Effects of multiphase versus single-phase CT angiography for the detection of distal cerebral vessel occlusion.

PURPOSE: The goal of this study was to determine whether the benefits of multiphase CTA (mCTA) over single-phase CTA (sCTA) for the detection of proximal cerebrovascular occlusions similarly extend to the distal cerebral vasculature. METHODS: Four attending radiologists, two neuroradiologists and two emergency radiologists, contributed as readers to this retrospective study. For each reader, two sessions were conducted, one using sCTA and one using mCTA. During each session, the reader interpreted the studies of 104 patients who underwent imaging for suspicion of acute ischemic stroke, resulting in a total of 832 interpretations. Changes in diagnostic accuracy, time to render final decision, and reported levels of reader confidence were quantitatively assessed. Further analysis comparing the effects for neuroradiologists versus emergency radiologists was additionally conducted. RESULTS: Using mCTA resulted in a significant 5.0% absolute increase in sensitivity (91.6% vs. 96.6%, p = .004) and an insignificant increase in specificity (99.5% vs. 99.7%, p = .39). A significant reduction in reading time (66.7 s vs. 59.6 s, p = .001) and an increase in diagnostic confidence (2.26 vs. 2.58, p < .001) were observed. Using sCTA, higher sensitivity was achieved by neuroradiologists than emergency radiologists (96.0% vs. 86.9%, p = .002); using mCTA resulted in an absolute increase in sensitivity of 0.9% (97.4%, p = .44) for neuroradiologists and 9.6% (96.5%, p < .001) for emergency radiologists, eliminating significant differences between the groups (p = 0.57). CONCLUSION: The use of mCTA results in increased sensitivity and negative predictive value, decreased reading time, increased diagnostic confidence, and the elimination of differences in accuracy between neuroradiologists and emergency radiologists.

Single-phase CT angiography: collateral grade is independent of scan weighting.

PURPOSE: Collateral grading may vary on single-phase CTA (sCTA) depending on whether the CTA is arterial (A), arteriovenous (AV), or venous (V) weighted. We studied the impact of sCTA weighting on collateral grading using the Tan, MAAS, and Menon methods, and their ability to predict infarct and clinical outcome hypothesizing that AV-weighted sCTA should better predict these outcomes. METHODS: Multicenter retrospective analysis of 212 patients undergoing baseline CTP/sCTA. sCTA weighting was determined by comparing ICA to torcula AV ratios with those from concomitant CTP time-density curves at peak arterial or venous contrast attenuation. A generalized linear mixed model investigated the predictive value for infarct volume or 90-day mRS of the three collateral scores stratified by sCTA weighting and adjusting for age, sex, clot burden score (CBS), and NIHSS. Bayesian information criterion (BIC) differences were calculated between the null and fitted models. RESULTS: Mean age, baseline median NIHSS, ASPECTS, and onset to treatment time were 69.89 ± 14.45, 13 (6-18), 10 (8-10), and 128 (66-181) minutes. sCTA scans were AV-weighted in 137/212 (65%) and A-weighted in 73 (34%). No association was demonstrated between sCTA weighting, hospital site, and sCTA technique. All collateral scores were related to infarct volume irrespective of sCTA weighting, with greatest fit with the regional leptomeningeal score (BIC 18.29, p = 0.0001). No association was shown between sCTA weighting, collateral grade, and clinical outcome. CONCLUSION: sCTA weighting did not significantly impact collateral grade using three common collateral scores or their ability to predict final infarct.

Single-Phase Versus Multiphase CT Angiography in Middle Cerebral Artery Clot Detection-Benefits for Less Experienced Radiologists and Neurologists.

