Perfusion Collateral Index versus Hypoperfusion Intensity Ratio in Assessment of Collaterals in Patients with Acute Ischemic Stroke.

BACKGROUND AND PURPOSE: Perfusion-based collateral indices such as the perfusion collateral index and the hypoperfusion intensity ratio have shown promise in the assessment of collaterals in patients with acute ischemic stroke. We aimed to compare the diagnostic performance of the perfusion collateral index and the hypoperfusion intensity ratio in collateral assessment compared with angiographic collaterals and outcome measures, including final infarct volume, infarct growth, and functional independence. MATERIALS AND METHODS: Consecutive patients with acute ischemic stroke with anterior circulation proximal arterial occlusion who underwent endovascular thrombectomy and had pre- and posttreatment MRI were included. Using pretreatment MR perfusion, we calculated the perfusion collateral index and the hypoperfusion intensity ratio for each patient. The angiographic collaterals obtained from DSA were dichotomized to sufficient (American Society of Interventional and Therapeutic Neuroradiology [ASITN] scale 3-4) versus insufficient (ASITN scale 0-2). The association of collateral status determined by the perfusion collateral index and the hypoperfusion intensity ratio was assessed against angiographic collaterals and outcome measures. RESULTS: A total of 98 patients met the inclusion criteria. Perfusion collateral index values were significantly higher in patients with sufficient angiographic collaterals (P < .001), while there was no significant (P = .46) difference in hypoperfusion intensity ratio values. Among patients with good (mRS 0-2) versus poor (mRS 3-6) functional outcome, the perfusion collateral index of ≥ 62 was present in 72% versus 31% (P = .003), while the hypoperfusion intensity ratio of ≤0.4 was present in 69% versus 56% (P = .52). The perfusion collateral index and the hypoperfusion intensity ratio were both significantly predictive of final infarct volume, but only the perfusion collateral index was significantly (P = .03) associated with infarct growth. CONCLUSIONS: Results show that the perfusion collateral index outperforms the hypoperfusion intensity ratio in the assessment of collateral status, infarct growth, and determination of functional outcomes.

Cortical morphometric correlational networks associated with cognitive deficits in first episode schizophrenia.

Schizophrenia (SCZ) is a chronic cognitive and behavioral disorder associated with abnormal cortical activity during information processing. Several brain structures associated with the seven performance domains evaluated using the MATRICS (Measurement and Treatment Research to Improve Cognition in Schizophrenia) Consensus Cognitive Battery (MCCB) have shown cortical volume loss in first episode schizophrenia (FES) patients. However, the relationship between morphological organization and MCCB performance remains unclear. Therefore, in the current observational study, high-resolution structural MRI scans were collected from 50 FES patients, and the morphometric correlation network (MCN) using cortical volume was established to characterize the cortical pattern associated with poorer MCCB performance. We also investigated topological properties, such as the modularity, the degree and the betweenness centrality. Our findings show structural volume was directly and strongly associated with the cognitive deficits of FES patients in the precuneus, anterior cingulate, and fusiform gyrus, as well as the prefrontal, parietal, and sensorimotor cortices. The medial orbitofrontal, fusiform, and superior frontal gyri were not only identified as the predominant nodes with high degree and betweenness centrality in the MCN, but they were also found to be critical in performance in several of the MCCB domains. Together, these results suggest a widespread cortical network is altered in FES patients and that performance on the MCCB domains is associated with the core pathophysiology of SCZ.

Association between cortical volume and gray-white matter contrast with second generation antipsychotic medication exposure in first episode male schizophrenia patients.

This cross-sectional study examines the differences in cortical volume and gray-to-white matter contrast (GWC) in first episode schizophrenia patients (SCZ) compared to healthy control participants (HC) and in SCZ patients as a function of exposure to second generation antipsychotic medication. We hypothesize 1) SCZ exhibit regionally lower cortical volumes relative to HCs, 2) cortical volume will be greater with longer exposure to second generation antipsychotics prior to the MRI scan, and 3) lower GWC with longer exposure to second generation antipsychotics prior to the MRI scan, suggesting more blurring from greater intracortical myelin. To accomplish this, MRI scans from 71 male SCZ patients treated with second generation oral risperidone and 42 male HCs were examined. 3D T1-weighted MPRAGE images collected at 1.5T were used to estimate cortical volume and GWC by sampling signal intensity at 30% within the cortical ribbon. Average cortical volume and GWC were calculated and compared between SCZ and HC. Cortical volume and GWC in SCZ patients were correlated with duration of medication exposure for the time period prior to the scan. First-episode SCZ patients had significantly lower cortical volume compared to HCs in bilateral temporal, superior and rostral frontal, postcentral gyral, and parahippocampal regions. In SCZ patients, greater cortical volume was associated with (log-transformed) duration of second-generation antipsychotic medication exposure in bilateral precuneus, right lingual, and right superior parietal regions. Lower GWC was correlated with longer duration of medication exposure bilaterally in the superior frontal lobes. In summary, second generation antipsychotics may increase cortical volume and decrease GWC in first episode SCZ patients.

