Optical penetration inside human skin is constrained by the wavelength dependent scattering and absorption losses by tissue microstructure and chromophores. This computational study investigates whether the signature of hematocrit variation from plexus i.e., the first skin layer having very small blood volume percentage distributed in capillary vessels, is retained by the detected photoacoustic response. The in-silico skin phantom is irradiated by a light source equivalent to a small footprint and low power (below 5 W) continuous wave LASER diode. As the low fluence can be compensated by exploiting strong absorption by targeted chromophores (hemoglobin molecules), an irradiation of wavelength 405 nm has been used to generate detectable pressure from capillary blood vessels of plexus. Optical energy deposition inside the tissue has been modelled using Monte Carlo technique and the pressure wave is computed using k-wave. It is found that with the increase in hematocrit from 10% to 50%, photoacoustic amplitude monotonically increases and gets almost doubled. The increment is about 30% in the range of hematocrit of physiological interest (from 30% to 50%). The variation follows a quadratic relationship for the entire hematocrit range. This photoacoustic signature of hematocrit variation has further been validated against minimum detectable pressure (800 Pa). This numerical model is expected to be an important basis to realize the idea of low cost small footprint in-vivo photoacoustic hematocrit measurement device.

人体皮肤内的光穿透受到组织微结构和发色团的波长相关散射和吸收损失的限制。这项计算研究调查了来自丛的血细胞比容变化的特征，即在毛细血管中分布的血容量百分比非常小的第一皮肤层，是否被检测到的光声响应保留。计算机内皮肤模型由相当于小尺寸和低功率（低于 5 W）连续波激光二极管的光源照射。由于可以通过利用目标发色团（血红蛋白分子）的强吸收来补偿低能量密度，因此已使用波长 405 nm 的辐射从神经丛毛细血管产生可检测的压力。组织内的光能沉积已使用蒙特卡罗技术建模，压力波使用 k 波计算。发现随着血细胞比容从10%增加到50%，光声振幅单调增加，几乎翻了一番。在生理感兴趣的血细胞比容范围内（从 30% 到 50%），增量约为 30%。该变化遵循整个血细胞比容范围的二次关系。这种血细胞比容变化的光声特征已针对最小可检测压力 (800 Pa) 进行了进一步验证。该数值模型有望成为实现低成本小足迹理念的重要基础体内光声血细胞比容测量装置。