A method of computed tomography that uses radionuclides which emit a single photon of a given energy. The camera is rotated 180 or 360 degrees around the patient to capture images at multiple positions along the arc. The computer is then used to reconstruct the transaxial, sagittal, and coronal images from the 3-dimensional distribution of radionuclides in the organ. The advantages of SPECT are that it can be used to observe biochemical and physiological processes as well as size and volume of the organ. The disadvantage is that, unlike positron-emission tomography where the positron-electron annihilation results in the emission of 2 photons at 180 degrees from each other, SPECT requires physical collimation to line up the photons, which results in the loss of many available photons and hence degrades the image.
Work consisting of bibliographic records, created according to specific and uniform principles of construction and under the control of an authority file, which describe the materials contained in a collection, library, or group of libraries. Catalogs include also lists of materials prepared for a particular purpose, such as exhibition catalogs, sales catalogs, garden catalogs, medical supply catalogs. (From The ALA Glossary of Library and Information Sciences, 1983)
Partial or complete opacity on or in the lens or capsule of one or both eyes, impairing vision or causing blindness. The many kinds of cataract are classified by their morphology (size, shape, location) or etiology (cause and time of occurrence). (Dorland, 27th ed)
The subdivisions used under Catholic Church may also be used under Catholic Church--Ambrosian rite; Catholic Church--Byzantine rite, etc. --subdivision Catholic Church under subjects, e.g. Asceticism--Catholic Church