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Abstract #2659

Comparison of Susceptibility Gradient Mapping & Off-Resonance Excitation for Quantitative Positive Contrast MRI of Magnetotactic Bacteria

Sonal Josan1,2, Amanda Hamilton3, Michael Benoit3, Charles Cunningham4, Daniel Spielman2, A. C. Matin3, Dirk Mayer1,2

1SRI International, Menlo Park, CA, United States; 2Radiology, Stanford University, Stanford, CA, United States; 3Microbiology & Immunology, Stanford University, Stanford, CA, United States; 4Sunnybrook Health Sciences Center, Toronto, ON, Canada

This work compares two positive contrast imaging techniques for quantitative detection of endogenous magnetite particles generaated by magnetotactic bacteria: off-resonance excitation and susceptibility gradient mapping (SGM). Off-resonance excitation uses spectral-spatial pulses to excite and refocus the off-resonant water protons near the magnetite particles while the SGM method involves post-processing of conventional 3D gradient echo images to calculate susceptibility gradients induced by the particles. Both techniques visualize the magnetite spots and provide good background suppression. Both methods demonstrated a linear correlation, but with different slopes, between iron concentration and the integrated signal intensity of positive contrast voxels at the spot location.