Stefan Marco Herz MD, Presenter: Nothing to Disclose

Patrick Vogel, Abstract Co-Author: Nothing to Disclose

Martin A. Ruckert, Abstract Co-Author: Nothing to Disclose

Christian Brede, Abstract Co-Author: Nothing to Disclose

Thomas Kampf, Abstract Co-Author: Nothing to Disclose

Simon Veldhoen MD, Abstract Co-Author: Nothing to Disclose

Peter Michael Jakob PhD, Abstract Co-Author: Nothing to Disclose

Andreas Beilhack, Abstract Co-Author: Nothing to Disclose

Volker C. Behr, Abstract Co-Author: Nothing to Disclose

Thorsten Alexander Bley MD, Abstract Co-Author: Nothing to Disclose

Here we investigated the feasibility of fusing 3D magnetic particle imaging (MPI) and magnetic resonance imaging (MRI) to visualize dynamic immune cell processes in a murine graft-versus-host disease (GVHD) model. MPI, a novel imaging tool, was used to detect monoclonal antibodies conjugated to superparamagnetic iron oxide particles to track T cell populations.

Acute GVHD was induced in myeloablativly (9 Gy) conditioned BALB/c mice (H-2d, CD90.2) by transplanting allogeneic luciferase (luc+) CD90.1+ T cells from transgenic C57BL/6.L2G85 mice together with T cell depleted bone marrow cells from C57BL/6 wild type mice. Controls only received T cell depleted bone marrow. 3 days after transplantation in vivo bioluminescence imaging (BLI) was performed before i.v. administration of a donor T cell specific CD90.1 monoclonal antibody conjugated to superparamagnetic iron oxide nanoparticles. 3h and 6h later MPI and MRI was performed using the same holder to ensure identical positioning of mice for both modalities. 3D MPI was conducted with a homemade traveling wave MPI scanner (gradient: 4T/m, bore: 29 mm). MRI was performed with a 7T scanner with a 60 mm horizontal bore. A 3D T2-weighted rapid acquisition with refocused echoes (RARE) sequence was used to provide anatomical background. MPI and MRI data were reconstructed and fused manually.

MPI proofed sensitive to visualize donor T cells after hematopoietic cell transplantation. In vivo BLI as reference standard revealed high signals in the cervical, mesenteric and splenic region indicating the presence of alloreactive T cells in mice within secondary lymphoid organs during GVHD initiation. In MPI/MRI fusion images high MPI-signal in the spleen was observed. In contrast, bone marrow controls displayed only baseline signals.

These initial results demonstrate that 3D MPI/MRI fusion imaging with labeled antibodies is a feasible tool to assess dynamic immune cell processes such as acute GVHD. Further technical improvements are necessary to transfer this technique from preclinical animal models to human imaging.

3D fusion of magnetic particle imaging and whole-body MRI is a promising biotechnical approach with the potential to provide radiation-free molecular imaging in humans.

Herz, S, Vogel, P, Ruckert, M, Brede, C, Kampf, T, Veldhoen, S, Jakob, P, Beilhack, A, Behr, V, Bley, T, Visualizing Immune Processes with 3D Magnetic Particle / Magnetic Resonance Fusion Imaging: Proof of Concept in a Murine Graft-versus-Host Disease Model.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012662.html