Term
| What is the definition of Radiographic Contrast, as given in the notes? |
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Definition
| Is the variation in densities on the radiograph |
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Term
| Explain Long Scale Contrast as related to Kvp as given in the notes. |
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Definition
i. Gradual changes in density
ii. The range between the densities is wide & large in number
iii. Desirable in medical radiology
iv. Usually results from a high kVp technique |
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Term
| Explain Short Scale Contrast as related to kVp as given in the notes. |
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Definition
i. More abrupt changes in densities
ii. The range of densities is small & few in number
iii. Usually results from a low kVp |
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Term
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Definition
| The inherent ability of the film to record high and low contrast as determined by the film manufacturer |
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Term
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Definition
| absorption characteristics of the part x-rayed and the kVp used. (attenuation of the beam) |
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Term
| What is the primary controlling factor affecting Contrast, as given in the notes? |
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Definition
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Term
| How does the use of a high kVp affect the film Contrast, as given in the notes? |
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Definition
a. creates more densities but with fewer differences between them
b. Long scale = low contrast
c. Increasing kVp:
i. Increases the amount of scatter
ii. Increases fog
iii. Decreases contrast |
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Term
| How does the use of low kVp affect the film Contrast, as given in the notes? |
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Definition
a. creates fewer densities but with greater differences
b. Short scale = high contrast
c. Decreasing kVp |
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Term
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Definition
i. Decreases scatter
ii. Decreases fog
iii. Increases contrast |
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Term
| Other than the kVp affect on Contrast how do most of the other Influences Factors affect Contrast, as given in the notes? |
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Definition
| Most influencing factors affect contrast by controlling the amount of scatter that reaches the film |
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Term
| How does the use of a grid “properly applied” affect the film Contrast, as given in the notes? |
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Definition
a. by absorbing much of the scatter that exits the patient before it reaches the film
b. Properly applied: it increases contrast |
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Term
| How does the Air Gap Technique affect Contrast, as given in the notes? |
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Definition
decreased scatter reaching the film
i. Increases contrast
ii. But causes magnification |
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Term
| Please define “Penumbra” as given in the notes. |
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Definition
a. Geometric unsharpness along the edges of the film. It is greatest on the cathode side of the tube.
b. It causes the border of the film to appear fuzzy |
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Term
| What are the 4 things listed that affect Penumbra, as given in the notes? |
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Definition
a. Magnification distortion
b. Projectional distortion
c. Focal spot distortion
d. Motion during exposure |
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Term
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Definition
| Source to Image-receptor Distance |
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Term
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Definition
| Object to Image-receptor Distance |
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Term
| A larger focal spot size = |
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Definition
| decrease in sharpness = decreased recorded detail |
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Term
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Definition
| increase in sharpness = increased recorded detail |
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Term
| Please explain how SID or FFD affects “Unsharpness” or Sharpness” of the recorded detail of the film image as given in the notes. |
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Definition
| The longest practical Focal-spot-to-film distance FFD (SID) produces the least amount of magnification distortion resulting in improved recorded detail |
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Term
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Definition
1. Increases sharpness
2. Increases recorded detail |
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Term
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Definition
1. Decreases sharpness
2. Decreases recorded detail |
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Term
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Definition
1. Decreases sharpness
2. Decreases recorded detail
3. increases magnification |
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Term
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Definition
1. Increases sharpness
2. Increases recorded detail
3. decreases magnification |
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Term
| How does Motion affect Recorded Detail, as given in the notes? |
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Definition
a. Motion of the tube, patient/body part or image receptor decreases recorded detail
b. Blur – is unsharpness due to patient motion |
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Term
| Explain how OID or OFD causes image size distortion as given in the notes. |
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Definition
a. Increase in OID = increase in magnification = increased distortion
b. Decrease in OID = decrease in magnification = decreased distortion |
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Term
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Definition
| increase in magnification = increased distortion |
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Term
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Definition
| decrease in magnification = decreased distortion |
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Term
| Explain how SID or FFD causes image size distortion as given in the notes. |
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Definition
a. Increase in SID = decrease in magnification = decreased distortion
b. Decrease in SID = increase in magnification = increased distortion |
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Term
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Definition
| decrease in magnification = decreased distortion |
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Term
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Definition
| increase in magnification = increased distortion |
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Term
| What are the two forms of Distortion of Shape, as given in the notes? |
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Definition
a. Elongation
b. Foreshortening |
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Term
| What is are the components that are combined to produce a diagnostic quality film at a given FFD, as given in the notes? |
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Definition
| A combination of mA, time, & kVp for a given FFD (SID) is used to produce a diagnostic quality film |
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Term
| What is the KEY to consistently & successfully applying technique to X-ray procedures, as given in the notes? |
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Definition
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Term
| Please explain how Latitude & kVp are related to exposure of the film, as given in the notes. |
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Definition
a. Latitude (mAs range) decreases as kVp decreases
b. Latitude & contrast are inversely proportional |
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Term
| At low kVp the mAs must be |
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Definition
| much more accurate (narrow latitude exposure) |
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Term
| At high kVp the mAs has a |
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Definition
| greater range of usability (wide latitude exposure)- Results in less repeat films |
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Term
| What are the 3 ways to apply X-ray Technique as given in the notes? |
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Definition
a. Fixed (optimum) kVp
b. Variable kVp
c. Variable kVp within an optimum range |
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Term
| What is a Fixed Optimum kVp Technique as given in the notes? |
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Definition
a. The highest kVp that will result in the lowest patient dose while consistently producing images with acceptable contrast (visible detail)
b. Optimum is subject to each clinician
c. A single kVp is set to insure adequate penetration of a wide range of patients thicknesses |
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Term
| Please list the three disadvantages to a ‘Fixed (Optimum) kVp’ X-ray technique, as given in the notes. |
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Definition
a. More scatter (higher kVp)
b. Lower contrast
c. Small changes in mAs may not be simple |
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Term
| What is the Variable kVp Technique, as given in the notes? |
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Definition
a. Accurate measurement with calipers is a must
b. The mAs is set per body part & the kVp is varied |
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Term
| What is the Rule of Thumb regarding the Variable kVp Technique, as given in the notes? |
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Definition
| kVp = 2X the cm thickness of body part + 30 |
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Term
| regarding the Variable kVp Technique: its ___ for lumbar |
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Definition
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Term
| regarding the Variable kVp Technique: ___ for cervical & thoracic |
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Definition
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Term
| regarding the Variable kVp Technique: ___ for extremities |
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Definition
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Term
| regarding the Variable kVp Technique: Best used in the _____ kVp range for the spine |
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Definition
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Term
| Please list the disadvantages to the Variable kVp technique, as given in the notes? |
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Definition
a. Contrast may be too high (less grey scale)
b. Increased patient dose
c. Greater tube wear
d. Longer exposure times – more motion potential
e. Narrow latitude (mAs range)
f. Less consistency between exposures |
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Term
| Please explain how to calculate the seconds of exposure time when you know the mA & the mAs, as given in the notes. |
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Definition
| The seconds are calculated by dividing the mAs by the mA |
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