A radiographic unit has an output intensity of 50uGya/mAs at a distance of 100cm with 150 kVp. If 100kVp is used with 60mAs, what would be the patient dose?

A radiographic unit has an output intensity of 50uGya/mAs at a distance of 100cm with 150 kVp. If 100kVp is used with 60mAs, what would be the patient dose?

• A. 0.8 mGya/mAs
• B. 1.0 mGya/mAs
• C. 1.3 mGya/mAs
• D. 1.5 mGya/mAs

Answer: (C)

To determine the patient dose when changing the kilovoltage peak (kVp) and milliampere-seconds (mAs), we start by understanding the relationship between these variables. The original scenario gives an output intensity of 50 µGya/mAs at 100 cm with 150 kVp. When changing to 100 kVp, a reduction in kVp will influence the dose due to the relationship between kVp and the penetration power of the X-ray beam. Typically, decreasing the kVp results in a reduction of radiation intensity reaching the patient. When adjusting the mAs, which in this question is now set to 60, the expectation is that the dose will also vary based on the new settings. A general principle in radiography is that lowering the kVp by about 20% can effectively decrease the radiation dose by about 50%, but this is not linear; rather, it is exponential. As a rule of thumb, for every 10% reduction in kVp, there is roughly a 30% reduction in exposure. In the original set-up at 150 kVp and 50 µGya/mAs, the dose can be understood as a starting point. When lowered to 100 kVp (

To determine the patient dose when changing the kilovoltage peak (kVp) and milliampere-seconds (mAs), we start by understanding the relationship between these variables.

The original scenario gives an output intensity of 50 µGya/mAs at 100 cm with 150 kVp. When changing to 100 kVp, a reduction in kVp will influence the dose due to the relationship between kVp and the penetration power of the X-ray beam. Typically, decreasing the kVp results in a reduction of radiation intensity reaching the patient.

When adjusting the mAs, which in this question is now set to 60, the expectation is that the dose will also vary based on the new settings. A general principle in radiography is that lowering the kVp by about 20% can effectively decrease the radiation dose by about 50%, but this is not linear; rather, it is exponential. As a rule of thumb, for every 10% reduction in kVp, there is roughly a 30% reduction in exposure.

In the original set-up at 150 kVp and 50 µGya/mAs, the dose can be understood as a starting point. When lowered to 100 kVp (