Perfusion Imaging Research Articles

Diagnostic Performance of Quantitative Perfusion Cardiac Magnetic Resonance Imaging in Patients with Prior Coronary Artery Disease.

The diagnostic performance of quantitative perfusion cardiac magnetic resonance (QP-CMR) imaging has scarcely been evaluated in patients with a history of coronary artery disease (CAD) and new onset chest pain. The present study compared the diagnostic performance of automated QP-CMR for detection of fractional flow reserve (FFR) defined hemodynamically significant CAD with visual assessment of first-pass stress perfusion CMR (v-CMR) and quantitative [15O]H2O positron emission tomography (PET) imaging in a true head-to-head fashion in patients with prior CAD. This PACIFIC-2 substudy included 145 symptomatic chronic coronary symptom patients with prior myocardial infarction (MI) and/or percutaneous coronary intervention (PCI). All patients underwent dual-sequence, single bolus perfusion CMR and [15O]H2O PET perfusion imaging followed by invasive coronary angiography with three-vessel FFR. Hemodynamically significant CAD was defined as an FFR ≤0.80. QP-CMR, v-CMR and PET exhibited a sensitivity of 66%, 67%, and 80%, respectively, whereas specificity was 60%, 62%, and 63%. Sensitivity of QP-CMR was lower than PET (P=0.015), whereas specificity of QP-CMR and PET was comparable. Diagnostic accuracy and area under the curve (AUC) of QP-CMR (64% and 0.66) was comparable to both v-CMR (66% [P=NS] and 0.67 (P=NS]) and PET (74% [P=NS] and 0.78 [P=NS]). In patients with prior MI and/or PCI, the diagnostic performance of QP-CMR was comparable to visual assessment of first-pass stress perfusion CMR and quantitative [15O]H2O PET for the detection of hemodynamically significant CAD as defined by FFR.

SPECT-MPI iterative denoising during the reconstruction process using a two-phase learned convolutional neural network

PurposeThe problem of image denoising in single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is a fundamental challenge. Although various image processing techniques have been presented, they may degrade the contrast of denoised images. The proposed idea in this study is to use a deep neural network as the denoising procedure during the iterative reconstruction process rather than the post-reconstruction phase. This method could decrease the background coefficient of variation (COV_bkg) of the final reconstructed image, which represents the amount of random noise, while improving the contrast-to-noise ratio (CNR).MethodsIn this study, a generative adversarial network is used, where its generator is trained by a two-phase approach. In the first phase, the network is trained by a confined image region around the heart in transverse view. The second phase improves the network’s generalization by tuning the network weights with the full image size as the input. The network was trained and tested by a dataset of 247 patients who underwent two immediate serially high- and low-noise SPECT-MPI.ResultsQuantitative results show that compared to post-reconstruction low pass filtering and post-reconstruction deep denoising methods, our proposed method can decline the COV_bkg of the images by up to 10.28% and 12.52% and enhance the CNR by up to 54.54% and 45.82%, respectively.ConclusionThe iterative deep denoising method outperforms 2D low-pass Gaussian filtering with an 8.4-mm FWHM and post-reconstruction deep denoising approaches.

Utility of automated CT perfusion software in acute ischemic stroke with large and medium vessel occlusion.

Early diagnosis of large vessel occlusion (LVO) in acute stroke often requires CT angiography (CTA). Automated CT perfusion (CTP) software, which identifies blood flow abnormalities, enhances LVO diagnosis and patient selection for endovascular thrombectomy (EVT). This study evaluates the sensitivity of automated CTP images in detecting perfusion abnormalities in patients with acute ischemic stroke (AIS) and LVO or medium vessel occlusion (MeVO), compared to CTA. We screened acute ischemic stroke patients presenting within 24 h who underwent CT, CTA, and CTP as per institutional protocol. RAPID AI software processed CTP images, while neuroradiologists reviewed CTA for intracranial arterial occlusions. Sensitivity, specificity, and accuracy of automated CTP maps in detecting occlusions were assessed. Of 790 screened patients, 31 were excluded due to lack of RAPID CTP data or poor-quality scans, leaving 759 for analysis. The median age was 71 years (IQR: 61-81), with 47% female. Among them, 678 had AIS, and 81 had AIS ruled out. CTA identified arterial occlusion in 562 patients (74%), with corresponding CTP abnormalities in 537 patients (Tmax > 6 sec). In the 197 without occlusion, CTP was negative in 161. Automated CTP maps had a sensitivity of 95.55% (CI 95: 93.50-97.10%), specificity of 81.73% (CI 95: 75.61-86.86%), negative predictive value of 98.22% (CI 95: 97.39-98.79%), positive predictive value of 63.54% (CI 95: 56.46-70.09%), and overall accuracy of 85.18% (CI 95: 82.45-87.64%). Automated CTP maps demonstrated high sensitivity and negative predictive value for LVOs and MeVOs, suggesting their usefulness as a rapid diagnostic tool, especially in settings without expert neuroradiologists.

