Functional Photoacoustic and Ultrasonic Assessment of Osteoporosis: A Clinical Feasibility Study
Multiwavelength PA measurement of the optical absorption spectrum of the trabecular bone in the human calcaneus in vivo. (a) The relative optical absorption spectra of the calcaneus bones calculated from multiwavelength PA measurements from the control group () and the osteoporosis group (), respectively, each normalized at 800 nm wavelength. The solid curves show the average over the subjects in each group, and the shadow shows the standard deviation at each wavelength. (b) The optical absorption spectra of different chemical components in the trabecular bone, including deoxy-hemoglobin (Hb), oxy-hemoglobin (HbO2), lipid, and hydroxyapatite, which are the major contributors to the optical absorption of the trabecular bone in the optical spectrum of 690-950 nm. (c) The fitted optical absorption spectra from spectral unmixing by using the least-square regression method compared to the measured optical absorption spectra from an osteoporosis patient and a control volunteer, respectively. The quantified correlations were 0.97 and 0.99, respectively. (d) The spectral unmixing results showing the relative contents of hydroxyapatite, lipid, Hb, HbO2, and blood (i.e., Hb + HbO2), as well as the blood oxygen saturation (SaO2), of the two groups. stands for in unpaired -tests comparing the results from the two subject groups ( for osteoporosis group, for control group).
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