This paper examines three boundary conditions commonly applied to the surface of a semi-infinite turbid medium in the context of radiative transfer and diffusion theory. The authors use the method of images to derive solutions for the partial-current and extrapolated-boundary conditions, finding that these two conditions have the same dipole and quadrupole moments. Consequently, the solutions to the diffusion equation under these conditions are nearly identical, with the extrapolated boundary solution approximately satisfying the partial-current boundary condition. This leads to a simplified and accurate method for extracting optical parameters from frequency-domain photon-migration (FDPM) data, which is computationally efficient. The paper also discusses the limitations of the zero-boundary condition, which violates the diffusion approximation and does not account for refractive index mismatches. The authors simulate phase and modulation data for all three boundary conditions, showing that the partial-current and extrapolated-boundary conditions yield results within 3% of each other, while the zero-boundary condition can lead to discrepancies of up to 14%. The authors conclude that the partial-current-extrapolated boundary approach is a robust and accurate method for analyzing FDPM data, especially when the tissue boundary is rigorously treated. They recommend this approach for noninvasive measurements of optically thick tissue.This paper examines three boundary conditions commonly applied to the surface of a semi-infinite turbid medium in the context of radiative transfer and diffusion theory. The authors use the method of images to derive solutions for the partial-current and extrapolated-boundary conditions, finding that these two conditions have the same dipole and quadrupole moments. Consequently, the solutions to the diffusion equation under these conditions are nearly identical, with the extrapolated boundary solution approximately satisfying the partial-current boundary condition. This leads to a simplified and accurate method for extracting optical parameters from frequency-domain photon-migration (FDPM) data, which is computationally efficient. The paper also discusses the limitations of the zero-boundary condition, which violates the diffusion approximation and does not account for refractive index mismatches. The authors simulate phase and modulation data for all three boundary conditions, showing that the partial-current and extrapolated-boundary conditions yield results within 3% of each other, while the zero-boundary condition can lead to discrepancies of up to 14%. The authors conclude that the partial-current-extrapolated boundary approach is a robust and accurate method for analyzing FDPM data, especially when the tissue boundary is rigorously treated. They recommend this approach for noninvasive measurements of optically thick tissue.