Researcher:
Demirkol, Mehmet Onur

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Mehmet Onur

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Demirkol

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Demirkol, Mehmet Onur

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2014 - 2019132020 - 202314

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    Determination of thyroglobulin levels by radioimmunoassay method in anti thyroglobulin positive differentiated thyroid patients: one center clinical experience
    (Pergamon-Elsevier Science Ltd, 2020) Uçar, Burcu; Şen, Melis; Acar, Tayfun; N/A; Demirkol, Mehmet Onur; Faculty Member; School of Medicine; 196946
    It is very crucial to determine Tg accurately and precisely in thyroid cancer cases. Although there are many studies on the detection of Tg in thyroid cases in the literature, there are no sufficient clinical studies examining many cases with different features by using RIA methodology. Here, a radiometric and chromatographic method has been studied for the first time to eliminate the interference from anti-Tg positive patients. In this paper, radioimmunoassay (RIA) and immunoradiometric (IRMA) techniques were used for the analysis of 302 sera collected from patients for Tg and TgAb quantification. By the RIA technique, a reliable result was obtained by calculating the real Tg value quantitatively in 41 patients showing TgAb positivity out of 208 patients. Our findings show that the RIA assay is the most suitable approach for detection of changeable (low or undetectable) Tg value and metastases detected by post-therapeutic imaging in early-stage DTC cases showing preoperative and postoperative TgAb positivity. The new immunoradiometric method allows the real (%) Tg value to be reached in a part of TgAb-positive DTC. Even if TgAb positive in the metastatic and nonmetastatic DTC patient group. This allows the accurate clinical follow-up of patients.
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    Diagnostic contribution of (18)F-FDG-PET/CT in fever of unknown origin
    (Elsevier Sci Ltd, 2014) Tokmak, Handan; N/A; Ergönül, Önder; Demirkol, Mehmet Onur; Çetiner, Mustafa; Ferhanoğlu, Ahmet Burhan; Faculty Member; Faculty Member; Faculty Member; Faculty Member; School of Medicine; School of Medicine; School of Medicine; School of Medicine; Koç University Hospital; 110398; 196946; N/A; 18320
    Objectives: Fever of unknown origin (FUO) remains one of the most compelling diagnostic issues in medicine. We aimed to evaluate the potential clinical contribution of 18-fluoro-2-deoxyglucose positron emission tomography/computed tomography (F-18-FDG-PET/CT) in the identification of the underlying cause of FUO. Methods: Fifty consecutive patients (27 men and 23 women; age range 16-88 years) with FUO based on the revised definition criteria were included in the study. A diagnostic protocol including biochemistry, histopathology, and microbiological tests was performed and the patients were followed up. FDG-PET was performed in 25 of the 50 patients (12 males and 13 females; age range 16-88 years) in order to determine the etiology of the patient's fever. PET-CT images were obtained with the Gemini Philips TF F-18-FDG-PET/CT camera after a 60-min 'standard uptake' period following an injection of a mean 330 MBq (range 290-370 MBq) intravenous F-18-FDG. Results: A total of 21 patients were available for analysis of the diagnostic contribution of PET/CT (two patients were undiagnosed and two had non-contributory PET/CT findings). F-18-FDG-PET/CT was able to precisely detect the cause of fever in 60% of the cases (n = 15). The accuracy, sensitivity, and specificity of this imaging modality were 90.5%, 93.8%, and 80%, respectively. Among the cases with a true-positive F-18-FDG-PET/CT finding (i.e., 15 cases), the identified underlying causes of FUO included localized infection (n = 7), non-infective inflammatory process (n = 5), and malignancy (n = 3). Conclusions: Further studies to confirm the high diagnostic yield of F-18-FDG-PET/CT observed in the present study would lend support to the inclusion of this imaging modality in the initial diagnostic workup of patients with suspected FUO. (C) 2013 The Authors. Published by Elsevier Ltd on behalf of International Society for Infectious Diseases. All rights reserved.
