As the Phase Matrix increases, which of the following decreases?

When the Phase Matrix increases, it refers to a higher number of phase encoding steps in MRI imaging. This adjustment affects several aspects of the images produced. As the Phase Matrix increases, the Signal-to-Noise Ratio (SNR) tends to decrease. This is because a higher Phase Matrix requires more phase encoding steps, which can lead to longer acquisition times and may not necessarily result in a proportional increase in signal strength.

In MRI, SNR is heavily influenced by the number of acquisitions and the time available to collect signal. When the Phase Matrix increases, the overall data acquisition is stretched across more steps, diluting the signal collected at each individual step. Essentially, while you're improving spatial resolution by acquiring more data points, you are also sampling the same amount of signal over a longer period, which can impact the clarity of that signal.

Other factors like spatial resolution, scan time, and slice thickness do change with an increase in Phase Matrix, but in a manner opposite to SNR. For example, spatial resolution improves because more data is being collected, scan time increases due to the additional phase encoding steps, and slice thickness is typically determined by other settings in the scan protocol. Thus, the relationship of increasing the Phase Matrix to a decrease in SNR is