During annual QA, which parameter is measured to verify X-ray central ray perpendicularity?

• A. SID Indicator Accuracy
• B. X-ray Beam Perpendicularity
• C. Central Ray Alignment
• D. Beam Angle Calibration

Answer: (B)

The essential idea is ensuring the x-ray beam hits the image receptor at a true right angle. To verify this, you measure X-ray Beam Perpendicularity, which directly quantifies how far the beam deviates from 90 degrees relative to the detector plane. When this parameter is within tolerance, the central ray is effectively perpendicular, helping prevent geometric distortion and magnification errors in the image. SID Indicator Accuracy checks distance readouts, not beam angle; Central Ray Alignment focuses on pointing the beam at the image center but doesn’t quantify the angle relative to the receptor; Beam Angle Calibration involves adjusting the beam’s tilt rather than measuring its perpendicularity.