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    F-18-FDG PET/CT texture analysis of anthracotic lymph nodes detected with EBUS and comparison with cytological findings
    (Hellenic Soc Nuclear Medicine, 2022) N/A; N/A; Falay, Fikri Okan; Meriçöz, Çisel Aydın; Demirtaş, Elif; Bulutay, Pınar; Seymen, Hülya; Fırat, Pınar Arıkan; Demirkol, Mehmet Onur; Çağlayan, Benan Niku; Teaching Faculty; Teaching Faculty; Master Student; Teaching Faculty; Teaching Faculty; Faculty Member; Faculty Member; Faculty Member; School of Medicine; School of Medicine; Graduate School of Health Sciences; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; 246484; 162418; N/A; 133565; 350778; 207545; 196946; 230719
    Objective: Lymph node metastasis is the most important factor both in the selection of treatment since many alternatives have been created in recent years, and in the evaluation of prognosis in lung cancer. The most unpredictable cause of lymph node false positivity in fluorine-18-fluorodeoxyglucose (F-18-FDG) positron emission tomography/computed tomography(PET/CT) is anthracosis. The aim of this study is to compare F-18-FDG PET/CT texture information of anthracotic (ALN) and metastatic (MLN) lymph nodes, after reevaluation of the cytological samples obtained from anthracotic lymph nodes by EBUS-TBNA. Subjects and Methods: Ninety nine patients, 78 of whom had primary lung cancer were included in the study. Two hundred and three lymph nodes from 99 patients sampled by EBUS-TBNA and diagnosed cytologically as ALN or MLN were evaluated retrospectively. All ALN were classified as grades 1, 2 and 3 cytologically. Volume of interest (VOI) of 203 lymph nodes was re-drawn and maximum standardized uptake value (SUVmax), metabolic tumor volume (MN) and total lesion glycolysis (TLG) values were recorded. Results: There was a statistically significant difference in MTV and TLG values in MLN and all ALN grades. However, only grade 1-2 ALN could be differentiated from MLN with SUVmax, and no statistically significant difference was found in grade 3 ALN and MLN. Metabolic tumor volume and TLG values over 4.10cm(3) and 26.57 showed 60% and 59% sensitivity and 83% and 94 specificity respectively for the identification of MLN. Conclusions: The contribution of MTV and TLG values of F-18-FDG PET/CT to the differential diagnosis of ALN is much more valuable than SUVmax values, especially for grade 3 anthracosis. It was thought that cytological reporting of only grade 3 ALN could make a better contribution to the F-18-FDG PET/CT evaluation analysis.
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    [68Ga]Ga-antiCAD1: radiosynthesis and first imaging study on rats
    (Kafkas Univ, Veteriner Fakultesi Dergisi, 2018) Uçar, Burcu; Acar, Tayfun; Pelit Arayıcı, Pelin; Mustafaeva, Zeynep; Demirkol, Mehmet Onur; Faculty Member; School of Medicine; 196946
    Cadherins are cell adhesion and cell signaling molecules that provide the molecular link between each adjacent cells and have critical importance for the initiation and continuation of adhesion mechanism. N-cadherin expression provides a correlation between upregulation of N-cadherin and inflammation of the lesions. In this paper, we concentrated on the radiolabeling and evaluation of [Ga-68]Ga-AntiCAD1 agent as a potential candidate for in vivo PET/CT imaging of adhesions. The synthetic N-Ac-CHAVC-NH2 cyclic peptide sequence designed as (ADH-1)c containing the selective binding His-Ala-Val (HAV) motif based on the chimeric antigen receptor sequence acts as the N-cadherin antagonist. In our previous study, AntiCAD1 conjugate has been studied in detail which is in the process of publication. In this study, the conjugate was radiolabelled with the [Ga-68]Ga radionuclide eluted from the Ge-68/Ga-68 generator (IDB Holland). Radiochemical purity of [Ga-68]Ga-AntiCAD1 agent was analysed with TLC methods. The 'shake-flask' method was applied to determine lipophilicity of the agent by calculating the P distribution coefficient (logP=-2.69 +/- 0.54). The biodistribution of the agent was investigated using PET/CT on Wistar Albino rats. Significant uptake was found in liver, kidneys, spleen, salivary gland and targeted region with SUVmax-mean of 1.36, 1.96, 1.38, 1.16 and 2.14 respectively. The Pearson Factorial method is used to test the relationship between the targeted region and other body tissues, to measure the degree of this relationship (R=0.73). Radiolabelled agent was demonstrated to react specifically with N-cadherin in targeting of rat tissues.
