Quantitative comparison of two distinct echogenic structures appearing on the same image using gain-assisted...

Gain-assisted densitometric evaluation of sonograms with two distinct echogenic structures appearing on each image was performed to establish if their density-gain setting curves have similar inclinations. We used the breast model (n = 67) in which hyperechoic masses were compared to the surrounding hyperechoic tissue at the optimal gain (Gopt) and at Gopt + 5. Both structures had significantly different film-corrected densities and showed a linear decline of density as the system gain increased from Gopt - 5 to Gopt + 5. The least squares regression lines were almost parallel. The density-gain unit decrease from Gopt - 5 to Gopt was not different, but the decrease from Gopt to Gopt + 5 reached statistical significance. The data suggest that skewed values are theoretically possible in comparing two distinct echogenic structures. However, within the gain intervals used in GADES, these differences are negligible and comparisons are as accurate as with the assessment of a single echogenic structure.