Ring Artifact Correction for Phase-Insensitive Ultrasound Computed Tomography

An algorithm was developed for the correction of ring artifacts in phase-insensitive ultrasound computed tomography attenuation images. Differences in the measurement sensitivity between the ultrasound transducer array elements cause discontinuities in the sinogram which manifest as rings and arcs in the reconstructed image. The magnitudes of the discontinuities are potentially time-varying and dependent on the attenuation being measured. The algorithm dynamically determines the measurement sensitivity of each transducer in the array during the scan by comparison with both the elements to its left and the elements to its right. Elements at either end of the array are corrected, assuming a zero-attenuation path. The two estimates of sensitivity are combined using a weighted mean similar to a Kalman filter. The algorithm was tested on simulated and experimentally acquired data. It was demonstrated to reduce the root-mean-square error (RMSE) of simulated images against ground-truth images by up to a factor of 50 compared with uncorrected images and to visibly reduce artifacts on images reconstructed from the experimentally acquired data.