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Publication Metadata only Denoising embolic Doppler ultrasound signals using Dual Tree Complex Discrete Wavelet Transform(2010) Serbes, Görkem; Aydın, Nizamettin; Serbes, Görkem, Department of Electrical Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey; Aydın, Nizamettin, Department of Computer Engineering, Yıldız Teknik Üniversitesi, Istanbul, TurkeyEarly and accurate detection of asymptomatic emboli is important for monitoring of preventive therapy in stroke-prone patients. One of the problems in detection of emboli is the identification of an embolic signal caused by very small emboli. The amplitude of the embolic signal may be so small that advanced processing methods are required to distinguish these signals from Doppler signals arising from red blood cells. In this study instead of conventional discrete wavelet transform, the Dual Tree Complex Discrete Wavelet Transform was used for denoising embolic signals. Performances of both approaches were compared. Unlike the conventional discrete wavelet transform discrete complex wavelet transform is a shift invariant transform with limited redundancy. Results demonstrate that the Dual Tree Complex Discrete Wavelet Transform based denoising outperforms conventional discrete wavelet denoising. Approximately 8 dB improvement is obtained by using the Dual Tree Complex Discrete Wavelet Transform compared to the improvement provided by the conventional Discrete Wavelet Transform (less than 5 dB). © 2010 IEEE. © 2011 Elsevier B.V., All rights reserved.Publication Metadata only Feature extraction using time-frequency/scale analysis and ensemble of feature sets for crackle detection(2011) Serbes, Görkem; Sakar, C. Okan; Kahya, Yasemin Palanduz; Aydın, Nizamettin; Serbes, Görkem, Department of Mechanical Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey; Sakar, C. Okan, Department of Computer Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey; Kahya, Yasemin Palanduz, Department of Electrical Engineering, Boğaziçi Üniversitesi, Bebek, Turkey; Aydın, Nizamettin, Department of Computer Engineering, Yıldız Teknik Üniversitesi, Istanbul, TurkeyPulmonary crackles are used as indicators for the diagnosis of different pulmonary disorders. Crackles are very common adventitious sounds which have transient characteristic. From the characteristics of crackles such as timing and number of occurrences, the type and the severity of the pulmonary diseases can be obtained. In this study, a novel method is proposed for crackle detection. In this method, various feature sets are extracted using time-frequency and time-scale analysis. The extracted feature sets are fed into support vector machines both individually and as an ensemble of networks. Besides, as a preprocessing stage in order to improve the success of the model, frequency bands containing no-information are removed using dual tree complex wavelet transform, which is a shift invariant transform with limited redundancy and an improved version of discrete wavelet transform. The comparative results of individual feature sets and ensemble of sets with pre-processed and non pre-processed data are proposed. © 2011 IEEE. © 2012 Elsevier B.V., All rights reserved.Publication Metadata only Directional dual-tree complex wavelet packet transform(2013) Serbes, Görkem; Aydın, Nizamettin; Gülçür, Halil Ö.; Serbes, Görkem, Department of Biomedical Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey, Institute of Biomedical Engineering, Boğaziçi Üniversitesi, Bebek, Turkey; Aydın, Nizamettin, Department of Computer Engineering, Yıldız Teknik Üniversitesi, Istanbul, Turkey; Gülçür, Halil Ö., Institute of Biomedical Engineering, Boğaziçi Üniversitesi, Bebek, TurkeyDoppler ultrasound systems, which are widely used in cardiovascular disorders detection, have quadrature format outputs. Various types of algorithms were described in literature to process