Multispectral optoacoustic tomography of peripheral arterial disease based on muscle hemoglobin gradients—a pilot clinical study

BACKGROUND: Current imaging assessment of peripheral artery disease (PAD) relies on anatomical cross-sectional visualizations of the affected arteries. Multispectral optoacoustic tomography (MSOT) is a novel molecular imaging technique that provides direct and label-free visualizations of soft tissue perfusion and oxygenation. METHODS: MSOT was prospectively assessed in a pilot trial in healthy volunteers (group n(1)=4, mean age 31, 50% male and group n(3)=4, mean age 37.3, 75% male) and patients with intermittent claudication (group n(2)=4, mean age 72, 75% male, PAD stage IIb). We conducted cuff-induced ischemia (group n(1)) and resting state measurements (groups n(2) and n(3)) over the calf region. Spatially resolved mapping of oxygenated (HbO(2)), deoxygenated (Hb) and total (THb) hemoglobin, as well as oxygen saturation (SO(2)), were measured via hand-held hybrid MSOT-Ultrasound based purely on hemoglobin contrast. RESULTS: Calf measurements in healthy volunteers revealed distinct dynamics for HbO(2), Hb, THb and SO(2) under cuff-induced ischemia. HbO(2), THb and SO(2) levels were significantly impaired in PAD patients compared to healthy volunteers (P<0.05 for all parameters). Revascularization led to significant improvements in HbO(2) of the affected limb. CONCLUSIONS: Clinical MSOT allows for non-invasive, label-free and real-time imaging of muscle oxygenation in health and disease with implications for diagnostics and therapy assessment in PAD.