Roumeliotis Michael, Ephrat Pinhas, Patrick John, Carson Jeffrey J L
Imaging Program, Lawson Health Research Institute, St. Joseph's Health Care, 268 Grosvenor St., London, Ontario, N6A 4V2, Canada.
Opt Express. 2009 Aug 17;17(17):15228-38. doi: 10.1364/oe.17.015228.
Photoacoustic imaging is a modality which makes use of the contrast provided by optical imaging techniques and the spatial resolution and penetration depth similar to acoustic imaging modalities. We have developed a method for fast 3D photoacoustic imaging using a sparse hemispherical array of transducers. Such a system requires characterization of the transducer's response to an ideal point source in order to accurately reconstruct objects in the imaging volume. First, an attempt was made to design an ideal photoacoustic point source via a combination of liquids which would appropriately scatter and absorb the light such that a spherical distribution was achieved. Methylene blue (MB(+)) was used as the primary optical absorber while Intralipid (IL) was used as the liquid responsible for the optical scatter. A multitude of combinations were tested and the signal uniformity was characterized. The combination of 200 microM MB(+) and 0.09% IL was found to produce the most uniform signal over the range of transducers in the hemispherical array. The liquid source was then characterized over a broader range of azimuthal and zenith angles where it was shown the azimuthal consistency was much greater than the stability seen in different zenith elevations. The source was then used in a calibration scan for an imaging volume of 40 x 40 x 40 mm(3). At 216 points evenly spaced in the imaging volume, parameters were recorded for signal amplitude, width, and time-of-flight. These calibration parameters could then be applied to an iterative reconstruction algorithm in an attempt to more accurately produce images.
光声成像是一种利用光学成像技术提供的对比度以及与声学成像模态相似的空间分辨率和穿透深度的成像方式。我们开发了一种使用稀疏半球形换能器阵列进行快速三维光声成像的方法。这样的系统需要表征换能器对理想点源的响应，以便准确重建成像体积中的物体。首先，尝试通过液体组合设计一个理想的光声点源，这些液体能够适当地散射和吸收光，从而实现球形分布。亚甲蓝（MB(+)）用作主要的光吸收剂，而脂质乳剂（IL）用作负责光散射的液体。测试了多种组合并对信号均匀性进行了表征。发现在半球形阵列中的换能器范围内，200 microM MB(+)和0.09% IL的组合产生的信号最均匀。然后在更宽的方位角和天顶角范围内对液体源进行表征，结果表明方位角一致性远大于不同天顶高度下的稳定性。然后将该源用于对40×40×40 mm(3)的成像体积进行校准扫描。在成像体积中均匀分布的216个点处，记录信号幅度、宽度和飞行时间等参数。然后可以将这些校准参数应用于迭代重建算法，以尝试更准确地生成图像。
