Understanding Bias in Artificial Intelligence: A Practice Perspective.

In the fall of 2021, several experts in this space delivered a Webinar hosted by the American Society of Neuroradiology (ASNR) Diversity and Inclusion Committee, focused on expanding the understanding of bias in artificial intelligence, with a health equity lens, and provided key concepts for neuroradiologists to approach the evaluation of these tools. In this perspective, we distill key parts of this discussion, including understanding why this topic is important to neuroradiologists and lending insight on how neuroradiologists can develop a framework to assess health equity-related bias in artificial intelligence tools. In addition, we provide examples of clinical workflow implementation of these tools so that we can begin to see how artificial intelligence tools will impact discourse on equitable radiologic care. As continuous learners, we must be engaged in new and rapidly evolving technologies that emerge in our field. The Diversity and Inclusion Committee of the ASNR has addressed this subject matter through its programming content revolving around health equity in neuroradiologic advances.

Brief communication: RSNA female gold medal recipients: life, legacy, and intergenerational mentorship.

In recent years, the number of RSNA female gold medal recipients has increased. Also recently, the importance of diversity, equity, and inclusion (DEI) in radiology beyond gender has received greater attention. The ACR Pipeline Initiative for the Enrichment of Radiology (PIER) program "began through the Commission for Women and Diversity in hopes of giving underrepresented minorities (URMs) and women an opportunity to explore the radiology specialty and engage in research."1 Consistent with this mission and the mission of Clinical Imaging to "advance knowledge and positively impact patient care and the profession of radiology,"2 the journal is pleased to announce a forthcoming initiative in which PIER program medical students will be paired with senior faculty members and given the opportunity to write a first-authorship publication about the legacies of RSNA Female Gold Medal Recipients. With this form of intergenerational mentorship, scholars will gain a new perspective and guidance as they navigate their early career.

Identifying clinically applicable machine learning algorithms for glioma segmentation: recent advances and discoveries.

Background: While there are innumerable machine learning (ML) research algorithms used for segmentation of gliomas, there is yet to be a US FDA cleared product. The aim of this study is to explore the systemic limitations of research algorithms that have prevented translation from concept to product by a review of the current research literature. Methods: We performed a systematic literature review on 4 databases. Of 11 727 articles, 58 articles met the inclusion criteria and were used for data extraction and screening using TRIPOD. Results: We found that while many articles were published on ML-based glioma segmentation and report high accuracy results, there were substantial limitations in the methods and results portions of the papers that result in difficulty reproducing the methods and translation into clinical practice. Conclusions: In addition, we identified that more than a third of the articles used the same publicly available BRaTS and TCIA datasets and are responsible for the majority of patient data on which ML algorithms were trained, which leads to limited generalizability and potential for overfitting and bias.

Development of paravertebral pseudoaneurysms following vertebral augmentation: a report of two cases.

Paravertebral pseudoaneurysms are infrequent following vertebral augmentation but can be difficult to manage due to their proximity to the arterial supply of the spinal cord. Here, we present two distinct manifestations of this complication with associated anatomy and management. In the first, a pseudoaneurysm developed following radiofrequency ablation and kyphoplasty at the L2 and L4 levels. Direct puncture embolization initially failed to close the pseudoaneurysm, but stasis was ultimately achieved via trans-arterial embolization. In the second, vertebral augmentation at the T9 and T11-L3 levels was complicated by formation of a pseudoaneurysm fed by a segmental artery and a long paravertebral anastomotic vein. Due to the patient's poor medical status, intervention was not performed. Understanding vertebral arterial anatomy is crucial for preventing and treating vascular injury in vertebral augmentation.

Hippocampal recording via the RNS system reveals marked ipsilateral activation of epileptiform activity during Wada testing.

Wada testing remains an important component of pre-surgical testing to assess the feasibility of temporal lobectomy for patients with intractable epilepsy. In this procedure, an anesthetic is injected into either internal carotid artery while memory and language testing is performed, simulating the effect of temporal lobe resection. The mechanism remains poorly understood because the hippocampal vasculature is predominantly via the posterior circulation. We recorded hippocampal EEG during bilateral methohexital Wada testing in three patients who had previously been implanted with a responsive neurostimulation system (RNS) to determine the effect of the injections on hippocampal activity. In all six injections from three patients, methohexital caused immediate, transient increases in hippocampal spikes. With at least two of these injections, the electrographic changes were consistent with electrographic seizures. In all cases, the epileptiform activity was not apparent on scalp EEG and was without obvious clinical correlate other than the negative findings expected from the anesthetic. The results demonstrate the utility of intracranial EEG during Wada testing and suggest that the elicitation of seizures or continuous spiking might contribute to dysfunction of the hippocampus during the Wada test. We hypothesize that this effect is due to disconnection and disinhibition of medial temporal structures.

