Define the following terms: Luminescence, Fluorescence, Phosphorescence
- Luminescence is when materials absorb energy and light
- Fluorescence is fast light emission (ms)
- Phosphorescence is slow light emission (lag)
Name the 5 components of an image intensifier (II) and their functions
- Input phosphor (IP) (generates light)
- Photocathode (light from IP energises crystals)
- Electron focussing lenses (controls directional flow of electrons)
- Anode (electrons are attracted by potential and focussed onto the OP)
- Output phosphor (OP) (converts electron strikes into light photons)
What are the structural advantages of Caesium Iodide (CsI)?
- Vacuum window
- Photocathode
- CsI needles
- X-ray and light production
- Electrons
What is Pincushion Distortion?
Projecting an image from curved surface
Edge of input phosphor in Intensifier is further away
More magnification
Less Brightness
Describe the ‘Vignetting’ image artefact.
Decrease in image brightness at lateral portions of image
Light scatter within active image area
Increased intensity of a uniformly exposed image
List 6 features of the fluoroscopy imaging chain.
- Monitor
- Vídeo camera
- Optical coupling
- II
- Grid
- Patient
- Table
- Filtration
- Collimator
- X-ray tube
- X-ray generator
True or False?
With FP magnification, digitally enlarging the display causes complete loss of resolution.
False.
It causes only slight loss of resolution
List one advantage and disadvantage of the Multifield II Magnification technique
+Uses electronic magnification
+Produces large image production on the output phosphor
- Has a decreased FOV
- Increases patient dose because it uses a high mAs
Define Detective Quantum Efficiency.
The efficiency of a detector in converting incident X-ray energy into an image signal
What are some applications of Fluoroscopy?
Barium studies
ERCP
HSG
Angiographic studies
What is the difference between Dual Focus and Trifocus?
Dual focus has 2 different FOVs whereas trifocus has 3 different input phosphor diameters.
What is ‘S Distortion’?
When the external electromagnetic sources affect the electron paths at the periphery of the image more than at the centre.
Warping of image along an S-shaped axis
How does a ‘Veiling glare’ occur?
Light reflection from window of OP
Reduces contrast
Degrades object contrast at output phosphor of II
In terms of resolution, Fluoroscopy…
- ..Doesn’t require high-res performance
- ..Uses flat-panel detectors to limit resolution
- ..Is performed with Image Intensifiers
- ..4 pixels are burned into 1 for a larger FOV
Where does the ‘Veiling Glare’ artefact commonly occur?
Inside the II between the Photocathode and the Anode.
Flat Panel Detectors.
Similar to DDR systems
Replace II and TV camera
Feed image info directly into processor
Rows of pixels (in the AMA) are switched continuously
Define the following;
Read-out Rate
Pixel Element Size
Pixel Fill Factor
Rate at which flat panel array is sampled and displayed
The smaller the pixels, the higher the spatial resolution
Percentage of the area of any pixel that is actively involved in the conversion of X-rays to image
3 advantages of FPDs
Smaller in volume
Less image distortion
Lighter and more durable
3 disadvantages of FPDs
Low spatial resolution
Defective image elements
Higher costs
Radiation Safety Techniques
Pulsed Fluoro
Single pulse mode
Beam limitation
Last image hold
Movements of II allow distance between patient and image detector to be reduced
