Photoacoustic Quantitative Flow Estimation Using Gold Nanoparticles
Date Issued
2005
Date
2005
Author(s)
Wei, Chen-Wei
DOI
zh-TW
Abstract
In this research, photoacoustic imaging techniques using gold nanoparticles are investigated. Photoacoustic imaging is a newly developed imaging technique. It combines the high contrast resolution of optical imaging and high spatial resolution of ultrasound imaging. However, the applications of photoacoustic imaging to date focus mainly on morphological imaging. Thus, constructing a non-invasive, blood flow related functional imaging system is the goal of this research. In the first part of this study, at first a pulsed Nd-YAG laser of a wavelength at 532 nm is used for laser irradiation and an ultrasound transducer of center frequency 3.5 MHz is used for acoustic detection (wash-out analyses). Based on the indicator-dilution theory, 40 nm gold nanospheres are used as the contrast agent for photoacoustic imaging. The actual flow rates are 3 ml/sec, 2.14 ml/sec, 1.2 ml/sec, 0.61 ml/sec, 0.45 ml/sec, 0.33 ml/sec, and 0.23 ml/sec. The mixing chamber of 30 ml is used. The wash-out time-intensity curve (TIC) is obtained to estimate the flow rate. In the second part of this study, a pulsed Nd-YAG laser of wavelength 1064 nm is used for laser irradiation and an ultrasound transducer of center frequency 1 MHz is used for acoustic detection (wash-in analyses). Based on the destruction-replenishment model, gold nanorods of absorption peak at 1018 nm are used as the contrast agent. The wash-in TIC is obtained to estimate the flow rate. The actual flow rates are 0.283 cm/sec, 0.142 cm/sec, 0.071 cm/sec, 0.035 cm/sec and 0.018 cm/sec. The flow parameters derived from the TIC among different flows rate are compared. The correlation coefficients between the mean transmit time derived from the wash-out TIC and the theoretical values are above 0.97. And the correlation coefficients between flow rates calculated from the wash-in TIC and the real flow rates are all above 0.96. Although wash-out TIC and wash-in TIC methods can be used in different applications, the results show that the wash-out TIC method is affected by the effective volume of the mixing chamber and the assumption of bolus injection. In practical applications, these issues can be resolved by the wash-in TIC method. The linearity between the concentration and signal amplitude of gold nanoparticles and the properties of gold nanoparticles under the laser radiation are also discussed for their effects on flow rate measurements. Future works will focus on improving the sensitivity for in vitro and in vivo applications. In addition, the biocompatibility tests of gold nanoparticles will be performed.
Subjects
金奈米粒子
光聲影像
功能性影像
對比劑
稀釋定理
破壞-補充模型
時間-強度曲線
gold nanoparticles
photo-acoustic imaging
functional imaging
contrast agent
indicator-dilution theory
destruction-replenishment model
time-intensity curve
Type
thesis
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