Use of artificial intelligence in emergency radiology: An overview of current applications, challenges, and opportunities.

The value of artificial intelligence (AI) in healthcare has become evident, especially in the field of medical imaging. The accelerated pace and acuity of care in the Emergency Department (ED) has made it a popular target for artificial intelligence-driven solutions. Software that helps better detect, report, and appropriately guide management can ensure high quality patient care while enabling emergency radiologists to better meet the demands of quick turnaround times. Beyond diagnostic applications, AI-based algorithms also have the potential to optimize other important steps within the ED imaging workflow. This review will highlight the different types of AI-based applications currently available for use in the ED, as well as the challenges and opportunities associated with their implementation.

Machine Learning Applications for Differentiation of Glioma from Brain Metastasis-A Systematic Review.

Glioma and brain metastasis can be difficult to distinguish on conventional magnetic resonance imaging (MRI) due to the similarity of imaging features in specific clinical circumstances. Multiple studies have investigated the use of machine learning (ML) models for non-invasive differentiation of glioma from brain metastasis. Many of the studies report promising classification results, however, to date, none have been implemented into clinical practice. After a screening of 12,470 studies, we included 29 eligible studies in our systematic review. From each study, we aggregated data on model design, development, and best classifiers, as well as quality of reporting according to the TRIPOD statement. In a subset of eligible studies, we conducted a meta-analysis of the reported AUC. It was found that data predominantly originated from single-center institutions (n = 25/29) and only two studies performed external validation. The median TRIPOD adherence was 0.48, indicating insufficient quality of reporting among surveyed studies. Our findings illustrate that despite promising classification results, reliable model assessment is limited by poor reporting of study design and lack of algorithm validation and generalizability. Therefore, adherence to quality guidelines and validation on outside datasets is critical for the clinical translation of ML for the differentiation of glioma and brain metastasis.

High-Entry Vertebral Artery Variant during Anterior Cervical Discectomy and Fusion.

Anterior surgical approaches to the cervical spine have allowed for treatment of common and complex pathologies with excellent outcomes. During the approach, complications can result from injury to the surrounding structures. The transverse processes usually protect the vertebral artery (VA) as it enters at C6 and courses cranially through the transverse foramina to C2 (referred to as the V2 segment). This is a case report of a patient who presented with myeloradiculopathy attributed to a C4-C5 disc herniation, severe canal stenosis, and marked bilateral neural foraminal stenosis. Preoperative imaging showed the right VA entering the C4 transverse foramen. This anatomic variant on a routine MRI led to further imaging and precautions when performing an uneventful anterior cervical discectomy and fusion (ACDF) at C4-C5. A high VA entry point into the transverse foramen above C6 could increase the risk of iatrogenic vascular injury in anterior approaches to the cervical spine. Rarely reported, the currently presented case describes a patient with a C4 right VA entry variant and highlights the importance of proper surgical planning.

DECT in Detection of Vertebral Fracture-associated Bone Marrow Edema: A Systematic Review and Meta-Analysis with Emphasis on Technical and Imaging Interpretation Parameters.

