Final - Part 3 Flashcards
What is DQE?
Detective Quantum Efficiencies - Measure of sensitivity & accuracy of conversion data. Ratio of squared output SNR to the squared input SNR of the imaging detector.
What is MTF?
Modulation Transfer Function - Measure of the system’s ability to display the contrast of anatomic objects varying in size & spatial resolution.
Spatial frequency filtering is used to sharpen, smooth, blur, reduce noise, or pull out elements of interest.
High pass filtering or ___ averages pixel signals & removes low-frequency signals to produce a sharper image w/ higher contrast.
Low pass filtering or ___ averages pixel frequency to blur the image, reduces noise, & brightness but decreases detail.
Blurring or ___ subtracts a low pass filtered image from the original image producing a subtracted & sharper image.
___ improves image quality by removing artifacts caused by the variation in pixel-to-pixel sensitivity.
___ assigns a value to a dead pixel based on the value of adjacent pixels.
edge enhancement
smoothing
unsharp masking
flat fielding
dead pixel correction
_____ allows several histograms to be “stacked” for a particular exam, usually in dedicated units.
Histogram Equalization
____ allows the tech to combine multiple images of body parts into one seamless image to compensate for length.
Image Stitching
Flat panel detectors are direct or indirect conversion systems.
In the direct conversion system, the x-ray photons strike a photoconductor made of __ which creates an electric charge.
The charge is then transmitted through the ___ to the computer.
In an indirect system, the x-ray photons strike a scintillator made of _ which emits light.
The light then strikes a photodiode or photodetector made of _ which converts light to an electric charge.
The charge is then transmitted through the TFT to the computer.
amorphous selenium
TFT
cesium iodide
amorphous silicon
Factors that affect phosphor efficiency & speed include: ___ which is the ability of the phosphor to convert the energy into trapped electrons, ___ which is the ability of the phosphor to perceive & interact w/ x-ray photons, and ____ which is the measure of how effective the phosphor is at absorbing x-ray photons.
conversion efficiency
DQE
absorption efficiency
Brightness of a digital image is controlled by __.
The contrast or grayscale of an image is controlled by __.
window level
window width
Image noise or quantum mottle is caused by ___ photons.
starvation
SNR is the difference between those x-rays that are transmitted to the IR ____ & those that are absorbed photoelectrically or are scattered ___.
signal
noise
An image w/ high SNR has ___ quality,
___ contrast, &
___ contrast resolution.
higher
higher
higher
Decreasing kVp leads to a higher SNR, but may increase ___.
Pt dose.
The exposure indicators represent how much radiation the IP has received. The EI is manufacturer dependent. Fuji, Konica, & Phillips use __ which is __ related to exposure. The acceptable range is __ to __.
Carestream (Kodak) uses ___ which is ___ related to exposure. The acceptable range is __ to __.
Afga uses __ which is ___ related to exposure. The acceptable range is __ to __.
S#/Sensitivity
inversely
150 - 250
Exposure index (Ei)
directly
1800-2200
Long median exposure
directly
1.8-2.2
Compared to conventional (film-screen) radiography, digital systems have:
___ contrast resolution,
___ spatial resolution,
___ DQE,
___ pt dose, &
___ exposure range.
increased
decreased
increased
decreased
wider
An overall visual assessment of a display device or monitor should be completed ___. Other quality control tests for distortion, reflection, luminance, & resolution should be completed __ or ___.
daily
monthly
quarterly
