Mean Transient Time Research Articles

Computed tomography perfusion as a predictor of gastric cancer grades

BackgroundGastric cancer stands as one of the most prevalent malignancies globally, conventional endoscopic specimens have been the primary means of diagnosing preoperative gastric histopathology, however, their limitations in capturing intra-tumor heterogeneity compromise their efficacy in evaluating angiogenesis. Perfusion Computed Tomography (P-CT) emerges as a pivotal functional imaging modality, facilitating objective assessment of tissue perfusion, serving as a marker of angiogenesis. So, our research objective was to evaluate the efficacy of CT perfusion imaging in the prediction of histological grades of gastric tumors using quantitative perfusion parameters such as permeability surface (PS), blood flow (BF), mean transient time (MTT), and blood volume (BV), in addition to the qualitative scoring system then comparing the findings with the histopathological results.ResultsPS and BF were statistically significant predictors of the grade of differentiation, their odds ratio (OR) was (1.05, 95% CI 1.02–1.09, for each of them) (P = 0.004, P = 0.009, respectively). MTT also emerged as a significant predictor of the grade of differentiation with an OR of 0.76 (95% CI 0.57–0.93, P = 0.025). Using multivariate logistic regression model, PS was the most potent individual P-CT predictor of differentiation of the grade and the diagnosis of poorly differentiated tumors at ≥ 39 mL/100 g/min cut off point, followed by BF at ≥ 82.2 mL/100 g/min, and MTT at < 8.4 s. Regarding the qualitative scoring system P-CT, poorly differentiated tumors generally received higher scores of PS (P < 0.001), BF (P < 0.001), and BV (P = 0.017), than well and moderately differentiated tumors, however, MTT showed that poorly differentiated tumors were more frequently scored as low compared to well and moderately differentiated tumors (P < 0.001).ConclusionsP-CT is an innovative, non-invasive biomarker for predicting gastric cancer grade by quantitative and qualitative assessment by P-CT parameters (PS, BF and MTT) with particular role of PS as the strongest individual P-CT predictor of differentiation grade followed by BF and MTT at specific cut off points.

ADDED UTILITY OF COMPUTED TOMOGRAPHY PERFUSION STUDY IN THE ASSESSMENT OF EARLY ISCHEMIC STROKE IN COMPARISON WITH NONCONTRAST COMPUTED TOMOGRAPHY - A PROSPECTIVE OBSERVATIONAL STUDY

Objective: 1. T o study the added utility of computed tomography perfusion study in the assessment of early ischemic stroke in comparison with non-contrast computed tomography. 2. To study the role of computed tomography perfusion study in deciding thrombolytic treatment/ therapeutic protocols aimed at reversing the cerebral ischemic insult. Conclusions and Results: It was observed that 15 (46.68%) patients were in the 61-70 years of age group followed by 8 (25%) in the age group of 51-60 years. The mean age of the patients was 58.87 ±12.14 years. Ÿ Females were affected more i.e. 18 (56.25%) compared to the male patients 14 (43.75%). Ÿ Most observed co-morbid condition was hypertension in 9 (28.13%) patients followed by hypertension and diabetes in 7 (21.87%) patients and diabetes in 6 (18.75%) patients. Ÿ Among the study participants 4 (12.50%) were smokers followed by 6 (18.75%) were alcoholic and smokers &amp; alcoholic (15.62%) respectively. Ÿ It was observed that the symptoms of palsy were present among 23 (71.88%) patients Ÿ The most commonly observed time of onset of symptoms was 3-5 hours in 23 (71.88%) patients followed by 1-3 hours (21.87%) and &gt;5 hours in 2 (6.25%) patients. Ÿ NCCT ndings observed was denite signs of stroke in 12 (37.5%) patients followed by suspected signs of stroke on NCCT (25%) Ÿ It was observed that no sign of stroke was observed in 12 (37.5%) patients. Ÿ CT perfusion ndings observed was increased mean transient time (MTT) in all (100%) patients followed by decreased blood ow in all (100%) patients. It was observed that cerebral blood volume decreased in 12 (37.5%) patients, increased in 8 (25%) and normal in 12 (37.5%) patients. Ÿ The correlation of NCCT and CT perfusion ndings observed that out of total 32 patients NCCT study identies 20 patients while all 32 patients were identied by CT perfusion study with sensitivity of 100%. Ÿ CT perfusion provides early diagnosis of ischemic stroke thus helps in management of stroke patients. Inference : The present study concludes that CT-perfusion had more sensitivity compared to NCCT in identifying early ischemic stroke. CT perfusion has additional utility in management of early ischemic stroke. CT Perfusion study provides important information to the neurologist and neuro-interventionalist when evaluating patients for endovascular reperfusion therapy by identifying the size of core infarction and penumbra

Cerebral Perfusion and Functional Outcome in Pediatric Head Injury Patients.

