Investigation of Radiofrequency Ultrasound-Based Fibrotic Tissue Strain Imaging Method Employing Endogenous Motion.

ABSTRACT

OBJECTIVES: The paper presents the results of an initial clinical study, which were obtained using the strain elastography imaging method based on radio frequency ultrasound signal analysis. METHODS: The technique employs endogenous motion of the liver induced by beating heart and vascular pulsatility as an excitation source of tissue microdisplacement. The potential for fibrotic tissue characterization was demonstrated using a clinical data set of radio frequency ultrasound signals (23 healthy controls, 21 subjects with hepatitis, and 16 subjects with liver cirrhosis). Parametric maps, which represent the tissue strain, were derived from the gradient of the integrated spectral coefficient parameter, and correlations with the stage of liver disease were evaluated. Average endogenous strain derived from the gradient of the integrated spectral coefficient parameter and variability (standard deviation) of the strain were evaluated in the rectangular regions of interest (sizes, 1 × 1 and 2 × 2 cm) defined by the observer. The assessment of strain was performed in different frequency subbands of endogenous motion (0-10 Hz and 10-20 Hz). RESULTS: The best distinction between the groups was observed for the average strain derived from the gradient of the integrated spectral coefficient parameter the controls, 13.30 ± 6.62; hepatitis, 7.12 ± 7.45; cirrhosis, 3.95 ± 2.44 µm/cm (region of interest, 1 × 1 cm; frequency subband 0-10 Hz), and 10.48 ± 6.02, 8.27 ± 5.41, 3.89 ± 2.07 µm/cm, respectively (2 × 2 cm, 0-10 Hz). CONCLUSION: The investigated strain parameters showed statistically significant differences (P < .001) for the different stages of liver fibrosis in most of the cases and proved this method to be feasible.