Which instrument is used to read densitometric values in processor QC?

• A. Densitometer
• B. Colorimeter
• C. Optical micrometer
• D. Geiger counter

Answer: (A)

Measuring how dark a processed radiographic film is requires densitometry. A densitometer is built to quantify optical density by passing a controlled amount of light through the film (or reflecting light off it) and reporting a density value. In processor quality control, you use this reading with a calibration step wedge to ensure the processor is producing consistent densities over time and across the film, which helps detect issues with temperature, developing chemistry, or timing. The other devices don’t measure optical density: a colorimeter assesses color properties, an optical micrometer measures physical dimensions, and a Geiger counter detects radiation. So the densitometer is the appropriate instrument for reading densitometric values.