Masaaki Omura1, Kenji Yoshida2, Shinsuke Akita3, Tadashi Yamaguchi4. 1. Graduate School of Science and Engineering (Frontier Science Program), Chiba University, 1-33 Yayoicho, Inage, Chiba, 2638522, Japan. m.omura@chiba-u.jp. 2. Center for Frontier Medical Engineering, Chiba University, 1-33 Yayoicho, Inage, Chiba, 2638522, Japan. 3. Department of Plastic, Reconstructive, and Aesthetic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo, Chiba, 2608670, Japan. 4. Center for Frontier Medical Engineering, Chiba University, 1-33 Yayoicho, Inage, Chiba, 2638522, Japan. yamaguchi@faculty.chiba-u.jp.
Abstract
PURPOSE: 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 (+)]. METHODS: 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. RESULTS: 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. CONCLUSION: 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.
PURPOSE: 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 (+)]. METHODS: 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. RESULTS: 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. CONCLUSION: 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.
Entities:
Keywords:
Attenuation coefficient; Backscatter coefficient; Dermis; Frequency dependence; Lymphedema