Tıp Fakültesi / Faculty of Medicine
Permanent URI for this collectionhttps://hdl.handle.net/11727/1403
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Item Diffusion-Weighted MRI and Optimal b-value For Characterization of Liver Lesions(2014) Kaya, Bilal; Koc, Zafer; https://orcid.org/0000-0002-8917-3375; https://orcid.org/0000-0003-0987-1980; 23982322; AAK-9366-2020; S-8384-2016Background: Diffusion-weighted imaging (DWI) is commonly used to distinguish between benign and malignant liver lesions. However, different b-values are recommended. Purpose: To determine the most suitable b-value in DWI for differentiation of benign and malignant liver lesions. Material and Methods: A total of 124 lesions in 89 consecutive patients (43 men, 46 women; age, mean +/- standard deviation, 58 +/- 14 years) with a pathological or radiological diagnosis of malignant or benign focal liver lesions after magnetic resonance imaging (MRI) were included in this study. Routine abdominal MRI and DWI were performed using seven b-values (0, 50, 200, 400, 600, 800, 1000 s/mm(2)). Lesions were analyzed for benignity/malignity using apparent diffusion coefficient (ADC) values with 10 b-value combinations and by measuring the lesion/normal parenchyma ADC ratio. Results: Mean ADC values were significantly different between malignant and benign lesions for all b-value combinations (P = 0.000). The best b-value combination was 0 and 800 (Az = 0.935). Using lower b-values such as 0 and 50 together with higher b-values >= 600 s/mm(2) was beneficial (Az = 0.928 and 0.927). Mean ADC values were approximately 13% (1-15%) higher in total when b = 0 and b = 50 s/mm(2) were included in multiple b-value combinations. Conclusion: In DWI, we recommend the use of b-values of 0 and 800 s/mm(2) as two b-values, or b = 0, 50, 600, 800, and 1000 s/mm(2) as multiple b-values for distinguishing between benign and malignant liver lesions. Mean ADC value is 13% higher in total by additional use of b = 0 and b = 50 s/mm(2) in multiple b-value combinations.Item Optimal b Value in Diffusion-Weighted Imaging for Differentiation of Abdominal Lesions(2014) Koc, Zafer; Erbay, Gurcan; https://orcid.org/0000-0003-0987-1980; https://orcid.org/0000-0002-1706-8680; 24115207; S-8384-2016; AAK-5370-2021Purpose: To explore the optimal b value in diffusion-weighted imaging (DWI) for differentiation of benign and malignant abdominal lesions. Materials and Methods: A total of 108 consecutive patients (age 60 +/- 12.5 years) with 127 pathologically confirmed diagnoses of abdominal lesions were included. Single-shot echoplanar imaging (SH-EPI) DWI (1.5T) with seven b values and eight apparent diffusion coefficient (ADC) maps were obtained. The lesions were analyzed visually on DWI and ADC maps for benignity/malignity using a 5-point scale and by measuring the ADC values and ADC lesion/normal parenchyma ADC ratio. ROC analysis was used to evaluate the diagnostic accuracy of ADC for differentiating between benign and malignant lesions. Pathology results were the reference standard. Results: Differentiation between malignant and benign lesions using visual scoring was successful at b values of 600 or higher (sensitivities, specificities, and accuracies were 100/93.8/92.5, 84.7/82.6/80.4, and 94.4/89.7/88.1, respectively, for b600, 800, and 1000). The mean ADC values of malignant lesions were significantly lower than those of benign lesions for all b-value combinations except b0 and 50 s/mm(2) (P = 0.032 for b0 and 50 s/mm(2), P = 0.000 for other b values). The best b-value combination was 0 and 600 s/mm(2) and multiple b2. The lesion/normal parenchymal ADC ratio for b600, b1000, and multiple b2 better distinguished between benign and malignant lesions. Conclusion: In DWI, the optimal b value is 600 s/mm(2); multiple b values of 600 s/mm(2) and higher are recommended to differentiate between benign and malignant abdominal lesions. The lesion ADC/normal parenchyma ADC ratio is more accurate than using lesion ADC only.Item Thorax CT Dose Reduction Based on Patient Features: Effect of Patient Characteristics on Image Quality and Effective Dose(2019) Koc, Gizem Gul; Koc, Zafer; Kaniyev, Tahir; Kokangul, Ali; https://orcid.org/0000-0003-0987-1980; 30908322; S-8384-2016Computed tomography (CT) radiation dose reduction is vital without compromising image quality. The aim was to determine the effects of patient characteristics on the received radiation dose and image quality in chest CT examinations and to be able to predict dose and image quality prior to scanning. Consecutive 230 patients underwent routine chest CT examinations were included. CT examination and patients input parameters were recorded for each patient. The effect of patients' demographics/anthropometrics on received dose and image quality was investigated by linear regression analysis. All parameters were evaluated using an artificial neural network (ANN). Of all parameters, patient demographics/anthropometrics were found to be 98% effective in calculating dose reduction. Using ANN on 60 new patients was more than 90% accurate for output parameters and 91% for image quality. Patient characteristics have a significant impact on radiation dose and image quality. Dose and image quality can