Inner volume MR imaging: technical concepts and their application.

Feinberg, David; Hoenninger, J; Crooks, Lawrence E.; Kaufman, L; Watts, J C; Arakawa, M

doi:10.1148/radiology.156.3.4023236

Cited by 204 publications

(215 citation statements)

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“…Magnetic field inhomogeneity was minimized by using an image-based shimming approach (Poole and Bowtell, 2008). For the acquisition of functional time-series, high resolution (1 mm isotropic) multi-slice GE-EPI data were acquired with outer volume suppression in the phase-encoding direction (Feinberg et al, 1985;Pfeuffer et al, 2002a) (Fig. 3a).…”

Section: Data Acquisitionmentioning

confidence: 99%

Functional quantitative susceptibility mapping (fQSM)

et al. 2014

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Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) is a powerful technique, typically based on the statistical analysis of the magnitude component of the complex time-series. Here, we additionally interrogated the phase data of the fMRI time-series and used quantitative susceptibility mapping (QSM) in order to investigate the potential of functional QSM (fQSM) relative to standard magnitude BOLD fMRI. High spatial resolution data (1 mm isotropic) were acquired every 3 seconds using zoomed multi-slice gradient-echo EPI collected at 7 T in single orientation (SO) and multiple orientation (MO) experiments, the latter involving 4 repetitions with the subject's head rotated relative to B0. Statistical parametric maps (SPM) were reconstructed for magnitude, phase and QSM time-series and each was subjected to detailed analysis. Several fQSM pipelines were evaluated and compared based on the relative number of voxels that were coincidentally found to be significant in QSM and magnitude SPMs (common voxels). We found that sensitivity and spatial reliability of fQSM relative to the magnitude data depended strongly on the arbitrary significance threshold defining "activated" voxels in SPMs, and on the efficiency of spatiotemporal filtering of the phase time-series. Sensitivity and spatial reliability depended slightly on whether MO or SO fQSM was performed and on the QSM calculation approach used for SO data. Our results present the potential of fQSM as a quantitative method of mapping BOLD changes. We also critically discuss the technical challenges and issues linked to this intriguing new technique. seconds using zoomed multi-slice gradient-echo EPI collected at 7 T in single orientation (SO) and multiple orientation (MO) experiments, the latter involving 4 repetitions with the subject's head rotated relative to B 0 . Statistical parametric maps (SPM) were reconstructed for magnitude, phase and QSM timeseries and each was subjected to detailed analysis. Several fQSM pipelines were evaluated and compared based on the relative number of voxels that were coincidentally found to be significant in QSM and magnitude SPMs (common voxels). We found that sensitivity and spatial reliability of fQSM relative to the magnitude data depended strongly on the arbitrary significance threshold defining "activated" voxels in SPMs, and on the efficiency of spatio-temporal filtering of the phase time-series. Sensitivity and spatial reliability depended slightly on whether MO or SO fQSM was performed and on the QSM calculation approach used for SO data.

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Section: Data Acquisitionmentioning

confidence: 99%

Functional quantitative susceptibility mapping (fQSM)

et al. 2014

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“…A zonal oblique multislice EPI (ZOOM-EPI) technique with fat and CSF suppression was introduced (6 -9) to reduce susceptibility artifacts and improve signal quality. ZOOM-EPI was modified from the inner volume (IV) technique (22) by applying 90°slice-selective and 180°refocusing radiofrequency (RF) pulses on angled planes. Only the intersection volume of these planes was refocused and imaged.…”

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confidence: 99%

Toward a practical protocol for human optic nerve DTI with EPI geometric distortion correction

Techavipoo

Okai

Lackey

et al. 2009

Magnetic Resonance Imaging

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Purpose: To develop a practical protocol for diffusion tensor imaging (DTI) of the human optic nerve with echo planar imaging (EPI) geometric distortion correction. Materials and Methods:A conventional DTI protocol was modified to acquire images with fat and cerebrospinal fluid (CSF) suppression and field inhomogeneity maps of contiguous coronal slices covering the whole brain. The technique was applied to healthy volunteers and multiple sclerosis patients with and without a history of unilateral optic neuritis. DTI measures and optic nerve tractography before and after geometric distortion correction were compared. Diffusion measures from left and right or from affected and unaffected eyes in different subject cohorts were reported. Results:The image geometry after correction closely resembled reference anatomical images. Optic nerve tractography became feasible after distortion correction. The diffusion measures from the healthy volunteers were in good agreement with the literature. Statistically significant differences were found in the fractional anisotropy and orthogonal eigenvalues between affected and unaffected eyes in optic neuritis patients with poor recovery. The diffusion measures before and after geometric distortion correction were not significantly different. For cohorts without optic neuritis, the difference between diffusion measures from left and right eyes was not statistically significant. Conclusion:The proposed technique could provide a practical DTI protocol to study the human optic nerve. MAGNETIC RESONANCE DIFFUSION TENSOR IMAG-ING (DTI) (1) has become a well-known clinical research tool to investigate brain tissue microstructure in vivo. DTI provides quantitative measures reflecting the integrity of the axonal fiber tracts in the central nervous system (CNS) via observation of water diffusion anisotropy. This information allows tractography of the fiber bundles suggesting connections between cortical regions. DTI has been applied to study changes associated with neurodevelopmental disorders and changes due to trauma and neurodegenerative diseases (2,3).DTI of the human optic nerve has been explored by many research groups (4 -17). As a pure white matter tract and most of its course being structurally isolated from the rest of the CNS, the optic nerve can serve as a unique structure to study the changes in the CNS due to multiple sclerosis (MS) and optic neuritis (ON). For example, acute inflammation with visual impairment is a first clinical presentation of CNS demyelination. About 20%-30% of patients with this symptom will develop MS and nearly 50% of the MS patients will develop ON (18). With a reliable assessment of visual function and the quantitative measurements from DTI, the impact of injuries and diseases to the optic nerves can be closely studied. However, DTI of the optic nerves is challenging because of their small diameter, confounding signals from surrounding fat tissue and cerebrospinal fluid (CSF), magnetic susceptibility gradients due to adjacent sinuses and bony structu...

