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標題Title: Measurements of acoustic dispersion on calcaneus using spilt spectrum processing technique
作者Authors: 陳培展,Tainsong..等
上傳單位Department: 電機工程系
上傳時間Date: 2009-11-18
上傳者Author: 陳培展
審核單位Department: 電機工程系
審核老師Teacher: 陳培展
檔案類型Categories: 論文Thesis
關鍵詞Keyword: SSP; Velocity dispersion; Phase velocity; Ultrasound; Calcaneu
摘要Abstract: The speed of sound (SOS) has become a useful tool in osteoporosis assessment, since it represents a combination of density and compressibility
of bone tissue and should provide better information on bone quality and an estimate the fracture risk. In general, the speed of sound on
dispersive material, such as bone tissue, depends strongly on frequency. Therefore, a measurement of velocity dispersion magnitude (VDM)
might provide more important bone structure information than measurements of bone mineral density (BMD), SOS or broadband ultrasound
attenuation (BUA). To obtain the velocity dispersion magnitude requires a sequence of pulses that have a frequency that is different from
that used in conventional approaches. The measurement is complicated by the fact that pulse waveform will distort as the pulses propagate
through the frequency-dependent medium. Alternatively, the phase velocity and velocity dispersion measurements also can be obtained on
frequency-domain processing. However, the accuracy of those techniques is affected by the 2mπ ambiguity in the phase unwrapping process in
frequency domain. And the spectrum approach is highly dependent on the gating window selection in time domain signals. The time-domain
split spectrum processing (SSP) technique is proposed here to measure the phase velocity and the VDM. The SSP technique is also used to
measure the SOS and VDM of two commercial calcaneus phantoms. Simulation results are in good agreement with the preset parameters of
a model-based signal obtained using the SSP technique. In addition, in vitro SSP measurements agree with the manufacturer’s specifications
for two commercial calcaneus phantoms. The negative dispersion is also found in in vivo measurements on human heel. Finally, an approach
based on the time domain SSP technique has potential clinical applications for osteoporosis diagnosis.

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