Abstract: BACKGROUND: CT perfusion (CTP) and diffusion or perfusion MRI might assist patient selection for endovascular thrombectomy. We aimed to establish whether imaging assessments of irreversibly injured ischaemic core and potentially salvageable penumbra volumes were associated with functional outcome and whether they interacted with the treatment effect of endovascular thrombectomy on functional outcome. METHODS: In this systematic review and meta-analysis, the HERMES collaboration pooled patient-level data from all randomised controlled trials that compared endovascular thrombectomy (predominantly using stent retrievers) with standard medical therapy in patients with anterior circulation ischaemic stroke, published in PubMed from Jan 1, 2010, to May 31, 2017. The primary endpoint was functional outcome, assessed by the modified Rankin Scale (mRS) at 90 days after stroke. Ischaemic core was estimated, before treatment with either endovascular thrombectomy or standard medical therapy, by CTP as relative cerebral blood flow less than 30% of normal brain blood flow or by MRI as an apparent diffusion coefficient less than 620 μm2/s. Critically hypoperfused tissue was estimated as the volume of tissue with a CTP time to maximum longer than 6 s. Mismatch volume (ie, the estimated penumbral volume) was calculated as critically hypoperfused tissue volume minus ischaemic core volume. The association of ischaemic core and penumbral volumes with 90-day mRS score was analysed with multivariable logistic regression (functional independence, defined as mRS score 0-2) and ordinal logistic regression (functional improvement by at least one mRS category) in all patients and in a subset of those with more than 50% endovascular reperfusion, adjusted for baseline prognostic variables. The meta-analysis was prospectively designed by the HERMES executive committee, but not registered. FINDINGS: We identified seven studies with 1764 patients, all of which were included in the meta-analysis. CTP was available and assessable for 591 (34%) patients and diffusion MRI for 309 (18%) patients. Functional independence was worse in patients who had CTP versus those who had diffusion MRI, after adjustment for ischaemic core volume (odds ratio [OR] 0·47 [95% CI 0·30-0·72], p=0·0007), so the imaging modalities were not pooled. Increasing ischaemic core volume was associated with reduced likelihood of functional independence (CTP OR 0·77 [0·69-0·86] per 10 mL, pinteraction=0·29; diffusion MRI OR 0·87 [0·81-0·94] per 10 mL, pinteraction=0·94). Mismatch volume, examined only in the CTP group because of the small numbers of patients who had perfusion MRI, was not associated with either functional independence or functional improvement. In patients with CTP with more than 50% endovascular reperfusion (n=186), age, ischaemic core volume, and imaging-to-reperfusion time were independently associated with functional improvement. Risk of bias between studies was generally low. INTERPRETATION: Estimated ischaemic core volume was independently associated with functional independence and functional improvement but did not modify the treatment benefit of endovascular thrombectomy over standard medical therapy for improved functional outcome. Combining ischaemic core volume with age and expected imaging-to-reperfusion time will improve assessment of prognosis and might inform endovascular thrombectomy treatment decisions. FUNDING: Medtronic.

Abstract: Determining the brain perfusion is an important task for diagnosis of vascular diseases such as occlusions and intracerebral haemorrhage. Even after successful diagnosis, there is a high risk of restenosis or rebleeding such that patients need intense attention in the days after treatment. Within this work, we present a diagnostic tomographic imager that allows access to brain perfusion quantitatively in short intervals. The device is based on the magnetic particle imaging technology and is designed for human scale. It is highly sensitive and allows the detection of an iron concentration of 263 pmolFe ml−1, which is one of the lowest iron concentrations imaged by MPI so far. The imager is self-shielded and can be used in unshielded environments such as intensive care units. In combination with the low technical requirements this opens up a variety of medical applications and would allow monitoring of stroke on intensive care units. Magnetic particle imaging (MPI) has been applied to various pre-clinical settings, including detection of ischemic stroke in mice. Translation of MPI to a clinical setting has been obstacled by the lack of a device with sufficient bore size and, at the same time, reasonable technical requirements. Here the authors present a human-sized MPI device with low technical requirements designed for detection of brain ischemia.