Fatal intracranial hemorrhage from brain AVM in a 7-week-old infant: case report and recent literature review.

Brain arteriovenous malformations (AVMs) are vascular abnormalities that typically present with spontaneous hemorrhage, seizure, or as a mass lesion. Pediatric brain AVMs are rarely diagnosed but carry a higher rate of rupture. We report a 7-week-old infant with rapid fatal intracranial hemorrhage from an undiagnosed brain. AVM confirmed at autopsy. Literature review on pediatric patients who had acute death caused by previously undiagnosed brain AVM from 1992 to 2018 revealed that cerebellum is the most frequent location of such AVMs, followed by thalamus. All the children had extensive intracranial hemorrhage that led to their deterioration despite surgical intervention.

pH-weighted molecular MRI in human traumatic brain injury (TBI) using amine proton chemical exchange saturation transfer echoplanar imaging (CEST EPI).

Cerebral acidosis is a consequence of secondary injury mechanisms following traumatic brain injury (TBI), including excitotoxicity and ischemia, with potentially significant clinical implications. However, there remains an unmet clinical need for technology for non-invasive, high resolution pH imaging of human TBI for studying metabolic changes following injury. The current study examined 17 patients with TBI and 20 healthy controls using amine chemical exchange saturation transfer echoplanar imaging (CEST EPI), a novel pH-weighted molecular MR imaging technique, on a clinical 3T MR scanner. Results showed significantly elevated pH-weighted image contrast (MTRasym at 3 ppm) in areas of T2 hyperintensity or edema (P < 0.0001), and a strong negative correlation with Glasgow Coma Scale (GCS) at the time of the MRI exam (R2 = 0.4777, P = 0.0021), Glasgow Outcome Scale - Extended (GOSE) at 6 months from injury (R2 = 0.5334, P = 0.0107), and a non-linear correlation with the time from injury to MRI exam (R2 = 0.6317, P = 0.0004). This evidence suggests clinical feasibility and potential value of pH-weighted amine CEST EPI as a high-resolution imaging tool for identifying tissue most at risk for long-term damage due to cerebral acidosis.

Quantitative Analysis of Neural Foramina in the Lumbar Spine: An Imaging Informatics and Machine Learning Study.

PURPOSE: To use machine learning tools and leverage big data informatics to statistically model the variation in the area of lumbar neural foramina in a large asymptomatic population. MATERIALS AND METHODS: By using an electronic health record and imaging archive, lumbar MRI studies in 645 male (mean age, 50.07 years) and 511 female (mean age, 48.23 years) patients between 20 and 80 years old were identified. Machine learning algorithms were used to delineate lumbar neural foramina autonomously and measure their areas. The relationship between neural foraminal area and patient age, sex, and height was studied by using multivariable linear regression. RESULTS: Neural foraminal areas correlated directly with patient height and inversely with patient age. The associations involved were statistically significant (P < .01). CONCLUSION: By using machine learning and big data techniques, a linear model encoding variation in lumbar neural foraminal areas in asymptomatic individuals has been established. This model can be used to make quantitative assessments of neural foraminal areas in patients by comparing them to the age-, sex-, and height-adjusted population averages.© RSNA, 2019Supplemental material is available for this article.

Selective middle cerebral artery occlusion in the rabbit: Technique and characterization with pathologic findings and multimodal MRI.

