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[Preprint]. 2024 Nov 1:2024.10.28.24316292.
doi: 10.1101/2024.10.28.24316292.

Brain morphometrics correlations with age among 352 participants imaged with both 3T and 7T MRI: 7T improves statistical power and reduces required sample size

Cong Chu  1 , Tales Santini  1 , Jr-Jiun Liou  1 , Ann D Cohen  2 , Pauline M Maki  3 , Anna L Marsland  4 , Rebecca C Thurston  5 , Peter J Gianaros  6 , Tamer S Ibrahim  7
Affiliations

Brain morphometrics correlations with age among 352 participants imaged with both 3T and 7T MRI: 7T improves statistical power and reduces required sample size

Cong Chu et al. medRxiv. .

Update in

Abstract

Introduction: Magnetic resonance imaging (MRI) at 7 Telsa (7T) has superior signal-to-noise ratio to 3 Telsa (3T) but also presents higher signal inhomogeneities and geometric distortions. A key knowledge gap is to robustly investigate the sensitivity and accuracy of 3T and 7T MRI in assessing brain morphometrics. This study aims to (a) aggregate a large number of paired 3T and 7T scans to evaluate their differences in quantitative brain morphological assessment using a widely available brain segmentation tool, FreeSurfer, as well as to (b) examine the impact of normalization methods for subject variability and smaller sample sizes on data analysis.

Methods: A total of 452 healthy participants aged 29 to 68 were imaged at both 3T and 7T. Structural T1-weighted magnetization-prepared rapid gradient-echo (MPRAGE) images were processed and segmented using FreeSurfer. To account for head size variability, the brain volumes underwent intracranial volume (ICV) correction using the Residual (regression model) and Proportional (simple division to ICV) methods. The resulting volumes and thicknesses were correlated with age using Pearson correlation and false discovery rate correction. The correlations were also calculated in increasing sample size from 3 to the whole sample to estimate the sample size required to detect aging-related brain variation.

Results: 352 subjects (210 females) passed the image quality control with 100 subjects excluded due to excessive motion artifacts on 3T, 7T, or both. 7T MRI showed an overall stronger correlation between morphometrics and age and a larger number of significantly correlated brain volumes and cortical thicknesses. While the ICV is consistent between both field strengths, the Residual normalization method shows markedly higher correlation with age for 3T when compared with the Proportional normalization method. The 7T results are consistent regardless of the normalization method used.

Conclusion: In a large cohort of healthy participants with paired 3T and 7T scans, we compared the statistical performance in assessing age-related brain morphological changes. Our study reaffirmed the inverse correlation between brain volumes and cortical thicknesses and age and highlighted varying correlations in different brain regions and normalization methods at 3T and 7T. 7T imaging significantly improves statistical power and thus reduces required sample size.

Keywords: 3T; 7T; Magnetic resonance imaging; aging; brain morphometrics.

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Conflict of interest statement

Conflict of interest statement The authors declare no conflict of interest.

Figures

Figure 1.
Figure 1.. 7T has a stronger inverse correlation of total cortical grey matter volume, total subcortical grey matter volume, total white matter volume, and mean cortical thickness with age.
Brain morphometric correlations with age using 352 pairs of 3T and 7T MPRAGE scans, including the raw volumes (No Correction) and corrected for ICV using either residuals from regression model (Residual method) or division by ICV (Proportional method). Correlation between the ICV derived from 3T and 7T was shown to demonstrate consistent brain stripping results.
Figure 2.
Figure 2.. 7T shows more significant regions in correlation of total grey matter volume or mean cortical thickness with age.
Cortical regions corrected for ICV using Residual method and sex and found significant after FDR correction are shown with their respective Pearson correlation coefficient (positive correlation, blue; insignificant, grey; inverse correlation, red). Vessel-affected regions were removed. Cortical thicknesses were only corrected for sex.
Figure 3.
Figure 3.. 7T reduces required sample size in all regions, cortical volumes, subcortical volumes, and cortical thickness.
Number of significant regions in raw volumes (no correction) and corrected for ICV using both the Residual and Proportional methods observed with increasing sample size significantly differed between 3T and 7T.
Figure 4.
Figure 4.. 7T-derived ICV is consistent with that derived from 3T but more accurate in regional volumes.
Comparison between the ICV value calculated at 3T and 7T as well as the effect of different ICV correction (Residual and Proportional) methods. Ideal correction should result in no correlation between total cortical volume and ICV. Dashed lines represent 95% confidence intervals. For the Residual method, both correlations showed no significant non-zero slope. For the Proportional method, 7T data showed no significant non-zero slope (p = 0.17) while the 3T data showed non-zero slope (p < 0.0001).
Figure 5.
Figure 5.. Mean cortical volume annual rate of change measured at 0.32% for both 3T and 7T.
Cortical volumes were corrected for ICV using the Residual method, and the median age of the population used for this analysis is 52 years old.
See this image and copyright information in PMC

References

    1. Andrea N Sajewski T. S., DeFranco Anthony, Keil Boris, Jin Hecheng, Berardinelli Jacob, Li Jinghang, Chu Cong, Martins Tiago, and Ibrahim Tamer S. (2023). An Open 60-channel Tx/ 32-channel Rx RF Coil System for Routine Use at 7T ISMRM,
    1. Barisano G., Sepehrband F., Ma S., Jann K., Cabeen R., Wang D. J., Toga A. W., & Law M. (2019). Clinical 7 T MRI: Are we there yet? A review about magnetic resonance imaging at ultra-high field. Br J Radiol, 92(1094), 20180492. 10.1259/bjr.20180492 - DOI - PMC - PubMed
    1. Benjamini Y., & Hochberg Y. (1995). Controlling the False Discovery Rate: A Practical and Powerful Approach to Multiple Testing. Journal of the Royal Statistical Society. Series B (Methodological), 57(1), 289–300. http://www.jstor.org.pitt.idm.oclc.org/stable/2346101
    1. Choi U. S., Kawaguchi H., & Kida I. (2020). Cerebral artery segmentation based on magnetization-prepared two rapid acquisition gradient echo multi-contrast images in 7 Tesla magnetic resonance imaging. Neuroimage, 222, 117259. 10.1016/j.neuroimage.2020.117259 - DOI - PubMed
    1. Dickerson B. C., Bakkour A., Salat D. H., Feczko E., Pacheco J., Greve D. N., Grodstein F., Wright C. I., Blacker D., Rosas H. D., Sperling R. A., Atri A., Growdon J. H., Hyman B. T., Morris J. C., Fischl B., & Buckner R. L. (2009). The cortical signature of Alzheimer’s disease: regionally specific cortical thinning relates to symptom severity in very mild to mild AD dementia and is detectable in asymptomatic amyloid-positive individuals. Cereb Cortex, 19(3), 497–510. 10.1093/cercor/bhn113 - DOI - PMC - PubMed

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