Clinical 3t mr scanner

MRI phantoms were made of SPION-PEG-PCL micelles (10 ml) with iron concentrations of 0.1, 0.3, 0.5 and 1 mM. Phantoms were prepared by mixing the micelle suspension with agarose (Sigma-Aldrich Chemical Co., Munich, Germany) aqueous solution (3%) which was heated and then cooled down in falcon tubes overnight to form a gel. The phantoms were placed in the extremity coil of a clinical 3T MR scanner (Siemens, Erlangen, Germany) at room temperature and a gradient echo T₂* sequence was applied. The repetition time was 2000 ms and six stepwise increasing echo times (TEs) of 2–17.2 ms was used to obtain the T₂*-weighted images of the phantoms. Regions of interest (ROI) were manually placed on the images. The relaxation time, T₂*, was then calculated as the slope of a semi-log plot of the signal intensity in the ROI versus the TEs. The relaxivity R₂* was calculated as 1/T₂*. All R₂* values for the phantoms were subtracted by R₂* value for the control sample (plain agarose gel). A standard curve was plotted with R₂* (s⁻¹, y-axis) versus iron concentration (mM, x-axis).

The in
vivo MRI of mice was tested using a clinical 3 T MR scanner
(Siemens). On day 15 after the establishment of the xenograft model,
mice were subjected to anesthesia through intraperitoneal injection
of pentobarbital sodium (60 mg/kg). Then the mice were administered
100 μL of PBS, ESIONPs (15.5 μg dispersed in 100 μL
of PBS), EXO (200 μg dispersed in 100 μL of PBS), and
ESIONPs@EXO (200 μg dispersed in 100 μL of PBS) through
the tail vein. The amount of ESIONPs was equal to that of ESIONPs@EXO
normalized to the content of Fe. Following a 1 h interval, the mice
were immobilized at the center of the MRI scanner coil, and MR imaging
was conducted utilizing the following imaging sequence: TE = 33.14
ms, TR = 2000 ms, FOV = 40 × 40 cm², matrix = 384
× 384, slice thickness = 3.0 mm.