ABSTRACT
BACKGROUND/AIM: Recognition of the limitations of liver biopsies has led to the need for non-invasive tests to assess liver fibrosis from intensity and kinetic point of views. The aim of the present study was to evaluate non-invasive ultrasonic tissue characterization for the continuous monitoring of this process in mice. METHODS: Twelve-week-old male and female C57Bl6/J mice were submitted to repetitive carbon-tetrachloride (CCl4) intraperitoneal injections during 8 weeks or analysed 28 days after common bile duct ligation (BDL). The extent and kinetic of the disease progression were followed by the measurement of ultrasound backscatter intensity. This was compared with histological and blood parameter analysis. RESULTS: CCl4 induced a progressive increase in in vivo liver tissue backscatter intensity in both males and females. This increase was mainly correlated with interstitial fibrosis and, to a lower extent, with nuclear surface of the hepatocytes. A similar result was found after BDL. CONCLUSIONS: These data demonstrate for the first time in a systematic study that ultrasound tissue characterization can be used as a reliable tool to follow liver remodelling in mice continuously.
Subject(s)
Collagen/metabolism , Liver Cirrhosis/diagnostic imaging , Liver/diagnostic imaging , Ultrasonography/methods , Animals , Bile Ducts/surgery , Carbon Tetrachloride , Disease Models, Animal , Disease Progression , Female , Image Interpretation, Computer-Assisted , Ligation , Liver/metabolism , Liver/pathology , Liver Cirrhosis/blood , Liver Cirrhosis/chemically induced , Liver Cirrhosis/metabolism , Liver Cirrhosis/pathology , Male , Mice , Mice, Inbred C57BL , Reproducibility of Results , Time FactorsABSTRACT
OBJECTIVE: To explore the potential advantages of tissue harmonic imaging (THI) versus fundamental frequency imaging (FFI) when applied to tissue characterization. METHODS: A Philips Medical Systems Sonos 5500 echocardiograph equipped with a broadband transducer (S4) and an on-line quantitative analysis software package (Acoustic Densitometry) was used for imaging. The effect of mechanical index (MI), imaging depth, and anisotropy on relative backscatter amplitude was evaluated. RESULTS: This study demonstrated that imaging with tissue harmonics generated relatively greater backscatter values at clinically relevant imaging depths and instrument settings referenced to FFI. This effect was dependent on MI setting. A direct relationship between backscatter amplitude and MI was demonstrated. Additionally, tissue anisotropy had similar effects on integrated backscatter amplitude during both THI and FFI. However, relative backscatter values at each fiber orientation are greater during THI at similar instrument settings when referenced to FFI. CONCLUSION: Tissue harmonic imaging may offer advantages over FFI for myocardial tissue characterization.
Subject(s)
Echocardiography/methods , Tendons/diagnostic imaging , Animals , Anisotropy , Cattle , Heart , Image Processing, Computer-Assisted , Phantoms, ImagingABSTRACT
Myocardial tissue characterization has been performed using various ultrasonic techniques, one of which is the cyclic variation of integrated backscatter, a method that analyzes the acoustic properties of the myocardium using backscattered radiofrequency signals to provide information about myocardial structure and function. Previous studies using prototype equipment have demonstrated a reduction in the cardiac cycle variation of integrated backscatter in various pathologic states. Recently, a commercially produced software package that allows online analysis of cyclic variation of integrated backscatter has been made available for testing by various investigators. To evaluate this new commercially produced software, we compared integrated backscatter results in three groups of patients: a control group; an end-stage cardiomyopathy group; and a heart transplant recipient group. Integrated backscatter of the septum and posterior walls in the parasternal long axis and 12, 3, 6, and 9 o'clock regions in the short axis was performed using a commercially produced program (Hewlett-Packard Sonos 1500). In the control group, the mean cyclic variation of integrated backscatter was 5.04 +/- 1.60 dB in the septum and did not significantly vary from the rest of the regions studied. In comparison, cyclic variation of integrated backscatter in every region studied was reduced in the cardiomyopathy and heart transplant groups. Intraobserver variability, interobserver variability, and reproducibility over a 3-month interval was found to be 6.5%, 5.7%, and 7.5%, respectively. These results indicate that: (1) online analysis of cardiac cyclic variation of integrated backscatter is possible utilizing commercially produced software; (2) results obtained are consistent with a low intraobserver and interobserver variability and are reproducible over time; and (3) as observed in the comparison between the transplant and control groups, this information may detect changes in cardiac structure even in the absence of changes in function. (ECHOCARDIOGRAPHY, Volume 13, May 1996)
