Contrast Enhancement Characteristics of a Lipid Nanoemulsion Contrast Agent for Micro-Computed Tomography
Abstract
Purpose
To determine the time enhancement characteristics of a blood-pool novel lipid nanoemulsion computed tomography (CT) contrast agent by determining the time to peak contrast enhancement of the heart, liver, lungs, and spleen.
Methods
The novel blood-pool nanoemulsion CT contrast agent had a Lipiodol core, a 60:40 ratio of egg phospholipids to cholesterol shell, a concentration of iodine of 50 mg I/mL, and 260 nm diameter particles. In-vivo imaging was performed on 10-week-old female C57Bl/6 mice (n=6) which received 150 μL tail vein injections of the contrast agent. Images were acquired on an eXplore CT 120 (Trifoil Imaging, Chatsworth, CA, USA) micro-CT scanner with a 4 min continuous rotation protocol (70 kV, 50 mA, 15 cGy). Images were acquired 0 min, 15 min, 30 min, 45 min, 1 hr, 2 hr, 4 hr, 8 hr, and 1 d post injection. Hounsfield Units (HU) of organs were recorded for each timepoint and averaged across all mice.
Results
The time to max contrast enhancement of the heart, liver, lungs, and spleen were respectively 5.5 +/- 0.8 min, 105 +/- 44 min, 50 +/- 19 min, and 110 +/- 50 min. The average difference between peak enhanced and 1 d scan values for heart, liver, lungs, and spleen were 68 +/- 11 HU, 56 +/- 12 HU, 124 +/- 122 HU, and 331 +/- 184 HU. No complications related to the contrast agent were encountered.
Conclusion
The recommended imaging windows for peak contrast enhancement for this lipid shelled nanoemulsion for the heart, liver, lungs, and spleen, are respectively 4-5 min, 60-150 min, 30-70 min, and 60-160 min post injection. The contrast agent was found to clear the body by one day post injection with no noted complications.