Atovaquone (ATQ) induces modification of tumor hypoxia in Calu6 xenografts. A, TMR [18F] FAZA uptake is increased from baseline at day 7 in control tumors (Cn; white bars) but was reduced in drug-treated tumors. B, Example [18F] FAZA PET images, with greatest hypoxia represented by orange and red. C, Tumor MRI hypoxic fraction showed similar relative reduction at day 3 and 7, relative to control tumors. D, Example segmented MRI images showing hypoxic (blue), normoxic (yellow), and necrotic (gray) tumor. E, Lower percentage of pimonidazole staining was detected in drug-treated tumors at day 7, compared to controls. F, Example pimonidazole adduct formation images (×40 magnification).