Perfusion Imaging Research Articles

A deep learning approach for quantifying CT perfusion parameters in stroke

Objective. Computed tomography perfusion (CTP) imaging is widely used for assessing acute ischemic stroke. However, conventional methods for quantifying CTP images, such as singular value decomposition (SVD), often lead to oscillations in the estimated residue function and underestimation of tissue perfusion. In addition, the use of global arterial input function (AIF) potentially leads to erroneous parameter estimates. We aim to develop a method for accurately estimating physiological parameters from CTP images.Approach. We introduced a Transformer-based network to learn voxel-wise temporal features of CTP images. With global AIF and concentration time curve (CTC) of brain tissue as inputs, the network estimated local AIF and flow-scaled residue function. The derived parameters, including cerebral blood flow (CBF) and bolus arrival delay (BAD), were validated on both simulated and patient data (ISLES18 dataset), and were compared with multiple SVD-based methods, including standard SVD (sSVD), block-circulant SVD (cSVD) and oscillation-index SVD (oSVD).Main results.On data simulating multiple scenarios, local AIF estimated by the proposed method correlated with true AIF with a coefficient of 0.97 ± 0.04 (P < 0.001), estimated CBF with a mean error of 4.95 ml/100 g min-1, and estimated BAD with a mean error of 0.51 s; the latter two errors were significantly lower than those of the SVD-based methods (P < 0.001). The CBF estimated by the SVD-based methods were underestimated by 10%∼15%. For patient data, the CBF estimates of the proposed method were significantly higher than those of the sSVD method in both normally perfused and ischemic tissues, by 13.83 ml/100 g min-1or 39.33% and 8.55 ml/100 g min-1or 57.73% (P < 0.001), respectively, which was in agreement with the simulation results.Significance. The proposed method is capable of estimating local AIF and perfusion parameters from CTP images with high accuracy, potentially improving CTP's performance and efficiency in diagnosing and treating ischemic stroke.

The hypoperfusion volume has a strong predictive value for hemorrhagic transformation in acute ischemic stroke patients with anterior circulation occlusion after endovascular thrombectomy

ObjectiveIt remains unclear whether hypoperfusion volume elevates the risk of hemorrhagic transformation (HT) after endovascular thrombectomy (EVT) in patients with acute ischemic stroke (AIS). This study aims to investigate the association between hypoperfusion volume and HT after EVT.Materials and methodsWe retrospectively recruited AIS patients with anterior circulation occlusion after receiving EVT from January 2021 to May 2024. The pre-EVT hypoperfusion volume was assessed using computed tomography perfusion, with a hypoperfusion area defined as time-to-maximum > 6s. Multivariable analysis determined whether the hypoperfusion volume served as an independent predictor of symptomatic intracerebral hemorrhage (sICH) or intracerebral hemorrhage (ICH), and its predictive value was evaluated using receiver operating characteristic (ROC) curves.ResultsA total of 115 patients were analyzed, with 55 (47.8%) having ICH and 16 (13.9%) experiencing sICH. The median age was 67, and 28.6% were female. The median core infarct volume was 4.3 ml, and the median hypoperfusion volume was 112.8 ml. After adjusting for potential confounding factors, the hypoperfusion volume remained independently correlated with sICH (OR = 1.008, 95% CI = 1.001–1.015, P = 0.018) and ICH (OR = 1.006, 95% CI = 1.001–1.012, P = 0.033). ROC curve analysis demonstrated that the hypoperfusion volume effectively predicted sICH [(area under the curve (AUC) = 0.702] or ICH (AUC = 0.643).ConclusionThe hypoperfusion volume has a strong predictive value for sICH and ICH in AIS patients with anterior circulation occlusion after EVT. This underscores the necessity of assessing the hypoperfusion volume before EVT, particularly for patients with smaller core infarct volumes in AIS.

Can interactive artificial intelligence be used for patient explanations of nuclear medicine examinations in Japanese?

