The SID indicator must represent the actual SID within what tolerance?

The SID indicator must represent the actual SID within what tolerance?

• A. +/- 1% of the SID
• B. +/- 5% of the SID
• C. +/- 2% of the SID
• D. +/- 10% of the SID

Answer: (C)

Accurate SID indication is essential because image geometry and exposure calculations depend on the true distance from the X-ray source to the image receptor. If the SID indicator is off, magnification estimates and dose calculations will be incorrect, potentially affecting image quality and patient safety. The accepted tolerance is that the indicator must match the actual SID within about 2% of the distance. For example, with a true SID of 100 cm, the display should read between 98 cm and 102 cm. This tight tolerance helps keep magnification predictable and ensures consistency in technique and patient dose across exams. If the indicator drifts beyond this limit, recalibration or adjustment is needed.

Accurate SID indication is essential because image geometry and exposure calculations depend on the true distance from the X-ray source to the image receptor. If the SID indicator is off, magnification estimates and dose calculations will be incorrect, potentially affecting image quality and patient safety. The accepted tolerance is that the indicator must match the actual SID within about 2% of the distance. For example, with a true SID of 100 cm, the display should read between 98 cm and 102 cm. This tight tolerance helps keep magnification predictable and ensures consistency in technique and patient dose across exams. If the indicator drifts beyond this limit, recalibration or adjustment is needed.