Neuroimaging clinics of North America
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Neuroimaging Clin. N. Am. · Nov 2003
ReviewThe role of positron emission tomography imaging in movement disorders.
PET imaging provides the means to study neurochemical, hemodynamic, or metabolic processes that underlie movement disorders in vivo. Because the extent of presynaptic nigrostriatal dopaminergic denervation can be quantified in PD even at an early or preclinical stage of the disease, PET imaging may allow the selection of at-risk subjects for neuroprotective intervention trials. These techniques may also provide markers to follow progression of disease or evaluate the effects of neurorestorative interventions in patients who have more advanced disease. ⋯ Studies have shown striatal dopamine receptor loss in selected subtypes of dystonic patients. In conclusion, it is expected that PET will help us to better understand the pathophysiology of movement disorders, increase the diagnostic accuracy, allow preclinical diagnosis, monitor disease progression, and evaluate the efficacy of therapeutic agents. Pharmacologic radioligand displacement studies and the development of new nondopaminergic ligands may further aid in the unraveling of cerebral mechanisms that underlie movement disorders.
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This article described basic ideas and concepts that are related to the performance and analysis of dynamic tracer kinetic PET studies of brain. There are many aspects of these studies that require careful consideration, because there is always a compromise between accuracy and precision [101]. Important issues that were not discussed in this article include the appropriate use of anatomic information for the interpretation and analysis of the functional PET imaging data, ROI sampling, or parametric image generation; statistical analyses of ROI and parametric data; as well as steps involved in the evaluation of novel radiotracers and the identification of an analysis-of-choice or issues related to methodologic optimization. Fig. 5 is a summary diagram that links these ideas and provides a more complete picture of the multiple components that are involved in tracer kinetic PET imaging research.
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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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Neuroimaging Clin. N. Am. · Aug 2003
ReviewNasopharynx: clinical, pathologic, and radiologic assessment.
NPC represents 0.2% of malignant disease in the white population but is more common in southern China, among Chinese in East Asia and the United [figure: see text] States, and in North Africa, including Saudi Arabia. NPC in these ethnic groups tends to manifest at a younger age. Undifferentiated carcinoma is the most common histopathologic type and is associated with EBV. ⋯ In addition, the metastatic lymph nodes in the neck reveal no specific imaging features that would allow differentiation from other lymph node metastases. They may be discrete, often multiple, and large and bulky displaying a variable degree of necrosis and enhancement following introduction of contrast material. Local recurrence manifests commonly within the first 2 to 3 years posttherapy and is optimally evaluated by MR imaging and PET scanning.
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Because of its superior depiction of bone detail, CT is a useful tool in the characterization of CF deformities and presurgical planning. Modern CT scanners and workstations provide 2D techniques such as multiplanar reformats and 3D techniques, such as MIP and volume renderings, which may be used effectively in the diagnosis and management of patients with CF malformations.