Tıbbi Görüntüleme Teknikleri Bölümü Koleksiyonu
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- ItemFabrication of Al/n-GaN/p-Si/Al diodes by thermal evaporation and evaluation of effect of gamma irradiation on device properties(Elsevier, 2024-12) Olkun, Ali; Kaplan, Hüseyin Kaan; Akay, Sertan Kemal; Sarsıcı, Serhat; Erdoğan, Nursev; 414025This study investigates the impact of gamma-irradiation on the material and device properties of Al/n-GaN/p-Si/Al heterojunction diodes. GaN thin films were deposited on glass and p-Si substrates using thermal evaporation, followed by annealing at 450 degrees C. The diodes were subjected to gamma-irradiation doses of 0, 3, and 6 kGy. X-ray diffraction (XRD) measurements revealed significant structural changes, including phase transitions influenced by radiation. Electrical characteristics were assessed through current-voltage (I-V) measurements within the +/- 2 V range. Notably, the ideality factor for the annealed diodes improved from 6.60 to 4.62 and 3.85 with increased gamma-irradiation. The barrier height was determined to be 0.85 eV, and it did not exhibit a significant change upon gamma-irradiation dose. The results provided valuable insights into the response of heterojunction diodes to radiation exposure, aiding in the understanding and potential improvement of the radiation resistance of GaN-based electronic devices.
- ItemMultimodal imaging analysis of autosomal recessive Parkinson’s disease(Springer, 2025-04) Soydaş Turan, Başak; Yalçın Çakmaklı, Gül; Lay Ergün, Eser; Daşgın, Hacer; Karlı Oğuz, Kader; Elibol, Bülent; Uğur, Ömer; Volkan Salancı, Bilge; 396621Objective Pathophysiological backgrounds of idiopathic Parkinson’s disease (IPD) and autosomal recessive monogenic Parkinson’s disease (AR-PD) have common features that can be assessed through multimodal imaging. In this study, the striatal and myocardial dopaminergic innervation, brain 18F-FDG metabolism, resting-state functional activity of basal ganglia network (BGN) and white-matter (WM) microstructure were evaluated in AR-PD with respect to IPD, to investigate whether AR-PD can be subtyped as “brain-first” parkinsonism according to recent etiopathogenetic classification effort. Methods Forty patients (17 with Parkin, 3 with DJ-1 mutations and 20 with IPD) were included. Striatal dopaminergic innervation was assessed semi-quantitatively by 18F-DOPA PET, and cardiac 18F-DOPA uptake was also evaluated. Brain 18F-FDG PET images were evaluated visually. Resting-state functional MRI and diffusion tensor imaging (DTI) were used to assess the BGN activity and WM microstructural alterations. Results AR-PD patients showed significantly decreased 18F-DOPA uptake in caudate corpus compared to both IPD and controls, with a more symmetrical striatal dopaminergic denervation. Myocardial 18F-DOPA uptake in AR-PD was similar to controls, while it was significantly reduced in IPD. There was no significant difference in cortical 18F-FDG metabolism and functional activity of BGN between PD groups. The DTI data revealed more extensive WM microstructural damage in AR-PD compared to IPD. Conclusions AR-PD group showed additional significant decreased 18F-DOPA uptake in caudate corpus and more symmetrical striatal denervation. Additionally, relatively preserved myocardial innervation, cortical metabolic and WM microstructural changes suggest the possibility of “brain-first” type progression in AR-PD. Also, 18F-DOPA PET/CT may be a practical tool for evaluating dopaminergic innervation of striatum and heart together, but further evaluation is needed in this area.
