Experimental Study of Ultrasound Transmission Through Rat Skulls
Restricted (Penn State Only)
- Author:
- Hussain, Saira
- Graduate Program:
- Mechanical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 10, 2024
- Committee Members:
- Jason Zachary Moore, Thesis Advisor/Co-Advisor
Yun Jing, Committee Member
Mary Frecker, Program Head/Chair
Daniel Humberto Cortes Correales, Committee Member - Keywords:
- Transcranial Focused Ultrasound
Attenuation
Defocusing
Transducers
Rat Skulls - Abstract:
- Transcranial focused ultrasound is an advancing field of research for non-invasive and safe therapeutic treatments of neurological conditions. However, advancements have been greatly limited by the skull posing as an acoustic barrier due to the difference in impedance from surrounding tissue. In this study, the attenuation and defocusing effects in the acoustic pressure fields resulting from the presence of two ex-vivo rat skulls at therapeutically relevant frequencies were analyzed. Experiments were performed using three focused ultrasound transducers operating at frequencies ranging from 1 to 2.25 MHz. Differences in skulls, skull locations, frequencies, and transducers were explored, and the feasibility of the sonication were evaluated through studying the transmission loss, FWHM, and focal location. It was established that skull thickness and morphology are significant factors in attenuation and defocusing effects. It was also confirmed that although higher frequencies provide higher pressure transmission and sharper focus, it also increases attenuation and defocusing effects. Furthermore, transducer properties influenced the results, though there was minimal variation in the difference of skull locations. It was evaluated that the presence of the skull caused a reduction in intensity at the focal point ranging from 50 to 88%, additionally, defocusing effects increased with higher frequencies. Overall, the attenuation was comparatively more significant than the defocusing effects, indicating that with adjusted parameters and compensation, effective brain stimulation at high frequencies can be achieved.