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    Posttherapeutic critical organ dosimetry of extensive lu-177- PSMA inhibitor therapy with metastatic castration-resistant prostate cancer one center results
    (Lippincott Williams & Wilkins, 2020) Uçar, Burcu; Özkan, Ahu; Yarar, Yasemin Yıldız; N/A; N/A; N/A; Seymen, Hülya; Falay, Fikri Okan; Demirkol, Mehmet Onur; Teaching Faculty; Teaching Faculty; Faculty Member; School of Medicine; School of Medicine; School of Medicine; 350778; 246484; 196946
    Purpose: Lu-177-PSMA inhibitor peptide receptor radioligand therapy (RLT) is playing an increasing role in metastatic castration-resistant prostate cancer. We aimed to estimate the absorbed radiation doses for critical organs (eg, kidneys, parotid glands, submandibular glands, and lacrimal glands) of patients treated with 4 to 6 cycles by Lu-177-PSMA inhibitor RLT, retrospectively, and to evaluate the findings extensively in order to determine the critical organ radiation-absorbed limitations and the number of prospective RLT. Materials and Methods: A total of 51 cycles Lu-177-PSMA inhibitor RLT in 10 patients was analyzed. Therapies have been applied in 4 to 6 cycles with 8 to 10 weeks' intervals. Dosimetric estimates of kidneys, parotid glands, submandibular glands, and lacrimal glands have been calculated based on MIRD scheme pamphlet no. 16. Regions of interest were drawn with GE Xeleris Functional Imaging Workstation. OLINDA/EXM 1.1 simulation software was used to calculate radiation-absorbed doses. Results: Mean radiation-absorbed doses were 0.70 +/- 0.24 Gy/GBq for kidneys, 1.34 +/- 0.78 Gy/GBq for parotid glands, 0.94 +/- 0.45 Gy/GBq for submandibular glands, and 2.28 +/- 1.29 Gy/GBq for lacrimal glands. Conclusions: Due to the critical target organ risks and the optimal therapy doses, patient-specific dosimetry is a deterministic factor in radionuclide therapy. Even when the absorbed kidney doses were above the ICRP critical dose limits in patients who had 4 to 6 cycles of therapy, mortality due to nephrotoxicity has not been observed. Mild increased tolerated radiation dose is acceptable for the patient groups with very low survival rate.
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    The diagnostic efficacy of PET/CT in the initial evaluation of soft tissue sarcoma
    (Soc Nuclear Medicine Inc, 2014) Tokmak, Handan; N/A; Demirkol, Mehmet Onur; Faculty Member; School of Medicine; 196946
    N/A
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    Effect of prophylactic central neck dissection on the surgical outcomes in papillary thyroid cancer: experience in a single center
    (Springer, 2020) Colakoglu, Bulent; Aydin, Ozlem; Terzioglu, Tarik; Dereli, Dilek Yazıcı; Sezer, Havva; Alagöl, Faruk; Kurtoğlu, Burçin Sağlam; Kapran, Yersu; Demirkol, Mehmet Onur; Faculty Member; Teaching Faculty; Doctor; Teaching Faculty; Faculty Member; Faculty Member; School of Medicine; School of Medicine; N/A; School of Medicine; School of Medicine; School of Medicine; Koç University Hospital; 179659; 154807; N/A; 172911; 168101; 196946
    Purpose: Morbidity due to papillary thyroid carcinoma (PTC) is increased mostly due to lymph node (LN) metastases, which lead to reoperations and complications associated with these operations. The aim is to compare the outcomes of PTC having total thyroidectomy and prophylactic central lymph node dissection (TT + PCND) with patients having total thyroidectomy (TT) alone. Methods: This study is a retrospective cohort analysis of 358 PTC patients that were operated by a single surgeon in a single center. Data about the patients were extracted from the medical records. Results: Of the patient cohort, 258 patients had TT + PCND (42.5 ± 11.3 years) and 100 patients (41.2 ± 11.9 years) had only TT. Total number of LN extracted in the TT + PCND group was 8.1 ± 6.9. The mean number of metastatic LN were 2.2 ± 1.9. Percentage of patients that had RAI were less in the TT + PCND group compared to the TT group. Seven patients (2.7%) in the TT + PCND group and 19 (19.0%) in TT group had recurrent disease (p < 0.0001). Of the complications, only transient hypoparathyroidism was increased in TT + PCND group compared to TT group (26.7% vs 10%, p < 0.0001). Conclusion: TT + PCND performed by an experienced surgeon seems to decrease the number of LN recurrences, and the need for reoperations.
