Motion Correction (motion + correction)

Distribution by Scientific Domains


Selected Abstracts


Improved dynamic susceptibility contrast (DSC)-MR perfusion estimates by motion correction

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2007
Robert K. Kosior BSc
Abstract Purpose To investigate the effect of patient motion on quantitative cerebral blood flow (CBF) maps in ischemic stroke patients and to evaluate the efficacy of a motion-correction scheme. Materials and Methods Perfusion data from 25 ischemic stroke patients were selected for analysis. Two motion profiles were applied to a digital anthropomorphic brain phantom to estimate accuracy. CBF images were generated for motion-corrupted and motion-corrected data. To correct for motion, rigid-body registration was performed. The realignment parameters and mean CBF in regions of interest were recorded. Results All patient data with motion exhibited visibly reduced intervolume misalignment after motion correction. Improved flow delineation between different tissues and a more clearly defined ischemic lesion (IL) were achieved in the motion-corrected CBF. A significant difference occurred in the IL (P < 0.05) for patients with severe motion with an average difference between corrupted and corrected data of 4.8 mL/minute/100 g. The phantom data supported the patient results with better CBF accuracy after motion correction and high registration accuracy (<1 mm translational and <1° rotational error). Conclusion Motion degrades flow differentiation between adjacent tissues in CBF maps and can cause ischemic severity to be underestimated. A registration motion correction scheme improves dynamic susceptibility contrast (DSC)-MR perfusion estimates. J. Magn. Reson. Imaging 2007;26:1167,1172. © 2007 Wiley-Liss, Inc. [source]


Patient motion correction for multiplanar, multi-breath-hold cardiac cine MR imaging

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 5 2007
Piotr J. Slomka PhD
Abstract Purpose To correct for spatial misregistration of multi-breath-hold short-axis (SA), two-chamber (2CH), and four-chamber (4CH) cine cardiac MR (CMR) images caused by respiratory and patient motion. Materials and Methods Twenty CMR studies from consecutive patients with separate breath-hold 2CH, 4CH, and SA 20-phase cine images were considered. We automatically registered the 2CH, 4CH, and SA images in three dimensions by minimizing the cost function derived from plane intersections for all cine phases. The automatic alignment was compared with manual alignment by two observers. Results The processing time for the proposed method was <20 seconds, compared to 14,24 minutes for the manual correction. The initial plane displacement identified by the observers was 2.8 ± 1.8 mm (maximum = 14 mm). A displacement of ,5 mm was identified in 15 of 20 studies. The registration accuracy (defined as the difference between the automatic parameters and those obtained by visual registration) was 1.0 ± 0.9 mm, 1.1 ± 1.0 mm, 1.1 ± 1.2 mm, and 2.0 ± 1.8 mm for 2CH-4CH alignment and SA alignment in the mid, basal, and apical regions, respectively. The algorithm variability was higher in the apex (2.0 ± 1.9 mm) than in the mid (1.4 ± 1.4 mm) or basal (1.2 ± 1.2 mm) regions (ANOVA, P < 0.05). Conclusion An automated preprocessing algorithm can reduce spatial misregistration between multiple CMR images acquired at different breath-holds and plane orientations. J. Magn. Reson. Imaging 2007;25:965,973. © 2007 Wiley-Liss, Inc. [source]


Coronary MR angiography: Respiratory motion correction with BACSPIN

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2003
Christopher J. Hardy PhD
Abstract Purpose To improve the signal-to-noise ratio (SNR) of breath-held coronary magnetic resonance angiography (CMRA) without increasing the number or duration of breath holds. Materials and Methods In this BACSPIN (Breathing AutoCorrection with SPiral INterleaves) technique, a single breath-held electrocardiogram (ECG)-gated multi-slice interleaved-spiral data set is acquired, followed by repeated imaging of the same slices during free breathing. Each spiral interleaf from the breath-held data set is used as a standard for comparison with corresponding acquisitions at the same interleaf angle during free breathing. The most closely matched acquisitions are incorporated into a multi-slice, multi-average data set with increasing SNR over time. In-plane translations of the coronary artery can be measured and compensated for each accepted acquisition before combination with the other acquisitions. Results CMRA was performed on six volunteers, with improved SNR and minimal motional blurring. In some cases, breath holding could be dispensed with completely and the average respiratory position used as a reference. Conclusion BACSPIN provides a promising method for CMRA with improved SNR and limited breath-holding requirements. J. Magn. Reson. Imaging 2003;17:170,176. © 2003 Wiley-Liss, Inc. [source]


