Associations of thrombus perviousness derived from entire thrombus segmentation with functional outcome in patients with acute ischemic stroke.

Thrombus perviousness is strongly associated with functional outcome and intravenous alteplase treatment success in patients with acute ischemic stroke. Accuracy of thrombus attenuation increase (TAI) assessment may be compromised by a heterogeneous thrombus composition and interobserver variations of currently used manual measurements. We hypothesized that TAI is more strongly associated with clinical outcomes when evaluated on the entire thrombus. In 195 patients, five TAI measures were performed: one manual by placing three regions of interest (TAImanual) and four automated ones assessing densities from the entire thrombus. The automated TAI measures were calculated by comparing quartiles; Q1, Q2, and Q3 of the non-contrast and contrast enhanced thrombus density distribution and using the lag of the maximum of the cross correlations (MCC). Associations with functional outcome (mRS at 90 days) were assessed with univariate and multivariable analyses. All entire TAI measures were significantly associated with functional outcome with odd ratios (OR) of 1.63(95 %CI:1.19-2.25, p = 0.003) for Q1, 1.56(95 %CI:1.16-2.10, p = 0.003) for Q2, 1.24(95 %CI:1.00-1.54, p = 0.045) for Q3, and 1.70(95 %CI:1.24-2.34, p = 0.001) for MCC per 10 HU increase in univariate models. TAImanual was not significantly associated with functional outcome (p = 0.055). In the multivariable logistic regression models including age, NIHSS, and recanalization, only TAI measures derived from the entire thrombus were independently associated with favorable outcome; OR of 1.64(95 %CI:1.01-2.66, p = 0.048) for Q2 and 1.82(1.13-2.95, p = 0.014) for MCC per 10 HU increase of thrombus attenuation. The novel perviousness measures of the entire thrombus are more strongly associated with functional outcome than the traditional manual perviousness assessments.

Prevalence of Carotid Web in Patients with Acute Intracranial Stroke Due to Intracranial Large Vessel Occlusion.

Purpose To investigate the prevalence of symptomatic carotid web in patients with acute ischemic stroke due to intracranial large vessel occlusion, to determine the clinical and imaging profile of patients with carotid web as well as their association with ischemic stroke, and to determine the interobserver agreement in the assessment of carotid webs. Materials and Methods All patients (n = 500) of the Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands (MR CLEAN) in whom the carotid bifurcation could be assessed (n = 443) were included. The presence of a carotid web at the carotid bifurcations was evaluated at computed tomographic (CT) angiography. Demographics, clinical characteristics, and imaging baseline characteristics were presented by descriptive statistics for patients with an identified carotid web. Interobserver agreement in the detection of carotid webs was examined by using kappa statistics. Results Eleven (2.5%) carotid webs were found at the symptomatic side and two (0.5%) carotid webs were found at the asymptomatic side. Ten (91%) patients with a symptomatic carotid web were female. Nine patients with a symptomatic carotid web did not have major risk factors or other causes for ischemic stroke (82%). Fair to good interobserver agreement (κ, 0.72) was observed for diagnosing carotid webs at CT angiography. Conclusion Carotid webs at the symptomatic carotid bifurcation were observed in 2.5% of the patients with acute ischemic stroke due to large vessel occlusion and were mostly diagnosed in female patients with a fair to good interobserver agreement. © RSNA, 2017 Clinical trial registration nos. NTR1804 and ISRCTN10888758 Online supplemental material is available for this article.

Extracranial Carotid Disease and Effect of Intra-arterial Treatment in Patients With Proximal Anterior Circulation Stroke in MR CLEAN.

Background: The presence of extracranial carotid disease (ECD) is associated with less favorable clinical outcomes in patients with acute ischemic stroke caused by intracranial proximal occlusion. Acute intra-arterial treatment (IAT) in the setting of extracranial and intracranial lesions is considered challenging, and whether it yields improved outcomes remains uncertain. Objective: To examine whether the presence of ECD modified the effect of IAT for intracranial proximal anterior circulation occlusion. Design: Prespecified subgroup analysis of a randomized clinical trial of endovascular treatment for acute ischemic stroke in the Netherlands. (Trial registrations: NTR1804 [Netherlands Trial Register] and ISRCTN10888758). Setting: 16 hospitals in the Netherlands. Patients: Acute ischemic stroke caused by proximal intracranial arterial occlusion of the anterior circulation. Extracranial carotid disease was defined as cervical internal carotid artery stenosis (>50%) or occlusion. Intervention: IAT treatment versus no IAT. Measurements: The primary outcome was functional outcome, as measured by the modified Rankin Scale at 90 days and reported as adjusted common odds ratio (acOR) for a shift in direction of a better outcome. Multivariable ordinal logistic regression analysis with an interaction term was used to estimate treatment effect modification by ECD. Results: The overall acOR was 1.67 (95% CI, 1.21 to 2.30) in favor of the intervention. The acOR was 3.1 (CI, 1.7 to 5.8) in the prespecified subgroup of patients with ECD versus 1.3 (CI, 0.9 to 1.9) in patients presenting without ECD. Both acORs are in favor of the intervention (P for interaction = 0.07). Limitation: The study was not powered for subgroup analysis. Conclusion: Intra-arterial treatment may be at least as effective in patients with ECD as in those without ECD, and it should not be withheld in these complex patients with acute ischemic stroke. Primary Funding Source: Dutch Heart Foundation, AngioCare BV, Medtronic/Covidien/EV3, MEDAC Gmbh/LAMEPRO, Penumbra, Stryker, and Top Medical/Concentric.

