GEH121333 Tumor T1-enhancement corresponds to free iron oxides in central necrosis.

<p>(A) Axial T1- and T2*-weighted MR images of a representative PymT tumor before and 48 hours post injection (p.i.) of ferumoxytol at a dose of 0.5 mmol Fe/kg. Note homogenous tumors on pre-contrast images. The tumor center demonstrates hyperintense (bright) T1-enhancement and hypointense (dark) T2*-enhancement while the tumor periphery demonstrates hypointense enhancement on both sequences. (B) Corresponding histopathology (20x magnification) demonstrates areas of apparently free PEG-Cy5 (red) positive iron oxides in central tumor areas. F4/80 positive (green) macrophages outline these central areas. (C) Higher magnification (40x magnification) of the central tumor area confirms free PEG-Cy5 positive iron oxides (red) in central, necrotic tumor areas with low cell quantity (DAPI, blue). (D) Closer evaluation of peripheral tumor areas with high cell content demonstrate PEG-Cy5 (red) positive iron oxides co-localized to abundant F4/80 positive (green) macrophages.