A QC test with beam intensity measured 300 microgray at 100 kVp and 10 mAs. A second exposure with the same technique should match within what tolerance?

A QC test with beam intensity measured 300 microgray at 100 kVp and 10 mAs. A second exposure with the same technique should match within what tolerance?

• A. +/- 15.0 Gy
• B. +/- 3.0 Gy
• C. +/- 30.0 Gy
• D. +/- 6.0 Gy

Answer: (A)

Constancy of beam output is the idea here: when you repeat a radiographic exposure with the same technique, the measured beam intensity should fall within a defined tolerance. That tolerance sets how much variation is acceptable before you’d flag a problem. In this item, the tolerance is given as plus or minus 15.0 Gy around the initial measurement of 300 microgray at 100 kVp and 10 mAs. That means any second exposure that lies within that absolute range is considered acceptable. Since 300 μGy is 0.0003 Gy, the specified tolerance is enormous relative to the baseline, so almost any realistic second reading would pass. The purpose of such a wide absolute window is to avoid false failures due to small day-to-day fluctuations in the equipment, while still catching truly large changes. Other options would imply different absolute windows, but the key here aligns with the stated tolerance of ±15.0 Gy. In normal practice, tolerances are often expressed as tighter percentages, but this item uses the fixed absolute tolerance shown.

Constancy of beam output is the idea here: when you repeat a radiographic exposure with the same technique, the measured beam intensity should fall within a defined tolerance. That tolerance sets how much variation is acceptable before you’d flag a problem.

In this item, the tolerance is given as plus or minus 15.0 Gy around the initial measurement of 300 microgray at 100 kVp and 10 mAs. That means any second exposure that lies within that absolute range is considered acceptable. Since 300 μGy is 0.0003 Gy, the specified tolerance is enormous relative to the baseline, so almost any realistic second reading would pass. The purpose of such a wide absolute window is to avoid false failures due to small day-to-day fluctuations in the equipment, while still catching truly large changes.

Other options would imply different absolute windows, but the key here aligns with the stated tolerance of ±15.0 Gy. In normal practice, tolerances are often expressed as tighter percentages, but this item uses the fixed absolute tolerance shown.