Abstract: Recent positive trials have thrust acute cerebral perfusion imaging into the routine evaluation of acute ischemic stroke. Updated guidelines state that in patients with anterior circulation large vessel occlusions presenting beyond 6 hours from time last known well, advanced imaging selection including perfusion-based selection is necessary. Centers that receive patients with acute stroke must now have the capability to perform and interpret CT or magnetic resonance perfusion imaging or provide rapid transfer to centers with the capability of selecting patients for a highly impactful endovascular therapy, particularly in delayed time windows. Many stroke centers are quickly incorporating the use of automated perfusion processing software to interpret perfusion raw data. As CT perfusion (CTP) is being assimilated in real-world clinical practice, it is essential to understand the basics of perfusion acquisition, quantification, and interpretation. It is equally important to recognize the common technical and clinical diagnostic challenges of automated CTP including ischemic core and penumbral misclassifications that could result in underestimation or overestimation of the core and penumbra volumes. This review highlights the pitfalls of automated CTP along with practical pearls to address the common challenges. This is particularly tailored to aid the acute stroke clinician who must interpret automated perfusion studies in an emergency setting to make time-dependent treatment decisions for patients with acute ischemic stroke.

Abstract: Importance The efficacy and safety of endovascular thrombectomy (EVT) in patients with large ischemic cores remains unknown, to our knowledge. Objective To compare outcomes in patients with large ischemic cores treated with EVT and medical management vs medical management alone. Design, Setting, and Participants This prespecified analysis of the Optimizing Patient’s Selection for Endovascular Treatment in Acute Ischemic Stroke (SELECT) trial, a prospective cohort study of imaging selection that was conducted in 9 US comprehensive stroke centers, enrolled patients between January 2016 and February 2018, and followed them up for 90 days. Patients with moderate to severe stroke and anterior circulation large-vessel occlusion presenting up to 24 hours from the time they were last known to be well were eligible for the cohort. Of these, patients with large ischemic cores on computed tomography (CT) (Alberta Stroke Program Early CT Score Exposures Endovascular thrombectomy with medical management (MM) or MM only. Main Outcomes and Measures Functional outcomes at 90 days per modified Rankin scale; safety outcomes (mortality, symptomatic intracerebral hemorrhage, and neurological worsening). Results A total of 105 patients with large ischemic cores on either CT or CT perfusion images were included: 71 with Alberta Stroke Program Early CT Scores of 5 or less (EVT, 37; MM, 34), 74 with cores of 50 cm3or greater on CT perfusion images (EVT, 39; MM, 35), and 40 who had large cores on both CT and CT perfusion images (EVT, 14; MM, 26). The median (interquartile range) age was 66 (60-75) years; 45 patients (43%) were female. Nineteen of 62 patients (31%) who were treated with EVT achieved functional independence (modified Rankin Scale scores, 0-2) vs 6 of 43 patients (14%) treated with MM only (odds ratio [OR], 3.27 [95% CI, 1.11-9.62];P = .03). Also, EVT was associated with better functional outcomes (common OR, 2.12 [95% CI, 1.05-4.31];P = .04), less infarct growth (44 vs 98 mL;P = .006), and smaller final infarct volume (97 vs 190 mL;P = .001) than MM. In the odds of functional independence, there was a 42% reduction per 10-cm3increase in core volume (adjusted OR, 0.58 [95% CI, 0.39-0.87];P = .007) and a 40% reduction per hour of treatment delay (adjusted OR, 0.60 [95% CI, 0.36-0.99];P = .045). Of 10 patients who had EVT with core volumes greater than 100 cm3, none had a favorable outcome. Conclusions and Relevance Although the odds of good outcomes for patients with large cores who receive EVT markedly decline with increasing core size and time to treatment, these data suggest potential benefits. Randomized clinical trials are needed.

Abstract: Background: Coronary microvascular dysfunction (MVD) is defined by impaired flow augmentation in response to a pharmacological vasodilator in the presence of nonobstructive coronary artery disease....

