TRADITIONAL POSTER - ismrm

Poster Sessions
3081. Imaging Near Metals with Phase Cycled SSFP
Michael Nicholas Hoff 1 , Jordin D. Green 2 , Qing-San Xiang 1,3
1 Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia, Canada; 2 Siemens Healthcare,
Calgary, Alberta, Canada; 3 Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada
A fast bSSFP technique is devised for removing imaging artifacts near metals. 3D phase cycled TrueFISP provides comprehensive artifact reduction using
powerful gradients, two dimensions of phase encoding, short TR, and thorough refocusing of magnetization. Problematic banding artifacts are eliminated
using a technique which formulates expressions for each voxel’s modulated magnetization, and then analytically solves the system with a simple Cross-
Solution (XS) to obtain the demodulated magnetization. Application to a phantom consisting of a hip prosthesis within a Lego structure confirms that 3D
imaging with XS-SSFP is simple, efficient, and robust in artifact reduction.
3082. B 1 Effects When Imaging Near Metal Implants at 3T
Kevin M. Koch 1 , Kevin F. King 1 , Graeme C. McKinnon 1
1 Applied Science Laboratory, GE Healthcare, Waukesha, WI, United States
Recently developed techniques have enabled low susceptibility-artifact imaging near metal implants using conventional spin-echo acquisition strategies.
Previous demonstrations of these techniques have been presented at 1.5T. While the susceptibility artifact mitigation of these techniques remains sufficient
at 3T, here we address the effects of reduced B 1 wavelength applied at 3T. These effects introduce increased B 1 artifacts near metal implants, particularly
those with long axes oriented collinear with B 0 . Finite element simulations and phantom images are presented to demonstrate and discuss these effects.
3083. Adaptive Slice Encoding for Metal Artifact Correction
Brian A. Hargreaves 1 , Garry E. Gold 1 , John M. Pauly 2 , Kim Butts Pauly 1
1 Radiology, Stanford University, Stanford, CA, United States; 2 Electrical Engineering, Stanford University, Stanford, CA, United
States
Slice encoding for metal artifact correction (SEMAC) excites 2D slices, then uses a 3D encoding to resolve the distortion of slices due to large metalinduced
susceptibility shifts. The addition of a simple, fast spectral prescan easily estimates the extent of this distortion, allowing the slab width and
encoded field-of-view to be adapted to the subject. This, allows the total number of excited slices to be greatly reduced without diminishing final image
quality, thus offering a substantial reduction in SEMAC scan time.
3084. Fat-Suppressed and Distortion-Corrected MRI Near Metallic Implants
Brian A. Hargreaves 1 , Wenmiao Lu 2 , Kim Butts Pauly 1 , John M. Pauly 3 , Garry E. Gold 1
1 Radiology, Stanford University, Stanford, CA, United States; 2 Electrical & Electronic Engineering, Nanyang Tech University,
Singapore, Singapore; 3 Electrical Engineering, Stanford University, Stanford, CA, United States
Fluid-sensitive volumetric imaging of patients with metallic implants is potentially an important diagnostic tool to assess for infection, implant loosening, or
other complications. Recent MR techniques use spin echoes combined with additional encoding to substantially reduce distortion and signal loss artifacts.
Here we demonstrate the use of these sequences with short TI inversion recovery (STIR) to provide reliable fat suppression near metallic implants, which is
particularly important in assessment of many disorders.
3085. Spiral Chemical Shift Imaging in the Presence of Metal Artifacts
Atsushi M. Takahashi 1
1 Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States
MRI in the presense of metal in the body is complicated by B0 field perturbations and by the shortening of the T2* relaxation times. With a multiinterleave,
short readout, spiral k-space trajectory, chemical shift imaging method, we can image in the presence of metal. Here we describe a method which
can be used in-vitro to visualize the field maps surrounding metal implants.
3086. Evaluation of MR Image Artifacts of Stent Implants at 3 Tesla Using a Phantom Filled with Mineral
Oil Compared to CuSO4
A Koenig 1,2 , Frank Reintke 2 , Gerrit Schönwald, 2,3 , Gregor Schaefers 2
1 University of applied Science Gelsenkirchen, Gelsenkirchen, NRW, Germany; 2 MR Safety Testing Laboratory, MR:comp GmbH,
Gelsenkirchen, Germany; 3 University Witten/Herdecke
The ASTM-Standard F2119-07 is used to evaluate artifacts of implants. According to the test method a phantom with CuSO4 is used. By replacing the
solution by mineral oil it is desired to avoid standing waves in images. We tested both fluids in two sequences (SE/GRE) with 2 test devices, a Nitinol stent
and an acryl reference tube. We compared a visual, a statistically and a manual analysis. We noticed non-significant results with one exception. Under
certain conditions the standard CuSO4 can be exchanged with mineral oil allowing better and precise artifact analysis at higher field strengths ¡Ý 3 T.
3087. Comparison of Fat Suppression Methods for Functional and Diffusion Studies Using SE EPI at 7T
Dimo Ivanov 1 , Markus Streicher 1 , Andreas Schäfer 1 , Robert Turner 1
1 Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
The increased SNR of ultra-high-field MR scanners allows high resolution functional and diffusion studies to be performed. Because chemical-shift artifact
suppression is essential for SE EPI images, we evaluated the performance of different fat suppression techniques. Conventional methods using additional
radiofrequency (RF) and gradient pulses provide suboptimal results owing to increased B0 and B1 inhomogeneity at higher fields. They also increase RF
power deposition. A recently developed method using different slice-select gradient strengths during the excitation and refocussing pulses was demonstrated
to be most robust, and delivered best chemical shift selection.