Related Experiment Video
Updated: Aug 22, 2026
In vivo Imaging of Optic Nerve Fiber Integrity by Contrast-Enhanced MRI in Mice
Published on: July 22, 2014
Intracellular manganese ions provide strong T1 relaxation in rat myocardium
Wibeke Nordhøy1, Henrik W Anthonsen, Morten Bruvold
1Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim.
Abstract:
The efficacy of manganese ions (Mn2+) as intracellular (ic) contrast agents was assessed in rat myocardium. T1 and T2 and Mn content were measured in ventricular tissue excised from isolated perfused hearts in which a 5-min wash-in with 0, 30, 100, 300, or 1000 microM of Mn dipyridoxyl diphosphate (MnDPDP) was followed by a 15-min wash-out to remove extracellular (ec) Mn2+. An inversion recovery (IR) analysis at 20 MHz revealed two T1 components: an ic and short T1-1 (650-251 ms), and an ec and longer T1-2 (2712-1042 ms). Intensities were about 68% and 32%, respectively. Tissue Mn content correlated particularly well with ic R1-1. A two-site water-exchange analysis of T1 data documented slow water exchange with ic and ec lifetimes of 11.3 s and 7.5 s, respectively, and no differences between apparent and intrinsic relaxation parameters. Ic relaxivity induced by Mn2+ ions in ic water was as high as 56 (s mM)(-1), about 8 times and 36 times higher than with Mn2+ aqua ions and MnDPDP, respectively, in vitro. This value is as high as any reported to date for any synthetic protein-bound metal chelate. The increased rotational correlation time (tauR) between proton and electron (Mn2+) spins, and maintained inner-sphere water access, might make ic Mn2+ ions and Mn2+ -ion-releasing contrast media surprisingly effective for T1-weighted imaging.
Insights
Manganese ions (Mn2+) show high efficacy as intracellular contrast agents in rat hearts. Their high relaxivity suggests potential for effective T1-weighted MRI imaging.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Biomedical Engineering
- Medical Imaging
Background:
- Manganese ions (Mn2+) are being explored as intracellular contrast agents for MRI.
- Understanding the behavior and efficacy of Mn2+ within cells is crucial for developing novel imaging techniques.
Purpose of the Study:
- To assess the efficacy of manganese ions (Mn2+) as intracellular contrast agents in rat myocardium.
- To quantify the relationship between tissue manganese content and MRI relaxation parameters.
Main Methods:
- Isolated perfused rat hearts were exposed to varying concentrations of Mn dipyridoxyl diphosphate (MnDPDP).
- Tissue Mn content, T1, and T2 relaxation times were measured using inversion recovery (IR) analysis.
- A two-site water-exchange model was used to analyze T1 data.
Main Results:
- Two distinct T1 components were identified: intracellular (short T1-1) and extracellular (longer T1-2).
- Intracellular Mn content strongly correlated with the T1 relaxation rate (R1-1).
- Intracellular Mn2+ exhibited exceptionally high relaxivity (56 (s mM)(-1)), significantly exceeding extracellular or in vitro values.
Conclusions:
- Intracellular Mn2+ ions demonstrate high relaxivity, comparable to protein-bound metal chelates.
- The findings suggest that intracellular Mn2+ and Mn2+-releasing agents hold significant promise for T1-weighted MRI.
- Optimized delivery and retention of Mn2+ could lead to superior contrast enhancement in MRI applications.