Abstract: Treatment evaluation of patients with glioblastomas is important to aid in clinical decisions. Conventional MRI with contrast is currently the standard method, but unable to differentiate tumor progression from treatment-related effects. Pseudoprogression appears as new enhancement, and thus mimics tumor progression on conventional MRI. Contrarily, a decrease in enhancement or edema on conventional MRI during antiangiogenic treatment can be due to pseudoresponse and is not necessarily reflective of a favorable outcome. Neovascularization is a hallmark of tumor progression but not for posttherapeutic effects. Perfusion-weighted MRI provides a plethora of additional parameters that can help to identify this neovascularization. This review shows that perfusion MRI aids to identify tumor progression, pseudoprogression, and pseudoresponse. The review provides an overview of the most applicable perfusion MRI methods and their limitations. Finally, future developments and remaining challenges of perfusion MRI in treatment evaluation in neuro-oncology are discussed. Level of Evidence: 3 Technical Efficacy: Stage 4 J. Magn. Reson. Imaging 2019;49:11-22.

Abstract: Background: Given the increasing worldwide prevalence of chronic kidney disease (CKD), it is critical to decrease the associated risk of debilitating vascular complications, including stroke, congestive heart failure, myocardial infarction, and peripheral vascular disease. Treatment options for reducing the risk of all subtypes of stroke in patients with CKD remain limited. For patients with end-stage kidney disease (ESKD), novel applications of noninvasive imaging may help personalize the type of dialysis and dialysis prescription for patients at high-risk. Summary: This manuscript reviews the heightened risk of stroke in patients with nephropathy, including ischemic and hemorrhagic subtypes. Mechanisms associated with increased risk include alterations in cardiac output, platelet function, regional cerebral perfusion, accelerated systemic atherosclerosis, altered blood brain barrier, and disordered neurovascular coupling. There is great potential for noninvasive monitoring of the cerebral vasculature using transcranial Doppler (TCD) to reduce stroke risk, particularly in patients with ESKD. Key Messages: Compared to the general population, patients with CKD are at heightened risk for all subtypes of stroke. This is due to a multitude of mechanisms linking nephropathy with altered cerebral perfusion, cerebral neurovascular coupling, and blood vessel integrity. Intracranial imaging is not currently standard of care practice in patients with CKD or ESKD. TCD may provide clinicians real-time and noninvasive measurement of brain perfusion. This could be useful for assessing risk of stroke in patients’ initiating dialysis, individualizing dialysis prescriptions, and potentially reducing rates of cerebrovascular disease and stroke in high-risk patients.

Abstract: Cerebral perfusion declines across the lifespan and is altered in the early stages of several age-related neuropathologies. Little is known, however, about the longitudinal evolution of perfusion in healthy older adults, particularly when perfusion is quantified using magnetic resonance imaging with arterial spin labeling (ASL). The objective was to characterize longitudinal perfusion in typically aging adults and elucidate associations with cognition and brain structure. Adults who were functionally intact at baseline (n = 161, ages 47-89) underwent ASL imaging to quantify whole-brain gray matter perfusion; a subset (n = 136) had repeated imaging (average follow-up: 2.3 years). Neuropsychological testing at each visit was summarized into executive function, memory, and processing speed composites. Global gray matter volume, white matter microstructure (mean diffusivity), and white matter hyperintensities were also quantified. We assessed baseline associations among perfusion, cognition, and brain structure using linear regression, and longitudinal relationships using linear mixed effects models. Greater baseline perfusion, particularly in the left dorsolateral prefrontal cortex and right thalamus, was associated with better executive functions. Greater whole-brain perfusion loss was associated with worsening brain structure and declining processing speed. This study helps validate noninvasive MRI-based perfusion imaging and underscores the importance of cerebral blood flow in cognitive aging.

