Grids, use of them and selection/problems, etc

• 1. Which of the following is NOT a grid positioning error?– A. air-gap technique– B. Lateral decentering– C. Off center grid– D. off focus grid– E. Off level grid

The MOST common grid used in portable imaging is:

• A. Crossed grid• B. A focused, moving grid• C. A focused stationary grid• D. A. Parallel, moving grid• E. A parallel, stationary grid

Grids generally:

• A. Must be cleaned on schedule• B. Require faster image receptors• C. Require less mAs• D. Require periodic replacement due to

radiation fatigue• E. Use of required increased patient dose

Which of the following will result in the lowest patient dose?

• A. High kVp and high-ratio grid• B. High kVp and low-ratio grid• C. High kVp and no grid• D. Low kVp and high-ratio grid• E. Low kVp and low-ratio grid

Grid cutoff:

• A. Is measured by the Bucky Factor (BF)• B. Is more pronounced with high-ratio grids• C. Is more pronounced with low-ratio grids• D. Never occurs with focused grids• E. Occurs only with focused grids

Air-gap technique:

• A. Increases the Bucky Factor• B. Reduces contrast by absorption of scattered

radiation in air• C. Requires that the grid and the film must be

separated by at least 30 cm• D. Results in approx. the same patient dose as

non-grid• E. Results in image magnification

Which grid would be MOST likely to produce grid cut-off?

• A. 5:1• B. 6:1• C. 8:1• D. 12:1• E. 16:1

Which grid has the GREATEST contrast improvement factor?

• A. Crossed grids• B. Focused grids• C. Moving grids• D. Parallel grids• E. Zero grids

What is the result of replacing an 8:1 grid with a 12:1 grid?

• A. Greater positioning latitude• B. Higher pt. dose• C. Less contrast• D. Less spatial resolution• E. Lower pt. dose

Grid ratio refers to:

• A. The height of the pb strips to their width• B. The length of the pb strips to the space

between them• C. The height of the pb strips to their thickness• D. The height of the pb strips to the space

between them

Most grids in RAD rooms are:

• A. 5:1 parallel• B. 8:1 parallel• C. 8:1 focused• D. 12:1 focused