This study aimed to evaluate the accuracy and validity of patient explanations about nuclear medicine examinations generated in Japanese using ChatGPT- 3.5 and ChatGPT- 4. ChatGPT was used to generate Japanese language explanations for seven single-photon emission computed tomography examinations (bone scintigraphy, brain perfusion imaging, myocardial perfusion imaging, dopamine transporter scintigraphy [DAT scintigraphy], sentinel lymph node scintigraphy, lung perfusion scintigraphy, and renal function scintigraphy) and 18F-fluorodeoxyglucose positron emission tomography. Nineteen board-certified nuclear medicine technologists evaluated the accuracy and validity of the responses using a 5-point scale. ChatGPT- 4 demonstrated significantly higher accuracy and validity than ChatGPT- 3.5, with 77.9% of responses rated as above average or excellent for accuracy, in comparison to 36.3% for ChatGPT- 3.5. For validity, 73.1% of ChatGPT- 4's responses were rated as above average or excellent, in comparison to 19.6% for ChatGPT- 3.5. ChatGPT- 4 outperformed ChatGPT- 3.5 in all examinations, with notable improvements in bone scintigraphy, lung perfusion scintigraphy, and DAT scintigraphy. These findings suggest that ChatGPT- 4 can be a valuable tool for providing patient explanations of nuclear medicine examinations. However, its application still requires expert supervision, and further research is needed to address potential risks and security concerns.

Validation of a novel CT perfusion software compared to RAPID in stroke patients receiving endovascular therapy

Accurate estimate of ischemic core volume (ICV) and penumbra volume (PV) is important in decision-making for endovascular therapies (EVT) and predicting the patient’s clinical outcome. In this study, we compared the performance of a novel automated CT perfusion software UGuard and the Rapid Processing of Perfusion and Diffusion (RAPID). UGuard and RAPID had strong agreement with regard to ICV (ICC 0.92, 95% CI 0.89 – 0.94) and PV (ICC 0.8, 95% CI 0.73 – 0.85) measurements. ICVs measured by UGuard or RAPID were similar in predicting favorable outcome (AUC 0.72 vs. 0.70, P = 0.43), with UGuard measurements having higher specificity. After adjusting for significant clinical covariates, the predictive performance of favorable outcome was excellent for each of the six models incorporating ICV and PV, and the model which incorporated ICV and PV measured by UGuard software package showed the best predictive performance. We concluded that the ICV and PV of CT perfusion images measured by UGuard software package, as well as the capacity to predict favorable outcome of patients following EVT, were comparable to RAPID.

Machine Learning-Based Classification of Anterior Circulation Cerebral Infarction Using Computational Fluid Dynamics and CT Perfusion Metrics

Background: Intracranial atherosclerotic stenosis (ICAS) is a leading cause of ischemic stroke, particularly in the anterior circulation. Understanding the underlying stroke mechanisms is essential for guiding personalized treatment strategies. This study proposes an integrated framework that combines CT perfusion imaging, vascular anatomical features, computational fluid dynamics (CFD), and machine learning to classify stroke mechanisms based on the Chinese Ischemic Stroke Subclassification (CISS) system. Methods: A retrospective analysis was conducted on 118 patients with intracranial atherosclerotic stenosis. Key indicators were selected using one-way ANOVA with nested cross-validation and visualized through correlation heatmaps. Optimal thresholds were identified using decision trees. The classification performance of six machine learning models was evaluated using ROC and PR curves. Results: Time to Maximum (Tmax) &gt; 4.0 s, wall shear stress ratio (WSSR), pressure ratio, and percent area stenosis were identified as the most predictive indicators. Thresholds such as Tmax &gt; 4.0 s = 134.0 mL and WSSR = 86.51 effectively distinguished stroke subtypes. The Logistic Regression model demonstrated the best performance (AUC = 0.91, AP = 0.85), followed by Naive Bayes models. Conclusions: This multimodal approach effectively differentiates stroke mechanisms in anterior circulation ICAS and holds promise for supporting more precise diagnosis and personalized treatment in clinical practice.

