How much SNR improvement does a quadrature coil offer over a linear coil of the same size?

A quadrature coil provides an improvement of √2 in signal-to-noise ratio (SNR) compared to a linear coil of the same size due to its ability to detect signals in two orthogonal (90-degree) directions. This dual sensitivity allows the quadrature coil to combine the signals received from both orientations, effectively doubling the amount of useful signal that can be captured.

In the context of MRI, the quadrature coil works by aligning the receiver's sensitivity with the magnetic field's spatial characteristics, which enhances the overall signal detection capability. The square root relationship comes from the principles of how noise and signals are combined mathematically. Since noise generally adds in a way that is independent of the direction of the signal, while the signal from both directions combines constructively, the improvement in SNR becomes √2, showing a clearer advantage of the quadrature design over the linear configuration.

Understanding this concept is essential when considering coil design in MRI, as higher SNR leads to improved image quality and clearer diagnostic capabilities.