Ultra-low-field MRI uses microtesla fields for signal encoding and sensitive superconducting quantum interference devices for signal detection. Similarly, modern magnetoencephalography (MEG) systems use arrays comprising hundreds of superconducting quantum interference device channels to measure the magnetic field generated by neuronal activity. In this article, hybrid MEG-MRI instrumentation based on a commercial whole-head MEG device is described. The combination of ultra-low-field MRI and MEG in a single device is expected to significantly reduce coregistration errors between the two modalities, to simplify MEG analysis, and to improve MEG localization accuracy. The sensor solutions, MRI coils (including a superconducting polarizing coil), an optimized pulse sequence, and a reconstruction method suitable for hybrid MEG-MRI measurements are described. The performance of the device is demonstrated by presenting ultra-low-field-MR images and MEG recordings that are compared with data obtained with a 3T scanner and a commercial MEG device.

The visually evoked field (VEF) maps at 80 ms after the stimulus onset. The contour step is 50 fT; red indicates field out and blue into the head surface. The green arrows depict the surface projection of the equivalent current dipoles fitted to the data. This image is from the article by Vesanen et al (pp 1795-1804).

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Altered electrocardiographic ventricular repolarization, indicating reduced repolarization reserve and possibly increased repolarization heterogeneity, is already present in hypertensive men with only mild LVM increase. At a population level, this may carry important risk implications for the large group of hypertensive patients.