University of Texas, Department of Biomedical Engineering, 107 W Dean Keeton, Austin, Texas 78712, USA.
J Biomed Opt. 2010 May-Jun;15(3):036013. doi: 10.1117/1.3431728.
Sinusoidally structured illumination is used in concert with a phantom-based lookup-table (LUT) to map wide-field optical properties in turbid media with reduced albedos as low as 0.44. A key advantage of the lookup-table approach is the ability to measure the absorption (mu(a)) and reduced scattering coefficients (mu(s) (')) over a much broader range of values than permitted by current diffusion theory methods. Through calibration with a single reflectance standard, the LUT can extract mu(s) (') from 0.8 to 2.4 mm(-1) with an average root-mean-square (rms) error of 7% and extract mu(a) from 0 to 1.0 mm(-1) with an average rms error of 6%. The LUT is based solely on measurements of two parameters, reflectance R and modulation M at an illumination period of 10 mm. A single set of three phase-shifted images is sufficient to measure both M and R, which are then used to generate maps of absorption and scattering by referencing the LUT. We establish empirically that each pair (M,R) maps uniquely to only one pair of (micro(s) ('),micro(a)) and report that the phase function (i.e., size) of the scatterers can influence the accuracy of optical property extraction.
正弦结构照明与基于体模的查找表 (LUT) 协同使用，可在低反射率低至 0.44 的混浊介质中映射宽场光学特性。查找表方法的一个主要优点是能够测量吸收 (μa) 和比当前扩散理论方法允许的更广泛的散射系数 (μs(')) 值范围。通过与单个反射率标准进行校准，LUT 可以从 0.8 到 2.4mm-1 以平均均方根 (rms) 误差 7% 提取 μs(')，并从 0 到 1.0mm-1 以平均 rms 误差 6% 提取 μa。LUT 仅基于两个参数的测量值，即照明周期为 10mm 时的反射率 R 和调制 M。一组三个相移图像就足以测量 M 和 R，然后通过参考 LUT 生成吸收和散射图。我们通过经验确定，每一对 (M,R) 仅映射到唯一一对 (μs('),μa)，并报告散射体的相位函数（即大小）会影响光学特性提取的准确性。
