Radiographic Grids Overview

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Questions and Answers

What is the primary function of a radiographic grid?

To increase the exposure time needed for imaging

To enhance the brightness of the image

To filter out all scatter radiation completely

To transmit x-rays traveling in a straight line to the image receptor (correct)

What can occur if a radiographic grid is placed backwards?

Grid errors (correct)

Increased image contrast

Reduced patient dose

Distortion of the image

Which material is commonly used for constructing the sections of a radiographic grid?

Glass

Radiopaque material (correct)

Conductive metal

Plastic

How is the grid ratio calculated?

Height of the lead strip divided by the width of the interspace material Signup and view all the answers

What is indicated by a high grid ratio compared to a low grid ratio?

More effective clean-up of scatter radiation Signup and view all the answers

What does the Contrast Improvement Factor measure?

The ratio of radiographic contrast with a grid to that without a grid Signup and view all the answers

What is a consequence of using high-ratio grids during imaging?

Increased patient dose Signup and view all the answers

Who first demonstrated the technique for reducing scatter radiation with grids?

Gustave Bucky Signup and view all the answers

What does the Bucky factor measure?

Patient dose with and without a grid Signup and view all the answers

When should a grid be used according to the guidelines?

Body part is larger than 10cm and contains mainly soft tissue and bone Signup and view all the answers

Which type of grid is used to reduce grid cut-off?

Focused grid Signup and view all the answers

Which type of grid consists of two linear grids superimposed?

Crossed grid Signup and view all the answers

What is a disadvantage of using grids?

Potential for grid lines on the image Signup and view all the answers

Which type of moving grid operates in a circular motion?

Oscillating grid Signup and view all the answers

What is an advantage of using a focused grid compared to a parallel grid?

More effective scatter radiation cleanup Signup and view all the answers

Reciprocating grids are most commonly used for what reason?

They have back and forth movement Signup and view all the answers

Study Notes

Radiographic Grid

Radiographic grids are designed to transmit only x-rays traveling in a straight line from the source to the image receptor.
The grid is positioned between the patient and the image receptor.
The grid is placed between the patient (behind the table or upright bucky) and the cassette.
Improper placement, such as placing the grid backwards, can cause grid errors.
Grids consist of a series of radiopaque material (interspace material).
The use of grids helps reduce scatter radiation reaching the image receptor.
This technique was first demonstrated in 1913 by Gustave Bucky.
Grid ratio, a fundamental concept in understanding grid technology, is the height of the grid divided by the interspace width.
For example, a 12:1 grid has a lead strip height of 12 inches and an interspace width of 1 inch.
High ratio grids are more effective in reducing scatter radiation than low ratio grids, but increase patient dose.
Contrast Improvement Factor is the ratio of radiographic contrast with a grid to that without a grid. It measures the improvement in image quality when grids are used.
Bucky Factor is the ratio of patient dose with and without a grid. It measures the increase in exposure necessary to compensate for the use of a grid.

When to Use a Grid

Use a grid when the kVp is above 60.
Use a grid when the body part exceeds 10cm and the tissue density is primarily soft tissue and bone.

Grid Classifications

Grids can be stationary or moving.

Grid Types

Grids can be linear, parallel, focused, or crossed.

Parallel Grid

Used in portable and OR radiography.
Cleans up scatter radiation in only one direction.
Has a "grid-cut off."

Focused Grid

Designed to minimize grid cut-off.
Used in moving grids.
More superior than parallel grids.

Crossed Grid

Consists of two linear grids superimposed, one above the other.
Used in special procedures.
More efficient in cleaning up scatter radiation.
Has more grid cut-off.
Not commonly used.

Moving Grid

An obvious, annoying shortcoming of moving grids is that they can produce grid lines on the image.
Moving grids were introduced in 1920 by Hollis E. Potter, by moving the grid while the x-ray exposure is being made.
Moving grids are either reciprocating (back-and-forth) or oscillating (circular).

Grid Problems

Off-level grid
Off-center grid
Off-focused grid
Upside-down grid
Combined off-center/off-focused

Air Gap Technique

The image receptor (IR) is moved 10–15 cm away from the patient to reduce scatter radiation. A portion of scatter x-rays generated in the patient would be scattered away from the IR and not recorded.

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Description

This quiz covers the essential concepts of radiographic grids, including their design, function, and placement. Learn about the impact of grid ratio on image quality and scatter radiation. Test your understanding of grid technology and its historical development.