Ultrasonic characterization of the transmural tissue structure of human scalp

The goal of the present study is to measure the ultrasonic properties of different layers of the human scalp. Sixty-four formalin fixed specimens were prepared from the left hemisphere of four human scalp donors from the frontal, parietal, occipital, and temporal regions and in either the polar or azimuthal direction. Ultrasonic measurements were performed with the transmural axis of the specimen perpendicular to the ultrasound beam. Measurements were performed in a water tank at room temperature (19-22°C) with a broadband 25 MHz single-element transducer (Model V324, Panametrics, Waltham, MA, USA; element diameter 6.35 mm, focal length of 25.4 mm, and a beam diameter of 0.25 mm at the focus) to create parametric images of the speed of sound (SOS), frequency slope of attenuation (FSA), apparent integrated backscatter (AIB), integrated attenuation coefficient (IAC), and integrated backscatter coefficient (IBC) in a plane containing the transmural axis. Thirty-two specimens from the right hemispheres were prepared and used to acquire conventional B-mode images to visualize the layered structure of the scalp. Images were acquired with a laptop-based ultrasound system (Terason T3000, Burlington, MA) equipped with a linear array transducer (12L5). The transducer was attached to a motorized linear slide that moved the transducer horizontally over the specimen while a video (cine-loop) was acquired. Each B-mode video consisted of several (>100) frames with a transducer displacement of approximately 0.2 mm between frames.本研究旨在测量人类头皮各层级的超声特性。本研究从4位头皮供体的左侧半球取材，制备了64份福尔马林固定标本，取材区域覆盖额、顶、枕、颞头皮区，采集方向涵盖极向或方位角方向。超声测量时，标本的透壁轴与超声束保持垂直。本次测量在室温（19~22℃）的水槽中开展，采用宽带25 MHz单阵元换能器（型号V324，帕纳梅特公司（Panametrics），美国马萨诸塞州沃尔瑟姆；阵元直径6.35 mm，焦距25.4 mm，焦点处束径0.25 mm），以在包含透壁轴的平面内生成声速（speed of sound, SOS）、衰减频率斜率（frequency slope of attenuation, FSA）、表观综合背散射（apparent integrated backscatter, AIB）、综合衰减系数（integrated attenuation coefficient, IAC）及综合背散射系数（integrated backscatter coefficient, IBC）的参数化图像。另制备32份取自同4位头皮供体右侧半球的标本，用于采集常规B-mode（B型超声）图像以可视化头皮的层级结构。图像采集采用基于笔记本电脑的超声系统（Terason T3000，美国马萨诸塞州伯灵顿），该系统搭载线阵换能器（12L5）。将换能器安装于电动线性滑轨上，可使换能器在标本上方水平移动，同时采集视频（cine-loop）。每段B-mode视频包含百余帧（>100）画面，帧间换能器位移约为0.2 mm。