Capturing Digital Image: DR And CR Flashcards
What type of detector system does DR use?
Flat panel detector built into radiographic room
What are the benefits of DR systems?
- High PACS compatibility
- Increased department efficiency
What does the detector of the DR system consist of?
Detector consists of hundreds of thousands of “dels” detector elements
What type of detector systems does CR use?
Cassette based systems that uses photostimulable phosphors
What does a CR system require for processing?
A plate reader to scan the plate
Which system is considered more efficient DR or CR?
DR
What is the size of detector elements (Dels)?
Approximately 100 microns or 1/10th millimeter
What are the Dels a part of?
Active matrix array (AMA) and Thin film transistor (TFT)
What do the Dels represent?
Numerical values/address, and not a physical pixel
What type of phosphor is used in direct conversion?
Amorphous selenium (a-Se)
What is the basis of a direct conversion system?
X-rays are directly converted to electrical charges
What is the benefit of a Direct conversion system?
Higher spatial resolution
What type of phosphor is used in indirect conversion?
Amorphous silicon (A-Si)
What are the phosphors overlaid with in indirect conversion?
Cesium iodide/gadolinium oxysulfide
What is the basis of a indirect conversion system?
X-rays are converted to light, then to electrical charges
What is the benefit of an indirect conversion system?
Higher DQE - Detective Quantum Efficiency
What is DQE?
Measures the detectors ability to convert x-ray exposure to image
What does a higher DQE mean?
A higher efficiency in converting the exposure and need for lower radiation dose
What is the DQE influenced by?
- Del surface area
- Fill factor
What is the del surface area?
Where the photons land and where they are counted
What is the fill factor?
The amount of radiation that can fall on this surface area
If a surface area is bigger what does that mean for efficiency?
A bigger surface area has a higher efficiency and less radiation dose can be used
What does a higher fill factor provide?
A higher Signal to Noise ratio which increases spatial resolution
What is spatial resolution limited by?
It is limited by the size of the focal spot
