Contact

Ioannis Angelos Giapitzakis

Address: Max-Planck-Ring 11
72076 Tübingen
Room number: 1.B.13
Phone: +49 7071 601 918
Fax: +49 7071 601 702
E-Mail: ioannis.giapitzakis

 

Picture of Giapitzakis, Ioannis Angelos

Ioannis Angelos Giapitzakis

Position: PhD Student  Unit: 

The last twenty years several techniques have been developed enabling the investigation of the function of human brain, as well as the study of the biochemical procedures taking place in the brain.


Magnetic Resonance Imaging plays an predominant role in this direction. Methods such as functional MRI (f-MRI), Diffusion Tensor Imaging (DTI) and Spectroscopy (MRS) further enlight  our knowledge about the human brain function.

 

During my  studies I have dealt mainly with fMRI and DTI, gaining significant knowledge and experience regarding the applications of these methods in neurosciences. My previous research concerned the study of myelination process in children with craniosynostosis (Diploma thesis) and the combination of DTI and fMRI to investigate the default mode network (DMN) in people suffering from posterior cortical atrophy (PCA)

 

However, my main goal was eventually to deal further with the MRS and its applications in neurosciences. The aim of my current PhD research is first the development of a robust protocol of MRS exploiting all the advantages of the Ultra High Fields (UHF) scanners (increased Signal to Noise ratio, higher spectral resolution, increased frequency dispersion of the metabolites). In the last stage, this protocol will be implemented in behavioural sciences and neurosciences. In particular, in studies using pharmacological stimulation

 

My current scientific interests are focused on the development of innovative methods for MRS @ 9.4 Tesla. The main localization schemes which were developed and optimised for in vivo studies @ 9.4T are metabolite cycled STEAM (MC STEAM) and Metabolite cycled sLASER (MC sLASER). In addition, double inversion recovery technique was optimised for the characterization of the macromolecule baseline of in vivo  human brain @ 9.4T.

 

 

PhD project: Functional Magnetic Resonance Spectroscopy at ultra-high field strength


In vivo Proton Magnetic Resonance Spectroscopy (1H-MRS) is a non-invasive method allowing the detection, as well as the quantification of several biochemical compounds in the body. Many previous studies utilized the unique information offered by this technique in order to investigate the changes in the concentration of metabolites in the brain. As a consequence, useful conclusions can be extracted regarding the function and the metabolic procedures taking place in the brain. In addition, recent technological achievements regarding the hardware and the software used in magnetic resonance imaging (MRI) enable the research of the brain metabolite profiles at ultra-high magnetics fields (i.e. ≥7T). The advantages of higher static fields (Bo) concern mainly increased Signal to Noise Ratio (SNR) and higher chemical shift dispersion leading to better spectral resolution. Nonetheless, technical limitations due to Bo inhomogeneity, radiofrequency (RF) pulses, as well as chemical shift displacement and lipid contamination demand a better protocol to be established. For this purpose, this PhD project concerns the development and improvement of a protocol for the localization, post-processing and quantification of the MRS Signal. Finally, this protocol will be applied in functional MRS (f-MRS) studies using pharmacological stimulation.

 

 

Optimisation of Asymmetric Adiabatic Pulses for Single Voxel Metabolite Cycled 1H-MRS in the Human Brain at 9.4 Tesla


Metabolite cycling is a method in which the metabolites either up-field or down-field of the water peak are alternately inverted [1] using asymmetric adiabatic pulses [2] leaving the water peak highly unaffected. Thus, the subtraction of two consecutive acquisitions leads to a spectrum without the water peak while the sum to a pure water peak spectrum. The advantages of this technique compare to other water suppression techniques are that the water signal can be used for frequency alignment and absolute quantification [3, 4]. The purpose of this research was to optimize the characteristics of the asymmetric adiabatic pulse for metabolite cycling implemented in a STEAM sequence at 9.4 Tesla.

 

TBW simulated for different B1+ values and pulse durations, with a frequency factor of 2. B) Longitudinal magnetization profile simulated for different B1+ values and frequency factors for a pulse duration of 23 ms

 

[1] Dreher W., Leibfritz D. MRM. 2005; 54(1):190-195 [2] Hwang T., van Zijl, Garwood M. JMR. 1999; 138(1):173-177 [3] Donnie Cameron et al. Proc 21st ISMRM. 2009:1359 [4] Andreas Hock et al. MRM. 2013; 69(5):1253-1260

 

Comparison of different methods for combination of multichannel spectroscopy data


Single voxel magnetic resonance spectroscopy (SVS) enables the study of several metabolites in different body parts yielding useful information regarding the underlying biochemical procedures. For reliable quantification and interpretation of the data a high signal to noise ratio (SNR) is required. One solution to this problem is the implementation of phased-array coils. However, one question immediately arising is how the spectra from multiple receive channels can be combined in order to give the best result. In this study three different methods  for the combination of multichannel SVS data [1-4] were compared with respect to multiple evaluation  criteria: 1) Brown’s method [2], 2) singular value decomposition (SVD) method [3] and generalized least squares (GLS) method [4] .

