3D MR angiography of intratumoral vasculature using a novel macromolecular MR contrast agent

Noninvasive methods to visualize blood flow in the intratumoral vasculature have not previously been studied. In the present study, the use of a novel intravascular MR contrast agent with a generation-6 polyamidoamine dendrimer core (G6-(1B4M-Gd)₁₉₂; MW: 175kD) was investigated, and the vasculature in experimental tumors was visualized using 3D MR angiography (MRA). Xenografted tumors in nude mice of two different histologies - KT005 (human osteogenic sarcoma) and LS180 (human colon carcinoma) - were used to obtain 3D MRA using G6-(1B4M-Gd)₁₉₂ and Gd-DTPA. The contrast MR sectional images were correlated with the corresponding histological sections. The intratumoral vasculature in the KT005 tumor was clearly visualized by 3D MRA, which became more evident with the growth of the tumor xenograft. In contrast, the intratumoral vasculature in the LS180 tumor was sparser and much less developed than that in KT005 tumors. Blood vessels with a diameter as small as 100 μm based on histology were visualized using 0.033 mmol Gd/kg of G6-(1B4M-Gd)₁₉₂. In conclusion, intratumoral vasculature with a 100-μm diameter was visualized better using 3D MRA with G6-(1B4M-Gd)₁₉₂ than with Gd-DTPA.