be determined before CT. This will allow setting the most appropriate scanning parameters before the CT scan.Item Internal Comparison Standard for Abdominal Diffusion-Weighted Imaging(2017) Koc, Zafer; Erbay, Gurcan; Karadeli, Elif; 0000-0002-1706-8680; 0000-0002-0352-8818; 0000-0003-0987-1980; 27956463; AAK-5370-2021; AAK-5399-2021; S-8384-2016Background: Standards for abdominal diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC) measurements, and analysis are required for reproducibility. Purpose: To identify optimal internal comparison standards for DWI to normalize the measured ADC for increased accuracy of differentiating malignant and benign abdominal lesions. Material and Methods: We retrospectively studied 97 lesions (89 patients; age, 57 +/- 13 years) with histopathologically confirmed abdominal disease. Seven normal body parts/contents (normal parenchyma, spleen, kidney, gallbladder bile, paraspinal muscle, spinal cord, and cerebrospinal fluid [CSF]) were assessed as internal references for possible use as comparison standards. Three observers performed ADC measurements. Statistical analyses included interclass correlation coefficients (ICCs), Mann-Whitney and Kruskal-Wallis tests, and coefficient of variation (CV). ROC analyses were performed to assess diagnostic accuracy of lesion ADC and normalized ADC for differentiating lesions. Pathology results were the reference standard. Results: Mean and normalized ADCs were significantly lower for malignant lesions than for benign lesions (P< 0.001). ICC was excellent for all internal references. Gallbladder had the lowest CV. Receiver operating characteristic (ROC) analyses showed that normalized ADCs obtained using normal parenchyma were better than lesion ADCs for differentiating malignant and benign abdominal lesions (area under the curve [AUC], 0.808 and 0.756, respectively). The normalized ADCs obtained using CSF shows higher accuracy than lesion ADCs (0.80 and 0.76, respectively) for differentiating between malignant and benign abdominal lesions. Conclusion: The normal parenchyma from a lesion-detected organ can be used as an internal comparison standard for DWI. CSF can be used as a generalizable in plane reference standard.Item Utility of Diffusion-Weighted MRI to Detect Changes in Liver Diffusion in Benign and Malignant Distal Bile Duct Obstruction: The Influence of Choice of b-Values(2016) Karan, Belgin; Erbay, Gurcan; Koc, Zafer; Pourbagher, Aysin; Yildirim, Sedat; Agildere, Ahmet Muhtesem; 0000-0003-0987-1980; 0000-0002-5735-4315; 0000-0002-1706-8680; 0000-0003-4223-7017; 27592163; S-8384-2016; AAF-4610-2019; AAK-5370-2021; AAB-5802-2020Purpose: The study sought to evaluate the potential of diffusion-weighted magnetic resonance imaging to detect changes in liver diffusion in benign and malignant distal bile duct obstruction and to investigate the effect of the choice of b-values on apparent diffusion coefficient (ADC). Methods: Diffusion-weighted imaging was acquired with b-values of 200, 600, 800, and 1000 s/mm(2). ADC values were obtained in 4 segments of the liver. The mean ADC values of 16 patients with malignant distal bile duct obstruction, 14 patients with benign distal bile duct obstruction, and a control group of 16 healthy patients were compared. Results: Mean ADC values for 4 liver segments were lower in the malignant obstruction group than in the benign obstruction and control groups using b = 200 s/mm(2) (P < .05). Mean ADC values of the left lobe medial and lateral segments were lower in the malignant obstruction group than in the benign obstructive and control groups using b = 600 s/mm2 (P < .05). Mean ADC values of the right lobe posterior segment were lower in the malignant and benign obstruction groups than in the control group using b = 1000 s/mm(2) (P < .05). Using b = 800 s/mm(2), ADC values of all 4 liver segments in each group were not significantly different (P > .05). There were no correlations between the ADC values of liver segments and liver function tests. Conclusion: Measurement of ADC shows good potential for detecting changes in liver diffusion in patients with distal bile duct obstruction. Calculated ADC values were affected by the choice of b-values.Item Predicting Tumor Recurrence in Patients with Cervical Carcinoma Treated with Definitive Chemoradiotherapy: Value Of Quantitative Histogram Analysis On Diffusion-Weighted MR Images(2017) Erbay, Gurcan; Onal, Cem; Karadeli, Elif; Guler, Ozan C.; Arica, Sami; Koc, Zafer; https://orcid.org/0000-0002-1706-8680; https://orcid.org/0000-0002-0352-8818; https://orcid.org/0000-0001-6908-3412; https://orcid.org/0000-0003-0987-1980; 27445314; AAK-5370-2021; HOC-5611-2023; AAK-5399-2021; AAC-5654-2020; S-8384-2016Background: Further research is required for evaluating the use of ADC histogram analysis in more advanced stages of cervical cancer treated with definitive chemoradiotherapy (CRT). Purpose: To investigate the utility of apparent diffusion coefficient (ADC) histogram derived from diffusion-weighted magnetic resonance images in cervical cancer patients treated with definitive CRT. Material and Methods: The clinical and radiological data of 50 patients with histologically proven cervical squamous cell carcinoma treated with