The use of both magnetic resonance imaging (MRI) and pacing devices has vastly increased worldwide in recent years. A significant number of implanted patients will likely need monitoring using magnetic resonance imaging (MRI) over the course of the lifetime of their device. Some studies have demonstrated that with appropriate precautions, MRI can be safely performed in patients with selected implantable pacemakers. However, MRI is still contraindicated in patients with pacemakers. Recently, new pacing systems have been specifically designed for safe use in the MRI environment. The first reported experience suggests that the technology is safe and may allow patients with these new pacemakers to undergo MRI. This review will describe the outstanding issues and controversies surrounding the safety of MRI in patients with pacemakers, and the potential benefits of the new MRI-conditional technology. We will also discuss how to decide whether an MRI-conditional system should be implanted, and highlight key issues that warrant further studies.
Humans ; Magnetic Resonance Imaging*

No abstract available.
Magnetic Resonance Imaging*

No abstract available.
Dermatomyositis* ; Magnetic Resonance Imaging*

OBJECTIVE: Achieving successful posterolateral fusion across the lumbosacral junction is particularly problematic. In our hospital, bilateral S2 laminar hooks coupled with bilateral S1 screws have been appeared to provide successful posterolateral fusion of lumbosacral junction in high non-fusion risk patients. Therefore we study about the safety of sacral lamina hooks insertion. METHODS: We measured the anterior-posterior(A-P) diameter of sacral canal at a point where median sacral crest of S1 and S2 meet on lumbar magnetic resonance(MR) sagittal images. The number of analyzed subjects was one hundred and minimum A-P diameter of sacral canal to insert laminar hooks safely was thought to be 9mm. RESULTS: In 78% of study cases, the sacral canal diameter was 9mm or more. There were no statistically significant difference of sacral canal diameter with age, sex, weight and height. CONCLUSION: Preoperative analysis of the sagittal MR image may be helpful for the safe insertion of the sacral laminar hooks to enhance posterolateral fusion of lumbosacral junction in high non-fusion risk patients. And, safe sacral laminar hooks insertion may be possible in about 78% of study cases.
Humans ; Magnetic Resonance Imaging*

No abstract available.
Magnetic Resonance Imaging*

In order to observe the pattern of a flow image on multisection MR imaging technique, a flow phantom experiment was preformed using a superconducting high filed 2.0 Tesla MRI scanner. The pattren of the first section images was homogeneous round at all flow velocities until the turbulence forming level. The patterns of the second section images,however,changed into a homogeneous round shape, a ring shape, a target shape, and a small round shape as the velocity increased. When scanned at velocities higher than the trubulence forming level, the images become distored and irregular, and eventually disappeared after the cut-off velocity. The homogeneous round image senn at the lower velocity levels in throught to be due to the overwhelming effects of fully managetized spins influxed into the imaging section during the prior repetition time(TR). Later in the higer velocity levels the effects of the partially saturated spins and fully magnetized spins influxed during the section transit time(TR/slice number) are added, and result in ring, target, and small round patterns in the second section image.
Magnetic Resonance Imaging*

PURPOSE: B1 field of birdcage RF (radiofrequency) coil that is used most for brain imaging in magnetic resonance imaging (MRI) decreases toward endring from the coil center. We investigated how much RF B1 homogeneity effect the endcap shield brings form the coil center as it towards to endcap region. MATERIALS AND METHODS: We compared RF B1 field distribution by each finite difference time domain (FDTD) simulations for lowpass, highpass and hybrid birdcage RF coils. We selected the highpass birdcage RF coil that was the highest RF B1 field condition as simulation result, and studied how much RF B1 homogeneity effect was occurred when endcap shield was applied to endring area. RESULTS: B1 field of the highpass birdcage RF coil was higher than other birdcage RF coil types as simulation result. However, the RF B1 homogeneity was lower than other coil types. RF B1 field of highpass birdcage RF coil with endcap shield is similar with RF B1 field of hybrid birdcage RF coil and the overall RF B1 homogeneity in sagittal direction was better. CONCLUSION: In this paper, proposed method can apply improving RF B1 homogeneity of RF coil in clinical examination.
Magnetic Resonance Imaging* ; Neuroimaging

No abstract available.
Magnetic Resonance Imaging* ; Relaxation*

No abstract available.
Breast* ; Magnetic Resonance Imaging*

PURPOSE: A new compressed sensing technique by iterative truncation of small transformed coefficients (ITSC) is proposed for fast cardiac CINE MRI. MATERIALS AND METHODS: The proposed reconstruction is composed of two processes: truncation of the small transformed coefficients in the r-f domain, and restoration of the measured data in the k-t domain. The two processes are sequentially applied iteratively until the reconstructed images converge, with the assumption that the cardiac CINE images are inherently sparse in the r-f domain. A novel sampling strategy to reduce the normalized mean square error of the reconstructed images is proposed. RESULTS: The technique shows the least normalized mean square error among the four methods under comparison (zero filling, view sharing, k-t FOCUSS, and ITSC). Application of ITSC for multi-slice cardiac CINE imaging was tested with the number of slices of 2 to 8 in a single breath-hold, to demonstrate the clinical usefulness of the technique. CONCLUSIONS: Reconstructed images with the compression factors of 3-4 appear very close to the images without compression. Furthermore the proposed algorithm is computationally efficient and is stable without using matrix inversion during the reconstruction.
Magnetic Resonance Imaging, Cine*