STrategically Acquired Gradient Echo (STAGE) imaging, part I: Creating enhanced T1 contrast and standardized susceptibility weighted imaging and quantitative susceptibility mapping

Chen, Yongsheng; Liu, Saifeng; Wang, Yu; Kang, Yan; Haacke, E. Mark

doi:10.1016/j.mri.2017.10.005

Cited by 85 publications

(93 citation statements)

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“…The original STAGE method consists of acquiring two dual echo scans acquired with a pair of optimal flip angles (FAs) (one smaller than the Ernst angle of white matter and the other angle larger) to produce proton density (PD) weighted and T1-weighted images. 11 For adaptation of STAGE to 0.35 T, we modified the protocol to acquire images with three echoes to improve the curve fitting for estimation of the R2* maps. Phase and magnitude data were then inputted into a postprocessing pipeline developed in MATLAB (The MathWorks, Inc., Natick, Massachusetts, United States).…”

Section: A Stage Methods and Optimizationmentioning

confidence: 99%

Rapid multicontrast brain imaging on a 0.35T MR‐linac

et al. 2020

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Purpose: Magnetic resonance-guided radiation therapy (MRgRT) has shown great promise for localization and real-time tumor monitoring. However, to date, quantitative imaging has been limited for low field MRgRT. This work benchmarks quantitative T1, R2*, and Proton Density (PD)mapping in a phantom on a 0.35 T MR-linac and implements a novel acquisition method, STrategically Acquired Gradient Echo (STAGE). To further validate STAGE in a clinical setting, a pilot study was undertaken in a cohort of brain tumor patients to elucidate opportunities for longitudinal functional imaging with an MR-linac in the brain. Methods: STAGE (two triple-echo gradient echo (GRE) acquisitions) was optimized for a 0.35T low-field MR-linac. Simulations were performed to choose two flip angles to optimize signal-tonoise ratio (SNR) and T1-mapping precision. Tradeoffs between SNR, scan time, and spatial resolution for whole-brain coverage were evaluated in healthy volunteers. Data were inputted into a STAGE processing pipeline to yield four qualitative images (T1-weighted, enhanced T1-weighted, protondensity (PD) weighted, and simulated FLuid-Attenuated Inversion Recovery (sFLAIR)), and three quantitative datasets (T1, PD, and R2*). A benchmarking ISMRM/NIST phantom consisting of vials with variable NiCl 2 and MnCl 2 concentrations was scanned using variable flip angles (VFA) (2-60 degrees) and inversion recovery (IR) methods at 0.35 T. STAGE and VFA T1 values of vials were compared to IR T1 values. As measures of agreement with reference values and repeatability, relative error (RE) and coefficient of variability (CV) were calculated, respectively, for quantitative MR values within the phantom vials (spheres). To demonstrate feasibility, longitudinal STAGE data (pretreatment, weekly, and~2 months post-treatment) were acquired in an IRB-approved pilot study of brain tumor cases via the generation of temporal and differential quantitative MRI maps. Results: In the phantom, RE of measured VFA T1 and STAGE relative to IR reference values were 7.0 AE 2.5% and 9.5 AE 2.2% respectively. RE for the PD vials was 8.1 AE 6.8% and CV for phantom R2* measurements was 10.1 AE 9.9%. Simulations and volunteer experiments yielded final STAGE parameters of FA = 50°/10°, 1 9 1 9 3 mm 3 resolution, TR = 40 ms, TE = 5/20/34 ms in 10 min (64 slices). In the pilot study of brain tumor patients, differential maps for R2* and T1 maps were sensitive to local tumor changes and appeared similar to 3 T follow-up MRI datasets. Conclusion: Quantitative T1, R2*, and PD mapping are promising at 0.35 T agreeing well with reference data. STAGE phantom data offer quantitative representations comparable to traditional methods in a fraction of the acquisition time. Initial feasibility of implementing STAGE at 0.35 T in a patient brain tumor cohort suggests that detectable changes can be observed over time. With confirmation in a larger cohort, results may be implemented to identify areas of recurrence and facilitate adaptive radiation therapy.

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Section: A Stage Methods and Optimizationmentioning

confidence: 99%

Rapid multicontrast brain imaging on a 0.35T MR‐linac

et al. 2020

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“…The ideal method would depend only on the presence of iron and not the presence of water. If there were a means to measure spin density (and hence water content), it would be possible to separate these two effects …”

Section: Mri‐based Methods For the Detection And Quantification Of Irmentioning

confidence: 99%

Iron deposition quantification: Applications in the brain and liver

Yan

Lin

et al. 2018

Magnetic Resonance Imaging

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“…An established imaging protocol was performed in the axial plane. 11 It includes: i) an interleaved two-point Dixon three-dimensional (3D) gradient recalled echo (GRE) scan for muscle fat fraction (FF); 12,13 ii) a highresolution 3D GRE scan for nerve fascicular cross-section area (fCSA); iii) the strategically acquired gradient echo (STAGE) imaging 14 for nerve longitudinal relaxation time (T1) and proton density (PD) mappings, which also generates the transmitter and receiver radiofrequency field maps for correcting heterogeneities in the T1, PD and magnetization transfer ratio (MTR) maps; and iv) two 3D GRE scans performed with and without MT pulses for nerve MTR and effective transverse relaxation time (T2star).…”

Section: Quantitative Magnetic Resonance Imaging (Qmri)mentioning

confidence: 99%

Fatigue in patients with hereditary neuropathy with liability to pressure palsies

Fritz

Chen

Waters

et al. 2020

Ann Clin Transl Neurol

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Objective Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) is caused by a heterozygous deletion of peripheral myelin protein‐22 (PMP22) gene resulting in focal sensorimotor deficits. Our lab has identified a disruption of myelin junctions in excessively permeable myelin that impairs action potential propagation. This mechanism is expected to cause fatigue in patients with HNPP. Therefore, the objective was to characterize fatigue in patients with HNPP and determine the relationship of fatigue to nerve pathology, disability, and quality of life. Methods Nine females with HNPP participated in a single visit that included genotyping, nerve conduction studies, neurological exam, quantitative magnetic resonance imaging, and a physical therapy exam incorporating upper and lower extremity function and survey measures of fatigue. This visit was followed by 2 weeks of ecological momentary assessment (wrist‐worn device) that captured fatigue ratings five times per day. Results Participants demonstrated mild neurological impairment (CMTNS: 5.7 ± 2.8), yet reported high fatigue levels (average fatigue intensity over 2 weeks: 5.9 out of 10). Higher fatigue levels were associated with poorer quality of life and more pain. Higher fatigue was associated with significantly greater distal nerve proton density changes on peripheral nerve MRI, which is in line with hyper‐permeable myelin in HNPP. Interpretation Fatigue is common and severe among patients with HNPP whose disabilities are minimal by conventional outcome measures. Therapeutic interventions targeting fatigue have the potential to improve quality of life and may serve as a robust outcome measure to show longitudinal changes for patients with HNPP.

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STrategically Acquired Gradient Echo (STAGE) imaging, part I: Creating enhanced T1 contrast and standardized susceptibility weighted imaging and quantitative susceptibility mapping

Cited by 85 publications

References 50 publications

Rapid multicontrast brain imaging on a 0.35T MR‐linac

Rapid multicontrast brain imaging on a 0.35T MR‐linac

Iron deposition quantification: Applications in the brain and liver

Fatigue in patients with hereditary neuropathy with liability to pressure palsies

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