Fig. 3: Validation based on histology and immunochemistry.
a–c Maximum intensity projections of the distribution of total haemoglobin concentration (HbT), Hb and HbO2 in the xy plane of the 4T1 tumour close to the central plane. d–f Cryosections were taken at depths from within the region of the tumour used to generate these maximum intensity projections, and the sections were stained with haematoxylin-eosin, an antibody against endothelial marker CD31 or an antibody against hypoxia-associated HIF-1α. In some cases, the nuclear stain DAPI (blue) was also included. White dashed lines highlight regions with good correlation between optoacoustic images and histology micrographs. g, h Profiles were drawn along the straight white lines in (a) and (d) as well as (b) and (e). Green and blue arrows show the regions with opposite features in the HbO2 and HIF-1α images. i, j Higher magnification views of the cryosection regions boxed in green or blue are shown after staining with haematoxylin-eosin. k–m The histograms of optoacoustic and histological images in (a–f) are listed. Some images have been rotated to highlight correlations with other images. All maximum intensity projections in this figure were calculated over sections with a thickness of 400 μm. Scale bars, 1 mm
