Basic Study
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Radiol. Jun 28, 2016; 8(6): 588-593
Published online Jun 28, 2016. doi: 10.4329/wjr.v8.i6.588
Effects of iodinated contrast on various magnetic resonance imaging sequences and field strength: Implications for characterization of hemorrhagic transformation in acute stroke therapy
Humberto Morales, Lisa Lemen, Ranasinghage Samaratunga, Peter Nguyen, Thomas Tomsick
Humberto Morales, Lisa Lemen, Ranasinghage Samaratunga, Peter Nguyen, Thomas Tomsick, Department of Radiology, University of Cincinnati Medical Center, Cincinnati, OH 45267-0761, United States
Author contributions: Morales H performed the experiment, analyzed the data and wrote the paper; Lemen L and Samaratunga R contributed to the performance of the experiment in the MR scanner and edited the paper; Nguyen P contributed to analyze the data and edited the paper; Tomsick T designed the study and wrote the paper.
Supported by The 2008 Neuroradiology Education and Research Fund of the American Society of Neuroradiology partially via the Boston Scientific Fellowship in Cerebrovascular Disease Research Award to Humberto Morales MD, Principal Investigator.
Institutional review board statement: This basic study involved only in vitro results of iodinated contrast materials. There was no involvement of data/information related to patients/animals or actual patients or animals. Institutional Guidelines for MR Safety were followed strictly.
Conflict-of-interest statement: Humberto Morales, MD, who managed the money paid to the institution to buy supplies, did not receive any salary support from the related ASNR grant. All other authors declare no source of funding or conflict of interest pertinent to this submitted manuscript.
Data sharing statement: Dataset available from the corresponding author at: moralehc@ucmail.uc.edu.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Humberto Morales, MD, Assistant Professor of Radiology Section of Neuroradiology, Department of Radiology, University of Cincinnati Medical Center, 234 Goodman Street, Cincinnati, OH 45267-0761, United States. moralehc@ucmail.uc.edu
Telephone: +1-513-5841584 Fax: +1-513-5849100
Received: July 30, 2015
Peer-review started: August 4, 2015
First decision: September 28, 2015
Revised: March 2, 2016
Accepted: March 17, 2016
Article in press: March 18, 2016
Published online: June 28, 2016
Processing time: 324 Days and 14.9 Hours
Abstract

AIM: To characterize the effects of iodinated contrast material (ICM) on magnetic resonance imaging (MRI) comparing different sequences and magnetic fields, with emphasis to similarities/differences with well-known signal characteristics of hemorrhage in the brain.

METHODS: Aliquots of iopamidol and iodixanol mixed with normal saline were scanned at 1.5T and 3T. Signal intensity (SI) was measured using similar spin-echo (SE)-T1, SE-T2, gradient-echo (GRE) and fluid-attenuation-inversion-recovery (FLAIR) sequences at both magnets. Contrast to noise ratio (CNR) (SI contrast-SI saline/SD noise) for each aliquot were calculated and Kruskall-wallis test and graphic analysis was used to compare different pulse sequences and ICMs.

RESULTS: Both ICM showed increased SI on SE-T1 and decreased SI on SE-T2, GRE and FLAIR at both 1.5T and 3T, as the concentration was increased. By CNR measurements, SE-T2 had the greatest conspicuity at 3T with undiluted iopamidol (92.6 ± 0.3, P < 0.00) followed by iodixanol (77.5 ± 0.9, P < 0.00) as compared with other sequences (CNR range: 15-40). While SE-T2 had greatest conspicuity at 1.5T with iopamidol (49.3 ± 1, P < 0.01), SE-T1 showed similar or slightly better conspicuity (20.8 ± 4) than SE-T2 with iodixanol (23 ± 1.7). In all cases, hypo-intensity on GRE was less conspicuous than on SE-T2.

CONCLUSION: Iodixanol and iopamidol shorten T1 and T2 relaxation times at both 1.5T and 3T. Hypo-intensity due to shortened T2 relaxation time is significantly more conspicuous than signal changes on T1-WI, FLAIR or GRE. Variations in signal conspicuity according to pulse sequence and to type of ICM are exaggerated at 3T. We postulate T2 hypointensity with less GRE conspicuity differentiates ICM from hemorrhage; given the well-known GRE hypointensity of hemorrhage. Described signal changes may be relevant in the setting of recent intra-arterial or intravenous ICM administration in translational research and/or human stroke therapy.

Keywords: Iodinated contrast; Magnetic resonance imaging; Gradient-echo; Hemorrhage; Stroke

Core tip: After recent groundbreaking stroke clinical trials have shown positive outcomes with endovascular therapy, the use of imaging, particularly magnetic resonance imaging (MRI) is expected to increase in this setting. Iodinated contrast material (ICM) is inherent to this scenario and can be deposited in the brain after intra-arterial or intra-venous injection. Differentiation of ICM from hemorrhagic changes is of upmost clinical importance. This paper demonstrates the signal characteristics of in vitro ICM with routine MR sequences [including not previously reported changes on gradient-echo (GRE)]. Changes at high magnetic field (3T) are to the best of our knowledge described for the first time, with T2 hypo intensity as the signal change with greatest conspicuity as compared with other routine brain sequences. Furthermore, no significant conspicuity/hypo intensity on GRE is demonstrate and postulated as a way to differentiate contrast deposition (T2 hypo intensity or T1 hyper intensity) from hemorrhagic changes.