Diseases associated with musculoskeletal inflammation cause debilitating pain to millions of people worldwide. Early and targeted diagnosis has been of great interest for a better understanding of musculoskeletal inflammation diseases. Optoacoustic imaging with targeted NIR probes enables functional molecular imaging and overcomes some of the limitations of conventional imaging techniques used for diagnosis of musculoskeletal inflammation diseases.

Three-dimensional rendering of a mouse paw. Contrast agent shown in Union Jack color scale. Single-wavelength MSOT contrast shown in grayscale.

Detection of inflammation with a targeted contrast agent

A macrophage-targeting polymer-based probe was used to detect inflammation in the foot of a mouse with Lipopolysaccharide (LPS)-induced inflammation. Similar approaches have been used in other mouse models of arthritis. MSOT can visualize the distribution of the probe with high sensitivity and specificity in 3D, while providing an anatomical background image based on endogenous tissue contrast from hemoglobin.

Inflammatory MSOT signal in mice stratified by MRI

A selectin-targeting agent was used to increase MSOT contrast in the arthritic knees of mice treated with Freund’s complete adjuvant. Healthy joints can be differentiated from arthritic ones, allowing investigators to potentially forego the time, expense, and infrastructure required for MRI scans. 

MSOT signals for groups of mice separated according to MRI-mediated synovitis detection.