Introduction Numerous perfusion imaging techniques have been developed based on nuclear medicine, MRI, CT, and ultrasound.1 A key enabler of perfusion imaging is the high contrast inherent to nuclear medicine, which sees only a tracer and does not see tissue. Magnetic Particle Imaging (MPI) is an emerging molecular imaging modality that, like nuclear medicine, sees only a tracer and does not see tissue.2–5 Because of MPI’s high contrast, high sensitivity, and signal linearity independent of depth, we believe MPI will excel at perfusion imaging.
As we push MPI towards quantitative perfusion imaging (blood volume, blood flow, mean transit time), we must first demonstrate high contrast imaging of the blood volume. Continued technical development to reduce scan times will enable quantitative measurement of blood flow and mean transit time. Here we demonstrate the first step, blood volume imaging, in vivo in rats with a tailored MPI-specific nanoparticle tracer.
Methods 1mg LodeSpin SPIOs were injected into the tail vein of anesthetized Fischer 344 rats and imaged in a home-built MPI scanner with respiratory gating or imaged following sacrifice. Images were reconstructed using x-space reconstruction and equalized or deconvolved. All experiments were conducted under an approved animal protocol.
Results Preliminary results for MPI blood pool imaging are shown in Figure 1. In Figure 1A, we see an MPI image of the thorax image of a live animal. In Figure 1B, we see the brain of the same animal following sacrifice two hours after injection. Figure 1C, we see brain vasculature, the jugular veins, the outline of the heart wall, and the lungs in an animal sacrificed immediately following injection. In Figure 1E we see the lungs, the liver, and the kidneys of the same animal.
Conclusion MPI shows great promise as a sensitive, high-contrast, and radiation-free technique for measuring brain perfusion, brain vasculature, and organ perfusion.
Acknowledgments The authors acknowledge support from the following research grants: NIH 5R01EB013689–03, CIRM RT2–01893, Keck Foundation 034317, NIH 1R24MH106053–01, NIH 1R01EB019458–01, ACTG 037829, and NIH 2R42EB013520–02A1.
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Disclosures P. Goodwill: 4; C; Magnetic Insight, Inc. 5; C; Magnetic Insight, Inc. M. Ferguson: 4; C; LodeSpin Labs. E. Yu: None. B. Zheng: None. K. Lu: None. A. Khandhar: 4; C; LodeSpin Labs. S. Kemp: 4; C; LodeSpin Labs. K. Krishnan: 4; C; LodeSpin Labs. S. Conolly: 4; C; Magnetic Insight, Inc.
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