1 What is a solitary pulmonary nodule (SPN)? An SPN is a solitary focal lesion in the lung that measures 3 cm or less. A solitary focal lesion that is greater than 3 cm is considered to be a mass, and most masses are malignant. Approximately 150,000 SPNs are detected annually in the United States, often incidentally on imaging. A goal of radiologic evaluation of SPN is to…
1 What are the clinical indications for computed tomography angiography (CTA) and magnetic resonance angiography (MRA) of the peripheral and visceral arteries? CTA and MRA are noninvasive methods of assessing the arteries and veins, which have all but replaced catheter angiography. The clinical indications for these examinations can be thought of in the following broad areas: Ischemia. Aneurysm Compression syndromes. Traumatic injury. 2 What is the…
1 What is the normal appearance of the pulmonary vessels on computed tomography (CT) and magnetic resonance imaging (MRI)? The main pulmonary artery originates from the right ventricular outflow tract, anterior and to the left of the aortic root, and serves as a conduit for blood from the right ventricle to the pulmonary circulation. It bifurcates into the right and left pulmonary arteries. The right pulmonary…
1 What are some noninvasive methods of coronary artery imaging? Imaging the coronary arteries is an important part of evaluating ischemic heart disease. Traditionally, this imaging has been performed using cardiac catheterization, an invasive procedure that requires arterial puncture. Newer technologies promise noninvasive, cross-sectional imaging of coronary artery patency and offer the potential to characterize coronary artery plaque. Coronary magnetic resonance imaging (MRI), using bright blood,…
1 What is the normal imaging appearance of the aorta on computed tomography (CT) and magnetic resonance imaging (MRI)? The normal aorta on imaging can be divided into the following five parts: the aortic root, the ascending aorta, the proximal (anterior) aortic arch, the distal (posterior) aortic arch, and the descending thoracic aorta. The proximal segment of the ascending aorta is the aortic root, which begins…
1 What forms the borders of the heart on the frontal posteroanterior (PA) or anteroposterior (AP) chest radiograph? The chest radiograph represents an important first step in the imaging workup of cardiovascular disease. On a PA frontal view of the chest, a cardiothoracic ratio (cardiac width : thoracic width) of less than 1 : 2 is considered normal in adults. Analysis of the cardiac silhouette can yield valuable information about…
1 What are the indications for breast magnetic resonance imaging (MRI)? General indications for breast MRI include: Establish the extent of disease in the setting of a newly diagnosed breast cancer. Further evaluate an imaging finding that is incompletely characterized by diagnostic mammography and/or breast ultrasonography (US). Evaluate for residual disease in the setting of positive margins after lumpectomy or other operative procedure. Evaluate a patient…
1 What are the labeled structures on the ultrasound image in Figure 10-1 ? The structures are skin (A), subcutaneous fat (B), glandular tissue (C), fat (D), muscle (E), and rib (F). 2 What type of transducer should be used to perform breast US? A linear array transducer should be used. It should ideally have a frequency of 10 MHz or greater. 3 List the indications for…
1 What are the indications for a diagnostic mammogram? Some indications for a diagnostic mammogram include a history of breast cancer, breast lump, nipple discharge, focal breast pain, breast implants, history of breast biopsy, history of an abnormal mammogram, and follow-up for a previously evaluated mammographic finding (BI-RADS category 3 lesion). 2 What views are performed for diagnostic mammography? How are patients who have undergone diagnostic…
1 What is a screening mammogram? A screening mammogram is a radiographic examination of the breasts performed to detect clinically occult breast cancer in asymptomatic women. 2 When should an average woman start getting mammograms? This is currently a topic of debate. The American College of Radiology (ACR) recommends that a woman get a baseline mammogram at age 40 and annual screening mammograms thereafter. The American…
1 What is the terminology for radiation dose? Absorbed dose, equivalent dose, and effective dose are all used to describe the effects of radiation on tissue. Absorbed dose specifically refers to the energy transferred to a quantity of tissue by ionizing radiation. Equivalent dose can be derived from absorbed dose by applying a weighting factor that describes the type of radiation, in order to account for…
1 What is a radiographic contrast agent? A radiographic contrast agent is a substance that is administered to a patient during an imaging examination to improve its diagnostic performance. Contrast agents are most often administered via the intravenous (IV) and oral routes for computed tomography (CT) and magnetic resonance imaging (MRI) examinations. However, other routes of contrast administration may be utilized, depending on the particular imaging…
1 What is PACS? PACS stands for Picture Archiving and Communication System. On the most basic level, PACS integrates image acquisition modalities, workstation displays, the image archiving system, and the underlying network. 2 How are PACS images stored? The PACS archive traditionally has been composed of short-term and long-term storage. Short-term storage is usually composed of redundant arrays of inexpensive (or independent) discs (RAID) arrays that…
1 What is a digital image? A digital image is an image discretized in spatial coordinates and in brightness. It can be represented by a multidimensional array of integers. 2 What is the difference between a pixel and a voxel? A pixel, or picture element, is the smallest element of a 2D digital image that can be individually processed, whereas a voxel, or volume element, is…
1 What is molecular imaging? Molecular imaging is the visualization, characterization, and measurement of biologic processes at the molecular and cellular levels in humans and other living systems. It is essentially a noninvasive means to study in vivo biochemistry and cell biology and is useful to optimize diagnosis and therapy of disease in individualized patients. Nuclear medicine techniques and optical imaging techniques are most commonly used…
Ultrasonography (US) 1 What is ultrasonography (US), and how does it work? US is a structural imaging technique that uses high-frequency mechanical ultrasound waves (with frequencies greater than audible sound waves) to create real-time tomographic (cross-sectional) images. A hand-held transducer is applied to a part of the body to transmit ultrasound waves into the patient. Reflected ultrasound waves (echoes) are then detected by the transducer and…
Radiography 1 What is radiography? Radiography is an imaging technique that uses x-rays to create projectional (2D) images of a region of interest in the body. It is performed by shining x-rays on a film or other image detector with a patient placed in front of it in a certain orientation. Different types of tissues in the patient attenuate x-rays to different degrees, leading to formation…
Introduction The Digital Revolution began in the latter half of the 20th century with the first uses of digital computers and data storage. The 1970s saw the development of the first microprocessor, Intel’s 4004, which marked the advent of the rapidly doubling processor speeds predicted by Moore’s Law. These exponential increases in computing power have since drastically changed how businesses and individuals interact by leading to…
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Introduction Historically, to be successful in their professional careers, radiologists must train intensively for years. They must master a daunting amount of clinical material, pass comprehensive tests, and meet a wide array of challenges in their training. That has not changed during my own career (now around a quarter-century in length) and, if anything, the amount of material that radiologists are expected to master keeps increasing…