Black bone magnetic resonance imaging in clinical practice: Systematic review of current perspectives and insights

Role of MRI in diagnosing vestibulocochlear nerve disorders: A narrative literature review of imaging techniques, current standards, and challenges.

Alzheimer’s disease (AD) is the most common progressive neurodegenerative disorder characterized by gradual deterioration in cognition, function, and behavior. The number of patients with dementia is increasing in the Western world. Neuroimaging plays an important role in the study and clinical diagnosis of AD. It is of utmost importance to exclude potentially treatable conditions such as brain tumors, hematomas, and hydrocephalus. According to a meta-analysis potentially reversible causes were seen in 9% and actually reversed in only 0.6% of dementia cases (0.29% partially, 0.31% fully) (1). Techniques that are widely used in clinical practice are still largely based on structural magnetic resonance (MR) imaging and volumetry. Recently Wattjes et al. (2) concluded that although MR imaging should be the preferred imaging modality due its lack of ionizing radiation and higher contrast resolution, 64-detector row computed tomography (CT) is a suitable and accurate imaging method with which to evaluate global cortical atrophy, medial temporal lobe atrophy, and white matter changes in a memory clinic setting, and it can be considered a nearly equivalent alternative to MR imaging in patients who cannot undergo MR examination. However, it should be noted that measures of brain atrophy typically reflect the relatively late stages of neuronal loss and may not be ideal for identifying early neuropathological changes. There is increasing evidence showing that the pathological process associated with AD may begin years or decades before diagnosis. But: do the advanced techniques help in assessing therapeutic effects or improve patient outcome? Early detection of AD risk would enable preventive or more effective treatment of the patients, resulting in a time delay in symptom onset that may decrease the prevalence of the disease (3). Therefore, in addition to the structural MR imaging procedures a spectrum of novel MR imaging tools is being adopted for the scientific study of pathological processes underlying the development of AD, including blood oxygenation level-dependent (BOLD) functional MRI studies of brain activation and functional connectivity, perfusion measurements with arterial spin labeling (ASL), MR spectroscopy (MRS), and diffusion tensor imaging (DTI). Functional MRI on BOLD contrast allows noninvasive in vivo assessment of hemodynamic responses to external stimuli. ASL is a non-invasive MR imaging technique for the measurement of regional cerebral blood flow by labeling of the arterial water and using it as an endogenous tracer. Although challenging (4), hippocampal MRS combined with quantitative measurements of hippocampal atrophy may improve the early diagnosis of AD. DTI can be used to determine the orientation of fiber tracts and the neural network connections between different brain regions. Fractional anisotropy has become an imaging marker commonly used to study microstructural white matter abnormalities in various pathological states. There is growing interest in using DTI for AD studies (5, 6). In this issue of Acta Radiologica a comprehensive state of the art review by Dr Li Tie-Qiang (3) discusses the use of these advanced imaging techniques mainly in research. The review allows you to get an excellent overview of the advanced MR imaging techniques and the article is highly recommended reading.

Three-dimensional (3D) reconstructed computed tomography (CT) imaging has become an integral component of craniomaxillofacial patient care. However, with increasing concern regarding the use of ionizing radiation, particularly in children with benign conditions who require repeated examinations, dose reduction and nonionizing alternatives are actively being sought. The "Black Bone" magnetic resonance imaging (MRI) technique provides uniform contrast of the soft tissues to enhance the definition of cortical bone. The aim of this study was to develop methods of 3D rendering of the craniofacial skeleton and to ascertain their accuracy. "Black Bone" MRI datasets acquired from phantoms, adult volunteers and patients were segmented and surface and/or volume rendered using 4 commercially available or open source software packages. Accuracy was explored using a custom phantom (permitting direct measurement), CT and MRI. "Black Bone" MRI datasets were successfully used to create 3D rendered images of the craniofacial skeleton in all 4 software packages. Comparable accuracy was achieved between CT and MRI 3D rendered images of the phantom. The "Black Bone" MRI technique provides a viable 3D alternative to CT examination when imaging the craniofacial skeleton.

