Representative axial images of the investigated human colon carcinoma xenografts including tumor morphology (T2w images, top row), tumor perfusion parameter maps (middle row) and 18F-FDG-PET (bottom row) before therapy (left column) and after a one-week treatment course of regorafenib (right column). Note the significant decrease of tumor plasma flow (mL/100mL/min) and tumor glucose metabolism (TTB) after regorafenib therapy between baseline and follow-up.

The hyperintense central tumor regions on the T2-weighted image after therapy are consistent with increasing, therapy-induced tumor necrosis.