High resolution transcranial acoustoelectric imaging of current densities from a directional deep brain stimulator

Abstract

Objective. New innovations in deep brain stimulation (DBS) enable directional current steering—allowing more precise electrical stimulation of the targeted brain structures for Parkinson’s disease, essential tremor and other neurological disorders. While intra-operative navigation through MRI or CT approaches millimeter accuracy for placing the DBS leads, no existing modality provides feedback of the currents as they spread from the contacts through the brain tissue. In this study, we investigate transcranial acoustoelectric imaging (tAEI) as a new modality to non-invasively image and characterize current produced from a directional DBS lead. tAEI uses ultrasound (US) to modulate tissue resistivity to generate detectable voltage signals proportional to the local currents. Approach. An 8-channel directional DBS lead (Infinity 6172ANS, Abbott Inc) was inserted inside three adult human skulls submerged in 0.9% NaCl. A 2.5 MHz linear array delivered US pulses through the transtemporal window and focused near the contacts on the lead, while a custom amplifier and acquisition system recorded the acoustoelectric (AE) interaction used to generate images. Main results. tAEI detected monopolar current with stimulation pulses as short as 100 µs with an SNR ranging from 10–27 dB when using safe US pressure (mechanical indices <0.78) and injected current of ~2 mA peak amplitude. Adjacent contacts were discernable along the length and within each ring of the lead with a mean radial separation between contacts of 2.10 and 1.34 mm, respectively. Significance. These results demonstrate the feasibility of tAEI for high resolution mapping of directional DBS currents using clinically-relevant stimulation parameters. This new modality may improve the accuracy for placing the DBS leads, guide calibration and programming, and monitor long-term performance of DBS for treatment of Parkinson’s disease.

Biological current source imaging method based on acoustoelectric effect: A systematic review

“…On this basis, he inserted 8-channel directional DBS leads into three adult human skulls immersed in 0.9% NaCl and used a 2.5 MHz linear array to focus near the contacts on the leads. When using a safe ultrasound pressure and an injection current with a peak amplitude of 2 mA, the AEI detected monopolar currents with stimulation pulses as short as 100 μs and a SNR of 10–27 dB (Preston et al, 2020 ).…”

In vivo acoustoelectric imaging for high-resolution visualization of cardiac electric spatiotemporal dynamics

“…Earlier ACI studies have successfully employed this theory and developed the US beamforming, signal acquisition systems, and data visualization tools to measure current densities around electrically active imaging phantoms [15,17,19] and ex vivo Langendorff perfused rat and rabbit hearts [12,20,21]. However, the use of electrical pacing and electromechanical uncouplers like 2,3-butanedione monoxime in these models and the lack of realistic electromagnetic interference from a live animal necessitate the use of in vivo models that better mimic the clinical setting.…”

In Vivo Transcranial Acoustoelectric Brain Imaging of Different Steady-State Visual Stimulation Paradigms

“…Then, tABI was presented by Y. Qin et al in 2017 [6], which is like AENI but more specific in electromagnetic signal type. The feasibility of using an artificial current source for AEI in a human head model and rat hippocampus has been confirmed, and many studies have shown that tABI may be able to accurately resolve deep neuron currents with a high spatial resolution (<3mm) [17][18][19][20][21]. But these models mainly use artificial current sources to simulate neural activity and lack valuable real brain data for verification and optimization.…”