Which items are used for annual testing of X-ray system filtration (HVL)?

• A. dosimeter
• B. type 1100 aluminum sheets
• C. semi-log graph paper
• D. all three

Answer: (D)

Determining HVL requires quantifying how the X-ray beam is attenuated by a known amount of filtration. You need a dosimeter to measure the beam intensity at a fixed geometry, both with and without added filtration. Use sheet aluminum of known thickness (such as Type 1100 aluminum sheets) to incrementally increase filtration and record the resulting exposures. Then plot the measured intensities against the aluminum thickness on semi-log graph paper so the exponential decrease becomes a straight line, allowing you to determine the thickness that reduces the beam to half its unattenuated value—the HVL. Using all three items provides the necessary measurement, the means to add precise filtration, and the analysis method to identify the HVL accurately for annual filtration testing.