T1 and proton density at 7 T in patients with multiple sclerosis: an initial study

Bluestein, Katharine T.; Pitt, David; Knopp, Michael V.; Schmalbrock, Petra

doi:10.1016/j.mri.2011.07.018

Cited by 16 publications

(13 citation statements)

References 21 publications

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“…This would also require better characterization of T 1 and T 2 values of cortical lesions at 7 T for the EPG simulations, as there is a paucity of literature on this subject. 21 …”

Section: Discussionmentioning

confidence: 99%

“…For all the simulations, the following values were assumed for relaxation parameters—WM, T 1 1100 milliseconds, T 2 45 milliseconds; GM, T 1 1960 milliseconds, T 2 55 milliseconds; cortical lesion, T 1 2400 milliseconds, T 2 120 milliseconds (J. Su, personal communication, 2013) 21 ; and WM lesion, T 1 2000 milliseconds, T 2 100 milliseconds. 22,23 A rectangular 1D object was modeled, as well as the k -space profile of the object modulated by the signal modulation from the EPG simulation for a given refocusing flip angle train.…”

Section: Methodsmentioning

confidence: 99%

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Optimization of Magnetization-Prepared 3-Dimensional Fluid Attenuated Inversion Recovery Imaging for Lesion Detection at 7 T

Saranathan¹,

Tourdias²,

Kerr³

et al. 2014

Investigative Radiology

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Purpose The aim of this study was to optimize the 3-dimensional (3D) fluid attenuated inversion recovery (FLAIR) pulse sequence for isotropic high-spatial-resolution imaging of white matter (WM) and cortical lesions at 7 T. Materials and Methods We added a magnetization-prepared (MP) FLAIR module to a Cube 3D fast spin echo sequence and optimized the refocusing flip angle train using extended phase graph simulations, taking into account image contrast, specific absorption rate (SAR), and signal-to-noise ratio (SNR) as well as T1/T2 values of the different species of interest (WM, grey matter, lesions) at 7 T. We also effected improved preparation homogeneity at 7 T by redesigning the refocusing pulse used in the MP segments. Two sets of refocusing flip angle trains—(a) an SNR-optimal and (b) a contrast-optimal set—were derived and used to scan 7 patients with Alzheimer disease/cognitive impairment and 7 patients with multiple sclerosis. Conventional constant refocusing flip MP-FLAIR images were also acquired for comparison. Lesion SNR, contrast, and lesion count were compared between the 2 optimized and the standard FLAIR sequences. Results Whole brain coverage with 0.8 mm3 isotropic spatial resolution in ~5-minute scan times was achieved using the optimized 3D FLAIR sequences at clinically acceptable SAR levels. The SNR efficiency of the SNR-optimal sequence was significantly better than that of conventional constant refocusing flip MP-FLAIR sequence, whereas the scan time was reduced more than 2-fold (~5 vs >10 minutes). The contrast efficiency of the contrast-optimal sequence was comparable with that of the constant refocusing flip sequence. Lesion load ascertained by lesion counting was not significantly different among the sequences. Conclusion Magnetization-prepared FLAIR-Cube with refocusing flip angle trains optimized for SNR and contrast can be used to characterize WM and cortical lesions at 7 Twith 0.8 mm3 isotropic resolution in short scan times and without SAR penalty.

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“…This would also require better characterization of T 1 and T 2 values of cortical lesions at 7 T for the EPG simulations, as there is a paucity of literature on this subject. 21 …”

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Optimization of Magnetization-Prepared 3-Dimensional Fluid Attenuated Inversion Recovery Imaging for Lesion Detection at 7 T

Saranathan¹,

Tourdias²,

Kerr³

et al. 2014

Investigative Radiology

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“…Very few studies have looked at the qMRI signature of CLs in vivo due to the difficulty in visualizing them [27, 28]. Combined post mortem MRI and histopathology are necessary to study the association between the qMRI signature of CLs and neuropathological substrates [18, 29].…”

Section: Introductionmentioning

confidence: 99%

Quantitative Magnetic Resonance Imaging of Cortical Multiple Sclerosis Pathology

Tardif

Bedell

Eskildsen

et al. 2012

Multiple Sclerosis International

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Although significant improvements have been made regarding the visualization and characterization of cortical multiple sclerosis (MS) lesions using magnetic resonance imaging (MRI), cortical lesions (CL) continue to be under-detected in vivo, and we have a limited understanding of the causes of GM pathology. The objective of this study was to characterize the MRI signature of CLs to help interpret the changes seen in vivo and elucidate the factors limiting their visualization. A quantitative 3D high-resolution (350 μm isotropic) MRI study at 3 Tesla of a fixed post mortem cerebral hemisphere from a patient with MS is presented in combination with matched immunohistochemistry. Type III subpial lesions are characterized by an increase in T1, T2 and M0, and a decrease in MTR in comparison to the normal appearing cortex (NAC). All quantitative MR parameters were associated with cortical GM myelin content, while T1 showed the strongest correlation. The histogram analysis showed extensive overlap between CL and NAC for all MR parameters and myelin content. This is due to the poor contrast in myelin content between CL and NAC in comparison to the variability in myelo-architecture throughout the healthy cortex. This latter comparison is highlighted by the representation of T1 times on cortical surfaces at several laminar depths.

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“…The empirically determined tissue parameters T1 and PD for WM, GM and cortical lesions (CL), and cerebrospinal (CSF) used in this study are listed in Table 1 [14]. Also listed are the average published T2* values for WM and GM [15,16].…”

Section: Methodsmentioning

confidence: 99%

Detecting cortical lesions in multiple sclerosis at 7 T using white matter signal attenuation

Bluestein

Pitt

Sammet

et al. 2012

Magnetic Resonance Imaging

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Cortical lesions have recently been a focus of multiple sclerosis (MS) MR research. In this study, we present a white matter signal attenuating sequence optimized for cortical lesion detection at 7 T. The feasibility of white matter attenuation (WHAT) for cortical lesion detection was determined by scanning eight patients (four relapsing/remitting MS, four secondary progressive MS) at 7 T. WHAT showed excellent gray matter–white matter contrast, and cortical lesions were hyperintense to the surrounding cortical gray matter, The sequence was then optimized for cortical lesion detection by determining the set of sequence parameters that produced the best gray matter–cortical lesion contrast in a 10-min scan. Despite the B1 inhomogeneities common at ultra-high field strengths, WHAT with an adiabatic inversion pulse showed good cortical lesion detection and would be a valuable component of clinical MS imaging protocols.

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T1 and proton density at 7 T in patients with multiple sclerosis: an initial study

Cited by 16 publications

References 21 publications

Optimization of Magnetization-Prepared 3-Dimensional Fluid Attenuated Inversion Recovery Imaging for Lesion Detection at 7 T

Optimization of Magnetization-Prepared 3-Dimensional Fluid Attenuated Inversion Recovery Imaging for Lesion Detection at 7 T

Quantitative Magnetic Resonance Imaging of Cortical Multiple Sclerosis Pathology

Detecting cortical lesions in multiple sclerosis at 7 T using white matter signal attenuation

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