Browsing by Subject "Magnetic resonance spectroscopy"

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Open Access
Investigation of Heschl's gyrus and planum temporale in patients with schizophrenia and bipolar disorder: a proton magnetic resonance spectroscopy study
(Elsevier, 2015) Atagün, M. İ.; Şıkoğlu, E. M.; Can, S. S.; Karakaş-Uğurlu, G.; Ulusoy-Kaymak, S.; Çayköylü, A.; Algın,Oktay; Phillips, M. L.; Moore, C. M.; Öngür, D.
Background: Superior temporal cortices include brain regions dedicated to auditory processing and several lines of evidence suggest structural and functional abnormalities in both schizophrenia and bipolar disorder within this brain region. However, possible glutamatergic dysfunction within this region has not been investigated in adult patients. Methods: Thirty patients with schizophrenia (38.67 ± 12.46. years of age), 28 euthymic patients with bipolar I disorder (35.32 ± 9.12. years of age), and 30 age-, gender- and education-matched healthy controls were enrolled. Proton magnetic resonance spectroscopy data were acquired using a 3.0. T Siemens MAGNETOM TIM Trio MR system and single voxel Point REsolved Spectroscopy Sequence (PRESS) in order to quantify brain metabolites within the left and right Heschl's gyrus and planum temporale of superior temporal cortices. Results: There were significant abnormalities in glutamate (Glu) (F(2,78) = 8.52, p < 0.0001), N-acetyl aspartate (tNAA) (F(2,81) = 5.73, p = 0.005), creatine (tCr) (F(2,83) = 5.91, p = 0.004) and inositol (Ins) (F(2,82) = 8.49, p < 0.0001) concentrations in the left superior temporal cortex. In general, metabolite levels were lower for bipolar disorder patients when compared to healthy participants. Moreover, patients with bipolar disorder exhibited significantly lower tCr and Ins concentrations when compared to schizophrenia patients. In addition, we have found significant correlations between the superior temporal cortex metabolites and clinical measures. Conclusion: As the left auditory cortices are associated with language and speech, left hemisphere specific abnormalities may have clinical significance. Our findings are suggestive of shared glutamatergic abnormalities in schizophrenia and bipolar disorder. © 2013 Elsevier B.V.
Open Access
Neurochemical differences between bipolar disorder type I and II in superior temporal cortices: a proton magnetic resonance spectroscopy study
(Elsevier B.V., 2018) Atagün, M. İ.; Şıkoğlu, E. M.; Can, S. S.; Uğurlu, G. K.; Kaymak, S. U.; Çayköylü, A.; Algın, Oktay; Phillips, M. L.; Moore, C. M.; Öngür, D.
Background: Despite the diagnostic challenges in categorizing bipolar disorder subtypes, bipolar I and II disorders (BD-I and BD-II respectively) are valid indices for researchers. Subtle neurobiological differences may underlie clinical differences between mood disorder subtypes. The aims of this study were to investigate neurochemical differences between bipolar disorder subtypes. Methods: Euthymic BD-II patients (n = 21) are compared with BD-I (n = 28) and healthy comparison subjects (HCs, n = 30). Magnetic Resonance Imaging (MRI) and proton spectroscopy (1H MRS) were performed on a 3T Siemens Tim Trio system. MRS voxels were located in the left/right superior temporal cortices, and spectra acquired with the single voxel Point REsolved Spectroscopy Sequence (PRESS). The spectroscopic data were analyzed with LCModel (Version 6.3.0) software. Results: There were significant differences between groups in terms of glutamate [F = 6.27, p = 0.003], glutamate + glutamine [F = 6.08, p = 0.004], inositol containing compounds (Ino) (F = 9.25, p < 0.001), NAA [F = 7.63, p = 0.001] and creatine + phosphocreatine [F = 11.06, p < 0.001] in the left hemisphere and Ino [F = 5.65, p = 0.005] in the right hemisphere. Post-hoc comparisons showed that the BD-I disorder group had significantly lower metabolite levels in comparison to the BD-II and the HC groups. Limitations: This was a cross-sectional study with a small sample size. In addition, patients were on various psychotropic medications, which may have impacted the results. Conclusions: Neurochemical levels, in the superior temporal cortices, measured with 1H-MRS discriminated between BD-II and BD-I. Although further studies are needed, one may speculate that the superior temporal cortices (particularly left hemispheric) play a critical role, whose pathology may be related to subtyping bipolar disorder.