To evaluate the usefulness and degree of perfusion abnormalities in pediatric head injury patients by using computed tomography perfusion (CTP) and to assess its co-relation with neurologic outcome based on Glasgow Outcome Scale Extended Pediatric revision (GOSE-P). Prospective evaluation of pediatric head injury patients who were taken for CTP after admission and then on discharge. We evaluated 5 regions of interest: orbitofrontal cortex, internal capsule, thalamus, caudate nucleus, and sensorimotor cortex for cerebral blood perfusion. The patient's clinical and radiologic findings were analyzed, correlated with cerebral blood flow (CBF) and MTT (mean transient time), and the outcome assessed using the GOSE-P scale on 3-month follow-up. Both CBF and MTT showed a correlation with the GOSE-P scale. In mild head injury patients, the Pearson correlation of GOSE-P with mean CBF and mean MTT was -0.11 and 0.56, respectively (P < 0.05) in the sensorimotor cortex; in moderate head injury patients the Pearson correlation of GOSE-P with mean CBF in the caudate nucleus and mean MTT in the internal capsule was -0.32 and 0.36, respectively (P < 0.05); and in severe head injury patients, the Pearson correlation of GOSE-P with mean CBF and mean MTT was -0.78 and 0.56, respectively (P < 0.05) in the caudate nucleus, which had the highest Pearson co-relation among the regions studied. We conclude that CBF and MTT are 2 important radiologic parameters that can be used as prognostic indicators in pediatric head injury patients.

Association of hyperglycemia and computed tomographic perfusion deficits in patients who underwent endovascular treatment for acute ischemic stroke caused by a proximal intracranial occlusion: A subgroup analysis of a randomized phase 3 trial (MR CLEAN)

IntroductionHyperglycemia is highly prevalent in patients with acute ischemic stroke and is associated with increased risk of symptomatic intracranial hemorrhage, larger infarct size and unfavorable outcome. Furthermore, glucose may modify the effect of endovascular treatment (EVT) in patients with ischemic stroke. Hyperglycemia might lead to accelerated conversion of penumbra into infarct core. However, it remains uncertain whether hyperglycemia on admission is associated with the size of penumbra or infarct core in acute ischemic stroke. In this study, we aimed to assess the association between hyperglycemia and Computed Tomographic Perfusion (CTP) derived parameters in patients who underwent EVT for acute ischemic stroke. MethodsWe used data from the MR CLEAN study (Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands). Hyperglycemia was defined as admission serum glucose of >7.8 mmol/L. Dichotomized and quantiles of glucose levels were related to size of core, penumbra and core penumbra ratio. Hypoperfused area is mean transient time 45% higher than that of the contralateral hemisphere. Core is the area with cerebral blood volume of <2 mL/100 g and penumbra is the area with cerebral blood volume > 2 mL/100 g. Core-penumbra ratio is the ischemic core divided by the total volume of hypoperfused tissue (core plus penumbra) multiplied by 100. Adjustments were made for age, sex, NIHSS on admission, onset-imaging time and diabetes mellitus. ResultsHundred seventy-three patients were included. Median glucose level on admission was 6.5 mmol/L (IQR 5.8–7.5 mmol/L) and thirty-five patients (20%) were hyperglycemic. Median core volume was 33.3 mL (IQR 13.6–62.4 mL), median penumbra volume was 80.2 mL (IQR 36.3–123.5 mL) and median core-penumbra ratio was 28.5% (IQR 18.6–45.8%). Patients with hyperglycemia on admission had larger core volumes and core penumbra ratio than normoglycemic patients with a regression coefficient of 15.1 (95% confidence interval (CI), 1.8 to 28.3) and 11.5 (95% confidence interval (CI), 3.4 to 19.7) respectively. ConclusionHyperglycemia on admission was associated with larger ischemic core volume and larger core-penumbra ratio in patients with acute ischemic stroke who underwent endovascular treatment.