quadrature Doppler signals (QDS), such as phasing filter technique (PFT), fast Fourier transform method, frequency domain Hilbert transform method and complex continuous wavelet transform. However for the discrete wavelet transform (DWT) case, which becomes a common method for processing QDSs, there was not a direct method to recover flow direction from quadrature signals. Traditionally, to process QDSs with DWT, firstly directional signals have to be extracted and later two DWTs must be applied. Although there exists a complex DWT algorithm called dual tree complex discrete wavelet transform (DTCWT), it does not provide directional signal decoding during analysis because of the unwanted energy leaks into its negative frequency bands. Modified DTCWT, which is a combination of PFT and DTCWT, has the capability of extracting directional information while decomposing QDSs into different frequency bands, but it uses an additional Hilbert transform filter and it increases the computational complexity of whole transform. Discrete wavelet packet transform (DWPT), which is a generalization of the ordinary DWT allowing subband analysis without the constraint of dyadic decomposition, can perform an adaptive decomposition of the frequency axis. In this study, a novel complex DWPT, which maps directional information while processing QDSs, is proposed. The success of proposed method will be measured by using simulated quadrature signals. © 2013 IEEE. © 2013 Elsevier B.V., All rights reserved.Publication Metadata only Compression of the CT images using classified energy and pattern blocks(2013) Gökbay, İnci Zaim; Gezer, Murat; Güz, Ümit; Gürkan, Hakan; Yarman, Binboǧa Siddik; Gökbay, İnci Zaim, Department of Mechanics, Bahçeşehir Üniversitesi, Istanbul, Turkey; Gezer, Murat, Department of Informatics, Istanbul Üniversitesi, Istanbul, Turkey; Güz, Ümit, Department of Electrical and Electronic Engineering, Işik Üniversitesi, Istanbul, Turkey; Gürkan, Hakan, Department of Electrical and Electronic Engineering, Işik Üniversitesi, Istanbul, Turkey; Yarman, Binboǧa Siddik, Department of Electrical and Electronic Engineering, Işik Üniversitesi, Istanbul, TurkeyIn this work, a new biomedical image compression method is proposed based on the classified energy and pattern blocks (CEPB). CEPB based compression method is specifically applied on the Computed Tomography (CT) images and the evaluation results are presented. Essentially, the CEPB is uniquely designed and structured codebook which is located on the both the transmitter and receiver part of a communication system in order to implement encoding and decoding processes. The encoding parameters are block scaling coefficient (BSC) and the index numbers of energy (IE) and pattern blocks (IP) determined for each block of the input images based on the CEPB. The evaluation results show that the newly proposed method provides considerable image compression ratios and image quality. © 2013 IEEE. © 2013 Elsevier B.V., All rights reserved.Publication Open Access Controlling hypertension in Turkey: Not a hopeless dream(Nature Publishing Group, 2013) Şengül, S.; Erdem, Yunus; Akpolat, Tekin; Derici, Ülver Boztepe; Sindel, Şükrü; Karatan, Oktay; Turgan, Çetin; Hasanoğlu, Enver; Çağlar, Şali; Ertürk, Şehsuvar; Sengül, S., Department of Nephrology, Ankara Üniversitesi, Ankara, Turkey; Erdem, Yunus, Department of Nephrology, Hacettepe Üniversitesi, Ankara, Turkey; Akpolat, Tekin, Department of Nephrology, Bahçeşehir Üniversitesi, Istanbul, Turkey; Derici, Ülver Boztepe, Department of Nephrology, Gazi University, Faculty of Medicine, Ankara, Turkey; Sindel, Şükrü, Department of Nephrology, Gazi University, Faculty of Medicine, Ankara, Turkey; Karatan, Oktay, Department of Nephrology, Ankara Üniversitesi, Ankara, Turkey; Turgan, Çetin, Department of Nephrology, Hacettepe Üniversitesi, Ankara, Turkey; Hasanoĝlu, Enver, Department of Pediatric Nephrology, Gazi