Blaney Giles, Sassaroli Angelo, Das Tapan, Fantini Sergio
Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford MA 02155, USA.
Jorhat Institute of Science and Technology, Chenijaan, Jorhat 785010, Assam, India.
Photonics. 2025 Jul;12(7). doi: 10.3390/photonics12070697. Epub 2025 Jul 10.
Self-calibrating and dual-slope measurements have been used in the field of diffuse optics for robust assessment of absolute values or temporal changes in the optical properties of highly scattering media and biological tissue. These measurements employ optical probes with a minimum of two source positions and a minimum of two detector positions. This work focuses on a quantitative analysis of the impact of errors in these source and detector positions on the assessment of optical properties. We considered linear, trapezoidal, and rectangular optode arrangements and theoretical computations based on diffusion theory for semi-infinite homogeneous media. We found that uncertainties in optodes' positions may have a greater impact on measurements of absolute scattering versus absorption coefficients. For example, a 4.1% and 19% average error in absolute absorption and scattering, respectively, can be expected by displacing every optode in a linear arrangement by 1 mm in any direction. The impact of optode position errors is typically smaller for measurements of absorption changes. In each geometrical arrangement (linear, trapezoid, rectangular), we identify the direction of the position uncertainty for each optode that has minimal impact on the optical measurements. These results can guide the optimal design of optical probes for self-calibrating and dual-slope measurements.
自校准和双斜率测量已用于漫射光学领域，以可靠地评估高散射介质和生物组织光学特性的绝对值或时间变化。这些测量采用至少具有两个光源位置和至少两个探测器位置的光学探头。这项工作重点对这些光源和探测器位置的误差对光学特性评估的影响进行定量分析。我们考虑了线性、梯形和矩形光极排列以及基于半无限均匀介质扩散理论的理论计算。我们发现，光极位置的不确定性对绝对散射系数与吸收系数测量的影响可能更大。例如，将线性排列中的每个光极在任何方向上移动1毫米，预计绝对吸收和散射的平均误差分别为4.1%和19%。对于吸收变化的测量，光极位置误差的影响通常较小。在每种几何排列（线性、梯形、矩形）中，我们确定了每个光极位置不确定性的方向，该方向对光学测量的影响最小。这些结果可为自校准和双斜率测量的光学探头的优化设计提供指导。
