Showing papers on "Perfusion scanning published in 2020"

Astrocytes monitor cerebral perfusion and control systemic circulation to maintain brain blood flow

Abstract: Astrocytes provide neurons with essential metabolic and structural support, modulate neuronal circuit activity and may also function as versatile surveyors of brain milieu, tuned to sense conditions of potential metabolic insufficiency. Here we show that astrocytes detect falling cerebral perfusion pressure and activate CNS autonomic sympathetic control circuits to increase systemic arterial blood pressure and heart rate with the purpose of maintaining brain blood flow and oxygen delivery. Studies conducted in experimental animals (laboratory rats) show that astrocytes respond to acute decreases in brain perfusion with elevations in intracellular [Ca2+]. Blockade of Ca2+-dependent signaling mechanisms in populations of astrocytes that reside alongside CNS sympathetic control circuits prevents compensatory increases in sympathetic nerve activity, heart rate and arterial blood pressure induced by reductions in cerebral perfusion. These data suggest that astrocytes function as intracranial baroreceptors and play an important role in homeostatic control of arterial blood pressure and brain blood flow.

Review of Perfusion Imaging in Acute Ischemic Stroke: From Time to Tissue.

Abstract: Perfusion imaging uses an intravascular tracer and serial imaging to quantify blood flow through the brain parenchyma. In acute ischemic stroke, perfusion imaging may increase diagnostic accuracy, aid treatment target identification, and provide prognostic information about functional outcome. Moreover, perfusion imaging can identify patients who benefit from reperfusion beyond the conventional time window or in whom time of symptom onset is unknown. Implementation of perfusion imaging in routine acute stroke care allows individualized treatment of stroke patients based on brain tissue status, rather than time-based treatment on the group level. In this review, we give an overview of computed tomography perfusion (CTP) and perfusion magnetic resonance imaging (MRP) in acute ischemic stroke and discuss technical properties, clinical use, and pitfalls.

Clinical quantitative cardiac imaging for the assessment of myocardial ischaemia

Abstract: Cardiac imaging has a pivotal role in the prevention, diagnosis and treatment of ischaemic heart disease. SPECT is most commonly used for clinical myocardial perfusion imaging, whereas PET is the clinical reference standard for the quantification of myocardial perfusion. MRI does not involve exposure to ionizing radiation, similar to echocardiography, which can be performed at the bedside. CT perfusion imaging is not frequently used but CT offers coronary angiography data, and invasive catheter-based methods can measure coronary flow and pressure. Technical improvements to the quantification of pathophysiological parameters of myocardial ischaemia can be achieved. Clinical consensus recommendations on the appropriateness of each technique were derived following a European quantitative cardiac imaging meeting and using a real-time Delphi process. SPECT using new detectors allows the quantification of myocardial blood flow and is now also suited to patients with a high BMI. PET is well suited to patients with multivessel disease to confirm or exclude balanced ischaemia. MRI allows the evaluation of patients with complex disease who would benefit from imaging of function and fibrosis in addition to perfusion. Echocardiography remains the preferred technique for assessing ischaemia in bedside situations, whereas CT has the greatest value for combined quantification of stenosis and characterization of atherosclerosis in relation to myocardial ischaemia. In patients with a high probability of needing invasive treatment, invasive coronary flow and pressure measurement is well suited to guide treatment decisions. In this Consensus Statement, we summarize the strengths and weaknesses as well as the future technological potential of each imaging modality.

Multimodal Predictive Modeling of Endovascular Treatment Outcome for Acute Ischemic Stroke Using Machine-Learning.

Abstract: Background and Purpose: This study assessed the predictive performance and relative importance of clinical, multimodal imaging, and angiographic characteristics for predicting the clinical outcome ...