Abstract: Perfusing fixatives through the cerebrovascular system is the gold standard approach in animals to prepare brain tissue for spatial biomolecular profiling, circuit tracing, and ultrastructural studies such as connectomics. Translating these discoveries to humans requires examination of postmortem autopsy brain tissue. Yet banked brain tissue is routinely prepared using immersion fixation, which is a significant barrier to optimal preservation of tissue architecture. The challenges involved in adopting perfusion fixation in brain banks and the extent to which it improves histology quality are not well defined. We searched four databases to identify studies that have performed perfusion fixation in human brain tissue and screened the references of the eligible studies to identify further studies. From the included studies, we extracted data about the methods that they used, as well as any data comparing perfusion fixation to immersion fixation. The protocol was preregistered at the Open Science Framework: https://osf.io/cv3ys/ . We screened 4489 abstracts, 214 full-text publications, and identified 35 studies that met our inclusion criteria, which collectively reported on the perfusion fixation of 558 human brains. We identified a wide variety of approaches to perfusion fixation, including perfusion fixation of the brain in situ and ex situ, perfusion fixation through different sets of blood vessels, and perfusion fixation with different washout solutions, fixatives, perfusion pressures, and postfixation tissue processing methods. Through a qualitative synthesis of data comparing the outcomes of perfusion and immersion fixation, we found moderate confidence evidence showing that perfusion fixation results in equal or greater subjective histology quality compared to immersion fixation of relatively large volumes of brain tissue, in an equal or shorter amount of time. This manuscript serves as a resource for investigators interested in building upon the methods and results of previous research in designing their own perfusion fixation studies in human brains or other large animal brains. We also suggest several future research directions, such as comparing the in situ and ex situ approaches to perfusion fixation, studying the efficacy of different washout solutions, and elucidating the types of brain donors in which perfusion fixation is likely to result in higher fixation quality than immersion fixation.

Abstract: Tumor microenvironment influences the efficacy of anti-cancer therapies. The dysfunctional tumor vasculature limits the efficiency of oxygenation and drug delivery to reduce treatment outcome. A concept of tumor vascular normalization (VN), which inhibits angiogenesis to improve vessel maturity, blood perfusion, and oxygenation, has been demonstrated under the anti-angiogenic therapy. The efficiency of drug delivery and penetration is increased by enhancing perfusion and reducing interstitial fluid pressure during the time window of VN. However, anti-angiogenic agents only induce transient VN and then prune vessels to aggravate tumor hypoxia. To repair tumor vessels without altering vessel density, we proposed to induce tumor VN by local oxygen release via oxygen microbubbles with ultrasound. With tumor perfusion enhancement under ultrasound contrast imaging tracing, the time window of VN was defined as 2-8 days after a single oxygen microbubble treatment. The enhanced tumor oxygenation after oxygen microbubble treatment inhibited hypoxia inducible factor-1 alpha (HIF-1α)/vascular endothelial growth factor (VEGF) pathway to improve the morphology and function of tumor vasculature. The pericyte coverage and Hoechst penetration of tumor vessels increased without any changes to the vessel density. Finally, the intratumoral accumulation of anti-cancer drug doxorubicin could be increased 3-4 folds during tumor VN. These findings demonstrate that regulating tumor oxygenation by oxygen microbubbles could normalize dysfunctional vessels to enhance vascular maturity, blood perfusion, and drug penetration. Furthermore, ultrasound perfusion imaging provides a simple and non-invasive way to detect the VN time window, which increases the feasibility of VN in clinical cancer applications.

