Use of phase diversity and modified phase congruence for edge enhancement in ultrasonic imaging

Abstract

Enhancement of boundaries is essential for the classification of suspicious regions in ultrasonic medical B scan images of internal organs so that malignancies can be identified and detected. Phase congruence has been suggested as a means to delineate the boundaries in images. Estimation of phase congruence requires the use of log-Gabor filters. In this work, spatial phase-only filters are used to generate the phase and magnitude information necessary for the estimation of phase congruence. Taking into account the multiplicative non-Rayleigh nature of speckle in these images, a modified version of phase congruence is used alongside pre-filtering with median filters to reduce speckle. Processing was undertaken on two computer-synthesized images and two B scan images of tissue-mimicking phantoms acquired using a commercial ultrasonic imaging unit. The results show that the modified phase congruence estimated after the filtering with four spatial phase-only filters enhances the boundaries of target-like regions in these images. Since these phase-only filters require fewer parameters than log-Gabor filters, the technique demonstrated in this work can provide a simple means to use phase congruence to highlight boundaries in ultrasonic images corrupted by speckle.