Rubidium ions as a novel therapeutic approach for glioblastoma

Glioblastoma (GBM) is a highly aggressive brain tumor with limited treatment options, mainly due to challenges such as incomplete resection and blood–brain barrier limitations. Rubidium, a naturally occurring alkali metal with favorable biocompatibility, widely used in myocardial and tumor perfusion imaging as a blood flow tracer, is repurposed in this study to investigate its potential therapeutic effects and mechanisms against GBM. The impacts of rubidium ions (Rb⁺) on GBM cells were assessed through functional assays evaluating proliferation, migration, invasion, and apoptosis. RNA sequencing and Western blot analyses were employed to investigate molecular mechanisms, while in vivo models were used to evaluate therapeutic efficacy and safety. Rb⁺ treatment significantly suppressed GBM cell proliferation, migration, and invasion, while inducing apoptosis and cell cycle arrest at the G2/M phase. Mechanistic studies revealed that Rb⁺ downregulated the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway, contributing to the induction of apoptosis in tumor cells. In vivo, Rb⁺ exhibited potent anti-tumor activity with no detectable adverse effects on major organs, physiological functions, or behavior in mice. Our findings highlight Rb⁺ as a promising and innovative candidate for GBM therapy, leveraging the PI3K/AKT/mTOR pathway to inhibit tumor growth and promote apoptosis. This study underscores the potential of Rb⁺ in addressing the urgent need for novel GBM treatments, warranting further preclinical and clinical investigations.

First-pass perfusion imaging using cardiovascular magnetic resonance in patients with various cardiac implantable electronic devices.

The number of patients with cardiac implantable electronic devices (CIEDs) is increasing. However, there is limited experience regarding vasodilator-stress cardiovascular magnetic resonance (CMR) and resulting device artifacts on perfusion images. The aim of this study was to determine CMR image quality in patients with different CIED types for CMR-based perfusion stress testing. A total of 156 patients with active CIEDs underwent CMR on a 1.5-Tesla scanner. Both conventional steady-state-free-precession (SSFP) and modified spoiled gradient-echo (sGE) protocols under stress and resting conditions were used to evaluate image artifacts in a 16-segment segment model of the heart. The study group comprised 39% conventional pacemaker (PM), 4% cardiac resynchronization therapy-pacemaker (CRT-P), 38% conventional implantable cardioverter-defibrillator (ICD), 6% cardiac resynchronization therapy-ICD (CRT-D), and 13% subcutaneous ICD (S-ICD) patients. PM-carriers showed only minor image artifacts in both perfusion protocols. Artifacts caused by ICDs were predominantly located in the left-ventricular (LV) inferolateral and anterior segments. S-ICDs showed the highest extent of artifacts with an anterolateral accentuation. The artifact extent was significantly reduced when sGE-based perfusion was used compared to SSFP-based sequences. 69% of the patients received a stress-perfusion protocol, and elective coronary angiography confirmed the presence of coronary stenosis in three cases. No major safety-relevant issues occurred. Myocardial perfusion imaging by CMR is safe and feasible with moderate-to-high image quality in patients with all types of CIEDs, including non-conditional devices, ICDs, and S-ICDs. A sGE-based perfusion protocol should be preferred in patients with left-sided ICDs, CRT-Ds, or S-ICDs.

Automated collateral assessment restricted to the hypoperfused area for distal vessel occlusions in ischemic stroke.