Abstract: Background and Purpose- Efficacy of endovascular thrombectomy has been demonstrated up to 24 hours after stroke onset in patients selected with perfusion imaging. We hypothesized that a persistent favorable perfusion profile exists in some patients beyond 24 hours from the onset and can be predicted by a lower baseline hypoperfusion intensity ratio, which indicates favorable collaterals. Methods- We identified control arm patients from the DEFUSE 3 trial (The Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke) with a diffusion weighted imaging and perfusion magnetic resonance imaging performed 24 hours following randomization and compared imaging and clinical variables between patients with persistent mismatch versus patients who no longer had a mismatch 24 hours after randomization. Results- Eighteen percent of the control arm patients had a persistent favorable profile >38 hours after last known well time. These patients had similar baseline diffusion weighted imaging and Tmax >6 seconds volumes as patients whose initially favorable perfusion profile became unfavorable (diffusion weighted imaging lesion 7 versus 17 mL; P=0.17, Tmax >6 seconds 98 versus 100 mL; P=0.48) yet experienced less infarct growth (15 versus 59 mL; P<0.001) and had 3-fold smaller infarct volumes (15 versus 59 mL; P<0.001) 24 hours after randomization. Patients with a persistent favorable perfusion profile had a significantly lower hypoperfusion intensity ratio on baseline imaging (0.2 versus 0.4; P<0.01). Favorable clinical outcome at 90 days occurred in only 10% of the persistent mismatch patients. Conclusions- About 20% of patients with a middle cerebral artery or internal carotid artery occlusion who present in an extended time window and are not treated with thrombectomy have a persistent mismatch for at least an additional 24 hours. These patients have a favorable hypoperfusion intensity ratio at presentation, may experience delayed infarct expansion, and have poor clinical outcomes. Clinical trials are needed to determine if patients with a favorable perfusion profile benefit from reperfusion beyond 24 hours. Clinical Trial Registration- URL: https://www.clinicaltrials.gov . Unique identifier: NCT02586415.

Abstract: Background and Purpose: Automated imaging software is integral to decision-making in acute ischemic stroke (AIS) during extended time windows. RAPID software is the most widely used and has been validated in landmark endovascular trials. Olea software is another commercially available and FDA-approved software, but has not been studied in AIS trials. We aimed to compare the diagnostic utility and accuracy of RAPID and Olea in everyday clinical practice outside of a clinical trial. Methods: We analyzed prospectively-collected data from a consecutive cohort of 141 patients with suspected AIS who underwent computed tomography perfusion upon presentation followed by diffusion-weighted magnetic resonance imaging (DWI-MRI) within 24-48 hours. Core infarct was defined as the region with a relative cerebral blood flow (rCBF) less than 30% on RAPID and rCBF less than 40% on Olea (default settings). We also evaluated rCBF less than 30% on Olea to match RAPID's default setting. Infarct volume on DWI-MRI was measured using a semiautomated segmentation method. Results: Twenty-one patients were excluded; 14 due to poor bolus tracking and/or motion artifact, and 7 due to software failure. The software failure rate was 4.7% [6/127] with RAPID versus .78% [1/127] with Olea (P = .12). For the remaining 120 patients, the sensitivity and specificity for detecting an acute infarct were 40.5% and 97.6% for RAPID; 50.6% and 85.4% for Olea; and for detecting large infarcts (≥70 mL on DWI-MRI) 73.7% and 81.2% for RAPID; 73.7% and 68.3% for Olea. Core infarct volume on RAPID was more closely correlated with DWI-MRI infarct volume (rho = .64) than Olea (rho = .42). Conclusions: Our head-to-head comparison of these 2 commonly-used softwares in the clinical setting elucidates the pros and cons of their use to guide decision-making for AIS management in the acute setting.

Abstract: CT perfusion can be useful in the work-up of patients with acute stroke. The value of the additional diagnostic information gained should, however, be weighed against treatment delays and the added contrast and radiation exposure that are incurred by obtaining a CTP study. AHA stroke guidelines recommend against the routine use of CTP in the early time-window (up to 6 h) because most early-window trials did not use CTP for patient selection. Treatment decisions regarding tPA can typically be based on non-contrast CT alone and treatment decisions regarding early-window endovascular therapy can be based on NCCT and CTA. In the early time-window, it is therefore reasonable to only obtain a CTP when the NCCT CTA provide insufficient diagnostic information. In contrast, AHA guidelines do recommend CTP or MR imaging for triage beyond 6h based on the results of two recent trials that showed benefit of endovascular therapy in the 6–24-h-time window in patients selected with CT perfusion or MRI. Due to cost and workflow considerations, most hospitals will opt to primarily use CT perfusion (CTP) and not MRI for triage. Because CT perfusion protocols are not standardized, these hospitals are now faced with the question of how to acquire, process, and interpret CT perfusion imaging. These aspects are not covered in the guidelines. This brief review aims to provide practical guidance on how to implement CT perfusion for acute stroke.

Abstract: Background: The goal of this study was to assess the prevalence of myocardial microvascular dysfunction in rheumatoid arthritis (RA) patients without clinical cardiovascular disease and its associa...

