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Systematic evaluation of the impact of defacing on quality and volumetric assessments on T1-weighted MR-images - 19/03/21

Doi : 10.1016/j.neurad.2021.03.001 
Gaurav Vivek Bhalerao a, b, d, 1, Pravesh Parekh a, c, d, 1, Jitender Saini e, Ganesan Venkatasubramanian a, b, d, , John P. John a, c, d,

the ADBS consortium2

  List of collaborating authors are listed in Appendix Appendix A.
Biju Viswanath, Naren P. Rao, Janardhanan C. Narayanaswamy, Palanimuthu T. Sivakumar, Arun Kandasamy, Muralidharan Kesavan, Urvakhsh Meherwan Mehta, Odity Mukherjee, Meera Purushottam, Ramakrishnan Kannan, Bhupesh Mehta, Thennarasu Kandavel, B. Binukumar, Deepak Jayarajan, A. Shyamsundar, Sydney Moirangthem, K.G. Vijay Kumar, Jayant Mahadevan, Bharath Holla, Jagadisha Thirthalli, Prabha S. Chandra, Bangalore N. Gangadhar, Pratima Murthy, Mitradas M. Panicker, Upinder S. Bhalla, Sumantra Chattarji, Vivek Benegal, Mathew Varghese, Janardhan Y.C. Reddy, Padinjat Raghu, Mahendra Rao, Sanjeev Jain

a ADBS Neuroimaging Centre, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India 
b Translational Psychiatry Lab, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India 
c Multimodal Brain Image Analysis Laboratory, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India 
d Departments of Psychiatry, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India 
e Department of Neuroimaging and Interventional Radiology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India 

Corresponding author at: Translational Psychiatry Lab, Department of Psychiatry, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore 560029, India.Translational Psychiatry LabDepartment of PsychiatryNational Institute of Mental Health and Neurosciences (NIMHANS)Bangalore560029India⁎⁎Corresponding author at: Multimodal Brain Image Analysis Laboratory, Department of Psychiatry, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore 560029, India.Multimodal Brain Image Analysis LaboratoryDepartment of PsychiatryNational Institute of Mental Health and Neurosciences (NIMHANS)Bangalore560029India
Sous presse. Épreuves corrigées par l'auteur. Disponible en ligne depuis le Friday 19 March 2021

Graphical abstract




Le texte complet de cet article est disponible en PDF.

Highlights

Removal of the facial features (defacing) protects privacy of the study participants.
Post-defacing, quantitative measures are expected to remain unchanged.
We compared volumetric and quality measures post-defacing for four defacing methods.
Most volumetric and quality measures changed significantly post-defacing.
Choice of defacing method can impact reproducibility of quantitative results.

Le texte complet de cet article est disponible en PDF.

Abstract

Background and purpose

Facial features can be potentially reconstructed from structural magnetic resonance images, thereby compromising the confidentiality of study participants. Defacing methods can be applied to MRI images to ensure privacy of study participants. These methods remove facial features, thereby rendering the image unidentifiable. It is commonly assumed that defacing would not have any impact on quantitative assessments of the brain. In this study, we have assessed the impact of different defacing methods on quality and volumetric estimates.

Materials and methods

We performed SPM-, Freesurfer-, pydeface, and FSL-based defacing on 30 T1-weighted images. We statistically compared the change in quality measurements (from MRIQC) and volumes (from SPM, CAT, and Freesurfer) between non-defaced and defaced images. We also calculated the Dice coefficient of each tissue class between non-defaced and defaced images.

Results

Almost all quality measurements and tissue volumes changed after defacing, irrespective of the method used. All tissue volumes decreased post-defacing for CAT, but no such consistent trend was seen for SPM and Freesurfer. Dice coefficients indicated that segmentations are relatively robust; however, partial volumes might be affected leading to changed volumetric estimates.

Conclusion

In this study, we demonstrated that volumes and quality measurements get affected differently by defacing methods. It is likely that this will have a significant impact on the reproducibility of experiments. We provide suggestions on ways to minimize the impact of defacing on outcome measurements. Our results warrant the need for robust handling of defaced images at different steps of image processing.

Le texte complet de cet article est disponible en PDF.

Abbreviations : CJV, CNR, QI, EFC, FBER, INU, WM2MAX, TIV, DC

Keywords : Defacing, Structural MRI, Reproducibility, Neuroimaging, Quality assessment, Quantitative assessment


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