Multiacquisition Variable-Resonance Image Combination Selective Can Improve Image Quality and Reproducibility for Metallic Implants in the Lumbar Spine.
The aim of this study is to evaluate how metallic artifacts in the lumbar spine can affect images obtained from magnetic resonance (MR) sequences. We performed a phantom experiment by scanning an agar containing an orthopedic metallic implant using 64-channel multidetector row computed tomography (CT) and a 3-tesla MR unit. We compared the reproducibility in each measurement, enlargement or reduction ratio of the CT and MR measurements, and signal deviation in each voxel from the control. The reproducibility on CT and multiacquisition variable-resonance image combination selective (MAVRIC SL) was good, but that on the other MR sequences showed either fixed bias or proportional bias. The reduction ratios of the distance between the nails were significantly smaller in MAVRIC SL than in the other MR sequences after CT measurements (p<0.001, respectively). MAVRIC SL was able to reduce the metallic artifact, permitting observation of the tissue surrounding the metal with good reproducibility.
Objectives White matter hyperintensities (WMHs) are implicated in the etiology of dementia. The underlying pathology of WMHs involves myelin and axonal loss due to chronic ischemia. We investigated myelin loss in WMHs and normal-appearing white matter (NAWM) in patients with various degrees of cognitive impairment using quantitative synthetic magnetic resonance imaging (MRI).
Infection and inflammation are a common occurrence with orthopaedic procedures. Anatomical modalities can show the transformation in the disease process; however, these may occur later when compared with functional imaging modalities that are more likely to identify early disease patterns. Various m
#2Robin Karr(MCW: Medical College of Wisconsin)H-Index: 3
Last. Kevin M. Koch(MCW: Medical College of Wisconsin)H-Index: 22
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Purpose To evaluate magnetic resonance imaging (MRI) artifacts near metallic spinal instrumentation using both conventional metal artifact reduction sequences (MARS) and 3D multispectral imaging sequences (3D-MSI). Materials and Methods Both MARS and 3D-MSI images were acquired in 10 subjects with titanium spinal hardware on a 1.5T GE 450W scanner. Clinical computed tomography (CT) images were used to measure the volume of the implant using seed-based region growing. Using 30–40 landmarks, the M...
Last. Kevin M. Koch(MCW: Medical College of Wisconsin)H-Index: 22
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Purpose By combining images created at distinct frequency offsets from the Larmor frequency, three-dimensional (3D) multispectral imaging (3D-MSI) sequences help overcome the large spatial frequency dispersion caused by metal implants. This frequency dispersion, however, varies with the implant size, orientation, and composition. Using a MAVRIC 3D-MSI acquisition, we sought to prospectively calibrate the spectral coverage needed for 3D-MSI scans. This calibration should offer a significant impro...
Purpose The diagnosis of osteomyelitis and implant-associated infections in patients with nonspecific laboratory or radiological findings is often unsatisfactory. We retrospectively evaluated the contributions of [18F]FDG PET and [18F]FDG PET/CT to the diagnosis of osteomyelitis and implant-associated infections, enabling timely and appropriate decision-making for further therapy options.
Purpose To characterize the fundamental limits of MRI near metallic implants on RF excitation, frequency encoding, and chemical shift–encoding water–fat separation. Methods Multicomponent three-dimensional (3D) digital models of a total hip and a total knee replacement were used to construct material-specific susceptibility maps. The fundamental limits and spatial relationship of imaging near metallic prostheses were investigated as a function of distance from the prosthetic surface by calculati...
#2Paul Malcolm(NNUH: Norfolk and Norwich University Hospital)H-Index: 13
Last. Andoni P. Toms(NNUH: Norfolk and Norwich University Hospital)H-Index: 30
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Artifact from metallic orthopedic prosthesis is caused by inhomogeneity in the B0 magnetic field, particularly in the frequency encoding direction. This results in signal voids, signal pileup, and geometric distortion. Advances in reducing this artifact allow us to assess the complications of joint replacement and improve imaging of nearby tissues such as within the pelvis. Selection of titanium implants and lower field strength MR units provide optimal conditions for artifact reduction. Convent...
#1M. Kretzschmar(UCSF: University of California, San Francisco)H-Index: 10
#2Lorenzo Nardo(UCSF: University of California, San Francisco)H-Index: 29
Last. Thomas M. Link(UCSF: University of California, San Francisco)H-Index: 103
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Objective The aim of our study was to evaluate the clinical feasibility and diagnostic value of a new MRI metal artefact reduction pulse sequence called MAVRIC-SL in a 3 T MRI environment.
OBJECTIVE. The objective of our study was to compare the multiacquisition variable-resonance image combination selective (MAVRIC SL) sequence with the 2D fast spin-echo (FSE) sequence for metal artifact reduction on 3-T MRI in patients with hip arthroplasty (HA). MATERIALS AND METHODS. Matched 2D FSE and MAVRIC SL images of 21 hips (19 patients with HA) were included in the study group. Paired image sets, composed of 13 coronal and 12 axial slices (total, 25 image sets), of the 21 hips were eval...
Abstract The diagnosis of infections associated with orthopedic implants is based on a combination of clinical signs, laboratory findings and imaging studies. There is no gold standard imaging technique: conventional radiography is indispensable, although 50% of the time the radiograph is normal. Computed tomography (CT), magnetic resonance imaging (MRI) and ultrasonography are valuable to detect soft tissue abnormalities. Bone scintigraphy (BS) rules out active infection. For infections involvi...