If the dose of scatter radiation in fluoroscopy to the radiographer is 10 mGya at a distance of 2 feet from the table, where should the radiographer stand to reduce the dose to 2.5 mGya?

If the dose of scatter radiation in fluoroscopy to the radiographer is 10 mGya at a distance of 2 feet from the table, where should the radiographer stand to reduce the dose to 2.5 mGya?

• A. Directly behind the fluoroscopist
• B. At the foot of the table
• C. 4 feet
• D. 8 feet

Answer: (C)

The inverse square law governs this: radiation dose decreases with the square of the distance from the source. If the scatter dose is 10 mGy at 2 feet, the dose at a new distance r is 10 × (2^2 / r^2). To reach 2.5 mGy, solve for r: 2.5 = 10 × (4 / r^2), which gives r^2 = 16, so r = 4 feet. You should stand 4 feet away from the table to achieve 2.5 mGy. Standing farther away, like 8 feet, would reduce the dose further (to about 0.625 mGy), while standing closer would result in a higher dose than 2.5 mGy.

The inverse square law governs this: radiation dose decreases with the square of the distance from the source. If the scatter dose is 10 mGy at 2 feet, the dose at a new distance r is 10 × (2^2 / r^2). To reach 2.5 mGy, solve for r: 2.5 = 10 × (4 / r^2), which gives r^2 = 16, so r = 4 feet. You should stand 4 feet away from the table to achieve 2.5 mGy.

Standing farther away, like 8 feet, would reduce the dose further (to about 0.625 mGy), while standing closer would result in a higher dose than 2.5 mGy.