Normative trajectories of R1, R2* and magnetic susceptibility in basal ganglia on healthy ageing

Quantitative MRI techniques, including R1, R2*, and magnetic susceptibility mapping, have emerged as promising tools for generating surrogate imaging markers of brain tissue microstructure, enabling non-invasive in vivo measurements associated with myelination and iron deposition. Gaining insights into how these quantitative measurements evolve throughout a normal lifespan can enhance our understanding of brain maturation processes and facilitate the study of disease-related microstructural changes by distinguishing pathological alterations from normal brain development. In this study, we established the normative trajectories of R1, R2*, and magnetic susceptibility in the basal ganglia at 3T. We used a healthy ageing cohort comprising 260 subjects with an evenly distributed age range and sex ratio throughout adulthood. Utilizing the non-parametric Gaussian Process Regression model to derive the normative trajectories, we found that R1 in these structures predominantly exhibit a quadratic shape over age, while R2* and magnetic susceptibility are primarily linear. We validated the normative trajectories of R2* and magnetic susceptibility using an independent cohort. Additionally, we demonstrated that the spatial distributions of the quantitative MRI parameters also change with age in the putamen and caudate nucleus. This study not only reinforces existing findings on the association between age and qMRI but also provides valuable resources for studying cognitive ageing, in conjunction with the behavioural data available in the same data collection. ### Competing Interest Statement The authors have declared no competing interest. * Pf : Parafascicularis thalami pc : Paracentral Ce : Centralis thalami Pu.l : Pulvinar thalami laterale Pu.m : Pulvinar thalami mediale Pu.o.v : Pulvinar thalami orale-ventralis V.c : Ventrocaudalis Li : Limitans thalami V.i.m : Ventrointermedius V.o.p : Ventrooralis posterior V.o.a : Ventrooralis anterior V.o.i : Ventrooralis internus Lpo : Lateropolaris thalami Fa : Fasciculosus thalami T.mth : Tractusmammillo-thalamicus mc in Lpoc La.m.o : Lamella medialis oralis S.pv : Substantia periventricularis mc in Ce F.M : Fasciculus retroflexus Meynertii V.o.m : Ventrooralismedialis Pu.ol : Pulvinar thalami oral laterale Pu.om : Pulvinar thalami orale mediale Pu.sf : Pulvinaris superficialis D.c : Dorso-caudalis D.im : Dorso-intermedii D.o : Dorso-orales thalami M : Dorsomedialis A.pr : Anteroprincipalis thalami CL : Centralis lateralis La.m.ip : Lamella medialis interpolaris LMM : Lamina medullaris medialis Cau : Caudate nucleus Pu : Putamen GPe : External globus pallidus GPi : Internal globus pallidus NAcc : Nucleus accumbens SNr : Substantia nigra pars reticulata SNc : Substantia nigra pars compacta RN : Red nucleus VP : Ventral pallidum STN : Subthalamic nucleus SD : Standard deviation TI : Inversion time TR : Repetition time TE : Echo time TA : Acquisition time GRE : Gradient echo imaging CI : Confidence interval