COMPUTED SONOGRAPHY - REQUIEM TO ECHOGENICITY ASSESSMENT

We studied the influence of changes in gain settings, log compression, persistence, preprocessing, and postprocessing on image density in th e fetal liver model. Each parameter was studied while the others were held constant. The image density was objectively measured by electroop tical transmission densitometry using a transparent film output. Neith er the persistence nor the preprocessing levels significantly changed image density. Postprocessing of sonographic images produced significa nt differences (p < 0.02) in mean image density of most of the various postprocessing curves and is a serious confounder of tissue echogenic ity assessment. The data reconfirmed that there is a linear relationsh ip (r = -0.94 to -0.997) between image density and gain setting. Howev er, each log compression setting significantly changed (p < 0.0000001) this relationship, obviating possible image density calibration. Our data suggest that manipulation of image parameters by computed sonogra phic technology obviates accurate echogenicity assessment.