Near-wall hemodynamic parameters quantification in in vitro intracranial aneurysms with 7 T PC-MRI

OBJECTIVE

Wall shear stress (WSS) and its derived spatiotemporal parameters have proven to play a major role on intracranial aneurysms (IAs) growth and rupture. This study aims to demonstrate how ultra-high field (UHF) 7 T phase contrast magnetic resonance imaging (PC-MRI) coupled with advanced image acceleration techniques allows a highly resolved visualization of near-wall hemodynamic parameters patterns in in vitro IAs, paving the way for more robust risk assessment of their growth and rupture.

MATERIALS AND METHODS

We performed pulsatile flow measurements inside three in vitro models of patient-specific IAs using 7 T PC-MRI. To this end, we built an MRI-compatible test bench, which faithfully reproduced a typical physiological intracranial flow rate in the models.

RESULTS

The ultra-high field 7 T images revealed WSS patterns with high spatiotemporal resolution. Interestingly, the high oscillatory shear index values were found in the core of low WSS vortical structures and in flow stream intersecting regions. In contrast, maxima of WSS occurred around the impinging jet sites.

CONCLUSIONS

We showed that the elevated signal-to-noise ratio arising from 7 T PC-MRI enabled to resolve high and low WSS patterns with a high degree of detail.

Human mesenchymal stem cells home specifically to radiation-injured tissues in a non-obese diabetes/severe combined immunodeficiency mouse model

The therapeutic potential of bone marrow-derived human mesenchymal stem cells (hMSC) has recently been brought into the spotlights of many fields of research. One possible application of the approach is the repair of tissue injuries related to side effects of radiotherapy. The first challenge in cell therapy is to assess the quality of the cell and the ability to retain their differentiation potential during the expansion process. Efficient delivery to the sites of intended action is also necessary. We addressed both challenges using hMSC cultured and then infused to non-obese diabetes/severe combined immunodeficiency (NOD/SCID) mice submitted to total body irradiation. Furthermore, we tested the impact of additional abdominal irradiation superimposed to total body irradiation (TBI), as a model of local therapeutic irradiation. Our results showed that the hMSC used for transplant have been expanded without significant loss in their differentiation capacities. After transplantation into adult unconditioned mice, hMSC not only migrate in bone marrow but also into other tissues. Total body irradiation increased hMSC implantation in bone marrow and muscle and further led to engraftment in brain, heart and liver. Local irradiation in addition to TBI, increased homing of injected cells to the injured tissues and to other tissues outside the local irradiation field. Morphological recovery of irradiated tissues after MSC transplantation and/or differentiation of MSC into specific organ cell types needs to be investigated. This study suggests that using the potential of hMSC to home to various organs in response to tissue injuries might be a strategy to repair the radiation-induced damages.