Where is RF power the least during an MRI scan?

The point where RF (Radio Frequency) power is the least during an MRI scan is indeed at the edges of the magnetic field. This is primarily due to the way RF energy propagates and interacts with the magnetic field and the body being imaged.

In the context of MRI, RF pulses are used to excite the protons in the body, and the effectiveness of this excitation decreases as you move away from the center (isocenter) of the magnetic field. The RF coil produces a field that is most uniform and intense at the isocenter, where the image quality is typically optimal. However, as you move towards the outer edges of the coil or scanner, the signal strength drops significantly.

This drop in RF power at the periphery can affect the quality of the images gathered from those areas, contributing to potential artifacts or less detailed images. Hence, knowing where RF power is weakest helps in planning and optimizing imaging protocols to ensure diagnostic quality.

In summary, the edges of the magnetic field are indeed where RF power is the least during an MRI scan due to the distribution and intensity of the RF energy as it radiates from the coil.