How is electromagnetic power dissipated within a complex multichannel MRI system?

What is it about?

Modern ultrahigh field MRI machines can utilize multiple radiofrequency elements driven by synchronized high-powered amplifiers to generate interfering high-frequency magnetic fields in the human body. Depending on the chosen amplitude and phase of each amplifier, different interference patterns can be realized, for example to allow recording a very high-fidelity image in a specific region of the human body that would be inaccessible to a simple single-channel system. The power delivered by the amplifers is dissipated throughout the whole system. Most of the power is usually absorbed in the human body to be imaged. Any additional loss, such as that occurring in the RF components (copper traces, capacitors, inductors) or electromagnetic radiation leaving of the MR scanner, degrades the capability of the scanner to produce images of high diagnostic quality. The relative distribution of the power throughout the system is termed power balance. The paper investigates how the power balance changes when modulating the amplitudes and phases of each amplifier. In introducing a matrix-based formalism, it becomes straightforward relate a specific magnetic field interference pattern to

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