OBJECTIVES: CT angiography (CTA) is recommended as a standard of stroke imaging. We investigated accuracy and precision of standard or single-phase CTA as compared with novel technique or multiphase CTA in clot detection in the middle cerebral artery. METHODS: Twenty single-phase CTA and twenty multiphase CTA with prevailing M2 occlusion were assessed by 10 radiologists and 10 neurologists blinded to clinical information (7 less experienced and 3 experienced). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated as compared with reading by two seniors. Reliability was calculated using Krippendorff's alpha (K-alpha). RESULTS: Sensitivity, specificity, PPV, and NPV of single-phase CTA compared with multiphase CTA for M2 clot presence were, respectively, .86, .75, .90, and .67 versus .88, .82, .92, and .72. For secondary or distal clots, sensitivity, specificity, PPV, and NPV of single-phase CTA compared with multiphase CTA were .41, .83, .50, and .78 versus .65, .77, .71, and .67. Agreement increased significantly in favor of multiphase CTA for detection of primary clots from moderate (.43) to substantial (.65) in less experienced radiologists and from slight (.10) to moderate (.30) in less experienced neurologists. Agreement significantly increased for distal or secondary clot detection in favor of multiphase CTA from fair (.24) to moderate (.49) in experienced radiologists and from slight (.12) to moderate (.46) in experienced neurologists. CONCLUSIONS: Multiphase CTA is a reliable imaging tool in M2 clot detection and might represent a beneficial imaging tool in clot detection for less experienced physicians.

Segmentation of Portal Vein in Multiphase CTA Image Based on Unsupervised Domain Transfer and Pseudo Label.

BACKGROUND: Clinically, physicians diagnose portal vein diseases on abdominal CT angiography (CTA) images scanned in the hepatic arterial phase (H-phase), portal vein phase (P-phase) and equilibrium phase (E-phase) simultaneously. However, existing studies typically segment the portal vein on P-phase images without considering other phase images. METHOD: We propose a method for segmenting portal veins on multiphase images based on unsupervised domain transfer and pseudo labels by using annotated P-phase images. Firstly, unsupervised domain transfer is performed to make the H-phase and E-phase images of the same patient approach the P-phase image in style, reducing the image differences caused by contrast media. Secondly, the H-phase (or E-phase) image and its style transferred image are input into the segmentation module together with the P-phase image. Under the constraints of pseudo labels, accurate prediction results are obtained. RESULTS: This method was evaluated on the multiphase CTA images of 169 patients. The portal vein segmented from the H-phase and E-phase images achieved DSC values of 0.76 and 0.86 and Jaccard values of 0.61 and 0.76, respectively. CONCLUSION: The method can automatically segment the portal vein on H-phase and E-phase images when only the portal vein on the P-phase CTA image is annotated, which greatly assists in clinical diagnosis.

Using Deep-Learning-Based Artificial Intelligence Technique to Automatically Evaluate the Collateral Status of Multiphase CTA in Acute Ischemic Stroke.

BACKGROUND: Collateral status is an important predictor for the outcome of acute ischemic stroke with large vessel occlusion. Multiphase computed-tomography angiography (mCTA) is useful to evaluate the collateral status, but visual evaluation of this examination is time-consuming. This study aims to use an artificial intelligence (AI) technique to develop an automatic AI prediction model for the collateral status of mCTA. METHODS: This retrospective study enrolled subjects with acute ischemic stroke receiving endovascular thrombectomy between January 2015 and June 2020 in a tertiary referral hospital. The demographic data and images of mCTA were collected. The collateral status of all mCTA was visually evaluated. Images at the basal ganglion and supraganglion levels of mCTA were selected to produce AI models using the convolutional neural network (CNN) technique to automatically predict the collateral status of mCTA. RESULTS: A total of 82 subjects were enrolled. There were 57 cases randomly selected for the training group and 25 cases for the validation group. In the training group, there were 40 cases with a positive collateral result (good or intermediate) and 17 cases with a negative collateral result (poor). In the validation group, there were 21 cases with a positive collateral result and 4 cases with a negative collateral result. During training for the CNN prediction model, the accuracy of the training group could reach 0.999 ± 0.015, whereas the prediction model had a performance of 0.746 ± 0.008 accuracy on the validation group. The area under the ROC curve was 0.7. CONCLUSIONS: This study suggests that the application of the AI model derived from mCTA images to automatically evaluate the collateral status is feasible.

Determinants of cerebral collateral circulation in acute ischemic stroke due to large vessel occlusion.

