J Biomed Opt. 2014 Mar;19(3):36015. doi: 10.1117/1.JBO.19.3.036015.
This study examines the application of backscattered ultrasound (US) and photoacoustic (PA) signals for assessment of bone structure and density variations. Both methods were applied in the frequency-domain, employing linear frequency modulation chirps. A near-IR laser (800 nm) was used for inducing the PA signal. The backscattered pressure waves were detected with a 2.2-MHz US transducer. Experiments were focused on detection and evaluation of PA and US signals from in-vitro animal and human bones with cortical and trabecular sublayers. It was shown that PA signals can be detected as deep as a few millimeters below trabecular and cortical layers. The occurrence of multiple scattering was demonstrated in PA detected signals from cancellous bone. Osteoporotic changes in the bone were simulated by using a very mild demineralization ethylenediaminetetraacetic acid solution. Changes in the time-domain signals as well as integrated backscattering spectra were compared for the samples before and after demineralization. The results demonstrated the sensitivity of PA to variations in bone minerals. In comparison to PA, US was capable of generating detectable signals from deeper bone sublayers (few centimeters). However, while US signal variations with changes in the cortical layer were insignificant, PA proved to be sensitive even to minor variations of the cortical bone density.
本研究探讨了背散射超声（US）和光声（PA）信号在评估骨结构和密度变化中的应用。这两种方法都在频域中应用，采用线性调频啁啾。近红外激光（800nm）用于产生 PA 信号。背散射压力波由 2.2MHz 的 US 换能器检测。实验集中在检测和评估来自体外动物和人体骨骼的皮质和小梁亚层的 PA 和 US 信号。结果表明，PA 信号可以在小梁和皮质层下几毫米的深度被检测到。在来自松质骨的 PA 检测信号中证明了多次散射的发生。通过使用非常温和的脱矿质乙二胺四乙酸溶液模拟骨中的骨质疏松变化。比较了脱矿前后时域信号和积分背散射光谱的变化。结果表明，PA 对骨矿物质变化敏感。与 PA 相比，US 能够从更深的骨亚层（几厘米）产生可检测的信号。然而，虽然 US 信号随皮质层变化的变化不显著，但 PA 被证明对皮质骨密度的微小变化也很敏感。
