The fate of the IntraVascular MRI (IVMRI) Catheter, a self-contained magnetic resonance system for visualization of coronary arteries from Israel’s TopSpin Medical, is now in the hands of the FDA. We’ve been following this exciting technology since 2005. According to Globes, the company completed laboratory tests, preclinical and clinical trials for the catheter, and its CEO is quite optimistic about a possible US approval. The system has received the CE Mark from the European regulators back in December.
To remind our readers, here’s how the technology works:
TopSpin Medical has developed a self contained “inside-out” miniature MRI probe in a tip of an intravascular catheter that allows for local high-resolution imaging of blood vessels without the need for external magnets or coils. The advantages of this technique range from the very practical aspect of a low-cost system (since no expensive external setup is required), accessibility to the patient during the procedure, compatibility with existing interventional tools, and finally resolution and diffusion contrast capabilities that are unattainable by conventional clinical MRI, due to the strong local gradients created by the probe and its proximity to the examined tissue.
The intravascular probe serves as a first example for a wide range of applications for this method, which in the near future may revolutionize the field of clinical MRI. It opens the door for the application of MRI in cases where high-resolution local images are required and when the transformation into an MRI environment is both mentally and economically difficult for the hospital. The medical applications for this technology include detection and staging of prostate cancer, imaging tumors in the colon, lung and breast and intravascular imaging of the peripheral vasculature…
A static magnetic field of about 0.2 Tesla is generated by strong permanent magnets located at the tip of the catheter. The gradients that result from such a small configuration are in the range of 100-300 T/m, and may be controlled to some extent by changing the angle of the magnetization and the dimensions of the gap between the two magnet pieces. Due to volume constraints, a single coil is used both for transmission and for reception. The magnetic field profile created by this “inside-out” probe within the imaged volume is significantly different from that created by conventional NMR or MRI setups.
The IVMRI catheter is used for measuring the apparent water diffusion coefficient of the various components of the atherosclerotic vascular wall. It shows decreased and isotropic water diffusion within the atherosclerotic plaque compared with the fibrous cap and medial layer. Hence, the heterogeneous water diffusion properties within the atherosclerotic arterial wall can be exploited, by the IVMRI catheter, to develop an index of arterial wall lipid infiltration and help determine the structure of the arterial wall with regard to lipid content. The extent and location of increased vascular lipid infiltration can then be used to determine the presence of an atherosclerotic lesion with an increased likelihood of subsequent clinical instability. The IVMRI catheter was designed to obtain high-resolution imaging, thereby revealing the depth and size of the necrotic core and assess fibrous cap thickness.