Mass spectrometry imaging-based multi-modal technique: Next-generation of biochemical analysis strategy

Atypical Teratoid Rhabdoid Tumor (AT/RT) is a highly invasive malignant embryonal tumor that is characterized by its low survival rate among pediatric patients. AT/RT spreads through the cerebral spinal fluid (CSF) and white matter tracts (WMTs) to other parts along the brain. Due to its rarity, AT/RT affects only a small number of pediatric patients, therefore studies on the tumor have been limited. While standard Magnetic Resonance Imaging (MRI) techniques offer valuable insight to characterize and detect AT/RT, incorporating advancing imaging techniques such as Diffusion Weighted Imaging (DWI), Diffusion Tensor Imaging (DTI), MR Spectroscopy (MRS), and Perfusion Weighted Imaging (PWI) significantly improves diagnostic accuracy, facilitates early detection of tumor spread, and overcomes the limitations of standard imaging techniques. This paper examines and provides clinical recommendations on how advanced imaging techniques can be used with standard imaging techniques to diagnose AT/RT and identify recurrence in pediatric patients. Additionally, this paper proposes that artificial intelligence (AI) powered Machine Language algorithms be used to statistically recreate DWI, DTI and PWI from conventional MRI scans for use in resource-constrained healthcare settings so as to diagnose AT/RT as well as to distinguish between AT/RT and other brain tumors. It also proposes creation of synthetic pediatric MRI images from adult MRI counterparts so as to expand pediatric MRI image database paucity. Genetic and epigenetic approaches to further improve detection and treatment of AT/RT are also discussed.

Mild traumatic brain injury (mTBI) constitutes the majority of brain trauma cases. Despite its prevalence, detection in clinical imaging remains a challenge, as does the ability to predict duration and extent of disability. Advanced magnetic resonance imaging (MRI) methods combined with improved data analytic techniques have already demonstrated the potential to meet this challenge. This chapter reviews the recent progress in detection and outcome prediction in mTBI using the latest MRI techniques, including diffusion tensor imaging (DTI), susceptibility weighted imaging (SWI), MR spectroscopy (MRS), and perfusion imaging. In the past five years, several published reports have found that DTI is sensitive to alterations in white matter ultrastructure which are not revealed in conventional MRI. More specifically, DTI reveals alterations in the ultrastructure of white matter axons caused by traumatic shear and stretch, which have been shown to correlate with clinical severity indicators and neuropsychological deficits. By virtue of its excellent sensitivity to iron and deoxygenated hemoglobin, SWI has demonstrated exquisite detection of hemorrhages, including the smallest micro-hemorrhages, which are frequently seen in TBI. MRS is capable of detecting indicators of injury by quantification of cerebral metabolic compounds (i.e. metabolites) which have also been found to be predictive of outcome and neuropsychological impairments. Measurement of perfusion has demonstrated utility in moderate and severe TBI using radioisotope techniques such as SPECT and PET and is now being explored using high-resolution flow sensitized MRI methods. Used together, these advanced imaging techniques have the potential to serve as a set of surrogate biomarkers which can be used in determining prognosis and will likely have a major role in animal and human therapeutic trials, both to improve selection criteria of experimental subjects and to provide a number of new biomarkers to follow in addition to conventional clinical and behavioral measures. These methods, in addition to still other MRI methods, including functional MRI and functional connectivity, may help to reveal the neural mechanisms underlying neurocognitive recovery following TBI. Therefore, it is expected that continued progress using these advanced MR imaging techniques at all stages of TBI will likely impact the routine diagnosis care of TBI including mTBI in the not too distant future.

MRI of articular cartilage in OA: novel pulse sequences and compositional/functional markers

Tumor angiogenesis is the important biological process whereby new blood vessels are formed to supply nutrients and oxygen and to remove waste products for growing tumors. Angiogenesis plays key roles in forming and regulating the tumor micro‐environment, enabling metastatic disease, and greatly affects the delivery and response of targeted therapeutic agents. Targeting the tumor vasculature may represent a promising strategy to inhibit tumor growth and progression. Thus, this key biological process is being vigorously studied with the goal of impacting human clinical care. Physical approaches to understanding tumor angiogenesis include magnetic resonance imaging (MRI), which through various dynamic techniques can assess blood flow and other bioanatomic parameters relevant to angiogenesis. These advanced imaging techniques can be used in both pre‐clinical animal models as well as humans. Importantly, anti‐angiogenic therapies include pharmacologic and biologic agents that target tumor vascular through various biomolecular mechanisms, and tumor response can be monitored using advanced MR imaging.For the benefit of the medical physicist who may be involved with angiogenesis research using MRI, targeted biochemical agents, and/or ionizing radiation, this symposium will review the biology of tumor angiogenesis, advanced MR imaging techniques, and translational efforts, including clinical trials and angiogenesis research challenges.Specific objectives of the symposium are to:1. Provide a primer on the biology of tumor angiogenesis and the tumor microenvironment2. Review the important role of angiogenesis for the formation of metastases3. Discuss biological mechanisms for the interruption of angiogenesis that would lead to a therapeutic result4. Describe pre‐clinical and clinical magnetic resonance imaging techniques and applications for tumor vascular imaging5. Review techniques and research challenges for quantitative MR imaging of angiogenesis, including national initiatives6. Describe promising anti‐angiogenic therapies with targeted biochemical agents and ionizing radiation7. Describe angiogenesis clinical trials, challenges in translating angiogenesis research to the clinic, and roles for medical physicists in angiogenesis imaging and therapeutics.

