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Federating research organisms to extend the reach of preclinical imaging research

A study on preclinical imaging involving several national research organisms (Inserm, CNRS, CEA, Universities) has produced MRI relaxometry maps for healthy rat brains. The impetus for that work is to be found in the France Life Imaging (FLI) initiative1 and its continuing momentum manifests today as the Small Animal Imaging Network (SAIN)2, which unites about ten French imaging facilities. The study, published in Frontiers in Neuroinformatics, demonstrates the feasibility of large-scale, multicenter3, MRI studies in the preclinical setting.

Published on 22 June 2020

Today, centers and clinics often collaborate to enable imaging studies involving hundreds and even thousands of human test subjects. In preclinical imaging research however, such multi-institution studies are much rarer, despite the fact that in this setting too, the pooling of larger amounts of experimental data would improve the statistical validity of obtained results. Of course, that statistical validity would depend also on the standardization of acquisition and analysis protocols, if multicenter preclinical imaging studies are to become a reality.

The Processing and Analysis of Multimodal Images team of MIRCen's Neurodegenerative Diseases Laboratory participated in a study aimed at demonstrating the feasibility and interest of collaborative multicenter preclinical imaging research. The raw magnetic resonance imaging (MRI) data of 40 healthy rat brains produced by two centers were pooled and analyzed in software developed at four centers. The study's authors focused on mapping T1 and T2 relaxation times at a magnetic field strength of 7 Tesla. Relaxometry maps permit the study of brain anatomy, particularly the contrast between its white and gray matter. By comparing and analyzing their results, the team was able to quantify observer variability between the two contributive centers. They also performed an evaluation of the influence of imaging processing steps on the resulting maps, using three different fitting algorithms from as many different centers. Finally, the relaxation times were studied in different brain regions of interest using image analysis solutions developed by two of the centers. The differences measured between T1 and T2 data were inconsequential. 

The study thus showed that multicenter research is feasible in the preclinical setting. The obtained relaxometry maps of healthy rat brains may prove useful as references for future works on signal intensity modifications in experimental pathological models. 

Top left: Individual sagittal and coronal T1-weighted raw images (inversion time: 247 ms) Top right: Individual sagittal and coronal T2-weighted raw images (echo time: 50 ms). Middle left: Sagittal and coronal views of the mean T1 relaxometry model (n=40 rats) Middle right: Sagittal and coronal views of the mean T2 relaxometry model (n=40 rats) Bottom left: Sagittal and coronal views of the T1-weighted model (40 rats; inversion time: 247 ms). Bottom right: Parcellation of the T1-weighted model (each brain region colored differently) (taken from the article).

© Frontiers in Neuroinformatics

1 To learn more about the FLI initiative

2 To learn more about SAIN

3  INSERM, U1216, Grenoble Institute of Neurosciences, Grenoble Alpes University / CNRS, CRMBM, Aix-Marseille University / UMR 9199, CNRS, CEA-MIRCen, Paris-Saclay University / CNRS, ICube-IMAGeS, University of Strasbourg

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