High Field Cardiac MRI

The advent of 3 Tesla scanners has made a significant impact in neuro-imaging and is now used as a routine clinical tool. Although high-field scanners have the potential to enhance the capabilities of cardiac MRI in several important areas, their use is complicated by degradation due to artifacts. Many of these artifacts are due to susceptibility differences and variations in the magnetic field, which become more problematic at higher field strengths.

Our group has a significant interest in the development of applications for 3 Tesla cardiac MRI, and much of our current focus is therefore directed towards the reduction of susceptibility artifacts at 3 Tesla. We have developed in-house tools to improve cardiac shimming at 3 Tesla, and thus improve image quality. The images below contain spectra obtained after routine shimming per manufacturer specifications (top panel) and additional shimming performed with an iterative technique developed by our group. As shown below, the half-maximum linewidth, over the identical shim volume, was reduced from 91 Hz to 34 Hz with the additional shimming.

Figure 1: Improved shim obtained after two iterations of a dedicated cardiac shim algorithm. The linewidth has been reduced form 91 Hz to 34 Hz.

The potential of 3 Tesla cardiac MRI is being actively explored in our group for a number of indications including non-invasive coronary artery angiography. In addition a large-bore 7 Tesla scanner is present in our center and is highly supported by several scientists both from the Martinos Center and from industry. While it is not anticipated that cardiac imaging will be performed on this scanner in the near future, many of the tools and insights obtained from performing neuro-imaging on humans at 7 Tesla can be applied to cardiac imaging at 3 Tesla. We believe that high-field MRI will make a significant contribution to cardiac MRI both in the clinical and research arenas and believe that our group is well positioned to make important contributions to this effort.