Neuroimaging clinics of North America
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Neuroimaging Clin. N. Am. · Nov 2003
ReviewImaging the epileptic brain with positron emission tomography.
Positron emission tomography (PET) has an established role in the noninvasive localization of epileptic foci during presurgical evaluation. [18F]fluorodeoxyglucose (FDG) PET is able to lateralize and regionalize potentially epileptogenic regions in patients who have normal MR imaging and is also useful in the evaluation of various childhood epilepsy syndromes, including cryptogenic infantile spasms and early Rasmussen's syndrome. Novel PET tracers that were developed to image neurotransmission related to gamma-aminobutyric acid (GABA) [with [11C]flumazenil] and serotonin-mediated [with alpha-[11C]methyl-L-tryptophan (AMT)] function provide increased specificity for epileptogenic cortex and are particularly useful when FDG PET shows large abnormalities of glucose metabolism. Detailed comparisons of PET abnormalities with intracranial electroencephalographic findings also improve our understanding of the pathophysiology of human epilepsy.
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Because the diagnosis of mandibular ORN can often essentially be based on clinical grounds, radiology is used for confirmation and evaluation of the extent of the bone involvement. The localization and extent of the bone destruction can be better evaluated with CT than with conventional occlusal or panoramic films. Nevertheless, plain films often provide sufficient information for patient management. Based on the clinical evaluation and plain imaging findings, a decision can be made to treat patients conservatively or surgically.
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Neuroimaging Clin. N. Am. · Aug 2003
ReviewHodgkin and non-Hodgkin lymphoma of the head and neck: clinical, pathologic, and imaging evaluation.
Lymphomas are subdivided into HL and NHL and are more specifically classified into subtypes of HL or NHL according to the WHO classification. HLs involve the lymph nodes predominantly and only approximately 5% arise in extranodal sites, whereas 30% of NHLs present in extranodal sites. Imaging studies, including CT and MR imaging, cannot distinguish [figure: see text] HL from NHL, and cannot differentiate their various subtypes, necessitating a pathologic diagnosis. ⋯ MR imaging is preferred for the assessment of extension of lymphomas to different fascial spaces (parapharyngeal, masticator, infratemporal fossa, tongue, and nasopharynx) and for intracranial extension. Lymphomas are isodense to muscle on CT and circumscribed with distinct margins that occasionally display extranodal extension with less-well-defined margins and areas of necrosis within the tumor matrix. Lymphomas appear low in signal intensity on T1-weighted images and low to high in signal intensity on T2-weighted images, with variable, but usually low, enhancement following introduction of Gadolinium-DTPA (Gd-DTPA) contrast material.
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Benign odontogenic tumors are characterized by imaging findings of expansile growth and well-defined margins with smooth borders, and their appearance is very similar to that of odontogenic and nonodontogenic cysts. From the viewpoint of diagnostic imaging of odontogenic tumors, teeth are designed differently according to their origin from the apex or crown. Therefore, for differential diagnosis, it is necessary to select diagnostic methods that make it possible to evaluate these findings in detail. ⋯ MR imaging is effective in differentiating between tumors and cysts, evaluating the infiltration of malignant tumors in the jawbone and surrounding soft tissue, and detecting bone marrow changes of the jaw. Differentiation between tumors and cysts must be achieved by contrast-enhanced studies. Combining plain radiography with advanced imaging techniques, including CT and MR imaging, can improve the accuracy of diagnosing odontogenic tumors.
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Cystic lesions appearing in the maxilla and mandible have been shown with their typical radiographic features. In addition, this article has presented radiographic techniques used to diagnose these lesions. ⋯ Key features to differentiate among these cysts have been discussed. Finally, the article discussed the differentiation of jaw cysts from benign tumors that appear in the jaws.