Which device is used to measure HVL?

• A. Dosimeter
• B. Geiger counter
• C. Ionization chamber
• D. Densitometer

Answer: (A)

HVL is found by measuring how much the beam is attenuated as you pass it through increasing thicknesses of a filter, and identifying the thickness that reduces the beam intensity to half. To do this accurately, you need a detector that gives a direct, stable measure of the beam’s exposure (air kerma) as a function of thickness. An ionization chamber provides that precise, real-time exposure reading and has a linear response in the diagnostic X-ray range, making it ideal for HVL measurements.

A dosimeter is a general dose-measuring device, but HVL requires exact transmission measurements rather than accumulated dose over time. A Geiger counter is not suitable due to its limited energy response and lower accuracy for this purpose. A densitometer measures film density, not the transmitted beam exposure, so it isn’t used for HVL.