Aberrant Origin of the Distal Anterior Cerebral Artery from the Middle Cerebral Artery Related to Obstruction of Bilateral Proximal Anterior Cerebral Arteries: A Case Report.

BACKGROUND: Aberrant origin of the distal anterior cerebral artery (ACA) arising from the middle cerebral artery (MCA) is extremely rare. CASE PRESENTATION: A 74-year-old woman with a sudden onset of left-sided weakness was admitted to the emergency department. Angiography revealed an unusual course of the distal ACA originating from the MCA with bilateral obstruction of the proximal segment of the ACA and simultaneous occurrence of infarction in the ACA and MCA territories. CONCLUSION: Knowledge of a rare vascular variation or anomaly could help understand brain imaging, which has an unusual involvement of vascular territories, performed in patients with acute ischemic stroke.

Comparison of imaging findings on three-dimensional black-blood enhanced MR imaging between intracranial atherosclerotic occlusion and thrombotic occlusion.

PURPOSE: The purpose of this study was to compare the imaging findings on three-dimensional (3D) black-blood (BB) contrast-enhanced MR imaging between intracranial atherosclerotic occlusion (IAO) and thrombotic occlusion (TO) of the middle cerebral artery (MCA) territory. MATERIALS AND METHODS: From August 2020 to September 2021, we retrospectively reviewed the BB contrast-enhanced MR imaging of patients visiting the emergency room for evaluation of acute ischemic stroke. In total, 77 patients with complete occlusion of the MCA territory on 3D BB contrast-enhanced MR imaging and cerebral angiography were enrolled in this study. We divided the IAO and TO groups according to occlusion causes based on angiography findings. RESULTS: Of 77 patients, 44 (57.1%) had an IAO in the M1 and M2 and 33 had a TO. Lesion length contrast enhancement (CE) in patients with a TO was significantly longer than that in patients with an IAO (18.95 mm [IQR: 20.91] vs. 7.1 mm [8.92], p <0.001). Overall, 38 (39.4%) patients showed a disconnection of CE on 3D BB contrast-enhanced MR imaging, and 35 showed CE before and after the stenotic or thrombotic lesion. Symptomatic lesions on diffusion-weighted imaging in the TO group were significantly higher than that of the IAO group (97.0% vs, 70.5%, p = 0.003). CONCLUSION: The long segment CE on 3D BB contrast-enhanced MR imaging was related to TO of MCA. CE before and after a stenotic or thrombotic lesion is a common finding on 3D BB contrast-enhanced MR imaging.

The role of vessel wall imaging in determining the best treatment approach for coexisting aneurysms and subarachnoid hemorrhage.

PURPOSE: The purpose of this study was to investigate the utilization of gadolinium enhancement on vessel wall imaging (VWI) in treatment decision-making for patients with two intracranial aneurysms presenting as a subarachnoid hemorrhage (SAH). MATERIALS AND METHODS: We prospectively performed VWI using 3.0-Tesla (3T) magnetic resonance imaging (MRI) before treatment with endovascular coiling or surgical clipping in patients with one or two intracranial aneurysms. The VWI protocol includes three different scans: black blood (BB) T1-weighted, BB T2-weighted, TOF axial, and BB contrast-enhanced T1-weighted imaging. We analyzed all aneurysm ruptures both with and without gadolinium enhancement of the aneurysm wall. RESULTS: Thirty-eight patients with 48 aneurysms were enrolled in this study. Of these patients, 28 had a single aneurysm (15 ruptured and 13 unruptured), and 10 had two aneurysms and SAH (9 patients with two aneurysms and 1 patient with three aneurysms). Of the 15 single ruptured aneurysms, 12 (80.0%) showed positive wall enhancement, whereas 2 of the 13 single unruptured aneurysms (15.4%) demonstrated positive wall enhancement. Ten patients with SAH and two aneurysms showed wall enhancement of a single aneurysm, and these aneurysms were treated first. CONCLUSION: Gadolinium enhancement of an aneurysm wall on MRI was associated with aneurysm rupture. In patients with two aneurysms and SAH, this type of imaging can play an important role in determining the order of aneurysm treatment.

Prevalence of Symptomatic Nonstenotic Carotid Disease Using Simultaneous Non-Contrast Angiography and Intraplaque Hemorrhage Imaging for MR Screen Protocol.