Hypoperfusion intensity ratio correlates with angiographic collaterals in acute ischaemic stroke with M1 occlusion

Abstract: BACKGROUND AND PURPOSE Among patients with an acute ischaemic stroke secondary to large-vessel occlusion, the hypoperfusion intensity ratio (HIR) [time to maximum (TMax) > 10 volume/TMax > 6 volume] is a strong predictor of infarct growth. We studied the correlation between HIR and collaterals assessed with digital subtraction angiography (DSA) before thrombectomy. METHODS Between January 2014 and March 2018, consecutive patients with an acute ischaemic stroke and an M1 middle cerebral artery (MCA) occlusion who underwent perfusion imaging and endovascular treatment at our center were screened. Ischaemic core (mL), HIR and perfusion mismatch (TMax > 6 s minus core volume) were assessed through magnetic resonance imaging or computed tomography perfusion. Collaterals were assessed on pre-intervention DSA using the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR) scale. Baseline clinical and perfusion characteristics were compared between patients with good (ASITN/SIR score 3-4) and those with poor (ASITN/SIR score 0-2) DSA collaterals. Correlation between HIR and ASITN/SIR scores was evaluated using Pearson's correlation. Receiver operating characteristic analysis was performed to determine the optimal HIR threshold for the prediction of good DSA collaterals. RESULTS A total of 98 patients were included; 49% (48/98) had good DSA collaterals and these patients had significantly smaller hypoperfusion volumes (TMax > 6 s, 89 vs. 125 mL; P = 0.007) and perfusion mismatch volumes (72 vs. 89 mL; P = 0.016). HIR was significantly correlated with DSA collaterals (-0.327; 95% confidence interval, -0.494 to -0.138; P = 0.01). An HIR cut-off of <0.4 best predicted good DSA collaterals with an odds ratio of 4.3 (95% confidence interval, 1.8-10.1) (sensitivity, 0.792; specificity, 0.560; area under curve, 0.708). CONCLUSION The HIR is a robust indicator of angiographic collaterals and might be used as a surrogate of collateral assessment in patients undergoing magnetic resonance imaging. HIR <0.4 best predicted good DSA collaterals.

Dynamic contrast-enhanced MRI in oncology: how we do it

Abstract: Magnetic resonance imaging (MRI) is particularly attractive for clinical application in perfusion imaging thanks to the absence of ionizing radiation and limited volumes of contrast agent (CA) necessary. Dynamic contrast-enhanced MRI (DCE-MRI) involves sequentially acquiring T1-weighted images through an organ of interest during the passage of a bolus administration of CA. It is a particularly flexible approach to perfusion imaging as the signal intensity time course allows not only rapid qualitative assessment, but also quantitative measures of intrinsic perfusion and permeability parameters. We examine aspects of the T1-weighted image series acquisition, CA administration, post-processing that constitute a DCE-MRI study in clinical practice, before considering some heuristics that may aid in interpreting the resulting contrast enhancement time series. While qualitative DCE-MRI has a well-established role in the diagnostic assessment of a range of tumours, and a central role in MR mammography, clinical use of quantitative DCE-MRI remains limited outside of clinical trials. The recent publication of proposals for standardized acquisition and analysis protocols for DCE-MRI by the Quantitative Imaging Biomarker Alliance may be an opportunity to consolidate and advance clinical practice.

Cost-Effectiveness Analysis of Stress Cardiovascular Magnetic Resonance Imaging for Stable Chest Pain Syndromes

