Design of a Small, Affordable Low Intensity Focused Ultrasound Device for Vagus Nerve Stimulation

Depression is a serious public health issue that affects more than 300 million people worldwide. While there are antidepressant drugs to alleviate depressive symptoms, 10 – 30% of patients either do not respond or develop a tolerance to these drugs. Researchers have found a correlation between the inflammatory response and treatment-resistant depression (TRD). Blocking this inflammatory pathway with electrical vagus nerve stimulation (VNS) can reduce cytokine levels and depressive symptoms. However, placing an electrical VNS device is invasive, costly, and poses a risk to the vagus nerve. Low intensity focused ultrasound (LIFU) is a novel therapy that is able to both excite and suppress neuronal activity in neurological disorders. However, progression of this research area has been impeded by the size and price of these devices. I designed a 50 x 57 x 76 mm LIFU device that consists of a transducer, matching network, and amplification network. Next, I characterized my LIFU device with 2D intensity maps of the focused ultrasound (FUS) field. My device produced an instantaneous intensity up to 350 mW/cm2. My colleagues and I applied the LIFU device on Sprague-Dawley rats (n=12) for VNS with the primary goal of reducing the inflammatory response. Five out of the eight rats that we analyzed showed a decrease in the cytokine TNF-α. Future work will involve design improvements and more animal studies with varying stimulation parameters. As FUS technology becomes smaller we move closer to wearable devices. As FUS technology becomes more affordable more research groups will have the opportunity to employ this novel therapy to investigate the pathophysiology of neurological disorders

Driving Circuitry for Focused Ultrasound Noninvasive Surgery and Drug Delivery Applications

Recent works on focused ultrasound (FUS) have shown great promise for cancer therapy. Researchers are continuously trying to improve system performance, which is resulting in an increased complexity that is more apparent when using multi-element phased array systems. This has led to significant efforts to reduce system size and cost by relying on system integration. Although ideas from other fields such as microwave antenna phased arrays can be adopted in FUS, the application requirements differ significantly since the frequency range used in FUS is much lower. In this paper, we review recent efforts to design efficient power monitoring, phase shifting and output driving techniques used specifically for high intensity focused ultrasound (HIFU)

Development of a medical imaging-based technology for cancer treatment

The Electrical Impedance Mammography (EIM) device is an imaging system developed at the University of Sussex for the detection of breast lesions in vivo using quadrature detection of impedance. The work describes a novel technique to integrate Ultrasound-guided Focused Ultrasound Surgery (USgFUS) with the existing EIM system. The benefits that such a system could provide include the possibility of non-invasive detection, diagnosis and treatment of breast cancer all within a single device and involving no radiation. Furthermore the timescales involved would allow the process to be considered an outpatient procedure such that a patient can be diagnosed and treated on the same day using the same device. Various geometries of transducer were investigated for physical compatibility as well as the ability to target the entire specified volume, based on the dimensions of the existing system. Simulations were performed using a custom written code based on Huygen’s principle, allowing minimum surface area and power requirements to be determined and feasibility of designs to be evaluated. The use of phase differences in the excitation signals applied to individual elements was also investigated, thus the effect of steering the simulated focus could be observed, an important factor to consider when attempting to incorporate a transducer into a device with restricted dimensions. Resulting simulated pressure fields were used to obtain acoustic intensity fields, which could then be used as inputs in the Pennes Bio-Heat Transfer Equation (BHTE) allowing temperature distributions to be observed. Preliminary studies proved the feasibility of using the suggested transducer design in conjunction with the existing EIM system. Pressure fields and heating patterns were all within acceptable limits, confirming the ability of the device to effectively ablate cancerous tissue. Additionally the capability to steer the resultant focal point was validated, and a thermal dose model was implemented allowing different heating patterns to be quantitatively compared