All animal experiments were conducted in accordance with the Northeastern University Division of Laboratory Animal Medicine and Institutional Animal Care and Use Committee The same quadrature 300 MHz, 30 mm Mouse MRI coil was used for all in vivo work (Animal Imaging Research, LLC, Holden, Massachusetts, USA). Healthy anesthetized Swiss Webster mice (n = 5) received a one-time intravenous bolus injection of 0.4–0.8 mg ferumoxytol for a starting blood pool concentration of 100–200 μg/mL (diluted to 4 mg/mL in phosphate-buffered saline) and were imaged longitudinally after injection (0, 2, and 4 h). Precontrast images were also acquired. Given the assumption that blood in mice is about 7% of body weight, for a 50-g mouse an initial yield of 115–230 μg/mL was predicted. This is similar to clinical concentrations where an injection of 510 mg produces a blood concentration of about 100 μg/mL for a total blood volume in the average adult human of 5 L.
A single UTE protocol was used for all images. To establish the UTE protocol, the following parameters were fixed: FOV = 3 × 3 × 3 cm3; matrix mesh size = 200 × 200 × 200; TE = 13 μs; TR = 4 ms; and θ = 20°. TR was slightly higher than the optimal value because of hardware and memory constraints. We analyzed a 50-mL cylindrical phantom filled with 5 mM CuSO4 to determine the k-trajectories for image reconstruction.
A single UTE protocol was used for all images. To establish the UTE protocol, the following parameters were fixed: FOV = 3 × 3 × 3 cm3; matrix mesh size = 200 × 200 × 200; TE = 13 μs; TR = 4 ms; and θ = 20°. TR was slightly higher than the optimal value because of hardware and memory constraints. We analyzed a 50-mL cylindrical phantom filled with 5 mM CuSO4 to determine the k-trajectories for image reconstruction.
