Multivariate analysis of peak density and attenuation parameters in ultrasonic data. (a) Non-rotated plot of attenuation vs. peak density. (b) Rotated and translated plot of attenuation vs. peak density, showing the use of parabolic and linear curves for the classification boundaries. F = fat necrosis - fibroadenoma - tubular adenoma. B = benign pathology. N = normal breast tissue. M = malignant breast tissue.