Abstract: Objectives The aim of this study was to compare, using results from the multicenter SPINS (Stress CMR Perfusion Imaging in the United States) study, the incremental cost-effectiveness of a stress cardiovascular magnetic resonance (CMR)–first strategy against 4 other clinical strategies for patients with stable symptoms suspicious for myocardial ischemia: 1) immediate x-ray coronary angiography (XCA) with selective fractional flow reserve for all patients; 2) single-photon emission computed tomography; 3) coronary computed tomographic angiography with selective computed tomographic fractional flow reserve; and 4) no imaging. Background Stress CMR perfusion imaging has established excellent diagnostic utility and prognostic value in coronary artery disease (CAD), but its cost-effectiveness in current clinical practice has not been well studied in the United States. Methods A decision analytic model was developed to project health care costs and lifetime quality-adjusted life years (QALYs) for symptomatic patients at presentation with a 32.4% prevalence of obstructive CAD. Rates of clinical events, costs, and quality-of-life values were estimated from SPINS and other published research. The analysis was conducted from a U.S. health care system perspective, with health and cost outcomes discounted annually at 3%. Results Using hard cardiovascular events (cardiovascular death or acute myocardial infarction) as the endpoint, total costs per person were lowest for the no-imaging strategy ($16,936) and highest for the immediate XCA strategy ($20,929). Lifetime QALYs were lowest for the no-imaging strategy (12.72050) and highest for the immediate XCA strategy (12.76535). The incremental cost-effectiveness ratio for the CMR-based strategy compared with the no-imaging strategy was $52,000/QALY, whereas the incremental cost-effectiveness ratio for the immediate XCA strategy was $12 million/QALY compared with CMR. Results were sensitive to variations in model inputs for prevalence of disease, hazard rate ratio for treatment of CAD, and annual discount rate. Conclusions Prior to invasive XCA, stress CMR can be a cost-effective gatekeeping tool in patients at risk for obstructive CAD in the United States. (Stress CMR Perfusion Imaging in the United States [SPINS] Study; NCT03192891

Optimizing Patient Selection for Endovascular Treatment in Acute Ischemic Stroke (SELECT): A Prospective, Multicenter Cohort Study of Imaging Selection.

Abstract: OBJECTIVE The primary imaging modalities used to select patients for endovascular thrombectomy (EVT) are noncontrast computed tomography (CT) and CT perfusion (CTP). However, their relative utility is uncertain. We prospectively assessed CT and CTP concordance/discordance and correlated the imaging profiles on both with EVT treatment decisions and clinical outcomes. METHODS A phase 2, multicenter, prospective cohort study of large-vessel occlusions presented up to 24 hours from last known well was conducted. Patients received a unified prespecified imaging evaluation (CT, CT angiography, and CTP with Rapid Processing of Perfusion and Diffusion software mismatch determination). The treatment decision, EVT versus medical management, was nonrandomized and at the treating physicians' discretion. An independent, blinded, neuroimaging core laboratory adjudicated favorable profiles based on predefined criteria (CT:Alberta Stroke Program Early CT Score ≥ 6, CTP:regional cerebral blood flow (<30%) < 70ml with mismatch ratio ≥ 1.2 and mismatch volume ≥ 10ml). RESULTS Of 4,722 patients screened from January 2016 to February 2018, 361 patients were included. Two hundred eighty-five (79%) received EVT, of whom 87.0% had favorable CTs, 91% favorable CTPs, 81% both favorable profiles, 16% discordant, and 3% both unfavorable. Favorable profiles on the 2 modalities correlated similarly with 90-day functional independence rates (favorable CT = 56% vs favorable CTP = 57%, adjusted odds ratio [aOR] = 1.91, 95% confidence interval [CI] = 0.40-9.01, p = 0.41). Having a favorable profile on both modalities significantly increased the odds of receiving thrombectomy as compared to discordant profiles (aOR = 3.97, 95% CI = 1.97-8.01, p < 0.001). Fifty-eight percent of the patients with favorable profiles on both modalities achieved functional independence as compared to 38% in discordant profiles and 0% when both were unfavorable (p < 0.001 for trend). In favorable CT/unfavorable CTP profiles, EVT was associated with high symptomatic intracranial hemorrhage (sICH) (24%) and mortality (53%) rates. INTERPRETATION Patients with favorable imaging profiles on both modalities had higher odds of receiving EVT and high functional independence rates. Patients with discordant profiles achieved reasonable functional independence rates, but those with an unfavorable CTP had higher adverse outcomes. Ann Neurol 2020;87:419-433.

