Quantitative assessment of sonographic image echogenicity by transmission densitometry: fetal liver model

Abstract

A mathematical method is proposed to compare density values of different sonographs of the same tissue. Two transformations were needed: (1) calibration of the gray scale according to the maximal range of scanning for a given tissue, and (2) comparison of the effect of two time‐compensated gains on the difference in density and standardizing this effect to an arbitrary gain. To verify these relationships, 12 fetal livers were scanned at 38 weeks' gestation, at three different gains corresponding to the optimal gain and to the minimal and maximal gains that allowed a clear image to be obtained. After the mathematical transformations, the initially completely different densities were nearly identical (t‐test: P = 0.9998; Wilcoxon test: P > 0.5; Pearson's R = 0.8933). This method permits an accurate quantitative assessment of the echogenicity of any parenchymatous organ.

Computed Sonography: Requiem to Echogenicity Assessment?

“…The transmitted light was electrooptically measured, giving a digitalized reading of density (D, repro ducibility of 0.0ID). The films were standardized by calibrating the two extremes of the gray scale [5]. The fetal liver area was measured ten times at random locations through a 3-mm hole, and a mean den sity was calculated.…”

“…All the above were performed in 7 patients. In 10 patients, images were created at three low-contrast 2-D postprocessing curves (2,3,4) and at three high-contrast 2-D postprocessing curves (5,6,7) while all other parameters were kept constant. A hard copy of each image was produced by the AGFA matrix mini daylight processor (Mortsel, Belgium).…”

“…The purpose of this study was to evaluate the effect on image density of the following five features of computed sonography that can change the apparent image output: gain setting, log compression (LC), persis tence, preprocessing, and two-dimensional (2-D) postpro cessing [7], The gain control compensates for the loss of energy that otherwise occurs as the ultrasound beam passes deeper into homogeneous tissue. Any change of this control will significantly change the echo pattern [5,6,8], The LC function controls the gray-scale display of the image, thus, by increasing the LC, the image contains a wider dynamic range of echo amplitudes. The persis tence control is a form of frame averaging that adds 'histo ry' to the current image.…”

“…For example, changing the gain setting of conventional sono graphic machines results in a predictable change in image density, as measured by densitometry [5], This change may be used to standardize and compare images pro duced using different gain settings [6].…”

Quantitative comparison of two distinct echogenic structures appearing on the same image using gain-assisted densitometric evaluation of sonograms (GADES).

“…Recently, a method allowing quantitative assessment of sonographic image echogenicity by transmission densitometry was proposed. 4 This method, GADES, was based on the e 1995 by the American Institute of Ultrasound in Medicine • J Ultrasound Med 14~.$09-513, 1995 • 0278-4297/ 95/ $3.50 5t0 COMPARISON OF ECHOGE l C STRUCTURES assumption that a given tissue is expected to cause a specific change in the acoustic energy and, thus, the difference in densities is expected to correlate with the difference in the gain settings. This linear d~ crease in density as a function of increase in the system gain setting was confirmed in a subsequent study,s and the accuracy level.…”