Speckle in Ultrasound Computerized Reflection Mode Tomography

Abstract

Soon after the first use of Ultrasound B-Scanners, a phenomenon was observed in the images of texture, which has been under investigation up to now: Macroscopic homogeneous texture areas are represented in the B-Scan-images not as a single homogeneous grey-level, but as very “granular” areas with characteristic “granule-size”. This phenomenon is commonly called “speckle”. Several different approaches were done to investigate this problem. Two of them, the analytical statistical methods of Burckhardt /3/and Wagner et al. /4/, are extended in this paper in order to investigate speckle in ultrasound computerized reflection mode tomography (UCTR). UCTR can be explained as a numerical superposition of several B-Scans of a cross-sectional plane obtained from different aspect angles. The superposition consists of a summation and an additional inverse filtering procedure, which is equivalent to the deconvolution in X-ray-CT. UCTR has been investigated theoretically (/1/, /2/) and has also been used for clinical in-vivo imaging of female breast /5/, muscles, and thyroid gland /2/. Section 2 summarizes the theory of UCTR. Section 3 shortly reviews the results of speckle in B-Scans from Burckhardt /3/ and Wagner et al. /4/ Sections 4, 5 and 6 presents results of first and second order statistics of speckle in the summation image, and shows measurements of correlation-coefficients of two B-Scans with different aspect-angles.