ULTRASMALL SUPERPARAMAGNETIC IRON-OXIDE TO ENHANCE MRA OF THE RENAL AND CORONARY-ARTERIES - STUDIES IN HUMAN PATIENTS

Objective: Our goal was to determine the feasibility of using an intra vascular MR contrast agent to improve 3D MRA. Materials and Methods: T hree-dimensional TOF MRA was performed in nine patients both prior to and following the administration of an ultrasmall particle superparama gnetic iron oxide contrast agent (AMI 227). The lengths of both renal arteries were measured from the maximum intensity projection (MIP) ima ges as well as the individual partitions. Seven of these patients also were studied by a 3D coronary artery MRA sequence. Signal-to-noise ra tio (SNR) and contrast-to-noise ratio (CNR) measurements of the right coronary artery were determined both prior to and following the admini stration of AMI 227. Statistical analysis of both renal artery lengths and right coronary SNR and CNR was performed using a one tailed paire d t test comparing pre- and postcontrast images. Results: The renal ar tery lengths significantly increased (right renal artery: 30%, p = 0.0 01; left renal artery: 25%, p < 0.008) when measured from the individu al axial slice partitions. No significant increase in length was obser ved on the MIP images following contrast. In the right coronary artery , the SNR increased by an average of 80% (p = 0.008) and CNR increased by an average of 109% (p = 0.007). Increased background signal and su perimposed venous structures reduced the measurable lengths of the ren al arteries from the MIP images. Conclusion: These studies support the hypothesis that 3D MRA in the body will benefit from the use of intra vascular contrast agents. Nevertheless, conventional MIP processing is unable to reveal the full advantage of the contrast improvement.