Figure 2. MRI contrast of small intrasplenic tumours following administration of Fe NP or IONP.

(A) Six week old Balb/c mice received intrasplenic injections of PBS only, or (B), 1×10⁶ 4T1 breast cancer cells and were imaged by MR 72 h later. An intravenous dose of PBS (Control, left column), IONP (middle column) or Fe NP (right column) was administered 8 h before imaging. (C) The signal intensity (SI) in the tumours was compared within the same mouse to that of the spleen and plotted as %ΔSI signal as follows: (SI of tumour - SI of spleen)/(SI of tumour). (D) An enlarged image (scale bar = 2 mm) shows the clear distinction between splenic parenchyma and tumour (arrow) in a representative mouse that received Fe NP. (**P<0.01 by Mann-Whitney rank-sum test).