J Opt Soc Am A Opt Image Sci Vis. 2024 Jun 1;41(6):1128-1139. doi: 10.1364/JOSAA.521238.
Photoacoustic (PA) spectroscopy is considered to be one of the most effective ways to measure the levels of hematocrit () and oxygenation saturation ( ) of blood, which are essential for diagnosing blood-related illnesses. This simulation study aims to investigate the impact of individual optical parameters, i.e., optical absorption coefficient ( ), scattering coefficient ( ), and anisotropy factor (), on the accuracy of this technique in estimating the blood properties. We first performed the Monte Carlo simulations, using realistic optical parameters, to obtain the fluence maps for various samples. The wavelengths of the incident light were chosen to be 532, 700, 1000, and 1064 nm. Thereafter, the -Wave simulations were executed, incorporating those fluence maps to generate the PA signals. The blood properties were obtained using the PA signals. We introduced variations in , , and ranging from -10 to +10, -10 to +10, and -5 to +1, respectively, at 700 and 1000 nm wavelengths. One parameter, at both wavelengths, was changed at a time, keeping others fixed. Subsequently, we examined how accurately the blood parameters could be determined at physiological hematocrit levels. A 10% variation in induces a 10% change in estimation but no change in determination. Almost no change has been seen for variation. However, a 5% (-5 to 0%) variation in the factor resulted in approximately 160% and 115% changes in the PA signal amplitudes at 700 and 1000 nm, respectively, leading to ≈125 error in hematocrit estimation and ≈14 deviation in assessment when nominal =70. It is clear from this study that the scattering anisotropy factor is a very sensitive parameter and a small change in its value can result in large errors in the PA estimation of blood properties. In the future, in vitro experiments with pathological blood (inducing variation in the parameter) will be performed, and accordingly, the accuracy of the PA technique in quantifying blood and will be evaluated.
光声（PA）光谱被认为是测量血液中红细胞压积（Hct）和氧饱和度（SpO2）水平的最有效方法之一，这些水平对于诊断血液相关疾病至关重要。本模拟研究旨在探讨单个光学参数，即光吸收系数（μa）、散射系数（μs）和各向异性因子（g）对该技术估计血液特性准确性的影响。我们首先使用实际光学参数进行蒙特卡罗模拟，以获得各种样本的荧光图。入射光的波长选择为 532、700、1000 和 1064nm。然后，执行 -Wave 模拟，将这些荧光图纳入其中以生成 PA 信号。使用 PA 信号获得血液特性。我们在 700nm 和 1000nm 波长下分别将 、 、和的变化范围从-10 到+10、-10 到+10 和-5 到+1 引入 1 个参数，每次改变一个参数，其他参数保持不变。随后，我们检查了在生理红细胞压积水平下，血液参数的确定精度。在两个波长下，μa 的 10%变化导致 Hct 估计值变化 10%，但 SpO2 确定值不变。对 μs 的变化几乎没有影响。然而，在 700nm 和 1000nm 时，g 因子的 5%（-5 到 0%）变化导致 PA 信号幅度分别增加约 160%和 115%，导致 Hct 估计值误差约为 125%，SpO2 评估值偏差约为 14%，当标称 g =70 时。从这项研究中可以清楚地看出，散射各向异性因子是一个非常敏感的参数，其值的微小变化会导致 PA 对血液特性的估计产生较大误差。在未来，将进行具有病理血液的体外实验（引起μa 参数变化），并相应地评估 PA 技术在量化血液 Hct 和 SpO2 方面的准确性。
