Term
| Please list the Factors contributing to Scatter, as given in the notes. |
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Definition
a. kVp used
b. Tissue Type & Thickness
c. Field size |
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Term
| How does kVp contribute to Scatter X-rays? |
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Definition
It controls the balance between scatter and absorption
a. Mid to high range kVp = less absorption
b. This leaves more photons to scatter and “fog” the film |
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Term
| How does Tissue Type contribute to Scatter X-rays? |
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Definition
a. Fat & water based tissue produce more scatter
b. % of compton’s interactions increases causing more fogging of the film leading to a loss of contrast and detail |
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Term
| How does Field Size contribute to Scatter X-rays? |
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Definition
| The larger the field the more area exposed to primary beam = more scatter |
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Term
| Please list the 5 methods of Contrast Improvement by Scatter Control, as given in the notes |
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Definition
a. Optimum kVp
b. Field size control – beam limiters
c. Scatter-absorbing grids
d. Air-gap technique
e. Recumbent radiography & tissue compression devices |
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Term
| What does Optimum kVp mean as given in the notes? |
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Definition
a. Maximum kVp that will consistently produce and image with acceptable contrast
b. Higher kVp is balance with lower mAs to reduce patient dose
c. Small parts & cervical spine = 70 kVp
d. Larger parts = 80 – 90 kVp |
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Term
| Spot filming requires an increase in which primary factor setting as given in the notes? |
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Definition
| An increase in mAs is needed |
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Term
| Please list the three types of Grids used in Scatter Control, as given in the notes. |
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Definition
a. Linear
b. Cross grid (Crosshatched)
c. Focused Grid |
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Term
| Please explain the 2 types of Grids Chiropractors use related to ratio and lines per inch, as given in the notes. |
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Definition
a. Stationary grid in a grid cabinet
i. 10:1 or 12:1 grid ratio
ii. 85 lead lines per inch
b. Moving grid in a bucky
i. 10:1 or 12:1 grid ratio
ii. 85 lead lines per inch |
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Term
| Stationary grid and moving grid both use a _______ to _______ grid ratio |
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Definition
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Term
| Stationary grid and moving grid both use a grid ratio of ________ lead lines per inch |
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Definition
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Term
| What is the clinical benefit of using the Air Gap Technique in trying to control Scatter, as given in the notes? |
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Definition
a. Increasing the object to film distance causes less scatter to reach the film.
b. It also magnification and distortion, which reduce the benefits clinically unless magnification is desired. |
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Term
| At what point in history did the use of glass plates for X-ray stop and what was the reason as given in the notes? |
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Definition
| World War I, due to a high quality glass shortage |
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Term
| What is the Silver Halides composition of X-ray Film as given in the notes? |
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Definition
a. Silver Bromide (AgBr) – 90% - 99%
b. Silver Iodide (Agl) – 1% - 10%
c. The silver halides are in the form of crystals |
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Term
| What is the percentage of Silver Bromide (AgBr)in the composition of x-ray film? |
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Definition
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Term
| What is the percentage of Silver Iodine (Agl) in composition of x-ray film? |
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Definition
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Term
| What is the purpose of the “Supercoat” over the film emulsion as given in the notes? |
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Definition
| It is a gelatinous covering that protects the emulsion from scratching, pressure, and contamination |
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Term
| Please explain Latent Image in regard to X-ray Film Processing, as given in the notes. |
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Definition
| Is the undetectable change induced in the silver halide crystals (metallic silver) |
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Term
| Please explain Manifest Image in regard to X-ray Film Processing, as given in the notes. |
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Definition
| When the film is chemically processed, the latent image becomes the “Manifest Image.” (Elemental silver) |
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Term
| What are the three types of Film as given in the notes? |
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Definition
a. Screen type film
b. Direct exposure film
c. Duplicating film |
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Term
| Which is the most commonly used types of film for medical imaging as given in the notes? |
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Definition
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Term
| What are the three types of Screen Film as given in the notes? |
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Definition
a. Blue sensitive
b. Green sensitive
c. UV sensitive |
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Term
| What are the 4 important considerations in selecting the proper screen-type film for your office use as given in the notes? |
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Definition
a. Detector contrast
b. Film speed
c. Latitude
d. Spectral Response |
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Term
| Please explain the functions of Intensifying Screens, as given in the notes. |
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Definition
| Converts the energy of X-rays into visible light allowing 90-95% of the films exposure to be from visible light emitted by the screen; reducing the patient dose. |
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Term
| What is the meaning of Optical Density as given in the notes? |
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Definition
| Refers to the overall blackening (darkness) of the finished radiograph. |
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Term
| What is the relationship to High vs. Low Optical Density and the film exposure, as given in the notes? |
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Definition
a. High optical density will produce a film that is too dark = overexposed
b. Low optical density will produce a film that is too light = under exposed |
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Term
| Low optical density will produce a film that is |
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Definition
| too light = under exposed |
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Term
| High optical density will produce a film that is |
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Definition
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Term
| What is the test for determining adequate density on the film, as given in the notes? |
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Definition
| Hold the film up to a view box, making sure your fingers are in the area outside the body part (air exposed area). You should not be able to see your fingers through the blackness |
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Term
| What is the primary controlling factor affecting Density, as given in the notes? |
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Definition
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Term
| Please explain the effect of increasing or decreasing the mAs on Optical Density, as given in the notes. |
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Definition
a. Increase mAs = increase optical density = increase darkness (more x-rays)
b. Decrease mAs = decrease optical density = decrease darkness (less x-rays) |
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Term
| Decrease mAs = decrease optical density |
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Definition
| decrease darkness (less x-rays) |
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Term
| Increase mAs = increase optical density |
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Definition
| increase darkness (more x-rays) |
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Term
| Explain the mAs 50% rule regarding darkening or lightening the film density, as given in the notes. |
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Definition
| Adjust mAs by a factor of 2 if there is a density error on the film. |
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Term
| mAs 50% rule If minimum change is needed: |
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Definition
1. Double mAs = darker
2. Half mAs = lighter |
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Term
| mAs 50% rule If greater change is needed: |
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Definition
| Multiply or divide by 4, 8, etc |
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Term
| mAs 50% rule a Visible change requires _____% change |
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Definition
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Term
| How does kVp affect optical density as given in the notes? |
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Definition
a. Increase kVp = increase density
b. Decrease kVp = decrease density |
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Term
| Why is it recommended to change the mAs instead of the kVp when attempting to change the Density on the film, as given in the notes? |
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Definition
a. Changing kVp does not have a proportional effect on denstity
b. Changing mAs does have a proportional effect on density |
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Term
| What is the kVp 15% rule and how does it work regarding density as given in the notes? |
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Definition
a. A 15% increase in kVp doubles the density (similar to 50% mAs rule)
b. A 15% decrease in kVp decreases density by ½ (similar to 50% mAs rule) |
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Term
| How does increasing or decreasing the SID (FFD) affect the Density on the film, as given in the notes? |
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Definition
a. Increasing the SID = a decrease in density
b. Decrease in SID = increase in density
***the intensity of the x-ray beam is inversely proportionate to the square of the distance from the source*** |
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