CT perfusion imaging in aneurysmal subarachnoid hemorrhage. State of the art.

CT perfusion (CTP) images can be easily and rapidly obtained on all modern CT scanners and have become part of the routine imaging protocol of patients with aneurysmal subarachnoid haemorrhage (aSAH). There is a growing body of evidence supporting the use of CTP imaging in these patients, however, there are significant differences in the software packages and methods of analysing CTP. In. addition, no quantitative threshold values for tissue at risk (TAR) have been validated in this patients' population. Here we discuss the contribution of the technique in the identification of patients at risk of aSAH-related delayed cerebral ischemia (DCI) and in the assessment of the response to endovascular rescue therapy (ERT). We also address the limitations and pitfalls of automated CTP postprocessing that are specific to aSAH patients as compared to acute ischemic stroke (AIS).

High Hypoperfusion Intensity Ratio Is Independently Associated with Very Poor Outcomes in Large Ischemic Core Stroke.

Recent advances have highlighted the efficacy of endovascular thrombectomy (EVT) in patients with large ischemic core stroke, yet asignificant portion still experience very poor outcomes, defined as a90-day modified Rankin Score (mRS) of 5-6. This study aims to investigate the hypoperfusion intensity ratio (HIR) as aprognostic imaging parameter for these outcomes. In amulticenter retrospective cohort study, data from consecutive patients undergoing EVT for acute ischemic stroke with large vessel occlusion (AIS-LVO) at two comprehensive stroke centers were analyzed. The study included patients with an Alberta Stroke Program Early CT Score (ASPECTS) of5 or less and utilized pretreatment perfusion imaging to calculate HIR. The primary outcome was very poor outcomes (90days mRS 5-6). Among 102 patients included, 59 (57.8%) had very poor outcome (90days mRS 5-6). Multivariable logistic regression analysis adjusting for multiple covariates including admission National Institutes of Health Stroke Scale (NIHSS) and EVT revealed that higher admission NIHSS (adjusted odds ratio [aOR] 1.224, 95% CI 1.089-1.374, p = 0.001) and HIR (aOR per 0.1 incremental change, 1.34, 95% CI 1.02-1.82, P = 0.042) were independently associated with very poor outcomes. This study demonstrates that admission NIHSS and HIR are independently associated with very poor outcome (90days mRS 5-6) in patients with large ischemic core strokes. These findings highlight the importance of collateral status and perfusion imaging in predicting outcomes in this patient population, suggesting apotential role for HIR in the triage and management of large core stroke patients.

Large ischemic core defined by visually assessed ASPECTS predicts functional outcomes comparably accurate to automated CT perfusion in the 6-24 h window.

Automated CT perfusion (aCTP) is commonly used to select patients with anterior circulation large vessel occlusion (aLVO) for endovascular treatment (EVT). The equivalence of visually assessed Non-contrast CT Alberta Stroke Program Early CT Scores (ASPECTS) and aCTP based selection in predicting favorable functional outcomes remains uncertain. Retrospective multicenter study of adult aLVO patients from the Swiss Stroke Registry (2014-2021) treated with EVT or best medical treatment 6-24 h after stroke onset. We assessed ASPECTS on non-contrast CT visually and ischemic core volumes on aCTP, defining ASPECTS 0-5 and aCTP CBF < 30% volumes ⩾50 mL as large ischemic cores. We used logistic regression to explore the association between CT modalities and favorable functional outcomes (modified Rankin Scale [mRS] score shift toward lower categories) at 3 months. Receiver operating characteristic (ROC) curve analysis compared the predictive accuracy of visually assessed ASPECTS and aCTP ischemic core for favorable outcomes (mRS 0-2) at 3 months. Of 210 patients, 11.4% had ASPECTS 0-5, and 12.9% aCTP core volumes ⩾50 mL. Within the same model, ASPECTS but not aCTP core volumes were associated with favorable outcomes (ASPECTS: acOR 1.85, 95%CI 1.27-2.70, p = 0.001). The ROC curve analyses showed comparable diagnostic accuracy in predicting favorable functional outcomes (mRS 0-2) at 3 months (ROC areas: ASPECTS 0.80 [95%CI 0.74-0.86] vs aCTP core 0.79 [95%CI 0.72-0.85]). In patients with aLVO, visually assessed ASPECTS showed at least comparable accuracy to automatically generated CTP core volumes in predicting functional outcomes at 3 months.

