ELECTRONIC POSTER - ismrm

14:00 4936. Combined Off-Resonance Imaging and Relaxation in the Rotating Frame for
Positive Contrast Imaging of Infection in a Murine Burn Model
Valeria Righi 1,2 , Dionyssios Mintzopoulos 1,2 , Ovidiu C. Andronesi 1,2 , Jianxin He 3 , George
Dai 2 , Laurence G. Rahme 3 , A Aria Tzika 1,2
1 NMR Surgical Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns
Institute, Harvard Medical School, Boston, MA, United States; 2 Department of Radiology, Massachusetts
General Hospital, Harvard Medical School, Athinoula A. Martinos Center for Biomedical Imaging, Boston,
MA, United States; 3 Molecular Surgery Laboratory, Department of Surgery, Massachusetts General Hospital
and Shriners Burns Institute, Harvard Medical School, Boston, MA, United States
We employed positive-contrast MRI in a murine model of burn and infection. We used off-resonance imaging (ORI) and a novel
method of combining off-resonance imaging and relaxation in the rotating frame (ORI-T2ρ). We imaged accumulation of ultra-small
super-paramagnetic iron oxide (USPIO) nanoparticle-labeled macrophages at the infection site in mice, which were burned and
infected with Pseudomona aeruginosa. We concluded that ORI-T2ρ is more sensitive than ORI in detecting USPIOs and that we can
successfully detect infection with positive contrast imaging, which opens up perspectives for monitoring infection and testing antiinfectives.
14:30 4937. Quantification of Bound Contrast Agent Concentration Using Delta Relaxation
Enhanced MR
Jamu K. Alford 1 , Blaine A. Chronik 1
1 Physics and Astronomy, The University of Western Ontario, London, ON, Canada
Delta relaxation enhanced magnetic resonance (dreMR) is an emerging method for performing molecular imaging, which utilizes a
removable electromagnetic coil to modify the strength of the main magnetic field during an MRI pulse sequence. The purpose of this
field-cycling method is to acquire information about the binding state of targeted contrast agents that is not obtainable with static-field
MRI methods. This work describes a method for advancing dreMR from qualitative imaging to quantitative measurement of contrast
agent binding. By measuring the concentration of bound agent, the corresponding concentration of the target molecule can
determined.
15:00 4938. Rigidity of the Microscopic Environment Surrounding the Binding Site of Magnetic
Nanoparticles
John B. Weaver 1 , Adam M. Rauwerdink 2
1 Radiology, Dartmouth-Hitchcock Medical Center, Lebanon, NH, United States; 2 Thayer School of
Engineering, Dartmouth College, Hanover, NH, United States
The microscopic stiffness of cellular cytoskeleton and the extracellular matrix have been very important in understanding metastasis
and angiogenesis but no methods capable of in vivo measurement exist. We show that a new method related to magnetic particle
imaging (MPI) called magnetic spectroscopy of nanoparticle Brownian motion (MSB) is sensitive to the stiffness of the microscopic
environment surrounding the binding sites of the streptavidin functionalized nanoparticles. The matrix consisted of gels made with
mixtures of gelatin and biotinated BSA. Gel stiffness was changed by varying the concentration of gelatin. MSB showed significant
differences between each of the gels.
Thursday 13:30-15:30 Computer 115
13:30 4939. Unambiguous Localization of Contrast Agents Via B 0 -Field-Cycling
Uvo Christoph Hoelscher 1 , Steffen Lother 1 , Florian Fidler 1 , Matin Blaimer 1 , Peter
Jakob 1,2
1 Research Center Magnetic Resonance Bavaria (MRB), Wuerzburg, Germany; 2 Department for Experimental
Physics 5, University of Wuerzburg, Wuerzburg, Germany
This work presents a setup and analysis algorithm for unambiguous localization of contrast agents via a cycled magnetic field inside a
clinical scanner. The algorithm detects contrasts agents with high relaxivity dispersion and suppresses signal from pure tissue. Data for
the contrast agent Vasovist is shown and compared to theoretical results.
14:00 4940. Contrast Agents: the Effect of Relaxation on Magnetic Particle Imaging
Yong Wu 1 , Zhen Yao 1 , Gareth Kafka 1 , David Farrell 1 , Mark Griswold 2 , Robert Brown 1
1 Department of Physics, Case Western Reserve University, Cleveland, OH, United States; 2 Department of
Radiology, Case Western Reserve University, Cleveland, OH, United States
Magnetic particle imaging (MPI) is a new tomographic technique that allows fast, inexpensive imaging of MRI contrast ferrofluid
agents with submillimeter resolution. Selection fields combined with oscillating driving fields can move unsaturated field-free-points
so as to cover the field of view. In previous studies, the average magnetization is assumed to respond instantaneously to changes in
the applied field. Realistically, however, a finite relaxation time slows the magnetic response. The present simulation demonstrates
that, for contrast agents of interest, the choice of an optimal particle size is strongly dependent on this effect. A trade-off thus exists
between sensitivity and resolution.
14:30 4941 A Fast Optimization Algorithm for Multi-Dimensional RF-Pulse Design under Multiple
Constraints
A. Sbrizzi 1 , H. Hoogduin 2 , P. Luijten2, J. J. Lagendijk 2 , G. Sleijpen 3 , and C. A. van den Berg 4