A Tillage Depth Monitoring and Control System for the Independent Adjustment of Each Subsoiling Shovel

Subsoiling can break the compacted hardpan without turning or mixing soil layers. It has significant advantages in improving soil structure, promoting rainwater infiltration, and increasing air permeability of soil. The soil compacted hardpan will not be completely broken and more power consumption will be generated unless the desired tillage depth is obtained. However, due to uneven surface between and within each row of subsoiling shovel in the field, the existing adjustment methods, adjusting via the lifting device of the whole machine or a group of tillage components, cannot ensure each subsoiling shovel avoiding undesired tillage depth. Therefore, a tillage depth monitoring and control system for the independent adjustment of each subsoiling shovel was developed, and the methods of detecting, adjusting, displaying, and recording tillage depth were described. Field experiments were conducted to evaluate detecting accuracy, stability of tillage depth, transient response time, and advantages. The results showed that the value obtained by sensor differed from manual measurement at the speed of 3 km/h, 4 km/h, and 5 km/h averagely by 8.28%. The mean value of the coefficient of the tillage depth stability at three speeds were all greater than 94%. The mean transient response time was 0.6 s. The standard deviation of tillage depth obtained under system control was 38.31, which was less than the 51.52 obtained by only adjusting on the three-point suspension. The subsoiler equipped with this system was capable of obtaining a desired tillage depth of each subsoiling shovel in every second.

Non-monotonic transients to synchrony in Kuramoto networks and electrochemical oscillators

We performed numerical simulations with the Kuramoto model and experiments with oscillatory nickel electrodissolution to explore the dynamical features of the transients from random initial conditions to a fully synchronized (one-cluster) state. The numerical simulations revealed that certain networks (e.g., globally coupled or dense Erdős–Rényi random networks) showed relatively simple behavior with monotonic increase of the Kuramoto order parameter from the random initial condition to the fully synchronized state and that the transient times exhibited a unimodal distribution. However, some modular networks with bridge elements were identified which exhibited non-monotonic variation of the order parameter with local maximum and/or minimum. In these networks, the histogram of the transients times became bimodal and the mean transient time scaled well with inverse of the magnitude of the second largest eigenvalue of the network Laplacian matrix. The non-monotonic transients increase the relative standard deviations from about 0.3 to 0.5, i.e., the transient times became more diverse. The non-monotonic transients are related to generation of phase patterns where the modules are synchronized but approximately anti-phase to each other. The predictions of the numerical simulations were demonstrated in a population of coupled oscillatory electrochemical reactions in global, modular, and irregular tree networks. The findings clarify the role of network structure in generation of complex transients that can, for example, play a role in intermittent desynchronization of the circadian clock due to external cues or in deep brain stimulations where long transients are required after a desynchronization stimulus.

Abstract P325: Validation of Deep Learning Based Critical Hypoperfusion and Ischemic Core Prediction in a Multicenter External Randomized Controlled Trial

Objective: We previously developed two separate deep learning (DL) models to segment the ischemic core and critically hypoperfused tissue on baseline imaging of acute ischemic stroke patients. We aimed to validate the models in an external, multi-center randomized clinical trial (DEFUSE3) and compare with the current clinical standard. Methods: The DL models were previously trained in a separate dataset in which follow-up MRI, obtained at 3-7 days, was used as the reference for critically hypoperfused tissue in patients who did not reperfuse and as the reference for the ischemic core in patients who did reperfuse. For validation, we included DEFUSE3 patients with adequate quality baseline MR perfusion and a 24-hour follow-up DWI scan. The 24-hour DWI lesion served as the reference for ischemic core in patients in the thrombectomy arm and for critically hypoperfused tissue for patients in the medical arm. RAPID was used to generate perfusion maps (Tmax, cerebral blood flow, cerebral blood volume, and mean transient time). The accuracy of segmenting the ischemic core and critically hypoperfused tissue on baseline imaging was compared between the DL approach and the traditional thresholding approach implemented in RAPID. Results: In the 46 patients included for analysis, 24 were in the medical arm and 22 in the thrombectomy arm. Compared to a traditional thresholding method, the DL model segmented the ischemic core more accurately (AUC of 0.92 vs 0.72, p=0.0001 and volume difference of -8ml vs -21ml, p=0.001). Similarly, the DL model segmented critically hypoperfused tissue more accurately (AUC of 0.93 vs 0.80, p&lt;0.0001; volume difference 14ml vs. 55ml, p=0.0005). However, great heterogeneity in final infarct was noticed in medical arm. See tables and figures. Conclusions: The DL-based critical hypoperfusion and ischemic core prediction provides more accurate prediction on final infarct than a commonly used thresholding method in this external validation.

