Frequency dependence of attenuation and backscatter coefficient of ex vivo human lymphedema dermis
- 27 Downloads
Radio-frequency (RF) signals from the most dominant scatterer in a dermis, i.e., collagen fibers, are collected as backscattered signals. We aim to confirm the frequency dependence of the spatial distribution of features in ultrasound images, as well as the attenuation coefficient (AC) and backscatter coefficient (BSC) of skin tissue without [LE (−)] and with lymphedema [LE (+)].
Measurement samples (n = 13) were excised from human skin tissue with LE (−) and middle severity LE (+). A laboratory-made scanner and single-element concave transducers (range 9–47 MHz) were used to measure RF data. A localized AC was computed from the normalized power spectrum using the linear least squares technique. The reflector method and compensation technique of the attenuation of tissue were applied to calculate the BSC. In addition, effective scatterer diameter (ESD), effective acoustic concentration (EAC), and integrated BSC (IBS) were calculated from the BSC as the benchmark to differentiate LE (−) and LE (+) tissues.
High-frequency ultrasound displayed different echogenicity and texture compared between LE (−) and LE (+) in all transducers. The AC for LE (−) (0.22 dB/mm/MHz) and LE (+) (0.29 dB/mm/MHz) was comparable. BSC in LE (−) and LE (+) increased linearly with each transducer. The difference of intercept of the BSC between LE (−) and LE (+) indicated that both EAC and IBS of LE (+) were higher than that of LE (−). In contrast, ESD correlated with the slope of the BSC demonstrated the same tendency for both LE (−) and LE (+). These tendencies appeared for each transducer independent of the frequency bandwidth.
Frequency independence of AC and BSC in LE (−) and LE (+) was confirmed. Several 9- to 19-MHz ultrasound beams are sufficient for BSC analysis to discriminate LE (−) and LE (+) in terms of the penetration depth of the ultrasound.
KeywordsAttenuation coefficient Backscatter coefficient Frequency dependence Lymphedema Dermis
This work was partly supported by the JSPS Core-to-Core Program (A. Advanced Research Networks) and KAKENHI Grant Numbers 17H05280 and 17J07762. We also acknowledge financial support from the Institute for Global Prominent Research and the Frontier Science Program of Graduate School of Science and Engineering at Chiba University. We would like to express our gratitude to Professor Ichiro Manabe and Dr. Noriko Yamanaka with respect to histopathological findings.
Compliance with ethical standards
Conflict of interest
The authors declare that there are no conflicts of interest.
Human rights statements and informed consent
All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1964 and later versions. Informed consent was obtained from all patients for being included in the study. Additional informed consent was obtained from all patients for which identifying information is included in this article.
- 13.Lin Y-H, Huang C-C, Wang S-H. In vivo assessment of inflammatory skin using high frequency ultrasound image and quantitative parameters. In: 2010 IEEE international ultrasonics symposium. San Diego: IEEE; 2010. p. 2311–4.Google Scholar