In QA testing, which parameter assesses beam alignment with the receptor?

• A. Image receptor speed
• B. Exposure timer accuracy
• C. Field-size/collimation accuracy
• D. Focal spot size

Answer: (C)

Aligning the X-ray beam with the receptor means the exposure field is centered on and sized to match the image receptor. Field-size and collimation accuracy is the QA parameter that checks this relationship—the light field you see with the collimator should coincide with the actual X-ray field and cover the receptor area as intended. When this is correct, anatomy is captured without clipping and unnecessary radiation to surrounding tissue is minimized, producing consistent image quality and dose. The other checks focus on different aspects: receptor speed relates to sensitivity and how much exposure is needed for a given image, timer accuracy governs the actual exposure duration, and focal spot size affects image sharpness and geometric blur, not how the beam aligns with the receptor.