Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, Michigan, USA.
J Orthop Res. 2024 Mar;42(3):647-660. doi: 10.1002/jor.25702. Epub 2023 Oct 17.
Osteoporosis is a major public health threat with significant physical, psychosocial, and financial consequences. The calcaneus bone has been used as a measurement site for risk prediction of osteoporosis by noninvasive quantitative ultrasound (QUS). By adding optical contrast to QUS, our previous studies indicate that a combination of photoacoustic (PA) and QUS, that is, PAQUS, provides a novel opportunity to assess the health of human calcaneus. Calibration of the PAQUS system is crucial to realize quantitative and repeatable measurements of the calcaneus. Therefore, a phantom which simulates the optical, ultrasound, and architectural properties of the human calcaneus, for PAQUS system calibration, is required. Additionally, a controllable phantom offers researchers a versatile framework for developing versatile structures, allowing more controlled assessment of how varying bone structures cause defined alterations in PA and QUS signals. In this work, we present the first semi-anthropomorphic calcaneus phantom for PAQUS. The phantom was developed based on nano computed-tomography (nano-CT) and stereolithography 3D printing, aiming to maximize accuracy in the approximation of both trabecular and cortical bone microstructures. Compared with the original digital input calcaneus model from a human cadaveric donor, the printed model achieved accuracies of 71.15% in total structure and 87.21% in bone volume fraction. Inorganic materials including synthetic blood, mineral oil, intralipid, and agar gel were used to model the substitutes of bone marrow and soft tissue, filling and covering the calcaneus phantom. The ultrasound and optical properties of this phantom were measured, and the results were consistent with those measured by a commercialized device and from previous in vivo studies. In addition, a short-term stability test was conducted for this phantom, demonstrating that the optical and ultrasound properties of the phantom were stable without significant variation over 1 month. This semi-anthropomorphic calcaneus phantom shows structural, ultrasound, and optical properties similar to those from a human calcaneus in vivo and, thereby, can serve as an effective source for equipment calibration and the comprehensive study of human patients.
骨质疏松症是一种重大的公共健康威胁，会带来重大的身体、心理社会和经济后果。跟骨已被用作非侵入性定量超声（QUS）预测骨质疏松症风险的测量部位。通过在 QUS 中添加光学对比度，我们之前的研究表明，声辐射力脉冲（PA）和 QUS 的结合，即 PAQUS，为评估人类跟骨健康提供了新的机会。PAQUS 系统的校准对于实现跟骨的定量和可重复测量至关重要。因此，需要一个模拟人跟骨光学、超声和结构特性的仿体来进行 PAQUS 系统校准。此外，可控仿体为研究人员提供了一个通用框架，用于开发各种结构，从而可以更可控地评估不同的骨骼结构如何导致 PA 和 QUS 信号的定义性变化。在这项工作中，我们展示了第一个用于 PAQUS 的半拟人跟骨仿体。该仿体是基于纳米计算机断层扫描（nano-CT）和立体光刻 3D 打印技术开发的，旨在最大限度地提高对小梁骨和皮质骨微观结构的近似精度。与来自人体尸体供体的原始数字输入跟骨模型相比，打印模型在总结构和骨体积分数方面的精度分别达到了 71.15%和 87.21%。合成血液、矿物油、中链甘油三酯和琼脂凝胶等无机材料被用于模拟骨髓和软组织的替代品，填充和覆盖跟骨仿体。测量了该仿体的超声和光学特性，结果与商业化设备测量的结果以及之前的体内研究结果一致。此外，对该仿体进行了短期稳定性测试，结果表明，在 1 个月内，仿体的光学和超声特性稳定，没有明显变化。这个半拟人跟骨仿体具有与人活体跟骨相似的结构、超声和光学特性，因此可以作为设备校准和全面研究人类患者的有效来源。
