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Diffusion Tensor Magnetic Resonance Imaging in the Analysis of Neurodegenerative Diseases
Published on: July 28, 2013
Microstructural abnormalities in multiple system atrophy as revealed by conventional and rotating frame relaxation
Antonietta Canna1, Silvia Mangia2, Shalom Michaeli2
1Montreal Neurological Institute and Hospital, the Neuro, McGill University, Montreal, QC, Canada.
Abstract:
Rotating frame relaxation (RFR) techniques provide robust and sensitive quantitative MRI (qMRI) metrics able to detect subtle alterations of brain tissue integrity in multiple neurological disorders. We performed a cross-sectional qMRI study in 16 patients with Multiple System Atrophy (MSA) and 14 age- and sex-matched healthy controls. The MRI protocol included the acquisition of RFR metrics, namely adiabatic T1ρ and T2ρ relaxation time constants, along with the acquisition of conventional relaxation metrics, namely R1 and R2*, and a semi-quantitative metric describing magnetization transfer (MT). Between-group comparisons of voxel-based and region-based outcomes were obtained both with and without accounting for the effect of atrophy. Significant brain atrophy was observed in the MSA patients in the white matter and grey matter of the cerebellum, and frontal white matter. On the other hand, group differences of virtually all relaxation metrics were observed for both voxel-wise and ROI analyses in many brain areas. These differences were reduced in spatial extent and/or effect size when the atrophy effect was accounted for. However, T1ρ values remained significantly longer in patients' ROIs encompassing both cerebellar grey matter and white matter, while MT, and R1 values were smaller. Cerebellar gray matter ROIs of patients also exhibited longer T2ρ and smaller R2*. Other voxel-wise group differences were still present after atrophy correction in several clusters, including among others, longer T1ρ in patients' putamen, and longer T1ρ and T2ρ and smaller MT in the patients' pons. Altogether, our findings suggest multiple processes of tissue integrity loss during the course of neurodegeneration that go beyond macrostructural alterations. We conclude that adiabatic T1ρ and T2ρ are valuable MRI metrics that expand the set of multi-parametric qMRI available to characterize the brain of MSA, providing additional and specific information on the brain tissue alterations occurring in this disease.
Insights
Rotating frame relaxation MRI techniques reveal subtle brain changes in Multiple System Atrophy (MSA). Adiabatic T1ρ and T2ρ metrics offer valuable insights into neurodegeneration beyond atrophy.
Area of Science:
- Neuroimaging
- Quantitative MRI
- Neurological Disorders
Background:
- Multiple System Atrophy (MSA) is a neurodegenerative disease characterized by progressive brain tissue damage.
- Quantitative MRI (qMRI) metrics, particularly Rotating Frame Relaxation (RFR) techniques, are sensitive to subtle changes in brain integrity.
- RFR metrics like adiabatic T1ρ and T2ρ, alongside conventional R1, R2*, and Magnetization Transfer (MT), can potentially differentiate between patients and controls.
Purpose of the Study:
- To investigate the utility of RFR metrics (adiabatic T1ρ, T2ρ) and conventional qMRI metrics (R1, R2*, MT) in characterizing brain tissue alterations in Multiple System Atrophy (MSA).
- To compare these metrics between MSA patients and healthy controls, both with and without accounting for brain atrophy.
- To determine if RFR metrics provide unique information on neurodegeneration in MSA.
Main Methods:
- Cross-sectional quantitative MRI study involving 16 patients with MSA and 14 age- and sex-matched healthy controls.
- Acquisition of adiabatic T1ρ, T2ρ, R1, R2*, and MT relaxation metrics.
- Voxel-based and region-based analyses comparing MSA patients and controls, with and without correction for brain atrophy.
Main Results:
- Significant brain atrophy was observed in MSA patients, particularly in the cerebellum and frontal white matter.
- Group differences in relaxation metrics were widespread, but their extent and effect size decreased after atrophy correction.
- Adiabatic T1ρ values remained significantly elevated in cerebellar regions of MSA patients, with longer T2ρ and smaller MT/R1 also observed in specific areas, indicating tissue alterations beyond atrophy.
Conclusions:
- Multiple processes contribute to tissue integrity loss in MSA, extending beyond macrostructural atrophy.
- Adiabatic T1ρ and T2ρ are valuable qMRI metrics that provide specific information on brain tissue alterations in MSA.
- Multi-parametric qMRI, including RFR techniques, enhances the characterization of neurodegenerative changes in MSA.
