Magnetic Resonance Imaging Detection of an Experimental Pulmonary Perfusion Deficit Using a Macromolecular Contrast Agent Polylysine-Gadolinium-DTPA40

RATIONALE AND OBJECTIVES. This study was designed to evaluate the potential of a blood–pool magnetic resonance (MR) contrast agent, polylysine–gadolinium-DTPA4O (polylysine–G-DTPA40) for detecting pulmonary perfusion defects. MATERIALS AND METHODS. Pulmonary emboli were induced in 10 rats by venous injection of 0.2 mL of air. Axial spin-echo images were acquired (TR = 800 mseconds; TE = 6 mseconds) before and after air injection and serially after the administration of polylysine–Gd-DTPA40. The embolism model was confirmed by scintigraphy using 99mTc-macroaggregated albumin. RESULTS. Signal intensity differences between normal and embolized lungs before and after the air injection were less than 25%. After polylysine–Gd-DTPA40 administration, signal intensity of the perfused lung increased more than 200%, whereas the embolized lung increased by only 25%. Signal intensities of the perfused lung remained stable for 1 hour, whereas signal intensities of the embolized lung gradually increased for 20 minutes as the air embolus dissolved. CONCLUSION. Magnetic resonance imaging (MRI) enhanced with a macromolecular blood–pool contrast agent can be used to detect acute pulmonary embolism in a confirmed animal model.