Relaxometry Vs Artefact Volume Measurements for Estimating the Number of Iron-Labelled Macrophages: in Vivo Testing in the Mouse Brain

Jean-Christophe Brisset^1,2, Monica Olivia Sigovan^1,2, Fabien Chauveau^1,2, Adrien Riou^1,2, Norbert Nighoghossian^1,2, Emmanuelle Canet-Soulas^1,2, Yves Berthezene^1,2, Marlene Wiart^1,2

The aim of this study was to compare 4 quantitative methods for estimating the number of iron-labelled cells injected in the mouse brain: T2, T2* relaxometry, and artefact volume measurement using negative and positive contrasts. Eight mice were stereotaxically injected with [500-7,500] iron-labelled cells and imaged at 4.7T. Bland-Altman and scatterplots were used to compare the T2 and T2*-based estimated number of cells, the artefact volumes, and the actual number of iron-labelled cells. T2 and T2* quantification failed to estimate the number of iron-labelled cell in-vivo, while measurement of the artefact volume gave promising results.