Diagnosing myocardial ischemia of obstructive coronary artery disease using dynamic computed tomography myocardial perfusion imaging: optimization of relative myocardial blood flow ratio.

To compare the diagnostic efficacy of different relative myocardial blood flow (MBF) ratios in computed tomography perfusion (CTP) for myocardial ischemia in patients with obstructive coronary artery disease (CAD). Between October 2020 and March 2024, patients with suspected or known obstructive CAD who underwent CTP + coronary computed tomography angiography and invasive coronary angiography/fractional flow reserve were retrospectively selected. Patients and vessels were categorized into ischemia and non-ischemia groups. The diagnostic efficacies of the three relative MBF ratios were compared in patients with obstructive CAD. This study included 48 patients (144 vessels). Notably, 34 of the 48 patients (70.83%) and 49 of the 144 vessels (34.03%) were considered to have myocardial ischemia. The area under the curve of Ratio-hi (0.944, 95% confidence interval: 0.893-0.976) was higher than those of Ratio-av, Ratio-Q3, and MBF-lowest; However, no statistical differences were found (P>0.005). The cutoff value for detecting Ratio-hi was 0.667, and the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were 91.8%, 83.2%, 75%, 95.24%, and 86.81%, respectively. Relative MBF ratios, especially Ratio-hi, demonstrated excellent performance and exhibited greater robustness in diagnosing myocardial ischemia in patients with obstructive CAD.

9398 Early Identification of Impending Thyroid Storm Leading to Improved Thyrotoxic Induce Cardiomyopathy

Abstract Disclosure: D.H. Sacoto: None. D. Patel: None. A. De Rosairo: None. K. Madani: None. B. Singh: None. A. Bonilla Campos: None. R. Belokovskaya: None. F. Alberto A.: None. Introduction: Heart failure can be the leading presentation in 6% of thyroid storm cases and is the leading cause of death, particularly in elderly patients. However, its importance lies in symptom control and heart function reversibility once the euthyroid state is achieved. We present a caseof thyroid storm-induced atrial fibrillation (Afib) leading to severe systolic dysfunction. Case: A 61-year-old female with a history of Graves’ disease (GD) presented to the ED with two months of palpitations and one week of shortness of breath. There were bibasilar lung crackles, irregular heart rhythm, pedal edema, and thyromegaly at the examination. EKG was consistent with Afib with rapid ventricular response (123-135 beats per minute); She was tachypneic (respiratory rate: 40 per minute) and hypoxemic (87% O2 saturation), which required bilevel positive airway pressure. Otherwise, hemodynamically stable (BP: 127/106 mmHg). Laboratories showed negative troponin T (&amp;lt;0.010 ng/mL, n &amp;lt;0.01 ng/mL). However, elevation of Pro-B-type natriuretic peptide (6000 pg/mL, n &amp;lt;125 pg/mL), an x-ray displaying bibasilar pleural effusions and an echocardiogram demonstrating a severely reduced ejection fraction (EF) (21%, n 50-70%), myocardial perfusion scan was normal. Thyroid evaluation showed a suppressed TSH (&amp;lt;0.01 uIU/mL, n 0.27-4.20 uIU/mL) with elevated free T4 (5.8 ng/dL, n 0.9-1.8 ng/dL), free T3 (202 ng/dL, n 2.0-4.4 ng/dL), and TSI (8.25 IU/L, n 0-0.55 IU/L). A thyroid ultrasound revealed increased vascular flow on the left thyroid lobe. A Burh-Schakowsky score of 45 points was consistent with impending thyroid storm. She was started on methimazole, cholestyramine, and propranolol. Three months follow-up, she was asymptomatic, TSH normalized (4.12 uIU/mL), and mild improvement of cardiac EF 25%. Discussion: A thyroid storm in the setting of GD often presents after precipitating factors such as surgery, infection, or, as in our case, anti-thyroid medication non-compliance. Increased thyroid hormone levels upregulate cardiac β receptors, enhancing sensitivity to sympathetic innervation. These can shorten the refractory period of cardiomyocytes, leading to tachyarrhythmias, with Afib occurring in 20% of patients. Chronic tachycardia finally impairs left ventricle function, with heart failure as an outcome. A high index of suspicion and the ability of early diagnosis of impending thyroid storm is critical since the first laboratory confirmation is often delayed, and second, either anti-thyroid medication, radioactive iodine ablation or thyroidectomy, in addition to non-selective beta-blockers, can reverse cardiac dysfunction and lead to clinical improvement as early as 12 -Twenty-four hours of medical treatment. In our case, the early diagnosis and treatment of thyroid storm, in addition to the rate control prevented a deadly outcome and contributed to the improvement of heart failure. Presentation: 6/1/2024

The application of mass defect percentage in the evaluation of acute coronary syndrome.