This study aims to: (1) develop and evaluate a quantitative assessment of collateral status in the downstream area of an occluded intracranial artery in acute ischemic stroke and compare this method to middle cerebral artery (MCA)-based assessment; (2) determine the agreement between the automated occlusion-downstream area collateral score (ODACS) and expert raters' assessments, and compare this to inter-rater agreement. Patients from MR CLEAN-NO IV and MR CLEAN Registry with a proximal M1, distal M1, or M2 occlusion were included. Using the hypoperfused area from CT perfusion (CTP) as a proxy for the occlusion-downstream territory and automated vessel segmentations from CT angiography (CTA), ODACS is calculated as the vessel volume ratio between downstream ipsilateral and its contralateral regions. ODACS was compared to a whole MCA-territory approach and evaluated against visual scoring by two expert raters that visually estimated ODACS using CTA and CTP, and their inter-rater agreement. The study included 204 patients with a proximal M1 (52%), distal M1 (32%), or M2 (16%) occlusion. ODACS yielded lower collateral scores than MCA-based scoring for all occlusion locations, with larger differences in more distal occlusions. For M2 occlusions, 58% of patients shifted from good (> 50%) to poor (≤ 50%) collateral filling of the occluded territory using ODACS. Moderate (weighted Cohen's kappa κ = 0.45) inter-rater agreement and fair (κ = 0.35) to moderate (κ = 0.51) ODACS-rater agreement were observed. ODACS yields lower collateral scores compared to MCA-based scoring and is comparable to scores from expert raters. Question CT angiography-based collateral assessment in the MCA territory is inadequate to assess the collateral status in patients with distal vessel occlusions. Findings Our automatedODACS revealed lower collateral scores than traditional whole-territory assessment, especially in distal vessel occlusions. Clinical relevance The more precise evaluation of affected brain territories through automated occlusion-downstream area assessments prevents an overestimation of collateral status in distal occlusions, which could lead to improved patient selection and treatment decisions in acute stroke care.

Assessment of myocardial dysfunction of patients with systemic lupus erythematosus based on myocardial perfusion imaging and analysis of potential influencing factors.

The incidence and prevalence of systemic lupus erythematosus (SLE) have increased annually over the past decade. The involvement of myocardium is one of the main reasons for the poor prognosis of patients with SLE. Identifying myocardial involvement in patients with autoimmune diseases and providing early targeted treatment can improve patient outcomes. The aim of this study is to evaluate myocardial dysfunction in patients with SLE using 99mTc-MIBI rest gated myocardial perfusion imaging (rGMPI) and to investigate factors associated with myocardial dysfunction. 76 patients with SLE were prospectively enrolled in the study and 46 patients without autoimmune diseases or other inflammatory diseases who had undergone 99mTc-MIBI rGMPI were selected as a control group. Results of relevant blood test indicators, echocardiography and rGMPI were recorded, and comparison was made between the two groups. Meanwhile, based on diagnostic results of rGMPI, SLE patients were divided into myocardial dysfunction group and normal myocardial function group and to analyze the influencing factors of myocardial dysfunction in SLE patients. The incidence of myocardial dysfunction was significantly higher in SLE patients than in controls (30.3% vs 0%, 2= 16.131, p < .001). Moderate/severe disease activity, decreased myocardial perfusion and positive anti-SSA/Ro52kDa antibody were associated with impaired myocardial function in SLE patients (OR = 2.753, 5.359, 3.646; p = .049, 0.015, 0.014). Positive anti-SSA/Ro52kDa antibody was is independently correlated with myocardial dysfunction in SLE patients [OR (95% CI) = 3.159 (1.071-9.316), p = .037]. In conclusion, 99mTc-MIBI rGMPI can noninvasively evaluate myocardial dysfunction in patients with SLE and provide evidence for clinical treatment decisions. Positive anti-SSA/Ro52kDa antibody was an independent risk factor for myocardial dysfunction in SLE patients.

Myocardial flow reserve and resting contractility modulate the impact of contractile reserve in patients undergoing rubidum-82 positron emission tomography.

