International Union of Angiology (IUA) consensus paper on imaging strategies in atherosclerotic carotid artery imaging: From basic strategies to advanced approaches

Cardiovascular disease (CVD) is the leading cause of mortality and disability in developed countries. According to WHO, an estimated 17.9 million people died from CVDs in 2019, representing 32% of all global deaths. Of these deaths, 85% were due to major adverse cardiac and cerebral events. Early detection and care for individuals at high risk could save lives, alleviate suffering, and diminish economic burden associated with these diseases. Carotid artery disease is not only a well-established risk factor for ischemic stroke, contributing to 10%–20% of strokes or transient ischemic attacks (TIAs), but it is also a surrogate marker of generalized atherosclerosis and a predictor of cardiovascular events. In addition to diligent history, physical examination, and laboratory detection of metabolic abnormalities leading to vascular changes, imaging of carotid arteries adds very important information in assessing stroke and overall cardiovascular risk. Spanning from carotid intima-media thickness (IMT) measurements in arteriopathy to plaque burden, morphology and biology in more advanced disease, imaging of carotid arteries could help not only in stroke prevention but also in ameliorating cardiovascular events in other territories (e.g. in the coronary arteries). While ultrasound is the most widely available and affordable imaging methods, computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), their combination and other more sophisticated methods have introduced novel concepts in detection of carotid plaque characteristics and risk assessment of stroke and other cardiovascular events. However, in addition to robust progress in usage of these methods, all of them have limitations which should be taken into account. The main purpose of this consensus document is to discuss pros but also cons in clinical, epidemiological and research use of all these techniques

Dual-energy imaging in stroke : feasibility of dual-layer detector cone-beam computed tomography

Background: Dual-energy computed tomography (DECT) is increasingly available and used in the standard diagnostic setting of ischemic stroke patients. For stroke patients with suspected large vessel occlusion, cone-beam computed tomography (CBCT) in the interventional suite could be an alternative to CT to shorten door to thrombectomy time. This approach could potentially lead to an improved patient outcome. However, image quality in CBCT is typically limited by artifacts and poor differentiation between gray and white matter. A dual-layer detector CBCT (DL-CBCT) system could be used to separate photon energy spectra with the potential to increase visibility of clinically relevant features, and acquire additional information. Purpose: Paper I evaluated how a range of DECT virtual monoenergetic images (VMI) impact identification of early ischemic changes, compared to conventional polyenergetic CT images. Paper II characterized the performance of a novel DLCBCT system with regards to clinically relevant imaging features. Paper III & IV investigated if DL-CBCT VMIs are sufficient for stroke diagnosis in the interventional suite, compared to reference standard CT. Methods: Paper I was a retrospective single-center study including consecutive patients presenting with acute ischemic stroke caused by an occlusion of the intracranial internal carotid artery or proximal middle cerebral artery. Automated Alberta Stroke Program Early Computed Tomography Score (ASPECTS) results from conventional images and 40-120 keV VMI were generated and compared to reference standard CT ASPECTS. In paper II, a prototype dual-layer detector was fitted into a commercial interventional C-arm CBCT system to enable dual-energy acquisitions. Metrics for spatial resolution, noise and uniformity were gathered. Clinically relevant tissue and iodine substitutes were characterized in terms of effective atomic numbers and electron densities. Iodine quantification was performed and virtual non-contrast (VNC) images were evaluated. VMIs were reconstructed and used for CT number estimation and evaluation of contrast-to-noise ratios (CNR) in relevant tissue pairings. In paper III and IV, a prospective single-center study enrolled consecutive participants with ischemic or hemorrhagic stroke on CT. In paper III, hemorrhage detection accuracy, ASPECTS accuracy, subjective and objective image quality were evaluated on non-contrast DL-CBCT 75 keV VMI and compared to reference standard CT. In paper IV, intracranial arterial segment vessel visibility and artifacts were evaluated on intravenous DL-CBCT angiography (DL-CBCTA) 70 keV VMI and compared to CT angiography (CTA). In both paper III and IV, non-inferiority was determined by the exact binomial test with a one-sided lower performance boundary set to 80% (98.75% CI). Main results: In paper I, 24 patients were included. 70 keV VMI had the highest region-based ASPECTS accuracy (0.90), sensitivity (0.82) and negative predictive value (0.94), whereas 40 keV VMI had the lowest accuracy (0.77), sensitivity (0.34) and negative predictive value (0.80). In paper II, the prototype and commercial CBCT had a similar spatial resolution and noise using the same standard reconstruction. For all tissue substitutes, the mean accuracy in effective atomic number was 98.2% (SD 1.2%) and 100.3% (SD 0.9%) for electron density. Iodine quantification had a mean difference of -0.1 (SD 0.5) mg/ml compared to the true concentrations. For VNC images, iodine substitutes with blood averaged 43.2 HU, blood only 44.8 HU, iodine substitutes with water 2.6 HU. A noise-suppressed dataset showed a CNR peak at 40 keV VMI and low at 120 keV VMI. In the same dataset without noise suppression, peak CNR was seen at 70 keV VMI and a low at 120 keV VMI. CT numbers of various clinically relevant objects generally matched the calculated CT number in a wide range of VMIs. In paper III, 27 participants were included. One reader missed a small bleeding, however all hemorrhages were detected in the majority analysis (100% accuracy, CI lower boundary 86%, p=0.002). ASPECTS majority analysis had 90% accuracy (CI lower boundary 85%, p<0.001), sensitivity was 66% (individual readers 67%, 69% and 76%), specificity was 97% (97%, 96% and 89%). Subjective and objective image quality metrics were inferior to CT. In paper IV, 21 participants had matched image sets. After excluding examinations with scan issues, all readers considered DL-CBCTA non-inferior to CTA (CI boundary 93%, 84%, 80%, respectively), when assessing arteries relevant in candidates for intracranial thrombectomy. Artifacts were more prevalent compared to CTA. Conclusions: In paper I, automated 70 keV VMI ASPECTS had the highest diagnostic accuracy, sensitivity and negative predictive value overall. Different VMI energy levels impact the identification of early ischemic changes on DECT. In paper II, the DL-CBCT prototype system showed comparable technical metrics to a commercial CBCT system, while offering dual-energy capability. The dual-energy images indicated a consistent ability to separate and characterize clinically relevant tissues, blood and iodine. Thus, the DL-CBCT system could find utility in the diagnostic setting. In paper III, non-contrast DL-CBCT 75 keV VMI showed non-inferior hemorrhage detection and ASPECTS accuracy to CT. However, image quality was inferior compared to CT, and visualization of small subarachnoid hemorrhages after treatment remains a challenge. In the same stroke cohort, paper IV showed non-inferior vessel visibility for DL-CBCTA 70 keV VMI compared to CTA under certain conditions. Specifically, the prototype system had a long scan time and was not capable of bolus tracking which resulted in scan issues. After excluding participants with such issues, DL-CBCTA 70 keV VMI were found non-inferior to CTA. In summary, the findings of this thesis indicate that DL-CBCT may be sufficient for stroke assessment in the interventional suite with the potential to bypass CT in patients eligible for thrombectomy. However, issues related to the prototype system and the visualization of small hemorrhages highlight the need of further development

