Optical detuning slashes MRI coil power to 10 mW for flexible arrays

MRI receive coils require detuning during transmit to avoid excessive currents and patient safety risks. Traditional galvanic detuning uses wired connections that limit coil flexibility and increase complexity. In a new arXiv preprint (arXiv:2607.06849), Jakob Gerlach and colleagues from the University of Freiburg systematically compare four optical detuning strategies for shielded loop resonators (SLRs) at 3T, aiming to replace wires with light-based control.

The team tested photodiode-PIN diode combinations, phototransistors, and passive detuning against conventional galvanic detuning. The photodiode-PIN diode combo performed best, achieving an unloaded Q factor of 68.6 and a Q ratio of 1.9 at just 10 mW optical power — performance comparable to galvanic detuning in bench tests and phantom SNR measurements. A flexible four-channel SLR array using this strategy was built and validated in vivo, producing high-quality knee and brain images.

The shift to optical detuning promises fully flexible, lightweight coil arrays that eliminate electrical cables, reducing patient discomfort and enabling new MRI applications. While passive detuning (wireless) also worked, active optical control provides robust detuning across all channels. The authors note that optimizing optical power requirements — already modest at 10 mW per channel — is a critical step toward clinical adoption of all-optical receive arrays.