Fig. 7.

In vivo ${}^{29}\mathrm{Si}$ MRI for $2\mu \mathrm{m}$ silicon particles. (a) Administration of $\sim 135\mathrm{mg}$ of PEGylated silicon particles (in $300\mu \mathrm{l}$ PBS) into a normal mouse via oral gavage, followed by a 5-min wait prior to imaging. (b) Administration of $\sim 135\mathrm{mg}$ of PEGylated silicon particles (in 1 ml PBS) via injection through the rectum of a normal mouse using a soft plastic gavage needle (3.8 mm diameter), followed by a 5-min wait prior to imaging. (c) Administration of $\sim 100\mathrm{mg}$ of PEGylated silicon particles (in $300\mu \mathrm{l}$ PBS) via intraperitoneal injection into a normal mouse, followed by a 30-min wait prior to imaging; gravitational settling is noted at the injection site. (d) Administration of $\sim 135\mathrm{mg}$ of ESTA-1 functionalized silicon particles (in $600\mu \mathrm{l}$ PBS) into a SKOV3 mouse via intraperitoneal injection, followed by physical manipulation of the mouse’s abdomen to help distribute the particles, then a 10-min wait prior to imaging. ${}^{29}\mathrm{Si}$ imaging scans (color): 90 deg RARE imaging sequence, TR/TE: $59.9/1.8\mathrm{ms}$, FOV: $64\times 64\mathrm{mm}$, resolution: 2 mm; single scan acquisition ($\text{scan time}\sim 60\mathrm{ms}$), processed with 35% threshold to filter background. Coregistered with ${}^1\mathrm{H}$ imaging scans (grayscale): 90 deg RARE imaging sequence, coronal plane, TR/TE: $1800/9.5\mathrm{ms}$, FOV: $64\times 64\mathrm{mm}$; resolution: 0.25 mm; three averages ($\text{scan time}\sim 3\min$).