Incident angle-dependent gain correction for reflection images on ultrasound computed tomography

We are performing clinical studies on breast cancer examinations at Hokkaido University Hospital with an ultrasound computed tomography (USCT) system. Our studies have revealed that some reflection images exhibit intensity inhomogeneity because ultrasound waves, shot by a 1-D ring array transducer, go non-vertically into the object surface. This trend significantly increases the burden of interpretation. Therefore, we developed a calibration method to remove this heterogeneity based on the distribution of the incident angle of waves that are estimated from the slope of the subject surface morphologically extracted from multi-slice reflection images. Results showed that applying this correction method to clinical images enabled the image contrast and uniformity to be successfully recovered.