Methodology for improved detection of low concentration metabolites in MRS: Optimised combination of signals from multi-element coil arrays

- This work looks at the combination of MRS data from multi element coils.
- Multi element coils are becoming more popular, with number of elements increasing.
- Using signal to noise squared weighting, SNR of combined spectrum is improved.
- Comparison with other methods is performed using simulations and in-vivo 7T data.

State of the art magnetic resonance imaging (MRI) scanners are generally equipped with multi-element receive coils; 16 or 32 channel coils are common. Their development has been predominant for parallel imaging to enable faster scanning. Less consideration has been given to localized magnetic resonance spectroscopy (MRS). Multinuclear studies, for example 31P or 13C MRS, are often conducted with a single element coil located over the region of interest. 1H MRS studies have generally employed the same multi-element coils used for MRI, but little consideration has been given as to how the spectroscopic data from the different channels are combined. In many cases it is simply co-added with detrimental effect on the signal to noise ratio. In this study, we derive the optimum method for combining multi-coil data, namely weighting with the ratio of signal to the square of the noise. We show that provided that the noise is uncorrelated, this is the theoretical optimal combination. The method is demonstrated for in vivo proton MRS data acquired using a 32 channel receive coil at 7 T in four different brain areas; left motor and right motor, occipital cortex and medial frontal cortex.