Fig. 4.

MRI quantification of tumor-associated phagocytic cells. Magnetic resonance-based macrophage imaging of rodent brain tumors as a function of treatment with CPA and HSV is shown. (A) Tumors of animals receiving mock treatment (−CPA/−HSV, Top), intratumoral HSV (−CPA/+HSV, Middle), or preadministration of CPA and intratumoral HSV (+CPA/+HSV, Bottom) were imaged for tumor-associated phagocytic cells infiltrating the tumor. Imaging was done 72 h after HSV injection (5 days after CPA pretreatment). Magnetic resonance signals were color-coded. Shift toward red indicates a darkening T₂-weighted signal; shift toward blue indicates a paled signal. The darker the T₂-weighted signal, the more superparamagnetic iron oxide particles are incorporated in the tumor by infiltrating peripheral phagocytic cells. (B) Each bar represents the mean T₂ value from 16 images of three rats per treatment group (±SD). Higher T₂ values correspond to decreased intratumoral infiltration of peripheral macrophages. Macrophage imaging showed significant difference among groups.