University, Faculty of Medicine, Ankara, Turkey; Çǎglar, Şali, Department of Nephrology, Hacettepe Üniversitesi, Ankara, Turkey; Ertürk, Şehsuvar, Department of Nephrology, Ankara Üniversitesi, Ankara, TurkeyDespite major progress in prevention, diagnosis, and treatment during the recent decades, hypertension remains the leading risk factor for cardiovascular disease and mortality throughout the world. The prevalence of hypertension in developing countries continues to rise reaching alarming rates. Several risk factors of hypertension appear to be more common in developing countries than in developed countries. In Turkey, hypertension is a prevalent condition affecting approximately 22.5 million individuals. Hypertension control (defined as blood pressure <140/90 mm Hg) rate increased from 8.1% in 2003 (first Prevalence, awareness, treatment, and control of hypertension in Turkey (PatenT) study) to 28.7% in 2012 (PatenT 2 study). Meanwhile, rates of cardiovascular morbidity and mortality remained high in Turkey. Controlling risk factors such as hypertension, tobacco use, unhealthy diet, obesity, diabetes, hyperlipidemia, and physical inactivity can prevent most of the deaths from cardiovascular disease. It is also crucial for the public health system to have a hypertension education program aimed at reducing cardiovascular disease and prevention and control of hypertension promoting a healthy lifestyle in Turkey. Such a program could positively affect other lifestyle-related diseases as well. Importantly, cooperation among the components of the health system could contribute to improved outcomes in hypertensive populations. © 2013 International Society of Nephrology. © 2024 Elsevier B.V., All rights reserved.Publication Metadata only Directional dual-tree rational-dilation complex wavelet transform(Institute of Electrical and Electronics Engineers Inc., 2014) Serbes, Görkem; Gülçür, Halil Ö.; Aydın, Nizamettin; Serbes, Görkem, Department of Biomedical Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey; Gülçür, Halil Ö., Institute of Biomedical Engineering, Boğaziçi Üniversitesi, Bebek, Turkey; Aydın, Nizamettin, Department of Computer Engineering, Yıldız Teknik Üniversitesi, Istanbul, TurkeyDyadic discrete wavelet transform (DWT) has been used successfully in processing signals having non-oscillatory transient behaviour. However, due to the low Q-factor property of their wavelet atoms, the dyadic DWT is less effective in processing oscillatory signals such as embolic signals (ESs). ESs are extracted from quadrature Doppler signals, which are the output of Doppler ultrasound systems. In order to process ESs, firstly, a pre-processing operation known as phase filtering for obtaining directional signals from quadrature Doppler signals must be employed. Only then, wavelet based methods can be applied to these directional signals for further analysis. In this study, a directional dual-tree rational-dilation complex wavelet transform, which can be applied directly to quadrature signals and has the ability of extracting directional information during analysis, is introduced. © 2021 Elsevier B.V., All rights reserved.Publication Metadata only Absence of Inferior Vena Cava in a Renal Transplant Recipient: A Case Report(Elsevier Inc., 2015) Eroǧlu, Atilla; Turunç, Volkan; Tabandeh, Babek; Oruʇ, Taner; Şener, Tufan; Deʇer, Erdal; Dheir, Hamad; Eroǧlu, Atilla, Organ Transplantation Center, Medical Park Hospital, Bursa, Turkey; Turunç, Volkan, Organ Transplantation Center, Medical Park Hospital, Bursa, Turkey; Tabandeh, Babek, Department of General Surgery, Bahçeşehir Üniversitesi, Istanbul, Turkey; Oruʇ, Taner, Department of General Surgery, Bahçeşehir Üniversitesi, Istanbul, Turkey; Şener, Tufan, Department of Cardiovascular Surgery, Medical Park Hospital, Bursa, Turkey; Deʇer, Erdal, Department of Radiology, Medical Park Hospital, Bursa, Turkey; Dheir, Hamad, Organ Transplantation Center, Medical