Dynamic CT perfusion image data compression for efficient parallel processing.

The increasing size of medical imaging data, in particular time series such as CT perfusion (CTP), requires new and fast approaches to deliver timely results for acute care. Cloud architectures based on graphics processing units (GPUs) can provide the processing capacity required for delivering fast results. However, the size of CTP datasets makes transfers to cloud infrastructures time-consuming and therefore not suitable in acute situations. To reduce this transfer time, this work proposes a fast and lossless compression algorithm for CTP data. The algorithm exploits redundancies in the temporal dimension and keeps random read-only access to the image elements directly from the compressed data on the GPU. To the best of our knowledge, this is the first work to present a GPU-ready method for medical image compression with random access to the image elements from the compressed data.

Characteristics of Misclassified CT Perfusion Ischemic Core in Patients with Acute Ischemic Stroke.

BACKGROUND: CT perfusion (CTP) is used to estimate the extent of ischemic core and penumbra in patients with acute ischemic stroke. CTP reliability, however, is limited. This study aims to identify regions misclassified as ischemic core on CTP, using infarct on follow-up noncontrast CT. We aim to assess differences in volumetric and perfusion characteristics in these regions compared to areas that ended up as infarct on follow-up. MATERIALS AND METHODS: This study included 35 patients with >100 mm brain coverage CTP. CTP processing was performed using Philips software (IntelliSpace 7.0). Final infarct was automatically segmented on follow-up noncontrast CT and used as reference. CTP and follow-up noncontrast CT image data were registered. This allowed classification of ischemic lesion agreement (core on CTP: rMTT≥145%, aCBV<2.0 ml/100g and infarct on follow-up noncontrast CT) and misclassified ischemic core (core on CTP, not identified on follow-up noncontrast CT) regions. False discovery ratio (FDR), defined as misclassified ischemic core volume divided by total CTP ischemic core volume, was calculated. Absolute and relative CTP parameters (CBV, CBF, and MTT) were calculated for both misclassified CTP ischemic core and ischemic lesion agreement regions and compared using paired rank-sum tests. RESULTS: Median total CTP ischemic core volume was 49.7ml (IQR:29.9ml-132ml); median misclassified ischemic core volume was 30.4ml (IQR:20.9ml-77.0ml). Median FDR between patients was 62% (IQR:49%-80%). Median relative mean transit time was 243% (IQR:198%-289%) and 342% (IQR:249%-432%) for misclassified and ischemic lesion agreement regions, respectively. Median absolute cerebral blood volume was 1.59 (IQR:1.43-1.79) ml/100g (P<0.01) and 1.38 (IQR:1.15-1.49) ml/100g (P<0.01) for misclassified ischemic core and ischemic lesion agreement, respectively. All CTP parameter values differed significantly. CONCLUSION: For all patients a considerable region of the CTP ischemic core is misclassified. CTP parameters significantly differed between ischemic lesion agreement and misclassified CTP ischemic core, suggesting that CTP analysis may benefit from revisions.

Value of Computed Tomographic Perfusion-Based Patient Selection for Intra-Arterial Acute Ischemic Stroke Treatment.

BACKGROUND AND PURPOSE: The utility of computed tomographic perfusion (CTP)-based patient selection for intra-arterial treatment of acute ischemic stroke has not been proven in randomized trials and requires further study in a cohort that was not selected based on CTP. Our objective was to study the relationship between CTP-derived parameters and outcome and treatment effect in patients with acute ischemic stroke because of a proximal intracranial arterial occlusion. METHODS: We included 175 patients who underwent CTP in the Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in The Netherlands (MR CLEAN). Association of CTP-derived parameters (ischemic-core volume, penumbra volume, and percentage ischemic core) with outcome was estimated with multivariable ordinal logistic regression as an adjusted odds ratio for a shift in the direction of a better outcome on the modified Rankin Scale. Interaction between CTP-derived parameters and treatment effect was determined using multivariable ordinal logistic regression. Interaction with treatment effect was also tested for mismatch (core <70 mL; penumbra core >1.2; penumbra core >10 mL). RESULTS: The adjusted odds ratio for improved functional outcome for ischemic core, percentage ischemic core, and penumbra were 0.79 per 10 mL (95% confidence interval: 0.71-0.89; P<0.001), 0.82 per 10% (95% confidence interval: 0.66-0.90; P=0.002), and 0.97 per 10 mL (96% confidence interval: 0.92-1.01; P=0.15), respectively. No significant interaction between any of the CTP-derived parameters and treatment effect was observed. We observed no significant interaction between mismatch and treatment effect. CONCLUSIONS: CTP seems useful for predicting functional outcome, but cannot reliably identify patients who will not benefit from intra-arterial therapy.

