Anatomy and Embryology Meninges The meninges, which form the coverings of the brain and spinal cord, develop from the meninx primitiva. The neural tube is surrounded by this dense cellular layer shortly after the neural tube closes. As early as 32 days and as late as 44 days of gestation, the meninx primitiva begins to cavitate to form the cerebral cisterns by gradually decreasing its cellular…
Introduction The first reported in vivo localized proton ( 1 H) magnetic resonance spectroscopy (H1-MRS) studies of the human brain were first reported over 20 years ago. Since these early studies, in vivo H1-MRS brain studies have been shown to be a powerful technique to noninvasively investigate the biochemistry of the human brain and to assess in situ the neurochemical profile of brain tissue. Thus they…
Introduction Magnetic resonance imaging (MRI) is very adept at displaying structural anatomy of the brain in great detail. However, the correlation between anatomy and function is not always clear or apparent, and this becomes particularly difficult in situations where the anatomy deviates from the expected owing to developmental anatomic variation or if there is structural distortion by disease. A few short years after the clinical use…
It is often clinically difficult to differentiate among the various neurodegenerative disorders such as dementias, hydrocephalus, and movement disorders, and even between pathologic and normal aging. In recent years, more specific and sensitive neuroimaging criteria have evolved to more accurately establish the correct diagnosis in these disorders. Magnetic resonance imaging (MRI), with its ability to image both the structure and function of the living brain, is…
Introduction More than 10,000 spinal cord injuries are diagnosed each year in the United States, with over half involving the cervical spinal cord. Multidetector computed tomography (CT) is recommended by the American College of Radiology as the first-line screening exam for any patient for whom spine injury cannot be excluded on clinical grounds alone. Coronal and sagittal spine reformats are also commonly incorporated into whole-body CT…
Introduction Nearly 2 million cases of traumatic brain injury (TBI) occur each year. Worldwide, trauma is the leading cause of death and disability in those younger than 45 years, with nearly half of fatalities resulting from TBI. In younger patients, traffic accidents are the leading cause of TBI, and in the elderly, falls are the principal cause. TBI is a heterogeneous disorder with different forms of…
Cerebral Aneurysms Incidence and Natural History The incidence of a cerebral aneurysm in the general population is 0.5% to 5%. Women more commonly harbor a cerebral aneurysm than men, and aneurysm development increases with advancing age. Some families demonstrate a genetic predisposition to develop cerebral aneurysms, with a prevalence of 4% when a first-degree relative has a confirmed aneurysm, increasing to 8% if two first-degree relatives…
Introduction Stroke is the second leading cause of death worldwide. Globally an estimated 16.9 million cases of new stroke occurred in 2010, resulting in 5.9 million stroke deaths. In the United States, a stroke occurs every 40 seconds, with a stroke death every 4 minutes. Although stroke mortality rates have reduced over the last 2 decades, the number of stroke survivors and disability-adjusted life-years lost from…
Computed tomography (CT) and magnetic resonance imaging (MRI) have become indispensable for diagnosis, evaluation, and treatment of intracranial infectious disease, contributing to significant decline in morbidity and mortality of these patients. CT is useful as a rapid screening tool to detect complications of intracranial infections such as hydrocephalus, extraaxial collections, and mass effect. MRI is superior for assessment of intracranial infections and allows for a more…
Introduction Based on data collected from several central cancer registries during the years 2007-2011, the Central Brain Tumor Registry of the United States (CBTRUS) estimates that 67,900 new cases of primary brain and central nervous system (CNS) tumors will be reported in 2014—one third of which will be malignant. The brain and CNS are also common sites of secondary tumor implantation; metastases may occur up to…
Introduction In the evaluation of diffuse and focal liver disorders, magnetic resonance imaging (MRI) has been proven to provide superior characterization of disease processes and therapy outcomes compared to other modalities in the imaging armamentarium. The particular strength of hepatic MRI is based on its unique ability to synergistically extract information on various soft tissue components in combination with assessment of functional liver status. To achieve…
Introduction The demand for pediatric magnetic resonance imaging (MRI) is steadily increasing because MRI is radiation free, has exquisite soft tissue contrast, and provides quantitative structural, functional, and vascular information for diagnosing a wide spectrum of diseases. Furthermore, the advent of genomics has led to improvements in understanding the genetic basis of a variety of heritable disorders associated with childhood neoplasms, so serial laboratory and radiologic…
Introduction Contrast agents used in magnetic resonance imaging (MRI) can be either endogenous or exogenous. The most common type of endogenous contrast-enhanced MRI is arterial spin labeling (ASL) techniques, which use a dynamic labeling of internal water to measure brain perfusion. ASL is noninvasive, and the sequences needed to acquire this type of imaging are included on most major vendors' platforms. However, ASL still suffers from…
Introduction Magnetic resonance angiography (MRA) enables noninvasive assessment of vascular disease in both the arterial and venous circulation. Owing to the availability of volumetric data sets without the need for ionizing radiation exposure and facilitated by technologic and methodological advances in hardware, data sampling, and image reconstruction approaches, MRA has become a powerful tool for the diagnosis of a variety of vascular pathologies. MRA techniques explore…
Magnetic resonance imaging (MRI) is based on spatially encoding a nuclear magnetic resonance (NMR) signal. Therefore an understanding of the basics of NMR is critical for understanding MRI, and this information is given in the first section of this chapter. Magnetic field gradients are used in MRI to spatially encode the NMR signal to obtain the raw MRI data, or k-space. Images are reconstructed from k-space…
Protocol Management and Optimization Protocols are the turn-by-turn instructions that allow the computed tomography (CT) operator to get from point A—registering the patient on the scanner from the order in the radiology information system (RIS)—to point B—sending a complete set of images to the picture archiving and communication system (PACS) for a radiologist to interpret. To comply with the National Electrical Manufacturers Association (NEMA) XR-29 standard,…
Computed tomography (CT) has grown quickly from an innovative specialized tool to a mainstay of medicine in every healthcare setting. Hospitals, outpatient clinics, and physician offices find CT to be an essential tool for patient diagnosis and management. Every year brings new advances in CT technology and applications. This chapter is dedicated to the basic principles and physics of CT operation. The practicing radiologist who can…
Overview Critical care ultrasound (CCU) is a noninvasive tool used for diagnostic evaluation and for guiding procedures in critical care patients. Ultrasound improves success and lowers complication rates when used to guide procedures such as vascular access and fluid drainage. Despite these advantages, formal training in CCU has not been incorporated into many fellowship programs, and training in this skill remains heterogeneous. The American Board of…
Overview Echocardiography provides intensivists with a means of rapidly assessing the anatomy and function of the heart in intensive care unit (ICU) patients with hemodynamic failure, thus guiding management. Since echocardiography is a key skill for frontline intensivists, developing effective training programs is essential to ensure that clinicians have competence in the field. This chapter discusses some issues related to training in critical care echocardiography (CCE)…
Overview Despite well-established evidence on the use of ultrasound for placement of any vascular access, a formal training program on how to perform ultrasound-guided vascular access (UGVA) and how to certify adequate competence has not been clearly defined. , According to recommendations by the National Institute for Clinical Excellence, those involved in UGVA should undertake appropriate training to achieve competence. Defining a competent practitioner in objective…