How is the specific absorption rate (SAR) affected by pulse duration and flip angle?

The specific absorption rate (SAR) is a measure of the rate at which energy is absorbed by tissue when exposed to an RF (radiofrequency) electromagnetic field during MRI procedures. The relationship between SAR, pulse duration, and flip angle is significant in understanding patient safety and optimizing imaging protocols.

When considering pulse duration, a longer pulse duration allows for more energy to be deposited into the tissue, thereby increasing SAR. Similarly, a larger flip angle typically requires more energy to achieve the desired level of magnetization, which also increases SAR. Therefore, both the flip angle and pulse duration directly contribute to an increase in the SAR.

This direct proportionality means that as the pulse duration increases or the flip angle increases, the SAR will accordingly rise, highlighting the importance of monitoring these parameters to ensure safe practices during MRI scans. Understanding this relationship is crucial for MRI technologists and radiologists to optimize imaging parameters while adhering to safety standards to minimize the risk of excessive heating of tissues.