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Improved stem cell MR detectability in animal models by modification of the inhalation gas
Uwe Himmelreich1, Ralph Weber, Pedro Ramos-Cabrer
1Max-Planck-Institute for Neurological Research, Cologne, Germany.
Abstract:
In vivo monitoring of cells labeled with paramagnetic iron oxide particles by magnetic resonance imaging (MRI) is complicated by intrinsic contrast of blood vessels. Distinction between T2* effects caused by blood vessels from those caused by labeled cells was so far only possible after carefully following the location of hypointense regions through subsequent slices of T2*-weighted 3-D MRI datasets, a procedure that is time consuming and not always reliable in the case of smaller blood vessels. Here, we demonstrate that the modification of the inhalation gas mixture from the routinely used composition 35% O2 and 65% N2O to a mixture containing 95% O2 and 5% CO2 results in a contrast suppression of most small blood vessels and reduces the intrinsic T2* effect of large vessels dramatically in an animal model. This change in protocol of physiological conditions was well tolerated by all studied animals, even over prolonged experimental times. The changed inhalation gas mixture thus provides a more reliable identification method for small clusters of iron oxide labeled cells in vivo.
Insights
Modifying the inhalation gas mixture for in vivo magnetic resonance imaging (MRI) significantly improves the detection of iron oxide-labeled cells by suppressing blood vessel contrast. This new method enhances cell tracking reliability in animal models.
Area of Science:
- Biomedical Imaging
- Cellular Biology
- Medical Physics
Background:
- In vivo cell tracking using iron oxide nanoparticles and MRI is challenged by intrinsic blood vessel contrast.
- Differentiating T2* effects from blood vessels versus labeled cells requires time-consuming analysis of MRI datasets.
- Existing methods struggle with reliable identification of smaller blood vessels and cell clusters.
Purpose of the Study:
- To develop a more reliable method for in vivo identification of iron oxide-labeled cells using MRI.
- To overcome the limitations posed by intrinsic blood vessel contrast in T2*-weighted imaging.
- To improve the accuracy of cell tracking in animal models.
Main Methods:
- Utilized T2*-weighted 3-D MRI datasets in an animal model.
- Modified the standard inhalation gas mixture (35% O2, 65% N2O) to a novel mixture (95% O2, 5% CO2).
- Assessed the impact of the gas mixture change on blood vessel contrast and T2* effects.
Main Results:
- The modified gas mixture (95% O2, 5% CO2) dramatically reduced intrinsic T2* effects from both large and small blood vessels.
- Contrast suppression of most small blood vessels was observed.
- The new protocol was well-tolerated by animals, even during prolonged experiments.
Conclusions:
- Altering the inhalation gas mixture provides a more reliable method for identifying in vivo iron oxide-labeled cells.
- This technique simplifies the distinction between labeled cells and background vasculature.
- The findings offer a significant advancement for in vivo cell monitoring and tracking applications.