White blood cells, neutrophils, lymphocytes, and neutrophil-to-lymphocyte ratio (NLR) distribution patterns in patients with anatomic coronary disease have previously been associated with cardiac events such as myocardial infarct size, complications, and prognosis. However, it remains unknown whether myocardial perfusion mass defect percentage (MDP) obtained from gated myocardial perfusion imaging (G-MPI) correlates with these hematological parameters. Therefore, our research aimed to investigate the application of MDP in the evaluation of acute coronary syndrome (ACS). Thirty-six patients with ACS underwent single-photon emission computed tomography/computed tomography using retrospective electrocardiography gating during the resting state. The primary outcome was the percentage of left ventricular mass with abnormal myocardial perfusion (i.e. MDP) in G-MPI. Furthermore, the correlation between myocardial perfusion MDP and lymphocyte count, neutrophil count, white blood cell count, and NLR was calculated. In addition, we explored the relationship of myocardial perfusion MDP with other cardiac function parameters obtained from G-MPI, such as summed rest score, left ventricular ejection fraction, end-systolic volume, and end-diastolic volume. Myocardial perfusion MDP significantly correlated with white blood cell count, neutrophil count, and NLR (P < 0.01). Furthermore, these hematological parameters were significantly different between low and high MDP groups. Additionally, myocardial perfusion MDP negatively correlated with end-systolic volume (r = -0.615) and left ventricular ejection fraction (r = -0.657). Myocardial perfusion MDP has a high correlation with inflammatory cell counts and cardiac function parameters obtained from G-MPI in ACS; this may be of help in the evaluation and treatment of these patients.

Segmentation of acute ischemic stroke lesions based on deep feature fusion

Acute ischemic stroke (AIS) is a common brain disease worldwide, and diagnosing AIS requires effectively utilizing information from multiple Computed Tomography Perfusion (CTP) maps. As far as we know, most methods independently process each CTP map or fail to fully utilize medical prior information when integrating the information from CTP maps. Considering the characteristics of AIS lesions, we propose a method for efficient information fusion of CTP maps to achieve accurate segmentation results. We propose Window Multi-Head Cross-Attention Net (WMHCA-Net), which employs a multi-path U-shaped architecture for encoding and decoding. After encoding, multiple independent windowed cross-attentions are used to deeply integrate information from different maps. During the decoding phase, a Channel Cross-Attention (CCA) module is utilized to enhance information recovery during upsampling. We also added a segmentation optimization module to optimize low-resolution segmentation results, improving the overall performance. Finally, experimental results demonstrate that our proposed method exhibits strong balance and excels across multiple metrics. It can provide more accurate AIS lesion segmentation results to assist doctors in evaluating patient conditions. Our code are available at https://github.com/MTVLab/WMHCA-Net.

Enhancing Stroke Recognition: A Comparative Analysis of Balance and Eyes-Face, Arms, Speech, Time (BE-FAST) and Face, Arms, Speech, Time (FAST) in Identifying Posterior Circulation Strokes.

Background/Objectives: Posterior circulation stroke (PCS) poses a diagnostic challenge due to the diverse and subtle clinical manifestations. While the FAST (Face, Arms, Speech, Time) mnemonic has proven effective in identifying anterior circulation stroke, its sensitivity to posterior events is less clear. Recently, the addition of Balance and Eyes to the mnemonic has been proposed as a more comprehensive tool for stroke recognition. Despite this, evidence directly comparing the effectiveness of BE-FAST and FAST in identifying PCS remains limited. Methods: A retrospective analysis was performed on stroke calls at a comprehensive stroke centre, Sydney, Australia. BE-FAST symptoms first assessed at an emergency department triage were recorded, along with automated acute computerised tomography perfusion (CTP) imaging findings. Haemorrhagic strokes were excluded from analysis. An ischaemic stroke diagnosis was confirmed 48-72 h later with magnetic resonance imaging (MRI) brain. The performance of 1. BE-FAST and FAST and 2. BE-FAST and CTP in the hyperacute detection of posterior circulation ischaemic stroke was compared. Results: Out of 164 identified ischaemic infarcts confirmed on MRIs, 46 were PCS. Of these, 27 were FAST-positive, while 45 were BE-FAST-positive. Overall, BE-FAST demonstrated a higher sensitivity compared to FAST in identifying PCS (97.8 vs. 58.7) but suffered from a lower specificity (10.0 vs. 39.8). Notably, 39.1% (n = 18) of patients with PCS would have been missed if only FAST were used. Furthermore, of the 26 PCS negative on CTP, 25 were BE-FAST-positive, and 14 were FAST-positive. Conclusions: The incorporation of Balance and Eye assessments into the FAST protocol improves PCS detection, although may yield more false positives.

