Ultrasonic properties of human scalp

The goal of this study was to characterize the ultrasonic properties of human scalp. Thirty-two specimens were prepared from formalin-fixed scalp tissue from four human donors (age 35–65, 2 male, 2 female). Tissue specimens were mounted in acrylic frames with a 30 × 30-mm acoustic window. The specimens were scanned in a water tank with a broadband ultrasound transducer with center frequency 7.5 MHz using a motion-controlled system. The ultrasonic region of interest (ROI) was a 20 × 20-mm region with a step size of 410 μm. The signals acquired were analyzed to determine the speed of sound (SOS) and frequency slope of attenuation (FSA) at all scan locations (2500 locations per specimen). The mean ± standard deviation (SD) of the SOS and FSA over all the specimens respectively was 1536 ± 9 m/s and 1.88 ± 0.51 dBcm-1MHz-1. The SD within an ROI was 3–15 m/s for SOS and 0.15–0.85 dBcm-1MHz-1 for FSA, depending on specimen, indicating some heterogeneity in the ultrasonic properties of the tissue.