| Radiology exposure |
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| Define contrast |
difference in adjacent densities |
| Define quantity |
The radiation intensity or the number of x rays in the beam, measured in mR |
| Define the relationship between ma and tube current |
Directly proportional |
| Define the relationship between ma and mR |
Directly proportional |
| Describe the relationship between exposure time and density |
Directly proportional |
| Describe the relationship between time and mR |
Directly proportional |
| Describe the relationship between mAs and density |
Directly proportional |
| describe the relationship between kVp and mR |
Inversely proportional |
| Describe the relationship between SID and mR |
inversely proportional |
| Identify 4 imaging characteristics controlled by SID |
magnification, distortion, penumbra and density |
| Define the reciprocity law. |
Any combination of mA and time can be used to get the same mAs with the same result in density. |
| What is the 15% rule? |
If kVp is increased by 15%, mAs will be halved. If kVp is decreased by 15%, mAs will be doubled. |
| ma + s = |
mAs |
| What is the density maintenance formula? |
new mAs/old mAs = new D^2/old D^2 |
| What is meant by low contrast? |
lots of gray |
| What is meant by high contrast? |
few shades of gray |
| How do you get a higher contrast on a film? |
lower the kVp |
| How do you get a lower contrast on a film? |
Use a higher kVp |
| What are the prime factors for exposure? |
mA, kVp, distance and time |
| What is quality? |
the penetrability of the beam |
| What is the controlling factor of contrast? |
kVp |
| What is the controlling factor of density? |
mAs |
| What is the relationship between kVp and scatter? |
Directly proportional |
| What is the function of contrast? |
To make details visible |
| What is meant by short scale contrast? |
Few shades of gray |
| What is meant by long scale of contrast? |
Many shades of gray |
| What is subject contrast? |
The range of differences in the intensity of the remnant x ray beam after it has been attenuated by the patient. |
| What is image receptor contrast? |
The range of densities the image receptor is capable of recording. |
| Five factors that affect image receptor contrast |
H & D curve, image density, processing, digital image receptors, intensifying screens |
| Three factors that affect subject contrast? |
kVp, amount of tissue irradiated, type of tissue irradiated. |
| How does mAs affect radiographic contrast |
Under or over exposure |
| How does focal spot size affect radiographic contrast |
No influence. |
| How does the anode heel effect affect radiographic contrast? |
Little effect |
| How does filtration affect contrast? |
Inversely related. |
| How does beam restriction (collimation) affect contrast? |
Inversely related. |
| How do grids affect contrast? |
Directly related. |
| What are two types of motion? |
Involuntary and voluntary. |
| Give an example of involuntary motion. |
pain, breathing, chills, spasms |
| What is the typical range for O.D? |
0.25 to 2.5 |
| How does SID affect density? |
By a factor of 4 (inversely). |
| What are the seven types of radiologic tissue types. |
metal, enamel, bone, muscle, fluids, fat and air/gas |
| Give an example of voluntary motion. |
nervousness, discomfort, fear, excitability |
| Define density. |
The overall blackness on the image. Also described as the amount of black metallic silver on a film. |
| What is fog? |
Unwanted density on the film. |
| The total quantity of x rays produced in an x ray beam is determined by the _____. |
mAs |
| The distance between the x ray tube and the film is? |
Source to image distance (SID) |
| Low radiographic contrast is called? |
long scale contrast |
| Two factors that directly control the amount of x rays emitted by the tube are? |
ma and time |
| The shorter the SID, the __________ the intensity of the xray beam? |
greater |
| Radiographic density if produced by? |
The quantity of x rays reaching the image receptor. |
| Scattered radiation has what effect on radiographic contrast? |
It decreases it. |
| Describe the relationship between filtration and density. |
Inversely related. |
| descibe the relationship between collimation and density |
inversely related |
| Describe the relationship between thickness and density. |
Inversely related |
| Describe the relationship between grid ratio and density. |
Inversely related. |
| Describe the relationship between thickness and contrast. |
Inversely related. |
| Describe the relationship between processing time and contrast |
Inversely related. |
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