RTBC Fundamentals Of Digital Radiography Practice Test

Describe the impact of grid ratio on image quality and patient dose in DR.

Lower grid ratio reduces patient dose while increasing scatter. Higher grid ratio improves scatter rejection and contrast but requires higher exposure (dose) to maintain signal. Grid ratio has no effect on image quality or dose. Higher grid ratio reduces scatter and does not affect exposure.

Correct Answer:

Higher grid ratio improves scatter rejection and contrast but requires higher exposure (dose) to maintain signal.

Explanation:

Grid ratio is about how tall the lead strips are compared to the space between them. A higher grid ratio makes the grid more effective at blocking scattered radiation, so image contrast improves because the fog from scatter is reduced and the anatomy stands out more on the DR image. But that same grid also absorbs a portion of the useful primary beam, so to keep the image brightness consistent you must increase the exposure (more mA-seconds or other exposure adjustments). That means the patient receives a higher dose when you use a higher grid ratio. The stronger scatter rejection and better contrast come with the trade-off of increased patient dose if the technique isn’t adjusted, which is why this option correctly describes the relationship.

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