A) Change of the real part of the weighting factors. On the x-axis the NEX is indicated. B) Combined spectrum using in vivo data (NEX =160).  The number next to the spectrum indicates the change of the weighting factor.

[1] Wright S. NRMB. 1997; 52:394-410 [2] Brown M. MRM. 2004; 52:1207-1213 [3] Bydder M. et al. MRI. 2008; 26:847-850 [4] An L. et al. JMRI. 2013; 37:1445-1450.

 

Metabolite cycled single voxel 1H spectroscopy at 9.4T

 


 

Non-water suppressed metabolite cycled proton magnetic resonance spectroscopy (MC 1H-MRS) has been proven to enhance the frequency resolution and the signal to noise ratio (SNR) of the spectrum at 3 Tesla [1-2]. This is achieved by enabling shot-by-shot frequency and phase alignment due to the simultaneous acquisition of water and metabolite spectra.  Previously the adiabatic inversion pulse for MC 1H-MRS was optimized to exploit these advantages for application in the human brain at 9.4T [3].  In this work, we examine the performance of STEAM [4] based MC 1H-MRS [3,5] compared to water suppressed 1H-MRS using a numerically optimized short water suppression (WS) sequence with respect to spectral resolution and signal-to-noise ratio (SNR) in the human brain at 9.4T.

MC 1H-MRS resulted in a spectrum with high frequency resolution allowing the detection of several metabolites. Asp: aspartate; PE: phosphoryl-ethanolamine; Gln: Glutamine; Glu: glutamate; Tau: taurine; Glx: Gln + Glu; Cho: choline; mI:myo-inosotol; sI: scyllo-inosotol; Cr: creatine; NAA: N-acetyl aspartate; GABA: γ-aminobutyric acid. A Gaussian filter (standard deviation: 40ms) and a lorenzian filter were applied (-11.4Hz) for volunteer 2 and 3. Averages with different number of acquisitions are shown.

 

[1] MacMillan E.L. et al. MRM. 2011; 65:1239-1246 [2] Hock A. et al. MRM. 2013; 69:1253-1260 [3] Giapitzakis I.A. et al. Proc 22nd ISMRM: 2014:2895 [4] Frahm J. et al. MRM. 1989; 79-93 [5] MacMillan E.L. et al. Proc 19th ISMRM. 2011:1412

PERSONAL DETAILS

 

Name:          Ioannis-Angelos

Surname:      Giapitzakis

Place of birth: Athens, Hellenic Republic

Birthday:       28 Sep 1988

Nationality:    Hellenic/Italian

 

EDUCATION

 


2012- Current    Max Planck Institute for Biological Cybernetics (KYB)

Department of High-Field Magnetic Resonance

Research group of MR Spectroscopy and Ultra-High Field Methodology

PhD student

PhD title: Magnetic Resonance Spectroscopy in human brain at Ultra High Filed Strength: Methods and Applications

Group Leader-Supervisor: Dr. Anke Henning

 

2011-2012 Imperial College London (ICL)

Department of Bioengineering

MSc & DIC in Biomedical Engineering with Medical Physics

Overall grade: 75.9%

Thesis: Co-analysis of resting state functional magnetic resonance imaging and diffusion tensor imaging for correlation of default mode network and ultra-structural deficit in posterior cortical atrophy (Grade: 86.7%)


2006-2011 National Technical University of Athens (NTUA)

School of Applied Mathematics and Physical Sciences (SEMFE)

Diploma in Applied Mathematics and Physical Sciences  (5 years)

Majors: 1) Nuclear Physics and Elementary Particles & 2) Optoelectronics and Laser

Overall Grade: 8.25/10

Thesis: The magnetic Tractography in the investigation of myelination in the human brain (Grade: 10/10 “Excellent”)

 

2003-2006 2nd High School of Kallithea, Athens, Greece

 

SCHOLARSHIPS-AWARDS


2017- Summa and Manga Cum Laude award - ISMRM


2016- Magna Cum Laude award - ISMRM

 

2012-2016   Max Planck Institute PhD Grant for my doctoral (PhD) studies


2012-2015  Scholarship from the Greek State Scholarships Foundation (IKY) and European Social Fund for my doctoral (PhD) studies

 

2011-2012 Institute of Engineering and Physics in Medicine (IPEM) award for the best MSc project in Medical Physics

2011-2012 Master of Science (MSc) with Merit


2011-2012  Scholarship from the Greek State Scholarships Foundation (IKY) and European Social Fund for my Postgraduate studies

 

 

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Talks (16):

Scheidegger M, Fuchs A, Ametamey S, Kuhn F, Giapitzakis IA, Johayem A, Buck A, Seifritz E and Henning A (March-20-2015) Abstract Talk: Observation of synaptic plasticity in the healthy human brain upon Ketamine infusion by 11C-ABP688-PET and 2D J-resolved 1H MRS, 10th Annual Meeting of the European Society for Molecular Imaging (EMIM 2015), Tübingen, Germany(300).
Giapitzakis I (September-13-2013) Invited Lecture: Functional magnetic resonance spectroscopy at ultra-high field strength, Networks! 2013: 4th German Neurophysiology PhD Meeting, Tübingen, Germany.
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Last updated: Monday, 22.05.2017