Improved detection and characterization of arterial occlusion in acute ischemic stroke using contrast enhanced MRA

Deep Learning-Based High-Resolution Magnetic Resonance Angiography (MRA) Generation Model for 4D Time-Resolved Angiography with Interleaved Stochastic Trajectories (TWIST) MRA in Fast Stroke Imaging

PURPOSE

The purpose of this study is to improve the qualitative and quantitative image quality of the time-resolved angiography with interleaved stochastic trajectories technique (4D-TWIST-MRA) using deep neural network (DNN)-based MR image reconstruction software.

MATERIALS AND METHODS

A total of 520 consecutive patients underwent 4D-TWIST-MRA for ischemic stroke or intracranial vessel stenosis evaluation. Four-dimensional DNN-reconstructed MRA (4D-DNR) was generated using commercially available software (SwiftMR v.3.0.0.0, AIRS Medical, Seoul, Republic of Korea). Among those evaluated, 397 (76.3%) patients received concurrent time-of-flight MRA (TOF-MRA) to compare the signal-to-noise ratio (SNR), image quality, noise, sharpness, vascular conspicuity, and degree of venous contamination with a 5-point Likert scale. Two radiologists independently evaluated the detection rate of intracranial aneurysm in TOF-MRA, 4D-TWIST-MRA, and 4D-DNR in separate sessions. The other 123 (23.7%) patients received 4D-TWIST-MRA due to a suspicion of acute ischemic stroke. The confidence level and decision time for large vessel occlusion were evaluated in these patients.

RESULTS

In qualitative analysis, 4D-DNR demonstrated better overall image quality, sharpness, vascular conspicuity, and noise reduction compared to 4D-TWIST-MRA. Moreover, 4D-DNR exhibited a higher SNR than 4D-TWIST-MRA. The venous contamination and aneurysm detection rates were not significantly different between the two MRA images. When compared to TOF-MRA, 4D-CE-MRA underestimated the aneurysm size (2.66 ± 0.51 vs. 1.75 ± 0.62, p = 0.029); however, 4D-DNR showed no significant difference in size compared to TOF-MRA (2.66 ± 0.51 vs. 2.10 ± 0.41, p = 0.327). In the diagnosis of large vessel occlusion, 4D-DNR showed a better confidence level and shorter decision time than 4D-TWIST-MRA.

CONCLUSION

DNN reconstruction may improve the qualitative and quantitative image quality of 4D-TWIST-MRA, and also enhance diagnostic performance for intracranial aneurysm and large vessel occlusion.

A novel nomogram predicting early neurological deterioration after intravenous thrombolysis for acute ischemic stroke

Objectives

Intravenous thrombolysis therapy (IVT) with recombinant tissue plasminogen activator has proven to be a beneficial treatment for acute ischemic stroke (AIS) patients when administered within 4.5 h after a stroke. This study aimed to investigate an available and inexpensive predictive tool for early neurological deterioration in AIS.

Methods

Patients admitted to our department with acute stroke who were given IVT with recombinant tissue plasminogen activator within 4.5 h of stroke onset were included in the study. The NIH stroke scale (NIHSS) was used to assess patients' neurological state prior to IVT and for 24 h after. Early neurological deterioration was defined as occurring if the NIHSS total score increased by ≥ 4 or the NIHSS individual score increased by ≥ 2 compared to baseline. Patients were randomly assigned to training or validation cohorts.

Results

Of the 266 AIS patients receiving IVT who were screened, 217 were deemed eligible for the study. Multivariate logistic regression analysis identified smoking history, NIHSS score, homocysteine level, and neutrophil to lymphocyte ratio as independent factors for predicting early neurological deterioration. ROC analysis was used to assess the quality of the resulting nomogram. The AUC for the training dataset was 0.826 (95 % CI, 0.719-0.932), and for the validation dataset was 0.887 (95 % CI, 0.763-1.000).

Conclusion

The robustness of this nomogram suggests that it may be a reliable tool for evaluating the progression of AIS after IVT.

