Fig. 1.

Optoacoustic tomography reveals oestrogen-independent MDA-MB-231 tumours have poorer oxygenation than oestrogen-dependent MCF-7 tumours and healthy tissue. a Regions of interest (yellow outline) were drawn in the optoacoustic tomography slice at which the tumour area burden was highest. A region containing the aorta and inferior vena cava was used as a baseline reference in normal tissue. Representative images show the spatial distribution of b oxygenation (SO₂^MSOT) and (c) total haemoglobin (THb) with tumour regions of interest overlaid (yellow outline). Quantification graphs are shown on the right, data were extracted from all regions of interest, and show a significantly higher oxygenation in MCF-7 compared to MDA-MB-231 (b) tumours and a decrease in THb (c). n^MCF−7 = 11; n²³¹ = 16, data expressed as mean ± SEM. *p < 0.05, ****p < 0.0001. Statistical significance was assessed by paired two-tailed t-test within a single-tumour type and by unpaired two-tailed t-test between tumour types