BACKGROUND: A reliable animal model of ischemic stroke is vital for pre-clinical evaluation of stroke therapies. We describe a reproducible middle cerebral artery (MCA) embolic occlusion in the French Lop rabbit characterized with multimodal MRI and histopathologic tissue analysis. NEW METHOD: Fluoroscopic-guided microcatheter placement was performed in five consecutive subjects with angiographic confirmation of MCA occlusion with autologous clot. Multimodal MRI was obtained prior to occlusion and up to six hours post after which repeat angiography confirmed sustained occlusion. The brain was harvested for histopathologic examination. RESULTS: Angiography confirmed successful MCA catheterization and durable (>6 h) MCA occlusion in all animals. There was increase of ADC volume over time and variable final core volume presumably related to individual variation in collateral flow. FLAIR hyperintensity indicative of cytotoxic edema and parenchymal contrast enhancement reflective of blood brain barrier disruption was observed over time. Tissue staining of the ischemic brain showed edema and structural alterations consistent with infarction. COMPARISON WITH EXISTING METHODS: This study describes a technique of selective catheterization and embolic occlusion of the MCA in the rabbit with MRI characterization of evolution of ischemia in the model. CONCLUSIONS: We demonstrate the feasibility of a rabbit model of embolic MCA occlusion with angiographic documentation. Serial MR imaging demonstrated changes comparable to those observed in human ischemic stroke, confirmed histopathologically.

Middle cerebral artery geometric features are associated with plaque distribution and stroke.

OBJECTIVE: We aimed to investigate the geometric features of the middle cerebral artery (MCA) and their relevance to plaque distribution and ischemic stroke. METHODS: We reviewed our institutional vessel wall imaging database. Patients with symptomatic MCA atherosclerosis, asymptomatic MCA atherosclerosis, or without MCA atherosclerosis were included. The MCA geometric features, including M1 segment shape and M1 curve orientation, were defined on magnetic resonance angiography. Plaque distribution and other plaque parameters were identified on vessel wall imaging. The association among MCA geometric features, plaque distribution, and ischemic stroke were analyzed. RESULTS: A total of 977 MCAs were analyzed (87 atherosclerotic symptomatic MCAs, 459 atherosclerotic asymptomatic MCAs, and 431 plaque-free MCAs). Overall, curved M1 segments were the predominant shape across all groups. In 91.1% of curved atherosclerotic MCAs, the plaque involved the inner wall of the curve. Plaque not involving the inner wall was shorter (p < 0.0001) and thinner (p = 0.005) compared to plaque involving the inner wall. Inferior plaque was observed in 39.9% of inferior-oriented M1 curves compared to 21.7% in non-inferior-oriented M1 curves (p < 0.0001). The absence of an inferior-oriented M1 curve (odds ratio 0.45, 95% confidence interval 0.27-0.77) and presence of superior plaque (odds ratio 2.67, 95% confidence interval 1.52-4.67) were independently associated with stroke after adjusting for plaque length and thickness, degree of stenosis, and remodeling ratio. CONCLUSIONS: MCA geometric features are associated with plaque distribution and stroke. Our findings provide insight into the vascular pathophysiology of MCA atherosclerosis.

A review of the diagnosis and management of vertebral basilar (posterior) circulation disease.