MRI for collateral assessment pre-thrombectomy and association with outcome: a systematic review and meta-analysis

PURPOSE

Various neuroimaging methods exist to assess the collateral circulation in stroke patients but much of the evidence is based on computed tomography. Our aim was to review the evidence for using magnetic resonance imaging for collateral status evaluation pre-thrombectomy and assess the impact of these methods on functional independence.

METHODS

We systematically reviewed EMBASE and MEDLINE for studies that evaluated baseline collaterals using MRI pre-thrombectomy and conducted a meta-analysis to express the relationship between good collaterals (defined variably as the presence [good] vs absence [poor] or quality [ordinal scores binarized as good-moderate vs poor] of collaterals) and functional independence (modified Rankin score mRS≤2) at 90 days. Outcome data were presented as relative risk (RR, 95% confidence interval, 95%CI). We assessed for study heterogeneity, publication bias, and conducted subgroup analyses of different MRI methods and affected arterial territories.

RESULTS

From 497 studies identified, we included 24 (1957 patients) for the qualitative synthesis, and 6 (479 patients) for the metanalysis. Good pre-thrombectomy collaterals were significantly associated with favorable outcome at 90 days (RR=1.91, 95%CI=1.36-2.68], p= 0.0002) with no difference between MRI methods and affected arterial territory subgroups. There was no evidence of statistical heterogeneity (I2=25%) among studies but there was evidence of publication bias.

CONCLUSION

In stroke patients treated with thrombectomy, good pre-treatment collaterals assessed using MRI are associated with double the rate of functional independence. However, we found evidence that relevant MR methods are heterogenous and under-reported. Greater standardization and clinical validation of MRI for collateral evaluation pre-thrombectomy are required.

Acute Ischemic Stroke in Pregnancy : A Practical Focus on Neuroimaging and Reperfusion Therapy

INTRODUCTION

Pregnancy increases the risk of acute ischemic stroke (AIS) among young women and is responsible for about 5% of maternal deaths and significant disability. Concerns of potential adverse events of imaging and reperfusion therapies in this group of patients can lead to a substantial delay or omission of treatment that can significantly worsen outcomes.

OBJECTIVE

The objective of this study is to discuss main concerns of diagnosis and therapy of pregnant patients with AIS regarding neuroimaging and reperfusion treatment.

RESULTS

The cumulative radiation dose of computed tomography (CT)-based entire diagnostic procedure (noncontrast CT, CT-angiography and CT-perfusion) is estimated to be below threshold for serious fetal radiation exposure adverse events. Similarly, magnetic resonance imaging(MRI)-based imaging is thought to be safe as long as gadolinium contrast media are avoided. The added risk of intravenous thrombolysis (IVT) and mechanical thrombectomy during pregnancy is thought to be very low. Nevertheless, some additional safety measures should be utilized to reduce the risk of radiation, contrast media and hypotension exposure during diagnostic procedures or reperfusion treatment.

CONCLUSION

Fetal safety concerns should not preclude routine diagnostic work-up (except for gadolinium contrast media administration) in childbearing AIS women, including procedures applied in unknown onset and late onset individuals. Due to rather low added risk of serious treatment complications, pregnancy should not be a sole contraindication for neither IVT, nor endovascular treatment.

Detection, Diagnosis and Treatment of Acute Ischemic Stroke: Current and Future Perspectives

Stroke is one of the leading causes of disability worldwide. Early diagnosis and treatment of stroke are important for better clinical outcome. Rapid and accurate diagnosis of stroke subtypes is critical. This review discusses the advantages and disadvantages of the current diagnostic and assessment techniques used in clinical practice, particularly for diagnosing acute ischemic stroke. Alternative techniques for rapid detection of stroke utilizing blood based biomarkers and novel portable devices employing imaging methods such as volumetric impedance phase-shift spectroscopy, microwave tomography and Doppler ultrasound are also discussed. Current therapeutic approaches for treating acute ischemic stroke using thrombolytic drugs and endovascular thrombectomy are discussed, with a focus on devices and approaches recently developed to treat large cranial vessel occlusions.

