Immunofluorescence and phosphor imaging of a representative mammary gland section from a 15-week-old MMTV-PyMT mouse. Sectioning was performed 30 min after injection with (R)-[11C]PAQ. (A) Staining with DAPI (blue) and CD31 antibodies (yellow); the most intensely CD31-stained areas are outlined. (B) Staining with DAPI and VEGFR2 antibodies (red); the most intensely VEGFR2-stained areas are outlined. (C) Phosphor imaging displaying radioactivity distributions with an overlay (outlined) of areas with overlapping high VEGFR2 and CD31 expressions. (D1) Magnification of a region with high uptake of radioactivity (indicated with a green square in (A) to (C)) showing the corresponding image with IF where the staining of CD31 and VEGFR2 are merged. (D2) Further magnification indicated by the blue square in (D1) showing VEGFR2 and CD31 co-localization in VEGFR2-positive blood vessels.