High spatial and temporal resolution cardiac cine MRI from retrospective reconstruction of data acquired in real time using motion correction and resorting

MAGNETIC RESONANCE IN MEDICINE, Issue 6 2009
Peter Kellman
Abstract Cine MRI is used for assessing cardiac function and flow and is typically based on a breath-held, segmented data acquisition. Breath holding is particularly difficult for patients with congestive heart failure or in pediatric cases. Real-time imaging may be used without breath holding or ECG triggering. However, despite the use of rapid imaging sequences and accelerated parallel imaging, real-time imaging typically has compromised spatial and temporal resolution compared with gated, segmented breath-held studies. A new method is proposed that produces a cardiac cine across the full cycle, with both high spatial and temporal resolution from a retrospective reconstruction of data acquired over multiple heartbeats during free breathing. The proposed method was compared with conventional cine images in 10 subjects. The resultant image quality for the proposed method (4.2 ± 0.4) without breath holding or gating was comparable to the conventional cine (4.4 ± 0.5) on a five-point scale (P = n.s.). Motion-corrected averaging of real-time acquired cardiac images provides a means of attaining high-quality cine images with many of the benefits of real-time imaging, such as free-breathing acquisition and tolerance to arrhythmias. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source]


Turboprop IDEAL: A motion-resistant fat,water separation technique

MAGNETIC RESONANCE IN MEDICINE, Issue 1 2009
Donglai Huo
Abstract Suppression of the fat signal in MRI is very important for many clinical applications. Multi-point water,fat separation methods, such as IDEAL (Iterative Decomposition of water and fat with Echo Asymmetry and Least-squares estimation), can robustly separate water and fat signal, but inevitably increase scan time, making separated images more easily affected by patient motions. PROPELLER (Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction) and Turboprop techniques offer an effective approach to correct for motion artifacts. By combining these techniques together, we demonstrate that the new TP-IDEAL method can provide reliable water,fat separation with robust motion correction. The Turboprop sequence was modified to acquire source images, and motion correction algorithms were adjusted to assure the registration between different echo images. Theoretical calculations were performed to predict the optimal shift and spacing of the gradient echoes. Phantom images were acquired, and results were compared with regular FSE-IDEAL. Both T1- and T2-weighted images of the human brain were used to demonstrate the effectiveness of motion correction. TP-IDEAL images were also acquired for pelvis, knee, and foot, showing great potential of this technique for general clinical applications. Magn Reson Med 61:188,195, 2009. © 2008 Wiley-Liss, Inc. [source]


Self-navigated motion correction using moments of spatial projections in radial MRI

MAGNETIC RESONANCE IN MEDICINE, Issue 2 2004
Edward Brian Welch
Abstract Interest in radial MRI (also known as projection reconstruction (PR) MRI) has increased recently for uses such as fast scanning and undersampled acquisitions. Additionally, PR acquisitions offer intrinsic advantages over standard two-dimensional Fourier transform (2DFT) imaging with respect to motion of the imaged object. It is well known that aligning each spatial domain projection's center of mass (calculated using the 0th and 1st moments) to the center of the field of view (FOV) corrects shifts caused by in-plane translation. In this work, a previously unrealized ability to determine the in-plane rotational motion of an imaged object using the 2nd moments of the spatial domain projections in conjunction with a specific projection angle acquisition time order is reported. We performed the correction using only the PR data itself acquired with the newly proposed projection angle acquisition time order. With the proposed view angle acquisition order, the acquisition is "self-navigating" with respect to both in-plane translation and rotation. We reconstructed the images using the aligned projections and detected acquisition angles to significantly reduce image artifacts due to such motion. The theory of the correction technique is described, and its effectiveness is demonstrated in phantom and in vivo experiments. Magn Reson Med 52:337,345, 2004. © 2004 Wiley-Liss, Inc. [source]


Online motion correction for diffusion-weighted imaging using navigator echoes: Application to RARE imaging without sensitivity loss