Park Hospital, Bursa, TurkeyA 27-year-old woman was admitted to our department with end-stage renal failure due to reflux nephropathy. She had no history of deep venous thrombosis. After pretransplantation evaluation, her father was accepted for kidney donation. We observed intraoperatively that the patient's iliac veins and inferior vena cava (IVC) were absent. There were many venous collaterals, but none of them was dilated enough for renal vein anastomosis. Since we could not find a suitable vein for venous drainage of the allograft, we decided to stop donor surgery and postpone renal transplantation (RT) for detailed radiologic examination. Contrast-enhanced computed tomography revealed the absence of an infrahepatic segment of IVC. Superior mesenteric vein was thin. Portal and splenic veins were normal, but we decided not to use them for venous drainage because of increased risk of torsion. We informed the patient and her family about the situation and cancelled RT. Iliac vein and IVC anomalies are not absolute contraindications for RT, but when a dilated collateral vein is not present or when there is no option for safe renal vein anastomosis as in our case, RT may not be possible. © 2021 Elsevier B.V., All rights reserved.Publication Metadata only Renal Transplantation after Thoracic Endovascular Repair of Type B Aortic Dissection - A Case Report(Elsevier Inc., 2015) Eroǧlu, Atilla; Turunç, Volkan; Şener, Tufan; Tabandeh, Babek; Oruʇ, Taner; Gürol, Tayfun; Aydin, Alper; Güven, Bahtisen; Eroǧlu, Atilla, Organ Transplantation Center, Medical Park Hospital, Bursa, Turkey; Turunç, Volkan, Organ Transplantation Center, Medical Park Hospital, Bursa, Turkey; Şener, Tufan, Department of Cardiovascular Surgery, Medical Park Hospital, Bursa, Turkey; Tabandeh, Babek, Department of General Surgery, Bahçeşehir Üniversitesi, Istanbul, Turkey; Oruʇ, Taner, Department of General Surgery, Bahçeşehir Üniversitesi, Istanbul, Turkey; Gürol, Tayfun, Department of Cardiology, Bahçeşehir Üniversitesi, Istanbul, Turkey; Aydin, Alper, Department of Cardiology, Bahçeşehir Üniversitesi, Istanbul, Turkey; Güven, Bahtisen, Organ Transplantation Center, Medical Park Hospital, Bursa, TurkeyBecause of the strong association between uremia and atherosclerosis, incidence of aortic aneurysms is increasing among renal failure patients awaiting renal transplantation (RT). Successful RTs have been performed in these patients after surgical repair of the aneurysms. Since Parodi et al introduced endovascular aortic aneurysm repair (EVAR) in patients with high risk for conventional surgery, a new era has begun. The 1st successful RT after EVAR was published in 2001. Herein we report the 1st successful RT after thoracic EVAR (TEVAR) reported to date. We performed RT in a 54-year-old man with end-stage renal failure due to diabetic nephropathy, who had undergone TEVAR for type B aortic dissection (TBAD) 6 months earlier. The postoperative period was uneventful and the patient was discharged from the hospital at postoperative day 6 with a serum creatinine of 0.9 mg/dL. At follow-up examination at postoperative 6 months, graft function was stable. Because of its advantages over open surgery, including low mortality and morbidity, TEVAR is becoming more common among renal failure patients with thoracic aortic aneurysms and TBAD. Our case shows that successful RT can be performed in renal failure patients who have undergone TEVAR. © 2021 Elsevier B.V., All rights reserved.Publication Metadata only Femoro-femoral Bypass for Graft Salvage in a Renal Transplant Patient with Aorto-iliac Occlusion: A Case Report(Elsevier Inc., 2015) Turunç, Volkan; Eroǧlu, Atilla; Tabandeh, Babek; Şarkişlali, Kamil Umut; Şener, Tufan; Aydin, Alper; Gürol, Tayfun; Oruʇ, Taner; Turunç, Volkan, Organ Transplantation Center, Medical Park Hospital, Bursa, Turkey; Eroǧlu, Atilla, Organ Transplantation Center, Medical Park Hospital, Bursa, Turkey; Tabandeh, Babek, Department