As kVp increases with digital DR imaging, the histogram becomes

• A. Broader histogram
• B. Narrower histogram
• C. No change
• D. Unpredictable

Answer: (B)

In digital DR, the histogram shows how pixel values (gray levels) are distributed across the image. The width of that histogram reflects how many different gray values appear: a wide spread means many extremes (very dark and very bright areas), while a narrow spread means most pixels cluster around similar mid-range values.

When kVp increases, the beam is more penetrating and the differences in attenuation between tissues become smaller. That reduces subject contrast, so the transmitted intensities across different tissues become more alike. In the detector, this translates to more pixels falling within a smaller range of gray values rather than spanning a broad spectrum. The result is a concentration of pixel values in a narrower band, so the histogram becomes narrower.