Origin of the MRI Contrast in Natural and Hydrogel Formulation of Pineapple Juice.

Domenico Rizzo,Enrico Ravera,Marco Fragai,Claudio Luchinat,Giacomo Parigi,Domenico Osella

doi:10.1155/2021/6666018

Domenico Rizzo, Enrico Ravera + Show 4 more

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https://doi.org/10.1155/2021/6666018

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Abstract

Magnetic resonance imaging (MRI) often requires contrast agents to improve the visualization in some tissues and organs, including the gastrointestinal tract. In this latter case, instead of intravascular administration, oral agents can be used. Natural oral contrast agents, such as fruit juice, have the advantages of better taste, tolerability, and lower price with respect to the artificial agents. We have characterized the relaxometry profiles of pineapple juice in order to understand the origin of the increase in relaxation rates (and thus of the MRI contrast) in reference to its content of manganese ions. Furthermore, we have characterized the relaxometry profiles of pineapple juice in the presence of alginate in different amounts; the interaction of the manganese ions with alginate slows down their reorientation time to some extent, with a subsequent increase in the relaxation rates. The relaxometry profiles were also compared with those of manganese(II) solutions in 50 mmol/dm3 sodium acetate solution (same pH of pineapple juice), which revealed sizable differences, mostly in the number of water molecules coordinated to the metal ion, their lifetimes, and in the constant of the Fermi-contact interaction. Finally, the fit of the transverse relaxivity shows that the increased viscosity in the hydrogel formulations can improve significantly the negative contrast of pineapple juice at the magnetic fields relevant for clinical MRI.

Highlights

Fruit juice rich in manganese ions is increasingly used in clinical Magnetic resonance imaging (MRI) as oral contrast agent for imaging of the gastrointestinal tract [1]
Metal Content of Pineapple Juice. e amount of copper, iron, and manganese ions in pineapple juice was evaluated through ICP-AES. e resulting concentrations of the three ions were 0.002–0.007 mmol/dm3, 0.027–0.031 mmol/dm3, and 0.42–0.46 mmol/dm3, respectively. e ranges refer to the variability observed for four samples taken from different fruit juice batches. e concentration of Mn2+ is more than one order of magnitude larger than that of iron and copper so that the relaxation properties of the juice are largely dictated by the presence of this ion
Conclusions e acquired 1H NMRD profiles confirm that the relaxation rates measured for pineapple juice are mostly determined by the large relaxivity of the Mn2+ ions, as expected

Summary

Introduction

Fruit juice rich in manganese ions is increasingly used in clinical MRI as oral contrast agent for imaging of the gastrointestinal tract [1]. Magnetic resonance cholangiopancreatography images are frequently degraded by the high signal due to the fluid collecting in stomach and duodenum. Pineapple juice is the most promising natural food for higher content of Mn2+ ions [13, 14], providing image contrast of a degree similar to commercially available negative contrast agents [6]. As T2 agent, it was shown to suppress the signal from bowel fluid in pediatric magnetic resonance cholangiopancreatography, while as T1 agent, it can delineate the gut [13]

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