Although ejection fraction reserve (EFR) harbors prognostic value in patients undergoing positron emission tomography (PET) myocardial perfusion imaging (MPI), whether resting EF and myocardial flow reserve (MFR) modulate its prognostic value has not been studied. Consecutive patients undergoing stress/rest MPI using Rb-82 PET between 2019 and 2024 were included. The primary outcome was a composite of death and heart failure (HF) hospitalizations. Multivariable Andersen-Gill Cox models were used to assess the association of EFR with the primary outcome across the spectrum of resting EF and MFR. Restricted cubic splines were used to allow non-linearity. The 50th percentile of EFR served as the reference, with the 25th and 75th percentiles representing low and high EFR. The analysis included 7,737 consecutive patients among whom 463 deaths and 821 HF hospitalizations occurred over a median follow-up of 554 days. A low EFR was associated with a 25% greater risk of the primary outcome (HR: 1.25; 95% CI: 1.16 to 1.35). The association was stronger at higher values of resting EF (HR at EFs of 40% and 70%: 0.99 and 1.21 respectively) and MFR (HR at MFRs of 1 and 3: 1.06 and 1.27 respectively). Similarly, a high EFR carried a protective association that was more pronounced at a higher resting EF and MFR. The prognostic implications of contractile reserve, as measured by EFR, are most pronounced in patients with a higher resting EF and MFR.

Contrast bolus timing in CT-angiography and CT-perfusion: insights from a large clinical dataset.

CT-Perfusion (CTP) is an essential part of stroke imaging. Incomplete coverage of the contrast bolus in CTP can lead to errors in post-processing that might hamper the identification of the infarct core or tissue at risk. However, the arrival of the contrast bolus depends on various technical and patient individual factors. This study investigated whether timing information from CT-angiography (CTA) can be used to optimize bolus coverage in CTP. We retrospectively reviewed cases with a multimodal stroke protocol for suspected ischemic stroke. Information on the contrast injection timing of CTA and CTP was extracted from the DICOM headers. Bolus arrival information were obtained from the CTP scan including peak time, height, and width and correlated with patient age and ejection fraction (the latter available in n = 868). The contrast timing information of the CTA was used to simulate optimized CTP timing. A total of 1,843 cases were included. CTP bolus peak position was associated with peak width (Pearsons's r = 0.89, p < 0.001), age (Pearsons's r = 0.40, p < 0.001), ejection fraction (Pearsons's r=-0.25, p < 0.001), and time to scan initiation based on triggering in CTA (Pearsons's r = 0.83, p < 0.001). Using information of the CTA timing to adjust the CTP timing, the variance of the AIF peak could significantly be reduced (p < 0.001). Our data indicate that patient individual characteristics lead to substantial variances in the contrast bolus arrival which could hamper CTP analysis. To ensure optimized coverage of the contrast bolus. CTP timing can significantly and safely be improved using timing information of preceding CTA.

Brain abscess mimicking a brain tumor only realized during surgery: A case report in a resource strained environment

Background Diagnosis of brain tumors increased in sub-Saharan Africa since the advent of computed tomography (CT)-scans and magnetic resonance imaging (MRI) in these regions, enabling easy diagnosis. However, some histological types of brain tumors can be confusing, especially on CT-scan, simulating other pathologies such as inflammatory granulomas or pyogenic abscesses. MRI, in this instance, with its diffusion-weighted imaging, susceptibility weighted imaging, or perfusion imaging, is important to help with accurate diagnosis. The down side of these imaging facilities, however, is that less and less importance is accorded to proper and detailed history taking. Such a care-free attitude to history taking can be costly, especially in resource strained environments. Case Description We report the case of a 06-year-old child who presented with seizures associated with headaches and vomiting. In this case, proper history taking following the surgical intervention revealed a history of head trauma after a fall with a scalp wound, which was suppurated but later progressed well. The CT scan showed a solid cystic lesion. The first component is a ring enhanced portion (hyperdense ring with the hypodense center, surrounded by edema) with central calcification located in the frontal region, and the second component is a cystic portion located in the temporal region. This lesion with dual component was more suggestive of a tumoral lesion on imaging than an abscess. The child did not benefit from further imaging due to unavailability in the region as well as the socioeconomic status of the family making them incapable of going elsewhere to do it. A decision to surgically excise the lesion was made, and during surgery, we found a well-circumscribed yellowish lesion associated with an arachnoid cyst. The capsule of the lesion was very thick, and after opening it, the content was pus combined with debris. The child did well on antibiotic therapy post-surgery. The follow-up was unremarkable. Conclusion Brain MRI is essential to differentiate some pyogenic brain abscesses from tumors. However, meticulous history taking is important to gather as much information as possible about any medical pathology, which would then be corroborated with the physical examination findings and imaging to increase diagnostic accuracy and minimize misdiagnosis.

