Dataset Information

Investigating the origin of pH-sensitive magnetization transfer ratio asymmetry MRI contrast during the acute stroke: Correction of T₁ change reveals the dominant amide proton transfer MRI signal.

ABSTRACT:

Purpose

Amide proton transfer (APT) MRI is promising to serve as a surrogate metabolic imaging biomarker of acute stroke. Although the magnetization transfer ratio asymmetry (MTR_asym ) has been used commonly, the origin of pH-weighted MRI effect remains an area of investigation, including contributions from APT, semisolid MT contrast asymmetry, and nuclear Overhauser enhancement effects. Our study aimed to determine the origin of pH-weighted MTR_asym contrast following acute stroke.

Methods

Multiparametric MRI, including T₁ , T₂ , diffusion and Z-spectrum, were performed in rats after middle cerebral artery occlusion. We analyzed the conventional Z-spectrum IΔωI0 and the apparent exchange spectrum RexΔω , being the difference between the relaxation-scaled inverse Z-spectrum and the intrinsic spinlock relaxation rate R1·cos2θ·I0IΔω-R1ρΔω . The ischemia-induced change was calculated as the spectral difference between the diffusion lesion and the contralateral normal area.

Results

The conventional Z-spectrum signal change at -3.5 ppm dominates that at +3.5 ppm (-1.16 ± 0.39% vs. 0.76 ± 0.26%, P < .01) following acute stroke. In comparison, the magnitude of ΔR_ex change at 3.5 ppm becomes significantly larger than that at -3.5 ppm (-2.80 ± 0.40% vs. -0.94 ± 0.80%, P < .001), with their SNR being 7.0 and 1.2, respectively. We extended the magnetization transfer and relaxation normalized APT concept to the apparent exchange-dependent relaxation image, documenting an enhanced pH contrast between the ischemic lesion and the intact tissue, over that of MTR_asym .

Conclusion

Our study shows that after the relaxation-effect correction, the APT effect is the dominant contributing factor to pH-weighted MTR_asym following acute stroke.

SUBMITTER: Wu L

PROVIDER: S-EPMC7402019 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Publications

Investigating the origin of pH-sensitive magnetization transfer ratio asymmetry MRI contrast during the acute stroke: Correction of T<sub>1</sub> change reveals the dominant amide proton transfer MRI signal.

Wu Limin L Jiang Liang L Sun Phillip Zhe PZ

Magnetic resonance in medicine 20200516 5

<h4>Purpose</h4>Amide proton transfer (APT) MRI is promising to serve as a surrogate metabolic imaging biomarker of acute stroke. Although the magnetization transfer ratio asymmetry (MTR<sub>asym</sub> ) has been used commonly, the origin of pH-weighted MRI effect remains an area of investigation, including contributions from APT, semisolid MT contrast asymmetry, and nuclear Overhauser enhancement effects. Our study aimed to determine the origin of pH-weighted MTR<sub>asym</sub> contrast followi ...[more]

PMID: 32416012

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Project description:ImportanceThe process of brain development in children with developmental delay is not well known. Amide proton transfer-weighted (APTw) imaging is a novel molecular magnetic resonance imaging (MRI) technique that can noninvasively detect cytosolic endogenous mobile proteins and peptides involved in the myelination process, and may be useful for providing insights into brain development.ObjectiveTo assess the contribution of amide proton transfer-weighted (APTw) imaging and magnetization transfer (MT) imaging to the evaluation of children with developmental delay (DD).MethodsFifty-one patients with DD were recruited to this study. The patients were divided into two groups according to the state of myelination assessed on conventional magnetic resonance imaging (MRI). Thirty patients (10 girls, 20 boys; age range: 1-8 months; median age: 4 months) in group A showed delayed myelination on MRI, while 21 patients (3 girls, 18 boys; age range: 12-36months; median age: 25months) in group B showed normal myelination on MRI. Fifty-one age- and sex-matched children with normal developmental quotient (DQ) and normal MRI appearance were recruited as normal controls. Three-slice APTw/MT axial imaging was performed at the level of the centrum semiovale, the basal ganglia and the pons. Quantitative data of the MT ratio (MTR) and APTw were analyzed for multiple brain regions. Independent-sample t-tests were used to compare differences in APTw and MTR signals between the two DD groups and normal controls. Analysis of Covariance was conducted to correct the statistical results. The level of statistical significance was set to P < 0.05.ResultsFor group A, the MTR values were lower in all regions (P = 0.004-0.033) compared with the normal controls, while the APTw values were higher in the pons, middle cerebellar peduncle, corpus callosum, frontal white matter, occipital white matter and centrum semiovale (P = 0.004-0.040 ). For Group B, the MTR values were slightly reduced, and the APTw values were slightly increased compared with the normal controls, but the differences were not statistically significant (P > 0.05).InterpretationFor DD patients showing signs of delayed myelination on MRI, MTR and APTw imaging can help to diagnose myelination delay by quantifying semi-solid macromolecules and cytosolic endogenous mobile proteins and peptides at a molecular level, providing a new method for comprehensive evaluation of DD. For DD patients with normal myelination on MRI, the clinical values of MTR and APTw imaging remain to be explored.

