UNIT 2 IMPORTANT STUFF Flashcards
Primary Radiation
All radiation produced directly from the target in an x-ray tube
Secondary Radiation
Created when primary beam interacts with matter
Scatter radiation
X-rays that travel in different directions after exiting the patient body
Remnant radiation
What remains of the primary beam after it has been attenuated by the matter(through the body before going onto the image receptor)
3 basic types of beam restriction devices
Aperture diaphragm, cones, collimators
Aperture diaphragm
Flat sheet of metal, usually lead, with a hole cut in the center and attached to the X-ray tube
Cones and Cylinders
Circular aperture diaphragms with metal extensions
Cone
Has an extension that flares or diverges with upper diameter smaller than the bottoms flared end
Cylinder
Not flared, has same diameter at the bottom of the extension as it has on the top
A grid created with the lead and interspace strips running parallel to one another. If an imaginary line were to extend the lead strips beyond the grid, they would never intersect.
Parallel grid
A grid in which the grid sectors are parallel in the center, but are angled progressively more out towards the peripheral edges. If imaginary lines were to extend the lead strips beyond the grid, they would intersect at a Focal Point.
Focused grid
The range of source-image distances (SID) at which the grid will not absorb significant amounts of primary radiation.
Focal Range
Two linear grids placed on top of one another so that the lead strips form a criss-cross pattern.
Cross-hatched grid
A grid with lead strips running in only one direction
Linear grid
Occurs when the tube is angled across the long axis of the grid strips. It results in a reduction in IR exposure over the entire Image Receptor.
Off-level grid error
Occurs when the Central ray is off-center to the center of a focused grid. The result is a reduction in IR exposure over the entire Image Receptor.
Off-center grid error
When a grid is used at a distance other than that specified as the focal range. The result is a reduction in IR exposure in the peripheral edges of the IR and normal exposure in the center.
Off-focus grid error
When a grid is placed upside down. The result is a reduction in IR exposure in the peripheral edges of the IR and normal exposure in the center.
Upside-down grid error
High frequency grids vs Low frequency grids
Using grids with higher frequency and higher grid ratios cleans up more scatter radiation which increases contrast more than low grid ratios and low frequency grids
Dfferential absorption
- Makes diagnostic X-ray work
- Absorbed at different rates
Depends on:
* Patient’s tissue
* Thickness
* Density
* Atomic number
In thicker tissue, dense tissue, or tissue possessing a high atomic number, more x-rays are absorbed in the tissue, a lower percentage exits the patient to expose the film.
On an x-ray how do gas, soft tissue, and bone show up?
Gas: black
Soft tissue: gray
Bone: white
The force that holds electrons in orbit around the nucleus. It is also the minimum amount of energy required to remove an electron from its orbit.
Electron binding energy
The distance from the face of the grid to the point of convergence of the lead strips
Grid radius
