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Shear wave dispersion

Introduction Acoustic radiation force impulse (ARFI) is a continually developing technology that provides biomechanical information concerning tissue elasticity (stiffness) by emitting a push pulse, which generates laterally propagating shear waves (SWs). In addition to elasticity, viscosity provides biomechanical information concerning the pathologic state of tissue, which is a different property than elasticity alone. However, most ultrasound (US) elastographic models use a linear elastic model to describe…

Noninvasive assessment of liver steatosis with ultrasound techniques

Introduction Worldwide, obesity has nearly tripled since 1975. The World Health Organization (WHO) reports that, as of 2016, more than 1.9 billion adults 18 years or older were overweight, and, of these, over 650 million were obese. The WHO report underscores that most of the world’s population lives in countries where overweight and obesity kills more people than underweight. As for children, the report estimated that…

Liver shear wave elastography: Guidelines

Introduction Guidelines for the use of elastography in diffuse liver disease have been released by societies or federations of societies. The first set of guidelines was released by European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) in 2013. In 2015 the World Federation for Ultrasound in Medicine and Biology (WFUMB) and the Society of Radiologists in Ultrasound (SRU) produced guidelines on this topic,…

Liver stiffness beyond the staging of liver fibrosis

Introduction Shear wave elastography (SWE) assesses stiffness, not fibrosis. In addition to fibrosis, there are some factors or clinical conditions that may lead to an increase of liver stiffness (LS). They are known as confounding factors for fibrosis staging: liver inflammation, mostly gauged using transaminase values, which are indirect biomarkers; acute hepatitis; obstructive cholestasis; liver congestion; and infiltrative liver diseases. The first report of an increase…

The role of ultrasound in portal hypertension

Introduction Portal hypertension (PH) is a clinical syndrome characterized by an increase of the pressure gradient between the portal vein (PV) and the inferior vena cava (IVC) above 5 mmHg and develops when there is a resistance in the portal–venous system exacerbated by an increased splanchnic and portal–collateral blood flow. There are different types of PH, depending on the site of the increased resistance. Most often…

Staging liver fibrosis with shear wave elastography

Introduction Chronic liver disease is a major worldwide health problem. It may be due to several etiological factors that lead to necroinflammation with subsequent fibrosis (i.e., formation of scar tissue). Fibrosis, which is the consequence and not the cause of liver injury, may progress to cirrhosis and its complications if the cause of liver injury is left untreated. The prevalence of cirrhosis is probably underestimated as…

Artifacts in liver stiffness evaluation

Overview of artifacts in liver shear wave elastography The use of shear wave elastography techniques proves valuable in providing qualitative and quantitative elasticity maps of the liver. There are, however, common disturbances that can affect the tissue measurements of stiffness. Image artifacts, signals that appear present on the image but are not present in the body, can result in overestimation, underestimation, and highly variable calculations of…

Tips and tricks for liver stiffness evaluation

Before scanning the patient It is important to remember that liver stiffness is measured, not liver fibrosis. Liver stiffness is influenced by fibrosis, inflammation, and congestion. Therefore obtaining clinical information before starting the examination is helpful. Important patient factors that can influence liver stiffness include elevated transaminase values, acute hepatitis, infiltrative diseases, alcohol ingestion, increased right heart pressure, deep inspiration, and recent ingestion of food. These…

Protocols for liver stiffness acquisition

General protocol For all of the ultrasound (US) shear wave elastography (SWE) techniques (vibration controlled transient elastography [VCTE], point shear wave elastography [pSWE] and two-dimensional shear wave elastography [2D-SWE]), adherence to a strict protocol when assessing liver stiffness is required. The recommended items and the quality criteria that must be used follow. We use the convention that the region of interest (ROI) is the larger area…

Liver stiffness measurement techniques: Basics

Introduction to stiffness Liver diseases, such as nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH), alcoholic liver disease, viral hepatitis as well others, may be characterized by the accumulation of extracellular matrix material (collagen, fibronectin, proteoglycans, and glycosaminoglycans), fats and triglycerides, or tissue scarring, all of which increase tissue stiffness. Biologically, tissue stiffness is important for resisting forces at the cellular, intracellular, and super-cellular levels and for…

Conventional ultrasound findings in chronic liver disease

Introduction Chronic liver disease (CLD) is a substantial worldwide problem. Any disease that incites liver inflammation can lead to liver fibrosis, which can then progress to cirrhosis. The stage of liver fibrosis is important to determine prognosis, surveillance, progression, or regression of disease. The process of fibrosis is dynamic, and regression of fibrosis is possible up to the stage of early cirrhosis with treatment of the…

Artificial Intelligence and Radiology

Introduction Artificial intelligence (AI) is the field of computer science that involves the simulation of intelligent behavior by computers. It is used to predict, automate, augment, and optimize tasks historically done by humans. To provide an overall view of some of the key terms and their relationships to each other, see eFig. G.1 (each will be discussed in this chapter). Early Visionaries Alan Turing Many consider Alan…

Diagnostic Radiology Signs

A B C D E F G H I J K L M N O P R S T U V W Y A Absent Bow-Tie Sign Accordion Sign Air Bronchogram Air Crescent Sign Angel-Wing (Bat-Wing) Pattern Angel-Wing Sign (Spinnaker Sail Sign) Anteater Sign Aortic Nipple Apple Core Sign Arcuate Sign B Bamboo Spine Banana Sign Bankart Fracture Bear Paw Sign Beveled Edge Sign Bird’s Beak…

Key Terminology and Glossaries

General Terminology Like politics, all terminology is local. Follow the terminology conventions used in your hospital or, alternatively, the person rendering your course grade, even if those conventions are different from what is described here. You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in here

Radiation Dose and Safety

Ionizing Radiation in Radiology Utilizing the modalities of conventional radiography, computed tomography (CT), and fluoroscopy, diagnostic images are produced using ionizing radiation. It is well known that radiation can also have harmful effects if used in excess or certain situations. All healthcare providers should understand the risks associated with radiation exposure and limit exposure when possible. Three Fates of Radiation During an Imaging Procedure Transmitted radiation…

The ABCs of Heart Disease

This is a system for diagnosing cardiac disease in adults by asking a series of questions in a set fashion , the answers to which are certain fundamental observations made from the frontal chest radiograph alone. This system is for “adults only.” Infant hearts do not display many of the recognizable contours discussed here, so cardiovascular evaluation in infants depends much more on parameters like heart…

Nuclear Medicine: Understanding the Principles and Recognizing the Basics

How it Works A radioactive isotope (radioisotope) is an unstable form of an element that emits radiation from its nucleus as it decays. Eventually, the end product is a stable, nonradioactive isotope of another element. Radioisotopes can be produced artificially, most frequently by neutron enrichment in a nuclear reactor or in a cyclotron, or may occur naturally. Naturally occurring radioisotopes include uranium and thorium. The vast…

Recognizing the Findings in Breast Imaging

Breast imaging is the field of radiology dedicated to the detection and management of breast abnormalities, especially breast cancer. Breast cancer is second only to skin cancer as the most common cancer diagnosed in women and is the second leading cause of cancer death in women, behind lung cancer. Case Quiz 29 Question This is a view of both breasts from a mammogram of a 68-year-old…