Open Access
Perisylvian GABA levels in schizophrenia and bipolar disorder
(Elsevier Ireland Ltd, 2017) Atagün, M. İ.; Şıkoglu, M. E.; Soykan, Ç.; Can, S. S.; Ulusoy-Kaymak S.; Çayköylü, A.; Algın O.; Phillips, M. L.; Öngür, D.; Moore, C. M.
The aim of this study is to measure GABA levels of perisylvian cortices in schizophrenia and bipolar disorder patients, using proton magnetic resonance spectroscopy (1H-MRS). Patients with schizophrenia (n = 25), bipolar I disorder (BD-I; n = 28) and bipolar II disorder (BD-II; n = 20) were compared with healthy controls (n = 30).1H-MRS data was acquired using a Siemens 3 T whole body scanner to quantify right and left perisylvian structures’ (including superior temporal lobes) GABA levels. Right perisylvian GABA values differed significantly between groups [χ2= 9.62, df: 3, p = 0.022]. GABA levels were significantly higher in the schizophrenia group compared with the healthy control group (p = 0.002). Furthermore, Chlorpromazine equivalent doses of antipsychotics correlated with right hemisphere GABA levels (r2= 0.68, p = 0.006, n = 33). GABA levels are elevated in the right hemisphere in patients with schizophrenia in comparison to bipolar disorder and healthy controls. The balance between excitatory and inhibitory controls over the cortical circuits may have direct relationship with GABAergic functions in auditory cortices. In addition, GABA levels may be altered by brain regions of interest, psychotropic medications, and clinical stage in schizophrenia and bipolar disorder. ï¿½ 2016 Elsevier Ireland Ltd
Open Access
Tetrastyryl-bodipy dyes: convenient synthesis and characterization of elusive near IR fluorophores
(2009) Buyukcakir, O.; Bozdemir, O. A.; Kolemen, S.; Erbas, S.; Akkaya, E. U.
1,3,5,7-Tetramethyl-Bodipy derivatives undergo Knoevenagel-type condensations with aromatic aldehydes to ultimately yield tetrastyryl-Bodipy derivatives. The resulting dyes absorb and emit strongly In the near IR. As the versatility of the Bodipy dyes are fully appreciated, these new tetrastyryl dyes are likely to be featured In a variety of functional supramolecular systems. © 2009 American Chemical Society.
Open Access
Uniqueness and reconstruction in magnetic resonance-electrical impedance tomography (MR-EIT)
(Institute of Physics Publishing, 2003) İder, Y. Z.; Onart, S.; Lionheart, W. R. B.
Magnetic resonance-electrical impedance tomography (MR-EIT) was first proposed in 1992. Since then various reconstruction algorithms have been suggested and applied. These algorithms use peripheral voltage measurements and internal current density measurements in different combinations. In this study the problem of MR-EIT is treated as a hyperbolic system of first-order partial differential equations, and three numerical methods are proposed for its solution. This approach is not utilized in any of the algorithms proposed earlier. The numerical solution methods are integration along equipotential surfaces (method of characteristics), integration on a Cartesian grid, and inversion of a system matrix derived by a finite difference formulation. It is shown that if some uniqueness conditions are satisfied, then using at least two injected current patterns, resistivity can be reconstructed apart from a multiplicative constant. This constant can then be identified using a single voltage measurement. The methods proposed are direct, non-iterative, and valid and feasible for 3D reconstructions. They can also be used to easily obtain slice and field-of-view images from a 3D object. 2D simulations are made to illustrate the performance of the algorithms.