In annual Gy/mAs testing, which statements are true? 1 test device is a dosimeter 2 test device is a homogeneous phantom 3 performance criteria is +/- 10%

• A. Dosimeter only; +/-10%
• B. Homogeneous phantom only; +/-10%
• C. Dosimeter and homogeneous phantom; +/-5%
• D. Dosimeter and homogeneous phantom; +/-10%

Answer: (D)

In annual Gy/mAs testing, you want to verify the beam output per mAs under conditions that resemble a patient’s path. That requires both a dosimeter to measure the actual dose and a homogeneous phantom to simulate tissue and provide a consistent, tissue-like attenuation and scatter environment. The dosimeter gives you a quantitative reading of dose, while the phantom ensures that the measurement reflects what a patient would receive rather than just free-air exposure.

Using both together with a tolerance of ±10% means you’re allowing for typical minor variations in calibration, beam quality, and setup, while still flagging significant drift. Relying on only a dosimeter would miss tissue-equivalent effects, and relying on only a phantom would not yield a numerical dose reading. A tighter ±5% tolerance is more stringent than usual for annual checks.