Artificial Intelligence: Development and Applications in Neurosurgery

The last decade has witnessed a significant increase in the relevance of artificial intelligence (AI) in neuroscience. Gaining notoriety from its potential to revolutionize medical decision making, data analytics, and clinical workflows, AI is poised to be increasingly implemented into neurosurgical practice. However, certain considerations pose significant challenges to its immediate and widespread implementation. Hence, this chapter will explore current developments in AI as it pertains to the field of clinical neuroscience, with a primary focus on neurosurgery. Additionally included is a brief discussion of important economic and ethical considerations related to the feasibility and implementation of AI-based technologies in neurosciences, including future horizons such as the operational integrations of human and non-human capabilities

Computer aided assessment of CT scans of traumatic brain injury patients

A thesis submitted in partial fulfilment for the degree of Doctor of PhilosophyOne of the serious public health problems is the Traumatic Brain Injury, also known as silent epidemic, affecting millions every year. Management of these patients essentially involves neuroimaging and noncontrast CT scans are the first choice amongst doctors. Significant anatomical changes identified on the neuroimages and volumetric assessment of haemorrhages and haematomas are of critical importance for assessing the patients’ condition for targeted therapeutic and/or surgical interventions. Manual demarcation and annotation by experts is still considered gold standard, however, the interpretation of neuroimages is fraught with inter-observer variability and is considered ’Achilles heel’ amongst radiologists. Errors and variability can be attributed to factors such as poor perception, inaccurate deduction, incomplete knowledge or the quality of the image and only a third of doctors confidently report the findings. The applicability of computer aided dianosis in segmenting the apposite regions and giving ’second opinion’ has been positively appraised to assist the radiologists, however, results of the approaches vary due to parameters of algorithms and manual intervention required from doctors and this presents a gap for automated segmentation and estimation of measurements of noncontrast brain CT scans. The Pattern Driven, Content Aware Active Contours (PDCAAC) Framework developed in this thesis provides robust and efficient segmentation of significant anatomical landmarks, estimations of their sizes and correlation to CT rating to assist the radiologists in establishing the diagnosis and prognosis more confidently. The integration of clinical profile of the patient into image segmentation algorithms has significantly improved their performance by highlighting characteristics of the region of interest. The modified active contour method in the PDCAAC framework achieves Jaccard Similarity Index (JI) of 0.87, which is a significant improvement over the existing methods of active contours achieving JI of 0.807 with Simple Linear Iterative Clustering and Distance Regularized Level Set Evolution. The Intraclass Correlation Coefficient of intracranial measurements is >0.97 compared with radiologists. Automatic seeding of the initial seed curve within the region of interest is incorporated into the method which is a novel approach and alleviates limitation of existing methods. The proposed PDCAAC framework can be construed as a contribution towards research to formulate correlations between image features and clinical variables encompassing normal development, ageing, pathological and traumatic cases propitious to improve management of such patients. Establishing prognosis usually entails survival but the focus can also be extended to functional outcomes, residual disability and quality of life issues

