Given the following parameters, which sequence has the lowest heating?

The sequence with the lowest heating is determined by considering the parameters that influence specific absorption rate (SAR) and the resultant heating effects during MRI scans.

In the provided options, the relevant parameters to assess are the pulse duration and the flip angle in terms of energy deposition in tissues. Generally, a lower flip angle results in less energy being deposited into the tissue during a pulse sequence, contributing to increased safety with respect to heating. Additionally, shorter pulse durations typically lead to reduced heating since the duration of RF exposure is minimized.

Option C stands out because it has a flip angle of 100 degrees, which is lower than the others. This implies that it will generate less RF energy deposition compared to the higher angles. Furthermore, it has a TR of 2000 ms and a pulse duration of only 1 ms, which further limits the time the tissue is exposed to the RF pulse compared to options with longer pulse durations.

In comparison, the other options either feature higher flip angles or longer pulse durations, which lead to higher energy absorption and consequently increased heating effects. Thus, the combination of a lower flip angle and a shorter pulse duration in option C results in the lowest heating effects among the choices provided.