Relative change in the A parameter (mean ± SEM) from day 0 to day 8 for the experimental groups. 3.5 mg/kg PL-DXR was administered after pre-treatment DCE MRI. RT was delivered at a dose of 2 Gy/day for 5 consecutive days, starting 24 hours after the pre-treatment DCE MRI. Hypoxia was induced by clamping the tumor-bearing leg 5 minutes prior to and during RT. Significant differences (p < 0.050) to the control or PL-DXR + hypoxic RT groups are indicated with # or ×, respectively.