Diagnosis of Ischemic Stroke: As Simple as Possible

The absolute majority of strokes in high-income countries, roughly 91%, are of ischemic origin. This review is focused on acute ischemic stroke (AIS) with large vessel occlusion (LVO) in the anterior circulation, which is considered the most devastating subtype of AIS. Moreover, stroke survivors impose substantial direct and indirect costs of care as well as costs due to productivity loss. We review of diagnostic possibilities of individual imaging methods such as computed tomography and magnetic resonance imaging, and discuss their pros and cons in the imaging of AIS. The goals of non-invasive imaging in AIS are as follows: (a) to rule out intracranial hemorrhage and to quickly exclude hemorrhagic stroke and contraindications for intravenous thrombolysis; (b) to identify potential LVO and its localization and to quickly provide guidance for endovascular treatment; (c) to assess/estimate the volume or size of the ischemic core. We suggest fast diagnostic management, which is able to quickly satisfy the above-mentioned diagnostic goals in AIS with LVO.

Mapping research strands of ethics of artificial intelligence in healthcare: A bibliometric and content analysis

The growth of artificial intelligence in promoting healthcare is rapidly progressing. Notwithstanding its promising nature, however, AI in healthcare embodies certain ethical challenges as well. This research aims to delineate the most influential elements of scientific research on AI ethics in healthcare by conducting bibliometric, social network analysis, and cluster-based content analysis of scientific articles. Not only did the bibliometric analysis identify the most influential authors, countries, institutions, sources, and documents, but it also recognized four ethical concerns associated with 12 medical issues. These ethical categories are composed of normative, meta-ethics, epistemological and medical practice. The content analysis complemented this list of ethical categories and distinguished seven more ethical categories: ethics of relationships, medico-legal concerns, ethics of robots, ethics of ambient intelligence, patients' rights, physicians' rights, and ethics of predictive analytics. This analysis likewise identified 40 general research gaps in the literature and plausible future research strands. This analysis furthers conversations on the ethics of AI and associated emerging technologies such as nanotech and biotech in healthcare, hence, advances convergence research on the ethics of AI in healthcare. Practically, this research will provide a map for policymakers and AI engineers and scientists on what dimensions of AI-based medical interventions require stricter policies and guidelines and robust ethical design and development.

Ischemic Stroke Increased Gadolinium Deposition in the Brain and Aggravated Astrocyte Injury After Gadolinium-Based Contrast Agent Administration: Linear Versus Macrocyclic Agents

BACKGROUND

Gadolinium (Gd)-based contrast agents (GBCAs) have been widely used in MRI. However, several studies have reported Gd deposition in the brain, which has raised concerns about safety.

PURPOSE

To investigate the effects of ischemic stroke on Gd deposition in the brain after repeated administration of linear or macrocyclic GBCAs and to determine whether GBCAs aggravate astrocyte injury after stroke.

STUDY TYPE

Animal study.

ANIMAL MODEL

Twenty-seven male Sprague-Dawley rats were randomized to an exposure group (n = 24) and a healthy control group (n = 3). Half of the exposure group (n = 12) underwent transient middle cerebral artery occlusion (tMCAO) and half (n = 12) had a sham procedure. In each subgroup (tMCAO or sham), the rats had repeated gadopentetate (n = 6) or gadobutrol (n = 6) injections. Oxygen-glucose deprivation and reoxygenation (OGD/R) was used as an in vitro model of stroke.

ASSESSMENT

On day 3 and day 28 after the last injection (p.i.), the Gd concentration in the cerebrum was quantified by inductively coupled plasma mass spectrometry. Cell viability, reactive oxygen species (ROS), and mitochondrial membrane potential (MMP) were analyzed in vitro.

STATISTICAL TESTS

One-way analysis of variance and two-sample t-tests were performed.

