Correction of eddy‐current distortions in diffusion tensor images using the known directions and strengths of diffusion gradients

Zhuang, Jiancheng; Hrabě, Jan; Kangarlu, Alayar; Xu, Dongrong; Bansal, Ravi; Branch, Craig A.; Peterson, Bradley S.

doi:10.1002/jmri.20727

Cited by 114 publications

(101 citation statements)

References 17 publications

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“…It is unclear how this may have affected our study findings; however, no selection bias was identified with respect to clinical indications, due to exclusion of these lesions. DW imaging misregistration issues can potentially be avoided in future studies by performing DW imaging earlier during the MR imaging examination, improving patient comfort to reduce motion, and employing alternative pulse sequences or postprocessing techniques to reduce eddy current distortions (45)(46)(47). The low spatial resolution of DW imaging could affect the accuracy of lesion ADC measurements owing to partial volume averaging.…”

Section: Intra-and Interobserver Variabilitymentioning

confidence: 99%

Nonmalignant Breast Lesions: ADCs of Benign and High-Risk Subtypes Assessed as False-Positive at Dynamic Enhanced MR Imaging

Parsian¹,

Rahbar²,

Allison³

et al. 2012

Radiology

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Purpose:To evaluate the diffusion-weighted (DW) imaging characteristics of nonmalignant lesion subtypes assessed as false-positive findings at conventional breast magnetic resonance (MR) imaging. Materials and Methods:This HIPAA-compliant retrospective study had institutional review board approval, and the need for informed patient consent was waived. Lesions assessed as Breast Imaging Reporting and Data System category 4 or 5 at clinical dynamic contrast material-enhanced MR imaging that subsequently proved nonmalignant at biopsy were retrospectively reviewed. One hundred seventy-five nonmalignant breast lesions in 165 women were evaluated. Apparent diffusion coefficients (ADCs) from DW imaging (b = 0, 600 sec/mm 2 ) were calculated for each lesion and were compared between subtypes and with an ADC threshold of 1.81 3 10 23 mm 2 /sec (determined in a prior study to achieve 100% sensitivity). Results:Eighty-one (46%) lesions exhibited ADCs greater than the predetermined threshold. /sec; n = 23) was the most common lesion subtype with ADC below the threshold. Lymph nodes exhibited the lowest mean ADC of all nonmalignant lesions ([1.28 6 0.23] 3 10 23 mm 2 /sec; n = 4). High-risk lesions (atypical ductal hyperplasia and lobular neoplasia) showed significantly lower ADCs than other benign lesions (P , .0001) and were the most common lesions with ADCs below the threshold. Conclusion:Assessing ADC along with dynamic contrast-enhanced MR imaging features may decrease the number of avoidable false-positive findings at breast MR imaging and reduce the number of preventable biopsies.

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Section: Intra-and Interobserver Variabilitymentioning

confidence: 99%

Nonmalignant Breast Lesions: ADCs of Benign and High-Risk Subtypes Assessed as False-Positive at Dynamic Enhanced MR Imaging

Parsian¹,

Rahbar²,

Allison³

et al. 2012

Radiology

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“…Axial T2-weighted images were also acquired for echo-planar imaging distortion correction. Processing of diffusion-weighted images, including coregistration, correction for eddy currents and subject motion using a 12-mode affine transformation, 21 skull stripping, and normalization to the ICBM-DTI-81 coordinates, 22 was performed using TORTOISE (http://www.nitrc.org/projects/tortoise) 23 and MRI Studio 24 (www. MriStudio.org) software packages.…”

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confidence: 99%

Impaired corticopontocerebellar tracts underlie pseudobulbar affect in motor neuron disorders

