How does scatter radiation happen?
In general, scatter radiation is Compton scatter radiation. This radiation usually occurs when x-ray interacts with matter. It occurs in medium and high energy range.
When do you recommend the use of an x-ray grid?
An x-ray grid is recommended when x-raying objects that are 10cm thick or greater. When thick objects are x-rayed, they create scattered radiation which contributes to fogging on the image.
How is scatter radiation removed?
X-ray grids are presently constructed with lead strips to absorb scatter radiation and an interspacer (most commonly aluminum) to allow the primary radiation to pass to the film or receptor.
What are high ratio grids recommended for high kVp?
When tube voltage increases, the x-ray energy increases. When x-ray energy increases, scattered radiation increases. To effectively remove the scatter a higher ratio grid is recommended.
Could you explain how to use the grid in radiography?
Traditionally, the grid is placed in front of image receptor or film cassette. To eliminate visible lines in an image the grid is installed on a reciprocating (moving) bucky. However, with Digital Radiography (DR) and Computed Radiography (CR), grids are being used without moving buckys. To eliminate grid lines in the image, a high line frequency is needed.
What is the construction of an x-ray grid?
The grid consists of aluminum interspacers and lead absorbers and is covered with an aluminum or CFRP cover.
What grid size is right for me?
It’s important to make sure the grid is larger than the Field of View (FOV). To prevent cutoff. Field of View is determined by the target angle of the tube.
What is the selection criterion for grid ratio?
When selecting the grid ratio, we used to consider x-ray source, especially kVp. The reason is that the occurrence of scatter radiation is related to x-ray energy.
What is the normal line density of grids in conventional radiography?
The grid density used traditionally is 80 lp/inch, 103 lp/inch, and 110 lp/inch. The common ratios are 8:1 and 10:1. For mammography, grids of 31-41 lp/cm are presently being used.