Question

If the exposure rate constant is 0. 87 Rcm2/mCi-hr and the average patient transmission factor is 0. 2, the exposure rate mR/hr. At 12. 5 cm for a patient who has been injected with 20 mCi of Tc-99m is 22 21 20 19

Answer 1

To find the exposure rate (in mR/hr) at a distance of 12.5 cm, we can use the following equation:

Exposure Rate (mR/hr) = Exposure Rate Constant (Rcm²/mCi-hr) × Activity (mCi) × Transmission Factor / Distance² (cm²)

Plugging in the given values:

Exposure Rate (mR/hr) = 0.87 Rcm²/mCi-hr × 20 mCi × 0.2 / (12.5 cm)²

Exposure Rate (mR/hr) = 17.4 Rcm²/hr × 0.2 / 156.25 cm²

Exposure Rate (mR/hr) = 3.48 Rcm²/hr / 156.25 cm²

Exposure Rate (mR/hr) ≈ 0.0223 R/hr

Since 1 R (Roentgen) is equal to 1000 mR (milliroentgen), we can convert the exposure rate to mR/hr:

Exposure Rate (mR/hr) ≈ 0.0223 R/hr × 1000 mR/R

Exposure Rate (mR/hr) ≈ 22.3 mR/hr

The closest answer choice is:

A) 22