Introduction: Cerebral collateral circulation has a central role in ischemic stroke pathophysiology, and it is considered to correlate with infarct size, the success of reperfusion therapies, and clinical outcomes. Our aim was to study the factors influencing the development of collaterals in patients with acute ischemic stroke eligible for endovascular treatment. Materials and methods: We enrolled patients with acute ischemic stroke and large vessel occlusion of anterior circulation potentially eligible for endovascular treatment. Included patients performed multiphase CT angiography to assess collaterals that were graded by the Menon Grading Score. We investigated the associations between clinical factors and collaterals and tested independent associations with logistic (good vs. poor collaterals) and ordinal (collateral grade grouped, Menon 0-2, 3, 4-5) regression analysis adjusting for age, sex, stroke severity, and onset to CT time (OCTT). Results: We included 520 patients, the mean age was 75 (±13.6) years, 215 (41%) were men, and the median (IQR) NIHSS was 17 (11-22). Good collaterals were present in 323 (62%) patients and were associated with lower NIHSS (median 16 vs. 18; p < 0.001) and left hemisphere involvement (60% vs. 45%; p < 0.001), whereas previous stroke/TIA was more frequent in patients with poor collaterals (17 vs. 26%; p = 0.014). These results were confirmed in both logistic and ordinal regression analyses where good collaterals were associated with lower NIHSS (OR = 0.94; 95% CI = 0.91-0.96; cOR = 0.95; 95% CI = 0.92-0.97, respectively) and left hemisphere stroke (OR = 2.24; 95% CI = 1.52-3.28; cOR = 2.11; 95% CI = 1.46-3.05, respectively), while previous stroke/TIA was associated with poor collaterals (OR = 0.57; 95% CI = 0.36-0.90; cOR = 0.61; 95% CI = 0.40-0.94, respectively). Vascular risk factors, demographics, and pre-stroke treatments did not influence the collateral score. Discussion: The results of our study suggest that risk factors and demographics do not influence the development of collateral circles, except for a negative relation with previous ischemic events. We confirm an already reported observation of a possible protective effect of collaterals on tissue damage assuming NIHSS as its surrogate. The association between left hemispheric stroke and better collaterals deserves to be further explored. Further efforts are needed to identify the factors that favor the development of collaterals.

Matrix metallopeptidase 9 and placental growth factor may correlate with collateral status based on whole-brain perfusion combined with multiphase computed tomography angiography.

OBJECTIVE: The aim of this study was to find out the relationship between serum biomarkers and cerebral collateral status in acute ischemic stroke with cerebral large artery atherosclerosis. METHODS: We enrolled patients with ischemic stroke due to large artery atherosclerosis within 7 days of symptom onset, age 18-80 years, from August 2016 to December 2017. Twelve biomarkers representing different pathophysiological mechanisms were tested after admission. Whole-brain perfusion combined with multiphase computed tomography angiography was performed to assess cerebral collateral structure and function. RESULTS: Fifty-two patients completed the test of candidate biomarkers and recruited in this study. The mean age was 55.0 (11.1) years, 42 (80.8%) patients were male, 20 (38.5%) had poor collateral, 36 (69.2%) patients had anterior circulation stenosis or occlusion. Compared with poor collateral group, the level of MMP-9 (135,475.00 pg/ml vs. 103,612.00 pg/ml, p = 0.040) and PGF (5.75 pg/ml vs. 3.46 pg/ml, p = 0.046) was significantly higher in good collateral group. The adjusted OR (95%CI) of MMP-9 and PGF were 5.533 (1.10-27.74, p = 0.038), 7.73 (1.41-42.39, p = 0.018), respectively. sTie-2 level had a positive correlation with proportion of Tmax 4-6 (r = 0.302, p = 0.033) and HMW-KGN had negative correlation with proportion of Tmax 6-8 (r = -0.338, p = 0.02). After adjustment, the correlation of sTie-2 level and proportion of Tmax 4-6 was statistically significant (p = 0.003), and correlation of HMW-KGN and Tmax6-8 was not statistically significant (p = 0.056). DISCUSSION: Serum PGF and MMP-9 levels may correlate with collateral status based on MP-CTA in acute ischemic stroke patients with cerebral large artery atherosclerosis. Higher PGF and MMP-9 concentration associated with good collateral status.

Deep learning-based identification of acute ischemic core and deficit from non-contrast CT and CTA.

