CAMRT Radiography Practice Exam

Which combination of mA and scan time provides 350 mAs for a cardiac scan?

1. 300 mA, scan time 0.50 seconds

2. 700 mA, scan time 0.5 seconds

3. 350 mA, scan time 1 second

4. 300 mA, scan time 2 seconds

The correct answer is: 700 mA, scan time 0.5 seconds

To determine which combination of milliampere-seconds (mAs) corresponds to 350 mAs, it's essential to understand the relationship between milliamperes (mA), scan time (in seconds), and mAs. The mAs is calculated by multiplying the mA by the scan time. In this case, we need a total of 350 mAs. Looking at the combination of 700 mA and a scan time of 0.5 seconds, you can calculate the mAs as follows: 700 mA x 0.5 seconds = 350 mAs. This calculation shows that the combination directly meets the requirement for 350 mAs, making it the correct choice. The other combinations do not yield 350 mAs when you perform the calculations. 300 mA with 0.5 seconds gives 150 mAs, 350 mA with a 1-second scan time results in 350 mAs but does not address the scan time reduction necessary for cardiac imaging, which typically involves rapid scanning, and 300 mA with 2 seconds results in 600 mAs, which is over the target. Therefore, the combination that provides exactly 350 mAs and aligns with the requirements for