Abstract P319: Can Deep Learning Find the Ischemic Core on CT? Transfer Learning From Pre-Trained MRI-Based Networks

Objective: Ischemic core prediction from CT perfusion (CTP) remains inaccurate compared with gold standard diffusion-weighted imaging (DWI). We evaluated if a deep learning model to predict the DWI lesion from MR perfusion (MRP) could facilitate ischemic core prediction on CTP. Method: Using the multi-center CRISP cohort of acute ischemic stroke patient with CTP before thrombectomy, we included patients with major reperfusion (TICI score≥2b), adequate image quality, and follow-up MRI at 3-7 days. Perfusion parameters including Tmax, mean transient time, cerebral blood flow (CBF), and cerebral blood volume were reconstructed by RAPID software. Core lab experts outlined the stroke lesion on the follow-up MRI. A previously trained MRI model in a separate group of patients was used as a starting point, which used MRP parameters as input and RAPID ischemic core on DWI as ground truth. We fine-tuned this model, using CTP parameters as input, and follow-up MRI as ground truth. Another model was also trained from scratch with only CTP data. 5-fold cross validation was used. Performance of the models was compared with ischemic core (rCBF≤30%) from RAPID software to identify the presence of a large infarct (volume&gt;70 or &gt;100ml). Results: 94 patients in the CRISP trial met the inclusion criteria (mean age 67±15 years, 52% male, median baseline NIHSS 18, median 90-day mRS 2). Without fine-tuning, the MRI model had an agreement of 73% in infarct &gt;70ml, and 69% in &gt;100ml; the MRI model fine-tuned on CT improved the agreement to 77% and 73%; The CT model trained from scratch had agreements of 73% and 71%; All of the deep learning models outperformed the rCBF segmentation from RAPID, which had agreements of 51% and 64%. See Table and figure. Conclusions: It is feasible to apply MRP-based deep learning model to CT. Fine-tuning with CTP data further improves the predictions. All deep learning models predict the stroke lesion after major recanalization better than thresholding approaches based on rCBF.

Mitigating long transient time in deterministic systems by resetting.

How long does a trajectory take to reach a stable equilibrium point in the basin of attraction of a dynamical system? This is a question of quite general interest and has stimulated a lot of activities in dynamical and stochastic systems where the metric of this estimation is often known as the transient or first passage time. In nonlinear systems, one often experiences long transients due to their underlying dynamics. We apply resetting or restart, an emerging concept in statistical physics and stochastic process, to mitigate the detrimental effects of prolonged transients in deterministic dynamical systems. We show that resetting the intrinsic dynamics intermittently to a spatial control line that passes through the equilibrium point can dramatically expedite its completion, resulting in a huge reduction in mean transient time and fluctuations around it. Moreover, our study reveals the emergence of an optimal restart time that globally minimizes the mean transient time. We corroborate the results with detailed numerical studies on two canonical setups in deterministic dynamical systems, namely, the Stuart-Landau oscillator and the Lorenz system. The key features-expedition of transient time-are found to be very generic under different resetting strategies. Our analysis opens up a door to control the mean and fluctuations in transient time by unifying the original dynamics with an external stochastic or periodic timer and poses open questions on the optimal way to harness transients in dynamical systems.

Role of Computed Tomography Perfusion in Identification of Acute Lacunar Stroke Syndromes.

Lacunar syndromes correlate with a lacunar stroke on imaging in 50% to 60% of cases. Computed tomography perfusion (CTP) is becoming the preferred imaging modality for acute stroke triage. We aimed to estimate the sensitivity, specificity, and predictive values for noncontrast computed tomography and CTP in lacunar syndromes, and for cortical, subcortical, and posterior fossa regions. A retrospective analysis of confirmed ischemic stroke patients who underwent acute CTP and follow-up magnetic resonance imaging between 2010 and 2018 was performed. Brain noncontrast computed tomography and CTP were assessed independently by 2 stroke neurologists. Receiver operating characteristic curve analysis was performed to estimate sensitivity, specificity, and area under the curve (AUC) for the detection of strokes in patients with lacunar syndromes using different CTP maps. We found 106 clinical lacunar syndromes, but on diffusion-weighted imaging, these consisted of 59 lacunar, 33 cortical, and 14 posterior fossa strokes. The discrimination of ischemia identification was very poor using noncontrast computed tomography in all 3 regions, but good for cortical (AUC, 0.82) and poor for subcortical and posterior regions (AUCs, 0.55 and 0.66) using automated core-penumbra maps. The addition of delay time and mean transient time maps substantially increased subcortical (AUC, 0.80) and slightly posterior stroke detection (AUC, 0.69). Analysis of mean transient time and delay time maps in combination with core-penumbra maps improves detection of subcortical and posterior strokes.

