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Unit 3
Image Acquisition and Evaluation
| Question | Answer |
|---|---|
| What is recorded detail? | The clarity, or resolution, in which anatomic structures are represented; sharpness of borders; measured by test pattern pg.298 |
| What is distortion? | The misrepresentation of the actual size or shape of the structure pg.299 |
| How is resolution expressed? | Line pairs per millimeter; one line pair refers to one line and the one space adjacent to it pg. 299 |
| What is visibility of detail? | How well the recorded detail can be seen; excessive density, brightness, or scattered radiation fog impairs detail visibility pg.299 |
| What is contrast resolution? | Anything that effects density/brightness or visibility of detail pg. 300 |
| How does the use of high kV affect the production of scattered radiation fog? | Scattered radiation fog increases |
| As the thickness and density of tissues increase, does scatter increase or decrease? | Increase |
| What happens as grid ratio increases? | The cleanup of scatter increases and contrast improves, contrast scale decreases, patient dose increases |
| What is a grid factor? | The ratio of the total amount of radiation incident on the surface of the grid to the amount of radiation transmitted through the grid pg. 347 |
| What are two types of AECs? | Phototimer and ionization chamber pg. 349 |
| What is signal to noise ratio used to describe? | Contrast resolution; the higher the SNR, the better contrast resolution |
| What is The Detective Quantum Efficiency? | DQE; The ability of receptor material to perceive and interact with x-ray photons |
| What is the most common result of incorrect film storage? | Fog |
| What temp. should film be stored? | 70 degrees F pg. 381 |
| What humidity should film be stored? | 40% to 60% pg. 381 |
| What causes CR graininess? | Underexposure, Incorrect processing algorithm/LUT, excess scattered radiation, inadequate collimation, grid misalignment or cutoff pg. 405 |
| What causes CR resolution to increase? | PSP phosphor size decreasing, laser beam size decreasing, monitor matrix size increasing pg. 406 |
| What causes excessive density on film? | Elevated developer temperature, insufficient dilution of developer pg. 389 |
| What causes inadequate density on film? | Too low developer temp., excessive dilution of developer pg. 389 |
| What causes subject/object unsharpness? | Object shape does not match the shape of x-ray beam, object plane is not parallet with x-ray tube and/or IR, anatomic objects of interest are not in path of CR, anatomic objects are a distance from the IR |
| What terms describe distortion? | Magnification, elongation, and foreshortening pg. 300 |
| How does focal spot size affect detail? | It influences the degree of blur or unsharpness pg. 308 |
| What is involuntary motion? | Peristaltic activity, muscle spasms, and heart action; motion that cannot be controlled pg. 309 |
| What is the active ingredient in intensifying screens? | Fluorescent phosphor pg. 311 |
| When is quantum mottle more likely to occur? | When using fast screens with low mAs and high kV factors pg. 313 |
| What is the definition of the reciprocity law? | Any combination of mA and exposure time that produces a particular mAs, will produce identical image density pg. 317 |
| Doubling the mAs will do what to the density? | Double pg. 318 |
| What percentage of change must occur to mAs in order for a recognizable change in density? | 30% change pg. 318 |
| What is the inverse square law formula? | I1/I2=D squared 2/D squared 1 pg. 319 |
| What is the density maintenance formula? | mAs1/mAs2=D squared 1/D squared 2 pg. 319 |
Created by:
cfdishon
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