Characterization of Traumatic Brain Injury Using Imaging and Physiological Parameters: A Pilot Study.

The study was a cross-sectional study aimed to obtain preliminary data to characterize traumatic brain injuries (TBIs) of Operation Iraqi Freedom/Operation Endurance Freedom (OIF/OEF) in a cohort of insular veterans using perfusion and molecular imaging, and physiologic parameters. The size and location of TBI lesions of 6 veterans were evaluated by quantifying cerebral perfusion and metabolism using Tc99m ethyl-cysteinate dimer SPECT/CT and fluorine-18 fluorodeoxyglucos PET/CT, respectively. Somatosensory evoked potentials were collected, and quality of life was measured by assessing functional status, activities of daily living, and depression levels. The study population included OIF/OEF returning soldiers diagnosed with mild/moderate TBI. Six subjects were enrolled in the study and 4 completed all assessments. The data showed that higher trauma severity might be accompanied by lower levels of independence. Perfusion and metabolic findings were detected in the presence of negative CT. Imaging abnormalities were frequently localized in the frontal lobe. An increased number of perfusion defects compared to metabolic defects were observed. SPECT/CT and PET/CT might have an added value in the diagnosis of patients with mild/moderate TBI. However, a larger study is required to develop new predictive TBI model systems that include functional and molecular nuclear medicine neuroimaging, and physiologic parameters, in the TBI diagnostic algorithm for veterans with probable TBI. The mismatch between perfusion and metabolism might be suggesting the possibility of up-regulation of cerebral glucose transporters/receptors to compensate for diminished perfusion. It can also imply an important role of impaired vasomotor response or endothelial dysfunction in the etiology of TBI. However, remaining functional neurons and neighboring damaged tissue would still likely be overexcited during reorganization for several months post-injury, potentially explaining the increased metabolic uptake in areas of decreased perfusion.

Diagnostic reference level, achievable dose, and effective dose estimation in adult hybrid SPECT myocardial perfusion imaging in Institut Jantung Negara

This study aims to establish the diagnostic reference level (DRL), achievable dose (AD), and effective dose (ED) estimation for adult hybrid SPECT myocardial perfusion imaging (MPI) procedures at Institut Jantung Negara (IJN). 737 subjects referred for MPI studies from January to June 2024 were included in the analysis. These subjects underwent either a one-day or two-day Tc-99 m tetrofosmin protocol using a cardiac-dedicated single-photon emission computed tomography (SPECT), either GE SPECT Discovery NM530c or GE SPECT Ventri. All subjects also underwent a cardiac CT scan via an external positron emission tomography/computed tomography (PET/CT) system, GE Discovery MI Digital Ready for either CT attenuation correction (CTAC) or CT coronary artery calcium score (CAC) protocol, depending on their clinical condition. The one-day protocol showed AD of 240.50 MBq and 691.90 MBq for the first and second injections, respectively, with corresponding DRL of 263.63 MBq and 777.93 MBq. The two-day protocol involved higher ADs of 1106.30 MBq and 1073.00 MBq for the first and second injections, with DRL of 1239.50 MBq and 1221.00 MBq, respectively. In the CTAC protocol, the AD for CT dose index volume (CTDIvol) was 2.8 mGy, with a DRL of 4.3 mGy. The dose length product (DLP) had an AD of 53.1 mGy.cm, compared to a DRL of 78.6 mGy.cm. For the CAC protocol, the CTDIvol had an AD of 4.8 mGy, matching the DRL of 4.8 mGy. The DLP showed an AD of 67.8 mGy.cm, with a DRL of 77.5 mGy.cm. The mean cumulated effective dose (EDCUMULATED) for one-day/CTAC, one-day/CAC, two-day/CTAC, and two-day/CAC was 6.69 ± 1.76 mSv, 7.32 ± 1.37 mSv, 10.13 ± 5.31 mSv, and 13.99 ± 3.24 mSv respectively. The average ED relative contribution by SPECT and CT were found to be 78.3% and 21.7% respectively. The DRL, AD, and ED data were successfully established for local MPI practice, contributing to global efforts to harmonize and enhance radiation safety in MPI practices.