Magnetic resonance imaging – unravelling the mystery

Novel Imaging Techniques in Detection of Progressive Multiple Sclerosis

Despite decades of advancement in the diagnosis and therapy of gliomas, the most malignant primary brain tumors, the overall survival rate is still dismal, and their post-treatment imaging appearance remains very challenging to interpret. Since the limitations of conventional magnetic resonance imaging (MRI) in the distinction between recurrence and treatment effect have been recognized, a variety of advanced MR and functional imaging techniques including diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), perfusion-weighted imaging (PWI), MR spectroscopy (MRS), as well as a variety of radiotracers for single photon emission computed tomography (SPECT) and positron emission tomography (PET) have been investigated for this indication along with voxel-based and more quantitative analytical methods in recent years. Machine learning and radiomics approaches in recent years have shown promise in distinguishing between recurrence and treatment effect as well as improving prognostication in a malignancy with a very short life expectancy. This review provides a comprehensive overview of the conventional and advanced imaging techniques with the potential to differentiate recurrence from treatment effect and includes updates in the state-of-the-art in advanced imaging with a brief overview of emerging experimental techniques. A series of representative cases are provided to illustrate the synthesis of conventional and advanced imaging with the clinical context which informs the radiologic evaluation of gliomas in the post-treatment setting.

With the introduction of new biologics such as anti-TNF-alpha antibodies and other therapies in the treatment of inflammatory arthritis, capable of halting joint destruction and functional disability, there are new pressures on diagnostic and prognostic imaging. Early demonstration of pre-erosive inflammatory features and monitoring of the long-term effects of treatment are becoming increasingly important. Early detection of synovitis offers advantages in terms of allowing early instigation of therapy and may allow the identification of those patients displaying more aggressive disease who might benefit from early intervention with expensive DMARD therapy. Advanced imaging techniques such as ultrasound (US) and magnetic resonance imaging (MRI) have focussed on the demonstration and quantification of synovitis and allow early diagnosis of inflammatory arthropathies such as rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Synovitis represents a potential surrogate measure of disease activity that can be monitored using either MRI or US; the techniques have, generally, focused on monitoring synovial volume or quality as assessed by its vascularity. However to achieve these goals, standardisation and validation of US and MRI are required to ensure accurate diagnosis, reproducibility and reliability. Each modality has different strengths and weaknesses and levels of validation. This article aims to increase the awareness of radiologists and rheumatologists about this field and to encourage them to participate and contribute to the ongoing development of these modalities. Without this collaboration, it is unlikely that these modalities will reach their full potential in the field of rheumatological imaging. This review is in two parts. The first part addresses the role of US and colour or power Doppler sonography (PDUS) in the detection and monitoring of synovitis in inflammatory arthropathies. The second part will look at advanced MR imaging and Dynamic contrast-enhanced MRI techniques and in particular how they are applied to the monitoring of the disease process. (www.actabiomedica.it)