We have reviewed the English literature published in the last 70 years on Diseases of the Vertebral Basilar Circulation, or Posterior Circulation Disease (PCD). We have found that errors have been made in the conduct and interpretation of these studies that have led to incorrect approaches to the management of PCD. Because of the difficulty in evaluating the PC, the management of PCD has been incorrectly applied from anterior circulation disease (ACD) experience to PCD. PCD is a common form of stroke affecting 20-40% patients with stroke. Yet, the evidence is strong that the Anterior Circulation (AC) and Posterior Circulations (PC) differ in their pathology, in their clinical presentations, in the rapidity of development of symptoms, in optimal imaging methods, and in available treatments. There appears to be two categories of patients who present with PCD. The first, acute basilar artery occlusion has a more rapid onset. The diagnosis must be made quickly and if imaging proves a diagnosis of Basilar Artery Occlusion (BAO), the treatment of choice is Interventional removal of the basilar artery thrombosis or embolus. The second category of PCD and the most commonly seen PCD disease process presents with non-specific symptoms and early warnings of PCD that now can be related to ischemic events in the entire PC vessels. These warning symptoms and signs occur much earlier than those in the AC. IA angiography is still the gold standard of diagnosis and is superior in definition to MR and CT angiography which are commonly used as a convenient screening imaging tool to evaluate PCD but are both inferior to IA angiography in definition for lesions below 3-4 mm. In at least two reported studies 7T MR angiography appears superior to other imaging modalities and will become the gold standard of imaging of PCD in the future. Medical treatments applied to the ACD have not been proven of value in specific forms of PCD. Interventional therapy was promising but of unproven value in Randomized Controlled Trials (RCT) except for the treatment of Basilar Artery Occlusion (BAO). Surgical revascularization has been proved to be highly successful in patients, who are refractory to medical therapy. These studies have been ignored by the scientific community basically because of an incorrect interpretation of the flawed EC-IC Bypass Trial in 1985 as applying to all stroke patients. Moreover, the EC-IC Bypass Study did not include PCD patients in their study population, but the study results were extrapolated to patients with PCD without any scientific basis. This experience led clinicians to an incorrect bias that surgical treatments are of no value in PCD. Thus, incorrectly, surgical treatments of PCD have not been considered among the therapeutic possibilities for PCD. QMRA is a new quantitative MR technique that measures specific blood flow in extra and intracranial vessels. QMRA has been used to select those patients who may benefit from medical, or interventional, or surgical treatment for PCD based on flow determinations with a high success rate. QMRA accurately predicts the flows in many large and small vessels in the PC and AC and clearly indicates that both circulations are intimately related. From medical and surgical studies, the longer one waits for surgical treatment the higher the risk of a poor outcome results. This observation becomes obvious when the rapidity of development of PCD is compared with ACD. Recent advances in endovascular therapy in the treatment of acute basilar thrombosis is a clear sign that early diagnosis and treatment of PCD will reduce the morbidity and mortality of these diseases. In this review it is evident that there are multiple medical and surgical treatments for PCD depending upon the location of the lesion(s) and the collateral circulation demonstrated. It is clear that the AC and PC have significant differences. With the exception of the large population studies from Oxford England, the reported studies on the management of PCD in the literature represent small selected subsets of the universe of PC diseases, the information from which is not generalizable to the universe of PCD patients. At this point in the history of PCD, there are not large enough databases of similar patients to provide a basis for valid randomized studies, with the exception of the surgical studies. Thus, a high index of suspicion of the early warning symptoms of PCD should lead to a rapid individual clinical assessment of patients selecting those with PCD. Medical, interventional, and/or surgical treatments should be chosen based on knowledge presented in this review. Recording the results in a national Registry on a continuing basis will provide the data that may help advance the management of PCD based on larger data bases of well documented patient information to guide the selection of future therapies for PCD treatments. It is also clear that the management of patients within the complex of diseases that comprise PCD should be performed in centers with expertise in the imaging, medical, interventional and surgical approaches to diseases of the PCD.

Abnormal Trajectory of Intracortical Myelination in Schizophrenia Implicates White Matter in Disease Pathophysiology and the Therapeutic Mechanism of Action of Antipsychotics.

BACKGROUND: Postmortem and imaging studies provide converging evidence that the frontal lobe myelination trajectory is dysregulated in schizophrenia (SZ) and suggest that early in treatment, antipsychotic medications increase intracortical myelin (ICM). We used magnetic resonance imaging to examine whether the ICM trajectory in SZ is dysregulated and altered by antipsychotic treatment. METHODS: We examined 93 subjects with SZ (64 men and 29 women) taking second-generation oral antipsychotics with medication exposures of 0-333 months in conjunction with 80 healthy control subjects (52 men and 28 women). Frontal lobe ICM volume was estimated using a novel dual contrast magnetic resonance imaging method that combines two images that track different tissue components. RESULTS: When plotted against oral antipsychotic exposure duration, ICM of subjects with SZ was higher as a function of medication exposure during the first year of treatment but declined thereafter. In the age range examined, ICM of subjects with SZ was lower with increased age, while ICM of healthy control subjects was not. CONCLUSIONS: In adults with SZ, the relationship between length of exposure to oral second-generation antipsychotics and ICM was positive during the first year of treatment but was negative after this initial period, consistent with suboptimal later adherence after initial adherence. This ICM trajectory resembles clinically observed antipsychotic response trajectory with high rates of remission in the first year followed by progressively lower response rates. The results support postmortem evidence that SZ pathophysiology involves ICM deficits and suggest that correcting these deficits may be an important mechanism of action for antipsychotics.

Early Blood-Brain Barrier Disruption after Mechanical Thrombectomy in Acute Ischemic Stroke.