Background Dual-energy CT (DECT) shows promising performance in detecting bone marrow edema (BME) associated with vertebral body fractures. However, the optimal technical and image interpretation parameters are not well described. Purpose To conduct a systematic review and meta-analysis to determine the diagnostic performance of DECT in detecting BME associated with vertebral fractures (VFs), using different technical and image interpretation parameters, compared with MRI as the reference standard. Materials and Methods A systematic literature search was performed on July 9, 2020, to identify studies evaluating DECT performance for in vivo detection of vertebral BME. A random-effects model was used to derive estimates of the diagnostic accuracy parameters of DECT. The impact of relevant covariates in technical, image interpretation, and study design parameters on the diagnostic performance of DECT was investigated using subgroup analyses. Results Seventeen studies (with 742 of 2468 vertebrae with BME at MRI) met inclusion criteria. Pooled estimates of sensitivity, specificity, and area under the curve of DECT for vertebral body BME were 89% (95% CI: 84%, 92%), 96% (95% CI: 92%, 98%), and 96% (95% CI: 94%, 97%), respectively. Single-source consecutive scanning showed poor specificity (78%) compared with the dual-source technique (98%, P < .001). Specificity was higher using bone and soft-tissue kernels (98%) compared with using only soft-tissue kernels (90%, P = .001). Qualitative assessment had a better specificity (97%) versus quantitative assessment (90%) of DECT images (P = .01). Experienced readers showed considerably higher specificity (96%) compared with trainees (79%, P = .01). DECT sensitivity improved using a higher difference between low- and high-energy spectra (90% vs 83%, P = .04). Conclusion Given its high specificity, the detection of vertebral bone marrow edema with dual-energy CT (DECT) associated with vertebral fracture may obviate confirmatory MRI in an emergency setting. Technical parameters, such as the dual-source technique, both bone and soft-tissue kernels, and qualitative assessment by experienced readers, can ensure the high specificity of DECT. © RSNA, 2021 Online supplemental material is available for this article.

Effects of Collateral Status on Infarct Distribution Following Endovascular Therapy in Large Vessel Occlusion Stroke.

BACKGROUND AND PURPOSE: We aim to examine effects of collateral status and post-thrombectomy reperfusion on final infarct distribution and early functional outcome in patients with anterior circulation large vessel occlusion ischemic stroke. METHODS: Patients with large vessel occlusion who underwent endovascular intervention were included in this study. All patients had baseline computed tomography angiography and follow-up magnetic resonance imaging. Collateral status was graded according to the criteria proposed by Miteff et al and reperfusion was assessed using the modified Thrombolysis in Cerebral Infarction (mTICI) system. We applied a multivariate voxel-wise general linear model to correlate the distribution of final infarction with collateral status and degree of reperfusion. Early favorable outcome was defined as a discharge modified Rankin Scale score ≤2. RESULTS: Of the 283 patients included, 129 (46%) had good, 97 (34%) had moderate, and 57 (20%) had poor collateral status. Successful reperfusion (mTICI 2b/3) was achieved in 206 (73%) patients. Poor collateral status was associated with infarction of middle cerebral artery border zones, whereas worse reperfusion (mTICI scores 0-2a) was associated with infarction of middle cerebral artery territory deep white matter tracts and the posterior limb of the internal capsule. In multivariate regression models, both mTICI (P<0.001) and collateral status (P<0.001) were among independent predictors of final infarct volumes. However, mTICI (P<0.001), but not collateral status (P=0.058), predicted favorable outcome at discharge. CONCLUSIONS: In this cohort of patients with large vessel occlusion stroke, both the collateral status and endovascular reperfusion were strongly associated with middle cerebral artery territory final infarct volumes. Our findings suggesting that baseline collateral status predominantly affected middle cerebral artery border zones infarction, whereas higher mTICI preserved deep white matter and internal capsule from infarction; may explain why reperfusion success-but not collateral status-was among the independent predictors of favorable outcome at discharge. Infarction of the lentiform nuclei was observed regardless of collateral status or reperfusion success.

Multimodality Imaging of Vertebrobasilar Dolichoectasia: Clinical Presentations and Imaging Spectrum.

Vertebrobasilar dolichoectasia (VBD) is characterized by ectasia, elongation, and tortuosity of the vertebrobasilar arteries, with a high degree of variability in clinical presentation. The disease origin is believed to involve degeneration of the internal elastic lamina, thinning of the media secondary to reticular fiber deficiency, and smooth muscle atrophy. The prevalence of VBD is variable, ranging from 0.05% to 18%. Most patients with VBD are asymptomatic and their VBD is detected incidentally; however, it is important to recognize that the presence of symptoms, which can lead to clinically significant morbidity and sometimes mortality, may influence clinical management. The most important clinical presentations of VBD are vascular events, such as ischemic stroke and catastrophic intracranial hemorrhage, or progressive compressive symptoms related to compression of adjacent structures, including the cranial nerves, brainstem, or third ventricle, causing hydrocephalus. The imaging diagnostic criteria for computed tomography and magnetic resonance (MR) imaging include three quantitative measures of basilar artery morphology: laterality score, height of bifurcation, and basilar artery diameter. The authors review the relevant anatomy and disease origin of VBD; pertinent imaging findings, including intraluminal thrombus and relation to the cranial nerves; and imaging pitfalls, such as the hyperintense vessel sign on MR images and artifacts related to slow flow in the dolichoectatic vessel. In addition, clinical manifestations, the role of radiology in diagnosis and management of this condition, and available management options are reviewed. (©)RSNA, 2016.