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    The utility of ga-68-psma pet/ct in poorly differentiated metastatic prostate cancer
    (Lippincott Williams & Wilkins, 2017) Uçar, Burcu; Sağlıcan, Yeşim; N/A; N/A; N/A; Demirkol, Mehmet Onur; Kiremit, Murat Can; Acar, Ömer; Faculty Member; Faculty Member; Faculty Member; School of Medicine; School of Medicine; School of Medicine; 196946; 222920; 237530
    We aimed to emphasize how useful PSMA PET/CT findings can be while trying to restage prostate cancer after radical prostatectomy in the presence of low prostate-specific antigen values. A 64-year-old man with pT3b N1 M0 Gleason 7 adenocarcinoma of the prostate presented 5 years postoperatively with a palpable axillary mass, whereas his prostate-specific antigen was 0.08 ng/mL. Conventional imaging studies and histopathologic findings of the axillary mass biopsy revealed inconclusive results. Ga-68-PSMA PET/CT demonstrated PSMA-positive metastatic lesions, the largest one being located in the right axilla. This finding confirmed metastatic poorly differentiated prostate cancer, and androgen deprivation therapy was initiated.
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    A new radio-theranostic agent candidate: synthesis and analysis of (ADH-1)c-EDTA conjugate
    (Parlar Scientific Publications (P S P), 2018) Ucar, Burcu; Acar, Tayfun; Pelit-Arayici, Pelin; Mustafaeva, Zeynep; N/A; Demirkol, Mehmet Onur; Faculty Member; School of Medicine; 196946
    The aim of this article are to synthesis, conjugate and characterize of (ADH-1)c (cell adhesion molecule) cyclic peptide sequence c(N-Ac-CHAVC-NH2) of N-CAD (N-cadherin) antagonist from a novel family of cyclic peptide antagonists. (ADH-l)c specifically targets and blocks N-cadherin, which can cause tumor vasculature disruption, inhibition of tumor cell growth, induction of tumor cell and endothelial cell apoptosis. (ADH-1)c is a cyclic pentapeptide vascular-disrupting agent with antineoplastic and antiangiogenic interactions. In peptide synthesis, microwave irradiation-assisted solid phase peptide synthesizer system with fluorenylmethyloxycarbonyl chemistry has been used to complete peptide sequences with high yields and smaller amount of racemization. macrocyclization was performed with ammonium acetate (5% w/v) following linear peptide synthesis. Conjugates of the cyclic peptide were synthesized with the EDTA chelator by application of water-soluble carbodiimide procedure. A wide range of HPLC (High Performance Liquid Chromatography) conditions for the purification of the peptides were examined by using an acetonitrile-based solvent system with CH2O2 as the ion pairing agent which has provided efficient purification. The purified peptide was characterized by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). The formation mechanism, physicochemical properties and electrical charges of the synthesized conjugate was characterized by Fluorescence Spectrophotometer, Zetasizer and LC-ESI-MS.
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    Cardiac angiosarcoma: Utility of [¹⁸F]fluorodeoxyglucose positron emission tomography-computed tomography in evaluation of residue, metastases, and treatment response
    (Dove Medical Press, 2014) Tokmak, Handan; Demir, Nurhan; Demirkol, Mehmet Onur; Faculty Member; School of Medicine; 196946
    Cardiac angiosarcomas are a rare form of malignancy. The majority of cases arise from the right atrium as mural masses. These tumors have extremely aggressive behavior, with early clinical symptoms that vary depending on location, size, and extent of the tumor. Most of these patients have a very short survival time. Surgical therapy is considered the best choice of therapy approach in cardiac angiosarcoma patients with nonmetastatic disease, even though the disease is rarely cured. Advanced diagnostic techniques facilitate accurate, noninvasive assessments of cardiac sarcomas. We report a case of a 62-year-old man with cardiac angiosarcoma who had multiple distant metastases that were revealed by [18F]fuorodeoxyglucose positron emission tomography-computed tomography imaging.