Mobile echoes in liver cysts: a form of range-ambiguity artifact.

PURPOSE: Faint moving echoes are occasionally encountered in large hepatic cysts, as an example of range-ambiguity artifacts. The aim of this article is to describe the pattern of these intracystic mobile echoes, to analyze the mechanism of their formation, and to discuss options to clear them. METHODS: We analyzed the size and location of the hepatic cysts, the movement of the artifactual echoes, and the relationship between pulse repetition frequency (PRF) and the depth of these intracystic mobile echoes in 10 cases. In three cases examination at a lower PRF was made to ascertain whether the artifactual echoes would disappear. RESULTS: Intracystic range-ambiguity echoes appeared when the heart was located distal to the hepatic cyst and these echoes moved according to cardiac motion. The depth of the intracystic artifacts changed according to the PRF and they disappeared at a low PRF. CONCLUSION: Intracystic range-ambiguity artifacts are caused by an erroneous display of the returning echoes from the heart. Knowledge of the mechanism and appearance of this artifact helps prevent misdiagnosis of internal echoes in large hepatic cysts. Observation at different PRFs is key to recognizing this artifact, and examination at lower PRFs should be done to confirm the artifactual nature of the echoes.

Measuring medium-sized muscular arteries using a novel broadband 15-MHz linear array probe.

We recently developed a wideband 15-MHz linear array probe (15 M) with a band width of 8 MHz (9-17 MHz). Both axial and lateral resolution of 15 M, evaluated using a phantom model, were better than those of the current 10-MHz linear probe. To compare interobserver variability in measurement of medium-sized muscular arteries acquired using a 7.5-MHz linear probe (7.5 M), a 10-MHz linear probe (10M) and 15 M, two observers independently acquired images of the brachial and radial arteries, and measured the diameter and intima-media thickness (IMT) of those arteries in 17 male volunteers. Intraobserver variability in determining percent flowmediated dilatation (%FMD) was assessed in the same subjects using 15 M. Coefficients of variation (CV) in arteries measured using 7.5 M, 10 M, and 15 M were 7.0%, 2.5%, and 1.5%, respectively, for the diameter of the brachial artery; 10.3%, 5.8%, and 3.2%, respectively, for the diameter of the radial artery; and 17.0%, 13.8%, and 8.5%, respectively, for IMT of the far wall of the brachial artery. The CV of measurement of %FMD was 4.6%. The new 15-MHz probe thus warrants use in evaluating morphology and function of muscular arteries of medium size.