BACKGROUND AND PURPOSE: The impact of blood-brain barrier (BBB) disruption can be detected by intraparenchymal hyperdense lesion on the computed tomography (CT) scan after endovascular stroke therapy. The purpose of this study was to determine whether early BBB disruption predicts intracranial hemorrhage and poor outcome in patients with acute ischemic stroke treated with mechanical thrombectomy. METHODS: We analyzed patients with anterior circulation stroke treated with mechanical thrombectomy and identified BBB disruption on the noncontrast CT images immediately after endovascular treatment. Follow-up CT or magnetic resonance imaging scan was performed at 24 hours to assess intracranial hemorrhage. We dichotomized patients into those with moderate BBB disruption versus those with minor BBB disruption and no BBB disruption. We evaluated the association of moderate BBB disruption after mechanical thrombectomy with intracranial hemorrhage and clinical outcomes. RESULTS: Moderate BBB disruption after mechanical thrombectomy was found in 56 of 210 patients (26.7%). Moderate BBB disruption was independently associated with higher rates of hemorrhagic transformation (OR 25.33; 95% CI 9.93-64.65; P < .001), parenchymal hematoma (OR 20.57; 95% CI 5.64-74.99; P < .001), and poor outcome at discharge (OR 2.35; 95% CI 1.09-5.07; P = .03). The association of BBB disruption with intracranial hemorrhage remained in patients with successful reperfusion after mechanical thrombectomy. The location of BBB disruption was not associated with intracranial hemorrhage and poor outcome. CONCLUSIONS: Moderate BBB disruption is common after mechanical thrombectomy in a quarter of patients with acute ischemic stroke and increases the risk of intracranial hemorrhage and poor outcome.

Utilization of Emergent Neuroimaging for Thrombolysis-Eligible Stroke Patients.

BACKGROUND: Advances in diagnostic imaging of stroke include multimodal techniques such as noninvasive angiography and perfusion imaging. We aimed to characterize trends in neuroimaging utilization among acute stroke patients. Utilization of multimodal imaging for acute stroke in the community has remained largely uncharacterized despite its increased adoption at academic medical centers. METHODS: We quantified neuroimaging utilization in the emergency department (ED) for 1,700 hyperacute stroke patients presenting <2 hours after symptom onset who participated in the National Institutes of Health Field Administration of Stroke Therapy-Magnesium (FAST-MAG) study throughout Los Angeles and Orange Counties. FAST-MAG provided no recommendation as to imaging utilization. RESULTS: A total of 1,700 cases were imaged a median (interquartile range [IQR]) of 92 (74-120) minutes after last known well time and 28 (19-41) minutes after ED arrival. The initial scanner used in the ED was computed tomography (CT) in a preponderance of cases (N = 1,612, 95%), with magnetic resonance imaging (MRI) in 88 cases (5%). CT angiography (CTA) was obtained in 192 (11%) and perfusion CT (CTP) in 91 (5.4%) cases. MRI imaging was universally obtained using diffusion-weighted images, 60% with MR angiography and 33% included perfusion imaging. Rates of concomitant CTA or CTP use increased in the later years of the study from 4% in 2005-2006, 2% in 2007-2008, 8% in 2009-2010, and 26% in 2011-2012 (P for trend < .001). CONCLUSIONS: Among acute stroke patients, noncontrast CT was the most common initial imaging strategy in clinical practice in the 2005-2012 time period, though use of concomitant CTA grew to one-quarter of cases, suggestive of an upward trend.

Radiographic and Magnetic Resonance Imaging Identification of Thoracolumbar Spine Variants with Implications for the Positioning of the Conus Medullaris in Rhesus Macaques.

The anatomy of the vertebral column in mammals may differ between species and between subjects of the same species, especially with regards to the composition of the thoracolumbar spine. We investigated, using several noninvasive imaging techniques, the thoracolumbar spine of a total of 44 adult rhesus macaques of both genders. Radiographic examination of the vertebral column showed a predominant spine phenotype with 12 rib-bearing thoracic vertebrae and 7 lumbar vertebrae without ribs in 82% of subjects, whereas a subset of subjects demonstrated 13 rib-bearing thoracic vertebrae and 6 lumbar vertebrae without ribs. Computer tomography studies of the thoraco-lumbar spine in two cases with a pair of supernumerary ribs showed facet joints between the most caudal pair of ribs and the associated vertebra, supporting a thoracic phenotype. Magnetic resonance imaging (MRI) studies were used to determine the relationship between the lumbosacral spinal cord and the vertebral column. The length of the conus medullaris portion of the spinal cord was 1.5 ± 0.3 vertebral units, and its rostral and caudal positions in the spinal canal were at 2.0 ± 0.3 and 3.6 ± 0.4 vertebral units below the thoracolumbar junction, respectively (n = 44). The presence of a set of supernumerary ribs did not affect the length or craniocaudal position of the conus medullaris, and subjects with13 rib-bearing vertebrae may from a functional or spine surgical perspective be considered as exhibiting12 thoracic vertebrae and an L1 vertebra with ribs. Anat Rec, 300:300-308, 2017. © 2016 Wiley Periodicals, Inc.

