Effect of ultrasound frequency on the Nakagami statistics of human liver tissues

• Published in: PloS one Vol. 12; no. 8; p. e0181789
• Main Authors: Tsui, Po-Hsiang, Zhou, Zhuhuang, Lin, Ying-Hsiu, Hung, Chieh-Ming, Chung, Shih-Jou, Wan, Yung-Liang
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.08.2017; Public Library of Science (PLoS)
• Subjects: Acoustics; Adult; Backscattering; Biopsy; Care and treatment; Coherent scattering; Correlation; Correlation analysis; Diagnosis; Echo surveys; Engineering and Technology; Fatty liver; Female; Fibrosis; Healthy Volunteers; Hepatitis; Humans; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; Image Processing, Computer-Assisted; Liver; Liver - diagnostic imaging; Liver - pathology; Liver biopsy; Liver cancer; Liver diseases; Magnetic resonance imaging; Male; Medical imaging; Medical Oncology - standards; Medicine and Health Sciences; Neoplasms - diagnostic imaging; Phantoms, Imaging; Physical Sciences; Rayleigh distribution; Research and Analysis Methods; Scattering, Radiation; Statistical analysis; Statistics; Steatosis; Tissues; Ultrasonic imaging; Ultrasonic methods; Ultrasonic testing; Ultrasonography; Ultrasound; Young Adult; Beijing China; China; Taiwan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0181789

The analysis of the backscattered statistics using the Nakagami parameter is an emerging ultrasound technique for assessing hepatic steatosis and fibrosis. Previous studies indicated that the echo amplitude distribution of a normal liver follows the Rayleigh distribution (the Nakagami parameter m is close to 1). However, using different frequencies may change the backscattered statistics of normal livers. This study explored the frequency dependence of the backscattered statistics in human livers and then discussed the sources of ultrasound scattering in the liver. A total of 30 healthy participants were enrolled to undergo a standard care ultrasound examination on the liver, which is a natural model containing diffuse and coherent scatterers. The liver of each volunteer was scanned from the right intercostal view to obtain image raw data at different central frequencies ranging from 2 to 3.5 MHz. Phantoms with diffuse scatterers only were also made to perform ultrasound scanning using the same protocol for comparisons with clinical data. The Nakagami parameter-frequency correlation was evaluated using Pearson correlation analysis. The median and interquartile range of the Nakagami parameter obtained from livers was 1.00 (0.98-1.05) for 2 MHz, 0.93 (0.89-0.98) for 2.3 MHz, 0.87 (0.84-0.92) for 2.5 MHz, 0.82 (0.77-0.88) for 3.3 MHz, and 0.81 (0.76-0.88) for 3.5 MHz. The Nakagami parameter decreased with the increasing central frequency (r = -0.67, p < 0.0001). However, the effect of ultrasound frequency on the statistical distribution of the backscattered envelopes was not found in the phantom results (r = -0.147, p = 0.0727). The current results demonstrated that the backscattered statistics of normal livers is frequency-dependent. Moreover, the coherent scatterers may be the primary factor to dominate the frequency dependence of the backscattered statistics in a liver.