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Physics Review 4-6
Physics Ch 4, 5, 6
| Question | Answer |
|---|---|
| Evaluating radiographic quality requires the radiographer to assess the image for both: | * visibility of recorded detail (photographic properties) * sharpness of recorded detail (geometric properties) |
| photographic properties of recorded detail that are determined by the extent to which the structural components of the anatomic area of interest can be seen on the recorded image | visibility of recorded detail |
| Visibility of the recorded detail is achieved by the proper balance of ________ and _________. | radiographic density and radiographic contrast |
| the amount of overall blackness produced on the image after processing | radiographic density |
| Factors that directly affect density are identified as: | controlling factors |
| Factors that indirectly affect density are identified as: | influencing factors |
| Controlling factors for density: | * mA * exposure time |
| mA and exposure time are ________ proportional to quantity of x-rays produced | directly |
| mA & exposure time have an _________ relationship when maintaining the same mAs | inverse (reciprocity law) |
| A change in mAs results in a ________ change in radiographic density. | direct |
| What is the primary responsibility of a radiographer? | to evaluate radiographic images to determine whether sufficient information exists for a diagnosis |
| Radiographic quality is the combination of ________ and ________. | visibility and sharpness of recorded detail |
| determined by the extent to which the structural components of the anatomic area of interest can be seen on the recorded image | photographic properties |
| Factors that affect the visibility of the recorded detail is achieved by the proper balance of ________ and ________. | density and contrast |
| photographic quality when visibility of recorded detail is maximized | optimal |
| photographic quality when visibility of recorded detail is adequate or acceptable | diagnostic |
| photographic quality when recorded detail is not adequately visualized & the image must be repeated | unacceptable |
| Visibility of recorded detail is achieved by the proper balance of ________ and ________. | density and contrast |
| the amount of overall blackness produced on the image after processing | radiographic density |
| A radiograph that is too light has ________ density. | insufficient |
| A radiograph that is too dark has ________ density, and the anatomic part cannot be well visualized. | excessive |
| True or False: Knowledge about the factors that affect the density on a radiograph is critical to developing effective problem-solving skills of a radiographer. | True |
| Factors that directly affect something are called ________ factors. | controlling |
| Factors that indirectly affect something are called ________ factors. | influencing |
| has a primary effect on the amount of density | quantity of radiation reaching the IR |
| What happens to density when you increase the mAs? | the density increases |
| What happens to density when you decrease the mAs? | the density decreases |
| mAs can be doubled by: | doubling the mA or doubling the exposure time |
| Shape distortions appear in 2 different ways: | 1. Foreshortening 2. Elongation |
| How should you adjust the technical factors to prevent blooming? | Increase kVp and Decrease mAs |
| To adapt an adult technique to a pedi technique for a 6 to 12 yr old: | Decrease mAs by 50% |
| How much should you adjust the mAs to make any density change? | by 30% |
| increasing kVp by 15% will have the same effect on radiographic density as doubling the mAs; a 15% decrease will have the same effect as halving the mAs...what rule is this? | The 15% Rule |
| A radiograph of the pelvis is produced using 25 mAs at 70 kVp. What kVp would be needed to double the exposure? | 81 kVp (15% of 70 kVp + 70 kVp = 80.5 or 80 kVp) |
| Given an original technique of 30mAs & 80kVp, provide 2 possible ways of doubling the density. | 1. Double your mAs or: 2. increase the kVp by 15% (80kVp x 1.15 = 92 kVp) |
| the relationship between distance & x-ray beam intensity is best described by | The Inverse Square Law |
| States that the intensity of the x-ray beam is inversely proportional to the square of the distance from the source | The Inverse Square Law |
| What are the standard distances for most radiographic procedures? | 40', 48" or 72" |
| a device placed between the patient & the IR to absorb scatter radiation exiting the patient | Grid |
| Film screen systems are classified by relative speed (RS) factor. What is the relative speed (RS) range for film screen systems? | 50 to 800 RS |
| What relative speed (RS) film screen would you use to radiograph an extremity? | 100 RS |
| What is a routine high-speed film screen? | 400 RS |
| What 3 things make the effect of collimation on the radiographic density more visible? | 1. when imaging large anatomic areas 2. performing exams without a grid 3. using a high kVp |
| What type of relationship does film screen speed have with density? | direct relationship |
| What type of relationship does collimation have with density? | inverse relationship |
| What does a thick anatomic part do to radiographic density? | decreases it |
| What does a thin anatomic part do to radiographic density? | increases it |
| How much should the radiographer adjust the mAs for every change in part thickness of 4cm? | by a factor of 2 |
| The visibility of the anode heel effect on a radiographic image depends on 3 things...what are they? | 1. the SID used 2. the x-ray beam field size 3. the anatomic area of interest |
| The anode heel affect is more visible when... | you have a short SID & a large x-ray field size |
| states that the density produced on the radiograph will be equal for any combination of mA and exposure time, as long as the product of mAs is equal. | Reciprocity Law |
| When can reciprocity failure occur? | if using intensifying screens & extreme exposure times ( >10s or <10ms) |
| Do 3-phase units require higher or lower technique settings to produce a comparable image compared to a single phase unit? | Lower technique settings |
| When using compensating filters, should the mAs be increased or decreased in order to maintain the overall radiographic density? | increased |
| Processing of the film after exposure to radiation has a major effect on: | density & contrast |
| What conditions during film processing can adversely affect the radiographic density or contrast? | processor temperature, chemistry, or film transport |
| True or False: Exposure factor's effects on the intensity of radiation holds true for digital imaging. | True |
| True or False: The relationship between mAs and density is not the same for digital imaging as it is for film-screen imaging. | True |
| What percentage of exposure errors can adequately be adjusted during digital image processing? | 50% |
| What describes the concept of density as it is displayed on a soft-copy monitor for digital images? | brightness |
| the degree of difference between adjacent densities | contrast |
| an image that has sufficient density but no differences in densities | a homogeneous object |
| radiographic contrast is the combined result of 2 categories: | film contrast & subject contrast |
| refers to the contrast that is a result of the inherent properties manufactured into the type of film and how it is radiographed, along w/the processing conditions | film contrast |
| contrast that is a result of the absorption characteristics of the anatomic tissue radiographed and the level of kVp used | subject contrast |
| a radiograph with few densities but great differences among them | High contrast (short-scale) |
| a radiograph with a large number of densities but little differences among them | Low contrast (long-scale) |
| controlling factor for contrast | kVp |
| influencing factors affecting contrast: | grids, collimation, OID, anatomic part, contrast media, processing |
| unwanted density on a radiograph | fog |
Created by:
kkant
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