Cardiovascular magnetic resonance: applications and practical considerations for the general cardiologist

Abstract: Cardiovascular magnetic resonance (CMR) is a rapidly evolving non-invasive imaging modality offering comprehensive, multiparametric assessment of cardiac structure and function in a variety of clinical situations. Cine imaging with CMR is the gold standard non-invasive imaging technique for the quantification of ventricular volumes and systolic function. It also affords superior visualisation of apical and right ventricular morphological abnormalities. In coronary artery disease, CMR stress perfusion imaging identifies functionally significant coronary artery disease with high sensitivity and specificity, and international guidelines recommend CMR perfusion imaging in patients with chest pain at intermediate-high risk of coronary disease. Late gadolinium enhancement (LGE) imaging is the most sensitive imaging technique for identifying infarction/viability. In non-ischaemic cardiomyopathy, LGE imaging plays vital diagnostic and prognostic roles in a number of cardiomyopathies (eg, hypertrophic and dilated cardiomyopathies, and amyloidosis). In vivo tissue characterisation with CMR enables the identification of oedema/inflammation in acute coronary syndromes/myocarditis and the diagnosis of chronic fibrotic conditions (eg, in hypertrophic and dilated cardiomyopathy, aortic stenosis and amyloidosis). CMR T2* imaging uniquely offers non-invasive assessment of iron overload states, facilitating diagnosis and management. A multiparametric CMR approach also enables differentiation of cardiac masses/tumours and is a useful adjunct to echocardiography in the assessment of valve disease. The emergence of automated, inline, quantitative methodologies will expand the scope of CMR and reduce its cost in forthcoming years.

Assessment of a Bayesian Vitrea CT Perfusion Analysis to Predict Final Infarct and Penumbra Volumes in Patients with Acute Ischemic Stroke: A Comparison with RAPID

Abstract: BACKGROUND AND PURPOSE: Brain CTP is used to estimate infarct and penumbra volumes to determine endovascular treatment eligibility for patients with acute ischemic stroke. We aimed to assess the accuracy of a Bayesian CTP algorithm in determining penumbra and final infarct volumes. MATERIALS AND METHODS: Data were retrospectively collected for 105 patients with acute ischemic stroke (55 patients with successful recanalization [TICI 2b/2c/3] and large-vessel occlusions and 50 patients without interventions). Final infarct volumes were calculated using DWI and FLAIR 24 hours following CTP imaging. RAPID and the Vitrea Bayesian CTP algorithm (with 3 different settings) predicted infarct and penumbra volumes for comparison with final infarct volumes to assess software performance. Vitrea settings used different combinations of perfusion maps (MTT, TTP, CBV, CBF, delay time) for infarct and penumbra quantification. Patients with and without interventions were included for assessment of predicted infarct and penumbra volumes, respectively. RESULTS: RAPID and Vitrea default setting had the most accurate final infarct volume prediction in patients with interventions ([Spearman correlation coefficient, mean infarct difference] default versus FLAIR: [0.77, 4.1 mL], default versus DWI: [0.72, 4.7 mL], RAPID versus FLAIR: [0.75, 7.5 mL], RAPID versus DWI: [0.75, 6.9 mL]). Default Vitrea and RAPID were the most and least accurate in determining final infarct volume for patients without an intervention, respectively (default versus FLAIR: [0.76, –0.4 mL], default versus DWI: [0.71, –2.6 mL], RAPID versus FLAIR: [0.68, −49.3 mL], RAPID versus DWI: [0.65, –51.5 mL]). CONCLUSIONS: Compared with RAPID, the Vitrea default setting was noninferior for patients with interventions and superior in penumbra estimation for patients without interventions as indicated by mean infarct differences and correlations with final infarct volumes.