Mechanical thrombectomy for acute ischemic stroke with cerebral microbleeds.

BACKGROUND: The influence of cerebral microbleeds (CMBs) on post-thrombolytic hemorrhagic transformation (HT) in patients with acute ischemic stroke remains controversial. OBJECTIVE: To investigate the association of CMBs with HT and clinical outcomes among patients with large-vessel occlusion strokes treated with mechanical thrombectomy. METHODS: We analyzed patients with acute stroke treated with Merci Retriever, Penumbra system or stent-retriever devices. CMBs were identified on pretreatment T2-weighted, gradient-recall echo MRI. We analyzed the association of the presence, burden, and distribution of CMBs with HT, procedural complications, in-hospital mortality, and clinical outcome. RESULTS: CMBs were detected in 37 (18.0%) of 206 patients. Seventy-three foci of microbleeds were identified. Fourteen patients (6.8%) had ≥2 CMBs, only 1 patient had ≥5 CMBs. Strictly lobar CMBs were found in 12 patients, strictly deep CMBs in 12 patients, strictly infratentorial CMBs in 2 patients, and mixed CMBs in 11 patients. There were no significant differences between patients with CMBs and those without CMBs in the rates of overall HT (37.8% vs 45.6%), parenchymal hematoma (16.2% vs 19.5%), procedure-related vessel perforation (5.4% vs 7.1%), in-hospital mortality (16.2% vs 18.3%), and modified Rankin Scale score 0-3 at discharge. CMBs were not independently associated with HT or in-hospital mortality in patients treated with either thrombectomy or intravenous thrombolysis followed by thrombectomy. CONCLUSIONS: Patients with CMBs are not at increased risk for HT and mortality following mechanical thrombectomy for acute stroke. Excluding such patients from mechanical thrombectomy is unwarranted. The risk of HT in patients with ≥5 CMBs requires further study.

New Cerebral Microbleeds After Mechanical Thrombectomy for Large-Vessel Occlusion Strokes.

The interval appearance of cerebral microbleeds (CMBs) after endovascular treatment has never been described. We investigated the frequency and predictors of new CMBs that developed shortly after mechanical thrombectomy for acute ischemic stroke, and its impact on clinical outcome.We retrospectively analyzed patients with large-vessel occlusion strokes treated with Merci Retriever, Penumbra System, or stent-retriever devices. Serial T2*-weighted gradient-recall echo (GRE) magnetic resonance imaging (MRI) before and 48 h after endovascular thrombectomy were assessed to identify new CMBs. We examined independent factors associated with new CMBs after mechanical thrombectomy. We analyzed the association of the presence, burden, and distribution of new CMBs with clinical outcome.A total of 187 consecutive patients with serial GRE were enrolled in this study. CMBs were evident in 36 (19.3%) patients before mechanical thrombectomy. New CMBs occurred in 41 (21.9%) patients after mechanical thrombectomy. Of the 68 new CMBs, 45 appeared in the lobar location, 18 in the deep location and 5 in the infratentorial location. The presence of baseline CMBs was associated with new CMBs after mechanical thrombectomy (OR 5.38; 95% CI 2.13-13.59; P < 0.001), no matter whether the patients were treated primarily with mechanical thrombectomy or with intravenous thrombolysis followed by mechanical thrombectomy. Patients with new CMBs did not have increased rates of hemorrhagic transformation, in-hospital mortality, and modified Rankin Scale score 4 to 6 at discharge.New CMBs are common after mechanical thrombectomy in one-fifth of patients with acute ischemic stroke. Baseline CMBs before mechanical thrombectomy predicts the development of new CMBs. New CMBs after mechanical thrombectomy do not influence clinical outcome.

Estimating peak skin and eye lens dose from neuroperfusion examinations: use of Monte Carlo based simulations and comparisons to CTDIvol, AAPM Report No. 111, and ImPACT dosimetry tool values.