Unraveling controlling factors of concentration discharge relationships in a fractured aquifer dominant spring-shed: Evidence from mean transit time and radium reactive transport model

This study unravels the controlling factors of concentration-discharge (C-Q) relations and solute export regimes of spring water based on long term monitoring of physicochemical parameters, radium and 222Rn. A simplified analytical solution is derived to quantify radium based mean transient time (MTT) based on radium disequilibrium. Key hydrogeological and lithological parameters such as retardation factor (Rf,Ra) and MTT of radium nuclides, and effective surface areas (Se) of subsurface are therefore quantified based on the long term monitoring records and discussed with the C-Q relation and solute export regimes. The study leads to the findings: 1) The spring water is characterized by very short MTT (days to weeks). Lower MTT, higher effective surface areas and Rf,Ra are observed during the wet seasons than the dry seasons. 2) The slow mass transfer between immobile and mobile phases controls the solute exports of Cl−, Na+, K+, Ca2+, and Mg2+. Export regimes of theses solutes are negligibly influenced by dynamics of Se and retardation processes. 3) Lower MTT, higher Se and activation of NO3− and SO42− lead to higher concentrations of NO3− and SO42− in wet seasons, and vice versa in dry seasons. 4) SO42− export is additionally influenced by co-precipitation of sulphate precipitates. HCO3− is controlled by dynamics of CO2 dissolution caused by fluctuations of water temperature and water table. This study demonstrates that the disequilibrium of radium transport in the fractured aquifer can be deployed to investigate the metrics of the critical zone and the solute export regimes of a springshed.

Abstract WMP19: Prediction of Subacute Infarction in Acute Ischemic Stroke Using Baseline Multi-modal MRI and Deep Learning

Objective: We aim to investigate if a deep learning algorithm can predict the location and size of subacute infarction in acute stroke patients using input data from baseline multimodal MRI. Methods: Acute ischemic stroke patients were reviewed and selected from Imaging Collaterals in Acute Stroke (iCAS) study from Apr 2014 to Aug 2017. We included patients who underwent baseline imaging including perfusion-weighted imaging, diffusion-weighted imaging, gradient echo, and arterial spin labeling; and follow up imaging with FLAIR performed 3-5 days after stroke onset. The ground truth was defined as the stroke lesions on follow-up T2-FLAIR, which were manually delineated by readers blinded to clinical information. Perfusion maps such as Tmax, cerebral blood flow, cerebral blood volume, and mean transient time were reconstructed by RAPID software. All images were co-registered to MNI template space. A U-Net model was trained with the above-mentioned 8 different contrasts as inputs (Figure A). 16 different rigid translation based augmentations were used to augment the training data size. The model was trained based on mixed loss function of cross-entropy and Dice score. Five-fold cross-validation was performed to evaluate the predictions and the results are reported as area under curve (AUC). Results: 38 patients were included (19 males, age 63±15, mRS 3 [IQR 1-4]). Eight patients underwent IV tPA only, 10 with IV tPA plus thrombectomy, 11 with thrombectomy only, and 9 without reperfusion therapy. The overall AUC of this model reached 0.942±0.053 in all slices, and 0.938±0.050 in slices that contain stroke lesions (Figure B&amp;C), compared to 0.734±0.104 for Tmax map and 0.88±0.12 in a larger previous reported study (Nielsen et al., Stroke 2017). Conclusions: Deep learning algorithms can accurately predict established stroke lesions using the information provided in baseline multimodal MRI. This may have value for patient selection for stroke therapies.

Hybrid Surgery for Internal Carotid Artery Revascularization

The management of chronic complete internal carotid artery (ICA) occlusion (COICA) has been challenging. Endovascular procedures have been performed with variable success and risks, depending on the type of occlusion and distal revascularization. We present a novel hybrid procedure to recanalize the ICA when previous endovascular interventions have failed or been deemed too risky. Two patients presented with symptomatic COICA after maximal medical management. They were deemed at high risk of endovascular intervention and/or previous endovascular attempts had failed. Thus, they had indications for a hybrid procedure. A hybrid technique was used to create a stump by surgical endarterectomy, followed by recanalization using an endovascular approach via femoral access. We have described the technique in detail. Postoperative computed tomography perfusion scanning showed normalization of the mean transient time, cerebral blood volume, and cerebral blood flow compared with the preoperative findings. Cerebral angiography showed successful recanalization of the ICA. Neither patient experienced any complications. A hybrid technique is feasible and should be considered for patients with COICA in whom maximal medical management has failed and who have a high-risk profile for endovascular intervention or in whom previous endovascular attempts have failed.

Postcranioplasty Quantitative Assessment of Intracranial Fluid Dynamics and Its Impact on Neurocognition Cranioplasty Effect: A Pilot Study

