Overcoming the Low Relaxivity of Gadofosveset at High Field with Spin Locking

Owen C. Richardson¹, Marietta Scott², Steven F. Tanner¹, John C. Waterton², David L. Buckley¹

Gadofosveset binds reversibly to serum albumin (SA), and has a high longitudinal relaxivity at lower magnetic fields ( 3.0 T) but a much lower relaxivity at high fields. Spin locking (SL) is sensitive to macromolecular content; it is hypothesised that combining SL with albumin binding may enable increased gadofosveset relaxivity at high fields. In Vitro measurements at 4.7 T found significantly higher SL relaxation rates, R1 (1/T1), when gadofosveset was SA-bound than when unbound. R1 values for a non-binding contrast agent (gadopentetate) in SA were similar to unbound gadofosveset. SL at high field generates significantly higher relaxation rates for gadofosveset than conventional agents, and may enable differentiation of free and bound molecules at these field strengths.