High-resolution Vessel Wall Magnetic Resonance Imaging in Intracranial Aneurysms and Brain Arteriovenous Malformations.

Over the last several years, the advent of intracranial high-resolution vessel wall magnetic resonance imaging (VW-MRI) has provided a new lens with which to view cerebrovascular disease that has not previously been available with conventional imaging. It has already fundamentally changed the way that steno-occlusive diseases are evaluated at many academic centers. This review focuses on current and emerging applications of intracranial high-resolution VW-MRI in the clinical evaluation of intracranial aneurysms and brain arteriovenous malformations. Examples are provided from our clinical practice.

Practice Building: Achieving Growth Through Computed Tomographic Myelography-Based Stereotactic Body Radiation Therapy for Spinal Metastases.

Stereotactic body radiation therapy (SBRT) is as an effective method to treat spinal metastases. Imaging is a critical component in the workup of patients who undergo stereotactic radiation treatment. Computed tomographic myelography may be more accurate than magnetic resonance imaging in the delineation of neural elements during SBRT. The task we faced was to offer a standardized method to rapidly and safely obtain high-quality computed tomographic myelography as part of a robust spine SBRT program. In detailing our experience, we support the greater, active participation of radiologists in the multidisciplinary care of patients with spinal metastases, while encouraging other radiologists to foster similar collaborations at their own institutions.

Carotid stent extrusion following carotid blowout.

OBJECTIVE: We describe an unusual foreign body, a carotid stent extruded into the upper airway, and discuss the predisposing factors. METHODS: This is a single patient case report with review of the literature. RESULTS: Our patient is a 59 year old female treated for T3N2aM0 (stage IVa) left tonsil squamous cell carcinoma who experienced a carotid blowout treated by carotid stent placement with subsequent carotid coiling and vessel takedown. Approximately ten months later, she coughed and expelled approximately 3cm of tubular stent-appearing material into her airway causing acute stridor and dysphagia. CT angiography (CTA) showed the distal and proximal stent in proper position without evidence of extravasation. The stent was extracted transorally showing the distal end of the carotid to be patent and covered by fibrin within its lumen. Review of the literature shows that such stent extrusions, although rare, do occur. CONCLUSION: Carotid stents are a valuable tool in cases of carotid blowout. However, long-term data on patient prognosis is lacking. The foreign body response triggered by stent placement can cause dislodgement. The potential for stent extrusion is greatest in patients who have preexisting ulceration or who have undergone radiation, both common in head and neck cancer patients.

Homozygous loss of DIAPH1 is a novel cause of microcephaly in humans.

The combination of family-based linkage analysis with high-throughput sequencing is a powerful approach to identifying rare genetic variants that contribute to genetically heterogeneous syndromes. Using parametric multipoint linkage analysis and whole exome sequencing, we have identified a gene responsible for microcephaly (MCP), severe visual impairment, intellectual disability, and short stature through the mapping of a homozygous nonsense alteration in a multiply-affected consanguineous family. This gene, DIAPH1, encodes the mammalian Diaphanous-related formin (mDia1), a member of the diaphanous-related formin family of Rho effector proteins. Upon the activation of GTP-bound Rho, mDia1 generates linear actin filaments in the maintenance of polarity during adhesion, migration, and division in immune cells and neuroepithelial cells, and in driving tangential migration of cortical interneurons in the rodent. Here, we show that patients with a homozygous nonsense DIAPH1 alteration (p.Gln778*) have MCP as well as reduced height and weight. diap1 (mDia1 knockout (KO))-deficient mice have grossly normal body and brain size. However, our histological analysis of diap1 KO mouse coronal brain sections at early and postnatal stages shows unilateral ventricular enlargement, indicating that this mutant mouse shows both important similarities as well as differences with human pathology. We also found that mDia1 protein is expressed in human neuronal precursor cells during mitotic cell division and has a major impact in the regulation of spindle formation and cell division.

Imaging recommendations for acute stroke and transient ischemic attack patients: a joint statement by the American Society of Neuroradiology, the American College of Radiology and the Society of NeuroInterventional Surgery.

