Significance: Frequency domain diffuse optical spectroscopy (FD-DOS) uses intensity modulated light to measure the absorption and reduced scattering coefficients of turbid media such as biological tissue. Some FD-DOS instruments utilize a single modulation frequency, whereas others use hundreds of frequencies. The effect of modulation frequency choice and measurement bandwidth on optical property (OP) extraction accuracy has not yet been fully characterized. Aim: We aim to assess the effect of modulation frequency selection on OP extraction error and develop a high-speed look-up table (LUT) approach for OP estimation. Approach: We first used noise-free simulations of light transport in homogeneous media to determine optimized iterative inversion model parameters and developed a new multi-frequency LUT method to increase the speed of inversion. We then used experimentally derived noise models for two FD-DOS instruments to generate realistic simulated data for a broad range of OPs and modulation frequencies to test OP extraction accuracy. Results: We found that repeated measurements at a single low-frequency (110 MHz) yielded essentially identical OP errors as a broadband frequency sweep (35 evenly spaced frequencies between 50 and 253 MHz) for these noise models. The inclusion of modulation frequencies >300 MHz diminished overall performance for one of the instruments. Additionally, we developed a LUT inversion algorithm capable of increasing inversion speeds by up to 6 × , with 1000 inversions / s and ∼1 % error when a single modulation frequency was used. Conclusion: These results suggest that simpler single-frequency systems are likely sufficient for many applications and pave the way for a new generation of simpler digital FD-DOS systems capable of rapid, large-volume measurements with real-time feedback.

中文翻译：

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频域漫射光谱的调制频率选择和高效查表反演

意义：频域漫反射光谱 (FD-DOS) 使用强度调制光来测量混浊介质（如生物组织）的吸收和减少的散射系数。一些 FD-DOS 仪器使用单个调制频率，而其他仪器使用数百个频率。调制频率选择和测量带宽对光学特性 (OP) 提取精度的影响尚未完全表征。目的：我们旨在评估调制频率选择对 OP 提取误差的影响，并开发一种用于 OP 估计的高速查找表 (LUT) 方法。方法：我们首先使用均质介质中光传输的无噪声模拟来确定优化的迭代反演模型参数，并开发了一种新的多频 LUT 方法来提高反演速度。然后，我们将实验得出的噪声模型用于两个 FD-DOS 仪器，为广泛的 OP 和调制频率生成逼真的模拟数据，以测试 OP 提取精度。结果：我们发现，对于这些噪声模型，在单个低频 (110 MHz) 上的重复测量产生了与宽带频率扫描（50 到 253 MHz 之间的 35 个均匀间隔频率）基本相同的 OP 误差。包含大于 300 MHz 的调制频率会降低其中一台仪器的整体性能。此外，我们开发了一种 LUT 反演算法，能够将反演速度提高多达 6 倍，当使用单个调制频率时，反演速度为 1000 次/秒，误差约为 1%。结论：