Anatomy: Imaging Overview- CT

Computed tomography or CT uses x-rays to generate slices of body parts, by rotating an x-ray source around a central axis, with computed reconstruction of the image based on complex mathematical calculations. The body part to be imaged is in the center of rotation on a movable table, within a tube shaped like a donut.

1) recognize each type of imaging and physical property--displays slices or 'sections' of the body, no overlap of structures but each image only shows a limited part of the body; physical property is tissue DENSITY; you can recognize CT as cortical bone will be the whitest structure on the image, and normal fat will be dark grey

2) radiation--uses ionizing radiation, at a moderate dose, depending on whether the body area is scanned once or multiple times

3) technical factors are related to the particular PLANE of section (sagittal, coronal, axial or other), the brightness and contrast settings for image display (called a CT 'window'), and whether oral or IV contrast was given

4) WHITE areas are called 'densities' or 'high attenuation' and BLACK areas are called 'lucencies', 'low density', or 'low attenuation'

5) types of disease that are best displayed: bones including fine internal bony structure and fractures, organs, lymph nodes, GI tract walls, blood vessel walls, acute diseases of the body and central nervous system (because scanning can be done very quickly)

6) types of disease that are not well demonstrated: soft tissues such as tendons, ligaments, the internal layers of the uterus, or internal tracts of the central nervous system