Background: To determine the prevalence of symptomatic nonstenotic carotid disease (SyNC) using simultaneous non-contrast angiography and intraplaque hemorrhage (SNAP) imaging for patients with acute stroke as an MR screen protocol and to assess imaging findings of carotid plaques. Patients and Methods: From May 2020 to October 2021, 2459 patients with suspected acute neurological symptoms were evaluated with brain diffusion-weighted imaging (DWI) and carotid SNAP imaging. We analyzed the degree of stenosis and intraplaque hemorrhage (IPH) using SNAP imaging. Prevalence of SyNC and risk factors for stroke in patients with SyNC were determined. We performed subgroup multivariate analysis between SyNC and other etiologies of stroke (non-SyNC). Results: Of 4608 carotid arteries in 2304 patients enrolled in this study, 454 (9.9%) plaques (both lesions in 128 patients) were found on SNAP imaging. Of these plaques, 353 (77.8%) showed stenosis of <50%. Of plaques with <50% stenosis, 47 (13.3%) patients had a territorial acute focal infarction. Seventeen (36.2%) were classified with embolic stroke of undetermined source (ESUS) and SyNC. High maximal wall thickness and carotid IPH were identified as influencing factors for SyNC. Conclusion: For patients with <50% stenosis and territorial infarction, SyNC is a relatively important source of stroke. Especially, high maximal wall thickness and carotid IPH are important risk factors for SyNC.

Acute Distal Vertebral Artery Occlusion in Patients with Asymmetrical Vertebral Artery Geometry: Role of Black-Blood-Enhanced MR Imaging.

Background: The purpose of this study was to evaluate the diagnostic value of contrast enhancement in a unilateral distal vertebral artery (VA) using black blood (BB)-enhanced magnetic resonance (MR) imaging in patients with acute neurological symptoms and asymmetrical VA geometry. Methods: From January 2020 to August 2021, we retrospectively analyzed BB-contrast-enhanced MR imaging and MR angiography (MRA) findings in stroke patients visiting the emergency room for an evaluation of acute neurological symptoms. We classified four patterns according to asymmetrical VA geometry using MRA and contrast enhancement using BB-enhanced MR imaging: type 1 = enhanced VA + no visualization of VA, type 2 = enhanced VA + hypoplastic VA, type 3 = non-enhanced VA + hypoplastic VA, or type 4 = non-enhanced VA + no visualization of VA. Results: In total, 288 patients (type 1 = 65, type 2 = 17, type 3 = 130, type 4 = 76) were enrolled in this study. Of these patients, 82 (28.5%) showed contrast enhancement of a unilateral distal VA on BB-enhanced MR imaging, and 51 (17.8%) had positive findings on diffusion-weighted imaging (DWI) in the ipsilateral medulla, pons, or posterior inferior cerebellar artery (PICA) territory. The contrast enhancement of a unilateral distal VA using BB-enhanced MR imaging demonstrated a significantly higher prevalence in patients with acute infarction on DWI (50.0% vs. 4.9%, p < 0.001). Conclusions: The contrast enhancement of a unilateral distal VA on BB-enhanced MR imaging is associated with acute infarction of the medulla, pons, or PICA territory and suggests acute occlusion of a distal VA.

The comprehensive comparison of imaging sign from CT angiography and noncontrast CT for predicting intracranial hemorrhage expansion: A comparative study.

