Contact

Mario Baez

Address: Spemannstr. 41
72076 Tübingen
Room number: 3.B.10
Phone: +49 7071 601 942
Fax: +49 7071 601 702
E-Mail: Mario.Baez

 

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Mario Baez

Position: PhD Student  Unit: Scheffler

Biomedical Engineer
PhD Student at Max Planck Institute for Biological Cybernetics

Sequences and Signals, NMR and MRI Signal Formation, fMRI & Monte-Carlo Simulations

Monte-Carlo Simulation of GE, SE and bSSFP MR signal formation in Neurovascular Tissue at 9.4 T

Modelling the functional nuclear magnetic resonance (NMR) signal opens the possibility to go beyond the actual magnetic resonance imaging (MRI) resolution and extract the fingerprint mesoscopic structure immerse in an imaged voxel.

High resolution fMRI is one of the most interestingly imaging acquisition methods because it allows more accurate spatial mapping of brain responses. This type of mapping relies on the blood oxygen level dependent (BOLD) contrast, and is closely related with the dynamics of the neurovascular network, responsible of the hemodynamics exchanges. Moreover, high resolution fMRI start to reveal the vascular and metabolic heterogeneity of the cortex, since the relevant contributor structures are of a similar size as the image resolution. To accurately predict high resolution BOLD responses, the characterisitc features of the model and the NMR signal needs to be modeled explicitly.

Biological tissues have a complicated chemical composition and geometrical architecture that influence the MR signal formation. In the presence of an external magnetic field, differences in magnetic susceptibilities between adjacent compartments generate local magnetic field perturbations, and hence a range of magnetic resonance frequency shifts. In addition, water molecules are not static but diffuse freely or restricted within this local inhomogenous field pattern, including an extra-dephasing incoherence to the spin frequency.

The use of bSSFP acquisition sequence in a fMRI experiment and the relation of the MR signal at microscopic scales is poorly understood. Aiming to understand the brain function and its relation with the MR signal, computer simulations supply valuable information to clarify this MR signal formation under realistic tissue properties scheme in both health and disease.

Neurovascular structure acquired with two-photon imaging from the rat brain cortex. Cylinders in different orientations respect to the main magnetic field mimicking homogeneous neurovascular structures. The frequency distribution shift created by the de-/oxy hemoglobin states can be calculated by analytical methods. The molecular motion within the frequency distribution exhibit by the model can be modelated with random walkers.

  • Ph.D. Student, Prof. K. Scheffler, High-Field Magnetic Resonance, Magnetic Resonance Center, MPI for Biological Cybernetics, Germany, Nov 2013-
  • Intership, Prof. P. Tobler, Neuroeconomics, Department of Economics, University of Zurich, Switzerland, Sept 2012 -Nov 2012.
  • Master of Science in Biomedical Engineer, Prof. G. Pacheco-Lopez, Autonomous Metropolitan University, Mexico, April 2011 – July 2013
  • Biomedical Engineer, Autonomous Metropolitan University, Mexico, January 2007 – March 2011

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Articles (2):

Báez-Yánez MG, Ehses P, Mirkes C, Tsai PS, Kleinfeld D and Scheffler K (September-2017) The impact of vessel size, orientation and intravascular contribution on the neurovascular fingerprint of BOLD bSSFP fMRI NeuroImage 163 13–23.
Montiel-Castro AJ, Baez-Yanez MG and Pacheco-Lopez G (July-2014) Social Neuroeconomics: The Influence of Microbiota in Partner-Choice and Sociality Current Pharmaceutical Design 20(29) 4774-4783.

Conference papers (1):

Báez-Yánez MG, Tsai PS, Kleinfeld D and Scheffler K (November-2017) The impact of vessel size, orientation and intravascular contribution on the V16 neurovascular fingerprint of BOLD bSSFP fMRI, 20. Jahrestagung der Deutschen Sektion der International Society for Magnetic Resonance in Medicine (ISMRM-DS 2017), 83-87.

Posters (3):

Ehses P, Báez-Yánez M, Erb M and Scheffler K (April-27-2017): Asymmetries of the balanced SSFP profile allow to probe microstructure anisotropy at 9.4 Tesla, 25th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2017), Honolulu, HI, USA.
Báez-Yánez M, Ehses P and Scheffler K (April-27-2017): The Impact of the Local, Mesoscopic Frequency Distribution and Diffusion in Gray and White Matter to the Static bSSFP Signal Profile, 25th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2017), Honolulu, HI, USA.
Scheffler K, Kleinfeld D, Tsai P, Báez-Yánez M and Ehses P (April-27-2017): The neurovascular fingerprint of BOLD bSSFP: the impact of vessel size, orientation and intravascular contribution, 25th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2017), Honolulu, HI, USA.

Talks (1):

Baez Yanez MG, Ehses P and Scheffler K (May-12-2016) Abstract Talk: The BOLD-sensitivity of balanced SSFP at very high fields is similar to GE-EPI but more selective to small vessels, 24th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2016), Singapore(0949).

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Last updated: Monday, 22.05.2017