Deep Learning Denoising Improves CT Perfusion Image Quality in the Setting of Lower Contrast Dosing: A Feasibility Study.

Considering recent iodinated contrast shortages and a focus on reducing waste, developing protocols with lower contrast dosing while maintaining image quality through artificial intelligence is needed. This study compared reduced iodinated contrast media and standard dose CTP acquisitions, and the impact of deep learning denoising on CTP image quality in preclinical and clinical studies. The effect of reduced X-ray mAs dose was also investigated in preclinical studies. Twelve swine underwent 9 CTP examinations each, performed at combinations of 3 different x-ray (37, 67, and 127 mAs) and iodinated contrast media doses (10, 15, and 20 mL). Clinical CTP acquisitions performed before and during the iodinated contrast media shortage and protocol change (from 40 to 30 mL) were retrospectively included. Eleven patients with reduced iodinated contrast media dosages and 11 propensity-score-matched controls with the standard iodinated contrast media dosages were included. A residual encoder-decoder convolutional neural network (RED-CNN) was trained for CTP denoising using k-space-weighted image average filtered CTP images as the target. The standard, RED-CNN-denoised, and k-space-weighted image average noise-filtered images for animal and human studies were compared for quantitative SNR and qualitative image evaluation. The SNR of animal CTP images decreased with reductions in iodinated contrast media and milliampere-second doses. Contrast dose reduction had a greater effect on SNR than milliampere-second reduction. Noise-filtering by k-space-weighted image average and RED-CNN denoising progressively improved the SNR of CTP maps, with RED-CNN resulting in the highest SNR. The SNR of clinical CTP images was generally lower with a reduced iodinated contrast media dose, which was improved by the k-space-weighted image average and RED-CNN denoising (P < .05). Qualitative readings consistently rated RED-CNN denoised CTP as the best quality, followed by k-space-weighted image average and then standard CTP images. Deep learning-denoising can improve image quality for low iodinated contrast media CTP protocols, and could approximate standard iodinated contrast media dose CTP, in addition to potentially improving image quality for low milliampere-second acquisitions.

Baseline Blood Pressure Was Associated with Hemispheric Cerebral Blood Flow in Acute Small Subcortical Infarcts

Introduction: While increased baseline blood pressure (BP) is a prevalent comorbidity in the acute phase of ischemic stroke, the association between baseline BP and the state of hemispheric perfusion in patients with acute small subcortical infarcts (SSIs) has not been studied in detail. The aim of this study was to investigate the relationship between baseline BP and hemispheric cerebral blood flow (CBF) in acute SSIs. Methods: This retrospective study included 101 patients with acute SSIs. Baseline hemispheric CBF was assessed through co-registration of baseline CT perfusion imaging and follow-up diffusion-weighted imaging. The association between baseline BP, CBF, and different cerebral small vessel disease (CSVD) biomarkers was assessed. Results: Baseline systolic BP (SBP) and diastolic BP (DBP) were negatively associated with contralateral hemispheric CBF after multivariate-adjusted linear analysis (SBP: β = −0.001, 95% CI: −0.002 to 0.000, p = 0.030; DBP: β = −0.002, 95% CI: −0.003∼0.001, p = 0.006). Among other CSVD biomarkers, the presence of any cerebral microbleeds showed a significant association with lower CBF in the contralateral hemisphere of the infarct lesion (r = −0.270, p = 0.035). Conclusion: In patients with acute SSIs, increased baseline BP was associated with reduced CBF in the contralateral hemisphere of the infarct lesion, which probably could be interpreted by the exacerbation of the CSVD burden, suggesting a potential mechanistic link between BP autoregulation dysfunction and the aggravation of neurovascular impairment in SSIs.

The Updated Registry of Fast Myocardial Perfusion Imaging with Next-Generation SPECT (REFINE SPECT 2.0).

