| Radiology exposure |
answers |
| 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. |
mr. charles11
