Journal of Ultrasound in Medicine, Vol 14, Issue 10 741-748, Copyright © 1995 by American Institute of Ultrasound in Medicine
Sonographic enhancement of renal cortex by contrast media
C. M. Sehgal, P. H. Arger and C. R. Pugh
Hospital of the University of Pennsylvania, Philadelphia, USA.
The purpose of this study was to evaluate whether a phase shift contrast
agent could enhance the renal cortex. Four doses of the contrast agent
EchoGen ranging from 0.25 to 0.65 ml/kg were injected intravenously in
three healthy dogs. Images of the kidney were recorded on a videotape
before and after each injection. The images were evaluated visually and
were computer-analyzed for brightness change caused by the contrast agent.
Marked changes in cortical brightness were observed at the doses of 0.45
and 0.65 ml/kg. At lower doses the changes in image brightness were
significantly reduced but measurable. The brightness peaked at 65 +/- 9
seconds after injection and gradually decreased to the baseline value in
approximately 12 minutes. The video density varied nonlinearly with dose,
and at low doses its value drifted below the baseline. This is believed to
be due to attenuation of echoes by the contrast agent. The results of this
study indicate that the microbubbles formed by phase shift contrast media
are sufficiently small and persist long enough to enhance sonographic
images of the cortex. Contrast media whose effect is based on the
phenomenon of phase shift permit enhancement of the gray scale
characteristic of the kidney. The enhancements last up to several minutes
and have strong potential to allow investigation of perfusion in kidney.