CT Scanning

Since its introduction in 1972, X-ray computed tomography (CT) has evolved into an essential diagnostic imaging tool for a continually increasing variety of clinical applications. The goal of this book was not simply to summarize currently available CT imaging techniques but also to provide clinical perspectives, advances in hybrid technologies, new applications other than medicine and an outlook on future developments. Major experts in this growing field contributed to this book, which is geared to radiologists, orthopedic surgeons, engineers, and clinical and basic researchers. We believe that CT scanning is an effective and essential tools in treatment planning, basic understanding of physiology, and and tackling the ever-increasing challenge of diagnosis in our society

Cerebral Circulation

Diagnostics and diseases related to the cerebrovascular system are constantly evolving and updating. 3D augmented reality or quantification of cerebral perfusion are becoming important diagnostic tools in daily practice and the role of the cerebral venous system is being constantly revised considering new theories such as that of “the glymphatic system.” This book provides updates on models, diagnosis, and treatment of diseases of the cerebrovascular system

Characterization of alar ligament on 3.0T MRI: a cross-sectional study in IIUM Medical Centre, Kuantan

INTRODUCTION: The main purpose of the study is to compare the normal anatomy of alar ligament on MRI between male and female. The specific objectives are to assess the prevalence of alar ligament visualized on MRI, to describe its characteristics in term of its course, shape and signal homogeneity and to find differences in alar ligament signal intensity between male and female. This study also aims to determine the association between the heights of respondents with alar ligament signal intensity and dimensions. MATERIALS & METHODS: 50 healthy volunteers were studied on 3.0T MR scanner Siemens Magnetom Spectra using 2-mm proton density, T2 and fat-suppression sequences. Alar ligament is depicted in 3 planes and the visualization and variability of the ligament courses, shapes and signal intensity characteristics were determined. The alar ligament dimensions were also measured. RESULTS: Alar ligament was best depicted in coronal plane, followed by sagittal and axial planes. The orientations were laterally ascending in most of the subjects (60%), predominantly oval in shaped (54%) and 67% showed inhomogenous signal. No significant difference of alar ligament signal intensity between male and female respondents. No significant association was found between the heights of the respondents with alar ligament signal intensity and dimensions. CONCLUSION: Employing a 3.0T MR scanner, the alar ligament is best portrayed on coronal plane, followed by sagittal and axial planes. However, tremendous variability of alar ligament as depicted in our data shows that caution needs to be exercised when evaluating alar ligament, especially during circumstances of injury

Case series of breast fillers and how things may go wrong: radiology point of view

INTRODUCTION: Breast augmentation is a procedure opted by women to overcome sagging breast due to breastfeeding or aging as well as small breast size. Recent years have shown the emergence of a variety of injectable materials on market as breast fillers. These injectable breast fillers have swiftly gained popularity among women, considering the minimal invasiveness of the procedure, nullifying the need for terrifying surgery. Little do they know that the procedure may pose detrimental complications, while visualization of breast parenchyma infiltrated by these fillers is also deemed substandard; posing diagnostic challenges. We present a case series of three patients with prior history of hyaluronic acid and collagen breast injections. REPORT: The first patient is a 37-year-old lady who presented to casualty with worsening shortness of breath, non-productive cough, central chest pain; associated with fever and chills for 2-weeks duration. The second patient is a 34-year-old lady who complained of cough, fever and haemoptysis; associated with shortness of breath for 1-week duration. CT in these cases revealed non thrombotic wedge-shaped peripheral air-space densities. The third patient is a 37‐year‐old female with right breast pain, swelling and redness for 2- weeks duration. Previous collagen breast injection performed 1 year ago had impeded sonographic visualization of the breast parenchyma. MRI breasts showed multiple non- enhancing round and oval shaped lesions exhibiting fat intensity. CONCLUSION: Radiologists should be familiar with the potential risks and hazards as well as limitations of imaging posed by breast fillers such that MRI is required as problem-solving tool

Computed-Tomography (CT) Scan

A computed tomography (CT) scan uses X-rays and a computer to create detailed images of the inside of the body. CT scanners measure, versus different angles, X-ray attenuations when passing through different tissues inside the body through rotation of both X-ray tube and a row of X-ray detectors placed in the gantry. These measurements are then processed using computer algorithms to reconstruct tomographic (cross-sectional) images. CT can produce detailed images of many structures inside the body, including the internal organs, blood vessels, and bones. This book presents a comprehensive overview of CT scanning. Chapters address such topics as instrumental basics, CT imaging in coronavirus, radiation and risk assessment in chest imaging, positron emission tomography (PET), and feature extraction