A Device For Measuring Acoustic Output Intensity Of Transcranial Doppler Ultrasound Transducers For Comparison With FDA Regulations

Authors

Sarah Altman, University of Nebraska-LincolnFollow
Gregory Bashford, University of Nebraska-LincolnFollow
Benjamin Hage, University of Nebraska-LincolnFollow

Date of this Version

Spring 2023

Document Type

Thesis

Citation

S. Altman, B. Hage, & G. Bashford. A Device For Measuring Acoustic Output Intensity Of Transcranial Doppler Ultrasound Transducers For Comparison With FDA Regulations. Undergraduate Honors Theses, University of Nebraska-Lincoln. 2023.

Comments

Copyright Sarah Altman, Gregory Bashford, and Benjamin Hage 2023.

Abstract

Transcranial Doppler Ultrasonography (TCD) is a non-invasive methodology which can evaluate cerebral blood flow velocity in real time. Single-element focused circular transducers placed on the scalp produce ultrasound waves capable of penetrating the skull with minimal aberration, enabling measurement of the Doppler shift. As such, TCD can measure blood flow velocity in the internal carotid and vertebral arteries, as well as the arteries of the Circle of Willis: the Anterior Cerebral (ACA), Posterior Cerebral (PCA), and Middle Cerebral Arteries (MCA). Intracranial aneurysm and ischemic stroke are serious conditions in which ballooning or occlusion of cerebral vessels cause insufficient perfusion, leading to severe neurological damage if not promptly detected and treated. TCD has the power to detect such conditions by reporting changes in blood flow velocity.

To develop commercial TCD systems, transducers must be calibrated to ensure they are compliant with Food and Drug Administration (FDA) regulations regarding maximum allowable acoustic intensity output into the brain. To this end, the Biomedical Imaging and Biosignal Analysis lab (BIBA) is working to develop a translation stage capable of generating visualizations of the acoustic field for transducers. Previous work in BIBA has led to the development of an Arduino-driven translation stage capable of driving transducers over a water tank with millimeter precision. This system uses a bullet hydrophone to record acoustic pressure waves, which are then used to create transducer beam plots, allowing visualization of transducer beam shape and intensity and calculation of spatial-peak temporal-average intensity (I_SPTA), a measure of the average power which is used by the FDA to define maximum allowable values for ultrasound systems. This work describes improvements to BIBA’s testing system to add user-input functionality to the LabView command module, including the specification of sampling mode and recording length. Further, a MATLAB script capable of calculating I_SPTA for a transducer is developed and tested.