Four-dimensional photoacoustic imaging of moving targets

Photoacoustic imaging provides optical contrast with improved tissue penetration and spatial resolution compared to pure optical techniques. Three-dimensional photoacoustic imaging is particularly advantageous for visualizing non-planar light absorbing structures, such as blood vessels, internal organs or tumours. We have developed a fast 3-D photoacoustic imaging system for small animal research based on a sparse array of ultrasonic detectors and iterative image reconstruction. The system can acquire 3-D images with a single laser-shot at a frame rate of 10 Hz. To demonstrate the imaging capabilities we have constructed phantoms made of a scanning point source and a rotating line object and imaged them at a rate of 10 frames per second. The resulting 4-D photoacoustic images depicted well the motion of each target. Comparison of the perceived motion in the images with the known velocity of the target showed good agreement. To our knowledge, this is the first report of single-shot high frame-rate 3-D photoacoustic imaging system. With further developments, this system could bring to bear its inherent speed for applications in small animal research, such as motion tracking of tumour outline during respiration, and rapid monitoring of contrast agent kinetics. (C) 2008 Optical Society of America

与纯光学技术相比，光声成像具有光学对比度，且组织穿透性和空间分辨率都有所提高。三维光声成像在可视化非平面光吸收结构（如血管、内脏器官或肿瘤）方面尤其具有优势。我们基于超声探测器的稀疏阵列和迭代图像重建技术，为小动物研究开发了一种快速三维光声成像系统。该系统能够以10Hz的帧率单次激光激发获取三维图像。为了展示成像能力，我们构建了由扫描点源和旋转线物体组成的模型，并以每秒10帧的速率对其成像。所得到的四维光声图像很好地描绘了每个目标的运动。将图像中感知到的运动与目标已知速度进行比较，结果显示二者高度吻合。据我们所知，这是关于单次激发高帧率三维光声成像系统的首次报道。随着进一步的发展，该系统可利用其固有速度应用于小动物研究，比如呼吸过程中肿瘤轮廓的运动追踪以及造影剂动力学的快速监测。（C）2008美国光学学会