A coordinate-robust parameter selection framework for backscattering Mueller matrix imaging

Computational Mueller matrix polarimetry holds great promise in biomedical studies and clinical applications, providing comprehensive polarization-related information within the sample. For backscattering polarimetry, the measured polarization basis parameters (PBPs) can be affected by the Cartesian coordinate transformation due to the vectorial properties of polarized light and the non-collinear characteristics of the measurement system. In this Letter, we propose a coordinate-robust parameter selection framework for backscattering Mueller matrix imaging. According to the dependency differences in Cartesian coordinate system transformation, we categorize the PBPs into photon coordinate system transformation invariants, azimuth rotation invariants, and azimuth orientation parameters. From anisotropic modulus and direction perspectives, we further investigate the influence mechanism of the Cartesian coordinate transformation on different polarization effects. The effectiveness of the proposed optimization strategy lies in introducing reasonable assumptions based on typical optical properties of tissues to refine PBPs calculations, thereby unifying computational outcomes across different coordinate systems. Our study provides a coordinate-robust parameter selection framework, improving the accuracy and reliability of backscattering MM imaging for in vivo applications.