In vitro relaxation measurements of potential oral contrast materials for small bowel MRI

Purpose: The purpose of the study was to measure and compare T1 and T2 relaxation times of different potential oral contrast agents for MR examination of the gastrointestinal tract.

Methods and Materials: The T1 and T2 values of fruit juices, cocoa, iron-desferrioxamine solution, polyethylene glycol and a commonly used Gd-based contrast material with different concentrations were determined by means of MRI methods at a clinical MR scanner operating at 1.0 Tesla. T1 maps were obtained with an inversion prepared spoiled gradient echo sequence. T2 maps were determined using the CPMG sequence. Percentage concentrations were used for fruit juices because the metal contents were not known.

Results: The results were analyzed and reported in tables and figures. In most cases the 1/T1 and 1/T2 relaxation rates increased linearly with the concentration but for the rosehip syrup the dependence was not linear. For the highest concentration, the iron-desferrioxamine solution and the rosehip syrup had shorter T1 time than the Gd-based contrast agent. T1 of cocoa was moderate. T2 values were very low for rosehip, cocoa and iron-desferrioxamine solution and were high for polyethylene glycol.

Conclusion: Probably there are solute-solute interactions in the rosehip syrup which make the dependence of 1/T1 and 1/T2 on the concentration non-linearly. The materials with short T1 values are potential positive contrast agents on T1 as it relates to signal intensity. Cocoa could behave like a negative contrast agent. Polyethylene glycol, being negative on T1 and positive on T2 could be used as a biphasic oral contrast agent for the small bowel MRI.