In vivo quantification of magnetically labelled cells by MRI relaxometry. (21st October 2016)

• Record Type: Journal Article
• Authors: Gimenez, Ulysse; Lajous, Hélène; El Atifi, Michèle; Bidart, Marie; Auboiroux, Vincent; Fries, Pascal Henry; Berger, François; Lahrech, Hana
• Is Part Of: Contrast media & molecular imaging. Volume 11:Number 6(2016:Nov./Dec.)
• Page Start: 535
• Page End: 543
• Publication Date: 2016-10-21
• Subjects: cellular MRI -- cell labelling -- iron oxide nanoparticle -- in vivo relaxometry -- fluorescent microscopy; Diagnostic imaging -- Periodicals; Magnetic resonance imaging -- Periodicals; Contrast media (Diagnostic imaging) -- Periodicals; Contrast Media -- Periodicals; Diagnostic Imaging -- Periodicals; Substances de contraste -- Périodiques; Diagnostics moléculaires -- Périodiques; Imagerie médicale; Substance de contraste; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); 616.0754
• DOI: 10.1002/cmmi.1715
• Languages: English
• ISSNs: 1555-4309

Abstract

Abstract : Cellular MRI, which visualizes magnetically labelled cells (cells*), is an active research field for in vivo cell therapy and tracking. The simultaneous relaxation rate measurements ( R 2 *, R 2, R 1 ) are the basis of a quantitative cellular MRI method proposed here. U937 cells were labelled with Molday ION Rhodamine B, a bi‐functional superparamagnetic and fluorescent nanoparticle (U937*). U937* viability and proliferation were not affected in vitro . In vitro relaxometry was performed in a cell concentration range of [2.5 × 10 4 –10 8 ] cells/mL. These measurements show the existence of complementary cell concentration intervals where these rates vary linearly. The juxtaposition of these intervals delineates a wide cell concentration range over which one of the relaxation rates in a voxel of an in vivo image can be converted into an absolute cell concentration. The linear regime was found at high concentrations for R 1 in the range of [10 6 – 2 × 10 8 ] cells/mL, at intermediate concentrations for R 2 in [2.5 × 10 5 – 5 × 10 7 ] cells/mL and at low concentrations for R 2 * in [8 × 10 4 – 5 × 10 6 ] cells/mL. In vivo relaxometry was performed in a longitudinal study, with labelled U937 cells injected into a U87 glioma mouse model. Using in vitro data, maps of in vivo U937* concentrations were obtained by converting one of the in vivo relaxation rates to cell concentration maps. MRI results were compared with the corresponding optical images of the same brains, showing the usefulness of our method to accurately follow therapeutic cell biodistribution in a longitudinal study. Results also demonstrate that the method quantifies a large range of magnetically labelled cells*. Copyright © 2016 John Wiley & Sons, Ltd. Abstract : A cellular MRI method that quantifies a large range of magnetically labelled cells is proposed. The method is based on the simultaneous measurements of R 2 *, R 2 and R 1 . Cellular relaxivities are defined in vitro and used to convert relaxation rates to cell concentration in vivo . The method was applied in a glioma model using U937 cells magnetically labelled with USPIO‐NPs.