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Modes of Radioactive Decay

Radioactive decay is a process in which an unstable nucleus transforms into a more stable one by emitting particles, photons, or both, releasing energy in the process. Atomic electrons may become involved in some types of radioactive decay, but it is basically a nuclear process caused by nuclear instability. In this chapter we discuss the general characteristics of various modes of radioactive decay and their general…

Basic Atomic and Nuclear Physics

Radioactivity is a process involving events in individual atoms and nuclei. Before discussing radioactivity, therefore, it is worthwhile to review some of the basic concepts of atomic and nuclear physics. a Quantities and Units 1 Types of Quantities and Units Physical properties and processes are described in terms of quantities such as time and energy. These quantities are measured in units such as seconds and joules.…

What Is Nuclear Medicine?

a Fundamental Concepts The science and clinical practice of nuclear medicine involve the administration of trace amounts of compounds labeled with radioactivity (radionuclides) that are used to provide diagnostic information in a wide range of disease states. Although radionuclides also have some therapeutic uses, with similar underlying physics principles, this book focuses on the diagnostic uses of radionuclides in modern medicine. In its most basic form,…

Head and Neck Imaging

The “head and neck” encompasses extracranial structures from the skull base to the thoracic inlet including the orbits, nasal cavity, paranasal sinuses (PNSs), face, jaws, temporal bones and soft tissues of the neck, oral cavity, and upper aerodigestive tract. In this chapter we describe approaches to imaging, highlighting typical and atypical imaging features and the differential diagnosis for a variety of processes that involve the pediatric…

Spine Imaging

The spinal cord is an integral part of the neural axis or central nervous system. Disease entities in the brain or spinal cord may have a direct or indirect influence on each other. Imaging of the pediatric spine differs from that in adults in terms of relevant anatomy and associated pathology. An accurate imaging evaluation requires familiarity with the wide differential diagnosis of pediatric spinal disease.…

Brain Imaging

Imaging the Pediatric Brain The central nervous system (CNS) consists of the skull, brain, spine, and spinal cord. Imaging the brain in children differs from imaging adult patients in many respects. Ultrasound, a modality rarely used in adult neuroradiology, plays a central role in imaging the brain in fetal life and infancy. Similar to adult neuroradiology, magnetic resonance imaging (MRI) is now the most widely used…

Musculoskeletal Imaging

Imaging Techniques Radiography Conventional radiographs depict the bony detail of the skeletal system quite well and remain the mainstay in the evaluation of musculoskeletal disease. In the setting of acute trauma, radiographic views of the long bones are obtained in at least two projections, whereas joints are typically imaged in at least three projections. When bony injury to a digit is suspected, dedicated views of the…

Genitourinary Imaging

This chapter provides an introduction to pediatric genitourinary imaging for the radiology resident. It will focus on diseases commonly encountered in or specific to children and congenital anomalies. Diseases more commonly seen in adults will not be covered extensively in this chapter. The goal of this chapter is not only to describe genitourinary diseases, but also to convey a systematic approach for imaging evaluation of these…

Hepatobiliary, Pancreas, and Spleen Imaging

Liver and Biliary Tree Anatomy and Embryology The liver, gallbladder, and biliary tree originate from endodermal cells that form a diverticulum arising from the duodenal region of the primitive embryonic gut between 4 and 10 weeks' gestation. The larger cranial division (pars hepatica) gives rise to the liver, whereas the smaller, caudal portion (pars cystica) develops into the gallbladder and cystic duct. The intrahepatic and extrahepatic…

Gastrointestinal Imaging

To the radiologist who cares for adults, the exact age of a patient is rarely of great importance. To be sure, one approaches the chest radiograph of a 30-year-old differently from that of an 80-year-old. For the most part, however, we are all equally prey to the afflictions of senescence. For the pediatric radiologist, the situation is entirely different. To offer an interpretation of an image…

