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What is repeat analysis?
A process of cataloging repeat images to determine reason for repeat to eliminate future repeats.
What specific important data can be gained from repeat analysis?
- 1 Equipment and accessory performance.
- 2 Department procedures.
- 3 Skill level of technical staff.
What are the MAIN advantages of lower department repeat rates?
- 1 Improved department efficiency.
- 2 Lower department costs.
- 3 Lower patient doses.
What are the benefits of improved department efficiency?
- Decreased diagnostic procedure times
- Increased customer satisfaction
What are the benefits of lower department costs in digital departments?
- Lower film and processing costs.
- Lower labor and depreciation of equipment costs.
What is the number one reason for repeats in digital departments?
What formula would you use to calculate a causal repeat rate?
Casual repeat rate=# of repeats for a specific case / Total # of repeats * 100
What formula would you use to calculate the total repeat rate for the department?
Total repeat rate=# of repeats images / Total # of views taken * 100
Repeat rates for radiographic procedures should not exceed ____% to ____%.
4 to 6
An artifact is anything on a finished radiograph that is not part of the patient's anatomy.
Name 3 ways that motion artifact can be reduced:
- 1 Short exposure time.
- 2 Immobilization.
- 3 Proper instructions to the patient.
What is quantum mottle? What causes it? And in what types of imaging can it occur?
- Quantum mottle is a blotchy appearance in a radiograph that is caused bu statistical variations in the number of xray photons covering a specific area.
- Usually found with low mAs (Less than 2 mAs).
- Occurs in CR, DR, CT, Fluoro, and Nuc Med.
What are grid lines? How are they caused?
Grid lines are shadows of the lead strips that appear on the resulting image and are caused by grid movement failure, improper grid focusing distance, improper angulation of the central ray, or improper centering.
What is grid cut-off?
- Grid cut-off is a decrease in optical density caused by primary radiation being absorbed by the grid.
- Improper use of grid causes cut-off.
What is moire' effect?
- A zebra pattern artifact usually due to a double set of grid lines.
- Can happen when grid lines are parallel to CR reader scan lines.
List the 4 steps you can use to eliminate moire' effect:
- 1 Ensure grids are moving during exposure.
- 2 Use a grid with a higher grid frequency.
- 3 Use a crosshatch grid or a multi-hole grid.
- 4 Change the orientation of the grid so lines are perpendicular to the CR reader scan lines.
What is heat blur?
Occurs when CR imaging plates are exposed to intense heat before being processed.
What is histogram error?
Improper optical density is applied when the wrong pre-processing histogram is selected.
Why should techs inspect imaging plates periodically?
Because scratches, scuff marks, or cracks can mimic fractures and signs of pneumothorax.
What is phantom image artifact?
This happens when cassettes are not properly erased and data from previous exam interferes with new exam.
Why are CR and DR image receptors more sensitive to scatter radiation?
They are more sensitive to scatter due to lower k-edge values.
What is CR scanner malfunction?
- Skipped scan lines, missing pixels, and distorted images.
- Caused by memory problems, digitization problems, or communication errors.
What are halo artifacts?
- Appears as dark bands at the interfaces of structures that differ widely in brightness levels.
- Ex: Barium and metal
What is true positive?
Image leads to positive diagnosis backed by separate testing.
What is false positive?
Image leads to positive diagnosis but separate testing shows otherwise.
What is true negative?
Image leads to negative diagnosis and is backed by separate testing.
What is false negative?
Image leads to negative diagnosis but separate testing shows otherwise.
What is accuracy?
Accuracy is the percentage or fraction of cases that are diagnosed correctly.
What is sensitivity?
Sensitivity indicates the likelihood of obtaining a positive diagnosis in a patient with the disease.
A sensitive test has a ____ false ____ rate.
Low false negative rate.
What is specificity?
Specificity indicates the likeliness of a patient obtaining a negative diagnosis when no disease is present.
A specific test has a ____ false ____rate.
Low false positive rate.
Describe negative predictive value:
The probability of not having the disease given the negative test.
What is the Law of Reciprocity?
Using different combinations of mA and seconds should result in the same quality image as long as mAs is the same.