In vivo assessment of pulmonary edema and fibrosis in rats using separation of single and multiple scattering contributions and quantitative ultrasound

The application of spectral quantitative ultrasound (QUS) and envelope statistical methods to lung ultrasound is complicated due to the presence of multiple scattering (MS). In this study, the relationship between QUS assessment of lung disease and scattering regime was explored by applying QUS to lung ultrasound data, where the single scattering (SS) and MS components were separated. Data were acquired by a Verasonics Vantage ultrasound scanner from 15 healthy rats, 19 edematous rats, and 20 fibrotic rats. SS and MS components of the data were separated by a random matrix theory approach. Spectral QUS and envelope statistical parameters were then estimated from the SS and MS data separately. Initial results were obtained using the healthy and pulmonary edema data, where the extracted QUS parameters were correlated to the wet-to-dry (W/D) weight ratio, a gold standard measurement of edema. Several QUS parameters were significantly correlated to W/D ratio for both the SS and MS data, and the highest correlation coefficient was 0.53 using the SS data and 0.48 using the MS data. These results demonstrate the utility of QUS for assessing lung disease and provide further insight on the effects of SS and MS on spectral QUS and envelope statistical parameters.