Expansion of intracranial hemorrhage (ICH) is an important predictor of poor clinical outcomes. Various imaging markers on non-contrast computed tomography (NCCT) or computed tomographic angiography (CTA) have been reported as predictors of ICH expansion. We aimed to compare the associations between various CT imaging markers and ICH expansion. Patients with spontaneous ICH who underwent initial NCCT, CTA, and subsequent NCCT between January 2016 and December 2019 were retrospectively identified. ICH expansion was defined as a volume increase of > 33% or > 6 mL. We analyzed the presence of imaging markers such as the black hole sign, blend sign, island sign, or swirl sign on initial NCCT or spot sign on CTA. An alternative free-response receiver operating characteristic curve analysis was performed using a 4-point scoring system based on the consensus of the reviewers. The predictive value of each marker was assessed using univariate and multivariate logistic regression analyses. A total of 250 patients, including 60 (24.0%) with ICH expansion, qualified for the analysis. Among the patients with spontaneous ICH, 118 (47.2%) presented with a black hole sign, 52 (20.8%) with a blend sign, 93 (37.2%) with an island sign, 79 (31.6%) with a swirl sign, and 56 (22.4%) with a spot sign. In univariate logistic regression, the initial ICH volume (P = .038), initial intraventricular hemorrhage (IVH) presence (P < .001), swirl sign (P < .001), and spot sign (P < .001) were associated with ICH expansion. Multivariate analysis confirmed that the presence of initial IVH (odds ratio, 4.111; P = .002) and spot sign (odds ratio, 109.5; P < .001) were independent predictors of ICH expansion. Initial ICH volume, IVH, swirl sign, and spot sign are associated with ICH expansion. The presence of spot signs and IVH were independent predictors of ICH expansion.

Differential Diagnosis of Intraplaque Hemorrhage and Dissection on High-Resolution MR Imaging in Patients with Focal High Signal of the Vertebrobasilar Artery on TOF Imaging.

PURPOSE: Intraplaque hemorrhage (IPH) and dissection in the vertebrobasilar artery (VBA) on time of flight (TOF) source imaging are seen as focal eccentric high-signal intensity. The purpose of this study is to identify IPH and dissection in the VBA using high-resolution magnetic resonance imaging (HR-MRI). METHODS: A total of 78 patients (VBA IPH: 55; dissection: 23) with focal high-signal intensity in the VBA on simultaneous non-contrast angiography and intraplaque hemorrhage (SNAP) of HR-MRI were included in this study. The focal high-signal intensity in the VBA on SNAP was defined as >200% than that of the adjacent muscle. We analyzed the signal intensity ratio (area of focal high signal intensity area/lumen) on TOF imaging and black blood (BB) T2-weighted imaging. RESULTS: The VBA IPH group was older than the dissection group and had more hypertension. Signal intensity of a false lumen in patients with dissection on TOF imaging was significantly higher than that of VBA IPH (p < 0.001). The signal intensity ratio between lumen and lesion on TOF imaging was significantly higher in the dissection group (p < 0.001). The signal intensity of a false lumen in patients with dissection on BB T2-weighted imaging was significantly lower than that of VBA IPH (p < 0.001). The signal intensity ratio between lumen and lesion on BB T2-weighted imaging was significantly higher in the VBA IPH group (p < 0.001). CONCLUSIONS: TOF imaging and BB T2-weighted imaging on HR-MRI in patients with focal eccentric high-signal intensity on TOF imaging can distinguish between VBA IPH and dissection.

One-step evaluation of intraplaque hemorrhage in the carotid artery and vertebrobasilar artery using simultaneous non-contrast angiography and intraplaque hemorrhage.

PURPOSE: To investigate the one-step detection of intraplaque hemorrhage (IPH) in the carotid artery (CA) and vertebrobasilar artery (VBA) using simultaneous non-contrast angiography and intraplaque hemorrhage (SNAP). METHODS: From January 2019 to March 2020, 1820 consecutive patients who visited our emergency room for evaluation of neurologic symptoms underwent brain MR imaging, including the SNAP sequence. SNAP imaging examined the coronal section from the CA to the VBA. IPH was defined as plaque in the CA and VBA with 200 % higher signal intensity on SNAP than in adjacent muscle in at least two consecutive slices. RESULTS: Of these patients, 360 (19.8 %) had carotid plaque (both sides = 141, 39.2 %; single side = 219, 61.8 %). Of patients with carotid plaque, 185 (51.4 %) had IPH. Of 141 patients with plaques on both sides, 35 (24.8 %) had bilateral IPH. In total, 73 (4.0 %) patients had VBA IPH (30 with carotid plaque, 43 without carotid plaque). In addition, 18 (1.0 %) patients had carotid IPH and VBA IPH. Maximal wall thickness was significantly higher in the carotid IPH groups (4.5 ± 0.1 vs. 4.1 ± 0.1, p = 0.009). Prevalence of high grade stenosis (>70 %) was significantly higher in the carotid IPH group (17.5 % vs. 6.2 %, p < 0.001). CONCLUSIONS: SNAP imaging can be evaluated with a one-step examination of CA and VBA IPH.

