During lumbar imaging, which parameter adjustment best balances dose and image quality?

• A. Lower kVp with higher mAs.
• B. Using a wide beam without restriction.
• C. Higher kVp with lower mAs.
• D. Increasing exposure time.

Answer: (C)

The key idea is to optimize dose while keeping image quality diagnostic. For lumbar imaging, you get enough bone detail because the vertebrae provide strong contrast against soft tissue, so you can use higher beam energy (kVp) to improve penetration and reduce the amount of current (mAs) needed. Raising kVp allows the photons to pass through more easily, so you can lower mAs and still achieve a receptor exposure that is adequate for visualization. Lowering mAs directly cuts patient dose, and the accompanying slight reduction in image contrast is acceptable here because bone detail remains distinguishable with proper exposure and technique. Using a wider beam or increasing exposure time would raise dose or blur the image, and lowering kVp with higher mAs increases dose without giving a meaningful gain in diagnostic yield.