scholarly journals Sensitivity and resolution improvement for in vivo magnetic resonance current‐density imaging of the human brain

2021 ◽  
Author(s):  
Cihan Göksu ◽  
Klaus Scheffler ◽  
Fróði Gregersen ◽  
Hasan H. Eroğlu ◽  
Rahel Heule ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Human Brain ◽  
Current Density ◽  
Resolution Improvement ◽  
Current Density Imaging ◽  
Resonance Current

scholarly journals Sensitivity and resolution improvement for in-vivo magnetic resonance current density imaging (MRCDI) of the human brain

2021 ◽  
Author(s):  
Cihan Goksu ◽  
Klaus Scheffler ◽  
Frodi Gregersen ◽  
Hasan H Eroglu ◽  
Rahel Heule ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Human Brain ◽  
Current Density ◽  
Current Flow ◽  
Transcranial Electrical Stimulation ◽  
Physiological Noise ◽  
Flow Simulations ◽  
Current Density Imaging ◽  
Resonance Current

Purpose: Magnetic resonance current density imaging (MRCDI) combines MR brain imaging with the injection of time-varying weak currents (1-2 mA) to assess the current flow pattern in the brain. However, the utility of MRCDI is still hampered by low measurement sensitivity and poor image quality. Methods: We recently introduced a multi-gradient-echo-based MRCDI approach that has the hitherto best documented efficiency. We now advanced our MRCDI approach in three directions and performed phantom and in-vivo human brain experiments for validation: First, we verified the importance of enhanced spoiling and optimize it for imaging of the human brain. Second, we improved the sensitivity and spatial resolution by using acquisition weighting. Third, we added navigators as a quality control measure for tracking physiological noise. Combining these advancements, we tested our optimized MRCDI method by using 1 mA transcranial electrical stimulation (TES) currents injected via two different electrode montages in five subjects. Results: For a session duration of 4:20 min, the new MRCDI method was able to detect magnetic field changes caused by the TES current flow at a sensitivity level of 84 pT, representing in a twofold increase relative to our original method. Comparing both methods to current flow simulations based on personalized head models demonstrated a consistent increase in the coefficient of determination of ∆R2=0.12 for the current-induced magnetic fields and ∆R2=0.22 for the current flow reconstructions. Interestingly, some of the simulations still clearly deviated from the measurements despite of the strongly improved measurement quality. This suggests that MRCDI can reveal useful information for the improvement of head models used for current flow simulations. Conclusion: The advanced method strongly improves the sensitivity and robustness of MRCDI and is an important step from proof-of-concept studies towards a broader application of MRCDI in clinical and basic neuroscience research.

scholarly journals On the Reconstruction of Magnetic Resonance Current Density Images of the Human Brain: Pitfalls and Perspectives

2021 ◽  
Author(s):  
Hasan H. Eroğlu ◽  
Oula Puonti ◽  
Cihan Göksu ◽  
Fróði Gregersen ◽  
Hartwig R. Siebner ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Human Brain ◽  
Current Density ◽  
Signal To Noise Ratio ◽  
Ground Truth ◽  
Statistical Testing ◽  
Signal To Noise ◽  
Testing Approach ◽  
Resonance Current

ABSTRACTMagnetic resonance current density imaging (MRCDI) of the human brain aims to reconstruct the current density distribution caused by transcranial electric stimulation from MR-based measurements of the current-induced magnetic fields. The reconstruction problem is challenging due to a low signal-to-noise ratio and a limited volume coverage of the MR-based measurements, the lack of data from the scalp and skull regions and because MRCDI is only sensitive to the component of the current-induced magnetic field parallel to the scanner field. Most existing reconstruction approaches have been validated using simulation studies and measurements in phantoms with simplified geometries. Only one reconstruction method, the projected current density algorithm, has been applied to human in-vivo data so far, however resulting in blurred current density estimates even when applied to noise-free simulated data.We analyze the underlying causes for the limited performance of the projected current density algorithm when applied to human brain data. In addition, we compare it with an approach that relies on the optimization of the conductivities of a small number of tissue compartments of anatomically detailed head models reconstructed from structural MR data. Both for simulated ground truth data and human in-vivo MRCDI data, our results indicate that the estimation of current densities benefits more from using a personalized volume conductor model than from applying the projected current density algorithm. In particular, we introduce a hierarchical statistical testing approach as a principled way to test and compare the quality of reconstructed current density images that accounts for the limited signal-to-noise ratio of the human in-vivo MRCDI data and the fact that the ground truth of the current density is unknown for measured data. Our results indicate that the statistical testing approach constitutes a valuable framework for the further development of accurate volume conductor models of the head. Our findings also highlight the importance of tailoring the reconstruction approaches to the quality and specific properties of the available data.

scholarly journals Human in-vivo brain magnetic resonance current density imaging (MRCDI)

NeuroImage ◽  
2018 ◽  
Vol 171 ◽  
pp. 26-39 ◽  
Author(s):  
Cihan Göksu ◽  
Lars G. Hanson ◽  
Hartwig R. Siebner ◽  
Philipp Ehses ◽  
Klaus Scheffler ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Current Density ◽  
Current Density Imaging ◽  
Resonance Current

scholarly journals [OA019] Human in-vivo Magnetic Resonance Current Density Imaging (MRCDI) and MR Electrical Impedance Tomography (MREIT)

2018 ◽  
Vol 52 ◽  
pp. 8
Author(s):  
Cihan Göksu ◽  
Lars G. Hanson ◽  
Hartwig R. Siebner ◽  
Philipp Ehses ◽  
Klaus Scheffler ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Electrical Impedance Tomography ◽  
Current Density ◽  
Electrical Impedance ◽  
Impedance Tomography ◽  
Current Density Imaging ◽  
Resonance Current

scholarly journals Human in-vivo magnetic resonance current density imaging of the brain by optimizing head tissue conductivities

2021 ◽  
Vol 14 (6) ◽  
pp. 1591-1592
Author(s):  
Hasan H. Eroglu ◽  
Oula Puonti ◽  
Cihan Göksu ◽  
Fróði Gregersen ◽  
Hartwig R. Siebner ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Current Density ◽  
Current Density Imaging ◽  
The Brain ◽  
Resonance Current
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