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Section: Discussionmentioning

confidence: 99%

“…Using perpendicular 90°and 180°selection gradients, the 3D slab can be defined in two dimensions, leaving the tissue outside unexcited; hence, the FOV can be reduced in the primary phase-encode direction without leading to wraparound. The reduced FOV enables fewer phaseencoding steps to be used to spatially resolve that direction, leading to reduced imaging time (3,8,15).Two other 3D techniques for arterial wall imaging are 3D GraSE (gradient-and spin-echo) (16) and, more recently, 3D balanced SSFP (steady-state with free precession) (17)(18)(19). The SSFP sequence has performed well in terms of contrast-to-noise ratio.…”

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confidence: 99%

“…Spatial encoding is performed in 3D by using additional phase encoding in the direction perpendicular to the selected slab, along with an additional dimension of Fourier transformation for image reconstruction (14). The 3D images have an inherently higher signal-to-noise ratio (SNR), so fewer cardiac cycles are needed than with 2D to produce similar image quality at the same voxel size (8,15). In theory, the SNR advantage of 3D over 2D is ͌N, where N is the number of 3D phase-encode steps in the partition direction.…”

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Comparison of 2D and multislab 3D magnetic resonance techniques for measuring carotid wall volumes

Keenan

Grasso

Locca

et al. 2008

Magnetic Resonance Imaging

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Purpose: To compare a multislab three-dimensional volume-selective fast spin-echo (FSE) magnetic resonance (MR) sequence with a routine two-dimensional FSE sequence for quantification of carotid wall volume. Materials and Methods:One hundred normal subjects (50 men, mean age 44.6 years) underwent carotid vessel wall MR using 2D and 3D techniques. Carotid artery total vessel volume, lumen volume, wall volume, and wall/outer wall (W/OW) ratio were measured over 20 contiguous slices. Two-(2D) and three-dimensional (3D) results were compared. Results:The mean difference between 2D and 3D datasets (as a percentage of the mean absolute value) was 1.7% for vessel volume, 4.9% for lumen volume, 4.7% for wall volume, and 5.8% for W/OW ratio. There was good correlation between 2D and 3D models for total vessel volume (R 2 ϭ 0.93, P Ͻ 0.001), lumen area (R 2 ϭ 0.92, P Ͻ 0.001), and wall volume (R 2 ϭ 0.77, P Ͻ 0.001). The correlation for the W/OW ratio was weaker (R 2 ϭ 0.30; P Ͻ 0.001). The signalto-noise ratio (SNR) for the 3D technique was 2.1-fold greater than for the 2D technique (P Ͻ 0.001). When using the 3D sequence, scan time was reduced by 63%. Conclusion:Multislab volume selective 3D FSE carotid arterial wall imaging performs similarly to a conventional 2D technique, but with over twice the SNR and substantially reduced scan time. CARDIOVASCULAR MAGNETIC RESONANCE (MR) is a good technique for assessing atherosclerosis in the carotid artery, with much development over the last 15 years in plaque characterization and assessment of the structure and function of the arterial wall (1-6). Quantitative carotid wall imaging typically requires a stack of two-dimensional (2D) images, which can be contoured and analyzed. Acquisition protocols vary, but scan times of the order of 1 hour are common so as to cover an adequate length of the carotid artery with contiguous slices. Long scan times limit the applicability of the technique. As scan times increase, patient comfort and acceptability decrease, and patient movement increases, leading to image degradation from movement artifact (7). Long scan times also limit the feasibility of using carotid MR in large clinical studies. To reduce the scan time, a localized three-dimensional (3D) fast spinecho (FSE) sequence for carotid artery imaging has been developed and validated (8 -13).In conventional 3D imaging, rather than a single slice, a slab of tissue is excited by the radiofrequency (RF) pulse. Spatial encoding is performed in 3D by using additional phase encoding in the direction perpendicular to the selected slab, along with an additional dimension of Fourier transformation for image reconstruction (14). The 3D images have an inherently higher signal-to-noise ratio (SNR), so fewer cardiac cycles are needed than with 2D to produce similar image quality at the same voxel size (8,15). In theory, the SNR advantage of 3D over 2D is ͌N, where N is the number of 3D phase-encode steps in the partition direction. Using perpendicular 90°and 180°selection gradients, the 3D slab can ...

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Inner volume MR imaging: technical concepts and their application.

Cited by 204 publications

References 0 publications

Functional quantitative susceptibility mapping (fQSM)

Functional quantitative susceptibility mapping (fQSM)

Toward a practical protocol for human optic nerve DTI with EPI geometric distortion correction

Comparison of 2D and multislab 3D magnetic resonance techniques for measuring carotid wall volumes

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