Serial MRI in mice that received magnetically labeled Sca1⁺ bone marrow cells, group 2. (A) 3D RARE images showing evolution of hypointense regions within and around tumor, due to incorporation of labeled cells into vascular structures or within parenchyma of tumor. Arrowheads indicate needle tract on day 4 after tumor implantation and growing tumor area on days 9 and 11. Hypointense areas in and around the tumor are evident at day 9, and a hypointense rim surrounding the tumor is observed on day 11. (B) Ex vivo gradient echo MRI of the same mouse at day 11.