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Radiation Detection & Ancillary Instrumentation

The passage of radiation, such as x-rays and gamma rays, through a given material leads to ionizations and excitations that can be used to quantify the amount of energy deposited. This property allows measurement of the level of intensity of a radiation beam or small amounts of radionuclides, including from within the patient. The appropriate choice of detection approach depends on the purpose. In some cases,…

Radioactivity and Radionuclides

In nuclear medicine, radiopharmaceuticals given to the patient emit the radiation used to create images or perform therapy. In order to understand how these agents perform and what safety considerations are involved in their use, it is necessary to be familiar with some basic aspects of the physics behind radioactive decay. This chapter discusses radioactive molecules, different types of radioactive decay, and how these emissions interact…

Paget’s Disease

Introduction Paget's disease, or osteitis deformans, is a chronic metabolic disorder characterized by increased bone turnover and breakdown secondary to excessive and disorganized osteoclastic and osteoblastic activity ( Fig. 48.1 ). The precise etiology is still unclear. The excessive breakdown of bone is followed by the formation of weak and abnormal bone. Over time this robust and disordered bone metabolism can result in enlarged and/or deformed…

Otospongiosis

Introduction Otospongiosis, also known as otosclerosis, is a progressive primary bone disorder of abnormal bone resorption and deposition. The majority of cases result in a progressive conductive hearing loss with severe cases evolving to a combination of conductive and sensorineural hearing loss. The clinical prevalence of otospongiosis is estimated to be 0.3%, although histologic studies have reported a prevalence between 8% and 11%, indicating that many…

Vocal Cord Augmentation/Injection Laryngoplasty

Introduction Injection laryngoplasty is performed for treatment of vocal cord paralysis, which may have a variety of causes ( Box 46.1 ). Imaging during a Valsalva maneuver demonstrates the mechanical and physiologic barriers that patients with unilateral vocal cord paralysis endure ( Fig. 46.1 ). Vocal cord augmentation procedures attempt to overcome these barriers by medializing the affected vocal fold, thus allowing for better phonation and…

Esthesioneuroblastoma

Introduction Esthesioneuroblastoma (olfactory neuroblastoma) is an uncommon malignancy of the nasal cavity. Esthesioneuroblastoma represents 3% to 6% of sinonasal malignancies and has an estimated incidence of 0.4 cases per 1 million people. This tumor has been reported across a wide age range (2 to 94 years) and has no sex predilection. Some case series document a bimodal age peak in the second and sixth decades ;…

Paraganglioma

Introduction Paragangliomas of the head and neck are rare neoplasms of neural crest cell origin. The four most common sites for paragangliomas within the head and neck are at the carotid body, the jugular foramen, in the middle ear, and along the vagus nerve. Rarely, paragangliomas have been found within the larynx, orbit, thyroid gland, nasopharynx, mandible, soft palate, face, and cheek. Carotid body tumors account…

Labyrinthitis

Introduction Labyrinthitis, also known as otitis interna, is an inflammatory disorder of the inner ear. Inflammation of the perilymphatic spaces results in secondary changes within the membranous labyrinth, the most common symptoms of which are sensorineural hearing loss and vertigo. Causes of labyrinthitis are most commonly classified either by mode of spread (tympanogenic, meningogenic, hematogenic, posttraumatic) or by causative agent (viral, bacterial, autoimmune, syphilitic). Viruses are…

Cholesteatoma

Introduction A cholesteatoma is a cystic mass filled with keratin and lined by stratified squamous epithelium. Cholesteatoma is not a neoplasm and can be thought of most simply as skin in the wrong place. Although a cholesteatoma is histologically identical to an epidermoid or epidermal inclusion cyst, the term “cholesteatoma” is preferred for a lesion located in the middle or external ear ( Fig. 42.1 ).…

Sjögren Syndrome

Introduction Sjögren syndrome (SS) is a chronic autoimmune disorder characterized by inflammatory destruction of the body's exocrine glands and may be considered primary or secondary, in association with other autoimmune disorders, such as collagen vascular diseases. Although SS can present with a variety of symptoms, both glandular and extraglandular, initial presenting symptoms most commonly include decreased secretions of the major and minor salivary glands, leading to…