PURPOSE: CT neuroperfusion examinations are capable of delivering high radiation dose to the skin or lens of the eyes of a patient and can possibly cause deterministic radiation injury. The purpose of this study is to: (a) estimate peak skin dose and eye lens dose from CT neuroperfusion examinations based on several voxelized adult patient models of different head size and (b) investigate how well those doses can be approximated by some commonly used CT dose metrics or tools, such as CTDIvol, American Association of Physicists in Medicine (AAPM) Report No. 111 style peak dose measurements, and the ImPACT organ dose calculator spreadsheet. METHODS: Monte Carlo simulation methods were used to estimate peak skin and eye lens dose on voxelized patient models, including GSF's Irene, Frank, Donna, and Golem, on four scanners from the major manufacturers at the widest collimation under all available tube potentials. Doses were reported on a per 100 mAs basis. CTDIvol measurements for a 16 cm CTDI phantom, AAPM Report No. 111 style peak dose measurements, and ImPACT calculations were performed for available scanners at all tube potentials. These were then compared with results from Monte Carlo simulations. RESULTS: The dose variations across the different voxelized patient models were small. Dependent on the tube potential and scanner and patient model, CTDIvol values overestimated peak skin dose by 26%-65%, and overestimated eye lens dose by 33%-106%, when compared to Monte Carlo simulations. AAPM Report No. 111 style measurements were much closer to peak skin estimates ranging from a 14% underestimate to a 33% overestimate, and with eye lens dose estimates ranging from a 9% underestimate to a 66% overestimate. The ImPACT spreadsheet overestimated eye lens dose by 2%-82% relative to voxelized model simulations. CONCLUSIONS: CTDIvol consistently overestimates dose to eye lens and skin. The ImPACT tool also overestimated dose to eye lenses. As such they are still useful as a conservative predictor of dose for CT neuroperfusion studies. AAPM Report No. 111 style measurements are a better predictor of both peak skin and eye lens dose than CTDIvol and ImPACT for the patient models used in this study. It should be remembered that both the AAPM Report No. 111 peak dose metric and CTDIvol dose metric are dose indices and were not intended to represent actual organ doses.

Quantitative analysis of hypoperfusion in acute stroke: arterial spin labeling versus dynamic susceptibility contrast.

BACKGROUND AND PURPOSE: This study compares the concordance between arterial spin labeling (ASL) and dynamic susceptibility contrast (DSC) for the identification of regional hypoperfusion and diffusion-perfusion mismatch tissue classification using a quantitative method. METHODS: The inclusion criteria for this retrospective study were as follows: patients with acute ischemic syndrome with symptom onset <24 hours and acquisition of both ASL and DSC MR perfusion. The volumes of infarction and hypoperfused lesions were calculated on ASL and DSC multi-parametric maps. Patients were classified into reperfused, matched, or mismatch groups using time to maximum >6 sec as the reference. In a subset of patients who were successfully recanalized, the identical analysis was performed and the infarction and hypoperfused lesion volumes were used for paired pre- and posttreatment comparisons. RESULTS: Forty-one patients met our inclusion criteria. Twenty patients underwent successful endovascular revascularization (TICI>2a), resulting in a total of 61 ASL-DSC data pairs for comparison. The hypoperfusion volume on ASL-cerebral blood flow best approximated the DSC-time to peak volume (r=0.83) in pretreatment group and time to maximum (r=0.46) after recanalization. Both ASL-cerebral blood flow and DSC-TTP overestimated the hypoperfusion volume compared with time to maximum volume in pretreatment (F=27.41, P<0.0001) and recanalized patients (F=8.78, P<0.0001). CONCLUSIONS: ASL-cerebral blood flow overestimates the DSC time to maximum hypoperfusion volume and mismatch classification in patients with acute ischemic syndrome. Continued overestimation of hypoperfused volume after recanalization suggests flow pattern and velocity changes in addition to arterial transit delay can affects the performance of ASL.

Natural history of asymptomatic unruptured cerebral aneurysms evaluated at CT angiography: growth and rupture incidence and correlation with epidemiologic risk factors.

