Ultrasound-Guided Breath-Compensation in Single-Element Photoacoustic Imaging for Three-Dimensional Whole-Body Images of Mice

Abstract

Photoacoustic imaging can be used to extract functional information at the molecular level for imaging the whole body of small animals in vivo. However, the use of a mechanical scanner to image the whole body involves acquiring the data for a period of time which can lead to breathing-related artifacts. Thus, the acquired three-dimensional data cannot be analyzed and visualized using two-dimensional projection rendering techniques unless the respiratory distortions are minimized. In this study, an ultrasound-guided breath-compensation method for the three-dimensional data of photoacoustic macroscopy to facilitate visualization and analysis in the depth direction is presented. Photoacoustic and ultrasound data of the whole body of mice were acquired in vivo, then the distorted skin layers were compensated in ultrasound data. The extracted distortion parameters were then applied to the corresponding photoacoustic data to compensate for the motion. The compensation method was successfully applied to visualize three-dimensional hemoglobin oxygen saturation in the whole body of mice in vivo by using multispectral photoacoustic data. The resulting three-dimensional images show that the developed methodology can be used in various biomedical studies, including monitoring drug delivery, imaging of tumors, and analysis of vasculature networks.

Contrast Agents for Photoacoustic Imaging: A Review Focusing on the Wavelength Range

“…Moreover, exogenous agents have been modified to have various functionalities, including disease targeting and drug delivery capabilities, environment-related signal switching, and treatment ability. In vivo visualization of small animals using these contrast agents has been widely studied using various PAI systems [ 115 , 116 , 117 ]. According to the configuration of the PAI system, the penetration depth and spatial resolution of the resulting images are varied [ 118 ].…”

Recent Advances in Photoacoustic Agents for Theranostic Applications

“…TPM, two−photon fluorescence microscopy; OR−PAM, optical−resolution photoacoustic microscopy; AR−PAM, acoustic-resolution photoacoustic microscopy; PACT, photoacoustic computed tomography; USI, ultrasound imaging; The images are reproduced with permission from Refs. [ 24 , 25 , 26 , 27 ].…”

“…Compared to pure optical imaging techniques, PAI can significantly increase the imaging depth while maintaining a relatively good spatial resolution [ 23 ]. In particular, the resolution and imaging depth of PAI can be tuned between US and fluorescence imaging by adjusting the foci of the ultrasound and light sources ( Figure 1 ) [ 24 , 25 , 26 , 27 ]. By inheriting the advantages of optical imaging techniques, PAI can also be used to monitor drug delivery, treatment responses, and agent assessment [ 28 , 29 , 30 , 31 , 32 ].…”

Whole-Body Photoacoustic Imaging Techniques for Preclinical Small Animal Studies

“…Although volumetric data were obtained in this system, three-dimensional (3D) visualization was limited owing to breath-related distortion during the long scanning time. Recently, Lee et al improved the system to achieve both US and PA images simultaneously and produced breath-compensated 3D PA whole-body images of mice [ 27 , 28 ]. Breath-related distortion was corrected by segmenting the skin profile in US images, realigning the signals in the axial direction, and applying the realignment parameters to the corresponding PA data.…”