Background: Neurodegeneration is an incurable, debilitating process which presents a growing medical and economic challenge due to our aging population. Alzheimer’s disease is one of the most common neurodegenerative diseases. Objectives: Currently, there are no minimally invasive diagnostic tools which allow for early diagnosis or monitoring of the progression of disease in patients. Methods: The European EMPIR NeuroMet 15HLT04 project (2016 – 9) is helping to address these objectives by exploring innovative techniques for early diagnosis and monitoring, based on non-invasive magnetic resonance imaging approaches, and developing improved clinical assessment protocols focused on monitoring declining cognitive functions. Results: As a case study, the person-centred measurement of cognitive ability is examined, where better analysis of correlations with brain atrophy is enabled thanks to the Rasch metrological approach. A new model of the metrology of ordinal data, including performance metrics and restitution is presented. Conclusions: An example is given of how the Rasch invariant measure theory can improve contemporary studies of possible correlations between neurodegeneration in patients suffering from Alzheimer’s disease – specifically failing cognitive ability – and brain atrophy. It is the first time to our knowledge that the known distortions - revealed by the Rasch psychometric model - of measurement scales in common clinical instruments for cognitive assessment have been corrected for in correlation studies. Possibilities of higher resolution and more reliable clinical decisions open up. Acknowledgments The European Metrology Programme for Innovation & Research (EMPIR, Horizon2020, Art. 185) is jointly funded by the EMPIR participating countries within EURAMET (www.euramet.org) and the European Union in this EMPIR 15 HLT04 NeuroMet project (coordinator: LGC (UK)). Thanks are due, particularly, to Members of the EMPIR NeuroMet consortium. PROJECT WEBSITE http://www.lgcgroup.com/our-science/national-measurement-laboratory/european-metrology-programme-for-innovation-and-re/neuromet/#.WRHEO2dYrcs