Dual Echo Dynamic MRI using Dy- micelles and Gd-DTPA as a contrast agent

Introduction: Dynamic contrast enhanced MRI can examine tissue vascularization but cannot distinguish between perfusion and permeability effects. By injecting Gd-DTPA (extravascular contrast agent) concurrently with Dy-micelles (intravascular within the imaging time frame) and imaging them at different echo times, it might be possible to estimate both perfusion and permeability parameters simultaneously. The contrast agent with higher R1/R2 ratio (Gd) would primarily influence signal intensity in short echoes, while the contrast agent with very low R1/R2 ratio (Dy) would have limited effect on the signal intensity in the short echo while still affecting longer echoes, thereby potentially allowing dissection of different vascular properties of tissues. To evaluate feasibility of this approach, we tested relaxation properties of a mixture of different concentrations of Gd-DTPA and Dy-micelles in water and blood.