Investigation of total-body applicable compartment models for kinetic modeling in total body 15O-water perfusion PET imaging

Dynamic total-body positron emission tomography (PET) imaging has recently become possible due to the introduction of new-generation imaging systems with increased axial field of view. This enables evaluation of kinetic modeling approaches using compartment models for the entire body simultaneously. Systematic evaluation of the conventionally used approaches is needed to find the best candidates among different compartment models for total body modeling of 15O-water perfusion PET images. Six variations of the 1-tissue-compartment model (1TCM) are evaluated. The models are systematically fitted to mean time activity curves of 20 anatomic structures of interest extracted from a dynamic 15O-water PET rest perfusion images of 58 human subjects, using an image-derived input function from the aorta. The impact of additional parameters for time delay correction (TDC), arterial volume fraction (AVF), and perfusable tissue fraction (PTF) is assessed. The models are evaluated with mean squared error, mean relative error (MRE), and Akaike information criterion (AIC) and by performing Wilcoxon signed-rank tests to see whether the found differences are statistically significant. For 11 out of the 20 anatomic structures, the best model in terms of median AIC was the 1TCM with AVF and TDC but without PTF. The use of TDC resulted in significantly lower AICs for all anatomic structures while the AVF and PTF parameters significantly improved the model performance only occasionally. Between the different organs, the models of pancreas, spleen, myocardium, the example rib, and brain performed very well in terms of MRE. In comparison, the investigated models worked poorly for liver and lung lobes. This paper serves as an initial attempt to evaluate potential approaches to derive an appropriate model for kinetic modeling in total body 15O-water PET perfusion imaging. According to our research, the suitability of 1TCM using a single input function from the aorta in 15O-water PET images depends on the organ of interest. Our results suggest that the use of 1TCM is justified for most anatomic structures and can be used to estimate the cerebral, myocardial, renal, and splenic blood flow. However, we recommend different models for quantification of hepatic and pulmonary blood flow.

Underestimation of Follow-Up Infarct Volume by Acute CT Perfusion Imaging.