Effect of extended CT perfusion acquisition time on ischemic core and penumbra volume estimation in patients with acute ischemic stroke due to a large vessel occlusion.

BACKGROUND AND PURPOSE: It has been suggested that CT Perfusion acquisition times <60 seconds are too short to capture the complete in and out-wash of contrast in the tissue, resulting in incomplete time attenuation curves. Yet, these short acquisitions times are not uncommon in clinical practice. The purpose of this study was to investigate the occurrence of time attenuation curve truncation in 48 seconds CT Perfusion acquisition and to quantify its effect on ischemic core and penumbra estimation in patients with acute ischemic stroke due to a proximal intracranial arterial occlusion of the anterior circulation. MATERIALS AND METHODS: We analyzed CT Perfusion data with 48 seconds and extended acquisition times, assuring full time attenuation curves, of 36 patients. Time attenuation curves were classified as complete or truncated. Ischemic core and penumbra volumes resulting from both data sets were compared by median paired differences and interquartile ranges. Controlled experiments were performed using a digital CT Perfusion phantom to investigate the effect of time attenuation curve truncation on ischemic core and penumbra estimation. RESULTS: In 48 seconds acquisition data, truncation was observed in 24 (67%) cases for the time attenuation curves in the ischemic core, in 2 cases for the arterial input function and in 5 cases for the venous output function. Analysis of extended data resulted in smaller ischemic cores and larger penumbras with a median difference of 13.2 (IQR: 4.3-26.0) ml (P<0.001) and; 12.4 (IQR: 4.1-25.7) ml (P<0.001), respectively. The phantom data showed increasing ischemic core overestimation with increasing tissue time attenuation curve truncation. CONCLUSIONS: Truncation is common in patients with large vessel occlusion and results in repartitioning of the area of hypoperfusion into larger ischemic core and smaller penumbra estimations. Phantom experiments confirmed that truncation results in overestimation of the ischemic core.

3D movement correction of CT brain perfusion image data of patients with acute ischemic stroke.

INTRODUCTION: Head movement during CT brain perfusion (CTP) acquisition can deteriorate the accuracy of CTP analysis. Most CTP software packages can only correct in-plane movement and are limited to small ranges. The purpose of this study is to validate a novel 3D correction method for head movement during CTP acquisition. METHODS: Thirty-five CTP datasets that were classified as defective due to head movement were included in this study. All CTP time frames were registered with non-contrast CT data using a 3D rigid registration method. Location and appearance of ischemic area in summary maps derived from original and registered CTP datasets were qualitative compared with follow-up non-contrast CT. A quality score (QS) of 0 to 3 was used to express the degree of agreement. Furthermore, experts compared the quality of both summary maps and assigned the improvement score (IS) of the CTP analysis, ranging from -2 (much worse) to 2 (much better). RESULTS: Summary maps generated from corrected CTP significantly agreed better with appearance of infarct on follow-up CT with mean QS 2.3 versus mean QS 1.8 for summary maps from original CTP (P = 0.024). In comparison to original CTP data, correction resulted in a quality improvement with average IS 0.8: 17 % worsened (IS = -2, -1), 20 % remained unchanged (IS = 0), and 63 % improved (IS = +1, +2). CONCLUSION: The proposed 3D movement correction improves the summary map quality for CTP datasets with severe head movement.

Muscle parameters for musculoskeletal modelling of the human neck.

BACKGROUND: To study normal or pathological neuromuscular control, a musculoskeletal model of the neck has great potential but a complete and consistent anatomical dataset which comprises the muscle geometry parameters to construct such a model is not yet available. METHODS: A dissection experiment was performed on the left side of one 50th percentile male embalmed specimen. Geometrical data including muscle attachment sites were digitized using an Optotrak measurement system and laser diffraction was used to determine muscle sarcomere lengths. Bony landmarks were recorded and joint centres of rotation between different vertebrae were estimated using literature data. FINDINGS: A total of 34 muscle parts of the neck were divided in 129 elements per body side. Muscle attachment sites, mass, physiological cross sectional area, fibre length, tendon length and optimal fibre length for each element are supplied as digital annexes to the paper. Results are coherent with other studies and new data are provided for several smaller muscles not reported elsewhere. INTERPRETATION: Implementation of this dataset into a neck model is likely to improve the estimation of muscle forces and thus increase the model validity; this makes future neck models more suitable for the use as clinical tools.