A method is disclosed for providing a correcting factor for the dilution of measurements of at least one biomarker in cerebrospinal fluid (CSF). The method comprises providing semi-automated measurements of the ventricular system by MRI scans using quantitative anatomical protocols, determining a measurement of biomarker levels in CSF that has been extracted, correcting the measurement of the level of said at least one biomarker'according to the ventricular size, and providing a corrected result of the measurement determined in step (b), said corrected result accounting for concentration dilution due to the change in ventricular size. The method is particularly suited for the measurement of all biomarkers found in the CSF, such as those associated with mild cognitive impairment (MCI) and Alzheimer's Disease.