This is an interventional, multicenter, prospective study involving healthy volunteers, to primarily assess the reproducibility of multiparametric renal MRI on 1.5T scanners. The study is also aimed at assessing possible differences in renal MRI reproducibility on 1.5T MRI scanners by sex and age, and assessing possible differences in renal MRI reproducibility across field strengths (1.5T vs 3T) in the subgroup of subjects enrolled in both RESPECT clinical study and in the current subproject.

Over the past decade, renal Magnetic Resonance Imaging (MRI) has emerged as a promising non-invasive technique for improved understanding and characterisation of renal pathophysiology.

Despite renal MRI potential to address several key clinical questions, current methodological differences across studies hinder reliable comparisons of the results, which can only be regarded as preliminary. Widely accepted normative values of renal MRI measures to establish benchmarks for early diagnosis, prognosis or treatment planning are not available. Standardization of acquisition and processing protocols across centres is therefore needed, and this is a necessary preliminary step towards multiparametric renal MRI wider use in clinical research and ultimate adoption in clinical practice.

The ongoing "Exploratory multicentre clinical study to assess repeatability, reproducibility, acceptability and clinical validity of multiparametric renal Magnetic Resonance Imaging (RESPECT Trial, NCT05229263)" trial will provide relevant information on repeatability and reproducibility of MRI measures obtained from multiparametric MRI scans acquired on 3T scanners, that represent the state-of-the-art for clinical research. However, 3T MRI scanners are not available in most clinical centres, where instead lower-field (1.5T) MRI scanners are much more common. Investigating reproducibility of renal MRI measures on 1.5T scanners and assessing possible differences in reproducibility across magnetic field strength would be needed towards translation of the results of the RESPECT clinical study to clinics.

The possible advantages that can derive from participating in the present research are essentially linked to the possibility to specifically assess the renal function with multiparametric MRI, that is not part of the routine clinical practice. More generally, in the long term, it will be possible for CKD patients to benefit from the results of this study that is aimed at demonstrating the reproducibility and the clinical validity of multiparametric MRI.

Participation in the study will not entail any additional risk to subjects' health. All clinical MRI safety procedures will be strictly followed. Indeed, multiparametric MRI acquisitions required by this research will be performed without the administration of contrast media and do not present risks in either short or long term.

Inclusion Criteria:

• Provision of written informed consent prior to any study specific procedures
• Male and female subjects aged [18-70] years
• Office SBP values < 140 mmHg and DBP values ≤ 90 mmHg, under no antihypertensive therapy
• Normal renal function defined as: estimated glomerular filtration rate [eGFR] ≥ 60mL/min/1.73m2 (using CKD-EPI Creatinine Equation)
• Negative result upon urine testing for haematuria or proteinuria.

Exclusion Criteria:

• Previous enrollment in the present substudy
• Contraindications to MRI including caustrophobia, pregnancy, cardiac pacemakers or other MRI-incompatible prostheses
• Ongoing therapy (e.g. for diabetes, dyslipidemia, or any acute disease)
• Past or current oncological pathology