et al. 2014

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Objective: The objectives of the study were (1) to determine the prevalence and characteristics of pseudobulbar affect (PBA) in patients with primary lateral sclerosis (PLS) and amyotrophic lateral sclerosis (ALS) in an outpatient clinic population, and (2) to test the hypothesis that damage of inputs to the cerebellum, leading to cerebellar dysmodulation, is associated with PBA.Methods: Chart review of all patients with PLS and ALS seen between 2000 and 2013. The examining neurologist documented the presence or absence of PBA in 87 patients. Fortyseven patients also had diffusion tensor imaging (DTI) studies. Tract-based spatial statistics were used to compare DTI of patients with and without PBA to identify altered white matter tracts associated with PBA.Results: Thirty-one of 50 patients with PLS and 12 of 37 patients with ALS had PBA. Psychiatric/emotional assessment found congruence between mood and affect during episodes, but excessive magnitude of the response. DTI studies of 25 PLS and 22 ALS patient brains showed reduced fractional anisotropy of the corticospinal and callosal white matter tracts in all patients. Patients with PBA additionally had increased mean diffusivity of white matter tracts underlying the frontotemporal cortex, the transverse pontine fibers, and the middle cerebellar peduncle.Conclusions: PBA is common in PLS. Imaging findings showing disruption of corticopontocerebellar pathways support the hypothesis that PBA can be viewed as a "dysmetria" of emotional expression resulting from cerebellar dysmodulation. Neurology ® 2014;83:620-627 GLOSSARY ALS 5 amyotrophic lateral sclerosis; ALSbi 5 amyotrophic lateral sclerosis with mild behavioral impairment; ALSci 5 amyotrophic lateral sclerosis with mild cognitive impairment; ALSFRS-R 5 Amyotrophic Lateral Sclerosis Functional Rating Scale-revised; BDI-II 5 Beck Depression Inventory-II; DRS-2 5 Mattis Dementia Rating Scale-2; DTI 5 diffusion tensor imaging; FA 5 fractional anisotropy; FSL 5 FMRIB's Software Library; PBA 5 pseudobulbar affect; PLS 5 primary lateral sclerosis; TFCE 5 threshold-free cluster enhancement; UCLA 5 University of California Los Angeles.Pseudobulbar affect (PBA) is a syndrome of involuntary emotional expression dissociated from one's true emotional experience.1 It occurs in several neurologic disorders, including amyotrophic lateral sclerosis (ALS).2,3 In one retrospective series, PBA occurred in 50% of patients with ALS. 4 There have been case reports of PBA in patients with primary lateral sclerosis (PLS), a motor neuron disorder variant with relatively selective degeneration of upper motor neurons. However, the prevalence of PBA in PLS has not been evaluated in a large patient series. 2,6 To assess the occurrence of PBA in PLS, we reviewed the charts of all patients seen in an upper motor neuron disorder clinic.Two hypotheses have been proposed regarding the neural circuits that produce PBA. Wilson 7 proposed that brainstem centers controlling laughter and crying were separately controlled by volitional a...

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“…Eddy currents can produce geometric distortions of contraction or dilation, shift and shear in diffusion-weighted images [9,18]. This artifact can be reduced by using a double refocusing SE sequence [19], by image postprocessing [20][21][22] or by using stimulated echo sequences [23]. Another type of artifact generated during diffusion studies is the susceptibility artifact caused by an inhomogeneous magnetic field when an EPI sequence is used to obtain data.…”

Section: Discussionmentioning

confidence: 99%

Diffusion anisotropy indexes are sensitive to selecting the EPI readout-encoding bandwidth at high-field MRI

Jahng

Weiner

Schuff

2008

Magnetic Resonance Imaging

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Diffusion tensor magnetic resonance imaging (DT-MRI) is generally performed using an echo planar imaging (EPI) acquisition to map directional water diffusion. However, the oscillating magnetic field gradients of the EPI acquisition can result in considerable mechanical vibrations, which lead, in turn, to magnetic field fluctuations causing Nyquist ghosting in the EPI data. The objective of this study was to investigate effects of EPI readout gradient modulation frequency, which is directly associated with the EPI readout bandwidth (BW), on the accuracy of DT-MRI measurements in a high magnetic field system. A spherical water phantom was used to study the relationship between the EPI BW and the Nyquist ghost for a spin-echo EPI acquisition with a matrix size of 128×128, complemented by diffusion sensitization gradients of up to b=800 s/mm 2 along six directions for DT-MRI. Nine volunteers (four males and five females) were studied using EPI at different BW acquisitions. Analysis of variance was used to investigate the EPI BW effects. The phantom studies demonstrated a systematic relationship between BWs and the intensities of Nyquist ghosts. In the human brain studies, EPI BW variations substantially corrupted diffusion anisotropy indexes (i.e., fractional anisotropy and relative anisotropy) (F=10.5, P=.0001) but were unrelated to diffusion-encoding directions (F=0.14, P=.98). It was possible to minimize BW dependence (F=1.48, P=.25) by tuning the modulation frequency of the EPI readout gradient. In conclusion, diffusion anisotropic indexes are sensitive to the readout BW of EPI due to associated Nyquist ghosting. However, the effect can be minimized by tuning the modulation frequency of the EPI readout gradient, that is, the EPI BW, to a range outside the harmonics of mechanical gradient vibrations.

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Correction of eddy‐current distortions in diffusion tensor images using the known directions and strengths of diffusion gradients

Cited by 114 publications

References 17 publications

Nonmalignant Breast Lesions: ADCs of Benign and High-Risk Subtypes Assessed as False-Positive at Dynamic Enhanced MR Imaging

Nonmalignant Breast Lesions: ADCs of Benign and High-Risk Subtypes Assessed as False-Positive at Dynamic Enhanced MR Imaging

Impaired corticopontocerebellar tracts underlie pseudobulbar affect in motor neuron disorders

Diffusion anisotropy indexes are sensitive to selecting the EPI readout-encoding bandwidth at high-field MRI

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