Radiology Quiz 8/13 Flashcards
What are pixels?
small discrete units of digital information that together constitute an image. pixel is short for picture pix=plural and el=element.
What is sharpness/definition?
A geometric factor that refers to the detail and the clarity of the outline of the structures shown on the radiograph.
What is un-sharpness usually caused by?
movement of the patient, image receptor, or tube head during exposure.
True or False? Digital imaging sharpness can be affected by pixel size?
True
What is shadow casting?
Principle that x-rays cast shadows of images onto the image receptor, producing a radiographic image of the teeth and supporting structures.
What are the five principles of shadow casting? (these will help reproduce the size and shape accurately.)
1) Small focal spot to reduce PENUMBRA (partial shadow around objects of interest) resulting in a sharper image and slightly less magnification. 2) long target object distance to reduce the penumbra and magnification. 4) parallel relationship between object and image receptor: to prevent distortion of image. 5) perpendicular relationship between the central ray of the x-ray beam and both the object and image receptor: to prevent distortion of the image.
What is short scale?
60-70 KVP
What are the factors affecting radiographic image?
subject-differences in absorption of the x-rays by tissue
kvp,-there is an inverse relationship between kvp and contrast (lower=less shades, and higher many shades of gray)
scatter radiation-when x-rays interact with matter such as tissue on the patients head.
film/digital sensor type-each film has its own inherent(built-in contrast that may vary from manufacturer.
exposure-an underexposed or an overexposed radiograph will result in diminished or poor contrast.
processing-can only be obtained by meticulous film processing procedures.
What is distortion?
The result in unequal magnification of different parts of the same object. This happens when the image receptor is not parallel to the object.
What is long scale?
80-100 KVP many shades of gray
Exposure factors on image density?
Increased MA=darker, decreased Ma=lighter, Increased time=darker, decreased time=lighter, increase KVP=darker, decreased KVP= lighter
What are radiographic errors?
incorrect positioning of the image receptor, not recording anterior structures, not recording posterior structures, not recording coronal coronal structures, slant or tiltionstead of straight occlusal plane, incorrect position of film dot, reversed image error, conecut, double image, blank clear image, green film, artifacts,light thin dark image..
T/F The smaller the pixels the sharper the image?
True
T/F Too many pixels will slow down the acquisition of the image?
True
What is the ideal level of contrast?
This is individual preference.
