Elimination of Non-targeted Photoacoustic Signals for Combined Photoacoustic and Ultrasound Imaging

Abstract

As a molecular imaging modality, photoacoustic imaging has been in the spotlight because it can provide an optical contrast image of physiological information and a relatively deep imaging depth. However, its sensitivity is limited despite the use of exogenous contrast agents due to the background photoacoustic signals generated from non-targeted absorbers such as blood and boundaries between different biological tissues. Additionally, clutter artifacts generated in both in-plane and out-of-plane imaging region degrade the sensitivity of photoacoustic imaging. We propose a method to eliminate the non-targeted photoacoustic signals. For this study, we used a dual-modal ultrasound-photoacoustic contrast agent that is capable of generating both backscattered ultrasound and photoacoustic signal in response to transmitted ultrasound and irradiated light, respectively. The ultrasound images of the contrast agents are used to construct a masking image that contains the location information about the target site and is applied to the photoacoustic image acquired after contrast agent injection. In-vitro and in-vivo experimental results demonstrated that the masking image constructed using the ultrasound images makes it possible to completely remove non-targeted photoacoustic signals. The proposed method can be used to enhance clear visualization of the target area in photoacoustic images. IEEE