Deep Learning Detection of Penumbral Tissue on Arterial Spin Labeling in Stroke

Abstract: Background and Purpose- Selection of patients with acute ischemic stroke for endovascular treatment generally relies on dynamic susceptibility contrast magnetic resonance imaging or computed tomography perfusion. Dynamic susceptibility contrast magnetic resonance imaging requires injection of contrast, whereas computed tomography perfusion requires high doses of ionizing radiation. The purpose of this work was to develop and evaluate a deep learning (DL)-based algorithm for assisting the selection of suitable patients with acute ischemic stroke for endovascular treatment based on 3-dimensional pseudo-continuous arterial spin labeling (pCASL). Methods- A total of 167 image sets of 3-dimensional pCASL data from 137 patients with acute ischemic stroke scanned on 1.5T and 3.0T Siemens MR systems were included for neural network training. The concurrently acquired dynamic susceptibility contrast magnetic resonance imaging was used to produce labels of hypoperfused brain regions, analyzed using commercial software. The DL and 6 machine learning (ML) algorithms were trained with 10-fold cross-validation. The eligibility for endovascular treatment was determined retrospectively based on the criteria of perfusion/diffusion mismatch in the DEFUSE 3 trial (Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke). The trained DL algorithm was further applied on twelve 3-dimensional pCASL data sets acquired on 1.5T and 3T General Electric MR systems, without fine-tuning of parameters. Results- The DL algorithm can predict the dynamic susceptibility contrast-defined hypoperfusion region in pCASL with a voxel-wise area under the curve of 0.958, while the 6 ML algorithms ranged from 0.897 to 0.933. For retrospective determination for subject-level endovascular treatment eligibility, the DL algorithm achieved an accuracy of 92%, with a sensitivity of 0.89 and specificity of 0.95. When applied to the GE pCASL data, the DL algorithm achieved a voxel-wise area under the curve of 0.94 and a subject-level accuracy of 92% for endovascular treatment eligibility. Conclusions- pCASL perfusion magnetic resonance imaging in conjunction with the DL algorithm provides a promising approach for assisting decision-making for endovascular treatment in patients with acute ischemic stroke.

Ischemia and no obstructive stenosis (INOCA) at CT angiography, CT myocardial perfusion, invasive coronary angiography, and SPECT: The CORE320 study

Abstract: Background CT allows evaluation of atherosclerosis, coronary stenosis, and myocardial ischemia. Data on the characterization of ischemia and no obstructive stenosis (INOCA) at CT remain limited. Purpose This was an observational study to describe the prevalence of INOCA defined at coronary CT angiography with CT perfusion imaging and associated clinical and atherosclerotic characteristics. The analysis was also performed for the combination of invasive coronary angiography (ICA) and SPECT as a secondary aim. Materials and Methods The prospective CORE320 study (ClinicalTrials.gov: NCT00934037) enrolled participants between November 2009 and July 2011 who were symptomatic and referred for clinically indicated ICA. Participants underwent CT angiography, rest-adenosine stress CT perfusion, and rest-stress SPECT prior to ICA. For this ancillary study, the following three phenotypes were considered, using either CT angiography/CT perfusion or ICA/SPECT data: (a) participants with obstructive (≥50%) stenosis, (b) participants with no obstructive stenosis but ischemia (ie, INOCA) on the basis of abnormal perfusion imaging results, and (c) participants with no obstructive stenosis and normal perfusion imaging results. Clinical characteristics and CT angiography atherosclerotic plaque measures were compared by using the Pearson χ2 or Wilcoxon rank-sum test. Results A total of 381 participants (mean age, 62 years [interquartile range, 56-68 years]; 129 [34%] women) were evaluated. A total of 31 (27%) of 115 participants without obstructive (≥50%) stenosis at CT angiography had abnormal CT perfusion findings. The corresponding value for ICA/SPECT was 45 (30%) of 151. The prevalence of INOCA was 31 (8%) of 381 (95% confidence interval [CI]: 5%, 11%) with CT angiography/CT perfusion and 45 (12%) of 381 (95% CI: 9%, 15%) with ICA/SPECT. Participants with CT-defined INOCA had greater total atheroma volume (118 vs 60 mm3, P = .008), more positive remodeling (13% vs 1%, P = .006), and greater low-attenuation atheroma volume (20 vs 10 mm3, P = .007) than participants with no obstructive stenosis and no ischemia. Comparisons for ICA/SPECT showed similar trends. Conclusion In CORE320, ischemia and no obstructive stenosis (INOCA) prevalence was 8% and 12% at CT angiography/CT perfusion and invasive coronary angiography/SPECT, respectively. Participants with INOCA had greater atherosclerotic burden and more adverse plaque features at CT compared with those with no obstructive stenosis and no ischemia. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Francois in this issue.