Comparison of Hemodynamic Visualization in Cerebral Arteries: Can Magnetic Resonance Imaging Replace Computational Fluid Dynamics?

A multimodality approach was applied using four-dimensional flow magnetic resonance imaging (4D flow MRI), time-of-flight magnetic resonance angiography (TOF-MRA) signal intensity gradient (SIG), and computational fluid dynamics (CFD) to investigate the 3D blood flow characteristics and wall shear stress (WSS) of the cerebral arteries. TOF-MRA and 4D flow MRI were performed on the major cerebral arteries in 16 healthy volunteers (mean age 34.7 ± 7.6 years). The flow rate measured with 4D flow MRI in the internal carotid artery, middle cerebral artery, and anterior cerebral artery were 3.8, 2.5, and 1.2 mL/s, respectively. The 3D blood flow pattern obtained through CFD and 4D flow MRI on the cerebral arteries showed reasonable consensus. CFD delivered much greater resolution than 4D flow MRI. TOF-MRA SIG and CFD WSS of the major cerebral arteries showed reasonable consensus with the locations where the WSS was relatively high. However, the visualizations were very different between TOF-MRA SIG and CFD WSS at the internal carotid artery bifurcations, the anterior cerebral arteries, and the anterior communicating arteries. 4D flow MRI, TOF-MRA SIG, and CFD are complementary methods that can provide additional insight into the hemodynamics of the human cerebral artery.

Strong enhancement on three-dimensional black-blood enhanced magnetic resonance imaging: Comparison intracranial stenosis and complete occlusion.

PURPOSE: The purpose of this study was to evaluate contrast enhancement patterns on three-dimensional (3D) black blood (BB) contrast-enhanced magnetic resonance (MR) imaging in patients with occlusion or stenosis of the anterior intracranial artery. MATERIALS AND METHODS: From January 2018 to January 2020 we retrospectively reviewed stroke 3D BB contrast-enhanced MR imaging and MR angiography findings of patients visiting the emergency room for evaluation of non-traumatic brain lesions. In total, 92 patients with positive findings on 3D BB contrast-enhanced MR imaging were enrolled in this study. We divided the enrolled group according to whether MR angiography findings suggested complete occlusion, high-grade stenosis (51-99 %), or low-grade stenosis (10-50 %). RESULTS: Of 92 patients, 33 had complete occlusion in the anterior intracranial artery, 36 had high-grade stenosis, and 23 had low-grade stenosis. The complete occlusion group showed concentric and segmental enhancement on 3D BB enhanced MR imaging. The high-grade stenosis group frequently showed concentric and focal enhancement. The high signal vessel sign in the complete occlusion group was significantly higher compared to the stenosis group (p < 0.001). The contrast ratio between the lesion and pituitary gland in the occlusion group was significantly lower than that of the stenosis group (p < 0.05). CONCLUSION: Bright contrast enhancement and high signal vessel sign on 3D BB contrast enhanced MR imaging are related to contrast stagnation of the occlusion site and slow flow of a distal portion of the occlusion site.

Characteristics of Symptomatic Basilar Artery Stenosis Using High-Resolution Magnetic Resonance Imaging in Ischemic Stroke Patients.

AIM: Arterial narrowing associated with the progression of atherosclerosis leads to serious conditions such as stroke, coronary artery disease, or even death. High-resolution magnetic resonance imaging (HR-MRI) is better for detecting arterial wall status and discriminating tissue characteristics than conventional imaging. We used HR-MRI to investigate the frequency of patients with basilar artery (BA) stenosis observed distinctively on routine angiography and identify the clinical features associated with this imaging. We analyzed the nature of the vessel wall causing the basal artery stenosis by HR-MRI, and related clinical factors. METHODS: Patients with BA stenosis underwent HR-MRI. The association between atherosclerosis (with or without intraplaque hemorrhage [IPH]) and dissection was analyzed. High signal intensity within a BA plaque on magnetization-prepared rapid acquisition with gradient echo was defined as an area with a signal intensity ＞200% that of the adjacent muscle. RESULTS: Fifteen patients were diagnosed with BA dissection on HR-MRI. IPH was identified in 14 patients. Patients with BA plaque with IPH were older and had higher prevalence of hypertension and hyperlipidemia than the other patients. The frequencies of alcohol drinking and number of current smokers were higher in the dissection group than in the other groups. Hyperlipidemia was identified as an influencing factor for IPH development in atherosclerotic plaque. Young age was identified as the influencing factor for the occurrence of BA dissection. CONCLUSIONS: The etiology of stenosis or occlusion was unclear until the development of HR-MRI. With HR-MRI, stroke etiology is better understood, and factors affecting each etiology can be identified. Further studies that clarify the etiology of posterior circulation stroke are required.