Project description:Objectives:To define normal signal intensity values of amide proton transfer-weighted (APTw) magnetic resonance (MR) imaging in different brain regions. Materials and Methods:Twenty healthy subjects (9 females, mean age 29 years, range 19 - 37 years) underwent MR imaging at 3 Tesla. 3D APTw (RF saturation B1,rms = 2 ?T, duration 2 s, 100% duty cycle) and 2D T2-weighted turbo spin echo (TSE) images were acquired. Postprocessing (image fusion, ROI measurements of APTw intensity values in 22 different brain regions) was performed and controlled by two independent neuroradiologists. Values were measured separately for each brain hemisphere. A subject was scanned both in prone and supine position to investigate differences between hemispheres. A mixed model on a 5% significance level was used to assess the effect of gender, brain region and side on APTw intensity values. Results:Mean APTw intensity values in the hippocampus and amygdala varied between 1.13 and 1.57%, in the deep subcortical nuclei (putamen, globus pallidus, head of caudate nucleus, thalamus, red nucleus, substantia nigra) between 0.73 and 1.84%, in the frontal, occipital and parietal cortex between 0.56 and 1.03%; in the insular cortex between 1.11 and 1.15%, in the temporal cortex between 1.22 and 1.37%, in the frontal, occipital and parietal white matter between 0.32 and 0.54% and in the temporal white matter between 0.83 and 0.89%. APTw intensity values were significantly impacted both by brain region (p < 0.001) and by side (p < 0.001), whereby overall values on the left side were higher than on the right side (1.13 vs. 0.9%). Gender did not significantly impact APTw intensity values (p = 0.24). APTw intensity values between the left and the right side were partially reversed after changing the position of one subject from supine to prone. Conclusion:We determined normal baseline APTw intensity values in different anatomical localizations in healthy subjects. APTw intensity values differed both between anatomical regions and between left and right brain hemisphere.

Dataset Information

Investigating the origin of pH-sensitive magnetization transfer ratio asymmetry MRI contrast during the acute stroke: Correction of T₁ change reveals the dominant amide proton transfer MRI signal.

Purpose

Methods

Results

Conclusion

Publications

Investigating the origin of pH-sensitive magnetization transfer ratio asymmetry MRI contrast during the acute stroke: Correction of T<sub>1</sub> change reveals the dominant amide proton transfer MRI signal.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

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Dataset Information

Investigating the origin of pH-sensitive magnetization transfer ratio asymmetry MRI contrast during the acute stroke: Correction of T1 change reveals the dominant amide proton transfer MRI signal.

Purpose

Methods

Results

Conclusion

Publications

Investigating the origin of pH-sensitive magnetization transfer ratio asymmetry MRI contrast during the acute stroke: Correction of T<sub>1</sub> change reveals the dominant amide proton transfer MRI signal.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Investigating the origin of pH-sensitive magnetization transfer ratio asymmetry MRI contrast during the acute stroke: Correction of T₁ change reveals the dominant amide proton transfer MRI signal.