Does the Application of Tecar Therapy Affect Temperature and Perfusion of Skin and Muscle Microcirculation? A Pilot Feasibility Study on Healthy Subjects.

Abstract: Background: Tecar therapy (TT) is an endogenous thermotherapy used to generate warming up of superficial and deep tissues. TT capability to affect the blood flow is commonly considered to be the pr...

Impact of Initial Imaging Protocol on Likelihood of Endovascular Stroke Therapy.

Abstract: Background and Purpose: Noncontrast head CT and CT perfusion (CTP) are both used to screen for endovascular stroke therapy (EST), but the impact of imaging strategy on likelihood of EST is undeterm...

Endovascular versus medical therapy for large-vessel anterior occlusive stroke presenting with mild symptoms.

Abstract: BackgroundAcute ischemic stroke patients with a large-vessel occlusion but mild symptoms (NIHSS ≤ 6) pose a treatment dilemma between medical management and endovascular thrombectomy.AimsTo evaluat...

Imaging glioma biology: spatial comparison of amino acid PET, amide proton transfer, and perfusion-weighted MRI in newly diagnosed gliomas

Abstract: Imaging glioma biology holds great promise to unravel the complex nature of these tumors. Besides well-established imaging techniques such O-(2-[18F]fluoroethyl)-l-tyrosine (FET)-PET and dynamic susceptibility contrast (DSC) perfusion imaging, amide proton transfer–weighted (APTw) imaging has emerged as a promising novel MR technique. In this study, we aimed to better understand the relation between these imaging biomarkers and how well they capture cellularity and vascularity in newly diagnosed gliomas. Preoperative MRI and FET-PET data of 46 patients (31 glioblastoma and 15 lower-grade glioma) were segmented into contrast-enhancing and FLAIR-hyperintense areas. Using established cutoffs, we calculated hot-spot volumes (HSV) and their spatial overlap. We further investigated APTw and CBV values in FET-HSV. In a subset of 10 glioblastoma patients, we compared cellularity and vascularization in 34 stereotactically targeted biopsies with imaging. In glioblastomas, the largest HSV was found for APTw, followed by PET and CBV (p < 0.05). In lower-grade gliomas, APTw–HSV was clearly lower than in glioblastomas. The spatial overlap of HSV was highest between APTw and FET in both tumor entities and regions. APTw correlated significantly with cellularity, similar to FET, while the association with vascularity was more pronounced in CBV and FET. We found a relevant spatial overlap in glioblastomas between hotspots of APTw and FET both in contrast-enhancing and FLAIR-hyperintense tumor. As suggested by earlier studies, APTw was lower in lower-grade gliomas compared with glioblastomas. APTw meaningfully contributes to biological imaging of gliomas.

Improved brain perfusion after electrical cardioversion of atrial fibrillation.

Abstract: AIMS Atrial fibrillation (AF) has been associated with reduced brain volume, cognitive impairment, and reduced cerebral blood flow. The causes of reduced cerebral blood flow in AF are unknown, but no reduction was seen in individuals without the arrhythmia in a previous study. The aim of this study was to test the hypothesis that brain perfusion, measured with magnetic resonance imaging (MRI), improves after cardioversion of AF to sinus rhythm (SR). METHODS AND RESULTS All patients undergoing elective cardioversion at our institution were invited to participate. A total of 44 individuals were included. Magnetic resonance imaging studies were done before and after cardioversion with both brain perfusion and cerebral blood flow measurements. However, 17 did not complete the second MRI as they had a recurrence of AF during the observation period (recurrent AF group), leaving 17 in the SR group and 10 in the AF group to complete both measurements. Brain perfusion increased after cardioversion to SR by 4.9 mL/100 g/min in the whole brain (P < 0.001) and by 5.6 mL/100 g/min in grey matter (P < 0.001). Cerebral blood flow increased by 58.6 mL/min (P < 0.05). Both brain perfusion and cerebral blood flow remained unchanged when cardioversion was unsuccessful. CONCLUSION In this study of individuals undergoing elective cardioversion for AF, restoration, and maintenance of SR for at least 10 weeks after was associated with an improvement of brain perfusion and cerebral blood flow measured by both arterial spin labelling and phase contrast MRI. In those individuals where cardioversion was unsuccessful, there was no change in perfusion or blood flow.

