Abstract
ObjectivesTo develop a nanoparticle-based MRI protocol based on transrectal administration of intestine-absorbable nanoparticle contrast agents to evaluate ulcerative colitis (UC).MethodsSolid lipid nanoparticles (SLNs) were synthesized by loading gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) and octadecylamine-fluorescein isothiocyanate to produce Gd-FITC-SLNs as T1 contrast agents. Twenty mice with acute UC were divided into four groups: enema with Gd-FITC-SLNs, intravenous injection of Gd-FITC-SLNs, enema with Gd-DTPA, and intravenous injection of Gd-DTPA. Five mice with chronic UC and five mice without UC underwent enema with Gd-FITC-SLNs. Axial T1- and T2-weighted MR images were obtained before and 20, 40, 60, 80,100, and 120 min after enema or intravenous injection of the contrast agent. The signal-to-noise ratios (SNRs) of the colorectal wall were measured in both groups. The MRI findings were correlated with subsequent histological confirmation.ResultsAt 20 min after enema with Gd-FITC-SLNs, MRI showed the following contrast enhancement pattern: acute UC > normal intestinal wall > chronic UC. A continuous enhancement effect was observed in mice with acute UC, whereas a slight continuous enhancement of the colorectal wall was observed in mice with chronic UC. The normal intestinal wall rapidly metabolized the contrast agent, and the enhancement decreased on sequential scans. There was no significant difference between the SNRs of the intestinal wall at 20 min after intravenous Gd-DTPA and transrectal Gd-FITC-SLN administration.ConclusionsEnema with Gd-FITC-SLNs may be helpful for the diagnosis and differential diagnosis of acute and chronic UC and can confer the same or better results than with intravenous Gd-DTPA.Key Points• Enema with Gd-FITC-SLNs may be helpful for the diagnosis and differential diagnosis of acute and chronic UC.• Enema with Gd-FITC-SLNs can achieve the same or better result than that with intravenous Gd-DTPA.• SLN-based MR colonography enhances the colorectal wall inflammation, based on the colonic absorption of the nanoparticle contrast agents.
Highlights
ulcerative colitis (UC) is a type of recurrent non-specific inflammation
The colorectal wall in the acute UC group was continuously enhanced for 120 min, the normal intestinal wall showed rapid metabolization of the contrast agent, and the degree of enhancement decreased with time, while in the chronic UC group, the colorectal wall only showed slight enhancement
After 20 min of enema with GdFITC-SLNs, the rectal wall enhancement of mice with acute UC was similar to those administered with intravenous gadolinium diethylenetriaminepentaacetic acid (GdDTPA), but the enhancement time was longer with enema than with intravenous injection (Figs. 4 and 5)
Summary
UC is a type of recurrent non-specific inflammation. Recently, its incidence has been increasing annually [1]. Medical researchers have continually explored ways of facilitating early diagnoses of UC [4]
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