MRI Near Metal
The presence of metal can be a serious problem in MRI, because (1) Magnetic metals can experience a force in the scanner, (2) Long wires (such as in pacemakers) can result in induced currents and heating from the RF magnetic field and (3) Metals cause the static (B0) magnetic field to be inhomogeneous, causing severe image degradation.
The first two of these problems are a DANGER to the patient, and are cause to not do an MRI. The third is not dangerous, but can result in severely distorted images using conventional MRI.
Metallic implants are increasingly common in medicine, including dental fillings, stents, joint replacements, spinal fixation, and many more. However, complications can arise when implants are used, and there are not always good methods for imaging to assess these complications.
We are addressing the inhomogeneity problem by developing distortion-free MR imaging near MR-safe implants. Using additional encoding, it is possible to dramatically improve the images, as shown in this example of a person with metal screws in his knee. Although these methods are now being made commercially available, we continue to improve the speed, flexibility and resolution of MRI near metal.
Faster MRI Near Metal Using Subsampling
Faster MRI near metal is enabled by subsampling and tightening the field of view to fit the shape of distorted slices.
MR Thermometry Near Metal
This novel development enables non-invasive temperature measurement using MRI (MR thermometry), in the vicinity of implanted metallic devices such as joint replacements or fixation hardware.
2D Multi-Spectral Imaging For Fast MRI Near Metal
This approach offers a fast (tens of seconds per slice) approach to MRI near metal while correcting much of the signal loss, distortion and abnormally bright signal that can occur near implanted metal.
Metallic Implant Estimation Using Susceptibility Mapping
Magnetic field patterns can be used to identify the location and shape of metal devices and render them on images.
Improved Field Mapping Near Metal
Reducing the noise and distortion in magnetic field maps near metal implants allows for better visualization of the anatomy near the implant.
Accelerated 3D Multispectral MRI with Robust Principal Component Analysis
We have developed a method to acquire diagnostic MR images in 2-3 minutes to help millions of people who have complications related to metal devices, commonly hip replacements, knee replacements or spinal fixations.
Artifact-Reduced Imaging of Biopsy Needles with 2D Multispectral Imaging
We have validated the use of an MR imaging method that reduces the image artifacts due to metal objects for tracking biopsy needles in MR-guided procedures.
MRI Monitoring of Focused Ultrasound Sonications Near Metallic Hardware
We previously developed a method for imaging temperature changes in tissue near metal hardware; here we evaluate its use to monitor MR-guided focused ultrasound treatments.