A Multicenter Preclinical MRI Study: Definition of Rat Brain Relaxometry Reference Maps

Abstract

Similarly to human population imaging, there are several well-founded motivations for animal population imaging, the most notable being the improvement of the validity of statistical results by pooling a sufficient number of animal data provided by different imaging centers. In this paper, we demonstrate the feasibility of such a multicenter animal study, sharing raw data from forty rats and processing pipelines between four imaging centers. As specific use case, we considered the estimation of T1 and T2 maps for the healthy rat brain at 7T. We quantitatively report about the variability observed across two data provider centers and evaluate the influence of image processing steps on the final maps, by using three fitting algorithms from three centers.Finally, to derive relaxation time values per brain area, two multi-atlas segmentation pipelines from different centers were executed on two different platforms. In this study, the impact of the acquisition was 2.21% (not significant) and 9.52% on T1 and T2 estimates while the impact of the data processing pipeline was not significant (1.04% and 3.33%, respectively). In addition, the computed normality values can serve as relaxometry reference maps to explore differences to animal models of pathologies.

T1 Mapping From MPRAGE Acquisitions: Application to the Measurement of the Concentration of Nanoparticles in Tumors for Theranostic Use

“…The density correction performed for the brain tissue provided values close to the literature values with a differentiation of the thalamus from the cortex or hippocampus. 32 The elevated values obtained without density correction illustrate the importance of density correction when an external reference is used. As with the in vitro measurements, the T 1 maps obtained from the MPRAGE sequence illustrate the potential of the approach, with a spatial resolution and measurement accuracy superior to that of an SR sequence, which is poorly adapted to in vivo measurements.…”

“…The T 1 values obtained from ROIs drawn in different brain regions are summarized in Table 1, including also typical T 1 values reported in the literature. 32 As a point of comparison, the T 1 values that were obtained without correcting for the proton density in the thalamus, cortex, and hippocampus amounted to 2356 AE 135 msec, 2676 AE 175 msec, and 2535 AE 155 msec, respectively.…”

Small Animal Shanoir (SAS) A Cloud-Based Solution for Managing Preclinical MR Brain Imaging Studies

“…It showed the coherence of the final computed maps when the acquisition sequence parameters are optimized and harmonized between centers (Deruelle et al, 2020). Using SAS, the study demonstrates the feasibility of pooling animal data from different centers.…”

D* from diffusion MRI reveals a correspondence between ventricular cerebrospinal fluid volume and flow in the ischemic rodent model

“…First, the ventricular ROIs were obtained using a thresholded T 2 map ( T 2 > 0.65 s). 31 However, because the mask of the thresholded T 2 map contains both ventricular and edematous regions with high T 2 values, the ADC map was used to exclude the edematous regions. The high ADC mask (ADC > 0.8 × 10 −3 mm 2 /s) was multiplied by the thresholded T 2 map mask to obtain the ventricular ROI.…”