Question

How should the mAs be varied to compensate for an increase in apparent image noise casued by reducing the slice thickness?

a. halve the mA and halve the scan time
b. halve the mA and double the scan time
c. decrease mAs
d. increase mAs

Answer 1

To reduce image noise caused by decreasing slice thickness, one should increase the mAs, which directly increases the photon flux and reduces noise.

Step-by-step explanation:

To compensate for an increase in apparent image noise caused by reducing the slice thickness, one should increase the mAs (milliampere-seconds). This is because image noise is inversely proportional to the square root of the number of photons, which in turn is directly proportional to the mAs. Reducing the slice thickness reduces the number of photons contributing to the image, thereby increasing noise. To counteract this, increasing the mAs will increase the photon flux, thus reducing noise. The correct option is to increase mAs, rather than reducing it or altering the scan time significantly.