The Registry of Fast Myocardial Perfusion Imaging with Next-Generation SPECT (REFINE SPECT) has been expanded to include more patients and CT attenuation correction imaging. We present the design and initial results from the updated registry. Methods: The updated REFINE SPECT is a multicenter, international registry with clinical data and image files. SPECT images were processed by quantitative software and CT images by deep learning software detecting coronary artery calcium (CAC). Patients were followed for major adverse cardiovascular events (MACEs) (death, myocardial infarction, unstable angina, late revascularization). Results: The registry included scans from 45,252 patients from 13 centers (55.9% male, 64.7 ± 11.8 y). Correlating invasive coronary angiography was available for 3,786 (8.4%) patients. CT attenuation correction imaging was available for 13,405 patients. MACEs occurred in 6,514 (14.4%) patients during a median follow-up of 3.6 y (interquartile range, 2.5-4.8 y). Patients with a stress total perfusion deficit of 5% to less than 10% (unadjusted hazard ratio [HR], 2.42; 95% CI, 2.23-2.62) and a stress total perfusion deficit of at least 10% (unadjusted HR, 3.85; 95% CI, 3.56-4.16) were more likely to experience MACEs. Patients with a deep learning CAC score of 101-400 (unadjusted HR, 3.09; 95% CI, 2.57-3.72) and a CAC of more than 400 (unadjusted HR, 5.17; 95% CI, 4.41-6.05) were at increased risk of MACEs. Conclusion: The REFINE SPECT registry contains a comprehensive set of imaging and clinical variables. It will aid in understanding the value of SPECT myocardial perfusion imaging, leverage hybrid imaging, and facilitate validation of new artificial intelligence tools for improving prediction of adverse outcomes incorporating multimodality imaging.

Physiological provocation compared to acetazolamide in the assessment of cerebral hemodynamics: a case report

BackgroundSevere large vessel disease may lead to cerebral hemodynamic failure that critically impairs cerebral blood flow (CBF) regulation elevating the risk of ischemic events. Assessment of the condition is often based on changes in CBF during vasodilatation; however, pharmacologically induced vasodilation does not reflect the physiological condition during an ischemic event caused by hemodynamic failure. We compared a [15O]H2O PET brain scan during vasodilation to a [99mTc]HMPAO SPECT brain scan during an ongoing transient ischemic attack (TIA).Case presentationA single patient presenting with limb-shaking TIA underwent CT, Digital Subtraction Angiography, and two different modalities of cerebral perfusion scans: [15O]H2O PET and [99mTc]HMPAO SPECT. Acetazolamide was used in the PET scan to induce vasodilatation, and during the SPECT scan physiological stress, standing up rapidly, was used to induce limb-shaking TIA. CT-angiography and Digital Subtraction Angiography revealed an occlusion in the distal part of the right A2 segment of the anterior cerebral artery, with a corresponding infarction in the watershed area. Collaterals supplied the main vascular territory of the anterior cerebral artery. During rest, neither perfusion modalities demonstrated reduced perfusion outside of the ischemic core. However, we found a pronounced difference between the PET utilizing acetazolamide and the SPECT during the TIA. The PET scan demonstrated relative hypoperfusion in vascular territory supplied by collaterals, while the area around the ischemic core was not affected. Contrary, the SPECT had only minor relative hypoperfusion in the collateral-supplied area, whereas the watershed area proximal to the infarct core had pronounced relative hypoperfusion.ConclusionsThe observed discrepancy in compromised areas during physiological provocation compared to pharmacological induced vasodilation questions the use of an unphysiological stressor for assessment of cerebrovascular hemodynamics. A physiological provocation test may achieve more clinically relevant evaluation.

