Efectos De La Gasolina En Las Plantas

Páginas: 36 (8854 palabras) Publicado: 19 de noviembre de 2012
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David M. Yousem, MD Michael A. Kraut, MD, PhD Ara A. Chalian, MD

Major Salivary Gland Imaging1
The algorithm for imaging the salivary glands depends on the clinical scenario with which the patient presents to the clinician. Because of the importance of identifying small calculi in the gland or salivary duct as the cause of the symptom complex, nonenhanced computed tomographyis often the best initial study for the evaluation of the painful gland. If an infiltrative neoplasm is highly suspected, nonenhanced and enhanced magnetic resonance (MR) imaging may be superior in demonstrating perineural, meningeal, and skull base invasion. Sialography is reserved for the evaluation of chronic sialadenitides unrelated to sialolithiasis. Thin-section MR techniques for MRsialography may soon replace conventional sialography.

Index terms: Salivary glands, calculi, 264.818 Salivary glands, CT, 264.12111, 264.12112 Salivary glands, diseases, 264.247 Salivary glands, MR, 264.12141, 264.12143 Salivary glands, neoplasms, 264.363, 264.37 Radiology 2000; 216:19–29 Abbreviations: HIV human immunodeficiency virus SE spin echo
1

From the Department of Radiology, JohnsHopkins Hospital, 600 N Wolfe St, Houck B-112, Baltimore, MD 21287 (D.M.Y., M.A.K.), and the Department of Otorhinolaryngology: Head and Neck Surgery, University of Pennsylvania Medical Center, Philadelphia (A.A.C.). Received January 22, 1999; revision requested March 30; final revision received August 6; accepted August 18. Address correspondence to D.M.Y. (e-mail: yousem@rad.jhu.edu). RSNA, 2000While neoplasms of the major salivary glands constitute less than 3% of all tumors in the body, many people have an illness related to the salivary glands at some time in their lives. The process may be self-limited, such as with viral parotitis or mumps, but in others it may be a relapsing and remitting illness, such as chronic sialadenitis secondary to sialolithiasis. Still others may be evaluatedfor what is thought to be a salivary gland mass but is actually a mass peripheral to the glands, such as a lymph node. Very rarely, a nonnodal extraglandular lesion such as a schwannoma, masseteric hypertrophy, or other pseudomass may be mistaken for a glandular process, even by experienced otorhinolaryngologists (1). The purpose of this review is to illustrate the role of imaging in evaluatingdiseases of the major salivary glands. The range of studies needed to assess salivary gland lesions spans a wide gamut. Many of the disease processes described above may not require imaging of any kind. Still others may be readily evaluated with palpation and direct visualization either endoscopically or transorally. At the other end of the spectrum are infiltrative deep lobe parotid masses such asadenoid cystic carcinomas, which may require computed tomography (CT), magnetic resonance (MR) imaging, and/or conventional angiography as part of a preoperative evaluation for perineural, vascular, or skull base infiltration. Ultrasonography (US), underutilized in most North American sites, may supplant the role of CT and MR imaging for superficial salivary gland lesions when experiencedsonographers use the technique. Patients with major salivary gland lesions may present to the otorhinolaryngologist or oral and maxillofacial surgeon with a suspected mass, with a suspected obstruction or inflammation, or with diffuse glandular enlargement (2). Although there are overlapping entities in this simple stratification, the imaging studies ordered may change with each presentation. For thepurposes of this review, major salivary gland imaging will be divided into neoplastic lesions, obstructive or inflammatory lesions, and systemic diseases.

NEOPLASTIC LESIONS
The usual clinical manifestation of a salivary gland neoplasm is that of an enlarging mass. The first critical step in evaluating a mass is to determine whether or not it is painful. While painful masses may be produced by...
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