Figure 1.

Oxygen saturation in liver parenchyma and stomach wall during changes of oxygen supply. A) Relative sO₂ (oxygen saturation) in liver parenchyma and stomach wall. Oxygen saturation is calculated as the percentage of oxygenated hemoglobin relative to total hemoglobin based on dual-wavelength PA imaging at 750 nm/850 nm. Gas supply was changed from air to 100% O₂ at 2.8 minutes, from 100% O₂ back to air at 11.5 minutes. B) Representative Oxy-Hemo photoacoustic images co-registered with greyscale B-mode images at 2.8, 7.25, 12.5 minutes. The heat map represents oxygen saturation levels ranging from 100% (red) to 0% (dark blue). Black pixels equal the absence of signal above a defined threshold of 20% of maximum (see methods). Oxygen saturation is calculated as the percentage of oxygenated hemoglobin in relation to total hemoglobin.