Greenleaf James F., Chen Shigao, Sanchez William, Callstrom Matthew, Gorman Brian, Lewis Jason, Sanderson Schuyler

James F. Greenleaf, Shigao Chen, William Sanchez, Matthew Callstrom, Brian Gorman, Jason Lewis, Schuyler Sanderson

Mayo Clinic, USA

キーワード :

【Purpose】
To investigate the value of viscosity measured by ultrasound for liver fibrosis staging and to study the impact of neglecting viscosity in ultrasound analysis on performance of fibrosis staging.
【Materials and Methods】
The study was approved by an institutional review board, and informed consent was obtained from each subject. We studied healthy volunteers （8 females and 2 males, age 27〜55） and liver patients （17 females and 18 males, age 19〜74）. The patients had liver biopsy and along with the volunteers, were studied using ultrasound elasticity measurements （within six months of liver biopsy for patients）. SDUV （Shearwave Dispersion Ultrasound Vibrometry） was used to acquire mechanical properties. Elasticity and viscosity were determined by evaluating dispersion of shear wave propagation phase velocity, and by TTP （Time To Peak） group velocity. Elasticity alone was estimated from the effective shear group velocity. The fibrosis stage in biopsied patients was assessed histologically with the METAVIR scores. The correlation of elasticity and viscosity was assessed by Pearson correlation coefficient. The performances of SDUV and TTP were evaluated with receiver operating characteristic （ROC） curve analysis.
【Results】
Significant correlations were found between elasticity and viscosity measured by SDUV （Pearson correlation coefficient r=0.77, P < 0.001）, and elasticity measured by SDUV and TTP （Pearson correlation coefficient r=0.97, P < 0.001）. The areas under the ROC curve for separating F0-F1 from F2-F4 were 0.98 for elasticity measured by SDUV, 0.86 for viscosity measured by SDUV, and 0.95 for elasticity measured by TTP.
【Conclusion】
Our preliminary results suggest that elasticity and viscosity measured between 100 Hz and 400 Hz using SDUV are correlated, and that neglecting viscosity in TTP elasticity measurements may not substantially degrade the performance of ultrasound based elasticity measurements in liver fibrosis staging. However visco-elasticity calculated from SDUV gave larger area under the ROC curve.