Abstract #2659

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

Sonal Josan^1,2, Amanda Hamilton³, Michael Benoit³, Charles Cunningham⁴, Daniel Spielman², A. C. Matin³, Dirk Mayer^1,2

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.