PA Anatomy: Imaging Overview-Contrast

Contrast x-ray studies can involve introduction of contrast material into the gastrointestinal (GI) tract or into the vascular system (angiography) or any other body cavity or region. GI contrast can be given orally or rectally or instilled into an indwelling tube, and may contain barium or iodine-based material. Iodine-based contrast is used for vascular structures, which include arteries (arteriography) or veins (venography); actual motion of objects can be seen with fluoroscopy (real-time radiography) and captured with video

1) recognize each type of imaging and physical property--NOT a slice, gives a view of an entire region with overlapping structures, physical property is tissue DENSITY

2) radiation--uses ionizing radiation, at a high dose, depending on the type of study, much higher dose than for radiographs,

3) technical factors are mostly related to the way the images are captured, and may include rapid sequence imaging to give a time-lapse appearance, or 'digital subtraction', which removes background structures, leaving only the contrast material

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

5) types of disease that are best displayed: fine detail of blood vessels (for angiograms), views of large regions of the inner surface of the GI tract, evaluation of motility of the GI tract

6) types of disease that are not well demonstrated: soft tissues such as organs, outer wall of GI tract structures, outer wall of vascular structures