Relationships Between Cranial Phantom Physical Characteristics and Transcranial Acoustic Wave Signal Features

During head examinations, real-time information relevant to potential cerebral injuries can be obtained using a simple, noninvasive, and portable ultrasound scanning protocol. However, for adult human applications, the clinical diagnostic process based on transcranial ultrasound imaging (TCUS) remains inconclusive. This is due to acoustic aberrations, i.e., attenuation and distortion of the detected ultrasound signal caused by cranial bone. Variations of cranial physical properties, specifically the thickness and porosity, strongly impact the structural and mechanical properties. Therefore, these two parameters are considered dominating factors that dictate the aberration mechanism in cranial bone. Here, we propose an approach to understand the influence of these characteristics on acoustic signal degradation based on a cranial-bone mimicking phantom. We demonstrated the implementation of an epoxy resin-based phantom that allows exploration of thickness and porosity variations in bone. Additionally, plant seeds were utilized to recreate acoustic scattering effects. We consider both time- and frequency-domain signal features from pulse-echo mode ultrasound measurements to explore the relationships with the physical parameters of cranial bone. Furthermore, we evaluate and discuss the important features of the acoustic signal that can be utilized to extract cranial thickness and porosity without physically accessing the bone cross section. This approach can be utilized toward the development of an effective aberration correction method.