Quantitative analysis of cetacean skin from different species using high frequency ultrasound

• Main Authors: Shin-ShianYeh, 葉信賢
• Other Authors: Shyh-Hau Wang
• Format: Others
• Language: en_US
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/8232wh

碩士 === 國立成功大學 === 資訊工程學系 === 107 === Marine mammal, cetacean, have been interest by human for centuries. In the 17th,18th century, whaling is an important economic activity and whaling watching, protection provide other value until late 20th century. In the past research of cetacean skin, skin is affected by environment, nutritional status and internal tissue condition. The layers of cetacean skin are classified as epidermis and blubber which contains dermis and subcutis and different individuals have significance variance (e.g., composition of epidermis and concentration of adipose tissue). Most of the results are analyzed by electron microscopy and slice staining. In view of past researches analying on skin by ultrasound, ultrasound is good at non-invasive diagnosis, fast and cost-effective scanning. But focal region is a big problem on ultrasound imaging because of resolution and noise effect. Therefore, in this study, surface skimming is used to overcome beyond focal region. A high frequency ultrasound, which is equipped 25 MHz transducer is used to measure different body parts (position 3,4,5,6) of Pygmy killer whale, Dwarf sperm whale and Fraser’s dolphin. The experiment is based on depth from surface and use sound speed, attenuation, Integrated backscatter (IB), Nakagami parameter for characterization. Results show that the signal to noise ratio (SNR) of rf signal from steel using horizontally scanning are 24.63 at 20.6 mm and 20.25 at 22.8 mm. The SNR of rf signal from steel using surface skimming are 24.51 at 20.6 mm and 24.62 at 22.8 mm. The artifact effect using surface skimming is not more obvious than horizontally scanning. The sound speed of Pygmy killer whale decrease as depth increase and attenuation at depth 1.5 mm and 2 mm is higher than 10 dB/mm compared with 0.5 mm and 1 mm. Nakagami parameters shows increasing trend as depth increase. Sound speed of Dwarf sperm whale position 3 at depth 1 mm is higher than position 4, however, depth 0.5 mm, 1.5mm, 2 mm at position 3 are lower than position 4. Attenuation coefficient increase as depth increase but progressive growth compared with Pygmy killer whale and Fraser’s dolphin which is clearly separated at depth 9 mm. Nakagami parameter increase from 0.5 mm to 1.5 mm and decrease from 1.5 mm to 2 mm. Speed sound of Fraser’s dolphin decrease slowly as depth increase. Attenuation is higher than 15 dB/mm from 1.5 mm and 0.5 mm, 1 mm are lower than 10 dB/mm. Nakagami parameter have the same trend as Dwarf sperm whale decreasing from 1.5 mm to 2 mm and increasing from 0.5 mm to 1.5 mm. The IB of three species have the decreasing trend which is undetermined that be caused by attenuation or composition of tissue. And compensation of frequency-dependent power spectra is not ideal because of inhomogeneity of tissue and noise effect. In this study, thickness of epidermis, concentration of adipose tissue and sampling position can be determined by ultrasounonic parameters. The study indicate that it is feasible to characterize composition and structure of cetacean skin by ultrasound.