Repeated Endovascular Thrombectomy in Patients with Acute Ischemic Stroke in a Single Center.

BACKGROUND: Patients with acute ischemic stroke treated with endovascular thrombectomy may be treated with repeat endovascular thrombectomy (rEVT) in case of recurrent large vessel occlusion (LVO). The purpose of this study is to report the frequency, timing, and outcomes of rEVT in a single center. MATERIALS AND METHODS: We retrospectively reviewed our databases for anterior or posterior circulation rEVT cases. Patient characteristics, procedural data, and functional outcomes (modified Rankin scale at 90 days) were analyzed. Early and late recurrence of stroke was divided at 30 days. RESULTS: Of 1025 patients treated between January 2011 and January 2020, 23 (2.2%) underwent rEVT. The median time between the first and second procedure was 185 days; 7 (30.4%) patients were re-treated within 30 days. Eleven patients (47.8%) had different occlusion sites between the two procedures. Good clinical outcome of patients with late ipsilateral recurrence was significantly higher than that of patients with late contralateral recurrence (83.3% vs. 16.7, p = 0.027). Overall good functional outcome after the second procedure was 43.5% (10/23). Overall good functional outcome of early and late recurrence groups were similar (57.1% vs. 37.5%, p = 0.650). One patient died due to an underlying cardiac problem. CONCLUSION: rEVT can be performed in patients with recurrent stroke of LVO. Ipsilateral recurrence of stroke was associated with good clinical outcome after rEVT.

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Endovascular treatment of acute carotid atherosclerotic tandem occlusions: Predictors of clinical outcomes as technical aspects and location of tandem occlusions.

BACKGROUND: We aimed to analyze angiographic and clinical outcomes according to the sequence of treatment (antegrade versus retrograde) in patients with acute ischemic stroke caused by tandem extracranial cervical carotid and intracranial large vessel occlusion. MATERIALS AND METHODS: All eligible tandem occlusion patients from April 2012 to March 2019 undergoing carotid artery stenting (CAS) simultaneously with intracranial endovascular thrombectomy (EVT) were retrospectively reviewed. After dividing into 2 groups according to the treatment sequence for tandem lesions (antegrade, CAS first; retrograde, intracranial EVT first), baseline data, immediate angiographic results, and clinical outcome for eligible patients were analyzed and compared. In addition, the same analysis was performed after dividing into 3 groups based on the location of intracranial lesions (T-zone, M1, M2). RESULTS: A total of 76 patients with a tandem occlusion (mean age, 71.7 y± 11.1) were treated with CAS and intracranial EVT. The rate of successful recanalization (TICI 2BC) was 83% (63/76), and favorable functional outcome was achieved in 49% (37/76). When comparing antegrade and retrograde methods, there were no differences in baseline data and angiographic or clinical outcomes. Favorable functional outcome was significantly higher in the M2 occlusion group (P=0.011). In multivariate analysis, baseline NIHSS <15, age <80, and M2 occlusion were revealed as independent predictors of favorable outcome. CONCLUSION: Different endovascular sequences for tandem extracranial cervical carotid and intracranial large vessel occlusion do not affect angiographic or functional outcomes. Intracranial M2 occlusion, age, and baseline NIHSS were independent predictors of good clinical outcome at 3 months.

Hemodynamic Changes in the Carotid Artery after Infusion of Normal Saline Using Computational Fluid Dynamics.

