Double contrast technique for MRI-guided vascular interventions

#This invention relates to the field of magnetic resonance imaging, more specifically to the use of two opposing contrast mechanisms or agents for magnetic resonance imaging (MRI) guided vascular intervention procedures.

#Oftentimes, during therapeutic procedures it is desirable to deliver a particular medical device or a therapeutic agent to a discrete location in the vasculature of a patient. Typically, such delivery is accomplished using a catheter which is introduced into a blood vessel of the patient and then advanced to the targeted location. Examples of such interventions include but are not limited to, angioplasty, stenting, determination of an embolization, local drug injections, including local chemotherapy, and gene therapy. Unfortunately, such procedures can be very difficult and time-consuming since the vasculature is highly branched. In addition, the extensive branching of the vasculature can lead to misdirection of the catheter.

#In recent years, attempts have been made to use MRI to monitor the advancement of the catheter in the vasculature. The potential benefits of using magnetic resonance guidance for endovascular procedures have recently been advanced by a number of research groups .(Bakker C J, Hoogeveen R M, Hurtak W F, Van Vaals J J, Viergever M A, Mali W P. Radiology 1997; 202: 273-276; Omary R A, Frayne R, Unal O, Grist T M, Strother C M. J Vasc Interv Radiol 1999; 10: 1315-1321; Omary R A, Frayne R, Unal O et al. J Vasc Interv Radiol 2000; 11: 373-381; Spuentrup E, Ruebben A, Schaeffier T, Manning W J, Gunther R W, Buecker A. Circulation 2002; 105: 874-879; Wacker F K, Reither K, Branding G, Wendt M, Wolf K J. Mag. J Magn Reson Imaging 1999; 10: 841-844; Wildermuth S, Debatin J F, Leung D A et al. Radiology 1997; 202: 578-583; Strother C M, Unal O, Frayne R et al. Radiology 2000; 215: 516-519; Omary R A, Unal O, Koscielski D S et al. J Vase Interv Radiol 2000; 11: 1079-1085.) These include the lack of ionizing radiation, the avoidance of iodinated contrast material, and the ability to measure changes in end-organ function with MR. Accurate visualization of the target vessels is essential during MR-guided procedures. However, the inflow effect of blood does not always provide sufficient contrast for clear vessel delineation, and is dependent upon the orientation of the imaging slice relative to the vessel and direction of blood flow. Thus, MRI procedures using magnetic or paramagnetic substances that enhance contrast have been developed. The use of TI-shortening gadolinium preparations, such as Magnevist™ (Gd-DTPA, Schering A G, Berlin, Germany), provides a more flow-independent vessel visualization. However, Gd-DTPA has a very short intravascular retention time. Therefore, multiple injections are required to repeatedly obtain angiograms during an interventional procedure. This can cause marked enhancement of the background tissue, which reduces the vessel contrast and thus the overall image quality.

#FIG. 1 illustrates an example MRI system.

#FIG. 2 is a graph showing the signal to noise ration (SNR) of a region of interest (ROI) positioned in the aortic lumen of a pig before, during and after a single CO2 injection through a catheter located in the abdominal aorta.

#FIG. 3 is a bar graph showing mean SNR values before (1), during (2) and after (3) CO2 injections (n=20) in the porcine aorta. During CO2 passage, SNR is significantly reduced (p<0.0005) compared to the SNR before injection.

#Example systems, methods, and computer media, are now described with reference to the drawings, where like reference numerals are used to refer to like elements throughout. In the following description for purposes of explanation, numerous specific details are set forth in order to facilitate thoroughly understanding the methods, systems, and computer readable media. It may be evident, however, that the methods, systems, and computer readable media can be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to simplify description.

#Lexicon

#A. Magnetic Resonance Imaging Terms