to occlusion of the internal carotid artery or the first segment of the middle cerebral artery to assess endovascular thrombectomy within 24 hours after onset. Patients had a large ischemic-core volume, defined as an Alberta Stroke Program Early Computed Tomography Score of 3 to 5 (range, 0 to 10, with lower scores indicating larger infarction) or a core volume of at least 50 ml on computed tomography perfusion or diffusion-weighted magnetic resonance imaging. Patients were assigned in a 1:1 ratio to endovascular thrombectomy plus medical care or to medical care alone. The primary outcome was the modified Rankin scale score at 90 days (range, 0 to 6, with higher scores indicating greater disability). Functional independence was a secondary outcome. The trial was stopped early for efficacy; 178 patients had been assigned to the thrombectomy group and 174 to the medical-care group. The generalized odds ratio for a shift in the distribution of modified Rankin scale scores toward better outcomes in favor of thrombectomy was 1.51 (95% confidence interval [CI], 1.20 to 1.89; P<0.001). A total of 20% of the patients in the thrombectomy group and 7% in the medical-care group had functional independence (relative risk, 2.97; 95% CI, 1.60 to 5.51). Mortality was similar in the two groups. In the thrombectomy group, arterial access-site complications occurred in 5 patients, dissection in 10, cerebral-vessel perforation in 7, and transient vasospasm in 11. Symptomatic intracranial hemorrhage occurred in 1 patient in the thrombectomy group and in 2 in the medical-care group. Among patients with large ischemic strokes, endovascular thrombectomy resulted in better functional outcomes than medical care but was associated with vascular complications. Cerebral hemorrhages were infrequent in both groups. (Funded by Stryker Neurovascular; SELECT2 ClinicalTrials.gov number, NCT03876457.).