PURPOSE: To study the effect of the infusion of normal saline on hemodynamic changes in healthy volunteers using computational fluid dynamics (CFD) simulation. METHODS: Eight healthy subjects participated and 16 carotid arteries were used for the CFD analysis. A one-liter intravenous infusion of normal saline was applied to the participants to observe the hemodynamic variations. Blood viscosity was measured before and after the injection of normal saline to apply the blood properties on the CFD modeling. Blood viscosity, shear rate, and wall shear stress were visually and quantitatively shown for the comparison between before and after the infusion of normal saline. Statistical analyses were performed to confirm the difference between the before and after groups. RESULTS: After the infusion of normal saline, decreased blood viscosity was observed in the whole carotid artery. At the internal carotid artery, the recirculation zone with low intensity was found after the injection of normal saline. Increased shear rate and reduced wall shear stress was observed at the carotid bifurcation and internal carotid artery. The hemodynamic differences between before and after groups were statistically significant. CONCLUSIONS: The infusion of normal saline affected not only the overall changes of blood flow in the carotid artery but also the decrease of blood viscosity.

Change in basilar artery length and bending according to aging and vertebral artery dominance: A longitudinal study.

This study aimed to investigate the basilar artery (BA) geometric changes in a longitudinal study. 154 subjects with normal vertebrobasilar arterial systems on magnetic resonance angiography were assigned into two groups: 1) non-dominant vertebral artery (VA) and 2) VA dominance. We defined the dominant VA as either that the VA is 3 millimeters larger in diameter or the VA is connected to BA in a more straight angle. BA imaging was segmented to obtain BA bending length (BABL) and BA length (BAL). A mixed model ANOVA was conducted to investigate the impact of aging and VA dominance on the change of BABL and BAL after 123.6 ± 16.2 months. There was a significant main effect of VA dominance on the change of BABL after about 10 years, F (1,152) = 39.78, p < 0.01. On the other hand, there was a significant main effect of aging on the change of BAL during the same period of time, F (1,152) = 6.64, p = 0.01. Most subjects had an opposite directional relationship between the dominant VA and BA bending (71.3%; p < 0.01). Our study supported the hypothesis that the bending of the BA depends on the dominance of the VA, whereas the increased length of the BA depends on aging.

Size-Dependent Distribution of Patient-Specific Hemodynamic Factors in Unruptured Cerebral Aneurysms Using Computational Fluid Dynamics.

PURPOSE: To analyze size-dependent hemodynamic factors [velocity, shear rate, blood viscosity, wall shear stress (WSS)] in unruptured cerebral aneurysms using computational fluid dynamics (CFD) based on the measured non-Newtonian model of viscosity. METHODS: Twenty-one patients with unruptured aneurysms formed the study cohort. Patient-specific geometric models were reconstructed for CFD analyses. Aneurysms were divided into small and large groups based on a cutoff size of 5 mm. For comparison between small and large aneurysms, 5 morphologic variables were measured. Patient-specific non-Newtonian blood viscosity was applied for more detailed CFD simulation. Quantitative and qualitative analyses of velocity, shear rate, blood viscosity, and WSS were conducted to compare small and large aneurysms. RESULTS: Complex flow patterns were found in large aneurysms. Large aneurysms had a significantly lower shear rate (235 ± 341 s-1)) than small aneurysms (915 ± 432 s-1) at peak-systole. Two times higher blood viscosity was observed in large aneurysms compared with small aneurysms. Lower WSS was found in large aneurysms (1.38 ± 1.36 Pa) than in small aneurysms (3.53 ± 1.22 Pa). All the differences in hemodynamic factors between small and large aneurysms were statistically significant. CONCLUSIONS: Large aneurysms tended to have complex flow patterns, low shear rate, high blood viscosity, and low WSS. The hemodynamic factors that we analyzed might be useful for decision making before surgical treatment of aneurysms.

Correlation between Spot Sign and Intracranial Hemorrhage Expansion on Dual-Phase CT Angiography.

