A portable three-dimensional photoacoustic tomography system for imaging of chronic foot ulcers

Background: Chronic leg ulcers affect approximately 6.5 million Americans and the disorder is associated with a range of serious complications. Since many chronic ulcers have underlying vascular insufficiency, accurate assessment of tissue perfusion is critical to treatment planning and post-surgical monitoring. However, existing clinical tests fail to meet this need in practice due to their low sensitivity or accuracy. Methods: In this paper, we introduce a portable photoacoustic tomography (PAT) system for wound assessment. Since hemoglobin serves as the major endogenous contrast at near-infrared wavelengths, PAT provides label-free, three-dimensional (3D) imaging of hemoglobin distribution, which is closely related to blood perfusion. The proposed system consists of a 128-element linear transducer array, a data acquisition (DAQ) system, and a pulsed Nd:YAG laser source, all mounted on a portable cart for easy clinical testing. Results: We validated our system through both phantom and human imaging studies. The phantom imaging results indicate that the system's spatial resolution ranges from 0.5 mm along the axial direction to 1.3 mm along the elevational direction. The healthy volunteer result shows clear foot vasculature, indicating good perfusion. The preliminary patient imaging results agree very well with the clinical test, demonstrating that PAT has a high potential for assessing the circulation around the wound. Conclusions: We believe that our technique will be a valuable tool for assessing tissue perfusion and guiding wound treatment in vascular clinics.