Abstract: Objective To explore the association of poststroke baseline blood pressure with cerebral collateral flow and functional outcome in acute ischemic patients with large vessel occlusion/stenosis. Methods Patients identified with large vessel occlusion/stenosis with baseline multimodal computed tomography, follow-up imaging, and complete clinical profiles were included. A 90-day modified Rankin Scale of 0-1 was defined as an excellent functional outcome. Cerebral collateral flow was quantified by the volume ratio of tissue within the delay time >3 seconds perfusion lesion with severely delayed contrast transit (delay time >3 seconds/delay time >6 seconds). Results There were 306 patients included in this study. With every increase of 10 mmHg in baseline systolic blood pressure, the odds of achieving an excellent functional outcome decreased by 12% in multivariate analysis (odds ratio = 0.88, p = 0.048). Conversely, increased baseline blood pressure was associated with better collateral flow. In subgroup analysis of patients with major reperfusion, higher blood pressure was associated with decreased infarct growth and a better clinical outcome, and vice versa in patients without reperfusion. Interpretation Higher baseline blood pressure in acute ischemic stroke patients with large vessel occlusion/stenosis was associated with better collateral flow. However, for patients without reperfusion, higher baseline blood pressure was associated with increased infarct growth, leading to an unfavorable clinical outcome. The relationship between blood pressure and outcomes is highly dependent on reperfusion, and active blood pressure-lowering treatment may be inappropriate in acute ischemic stroke patients prior to reperfusion treatment. ANN NEUROL 2019;85:331-339.

Abstract: Indocyanine green fluorescence angiography (ICG-FA) is an established technique for assessment of intestinal perfusion during gastrointestinal surgery, whereas quantitative ICG-FA (q-ICG) and laser speckle contrast imaging (LSCI) are relatively unproven. The study aimed to investigate whether the techniques could be applied interchangeably for perfusion assessment. Nineteen pigs underwent laparotomy, two minor resections of the small bowel, and anastomoses. Additionally, seven pigs had parts of their stomach and small intestine de-vascularized. Data was also collected from an in vivo model (inferior caval vein measurements in two additional pigs) and an ex vivo flow model, allowing for standardization of experimental flow, distance, and angulation. Q-ICG and LSCI were performed, so that regions of interest were matched between the two modalities in the analyses, ensuring coverage of the same tissue. The overall correlation of q-ICG and LSCI evaluated in the porcine model was modest (rho = 0.45, p < 0.001), but high in tissue with low perfusion (rho = 0.74, p < 0.001). Flux values obtained by LSCI from the ex vivo flow model revealed a decreasing flux with linearly increasing distance as well as angulation to the model. The Q-ICG perfusion values obtained varied slightly with increasing distance as well as angulation to the model. Q-ICG and LSCI cannot be used interchangeably but may supplement each other. LSCI is profoundly affected by angulation and distance. In comparison, q-ICG is minimally affected by changing experimental conditions and is more readily applicable in minimally invasive surgery.

Abstract: Objective We assessed patient clinical outcomes based on occlusion location, focusing on distal occlusions to understand if occlusion location was an independent predictor of outcome, and tested the relationship between occlusion location and baseline ischemic core, a known predictor of modified Rankin Scale (mRS) score at 90 days. Methods We analyzed a prospectively collected cohort of thrombolysis-eligible ischemic stroke patients from the International Stroke Perfusion Imaging Registry who underwent multimodal CT pretreatment. For the primary analysis, logistic regression was used to predict the effect of occlusion location and ischemic core on the likelihood of excellent (mRS 0–1) and favorable (mRS 0–2) 90-day outcomes. Results This study included 945 patients. The rates of excellent and favorable outcome in patients with distal occlusion (M2, M3 segment of middle cerebral artery, anterior cerebral artery, and posterior cerebral artery) were higher than M1 occlusions (mRS 0%–1%, 55% vs 37%; mRS 0%–2%, 73% vs 50%, p Conclusions Ischemic stroke patients with a distal occlusion have higher rate of excellent and favorable outcome than patients with an M1 occlusion. The baseline ischemic core was shown to be a more powerful predictor of functional outcome than the occlusion location, but the relationship between ischemic core and outcome does not different by occlusion locations.

