RAD106
What happens when you increase or decrease the field of view (FOV)?
increase FOV = decreased collimation = decreased spatial resolution
decrease FOV = increased collimation = increased spatial resolution
What does a CCD do?
reduces the size of visible light images, transfers the image to one or more CCD's, light is then converted to an electrical signal.
How do you erase CR plates?
Expose it to intense light.
What is the name for laser pattern?
Raster pattern.
Does a smaller image palte have better spatial resolution?
Yes, because the pixels are smaller.
What are the steps for image acquisition used in CR?
1. exposure
2. image focused laser light scanning (readout)
3. information goes to photomultiplier
4. analog-to-digital conversion
5. image processing and enhancement
6. sent to review station.
What do CMOS do?
True or false: the Laser creates and amplifies narrow wide soft beams of divergent light?
What do we call the motion for an imaging palte?
Oscillation motion, the name of a moving grid.
How does matrix size and number of pixels influence resolution?
More pixels, the better the resolution.
The larger the matrix, the better the resolution.
What is a Look-up table?
Reference histogram of luminance values derived during image acquisition based on anatomy selection.
What happens when an incorrect body part is selected in CR?
can open up possibility of image misrepresentation or misinterpretation because we are using the wrong histogram.
What is, done before the exposure is taken, helps reduce the amount of radiation exposure to the patient?
Collimation.
What are some factors that affect resolution?
1. pixel size
2. phosphor thickness
3. number of pixels
4. matrix size.
Why is grid use so important with CR?
1.to decrease scatter radiation.
2. sensitive to low energy.
What are CMOS?
Complementary metal oxide semiconductors. Use a scintillator that when struck with x-ray photons convert the x-rays into light photons and stores them in capacitors.
In CR, what is the phosphor layer made of?
Barium fluorohalide
What is, a post processing technique that blacks out the white collimation borders, essentially eliminating veil glare?
Shuttering.
How will an image appear if there is insufficient light translation?
Grainy appearance because of insufficient light produced in imaging plate.
What is, number of lead strips/grid lines per inch?
Grid frequency.
What are the differences between CCD's and CMOS?
CMOS:
CCD:
- Bigger, less expensive
- CCDs use as much as 100 times the power.
- widely available at low cost.
Is the signal ever completely lost in phosphor plates?
trapped signal will remain for hours, days. deterioration begins immediately. in fact, the trapped signal is never completely lost.
What is the Fuji S-number?
Another name for exposure index.
In CR, how will spatial resolution be affected if an imaging plate much larger than the part is being used?
spatial resolution won't be as good compared to if a smaller plate was used.
What is a Photoconductor?
Absorbs x-rays and results in electrical charge.