Arterial Spin Labeling Applications in Pediatric and Adult Neurologic Disorders

Abstract: Arterial spin labeling (ASL) is a powerful noncontrast magnetic resonance imaging (MRI) technique that enables quantitative evaluation of brain perfusion. To optimize the clinical and research utilization of ASL, radiologists and physicists must understand the technical considerations and age-related variations in normal and disease states. We discuss advanced applications of ASL across the lifespan, with example cases from children and adults covering a wide variety of pathologies. Through literature review and illustrated clinical cases, we highlight the subtleties as well as pitfalls of ASL interpretation. First, we review basic physical principles, techniques, and artifacts. This is followed by a discussion of normal perfusion variants based on age and physiology. The three major categories of perfusion abnormalities-hypoperfusion, hyperperfusion, and mixed patterns-are covered with an emphasis on clinical interpretation and relationship to the disease process. Major etiologies of hypoperfusion include large artery, small artery, and venous disease; other vascular conditions; global hypoxic-ischemic injury; and neurodegeneration. Hyperperfusion is characteristic of vascular malformations and tumors. Mixed perfusion patterns can be seen with epilepsy, migraine, trauma, infection/inflammation, and toxic-metabolic encephalopathy. LEVEL OF EVIDENCE: 4 TECHNICAL EFFICACY STAGE: 3.

Contrast-enhanced ultrasound for quantification of tissue perfusion in humans.

Abstract: Contrast-enhanced ultrasound is an imaging technique that can be used to quantify microvascular blood volume and blood flow of vital organs in humans. It relies on the use of microbubble contrast agents and ultrasound-based imaging of microbubbles. Over the past decades, both ultrasound contrast agents and experimental techniques to image them have rapidly improved, as did experience among investigators and clinicians. However, these improvements have not yet resulted in uniform guidelines for CEUS when it comes to quantification of tissue perfusion in humans, preventing its uniform and widespread use in research settings. The objective of this review is to provide a methodological overview of CEUS and its development, the influences of hardware and software settings, type and dosage of ultrasound contrast agent, and method of analysis on CEUS-derived perfusion data. Furthermore, we will discuss organ-specific imaging challenges, advantages, and limitations of CEUS.

Brain tumor segmentation using 3D mask R-CNN for dynamic susceptibility contrast enhanced perfusion imaging

Abstract: The detection and segmentation of neoplasms are an important part of radiotherapy treatment planning, monitoring disease progression, and predicting patient outcome. In the brain, functional magnetic resonance imaging (MRI) like dynamic susceptibility contrast enhanced (DSC) or T1-weighted dynamic contrast enhanced (DCE) perfusion MRI are important tools for diagnosis. However, the manual contouring of these neoplasms are tedious, expensive, time-consuming, and contains inter-observer variability. In this work, we propose to use a 3D Mask R-CNN method to automatically detect and segment high and low grade brain tumors for DSC MRI perfusion images. Twenty-two high and low grade patients with 50-70 perfusion time-point volumes were used in this study. Experimental results show that our proposed method achieved an overall Dice similarity, precision, recall and center of mass distance were 89%±0.03%, 90%±0.02%, 87%±0.04% and 1.27±0.67 respectively.

Perfusion Imaging to Select Patients with Large Ischemic Core for Mechanical Thrombectomy.

