Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, Department of Electrical Engineering, California Institute of Technology, Pasadena, CA, USA.
Nat Protoc. 2021 May;16(5):2381-2394. doi: 10.1038/s41596-020-00487-w. Epub 2021 Apr 12.
Photoacoustic tomography (PAT) has demonstrated versatile biomedical applications, ranging from tracking single cells to monitoring whole-body dynamics of small animals and diagnosing human breast cancer. Currently, PAT has two major implementations: photoacoustic computed tomography (PACT) and photoacoustic microscopy (PAM). PACT uses a multi-element ultrasonic array for parallel detection, which is relatively complex and expensive. In contrast, PAM requires point-by-point scanning with a single-element detector, which has a limited imaging throughput. The trade-off between the system cost and throughput demands a new imaging method. To this end, we have developed photoacoustic topography through an ergodic relay (PATER). PATER can capture a wide-field image with only a single-element ultrasonic detector upon a single laser shot. This protocol describes the detailed procedures for PATER system construction, including component selection, equipment setup and system alignment. A step-by-step guide for in vivo imaging of a mouse brain is provided as an example application. Data acquisition, image reconstruction and troubleshooting procedures are also elaborated. It takes ~130 min to carry out this protocol, including ~60 min for both calibration and snapshot wide-field data acquisition using a laser with a 2-kHz pulse repetition rate. PATER offers low-cost snapshot wide-field imaging of fast dynamics, such as visualizing blood pulse wave propagation and tracking melanoma tumor cell circulation in mice in vivo. We envision that PATER will have wide biomedical applications and anticipate that the compact size of the setup will allow it to be further developed as a wearable device to monitor human vital signs.
光声断层扫描（PAT）已经展示了广泛的生物医学应用，从跟踪单细胞到监测小动物的全身动态和诊断人类乳腺癌。目前，PAT 有两种主要的实现方式：光声计算机断层扫描（PACT）和光声显微镜（PAM）。PACT 使用多元素超声阵列进行并行检测，相对复杂且昂贵。相比之下，PAM 需要使用单个元素探测器进行逐点扫描，这限制了成像的速度。系统成本和速度之间的权衡需要一种新的成像方法。为此，我们通过遍历性中继（PATER）开发了光声地形学。PATER 只需单个元素超声探测器，单次激光射击即可捕获宽视场图像。本协议描述了 PATER 系统构建的详细步骤，包括组件选择、设备设置和系统对准。提供了一个示例应用，即体内小鼠大脑成像的分步指南。还详细阐述了数据采集、图像重建和故障排除程序。完成此协议大约需要 130 分钟，其中包括使用 2kHz 脉冲重复率的激光进行校准和快照宽场数据采集各约 60 分钟。PATER 提供低成本的快照宽场快速动态成像，例如可视化血流脉搏波传播和跟踪体内小鼠黑素瘤肿瘤细胞循环。我们预计 PATER 将有广泛的生物医学应用，并期望该设备的紧凑尺寸使其能够进一步开发成为一种可穿戴设备，以监测人体生命体征。