Utility of CT perfusion in seizures and rhythmic and periodic patterns

ObjectiveCT hyper-perfusion has been reported in non-convulsive status epilepticus (NCSE), while its occurrence and relevance after single seizures or with rhythmic and periodic patterns (RPPs) that lie along the ictal-interictal continuum (IIC), remain unclear. The goal of the study is to assess the role of CT perfusion (CTP) in diagnosing patients with clinical seizures, subclinical seizures, or RPPs that lie along the IIC, to help in the clinical assessment of these entities. MethodsWe retrospectively reviewed inpatients who underwent a CTP and an EEG within 6 h of each other. CTP and EEGs were blindly reviewed independent of electronic medical records. ResultsOut of 103 patients, 15 patients (15 %) demonstrated hyper-perfusion, 40 patients (39 %) had hypo-perfusion, while 48 patients (47 %) had normal CTP. Patients with focal CTP hyperperfusion were more likely to have clinical seizures, electrographic seizures, and/or lateralized rhythmic periodic patterns (RPPs) compared to those without CTP hyperperfusion. Focal CTP hyper-perfusion had 34 % sensitivity and 96 % specificity for identifying patients with clinical seizures, and a 40 % sensitivity and 92 % specificity for identifying patients with electrographic seizures or lateralized RPP. Although the numbers were small, none of the patients with generalized periodic discharges or generalized rhythmic delta activity had CTP hyper-perfusion. ConclusionsFocal CTP hyper-perfusion has low sensitivity but high specificity for identifying patients with seizures and lateralized RPPs, and may be considered in the clinical assessment of patients where the clinical information are unclear or insufficient. SignificanceThe presence of CTP hyper-perfusion should alert the physician to the possibility of an ictal related etiology accounting for the patient’s symptoms.

Combined Oxygen-Enhanced MRI and Perfusion Imaging Detect Hypoxia Modification from Banoxantrone and Atovaquone and Track Their Differential Mechanisms of Action.

Oxygen-enhanced MRI (OE-MRI) has shown promise for quantifying and spatially mapping tumor hypoxia, either alone or in combination with perfusion imaging. Previous studies have validated the technique in mouse models and in patients with cancer. Here, we report the first evidence that OE-MRI can track change in tumor oxygenation induced by two drugs designed to modify hypoxia. Mechanism of action of banoxantrone and atovaquone were confirmed using in vitro experiments. Next, in vivo OE-MRI studies were performed in Calu6 and U87 xenograft tumor models, alongside fluorine-18-fluoroazomycin arabinoside PET and immunohistochemistry assays of hypoxia. Neither drug altered tumor size. Banoxantrone reduced OE-MRI hypoxic fraction in Calu6 tumors by 52.5% ± 12.0% (P = 0.008) and in U87 tumors by 29.0% ± 15.8% (P = 0.004) after 3 days treatment. Atovaquone reduced OE-MRI hypoxic fraction in Calu6 tumors by 53.4% ± 15.3% (P = 0.002) after 7 days therapy. PET and immunohistochemistry provided independent validation of the MRI findings. Finally, combined OE-MRI and perfusion imaging showed that hypoxic tissue was converted into necrotic tissue when treated by the hypoxia-activated cytotoxic prodrug banoxantrone, whereas hypoxic tissue became normoxic when treated by atovaquone, an inhibitor of mitochondrial complex III of the electron transport chain. OE-MRI detected and quantified hypoxia reduction induced by two hypoxia-modifying therapies and could distinguish between their differential mechanisms of action. These data support clinical translation of OE-MRI biomarkers in clinical trials of hypoxia-modifying agents to identify patients demonstrating biological response and to optimize treatment timing and scheduling. Significance: For the first time, we show that hypoxic fraction measured by oxygen-enhanced MRI (OE-MRI) detected changes in tumor oxygenation induced by two drugs designed specifically to modify hypoxia. Furthermore, when combined with perfusion imaging, OE-MRI hypoxic volume distinguished the two drug mechanisms of action. This imaging technology has potential to facilitate drug development, enrich clinical trial design, and accelerate clinical translation of novel therapeutics into clinical use.

Thrombectomy Outcomes for Anterior Circulation Stroke in the 6-24 h Time Window Solely Based On NCCT and CTA: ASingle Center Study.

Since perfusion imaging may be unavailable in smaller hospitals, alternative imaging selection methods for acute ischemic stroke can improve outcomes and optimize resources. This study assessed the safety and effectiveness of using imaging criteria other than DEFUSE3 and DAWN for thrombectomy beyond 6 h from symptom onset in patients stroke in the anterior circulation. This is aretrospective, single-center analysis of consecutive patients with large vessel occlusion in the anterior circulation undergoing thrombectomy. Patients were categorized into two groups based on the collateral status (moderate collaterals and good collaterals). Among 198 patients, 106 (54%) met the inclusion criteria and were analyzed. Good collateral status was observed in 78 (74%) patients. Patients with good collaterals showed significantly lower mRS scores at discharge and at 90days compared to their counterparts with moderate collateral status (4 (3-4) vs.4 (4-5); p = 0.001 and 2 (0-4) vs.6 (3-6); p < 0.001, respectively). More patients with good collateral status achieved favorable outcomes at 90days compared to those with moderate status (48 (61.5%) vs.5 (17.9%); p < 0.001). Good collaterals were an independent predictor of good clinical outcomes at 90days (OR = 1.31, 95% CI: 1.13-1.53, p < 0.001). Selecting patients for endovascular treatment of acute ischemic stroke using non-contrast CT and CT angiography shows 90-day outcomes similar to the DAWN and DEFUSE-3trials. Using collateral status on CT angiography can predict favorable outcomes after mechanical thrombectomy in resource-limited settings where perfusion imaging is unavailable.

