Spatial calibration of a 3D ultrasound tomography system

We present a novel spatial calibration method for a 3D ultrasound computed tomography (USCT) system, designed to improve imaging accuracy without relying on costly high-precision manufacturing. The method utilizes time-of-flight measurements from water acquisitions. When applied to the KIT 3D USCT III system, the calibration detects misalignment such as rotated transducer array systems and considerably enhances image quality. Evaluation using a wire phantom demonstrates improved focus, contrast, and reduced point spread function in reconstructions. Although brute-force optimization of the sound speed substantially improves reconstructions obtained with uncalibrated data, the calibrated geometry still yields superior image quality. This approach offers a scalable and practical solution for high-resolution ultrasound imaging in clinical and research settings.