Biexponential longitudinal relaxation in white matter: Characterization and impact on T<sub>1</sub> mapping with IR‐FSE and MP2RAGE
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MRI physics study of biexponential T1 relaxation; measurement reproducibility in the assay sense, not the reproducibility of research.
The study investigates MRI relaxation measurements and sequence parameters, not research reproducibility as a social or methodological practice.
MRI physics characterizing biexponential T1 relaxation to improve mapping is imaging-method development, not study of research practice.
Abstract
PURPOSE: Magnetization transfer in white matter (WM) causes biexponential relaxation, but most quantitative T1 measurements fit data assuming monoexponential relaxation. The resulting monoexponential T1 estimate varies based on scan parameters and represents a source of variation between studies, especially at high fields. In this study, we characterized WM T1 relaxation and performed simulations to determine how to minimize this deviation. METHODS: To characterize biexponential relaxation, four volunteers were scanned at 3T and 7T using inversion recovery fast spin echo (IR-FSE) with 13 inversion times (TIs). Three volunteers were scanned with IR-FSE using TIs chosen by simulations to reduce T1 deviation, and with MP2RAGE. RESULTS: At 3T, the biexponential relaxation has a short component of T1 = 48 ms (9%) and a long component of T1 = 939 ms. At 7T the short component is T1 = 57 ms (11%) and the long component is 1349 ms (89%). For IR-FSE, acquiring four TIs with a minimum of 150 ms (3T) or 200 ms (7T) yielded monoexponential T1 estimates that match the long component to within 10 ms. For MP2RAGE, significant differences (90 ms at 3T, 125 ms at 7T) remain at all parameter values. CONCLUSION: Many T1 mapping sequences yield robust estimates of the long T1 component with suitable choice of TIs, allowing reproducible, sequence-independent T1 values to be measured. However, this is not true of MP2RAGE in its current implementation. Magn Reson Med 75:2265-2277, 2016. © 2015 Wiley Periodicals, Inc.
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The record
- Venue
- Magnetic Resonance in Medicine
- Topic
- Advanced MRI Techniques and Applications
- Field
- Medicine
- Canadian institutions
- McGill UniversityMcGill University Health Centre
- Funders
- National Center for Research ResourcesNational Institute of Biomedical Imaging and BioengineeringNational Institutes of Health
- Keywords
- Nuclear magnetic resonanceRelaxation (psychology)Magnetization transferWhite matterChemistryNuclear medicineMagnetic resonance imagingPhysicsMedicineRadiology
- Has abstract in OpenAlex
- yes