Time course of tumor development on T1-w post Gd-contrast images (a). T2*-w images (80 µm resolution). Hypointense tubular structures, most likely venules (arrowheads), are visible due to the BOLD effect on pre-contrast images (upper row). Post-contrast administration arterioles and venules can be visualized (middle row). A minimum intensity projection (mIP) is shown in the bottom row (b). T2*-w images two and 3 weeks post-tumor implantation (c,d). Quantification of tumor sizes on T1-w post-contrast images (e). Quantification of the vascularized area on T2* images (f). Histogram analysis of the tumor region on post-contrast images 2 (green distribution) and 3 weeks (red) after tumor implantation. A significant signal drop (red distribution) within the tumor relative to the healthy white matter (WM) occurs within 1 week (p<0.001, g). This signal drop is only visible post-contrast administration (red distribution, p<0.001, h). Single plane T2*-w images pre- and post-contrast 2 weeks post-tumor implantation. The tubular vessel is only visible after contrast injection (i). Note the tortuous appearance and the multiple branches of the vessel. Scale bars are 1 mm.