Computational calibration method for optical tomography

Abstract

We propose a computational calibration method for optical tomography. The model of the calibration scheme is based on the rotation symmetry of source and detector positions in the measurement setup. The relative amplitude losses and phase shifts at the optic fibers are modeled by complex-valued coupling coefficients. The coupling coefficients can be estimated when optical tomography data from a homogeneous and isotropic object are given. Once these coupling coefficients have been estimated, any data measured with the same measurement setup can be corrected for the relative variation in the data due to source and detector losses. The final calibration of the data for the source and detector losses and the source calibration between the data and the forward model are obtained as part of the initial estimation for reconstruction. The calibration method was tested with simulations and measurements. The results show that the coupling coefficients of the sources and detectors can be estimated with good accuracy. Furthermore, the results show that the method can significantly improve the quality of reconstructed images.

Recent advances in diffuse optical imaging

“…The technique has since been extended to allow small errors in optode position to be corrected (Stott et al 2003, Culver et al 2003c and has been used for dynamic breast imaging (Intes et al 2003). Vilhunen et al (2004) have implemented a related method which can be used when the sources and detectors have rotational symmetry. Oh et al (2002) used a Bayesian formulation to reconstruct 3D images non-linearly by treating the unknown source-detector coupling coefficients as unwanted 'nuisance' parameters.…”