Longitudinal changes in the US emergency department use of advanced neuroimaging in the mechanical thrombectomy era.

To describe ED neuroimaging trends across the time-period spanning the early adoption of endovascular therapy for acute stroke (2013-2018). We performed a retrospective, cross-sectional study of ED visits using the 2013-2018 National Emergency Department Sample, a 20% sample of ED encounters in the United States. Neuroimaging use was determined by Common Procedural Terminology (CPT) code for non-contrast head CT (NCCT), CT angiography head (CTA), CT perfusion (CTP), and MRI brain (MRI) in non-admitted ED patients. Data was analyzed according to sampling weights and imaging rates were calculated per 100,000 ED visits. Multivariate logistic regression analysis was performed to identify hospital-level factors associated with imaging utilization. Study population comprised 571,935,906 weighted adult ED encounters. Image utilization increased between 2013 and 2018 for all modalities studied, although more pronounced in CTA (80.24/100,000 ED visits to 448.26/100,000 ED visits (p < 0.001)) and CTP (1.75/100,000 ED visits to 28.04/100,000 ED visits p < 0.001)). Regression analysis revealed that teaching hospitals were associated with higher odds of high CTA utilization (OR 1.88 for 2018, p < 0.05), while low-volume EDs and public hospitals showed the reverse (OR 0.39 in 2018, p < 0.05). We identified substantial increases in overall neuroimaging use in a national sample of non-admitted emergency department encounters between 2013 and 2018 with variability in utilization according to both patient and hospital properties. Further investigation into the appropriateness of this imaging is required to ensure that access to acute stroke treatment is balanced against the timing and cost of over-imaging.

Decreased Quantitative Cerebral Blood Volume Is Associated With Poor Outcomes in Large Core Patients.

Recent large core trials have highlighted the effectiveness of mechanical thrombectomy (MT) in acute ischemic stroke with large vessel occlusion. Variable perfusion-imaging thresholds and poor Alberta Stroke Program Early Computed Tomography Score reliability underline the need for more standardized, quantitative ischemia measures for MT patient selection. We aimed to identify the computed tomography perfusion parameter most strongly associated with poor outcomes in patients with acute ischemic stroke-large vessel occlusion with significant ischemic cores. In this study from 2 comprehensive stroke centers from 2 comprehensive stroke centers within the Johns Hopkins Medical Enterprise (Johns Hopkins Hospita-East Baltimore and Bayview Medical Campus) from July 29, 2019 to January 29, 2023 in a continuously maintained database, we included patients with acute ischemic stroke-large vessel occlusion with ischemic core volumes defined as relative cerebral blood flow <30% and ≥50 mL on computed tomography perfusion or Alberta Stroke Program Early Computed Tomography Score <6. We used receiver operating characteristics to find the optimal cutoff for parameters like cerebral blood volume (CBV) <34%, 38%, 42%, and relative cerebral blood flow >20%, 30%, 34%, 38%, and time-to-maximum >4, 6, 8, and 10 seconds. The primary outcome was unfavorable outcomes (90-day modified Rankin Scale score 4-6). Multivariable models were adjusted for age, sex, diabetes, baseline National Institutes of Health Stroke Scale, intravenous thrombolysis, and MT. We identified 59 patients with large ischemic cores. A receiver operating characteristic curve analysis showed that CBV<42% ≥68 mL is associated with unfavorable outcomes (90-day modified Rankin Scale score 4-6) with an area under the curve of 0.90 (95% CI, 0.82-0.99) in the total and MT-only cohorts. Dichotomizing at this CBV threshold, patients in the ≥68 mL group exhibited significantly higher relative cerebral blood flow, time-to-maximum >8 and 10 seconds volumes, higher CBV volumes, higher HIR, and lower CBV index. The multivariable model incorporating CBV<42% ≥68 mL predicted poor outcomes robustly in both cohorts (area under the curve for MT-only subgroup was 0.87 [95% CI, 0.75-1.00]). CBV<42% ≥68 mL most effectively forecasts poor outcomes in patients with large-core stroke, confirming its value alongside other parameters like time-to-maximum in managing acute ischemic stroke-large vessel occlusion.