Transcranial magnetic stimulation (TMS) is one of the most widely used noninvasive brain stimulation method. It has been utilized for both treatment and diagnosis of many neural diseases, such as neuropathic pain and loss of function caused by stroke. Existing TMS tools cannot deliver focused electric field to targeted penetration depth even though many important neurological disorders are originated from there. A breakthrough is needed to achieve noninvasive, focused brain stimulation. We demonstrated using magnetic shield to achieve magnetic focusing without sacrificing significant amount of throughput. The shield is composed of multiple layers of copper ring arrays, which utilize induced current to generate counter magnetic fields. We experimentally set up a two-pole stimulator system to verify device simulation. A transient magnetic field probe was used for field measurements. The focusing effect highly depends on the geometric design of shield. A tight focal spot with a diameter of smaller than 5mm (plotted in Matlab contour map) can be achieved by using copper ring arrays. With properly designed array structures and rings locations, the combined original and induced counter fields can produce a tightly focused field distribution with enhanced field strength at a depth 7.5mm beyond the shield plane, which is sufficient to reach many deep and critical parts of a mouse brain.
Keyphrases
- transcranial magnetic stimulation
- high frequency
- neuropathic pain
- cerebral ischemia
- high density
- high glucose
- molecularly imprinted
- spinal cord
- high resolution
- diabetic rats
- spinal cord injury
- resting state
- optical coherence tomography
- blood brain barrier
- high throughput
- atrial fibrillation
- oxidative stress
- subarachnoid hemorrhage
- functional connectivity
- multiple sclerosis
- quantum dots
- living cells
- optic nerve
- single cell
- fluorescent probe