MAGNETIC RESONANCE IN MEDICINE, Issue 5 2001
David G. Norris
Abstract This article describes the first application of true online motion correction to diffusion-weighted RARE imaging. Two orthogonal navigator echoes were acquired and zeroth and first-order phase corrections applied in less than 8 ms between a diffusion-weighted magnetization preparation and data acquisition using the RARE sequence. The zeroth-order phase correction was realized by pulsing the system's B0 -coil: the first-order error corrected with appropriate magnetic field gradient pulses. Online correction ensured that no irreversible signal loss could occur in the imaging experiment. Diffusion-weighted images of the brain were obtained from healthy volunteers. EGG-triggered acquisition was applied at 400 ms after the R-wave. Data were acquired on a matrix of 256 × 256 with a RARE factor of 16 and a b -value of 804 smm,2. The images obtained with online motion correction showed a remarkably high image quality, while those acquired without motion correction were severely degraded by artifacts. Magn Reson Med 45:729,733, 2001. © 2001 Wiley-Liss, Inc. [source]


Twenty-five pitfalls in the analysis of diffusion MRI data,

NMR IN BIOMEDICINE, Issue 7 2010
Derek K. Jones
Abstract Obtaining reliable data and drawing meaningful and robust inferences from diffusion MRI can be challenging and is subject to many pitfalls. The process of quantifying diffusion indices and eventually comparing them between groups of subjects and/or correlating them with other parameters starts at the acquisition of the raw data, followed by a long pipeline of image processing steps. Each one of these steps is susceptible to sources of bias, which may not only limit the accuracy and precision, but can lead to substantial errors. This article provides a detailed review of the steps along the analysis pipeline and their associated pitfalls. These are grouped into 1 pre-processing of data; 2 estimation of the tensor; 3 derivation of voxelwise quantitative parameters; 4 strategies for extracting quantitative parameters; and finally 5 intra-subject and inter-subject comparison, including region of interest, histogram, tract-specific and voxel-based analyses. The article covers important aspects of diffusion MRI analysis, such as motion correction, susceptibility and eddy current distortion correction, model fitting, region of interest placement, histogram and voxel-based analysis. We have assembled 25 pitfalls (several previously unreported) into a single article, which should serve as a useful reference for those embarking on new diffusion MRI-based studies, and as a check for those who may already be running studies but may have overlooked some important confounds. While some of these problems are well known to diffusion experts, they might not be to other researchers wishing to undertake a clinical study based on diffusion MRI. Copyright © 2010 John Wiley & Sons, Ltd. [source]


Quantitative MRI for the assessment of bone structure and function,

NMR IN BIOMEDICINE, Issue 7 2006
Felix W. Wehrli
Abstract Osteoporosis is the most common degenerative disease in the elderly. It is characterized by low bone mass and structural deterioration of bone tissue, leading to morbidity and increased fracture risk in the hip, spine and wrist,all sites of predominantly trabecular bone. Bone densitometry, currently the standard methodology for diagnosis and treatment monitoring, has significant limitations in that it cannot provide information on the structural manifestations of the disease. Recent advances in imaging, in particular MRI, can now provide detailed insight into the architectural consequences of disease progression and regression in response to treatment. The focus of this review is on the emerging methodology of quantitative MRI for the assessment of structure and function of trabecular bone. During the past 10 years, various approaches have been explored for obtaining image-based quantitative information on trabecular architecture. Indirect methods that do not require resolution on the scale of individual trabeculae and therefore can be practiced at any skeletal location, make use of the induced magnetic fields in the intertrabecular space. These fields, which have their origin in the greater diamagnetism of bone relative to surrounding marrow, can be measured in various ways, most typically in the form of R2,, the recoverable component of the total transverse relaxation rate. Alternatively, the trabecular network can be quantified by high-resolution MRI (µ-MRI), which requires resolution adequate to at least partially resolve individual trabeculae. Micro-MRI-based structure analysis is therefore technically demanding in terms of image acquisition and algorithms needed to extract the structural information under conditions of limited signal-to-noise ratio and resolution. Other requirements that must be met include motion correction and image registration, both critical for achieving the reproducibility needed in repeat studies. Key clinical applications targeted involve fracture risk prediction and evaluation of the effect of therapeutic intervention. Copyright © 2006 John Wiley & Sons, Ltd. [source]