Increasing bit depth in digital radiography primarily affects which aspect?

• A. Spatial resolution
• B. Gray-level resolution
• C. Noise
• D. Detector dosage

Answer: (B)

Bit depth determines how many gray shades a pixel can store, which is what gray-level resolution is all about. When you increase bit depth, you expand the number of quantization levels (for example, from 256 levels with 8-bit to thousands with 12-bit or tens of thousands with 16-bit), so the image can represent subtler differences in tissue contrast. This improves the ability to distinguish between tissues that are similar in brightness.

Spatial resolution, on the other hand, is about how sharp or finely detailed the image is, which depends on factors like pixel size, detector sampling, and imaging geometry, not the number of gray shades. Noise relates to random fluctuations in the signal and is influenced by exposure and detector characteristics, not directly by bit depth. Detector dosage refers to the amount of radiation used during exposure, which also doesn’t change with bit depth. So the main effect of increasing bit depth is better gray-level resolution.