Tomographic imaging with an LED-based photoacoustic-ultrasound system

Combined Photoacoustic (PA) and Ultrasound (US) imaging systems are finding more preclinical and clinical applications. However, majority of the commercial systems use expensive pulsed lasers. In most small animal studies and clinical applications like arthritis screening of finger joints, there is a need for tomographic imaging. In this work, we present PA and US tomographic imaging using a commercial imaging system with LED arrays as illumination source. We employ multiangle spatial compounding of PA and US images using a probe with a linear array transducer and four LED arrays, to form dual-mode tomographic images. Using phantom experiments, the proposed approach is validated and thoroughly tested. Further, the potential of the system is demonstrated by imaging knee joint and abdominal region of a mouse. This proposed approach has several advantages. First, the resolution and signal to noise ratio (SNR) are improved with the compounding of images from multiple angles. The resolution improvement owes to better axial resolution compared to lateral and high SNR with averaging. Secondly, the limited view artifacts and loss of information from the use of a linear array US probe is tackled. The US tomographic images of the mouse-knee RA model show structural details of the joint and blood vessels were visible in the tomographic PA images. The whole animal images enabled improved functional and structural information. An affordable PA/US tomographic imaging system with potential in clinical arthritis-screening and small animal imaging is presented.