8. Characteristics of diagnostic imaging part 1 Flashcards
Define analog:
Required for viewing, needs to be in analog for us to view it in digital radiography
Define digital, and how pixels give us our image:
-A matrix of pixels represented by numerical values
-After exposure, each number captured by the pixel gives a certain value that will correspond to a certain brightness
Define digital imaging;
An image constructed from numerical data
What are the pixels represented by? What do individual pixels contain?
Represented by a numerical value and contains a series of bits
What are the 2 types of DDR?
- Flat panel direct capture detectors
- Charged coupled devices
What are the two ways that images can be captured in flat panel direct capture detectors?
- Indirect acquisition
- Direct acquisition
Define Indirect acquisition:
- Scintillator: Converts x-rays into light. It is made of Cesium iodide or gadolinium (cesium iodide can be formed into lines)
- Photodiode: Amorphous silicon. Converts light into electric charge
- TFT: Composed of an array of DELs. Each DEL is comprised of pixels. (Storage capacitor and switch located within pixel to release charge in binary numbers
Could also used a charged coupled device
Define direct acquisition:
- Amorphous selenium: Uses high voltage run through to collect the x-ray charge and turn directly into electrical signal
- TFT: Composed of an array of DELs. Each DEL is comprised of pixels. (Storage capacitor and switch located within pixel to release charge in binary numbers
What are the pros of CR?
-Portable (bucky/tabletop, diff room)
-Can adapt to existing radiography equipment
What do the 0 and 1’s represent in binary system?
Either selecting or not selecting something
How is pixel depth (not physical) measured?
-By the number of bits. The more bits associated with the pixel, the more depth
Why do we need depth?
-Without ‘depth’ we would not be able to represent various brightness levels/pixel
How many values can one pixel represent?
-Pixel can only represent one value at a time
What do the bits represent?
-Represent each pixel brightness
How much is 8 bits?
- 8 bits=1 byte
In binary notation, what is the decimal number 3 equal to?
2^1+2^0