of General Surgery, Bahçeşehir Üniversitesi, Istanbul, Turkey; Şarkişlali, Kamil Umut, Department of Cardiovascular Surgery, Medical Park Hospital, Bursa, Turkey; Şener, Tufan, Department of Cardiovascular Surgery, Medical Park Hospital, Bursa, Turkey; Aydin, Alper, Department of Cardiology, Bahçeşehir Üniversitesi, Istanbul, Turkey; Gürol, Tayfun, Department of Cardiology, Bahçeşehir Üniversitesi, Istanbul, Turkey; Oruʇ, Taner, Department of General Surgery, Bahçeşehir Üniversitesi, Istanbul, TurkeyAs vascular diseases are becoming more prevalent among renal transplant recipients, complications related to renal artery anastomosis are likely to occur more often. Here we report a renal transplant patient treated with femoro-femoral bypass who had renal allograft dysfunction due to aorto-iliac occlusive disease (AIOD) proximal to renal artery anastomosis. We performed living donor renal transplantation in the left iliac fossa of a 41-year-old male. At post-transplant 30 months, he was admitted with hypertension, increase in serum creatinine, and claudication of his left leg. Doppler ultrasonography showed poor flow characteristics of the renal allograft. Total occlusion of the left common iliac artery was diagnosed on angiography. Since endovascular approach was unsuccessful, we performed right-to-left femoro-femoral bypass to provide retrograde blood flow to the renal allograft. The patient was discharged at postoperative day 3 with decreased serum creatinine, normal blood pressure, no claudication, and normal flow characteristics in Doppler ultrasonography. AIOD should be suspected in renal transplant patients in case of hypertension, allograft dysfunction, and ipsilateral leg ischemia. Femoro-femoral bypass is a safe surgical procedure that may be performed in patients who cannot be treated using an endovascular approach. © 2021 Elsevier B.V., All rights reserved.Publication Metadata only Escherichia Coli-Related Necrotizing Fasciitis after Renal Transplantation: A Case Report(Elsevier Inc., 2015) Turunç, Volkan; Eroǧlu, Atilla; Cihandide, Ercan; Tabandeh, Babek; Oruʇ, Taner; Güven, Bahtisen; Turunç, Volkan, Organ Transplantation Center, Medical Park Hospital, Bursa, Turkey; Eroǧlu, Atilla, Organ Transplantation Center, Medical Park Hospital, Bursa, Turkey; Cihandide, Ercan, Department of Plastic Surgery, Bahçeşehir Üniversitesi, Istanbul, Turkey; Tabandeh, Babek, Department of General Surgery, Bahçeşehir Üniversitesi, Istanbul, Turkey; Oruʇ, Taner, Department of General Surgery, Bahçeşehir Üniversitesi, Istanbul, Turkey; Güven, Bahtisen, Organ Transplantation Center, Medical Park Hospital, Bursa, TurkeyA 39-year-old man who had received cadaveric renal transplantation (RT) 1 month previously presented with rash and pain on his left lower extremity. Initially, bacterial cellulitis was suspected, and ampicillin/sulbactam was initiated, however, 3 days later, skin necrosis occurred and pain increased. Ampicillin/sulbactam was replaced with imipenem+ciprofloxacin, and surgical debridement was performed. Escherichia coli was identified in the wound culture, urine culture, and blood culture. After repeated debridement, wound care, and appropriate antimicrobial treatment, wounds began to heal and skin grafting was planned at the 4th month of therapy. However, the patient died of viral pneumonia. To date, 20 cases of necrotizing fasciitis (NF) after RT have been reported (including our case), and, as far as we know, this is the second E coli-related NF case. An analysis of all 20 cases showed that the most common infection site was the extremities (90%) and that 45% of pathogens were fungus. The mortality rate was 30%. NF is a rare but rapidly developing and life-threatening soft-tissue infection in RT patients. To reduce mortality rates, early diagnosis, recurrent surgical debridement, and aggressive therapy are mandatory. © 2021 Elsevier B.V., All rights reserved.