Abstract: BACKGROUND AND PURPOSE: In-hospital time delays lead to a relevant deterioration of neurologic outcomes in patients with stroke with large-vessel occlusions. At the moment, CT perfusion is relevant in the triage of late-window patients with stroke. We conducted this study to determine whether one-stop management with perfusion is feasible and leads to a reduction of in-hospital times. MATERIALS AND METHODS: In this observational study, we report the first 15 consecutive transfer patients with stroke with externally confirmed large-vessel occlusions who underwent flat panel detector CT perfusion and thrombectomy in the same room. Preinterventional imaging consisted of noncontrast flat panel detector CT and flat panel detector CT perfusion, acquired with a biplane angiography system. The flat panel detector CT perfusion was used to reconstruct a flat panel detector CT angiography to confirm the large-vessel occlusions. After confirmation of the large-vessel occlusion, the patient underwent mechanical thrombectomy. We recorded time metrics and safety parameters prospectively and compared them with those of transfer patients whom we treated before the introduction of one-stop management with perfusion. RESULTS: Fifteen transfer patients underwent flat panel detector CT perfusion and were treated with mechanical thrombectomy from June 2017 to January 2019. The median time from symptom onset to admission was 241 minutes. Median door-to-groin time was 24 minutes. Compared with 23 transfer patients imaged with multidetector CT, it was reduced significantly (24 minutes; 95% CI, 19–37 minutes, versus 53 minutes; 95% CI, 44–66 minutes; P CONCLUSIONS: In this small series, one-stop management with perfusion led to a significant reduction of in-hospital times compared with our previous workflow.

Abstract: Background The accuracy of absolute myocardial blood flow (MBF) from dynamic contrast-enhanced cardiac computed tomography acquisitions has not been fully characterized. We evaluate computed tomography (CT) compared with rubidium-82 positron emission tomography (PET) MBF estimates in a high-risk population. Methods In a prospective trial, patients receiving clinically indicated rubidium-82 PET exams were recruited to receive a dynamic contrast-enhanced cardiac computed tomography exam. The CT protocol included a rest and stress dynamic portion each acquiring 12 to 18 cardiac-gated frames. The global MBF was estimated from the PET and CT exam. Results Thirty-four patients referred for cardiac rest-stress PET were recruited. Of the 68 dynamic contrast-enhanced cardiac computed tomography scans, 5 were excluded because of injection errors or mismatched hemodynamics. The CT-derived global MBF was highly correlated with the PET MBF (r=0.92; P<0.001) with a mean difference of 0.7±26.4%. The CT MBF estimates were within 20% of PET estimates ( P<0.02) with a mean of (1) MBF for resting flow of PET versus CT of 0.9±0.3 versus 1.0±0.2 mL/min per gram and (2) MBF for stress flow of 2.1±0.7 versus 2.0±0.8 mL/min per gram. Myocardial flow reserve was -14±28% underestimated with CT (PET versus CT myocardial flow reserve, 2.5±0.6 versus 2.2±0.6). The proposed rest+stress+computed tomography angiography protocol had a dose length product of 598±76 mGy×cm resulting in an approximate effective dose of 8.4±1.1 mSv. Conclusions In a high-risk clinical population, a clinically practical dynamic contrast-enhanced cardiac computed tomography provided unbiased MBF estimates within 20% of rubidium-82 PET. Although unbiased, the CT estimates contain substantial variance with an standard error of the estimate of 0.44 mL/min per gram. Myocardial flow reserve estimation was not as accurate as individual MBF estimates.