IgG4-Related Disease in the Head and Neck

Introduction Background IgG4-related disease (IgG4-RD) is a relatively recently recognized fibroinflammatory condition of unknown etiology characterized by elevated serum IgG4, plasmacytic infiltration, multifocal tumefactive fibrosis, and clinical improvement by steroid therapy. The association between autoimmune (sclerosing) pancreatitis and elevated serum IgG4 was first described by Hamano et al. in 2001, but it wasn't until 2003 that the systemic nature of IgG4-RD was discovered. After the pancreas, the…

Thyroid-Associated Orbitopathy

Introduction Thyroid-associated orbitopathy (TAO), thyroid eye disease (TED), dysthyroid/TAO, and Graves orbitopathy all refer to a poorly understood autoimmune phenomenon resulting in the adipogenesis of orbital fat. An estimated 40% of patients with Graves disease develop TAO. Up to 20% of patients presenting with thyroid orbitopathy are concurrently diagnosed with Graves disease. Affected populations naturally parallel that of Graves disease, and TAO occurs most commonly in…

Recurrent Suppurative Thyroiditis Due to Piriform Sinus Fistula

Introduction Anomalies arising from the third and fourth branchial cleft remnants are quite rare. In particular, branchial abnormalities related to the pharynx are only a small subset of the already rare collection of branchial cleft lesions. Branchial abnormalities with a sinus tract connecting to the pharynx usually present with acute suppurative thyroiditis and a thyroid abscess. The sinus tract connecting to the pharynx serves as a…

Orbital Infection

Introduction There are various forms of orbital infection, including those listed in the Jain-Rubin classification: 1. Periorbital cellulitis 2. Orbital cellulitis with or without intracranial complications 3. Orbital abscess with or without intracranial complications a. Intraorbital abscess, which may arise from collection of purulent material in an orbital cellulitis b. Subperiosteal abscess, which may lead to true infection of orbital soft tissues In addition, orbital infections…

Dorsal Thoracic Arachnoid Abnormalities

Introduction Deformities along the dorsal aspect of the thoracic spinal cord are occasionally identified on magnetic resonance imaging (MRI), often in patients presenting with myelopathy ( Fig. 36.1 ). A variety of nontumoral etiologies result in deformities of the dorsal thoracic cord, of which many are related to abnormalities of the dorsal arachnoid. These abnormalities include intradural arachnoid cyst as well as dorsal thoracic arachnoid webs,…

Hirayama Disease

Introduction Hirayama disease is a rare, slowly progressive, and self-limiting cervical myelopathy related to neck flexion in young adults. It is characterized by a pure focal amyotrophy in the C7-T1 innervated musculature. It presents classically in an adolescent male with progressive asymmetric upper extremity muscular weakness and atrophy. During neck flexion, forward displacement of the posterior dural sac is thought to result in minimal but additive…

Spinal Cord Astrocytoma

Introduction Spinal cord astrocytomas are quite uncommon and account for only 3% to 4% of all central nervous system (CNS) astrocytomas. Furthermore, although intracranial glioblastomas are the most common primary brain parenchymal neoplasm, spinal cord glioblastomas are exceedingly rare. The characteristic asymmetric location of small spinal cord astrocytomas is due to the location of their peripherally located astrocytic cells of origin, as well as their affinity…

Spinal Cord Ependymoma

Introduction Spinal cord ependymomas are the most common intramedullary tumor in adults and the second most common tumor in children after astrocytomas. Ependymomas typically present within the fourth decade of life and affect men more often than women. A higher incidence of these tumors occurs in patients with neurofibromatosis type II. The presenting symptoms are often insidious and nonspecific, with the majority of patients being symptomatic…

Subacute Progressive Ascending Myelopathy

Introduction Subacute progressive ascending myelopathy (SPAM) is an exceedingly rare and poorly understood complication of spinal cord injury. As the natural history of this process is quite peculiar, it is especially important for the imaging interpreter to be aware of this entity. Following a latent period a few weeks after spinal cord injury, patients usually present with an abrupt ascending neurologic deficit. The sudden onset of…