PURPOSE: Expansion of intracranial hemorrhage (ICH) is an important predictor of poor clinical outcome. ICH expansion can be predicted with a spot sign on computed tomographic angiography (CTA). We aimed to evaluate the correlation between spot signs on CTA and ICH expansion on dual-phase CTA. METHODS: Patients with spontaneous ICH between January 2017 and April 2019 who underwent an initial CT, dual-phase CTA, and a subsequent CT were retrospectively identified. ICH expansion was defined as volume growth of >33% or >6 mL. We analyzed the presence and change in size of the spot sign in the first phase and second phase CTA. Also, we divided the morphological status of the spot sign, such as a dot-like lesion or linear contrast extravasation, in the first and second phase CTA. RESULTS: A total of 206 patients, including 38 (18.5%) with ICH expansion and 45 (21.8%) with a spot sign, qualified for analysis. Of patients with a spot sign, 26 (57.8%) had ICH expansion on subsequent CT. Increased size of a spot sign in second-phase CTA was more frequent in the ICH expansion group than in the no-expansion group (96.2% vs. 52.6%, p < 0.001). First visualization of a spot sign in the second phase was more common in the no-expansion group than in the ICH expansion group (47.4% vs. 3.8%, p < 0.001). The morphological patterns of a spot sign between the two groups were not significantly different. CONCLUSION: Spot signs on dual-phase CTA have different sizes and morphological patterns. Increased size of a spot sign in the second phase of CTA can help identify patients at risk for ICH expansion.

Four-Dimensional Flow Magnetic Resonance Imaging for Assessment of Velocity Magnitudes and Flow Patterns in The Human Carotid Artery Bifurcation: Comparison with Computational Fluid Dynamics.

PURPOSE: Knowledge of the hemodynamics in the vascular system is important to understand and treat vascular pathology. The present study aimed to evaluate the hemodynamics in the human carotid artery bifurcation measured by four-dimensional (4D) flow magnetic resonance imaging (MRI) as compared to computational fluid dynamics (CFD). METHODS: This protocol used MRI data of 12 healthy volunteers for the 3D vascular models and 4D flow MRI measurements for the boundary conditions in CFD simulation. We compared the velocities measured at the carotid bifurcation and the 3D velocity streamlines of the carotid arteries obtained by these two methods. RESULTS: There was a good agreement for both maximum and minimum velocity values between the 2 methods for velocity magnitude at the bifurcation plane. However, on the 3D blood flow visualization, secondary flows, and recirculation regions are of poorer quality when visualized through the 4D flow MRI. CONCLUSION: 4D flow MRI and CFD show reasonable agreement in demonstrated velocity magnitudes at the carotid artery bifurcation. However, the visualization of blood flow at the recirculation regions and the assessment of secondary flow characteristics should be enhanced for the use of 4D flow MRI in clinical situations.

Quantification of Carotid Intraplaque Hemorrhage: Comparison between Manual Segmentation and Semi-Automatic Segmentation on Magnetization-Prepared Rapid Acquisition with Gradient-Echo Sequences.

PURPOSE: Carotid intraplaque hemorrhage (IPH) increases risk of territorial cerebral ischemic events, but different sequences or criteria have been used to diagnose or quantify carotid IPH. The purpose of this study was to compare manual segmentation and semi-automatic segmentation for quantification of carotid IPH on magnetization-prepared rapid acquisition with gradient-echo (MPRAGE) sequences. METHODS: Forty patients with 16-79% carotid stenosis and IPH on MPRAGE sequences were reviewed by two trained radiologists with more than five years of specialized experience in carotid plaque characterization with carotid plaque MRI. Initially, the radiologists manually viewed the IPH based on the MPRAGE sequence. IPH volume was then measured by three different semi-automatic methods, with high signal intensity 150%, 175%, and 200%, respectively, above that of adjacent muscle on the MPRAGE sequence. Agreement on measurements between manual segmentation and semi-automatic segmentation was assessed using the intraclass correlation coefficient (ICC). RESULTS: There was near-perfect agreement between manual segmentation and the 150% and 175% criteria for semi-automatic segmentation in quantification of IPH volume. The ICC of each semi-automatic segmentation were as follows: 150% criteria: 0.861, 175% criteria: 0.809, 200% criteria: 0.491. The ICC value of manual vs. 150% criteria and manual vs. 175% criteria were significantly better than the manual vs. 200% criteria (p < 0.001). CONCLUSIONS: The ICC of 150% and 175% criteria for semi-automatic segmentation are more reliable for quantification of IPH volume. Semi-automatic classification tools may be beneficial in large-scale multicenter studies by reducing image analysis time and avoiding bias between human reviewers.