Which pulse sequences are known to cause the greatest tissue heating?

The answer is based on understanding the mechanisms behind tissue heating during MRI. Turbo Spin Echo (TSE) and Fast Spin Echo (FSE) sequences are known for their efficiency in acquiring images quickly by applying multiple 180-degree refocusing pulses. While this increases the signal and reduces scan time, it also enhances the potential for tissue heating.

These sequences have higher specific absorption rates (SAR) due to the multiple radiofrequency (RF) pulses involved. Increased SAR results in more energy being deposited into the tissues, which can lead to a greater increase in tissue temperature. The effect becomes more pronounced with longer scan times and higher pulse repetition frequencies, which can occur with TSE/FSE sequences.

In contrast, other sequences such as Gradient Echo, Inversion Recovery, and Spin Echo generally involve fewer RF pulses or less energy deposition per pulse, leading to a lower potential for heating compared to TSE/FSE sequences. Therefore, Turbo Spin Echo and Fast Spin Echo are particularly noted for their enhanced heat generation, making them the sequences associated with the greatest tissue heating during MRI procedures.