The accurate identification of irreversible infarction and salvageable tissue is important in planning the treatments for acute ischemic stroke (AIS) patients. Computed tomographic perfusion (CTP) can be used to evaluate the ischemic core and deficit, covering most of the territories of anterior circulation, but many community hospitals and primary stroke centers do not have the capability to perform CTP scan in emergency situation. This study aimed to identify AIS lesions from widely available non-contrast computed tomography (NCCT) and CT angiography (CTA) using deep learning. A total of 345AIS patients from our emergency department were included. A multi-scale 3D convolutional neural network (CNN) was used as the predictive model with inputs of NCCT, CTA, and CTA+ (8 s delay after CTA) images. An external cohort with 108 patients was included to further validate the generalization performance of the proposed model. Strong correlations with CTP-RAPID segmentations (r = 0.84 for core, r = 0.83 for deficit) were observed when NCCT, CTA, and CTA+ images were all used in the model. The diagnostic decisions according to DEFUSE3 showed high accuracy when using NCCT, CTA, and CTA+ (0.90±0.04), followed by the combination of NCCT and CTA (0.87±0.04), CTA-alone (0.76±0.06), and NCCT-alone (0.53±0.09).

Dynamic CT but Not Optimized Multiphase CT Angiography Accurately Identifies CT Perfusion Target Mismatch Ischemic Stroke Patients.

Imaging protocols for acute ischemic stroke varies significantly from center to center leading to challenges in research translation. We aimed to assess the inter-rater reliability of collateral grading systems derived from dynamic computed tomography angiography (CTA) and an optimized multiphase CTA and, to analyze the association of the two CTA modalities with CT perfusion (CTP) compartments by comparing the accuracy of dynamic CTA (dCTA) and optimized multiphase CTA (omCTA) in identifying CT perfusion (CTP) target mismatch patients. Acute ischemic stroke patients with a proximal large vessel occlusion who underwent whole brain CTP were included in the study. Collateral status were assessed using ASPECTS collaterals (Alberta Stroke Program Early CT Score on Collaterals) and ASITN/SIR collateral system (the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology) on dCTA and omCTA. Eighty-one patients were assessed, with a median ischemic core volume of 29 mL. The collateral assessment with ASPECTS collaterals using dCTA have a similar inter-rater agreement (K-alpha: 0.71) compared to omCTA (K-alpha: 0.69). However, the agreement between dCTA and CTP in classifying patients with target mismatch was higher compared to omCTA (Kappa, dCTA: 0.81; omCTA: 0.64). We found dCTA was more accurate than omCTA in identifying target mismatch patients with proximal large vessel occlusion.

Beyond the collaterals: Additional value of multiphase CTA in acute ischemic stroke evaluation.

PURPOSE: Multiphase computed tomography angiography (MP-CTA) is an innovative imaging tool that can give those managing acute ischemic stroke temporal information on degree and extent of pial collateral arterial filling in the affected brain. We sought to estimate the incidence of false-positive or -negative evaluation of the carotid bifurcation or intracranial thrombus on single-phase CTA (SP-CTA) compared with MP-CTA. MATERIAL AND METHODS: A single-center, retrospective consecutive review was conducted of imaging and clinical records of 150 patients in two months who presented with neurological symptoms with a National Institutes of Health Stroke Scale score ≥ 2 and who received an MP-CTA as part of their investigative work-up. The cohort consisted of 52.3% male and 47.7% female patients. Median individual age was 68 years (interquartile range 60-79). Extracranial and intracranial vessel images of the initial early arterial phase were evaluated and compared with late arterial and early venous phase images. RESULTS: In the cohort of 150 patients, in three patients (2%) SP-CTA would have led to an incorrect diagnosis and management without MP-CTA-acquired source imaging. The three scenarios represented differentiating a carotid string sign from internal carotid artery occlusion, determining the appearance and extent of thrombus in carotid T-occlusion, and differentiating slow flow and contrast mixing-related artifacts from intraluminal thrombus. CONCLUSIONS: In addition to improving assessment of collateral circulation in acute stroke patients, MP-CTA is also useful in assessing specific flow-related scenarios for which SP-CTA may give spurious results.

Implementation of multiphase computed tomography angiography in management of patients with acute ischemic stroke in clinical practice.