PURPOSE: To characterize the relationship between aneurysm size and epidemiologic risk factors with growth and rupture by using computed tomographic (CT) angiography. MATERIALS AND METHODS: In this HIPAA-compliant, institutional review board approved study, patients with known asymptomatic unruptured intracerebral aneurysms were followed up longitudinally with CT angiographic examinations. Growth was defined as an increase in one or more dimensions above the measurement error, and at least 5% volume by using the ABC/2 method. Associations of epidemiologic factors with aneurysm growth and rupture were analyzed by using logistic regression analysis. Intra- and interobserver agreement coefficients for dimension, volume, and growth were evaluated by using the Pearson correlation coefficient and difference of means with 95% confidence intervals, the agreement statistic, and the McNemar χ(2). RESULTS: Patients (n = 165) with aneurysms (n = 258) had a mean follow-up time of 2.24 years from time of diagnosis. Forty-six of 258 (18%) aneurysms in 38 patients grew larger. Spontaneous rupture occurred in four of 228 (1.8%) intradural aneurysms of average size (6.2 mm). Risk of aneurysm rupture per patient-year was 2.4% (95% CI: 0.5%, 7.12%) with growth and 0.2% (95% CI: 0.006%, 1.22%) without growth (P = .034). There was a 12-fold higher risk of rupture for growing aneurysms (P < .002), with high intra- and interobserver correlation coefficients for size, volume, and growth. Tobacco smoking (3.806, one degree of freedom; P < .015,) and initial size (5.895, two degrees of freedom; P < .051) were independent covariates, predicting 78.4% of growing aneurysms. CONCLUSION: These results support imaging follow-up of all patients with aneurysms, including those whose aneurysms are smaller than the current 7-mm treatment threshold. Aneurysm growth, size, and smoking were associated with increased rupture risk.

The hyperdense vessel sign on CT predicts successful recanalization with the Merci device in acute ischemic stroke.

BACKGROUND: The success of mechanical clot retrieval for acute ischemic stroke may be influenced by the characteristics of the occlusive thrombus. The thrombus can be partly characterized by CT, as the hyperdense vessel sign (HVS) suggests erythrocyte-rich clot whereas fibrin-rich clot may be isodense. We hypothesized that the physical clot characteristics that determine CT density may also determine likelihood of retrieval with the Merci device. METHODS: We reviewed all acute stroke cases initially imaged with non-contrast CT before attempted Merci clot retrieval at a single center between 2004 and 2010. Each CT was blindly assessed for the presence or absence of the HVS, and post-retrieval angiograms were blindly assessed for reperfusion using the TICI scale. RESULTS: Of 67 patients analyzed (mean age 69; median NIHSS 19; 61% female), the HVS was seen in 42, and no HVS was present in 25. Successful recanalization was achieved in 79% of patients with the HVS (33/42), but in only 36% (9/25) of patients without HVS (p=0.001). The HVS was the only significant predictor of recanalization while accounting for age, treatment with IV-tPA, clot location, stroke etiology, time to treatment, and number of retrieval attempts. CONCLUSION: The HVS in acute ischemic stroke was strongly predictive of successful recanalization using the Merci device. The HVS may indicate thrombi that are less adhesive compared with isodense clots that are more resistant to mechanical retrieval. The absence of HVS on pre-treatment CT may thus suggest the need for a more aggressive or alternative therapeutic approach.

Acute stroke: a comparison of different CT perfusion algorithms and validation of ischaemic lesions by follow-up imaging.

OBJECTIVES: To compare ischaemic lesions predicted by different CT perfusion (CTP) post-processing techniques and validate CTP lesions compared with final lesion size in stroke patients. METHODS: Fifty patients underwent CT, CTP and CT angiography. Quantitative values and colour maps were calculated using least mean square deconvolution (LMSD), maximum slope (MS) and conventional singular value decomposition deconvolution (SVDD) algorithms. Quantitative results, core/penumbra lesion sizes and Alberta Stroke Programme Early CT Score (ASPECTS) were compared among the algorithms; lesion sizes and ASPECTS were compared with final lesions on follow-up MRI + MRA or CT + CTA as a reference standard, accounting for recanalisation status. RESULTS: Differences in quantitative values and lesion sizes were statistically significant, but therapeutic decisions based on ASPECTS and core/penumbra ratios would have been the same in all cases. CTP lesion sizes were highly predictive of final infarct size: Coefficients of determination (R (2)) for CTP versus follow-up lesion sizes in the recanalisation group were 0.87, 0.82 and 0.61 (P < 0.001) for LMSD, MS and SVDD, respectively, and 0.88, 0.87 and 0.76 (P < 0.001), respectively, in the non-recanalisation group. CONCLUSIONS: Lesions on CT perfusion are highly predictive of final infarct. Different CTP post-processing algorithms usually lead to the same clinical decision, but for assessing lesion size, LMSD and MS appear superior to SVDD. KEY POINTS: Following an acute stroke, CT perfusion imaging can help predict lesion evolution. Delay-insensitive deconvolution and maximum slope approach are superior to delay-sensitive deconvolution regarding accuracy. Different CT perfusion post-processing algorithms usually lead to the same clinical decision. CT perfusion offers new insights into the evolution of stroke.