Abstract: Heart failure with preserved ejection fraction (HFpEF) is frequently accompanied by co-morbidities and a systemic proinflammatory state, resulting in coronary microvascular dysfunction (CMD), as well as myocardial fibrosis. The purpose of this study is to examine the relation between myocardial perfusion reserve (MPR) and diffuse myocardial fibrosis in patients with HFpEF using cardiovascular magnetic resonance. A single center study was performed in 19 patients with clinical HFpEF and 15 healthy control subjects who underwent quantitative first-pass perfusion imaging to calculate global MPR. T1 mapping was used to assess fibrosis and to calculate extracellular volume. Spiral cine displacement encoded stimulated echo was used to calculate myocardial strain. Comprehensive 2D echocardiograms with speckle tracking, cardiopulmonary exercise testing, and brain natriuretic peptide levels were also obtained. In patients with HFpEF, mean left ventricular EF was 61% ± 9% and left ventricular mass index 45 ± 12 g/m2. Compared with controls, HFpEF patients had reduced global MPR (2.29 ± 0.64 vs 3.38 ± 0.76, p = 0.002) and VO2 max (16.5 ± 6.8 vs 30.9 ± 7.7 ml/kg min, p

Abstract: Functional magnetic resonance imaging (MRI) of tumors of the head and neck usually encompasses diffusion-weighted imaging (DWI) and intravenous (IV) contrast T1 dynamic perfusion imaging (DCE-MRI or PWI). Both techniques can characterize different tissues by probing into their microstructure, providing a novel approach in oncological imaging. In this pictorial review, we will cover the important technical aspects of DWI and PWI, the pathophysiological background and the current applications and potential of these functional MRI techniques in the imaging of head and neck cancer.

Abstract: A large variety of severe medical conditions involve alterations in microvascular circulation. Hence, measurements or simulation of circulation and perfusion has considerable clinical value and can be used for diagnostics, evaluation of treatment efficacy, and for surgical planning. However, the accuracy of traditional tracer kinetic one-compartment models is limited due to scale dependency. As a remedy, we propose a scale invariant mathematical framework for simulating whole brain perfusion. The suggested framework is based on a segmentation of anatomical geometry down to imaging voxel resolution. Large vessels in the arterial and venous network are identified from time-of-flight (ToF) and quantitative susceptibility mapping (QSM). Macro-scale flow in the large-vessel-network is accurately modelled using the Hagen-Poiseuille equation, whereas capillary flow is treated as two-compartment porous media flow. Macro-scale flow is coupled with micro-scale flow by a spatially distributing support function in the terminal endings. Perfusion is defined as the transition of fluid from the arterial to the venous compartment. We demonstrate a whole brain simulation of tracer propagation on a realistic geometric model of the human brain, where the model comprises distinct areas of grey and white matter, as well as large vessels in the arterial and venous vascular network. Our proposed framework is an accurate and viable alternative to traditional compartment models, with high relevance for simulation of brain perfusion and also for restoration of field parameters in clinical brain perfusion applications.

Abstract: The heart failure epidemic continues to rise with coronary artery disease as one of its main causes. Novel concepts for risk stratification to guide the referring cardiologist towards revascularization procedures are of significant value. Myocardial perfusion imaging using single-photon emission computed tomography (SPECT) agents has demonstrated high accuracy for the detection of clinically relevant stenoses. With positron emission tomography (PET) becoming more widely available, mainly due to its diagnostic performance in oncology, perfusion imaging with that modality is more practical than in the past and overcomes existing limitations of SPECT MPI. Advantages of PET include more reliable quantification of absolute myocardial blood flow, the routine use of computed tomography for attenuation correction, a higher spatiotemporal resolution and a higher count sensitivity. Current PET radiotracers such as rubidium-82 (half-life, 76 s), oxygen-15 water (2 min) or nitrogen-13 ammonia (10 min) are labeled with radionuclides with very short half-lives, necessitating that stress imaging is performed under pharmacological vasodilator stress instead of exercise testing. However, with the introduction of novel 18F-labeled MPI PET radiotracers (half-life, 110 min), the intrinsic advantages of PET can be combined with exercise testing. Additional advantages of those radiotracers include, but are not limited to: potentially improved cost-effectiveness due to the use of pre-existing delivery systems and superior imaging qualities, mainly due to the shortest positron range among available PET MPI probes. In the present review, widely used PET MPI radiotracers will be reviewed and potential novel 18F-labeled perfusion radiotracers will be discussed.