- ItemShort-term prognostic value of the culprit-SYNTAX score in patients with acute myocardial infarction(MDPI, 2023) Peker, Tezcan; Boyraz, Bedrettin; 313898Background: The SYNergy between Percutaneous Coronary Intervention with TAXus and Cardiac Surgery (SYNTAX) score is a scoring system that helps to decide on surgery or percutaneous coronary intervention (PCI) in patients with acute myocardial infarction (MI), and studies are showing the prognostic value of this scoring system in both MI and coronary artery disease patients undergoing PCI. In acute coronary syndrome (ACS) patients, the infarct-related artery and the complexity of the lesions are also important in terms of mortality and morbidity. Our study aimed to determine the prognostic value of the culprit vessel’s SYNTAX score (cul-SS) in patients presenting with MI. Methods: In our study, 1284 patients presenting with MI were analyzed retrospectively. The SYNTAX scores and cul-SS of the patients were calculated. In-hospital and 30-day deaths and major complications were accepted as primary outcomes. The SYNTAX scores and cul-SS were compared in terms of predicting primary outcomes. Conclusions: Major complications were observed in 36 (2.8%) patients, death in 42 (3.3%) patients, and stent thrombosis in 24 (1.9%) patients. The area under the curves for SYNTAX and cul-SS for predicting primary outcomes is 0.64 and 0.68 (p = 0.026), respectively. Cul-SS was as successful as the SYNTAX score in predicting stent thrombosis and was superior in predicting short-term death and major complications.
- ItemThe effect of being married on heart rate variability, an indicator of autonomic dysfunction: A retrospective study(Lippincott Williams & Wilkins, 2023) Akgümüş, Alkame; Balun, Ahmet; Peker, Tezcan; Boyraz, Bedrettin; 313898Heart rate variability (HRV) is a noninvasive assessment that reflects the autonomic functions of the heart and is known to be impaired in many diseases. In our study, we aimed to investigate the relationship between HRV and being married. The study included 104 patients, between the aged 20 to 40 years were included in the study. The patients were divided into 2 groups as 53 healthy married (group 1) and 51 healthy unmarried (group 2). 24-hour rhythm Holter recordings were performed on all married and unmarried patients. Group 1 had a mean age of 32 ± 5 years and 47.2% men, and group 2 had a mean age of 30 ± 5 years and 54.9% men. Standard deviation of normal to normal (SDNN) was 150 ± 40 versus 128 ± 30 (P = .003), SDNN index was 66 ± 20 versus 56 ± 12 (P = .004), the square root of the mean of the squares of the differences of the adjacent root mean square of successive differences (RMSSD) was 37 ± 10 versus 30 ± 10 (P < .001), percentage of successive R-R intervals that differ by more than 50 milliseconds (PNN50) was 13.5 ± 7 versus 8.5 ± 7 (P = .001), HF was 450 ± 270 versus 225 ± 130 (P < .001) found to be significantly less in the group 2. LF/HF ratio was 1.68 ± 0.65 versus 3.31 ± 1.56 (P < .001) found to be significantly higher in the group 2. In our study, it is possible to say that the sympathetic system effect on the heart was more dominant and the HRV was lower in the unmarried group.
- ItemThe role of advanced glycation end-product levels measured by skin autofluorescence in the development of mitral annular calcification(MDPI, 2023) Boyraz, Bedrettin; Peker, Tezcan; 313898As a person ages, mitral annular calcification develops in the mitral annulus with increasing frequency. Lipid deposition, inflammation, and aging-related degeneration have been cited as potential causes of this pathophysiology, though there is currently no conclusive evidence to support this. AGEs accumulate in tissues due to the glycation of proteins and lipids, increasing the release of proinflammatory cytokines secondary to oxidative stress through the AGE receptor. The AGE levels increase in diabetic microvascular complications and degenerative aortic valve disease. Our study was planned prospectively as a case–control study involving 94 MAC-positive patients and 94 MAC-negative patients. The demographics, echocardiographic data and AGE levels of the patients were measured and recorded using the skin autofluorescence method. AGE levels were significantly higher in the MAC-positive patient group (3.2 vs. 2.7; p < 0.001). The AGE levels were observed as an independent predictor of MAC development in a regression analysis (OR: 8.05, 95% CI: 3.74–17.33, p < 0.001). In a ROC-curve analysis, the AUC was 0.79 (95% CI: 0.72–0.85). At a cut-off value of 2.7, 79.7% sensitivity and 69.1% specificity were observed. AGE levels can be used to cheaply, easily and non-invasively identify patients at risk of developing MAC.
