DR
What are advantages of digital radiography?
1. transforms analog images into digital images.
2. Allows operator to enhance or manipulate image
3. increased contrast resolution
4. decreased spatial resolution due to pixel size
Describe Cesium iodide/charge coupled device capture technique.
1. Indirect capture technique
2. xrays converted to light
3. xrays converted to electric signal via fiber optics
4. high spatial resolution
5. Used in II
6. No cassette.
Digital Radiography is best described by what three elements?
1. capture
2. coupling
3. collection
a-Se (Amorphous selenium) is a...?
direct DR process by which xrays are converted directly into an electronic signal.
Define sensitivity.
The ability of the CCD to detect and respond to very low levels of visible light.
List the 3 components of a digital radiography imaging system.
1. Capture element, this captures the Xray signal, uses cesium iodide.
2. Coupling element, this transfers the Xray signal, uses fiber optics.
3. Collection element, this collects the Xray signal, uses light.
Describe Cesium iodide/amorphous silicon capture technique.
1. indirect capture technique
2. Xrays converted to light via silicon
3. xrays converted to electric signal
4. no cassette.
The CCD (charge coupled device) has a...?
High sensitivity to xray exposure and a very wide dynamic range.
Define digital radiography.
advanced imaging technology that captures xray images directly into a digital format.
Define dynamic range.
the ability of the CCD to respond to a wide range of light intensity, from very dim to very bright.
List the 4 digital radiograph production/capture techniques.
1. computed radiography (cassette based).
2. scanned projection radiography (CT).
3. Charged coupled device (no cassette).
4. Direct radiography (no cassette).
Describe Amorphous selenium capture technique.
1. Direct radiography.
2. no phosphor involved
3. xrays ionize/charge selenium
4. charge released creates signal
5. signal read by thin film transistor
6. no cassette.
Csl/CCD is an...?
Indirect DR process by which xrays are converted first to light and then to an electronic signal.
Define capture element
the capture element is that in which the xray is captured.
Define amorphous.
When identified as amorphous silicon, the silicon is not yet crystalline but it is a fluid that can be painted onto a supporting device.
Describe scanned projection radiography capture technique.
1. used in CT.
2. Xray beam shaped into a fan by collimators.
3. scatter radiation reduced.
4. increased image contrast.
5. may have use in digital mammography.
Describe capture technique.
1. CR (cassette based)
- photostimulable phosphor
2. Xray excites e-
3. e- relaxes during processing
4. emits signal.
Csl/a-Si is an...?
Indirect Dr process by which xrays are converted first to light and then to an electronic signal.
Define coupling element.
The coupling element is that which transfers the xray generated signal to the collection element,
Describe charge coupled device capture technique.
1. Highly sensitive to radiation and light
- This decreases patient dose
- Similar to 400 screen speed
- Contrast enhanced unrelated to technique
2. Indirect capture technique
3. No Cassette.
Describe collection element.
1. photodiode: light sensitive device
- collects light photons
2. CCD: light sensitive device
- Cesium Iodide (Csl).
3. Thin film transistor: Charge sensitive device
- collects electrons
- gadolinium oxysulfide (GdOS)
Spatial resolution in DR is...?
Pixel limited.
Define the collection element.
The collection element may be a photodiode, a charge coupled device (CCD), or a thin film transistor (TFT)