In the article entitled "Imaging Recommendations for Acute Stroke and Transient Ischemic Attack Patients: A Joint Statement by the American Society of Neuroradiology, the American College of Radiology and the Society of NeuroInterventional Surgery", we are proposing a simple, pragmatic approach that will allow the reader to develop an optimal imaging algorithm for stroke patients at their institution.

Recessive loss of function of the neuronal ubiquitin hydrolase UCHL1 leads to early-onset progressive neurodegeneration.

Ubiquitin C-terminal hydrolase-L1 (UCHL1), a neuron-specific de-ubiquitinating enzyme, is one of the most abundant proteins in the brain. We describe three siblings from a consanguineous union with a previously unreported early-onset progressive neurodegenerative syndrome featuring childhood onset blindness, cerebellar ataxia, nystagmus, dorsal column dysfuction, and spasticity with upper motor neuron dysfunction. Through homozygosity mapping of the affected individuals followed by whole-exome sequencing of the index case, we identified a previously undescribed homozygous missense mutation within the ubiquitin binding domain of UCHL1 (UCHL1(GLU7ALA)), shared by all affected subjects. As demonstrated by isothermal titration calorimetry, purified UCHL1(GLU7ALA), compared with WT, exhibited at least sevenfold reduced affinity for ubiquitin. In vitro, the mutation led to a near complete loss of UCHL1 hydrolase activity. The GLU7ALA variant is predicted to interfere with the substrate binding by restricting the proper positioning of the substrate for tunneling underneath the cross-over loop spanning the catalytic cleft of UCHL1. This interference with substrate binding, combined with near complete loss of hydrolase activity, resulted in a >100-fold reduction in the efficiency of UCHL1(GLU7ALA) relative to WT. These findings demonstrate a broad requirement of UCHL1 in the maintenance of the nervous system.

Advances in transcranial Doppler US: imaging ahead.

Transcranial Doppler ultrasonography (US) is a noninvasive, portable technique for evaluating the intracranial vasculature. It has found its most useful clinical application in the detection of vasospasm involving the cerebral vessels after subarachnoid hemorrhage due to aneurysm rupture. The technique has become an integral part of monitoring and managing patients with subarachnoid hemorrhage in the neurologic intensive care unit. In addition, it has proved useful for evaluating the intracranial vasculature in patients with sickle cell disease, stroke, or brain death. Transcranial US originated as a "blind" nonimaging study in which pulsed Doppler technology was used. Identification of the major intracranial vessels and evaluation of those vessels for vasospasm relied on spectral waveforms obtained in each vessel and was based on the depth of the vessel from the skull, the direction of blood flow, and the orientation of the transducer. Recent advances in US technology allow the use of gray-scale, spectral Doppler, and color Doppler flow imaging to directly visualize intracranial vessels, thereby simplifying flow velocity measurements and enhancing their accuracy for vasospasm detection. In particular, measurements of peak systolic velocity and mean flow velocity and calculation of the Lindegaard ratio facilitate the identification of vessels that may be in vasospasm and help differentiate vasospasm from physiologic conditions such as hyperemia and autoregulation. Thus, gray-scale and color Doppler flow imaging offer many advantages over the original pulsed Doppler technique for evaluating the intracranial vasculature.

Intracranial stenting as monotherapy in subarachnoid hemorrhage and sickle cell disease.

INTRODUCTION: Although there have been a few reports of coiling intracranial aneurysms in patients with sickle cell disease (SCD), there are no reports of intracranial stent placement in this patient population. A patient in whom stent placement was utilized as monotherapy to treat a blister-like aneurysm is described and the implications of SCD and endovascular treatment are discussed. CASE REPORT: A 37-year-old man with SCD presented with diffuse subarachnoid hemorrhage. Angiography confirmed a 2 mm irregular aneurysm on the posterior cerebral artery which was treated with an oversized Neuroform 3 stent that was placed across the aneurysm neck by the senior author (KRB). Follow-up CT angiography showed no residual aneurysmal filling. The patient was discharged home in a stable condition, and he continues to do well 4 weeks following the procedure with no recurrence of the aneurysm. DISCUSSION: This report reviews hypercoagulability in SCD and the treatment options for intracranial aneurysms in patients with SCD. Additionally, the reported case suggests that intracranial stent placement may be a viable option for treating complex intracranial aneurysms in SCD patients.