Journal of Ultrasound in Medicine, Vol 13, Issue 9 675-678, Copyright © 1994 by American Institute of Ultrasound in Medicine

JOURNAL ARTICLE

The relation between different system gain settings and the accuracy of densitometric assessment of echogenicity

I. Blickstein and R. Goldman
Department of Obstetrics and Gynecology, Kaplan Hospital, Rehorot, Israel.

Two mathematical transformations of the measured density of a sonographic image of the fetal liver were used in 19 patients at nine different system gain settings (G) (optimal G number [dB] and optimal G number +/- 2, +/- 4, +/- 8, +/- 12). A significant correlation was found between the film-corrected density (Dcor) and gain interval from the optimal gain (Dcor = 1.39-0.052 [G interval], R = -0.81, P < 0.00001, 95% confidence limits = -0.052 +/- 0.052). After standardization of the values to the arbitrary G number of 49 (Dcor 49), a gain-independent convergence of the values was found. In 79% of the 19 cases the accuracy of the method was very high, as estimated from a small coefficient of variation. No significant difference was found in comparing the mean standardized densities derived from paired measurements (i.e., optimal G number +/- 2, +/- 4, +/- 8, and +/- 12). The data support background assumptions for the quantitative assessment or echogenicity by transmission densitometry and provide highly confident accuracy estimates.

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