In 81 cases of resected rectal cancer, quantitative analysis of B-mode ultrasonographic texture was studied in order to establish an ultrasonic tissue characterization of rectal cancer. A microcomputer-based system, interfaced with conventional diagnostic systems, was used for digital signal processing. The memory of the digital scan converter has 6-bit elements. The echo level of texture, which is the average amplitude of echo scattered back from the tissue, was compared between cancer and normal tissues. The echo level of rectal cancer tissue was significantly lower than that of the normal mucosal layer (p < 0.01). The echo level ratio was 0.7790 ± 0.0838 (mean ± S.D.). A high correlation of echo level was found between cancer tissue and the normal mucosal layer (r = 0.7367, p < 0.01). However, there was no significant difference between the echo level ratios of tissue of each histological type. Fixation with formaldehyde resulted in an equal increase in the echo levels of these tissues. It was demonstrated objectively and quantitatively that the echo level as an ultrasonic tissue characterization of rectal cancer was the lowest at the muscular layer and increased in the order of cancer, mucosal layer and subserosal layer. From these results, the author recommends that the obtained data should be applied to the clinical objective diagnosis of the spread of rectal cancer. This new method of ultrasonic tissue characterization is very useful.
digital signal processing