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OD/Artifacts
Optical density, artifacts
Question | Answer |
---|---|
When only soft tissue is beng imaged, __ kVp and __ mAs are used. | Low, High |
___ kVp and __ mAs results in an image with satisfactory contrast and low patient radiation exposure. | High, low |
Radiolucent tissue appears ___ on radiographs. | Black |
Radiopaque tissue appears __ on radiographs. | White |
Destructive pathology causes tissue to appear __. | Radiolucent |
Constructive pathology causes tissue to appear __. | Radiopaque |
What is optical density? | Degree of blackening of the finished radiograph. |
In OD, black is has an OD of what number? | 4 or greater |
In OD, clear has an OD of what number? | Less than 0.2 |
OD is controlled by what 2 factors? | mAs and SID |
In order to produce a visible change in OD, mAs must be changed by __%. | 30% |
kVp must be change by __% to produce a perceptible change in OD. | 4% |
A __% increase in kVp accompanied by a half reduction in mAs results in the same OD. | 15% |
The simplest method for increasing or decreasing OD on an x-ray is to increase or decrease __. | mAs |
High kVp produces? | LONG scale, LOW contrast, LESS contrast |
Low kVp produces? | SHORT scale, HIGH contrast, MORE contrast |
Detail is controlled by? | Focal-spot size |
What are the three classes of artifacts? | Processing, Exposure and Handling |
Pi lines, dichroic stains and chemical fog are examples of what type of artifact? | Processing artifacts |
Motion, poor screen contact and improper grid position are examples of what type of artifact? | Exposure artifacts |
Kink marks, radiation fog and scratches are examples of what type of artifact? | Handing and storage artifacts |
What are two types of roller marks? | Guide-shoe marks and Pi lines. |
What is the cause of dichroic stains? | Improper squeezing of processing chemicals from film |
What is the cause of guide-shoe marks? | Improper position or springing of guide shoes in turn-around assembly. |
What is the cause of pi lines? | Dirt or chemical stains on rollers |
T/F: Dichroic stain is a type of chemical fog. | True |
T/F: Processing artifacts in digital radiography are different from those with screen-film because the method of producing the image is electronic instead of chemical. | True |
Name several handling and storage artifacts. | Fog, kink marks, crown |
What causes pressure marks? | Improperly or roughly handled film |
What causes fog? | High temperature or humidity |
What are the 3 types of static artifacts? | Crown, Tree and Smudge |