Just-in-time burn severity assessment plays a vital role in burn treatment and care. However, it is still difficult to quantitatively and promptly evaluate burn severity by existing medical imaging methods via initial burn depth measurement since burn wounds are usually dynamically developed. As an elastic skeleton of skin, the degree of conformational changes of collagen fibers caused by overheating can reflect the burn severity in a timelier manner. Herein, the polarized photoacoustic technique (PPAT) for just-in-time quantitative evaluation of burn severity via collagen fiber anisotropy assessment is proposed. First, phantom experiments demonstrate the ability of PPAT for deep imaging in a transport mean free path and accurately quantify changes in microstructural order by thermal damage. Then, the Pearson correlation coefficient of the PPAT in assessing burn severity is shown to be up to 0.95, validated by burn skin samples. The PPAT provides a just-in-time quantitative strategy for burn severity evaluation.

Photoacoustic imaging has been developed to image the immune study at the macro scale. Macrophages play diverse roles in the acute response to infection and tissue repair. However, macrophages activities in acute inflammation at the microscopic level still remain challenging. In this work, we proposed optical-resolution photoacoustic microscopy to promptly monitor the labeled macrophages activities in normal and inflammatory groups. The result showed that many labeled macrophages emerged around the vessels firstly, then exuded into tissues, and finally disappeared in the inflammatory group injected with labeled macrophages. In summary, our method allows us to exactly image and track the immune cells of inflammatory diseases.