This study was done to evaluate the effects of cranioplasty on cerebrohemodynamics (cerebral blood flow [CBF] and mean transient time [MTT]) and cerebrospinal fluid (CSF) hydrodynamics (flow velocities) by using computed tomography perfusion and cardiac-gated cine phase magnetic resonance imaging (MRI) (phase contrast [PC] MRI), respectively. It also aims to determine the co-relation between changes in CBF, MTT, and CSF flow dynamics with neurocognitive outcome. The mean values of ipsilateral CBF were 27.58 and 41.66 mL/min/100 g in pre- and postcranioplasty patients, respectively (P= 0.04). Contralateral CBF also showed improvement from 38.76 to 60.44 mL/min/100 g (P= 0.03). Mean values of MTT were found to be decreased in the bilateral hemisphere after cranioplasty. On evaluation of CSF flow velocities by PC MRI, the means of the maximum velocity and peak velocity at the aqueduct of Sylvius were increased from pre- to postcranioplasty as 2.36 to 3.84 cm/s (P= 0.048) and 1.21 to 3.50 cm/s (P < 0.001), respectively. Cognitive evaluation showed a significant improvement at 1 (P= 0.035) and 6 months (P= 0.002) postcranioplasty. All cases were subjected to precranioplasty cine phase cardiac gated contrast MRI for CSF dynamics and computed tomography perfusion for cerebrovascular hemodynamic parameters. CBF and related indices were calculated at different regions of interest with the help of the manufacturer's software package of computed tomography perfusion in the ipsilateral hemisphere and simultaneously on the contralateral side. Cine cardiac gated phase contrast MRI was also done for CSF flow velocity at the aqueduct of Sylvius and median aperture (foramen of Magendie). Both studies were again performed on postcranioplasty day 5-7. Cranioplasty can remarkably improve cortical perfusion for both the ipsilateral and contralateral hemispheres. Postoperative increased CSF velocities suggest improved rapid turnover of CSF in a circuit and possibly play a role in good neurologic outcome. Our study shows there is improvement in CSF flow at the aqueduct of Sylvius after cranioplasty. We propose that improvement in CSF circulation along with changes in CBF co-relate well with cognitive outcome (Montreal Cognitive Assessment score).

MRI of plaque characteristics and relationship with downstream perfusion and cerebral infarction in patients with symptomatic middle cerebral artery stenosis.

Intracranial plaque characteristics are associated with stroke events. Differences in plaque features may explain the disconnect between stenosis severity and the presence of ischemic stroke. To investigate the relationship between plaque characteristics and downstream perfusion changes, and their contribution to the occurrence of cerebral infarction beyond luminal stenosis. Case control. Forty-six patients with symptomatic middle cerebral artery (MCA) stenosis (with acute cerebral infarction, n = 30; without acute cerebral infarction, n = 16). 3.0T with 3D turbo spin echo sequence (3D-SPACE). Luminal stenosis grade, plaque features including lesion T2 and T1 hyperintense components, plaque enhancement grade, and plaque distribution were assessed. Brain perfusion was evaluated on mean transient time maps based on the Alberta Stroke Program Early CT score (MTT-ASPECTS). Plaque features, grade of luminal stenosis, and MTT-ASPECTS were compared between two groups. The association between plaque features and MTT-ASPECTS were assessed using Spearman's correlation analysis. Multivariate logistic regression and receiver operating characteristic (ROC) curves were constructed to assess the effect of significant variables alone and their combination in determining the occurrence of cerebral infarction. Stronger enhanced plaques were associated with downstream lower MTT-ASPECTS (P = 0.010). Plaque enhancement grade (P = 0.039, odds ratio [OR] 5.9, 95% confidence interval [CI] 1.1-32) and MTT-ASPECTS (P = 0.003, OR 2.6, 95% CI 1.4-4.7) were associated with a recent cerebral infarction, whereas luminal stenosis grade was not (P = 0.128). The combination of MTT-ASPECTS and plaque enhancement grade provided incremental information beyond luminal stenosis grade alone. The area under the receiver operating characteristic curve (AUC) improved from 0.535 to 0.921 (P < 0.05). Strongly enhanced plaques are associated with a higher likelihood of downstream perfusion impairment. Plaque enhancement and perfusion evaluation may play a complementary role to luminal stenosis in determining the occurrence of acute cerebral infarction. 4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017.

Automatic flow analysis of digital subtraction angiography using independent component analysis in patients with carotid stenosis.