Abstract: Background and purpose Patients with acute ischemic stroke, proximal vessel occlusion and a large ischemic core at presentation are commonly not considered for mechanical thrombectomy (MT). We tested the hypothesis that in patients with baseline large infarct cores, identification of remaining penumbral tissue using perfusion imaging would translate to better outcomes after MT. Methods This was a multicenter, retrospective, core lab adjudicated, cohort study of adult patients with proximal vessel occlusion, a large ischemic core volume (diffusion weighted imaging volume ≥70 mL), with pre-treatment magnetic resonance imaging perfusion, treated with MT (2015 to 2018) or medical care alone (controls; before 2015). Primary outcome measure was 3-month favorable outcome (defined as a modified Rankin Scale of 0-3). Core perfusion mismatch ratio (CPMR) was defined as the volume of critically hypo-perfused tissue (Tmax >6 seconds) divided by the core volume. Multivariable logistic regression models were used to determine factors that were independently associated with clinical outcomes. Outputs are displayed as adjusted odds ratio (aOR) and 95% confidence interval (CI). Results A total of 172 patients were included (MT n=130; Control n=42; mean age 69.0±15.4 years; 36% females). Mean core-volume and CPMR were 102.3±36.7 and 1.8±0.7 mL, respectively. As hypothesized, receiving MT was associated with increased probability of favorable outcome and functional independence, as CPMR increased, a difference becoming statistically significant above a mismatch-ratio of 1.72. Similarly, receiving MT was also associated with favorable outcome in the subgroup of 74 patients with CPMR >1.7 (aOR, 8.12; 95% CI, 1.24 to 53.11; P=0.028). Overall (prior to stratification by CPMR) 73 (42.4%) patients had a favorable outcome at 3 months, with no difference amongst groups. Conclusion s In patients currently deemed ineligible for MT due to large infarct ischemic cores at baseline, CPMR identifies a subgroup strongly benefiting from MT. Prospective studies are warranted.

The additive effects of obesity on myocardial microcirculation in diabetic individuals: a cardiac magnetic resonance first-pass perfusion study

Abstract: The microvascular effects of obesity should be considered in diabetic individuals for elucidating underlying mechanisms and developing targeted therapies. This study aims to determine the effect of obesity on myocardial microvascular function in type 2 diabetes mellitus (T2DM) patients using cardiac magnetic resonance (CMR) first-pass perfusion imaging and assessed significant risk factors for microvascular dysfunction. Between September 2016 and May 2018, 120 patients with T2DM (45.8% women [55 of 120]; mean age, 56.45 ± 11.97 years) and 79 controls (44.3% women [35 of 79]; mean age, 54.50 ± 7.79 years) with different body mass index (BMI) scales were prospectively enrolled and underwent CMR examination. CMR-derived perfusion parameters, including upslope, time to maximum signal intensity (TTM), maximum signal intensity (MaxSI), MaxSI (-baseline), and SI (baseline), and T2DM related risk factors were analyzed among groups/subgroups both in T2DM patients and controls. Univariable and multivariable linear and logistic regression analyses were performed to assess the potential additive effect of obesity on microvascular dysfunction in diabetic individuals. Compared with controls with comparable BMIs, patients with T2DM showed reduced upslope and MaxSI and increased TTM. For both T2DM and control subgroups, perfusion function gradually declined with increasing BMI, which was confirmed by all perfusion parameters, except for TTM (all P < 0.01). In multivariable linear regression analysis, BMI (β = − 0.516; 95% confidence interval [CI], − 0.632 to − 0.357; P < 0.001), female sex (β = 0.372; 95% CI, 0.215 to 0.475; P < 0.001), diabetes duration (β = − 0.169; 95% CI, − 0.319 to − 0.025; P = 0.022) and glycated haemoglobin (β = − 0.184; 95% CI, − 0.281 to − 0.039; P = 0.010) were significantly associated with global upslope in the T2DM group. Multivariable logistic regression analysis indicated that T2DM was an independent predictor of microvascular dysfunction in normal-weight (odds ratio[OR], 6.46; 95% CI, 2.08 to 20.10; P = 0.001), overweight (OR, 7.19; 95% CI, 1.67 to 31.07; P = 0.008) and obese participants (OR, 11.21; 95% CI, 2.38 to 52.75; P = 0.002). Myocardial microvascular function gradually declined with increasing BMI in both diabetes and non-diabetes status. T2DM was associated with an increased risk of microvascular dysfunction, and obesity exacerbated the adverse effect of T2DM.