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Radiology

Chapter 7 Vocab

QuestionAnswer
Distortion The difference between the actual subject and its radiographic image.
Umbra The portion of the image that is common to all points on the focal spot.
Penumbra The term used to describe the "unsharp edges" of the umbra, or body part.
Source-image receptor distance (SID) The distance between the tube-target and the film or imaging plane.
Inverse Square Law Radiation intensity is inversely proportional to the square of the distance.
Underexposed A film that is too light.
Overexposed A film that is too dark.
Tissue density The mass density of the radiographic subject that causes a lighter area on the radiograph because of greater absorption in some body parts.
Film/screen contact that property of the cassette that keeps the film in uniform tight contact with the two intensifying screens.
Contrast The difference in radiographic density between adjacent portions of the image.
Short scale contrast High level contrast produced by low kilovoltage. Approximately 5 gray tones.
Long scale contrast Low level contrast produced by high kilovoltage. Approximately 15 gray tones.
Subject contrast Radiographic contrast influenced by the tissue densities within the subject.
Latitude Long scale contrast.
Fog Unwanted exposure on the film that causes all parts of the image to appear as though seen through a gray veil.
Magnification That property of distortion wherein the image is larger than the object.
Object-image receptor distance (OID) The distance between the subject and the film.
Quantum Mottle The uneven distribution of photons within the x-ray beam.
Density The overall blackness or darkness of the radiograph.
Elongation A form of shape distortion where the projected part appears longer than it really is.
Foreshortening A form of shape distortion where the projected part appears shorter than it really is.
Penetrometer A solid piece of aluminum with steps of varying thickness. Often referred to as a step-wedge.
Radiographic Contrast The overall contrast seen in a radiographic image. It is a product of the IR (film) contrast and the subject (patient) contrast.
Recorded Detail The sharpness of the structures in the image. Also called detail, sharpness, and resolution.
Shape Distortion The result of unequal magnification of the actual shape of a structure. Displaces the projected image of an object from its actual position.
Size Distortion Distortion that is always in the form of magnification enlargement.
Voluntary Motion A normally controllable motion.
Involuntary Motion Movement over which the patient has no control, such as tremors, peristalsis, and heartbeats.
Created by: hollieritter