definitive CRT were retrospectively analyzed. The impact of clinicopathological factors and ADC histogram parameters on prognostic factors and treatment outcomes was assessed. Results: The mean and median ADC values for the cohort were 1.043 +/- 0.135 x 10(-3) mm(2)/s and 1.018 x 10(-3) mm(2)/s (range, 0.787-1.443 x 10(-3) mm(2)/s). The mean ADC was significantly lower for patients with advanced stage (>= IIB) or lymph node metastasis compared with patients with stage < IIB or no lymph node metastasis. The mean ADC, 75th percentile ADC (ADC75), 90th percentile ADC (ADC90), and 95th percentile ADC (ADC95) were significantly lower in patients with tumor recurrence compared with patients without recurrence. In multivariate analysis, tumor size, ADC75 and ADC95 were independent prognostic factors for both overall survival and disease-free survival. Conclusion: ADC histogram parameters could be markers for disease recurrence and for predicting survival outcomes. ADC75, ADC90, and ADC95 of the primary tumor were significant predictors of disease recurrence in cervical cancer patients treated with definitive CRT.Item Utility of Diffusion Weighted Magnetic Resonance Imaging with Multiple B Values in Evaluation of Pancreatic Malignant and Benign Lesions and Pancreatitis(2018) Karadeli, Elif; Erbay, Gurcan; Parlakgumus, Alper; Koc, Zafer; https://orcid.org/0000-0002-0352-8818; https://orcid.org/0000-0002-1706-8680; https://orcid.org/0000-0003-0987-1980; 29394967; AAK-5399-2021; AAK-5370-2021; S-8384-2016Objective: To determine the feasibility of diffusion-weighted imaging in evaluation of pancreatic lesions and in differentiation of benign from malignant lesions. Study Design: Descriptive study. Place and Duration of Study: Baskent University Adana Teaching and Research Center, Adana, Turkey, between September 2013 and May 2015. Methodology: Forty-three lesions [pancreas adenocarcinoma (n = 25)], pancreatitis (n = 10), benign lesion (n = 8)] were utilized with diffusion-weighted magnetic resonance imaging with multiple b-values. Different ADC maps of diffusion weighted images by using b-values were acquired. Results: The median ADC at all b values for malignant lesions was significantly different from that for benign lesions (p < 0.001). When ADCs at all b values were compared between benign lesions/normal parenchyma and malignant lesions/normal parenchyma, there was a significant statistical difference in all b values between benign and malignant lesions except at b 50 and b 200 (p<0.05). The lesion/normal parenchyma ADC ratio for b 600 value (AUC=0.804) was more effective than the lesion ADC for b 600 value (AUC=0.766) in differentiation of benign and malignant lesions. The specificity and sensitivity of the lesion/normal parenchyma ADC ratio were higher than those of ADC values of lesions. When the ADC was compared between benign lesions and pancreatitis, a significant difference was found at all b values (p<0.001). There was not a statistically significant difference between the ADC for pancreatitis and that for malignant lesions at any b value combinations (p>0.05). Conclusion: Diffusion-weighted magnetic resonance images can be helpful in differentiation of pancreatic carcinoma and benign lesions. Lesion ADC / normal parenchyma ADC ratios are more important than lesion ADC values in assessment of pancreatic lesions.Item Prognostic values of ADC(mean) and SUVmax of the primary tumour in cervical cancer patients treated with definitive chemoradiotherapy(2019) Yildirim, Berna Akkus; Onal, Cem; Erbay, Gurcan; Guler, Ozan Cem; Karadeli, Elif; Reyhan, Mehmet; Koc, Zafer; 0000-0002-2742-9021; 0000-0003-0987-1980; 30354907; D-5195-2014; S-8384-2016We analysed the correlation of F-18-fluorodeoxyglucose uptake into primary tumours using the maximum standardised uptake value (SUVmax) and the mean apparent diffusion coefficient (ADC(mean)) values in magnetic resonance imaging (MRI) with the clinical and pathological factors in patients with cervical cancer who were treated with concurrent chemoradiotherapy. The patients were stratified according to the primary tumour pre-treatment ADC(mean) and SUVmax cut-off values. There were significant correlations between the SUVmax of the primary tumour and tumour size, and the treatment response. The correlation between the ADC(mean) and FIGO stage, tumour size, and the lymph node metastasis was significant. The SUVmax was significantly and inversely correlated with the ADC(mean) for cervical cancer (r = -0.44, p <.001). In the multivariate analysis, the primary tumour ADC(mean), treatment response and the lymph node metastasis emerged as significant independent predictors of both OS and DFS, and of the primary tumour SUVmax for DFS. Tumour size has a borderline significance for OS. High SUVmax and low ADC(mean) of the primary tumour are important predictive factors for identifying high-risk patients with cervical cancer who are treated with definitive chemoradiotherapy. These results point to a future role for the diffusion-weighted MRI and for F-18-fluorodeoxyglucose positron emission tomography, not only in the staging of cervical cancer but as an aid in the selection of an adjuvant treatment regimen after chemoradiotherapy for individual patients.