PurposeCurrent time—density curve analysis of digital subtraction angiography (DSA) provides intravascular flow information but requires manual vasculature selection. We developed an angiographic marker that represents cerebral perfusion by using automatic independent component analysis.Materials and methodsWe retrospectively analyzed the data of 44 patients with unilateral carotid stenosis higher than 70% according to North American Symptomatic Carotid Endarterectomy Trial criteria. For all patients, magnetic resonance perfusion (MRP) was performed one day before DSA. Fixed contrast injection protocols and DSA acquisition parameters were used before stenting. The cerebral circulation time (CCT) was defined as the difference in the time to peak between the parietal vein and cavernous internal carotid artery in a lateral angiogram. Both anterior-posterior and lateral DSA views were processed using independent component analysis, and the capillary angiogram was extracted automatically. The full width at half maximum of the time—density curve in the capillary phase in the anterior-posterior and lateral DSA views was defined as the angiographic mean transient time (aMTT; i.e., aMTTAP and aMTTLat). The correlations between the degree of stenosis, CCT, aMTTAP and aMTTLat, and MRP parameters were evaluated.ResultsThe degree of stenosis showed no correlation with CCT, aMTTAP, aMTTLat, or any MRP parameter. CCT showed a strong correlation with aMTTAP (r = 0.67) and aMTTLat (r = 0.72). Among the MRP parameters, CCT showed only a moderate correlation with MTT (r = 0.67) and Tmax (r = 0.40). aMTTAP showed a moderate correlation with Tmax (r = 0.42) and a strong correlation with MTT (r = 0.77). aMTTLat also showed similar correlations with Tmax (r = 0.59) and MTT (r = 0.73).ConclusionApart from vascular anatomy, aMTT estimates brain parenchyma hemodynamics from DSA and is concordant with MRP. This process is completely automatic and provides immediate measurement of quantitative peritherapeutic brain parenchyma changes during stenting.

Clinical Use of Computed Tomographic Perfusion for the Diagnosis and Prediction of Lesion Growth in Acute Ischemic Stroke

Computed tomography perfusion (CTP) mapping in research centers correlates well with diffusion-weighted imaging (DWI) lesions and may accurately differentiate the infarct core from ischemic penumbra. The value of CTP in real-world clinical practice has not been fully established. We investigated the yield of CTP-derived cerebral blood volume (CBV) and mean transient time (MTT) for the detection of cerebral ischemia and ischemic penumbra in a sample of acute ischemic stroke (AIS) patients. We studied 165 patients with initial clinical symptoms suggestive of AIS. All patients had an initial noncontrast head CT, CTP, CT angiogram (CTA), and follow-up magnetic resonance imaging (MRI) of the brain. The obtained perfusion images were used for image processing. CBV, MTT, and DWI lesion volumes were visually estimated and manually traced. Statistical analysis was conducted using R and SAS software. All normal DWI sequences had normal CBV and MTT studies (N=89). Seventy-three patients had acute DWI lesions. CBV was abnormal in 23.3% and MTT was abnormal in 42.5% of these patients. There was a high specificity (91.8%) but poor sensitivity (40.0%) for MTT maps predicting positive DWI. The Spearman correlation was significant between MTT and DWI lesions (ρ=0.66; P>.0001) only for abnormal MTT and DWI lesions >0 cc. CBV lesions did not correlate with final DWI. In real-world use, acute imaging with CTP did not predict stroke or DWI lesions with sufficient accuracy. Our findings argue against the use ofCTP for screening AIS patients until real-world implementations match the accuracy reported from specialized research centers.

Optimisation of vascular input and output functions in CT-perfusion imaging using 256(or more)-slice multidetector CT

To evaluate the accuracy and reproducibility of CT-perfusion (CTP) by finding the optimal artery for the arterial input function (AIF) and re-evaluating the necessity of the venous output function (VOF). Forty-four acute ischaemic stroke patients who underwent non-enhanced CT, CTP and CT-angiography using 256-slice multidetector computed tomography (MDCT) were evaluated. The anterior cerebral artery (ACA), middle cerebral artery (MCA), internal carotid artery (ICA) and basilar artery were selected as the AIF. Subsequently the resulting area under the time-enhancement curve of the AIF (AUCAIF) and quantitative perfusion measurements were analysed by repeated measures ANOVA and subsequently the paired t test. To evaluate reproducibility we examined if the VOF could be deleted by comparing the perfusion measurements using versus not using the VOF (paired t test). The AUCAIF and perfusion measurements resulting from the different AIFs showed significant group differences (all P < 0.0001). The ICA had the largest AUCAIF and resulted in the highest mean transient time (MTT) and lowest cerebral blood flow (CBF), whereas the basilar artery showed the lowest cerebral blood volume (CBV). Not using the VOF showed significantly higher CBV and CBF in 66 % of patients on the ipsilateral (P < 0.0001 and P = 0.007, respectively) and contralateral hemisphere (P < 0.0001 and P = 0.019, respectively). Selecting the ICA as the AIF and continuing the use of the VOF would improve the accuracy of CTP. • Perfusion imaging is an increasingly important aspect of multidetector computed tomography (MDCT). • Vascular input functions were evaluated for CT-perfusion using 256-slice MDCT. • Selecting different arterial input functions (AIFs) leads to variation in quantitative values. • Using the internal carotid artery for AIF provides optimal perfusion values. • Deleting the venous output function would be detrimental for validity.