Cardiac Imaging

Congenital Heart Disease Congenital heart disease (CHD) occurs in approximately 1% of all live births, or 40,000 births annually in the United States. It remains the leading cause of birth defect–associated death in infancy. Approximately 25% of CHD defects are critical or severe, resulting in symptoms during the first year of life. About 25% of patients with CHD eventually die of their disease, and approximately 25%…

Chest Imaging

Imaging Techniques and Indications Conventional Radiography Diagnostic imaging plays an important role in the evaluation of the upper airway and chest in children. Chest radiographs comprise about 40% of all pediatric imaging, in large part because congenital and acquired respiratory disorders are so common. The most common indication for evaluation of the upper airway is stridor, or noisy breathing caused by airway obstruction. Stridor can be…

Fibrous dysplasia

Key points Definition: Fibrous dysplasia (FD) is typically a benign slowly progressing tumorlike process involving bone maturation in which normal cancellous bone is replaced by immature woven bone and fibrous tissue. Its predilection for the skull can cause serious orbital problems. Synonym: Lichtenstein-Jaffe disease. Classic clue: Preadolescent patient presents with painless proptosis and diplopia caused by an expanding enhancing sphenoid wing mass showing intact bony cortex.…

Orbital plasmacytoma and myeloma

Key points Definition: Plasma cell tumors may present as a solitary bone plasmacytoma (SBP), extramedullary plasmacytoma (EMP), or multiple myeloma (MM). While orbital involvement is rare and may not be associated with MM at presentation, it habitually heralds the unwelcome unleashing of this formidable foe (see Figure 49-3 , C ). Synonyms: Solitary bone plasmacytoma (SBP), solitary extramedullary plasmacytoma (SEP). Classic clue: a 60-year-old man presents…

Wegener granulomatosis

Key points Definition: Wegener granulomatosis (WG) is a systemic vasculitis causing necrosis and granulomatous inflammation, often presenting with a “runny nose.” Without modern treatment, most patients would quickly progress to death within a few short months. Synonym: granulomatosis with polyangiitis. Classic clue: Middle-aged Caucasian, sent for sinus examination for a “runny nose,” is found to have a medial orbital mass in addition to adjacent ethmoid sinus…

Pseudotumor cerebri

Key points Definition: Pseudotumor cerebri (PTC) is a clinical entity characterized by intracranial hypertension in patients without other demonstrable intracranial disease, including but not limited to primary or secondary neoplasm. Synonyms: idiopathic intracranial hypertension, benign intracranial hypertension. Classic clue: Obese female of childbearing age with diplopia, headache (HA), nausea, vomiting, and pulsatile tinnitus. Physical examination proves papilledema, visual field cuts, and cranial nerve (CN) VI palsy.…

Pott’s puffy tumor

Key points Definition: Pott’s puffy tumor is an osteomyelitis with associated subperiosteal abscess collection usually related to frontal sinusitis or mastoiditis. It may extend into the orbit causing inflammation including cellulitis, subperiosteal abscess, orbital abscess (OA), and cavernous sinus thrombosis. It poses a potentially life-threatening emergency, often requiring surgery. Synonym: Pott puffy tumor. Classic clue: Teenage boy presents with slow saga of recurrent headache, fever, and…

Cytomegalovirus retinitis

Key points Definition: Cytomegalovirus retinitis (CMVR) is an opportunistic infection that untreated leads to progressive retinal destruction and blindness. Synonym: CMV uveitis Classic clue: AIDS patient presenting with blurred vision, floaters, and blind spots found to have abnormal retinal thickening and enhancement with abnormal signal in the posterior chamber. CMV is a DNA virus from the herpesvirus group, also known as human herpesvirus 5 (HHV-5). ,…

Orbital abscess

Key points Definition: Orbital abscess (OA) is an intraorbital collection of neutrophils and microorganisms that has become a sight-threatening and potentially life-threatening emergency, requiring prompt imaging and treatment. Classic clue: Patient presenting with recent onset severe proptosis, complete ophthalmoplegia, and vision loss with retroorbital extraconal mass exhibiting “ring” enhancement and intraorbital air. The associated inflammatory response is a defensive reaction to prevent the spread of the…