RESULTS

The Gd concentration in the ipsilateral hemisphere homogenates of tMCAO group was significantly higher than that in the brain homogenates of the sham group on day 3 p.i. of either gadobutrol (0.065 ± 0.006 vs. 0.042 ± 0.007 μg/g, P < 0.05) or gadopentetate (0.093 ± 0.010 vs. 0.069 ± 0.008 μg/g, P < 0.05). Increased Gd deposition was also found in the ipsilateral hemisphere homogenates of the tMCAO group compared with the brain homogenates of the sham group on day 28 p.i. of gadopentetate (0.075 ± 0.012 vs. 0.044 ± 0.003 μg/g, P < 0.05), but not gadobutrol (0.012 ± 0.007 vs. 0.010 ± 0.001 μg/g, P = 0.80). The Gd concentration in the ipsilateral hemisphere in the tMCAO group was significantly higher for gadopentetate than gadobutrol on both day 3 p.i. (0.085 ± 0.006 vs. 0.049 ± 0.005 μg/g, P < 0.05) and day 28 p.i (0.075 ± 0.012 vs. 0.012 ± 0.007 μg/g, P < 0.05). Additionally, compared with gadobutrol, gadopentetate decreased viability, increased ROS accumulation, and decreased MMP in OGD/R-induced astrocytes (all P < 0.05).

DATA CONCLUSION

Administration of GBCAs after an animal model of ischemic stroke increased Gd deposition in the brain and aggravated astrocyte injury. The effect of gadopentetate appeared to be more pronounced than that of gadobutrol.

Diagnostic value of alternative techniques to gadolinium-based contrast agents in MR neuroimaging-a comprehensive overview

Gadolinium-based contrast agents (GBCAs) increase lesion detection and improve disease characterization for many cerebral pathologies investigated with MRI. These agents, introduced in the late 1980s, are in wide use today. However, some non-ionic linear GBCAs have been associated with the development of nephrogenic systemic fibrosis in patients with kidney failure. Gadolinium deposition has also been found in deep brain structures, although it is of unclear clinical relevance. Hence, new guidelines from the International Society for Magnetic Resonance in Medicine advocate cautious use of GBCA in clinical and research practice. Some linear GBCAs were restricted from use by the European Medicines Agency (EMA) in 2017.

This review focuses on non-contrast-enhanced MRI techniques that can serve as alternatives for the use of GBCAs. Clinical studies on the diagnostic performance of non-contrast-enhanced as well as contrast-enhanced MRI methods, both well established and newly proposed, were included. Advantages and disadvantages together with the diagnostic performance of each method are detailed. Non-contrast-enhanced MRIs discussed in this review are arterial spin labeling (ASL), time of flight (TOF), phase contrast (PC), diffusion-weighted imaging (DWI), magnetic resonance spectroscopy (MRS), susceptibility weighted imaging (SWI), and amide proton transfer (APT) imaging.

Ten common diseases were identified for which studies reported comparisons of non-contrast-enhanced and contrast-enhanced MRI. These specific diseases include primary brain tumors, metastases, abscess, multiple sclerosis, and vascular conditions such as aneurysm, arteriovenous malformation, arteriovenous fistula, intracranial carotid artery occlusive disease, hemorrhagic, and ischemic stroke.

In general, non-contrast-enhanced techniques showed comparable diagnostic performance to contrast-enhanced MRI for specific diagnostic questions. However, some diagnoses still require contrast-enhanced imaging for a complete examination.

High-resolution MRI of intracranial large artery diseases: how to use it in clinical practice?

High-resolution MRI (HRMRI) has emerged as a useful tool for clinical research in recent years. Compared with traditional cranial and vessel imaging, HRMRI provides more additional valuable pathophysiology information that is helpful for the differential diagnosis of intracranial atherosclerosis, dissection and vasculitis. However, there are some points that a neurologist should keep in mind. First, although enhanced vessel wall imaging is widely applied for research purposes, it is not appropriate for routine clinical use. Any injury or inflammation within vessel wall can result in enhancement, which is unspecific for a diagnosis. Second, although plaque components identified on HRMRI arouse researchers' interest, they may have limited positive predictive value for future stroke. Ruptured plaques may have higher prevalence in asymptomatic patients than expected. More prospective observational studies are required. Third, the vessel wall morphology features remain the useful and reliable clue for a diagnosis. It is true that eccentric vessel wall lesions most likely represent atherosclerosis if vessel dissection is easily excluded. For concentric wall lesions, however, the underlying pathophysiology is complicated, either atherosclerotic or non-atherosclerotic. Fourth, HRMRI can show luminal thrombus directly and provide valuable details. All in all, when HRMRI is used by a neurologist, it should not be viewed as the only key for a diagnosis. The diagnosis should be made based on patient history, lab works, other imaging technique and even genetic examinations.