Department of Electrical and Computer Engineering, University of Alberta, 9107, 116 Street, Edmonton, Alberta T6G 2V4, Canada.
Photoacoustics. 2013 Dec 16;2(1):33-8. doi: 10.1016/j.pacs.2013.11.004. eCollection 2014 Mar.
OBJECTIVES: We analyze a reflection-mode multiple-illumination photoacoustic method which allows us to estimate optical scattering properties of turbid media based on fitting light-transport models and explore its limits in optical property estimation and depth-dependent fluence compensation. BACKGROUND: Recent simulation results show significant promise for a technique called multiple-illumination photoacoustic tomography (MI-PAT) to quantitatively reconstruct both absorption and scattering heterogeneities in turbid medium. Prior to experiments, it is essential to develop and analyze a measurement technique and probe capabilities of quantitative measurements that focus on sensing rather than imaging. METHODS: This technique involved translation of a 532 nm pulsed-laser light spot while focusing an ultrasound receiver on a sub-surface optical absorber immersed in a scattering medium at 3, 4 and 5 mm below the surface. Measured photoacoustic amplitudes for media with different reduced scattering coefficients are fitted with a light propagation model to estimate optical properties. RESULTS: When the absorber was located at 5 mm below the membrane in media with a reduced scattering coefficient of 4.4 and 5.5 cm(-1), the true values were predicted with an error of 5.7% and 12.7%, respectively. We observe accuracy and the ability of estimating optical scattering properties decreased with the increased reduced scattering coefficient. Nevertheless, the estimated parameters were sufficient for demonstrating depth-dependent fluence compensation for improved quantitation in photoacoustic imaging.
目的:我们分析了一种反射模式的多照明光声方法,该方法允许我们根据拟合光传输模型来估计混浊介质的光学散射特性,并探索其在光学特性估计和深度相关的光强补偿方面的局限性。
背景:最近的模拟结果表明,一种名为多照明光声断层扫描(MI-PAT)的技术在定量重建混浊介质中的吸收和散射异质性方面具有很大的潜力。在进行实验之前,开发和分析一种测量技术以及分析侧重于传感而不是成像的定量测量的探针能力是至关重要的。
方法:该技术涉及在聚焦超声接收器的同时平移一个 532nm 脉冲激光光斑,该接收器聚焦于一个浸入散射介质中的亚表面光吸收体,该吸收体位于表面以下 3、4 和 5mm 处。用光传播模型拟合具有不同散射系数的介质的测量光声幅度,以估计光学性质。
结果:当吸收体位于膜下 5mm 处,散射系数分别为 4.4 和 5.5cm(-1)时,真数值的预测误差分别为 5.7%和 12.7%。我们观察到,随着散射系数的增加,估计的准确性和估计光学散射特性的能力都降低了。然而,所估计的参数足以证明深度相关的光强补偿,以提高光声成像的定量能力。
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