Abstract 3048: Real-World Clinical Use of CT Perfusion for Diagnosis and Prediction of Lesion Growth in Acute Ischemic Stroke

Background: Diffusion-weighted imaging (DWI) detects acute ischemia with a high sensitivity. In research centers, qualitative CT perfusion (CTP) mapping correlates well with DWI and may accurately differentiate the infarct core from ischemic penumbra. The value of the CTP in real-world clinical practice, however, has not been fully established. We investigated the yield of CTP - derived cerebral blood volume (CBV) and mean transient time (MTT) for the detection of cerebral ischemia in a sample of acute ischemic stroke (AIS) patients. Methods: In a large metropolitan academic medical center that is a certified Primary Stroke Center (PSC) we retrospectively studied 162 patients who presented between January 2008 and July 2010 with symptoms suggestive of AIS. All patients had an initial Code Brain protocol including non-contrast head CT, CTP, and CTA. As clinically indicated, some patients underwent follow up brain MRI within 48 hours. Acute perfusion maps were derived in real time by a trained operator. From the obtained images CBV, MTT and DWI lesion volumes were manually traced using planimetry (ImageJ v1.42) by two stroke neurologists blinded to clinical information. Volumes were calculated using the Cavaleri theorem. Sensitivity, specificity and statistical analysis were calculated using Graph Pad 5.0. Results: Of 162 patients with acute stroke-like symptoms, 73 had DWI lesions. The sensitivity and specificity to detect abnormal DWI signals were 23% and 100%, for CBV; and 43.8% and 98.9% for MTT. For DWI lesions ≥5ml the yield was 59.3% for CVB and 77.8% for MTT. For lesions ≥10ml the yield was 68.4% for CBV and 89.5% for MTT. In patients with NIHSS ≥5, CBV predicted abnormal DWI in 22.6% and MTT in 35.5%. In patients with NIHSS ≥10, CBV and MTT, both had a yield of 50.0%. A CBV - MTT mismatch of &gt;25% predicted MRI lesion extension in 81.25% of the cases. There were small but significant correlations for DWI versus CBV lesion volumes ( r 2 0.32, P= 0.0001), and for DWI versus MTT lesion volumes ( r 2 0.29, P &lt;0.0001). Correlation between DWI and perfusion maps for MCA territory infarcts were CBV ( r 2 0.3, P &lt;0.0001) and MTT ( r 2 0.45, P &lt;0.0001). Conclusions: In real-world deployment during a Code Brain protocol in a busy PSC, acute imaging with CTP did not predict DWI lesions on brain MRI with sufficient accuracy. In patients with large lesions the predictive value was better.

Acute perfusion changes after spontaneous SAH: a perfusion CT study

Perfusion computed tomography (CT) is a rapid technique that allows the measurement of acute disturbances in local and global cerebral blood flow in patients suffering stroke and spontaneous subarachnoid haemorrhage (SAH). The purpose of this study was to establish the relationship between different measures of brain perfusion made on dynamic-contrast CT reconstructions performed as soon as SAH has been diagnosed and the severity of the bleeding determined by the clinical grade, the extent of the bleeding and the outcome of the patients. After the diagnosis of SAH by conventional CT, a perfusion CT was performed before CT angiography. All imaging studies were performed on a six-slice spiral CT scanner. All images were analysed using perfusion software developed by Philips, which produces perfusion CT quantitative data based on temporal changes in signal intensity during the first pass of a bolus of an iodinated contrast agent. Measurements of mean transient time (MTT), time to peak (TTP), cerebral blood volume (CBV) and cerebral blood flow (CBF) in volumes of interest corresponding to territories perfused by the major cerebral arteries were performed. Different data regarding severity of the bleeding-such as level of consciousness, amount of bleeding in conventional CT-were collected. All poor-grade patients received a ventriculostomy catheter so that ICP recordings were obtained. Also, the occurrence of delayed cerebral ischaemia (DCI) was recorded. Outcome was assessed by the Glasgow Outcome Scale 6 months after the bleeding. For statistical analysis, non-parametric correlations between variables were performed. Thirty-nine patients have been included in the study since January 2007. In SAH patients there are increasing perfusion abnormalities as the severity of the bleeding increases. The most affected perfusion parameters are TTP and MTT, as they significantly increase with the clinical severity of the bleeding and the total volume of bleeding (P < 0.01, Spearman's Rho). When average MTT time is increased over 5.9 s there is a 20-fold (95% CI = 2.1-182) risk of poor outcome. All patients presenting this MTT time suffered from DCI. This value has a positive predictive value of 100% for DCI and 90% for a poor outcome. SAH causes cerebral blood flow abnormalities even in the acute phase of the illness, consisting mainly of an increase in circulation times (TTP and MTT), which are correlated with the severity of the bleeding.