What do window level and window width control in DR image display, and how should they be used to optimize visualization of a chest radiograph?

• A. Window level shifts grayscale midpoint; window width controls contrast range; for chest radiographs, use a broader width with an appropriate level to visualize both lungs and mediastinum.
• B. Window level controls brightness; width sets sharpness; chest uses broad width.
• C. Level controls color; width controls saturation; chest uses high level.
• D. Level determines patient dose; width adjusts brightness.

Answer: (A)

Window level sets the brightness by determining where the grayscale midpoint falls, while window width determines how many gray shades are available to represent the range of densities in the image, i.e., the contrast range. For a chest radiograph, using a broad window width expands the range of densities that can be displayed—from air in the lungs to soft tissue and bone—so both lung detail and mediastinal contours remain visible. The level should be chosen to place this range around the center of thoracic densities, providing balanced overall brightness. In short, level changes brightness and width changes contrast; a wide width helps visualize both lungs and mediastinal structures, with the level set to keep the image well balanced.