Background and Aims Novel Magnetic Resonance Imaging (MRI) techniques are potential methods to non-invasively assess and quantify functional, structural and pathophysiological changes in chronic kidney disease (CKD) that may improve diagnosis, prognosis and treatment of these patients. Advances in imaging techniques are also likely to result in the detection of unexpected and asymptomatic incidental findings. We retrospectively analyzed the overall prevalence of incidental findings in the participants of our previously reported study utilizing a non-contrast multiparametric MRI protocol in patients with type 2 DM (T2DM) as compared to healthy controls. Method The subjects of this sub-study were participants of our original prospective, single-center, observational study, in which several MRI biomarkers were evaluated to differentiate diabetic versus healthy kidneys, and various stages of CKD. A complete medical history and physical examination were performed. The inclusion criteria for the T2DM cohort were: Age 18-70 years, type II DM with CKD staged 3-4 (estimated glomerular filtration rate [eGFR] 15-60 ml/min/1.73 m2, body mass index (BMI) 18-35 and provision of written informed consent. The control group comprised of healthy volunteers who were age- and sex-matched and had the following inclusion criteria: Age 18-70 years, eGFR >80 ml/min/1.73 m2, UACR <30 mmol/g, BMI 18-35 and provision of written informed consent. Exclusion criteria for the diabetic group were any apparent cause/s of CKD other than diabetes, previous kidney transplantation, pregnancy, contraindication for MRI examination, heart failure (NYHA class III or IV), allergies to iodine-based contrast agents. Factors that excluded healthy participants were pregnancy, contraindication for MRI examination, allergy to iodine-based contrast agents and any active or chronic disease/diagnosis. Measured GFR (mGFR) was assessed in all participants using iohexol clearance. An MRI scan using a wide range of non-contrast techniques was performed at baseline. Total scan time for patients did not exceed 45 min per session and no gadolinium-based contrast agents were used in any of the MRI examinations. All patients with incidental findings on MRI were further evaluated and referred to appropriate specialists for management. Results A total of 38 T2DM patients with CKD and 20 age- and gender-matched healthy volunteers who completed the study were included in the analysis. Of the T2DM patients, 2 were found to have CKD stage 2 by mGFR and 36 CKD stages 3–4. Clinically significant incidental findings (excluding 4 cases of renal cysts requiring only follow-up without further intervention) were found in 13 of the 38 (34%) T2DM patients. The most frequent findings were intraductal papillary mucinous neoplasm (IPMN) in 7 patients, followed by 3 cancers (1 case of kidney cancer, 1 bladder cancer and 1 lymphoma) and 3 cases of adrenal gland mass later diagnosed to be benign adenoma on further investigation. In contrast, of the 20 healthy volunteers, 2 (10%) were found to have significant incidental findings, which were IPMN in both. The follow-up duration varied between 2-6 years. The patient with bladder cancer had metastatic disease and died shortly after the diagnosis, the one with kidney cancer is under observation and the one with lymphoma underwent adequate treatment and is under remission. The cases of IPMN are being followed up regularly at our surgical department. Conclusion Clinically important incidental findings on renal MRI appear to be more common in T2DM patients than in healthy volunteers, which would have been missed without MRI examination. Mechanisms for reporting and strategies for dealing with incidental findings need to be taken into account in such investigational imaging studies. The detection of incidental findings also poses various practical and ethical issues. Further larger studies with long-term follow-up are needed to delineate the clinical relevance, natural course and management of such incidental findings.

Shall We Bury the Sword? Imaging of Hepatic Fibrosis

Despite extensive study, the optimal imaging modality for the diagnosis of a suspected scaphoid fracture remains controversial. Traditionally, patients with clinical findings consistent with scaphoid fracture but with negative initial radiographs have been managed with splint or cast immobilization followed by repeat clinical and radiographic examination two weeks following injury. However, given the relatively low prevalence of true fractures in this population, the classical approach has been criticized for overtreating a majority of these patients. To avoid diagnostic delay and unnecessary immobilization, advanced imaging techniques have gained popularity to facilitate early definitive diagnosis of scaphoid fractures. Studies advocating the use of magnetic resonance imaging (MRI), computed tomography (CT), bone scintigraphy, and ultrasound in the evaluation of suspected scaphoid fractures are plentiful. Among these imaging modalities, MRI has emerged as a relative gold standard, due to both its excellent reported diagnostic performance as well as its ability to identify alternate causes of wrist pain. Criticisms of MRI have been that it is susceptible to misinterpretation of injuries such as bone bruises, potentially resulting in false positive results, and that it has limited capacity to demonstrate subtle degrees of fracture displacement. The use of CT in the acute diagnosis of scaphoid fractures is less well documented but has been advocated because of its lower costs and widespread availability, although the diagnostic accuracy of CT in this situation has been questioned1. Although current institutional protocols vary, an often recommended algorithm is to first proceed …