Biomagnetic signals recorded from Transcranial Magnetic Stimulation invoked activity

Transcranial magnetic stimulation (TMS) has widespread clinical applications from diagnosis to treatment of various motor neuron disorders. We combined TMS with non-contact magnetic detection of TMS-evoked muscle activity in peripheral limbs to explore a new diagnostic modality that enhances the utility of TMS as a clinical tool by leveraging technological advances in magnetometry. The biomagnetic signals from evoked muscle activity contain detailed and unique information that is complementary to electromyograph (EMG) data. We recorded measurements inside a hospital setting using an array of optically pumped magnetometers (OPMs) inside a portable shield that encompasses only the forearm and hand of the subject. We present magnetomyographs (MMG)s of TMS-evoked movement in a human hand, together with a simultaneous surface EMG and electroencephalograph (EEG). The MMG provides important spatial and timing information to aid in analysis of the electric signal channels. Moreover, we identify greater detail in the magnetic recording beyond that of the EMG, which informs detailed temporal analysis of the EEG. This system demonstrates the value of biomagentic signals in TMS-based diagnoses and treatment and has widespread clinical and research potential. Learn More(arXiv)1

Battery diagnostics with atomic magnetometers

The ever-increasing demand for high-capacity rechargeable batteries highlights the need for sensitive and accurate diagnostic technology for determining the state of a cell, for identifying and localizing defects, or for sensing capacity loss mechanisms. Here, we demonstrate the use of atomic magnetometry to map the weak induced magnetic fields around a Li-ion battery cell as a function of state of charge and upon introducing mechanical defects. These measurements provide maps of the magnetic susceptibility of the cell, which follow trends characteristic for the battery materials under study upon discharge. In addition, the measurements reveal hitherto unknown long time-scale transient internal current effects, which were particularly pronounced in the overdischarged regime. The diagnostic power of this technique is promising for the assessment of cells in research, quality control, or during operation, and could help uncover details of charge storage and failure processes in cells. Learn More(arXiv)

Past Experiments