It is unknown whether acute CT perfusion (CTP) core imaging may underestimate the follow-up infarct. We hypothesize that infarct underestimation occurs especially in late-presenting patients and that underestimated infarct can partially be detected on baseline noncontrast CT (NCCT). We included patients with acute anterior circulation ischemic stroke who underwent baseline NCCT and CTP imaging, complete endovascular reperfusion, and follow-up MRI from the Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke (DEFUSE 3) trial and a consecutive, monocenter cohort. We divided patients into early (<6 hours) and late (6-24 hours) presenters. We performed semiautomated segmentations of the acute ischemic lesion on NCCT using 5% relative density difference (rNCCT>5%) and used the relative cerebral blood flow <30% to segment the CTP core. On coregistered images, we performed volumetric and voxel-based analyses to compare infarct estimations by imaging modality. Spatial accuracy for the follow-up infarct was assessed using the Dice similarity coefficient (DSC) and balanced accuracy. We included 109 patients with a median age of 70 (interquartile range [IQR] 31-93) years of whom 52% were female. The follow-up infarct was underestimated by the CTP core (mean absolute volume difference [MAVD] = 14 mL [SD 36], p < 0.001), but not by the union lesion (MAVD = 3 mL [SD 32], p = 0.76). Infarct underestimation was greater in late presenters (median 17 mL [IQR 7-33] vs 7 mL [IQR 4-25] in early presenters, p < 0.01) and in patients with poor collaterals (median 20 mL [IQR 8-56] vs 8 mL [IQR 4-20] in patients with good collaterals, p < 0.01). Median 25% of the infarct missed by the CTP core could be detected on baseline rNCCT in late presenters (vs. median 3% in early presenters). The combined rNCCT>5% and CTP core lesion more accurately detected the follow-up infarct compared with the CTP core alone (median DSC 0.37 [IQR 0.06-0.55] vs 0.18 [IQR 0-0.42] and median balanced accuracy 0.67 [IQR 0.53-0.75] vs 0.56 [IQR 0.50-0.67], p < 0.001 for both). Underestimation of follow-up infarct by CTP is substantial and the follow-up infarct can partially be detected by baseline NCCT, especially in patients with stroke with delayed presentation. Combining rNCCT>5% and CTP increases the accuracy for predicting the follow-up infarct.

Moyamoya Across the Lifespan: Current Neurologic Care and Future Directions.

Moyamoya arteriopathy is an important cause of stroke across the lifespan, with high rates of incident and recurrent stroke in affected individuals. Although it affects adults and children globally, moyamoya is more prevalent in East Asian countries, particularly Japan and Korea. The R4810K variant of the RNF213 gene, most common in Asian populations, is associated with severe, early onset, multisystem vasculopathy. Neuroimaging is critical for moyamoya diagnosis and treatment planning, with conventional imaging, catheter angiography, perfusion imaging, and cerebrovascular reactivity assessment all having a place within moyamoya care. Medical management of moyamoya entails reducing the competing risks of ischemic and hemorrhagic stroke as well as managing coexisting conditions, such as headache, epilepsy, and neuropsychological sequelae. Antiplatelet therapy is commonly prescribed to prevent thromboembolic stroke, although data supporting this practice are limited and practice patterns vary globally. Promoting cerebral oxygen and nutrient delivery with sufficient fluid intake, maintaining adequate blood pressure, and avoiding anemia and hypoglycemia aid in stroke prevention in moyamoya. Definitive treatment of moyamoya is predicated on surgical revascularization, which aims to augment perfusion to at-risk brain tissue and decrease the risk of hemorrhage from fragile moyamoya collaterals. Although surgery is highly effective in appropriately selected patients, perioperative ischemic events occur following 4%-18% of cases. Perioperative medical management aims to mitigate this risk by optimizing brain oxygen delivery through adequate cerebral perfusion and blood oxygenation, pain/nausea control, minimizing metabolic demand, and preventing thrombosis. Long-term neuroimaging surveillance, evaluation of the neuropsychological effect of moyamoya, and screening for and management of headache and epilepsy resulting from moyamoya are important aspects of the chronic care of all patients with moyamoya. In this review, we summarize key aspects of neurologic evaluation and management for moyamoya across the lifespan, highlight key differences between adult and pediatric moyamoya, and discuss ongoing research efforts that aim to improve care of children and adults with moyamoya.

Computed Tomography Perfusion Imaging Profiles Are Similar Before and After Transfer to a Comprehensive Stroke Center (P11-13.003)

Computed Tomography Perfusion Imaging Profiles Are Similar Before and After Transfer to a Comprehensive Stroke Center (P11-13.003)

Diagnostic Utility of Computed Tomography Perfusion in Acute Ischemic Stroke (P9-14.012)

Diagnostic Utility of Computed Tomography Perfusion in Acute Ischemic Stroke (P9-14.012)

Quality Assessment of CT Perfusion Scan Use in Acute Stroke Protocols (P9-14.013)

Quality Assessment of CT Perfusion Scan Use in Acute Stroke Protocols (P9-14.013)