Multiphase computed tomography angiography (CTA) provides information on the status of major cranial arteries and extent of brain collateralization. The purpose of the study was to determine whether implementation of multiphase CTA in routine clinical practice was feasible, safe and useful. Patients with acute ischemic stroke (NIHSS ≥ 6) were included. Multiphase CTA was performed. Duration of performing multiphase CTA, inter-rater correlation and incidence of contrast-induced nephropathy (CIN) were studied. Infarct volume, incidence of hemorrhagic transformation, the rates of favorable outcome and death were compared between those with poor and intermediate-good collateralization. Multiphase CTA was performed in 108 patients. Mean duration on each multiphase CTA study was 4.8 min. Inter-rater reliability was intermediate-good (weighted kappa 0.7569, p < 0.001). CIN occurred in 3 patients (2.8%). There were no major intracranial/extracranial artery occlusion in 31 patients (29%) and there were severe stenosis or occlusions in 77 patients (71%). In the subgroup of patients with major artery severe stenosis or occlusion, 36 patients (36/77, 47%) had poor collateralization. Despite non-significant difference in acute treatment, the patients with poor collateralization had larger infarct (123 vs 35 cc, p < 0.001) and poorer outcomes (mean modified Rankin scale 3.86 vs 2.73, p = 0.011), while the differences in symptomatic hemorrhagic transformation (2.6 vs 7%, p = 0.385) and death rate (14 vs 12%, p = 0.825) were non-significant, as compared to those with intermediate-good collateralization. Multiphase CTA was feasible and safe. Besides the status of major arteries, multiphase CTA provided information on collateralization, which was associated with the size of infarct and clinical outcomes.

Fetal origin of posterior cerebral artery related to poor collaterals in patients with acute ischemic stroke.

The anatomic variation of Circle of Willis (CW) has been shown to have a great impact on its compensatory capacity during acute ischemic stroke. The purpose of the study was to evaluate the effect of variations in CW on collateral circulation in patients with acute ischemic stroke who had major artery occlusion. Patients with acute ischemic stroke within 4.5 h of stroke onset who had at least moderate severity of stroke (NIHSS ≥ 6), caused by major artery occlusion were included. Multiphase computed tomography angiography (CTA) was performed. Variations in CW on each patient were recorded and compared between those with poor collateral and intermediate-good collateral circulation. There were 66 patients. Mean NIHSS was 15. Forty patients had poor collateral circulation and 26 patients had intermediate-good collateral circulation. There were variations in CW: no visualized posterior communicating artery (PCOM) (31/66, 47%), fetal origin of posterior cerebral artery (25/66, 38%), one anterior cerebral artery, segment A1 (A1) hypoplasia or atresia (16/66, 24%), one PCOM (8/66, 12%), and complete CW (3/66, 5%). Fetal origin of posterior cerebral artery (PCA) was associated with poor collateral circulation (48% vs 23%, p-value = 0.046). This pilot study showed that the presence of fetal origin of PCA was associated with poor collateral circulation in patients with acute ischemic stroke caused by major artery occlusion.

Dynamic CTA in Native Kidneys Using a Multiphase CT Protocol-Potential of Significant Reduction of Contrast Medium.

RATIONALE AND OBJECTIVE: The objective of this study was to assess an optimized renal multiphase computed tomography angiography (MP-CTA) protocol regarding reduction of contrast volume. MATERIALS AND METHODS: Thirty patients underwent MP-CTA (12 phases, every 3.5 seconds, 80 kV/120 mAs) using 30 mL of contrast medium. The quality of MP-CTA was assessed quantitatively measuring vessel attenuation, image noise, and contrast-to-noise ratio. MP-CTA was evaluated qualitatively regarding depiction of vessels, cortex differentiation, and motion artifacts (grades 1-4, 1 = best). Mean effective radiation dose was registered. Results were compared to standard renal computed tomography angiography (CTA) (80 mL). Student t test was applied, if variables followed normal distribution. For other variables, nonparametric Mann-Whitney U test was used. RESULTS: All acquisitions were successfully performed, and no patient had to be excluded from the study. MP-CTA enabled high attenuation (aorta: 503 ± 91 HU, renal arteries: 450 ± 73 HU/456 ± 72 HU) at adequate image noise (13.7 ± 1.5) and good contrast-to-noise ratio (34.2 ± 10.2). Good attenuation of renal veins was observed (286 ± 43 HU/282 ± 42 HU). Arterial enhancement was significantly higher compared to renal CTA (aorta: 396 ± 90 HU, renal arteries: 331 ± 74 HU/333 ± 80 HU; P < .001). MP-CTA protocol enabled good image quality of renal arteries (1.5 ± 0.6) and veins (1.7 ± 0.6). Cortex differentiation and motion artifacts were ranked 1.8 ± 0.8 and 1.6 ± 0.8. The mean effective radiation dose was 9 mSv (MP-CTA). CONCLUSIONS: Compared to standard renal CTA, the renal MP-CTA enabled the significant reduction of contrast volume and simultaneously provided a significantly higher arterial attenuation.