44 results on '"Tsantis S"'
Search Results
2. Optical coherence tomography provides images similar to histology and allows the performance of extensive measurements of drug-eluting metal stents in animal ureters
- Author
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Kallidonis, P., Kagadis, G. C., Kitrou, P., Tsamandas, A., Kyriazis, I., Georgiopoulos, I., Karnabatidis, D., Tsantis, S., Liourdi, D., Al-Aown, A., and Liatsikos, E.
- Published
- 2014
- Full Text
- View/download PDF
3. Inter-scale wavelet analysis for speckle reduction in thyroid ultrasound images
- Author
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Tsantis, S., Dimitropoulos, N., Ioannidou, M., Cavouras, D., and Nikiforidis, G.
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- 2007
- Full Text
- View/download PDF
4. A hybrid multi-scale model for thyroid nodule boundary detection on ultrasound images
- Author
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Tsantis, S., Dimitropoulos, N., Cavouras, D., and Nikiforidis, G.
- Published
- 2006
- Full Text
- View/download PDF
5. 2D perfusion DSA with an open-source, semi-automated, color-coded software for the quantification of foot perfusion following infrapopliteal angioplasty: a feasibility study
- Author
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Kagadis, G.C. Tsantis, S. Gatos, I. Spiliopoulos, S. Katsanos, K. Karnabatidis, D.
- Abstract
Background: Foot perfusion has been recently implemented as a new tool for optimizing outcomes of peripheral endovascular procedures. A custom-made, two-dimensional perfusion digital subtraction angiography (PDSA) algorithm has been implemented to quantify outcomes of endovascular treatment of critical limb ischemia (CLI), assist intra-procedural decision-making, and enhance clinical outcomes. Methods: The study was approved by the Hospital’s Ethics Committee. This prospective, single-center study included seven consecutive patients scheduled to undergo infrapopliteal endovascular treatment of CLI. Perfusion blood volume (PBV), mean transit time (MTT), and perfusion blood flow (PBF) maps were extracted by analyzing time-intensity curves and signal intensity on the perfused vessel mask. Mean values calculated from user-specified regions of interest (ROIs) on perfusion maps were employed to evaluate pre- and post-endovascular treatment condition. Measurements were performed immediately after final PDSA. Results: In total, five patients (aged 54 ± 16 years, mean ± standard deviation) were analyzed, as two patients were excluded due to significant motion artifacts. Post-procedural MTT presented a mean decrease of 19.1% for all patients and increased only in 1 of 5 patients, demonstrating in 4/5 patients an increase in tissue perfusion after revascularization. Overall mean PBF and PBV values were also analogously increased following revascularization (446% and 69.5% mean, respectively) and in the majority of selected ROIs (13/15 and 12/15 ROIs, respectively). Conclusions: Quantification of infrapopliteal angioplasty outcomes using this newly proposed, custom-made, intra-procedural PDSA algorithm was performed using PBV, MTT, and PBF maps. Further studies are required to determine its role in peripheral endovascular procedures (ClinicalTrials.gov Identifier: NCT04356092). © 2020, The Author(s).
- Published
- 2020
6. Deep learning networks on chronic liver disease assessment with fine-tuning of shear wave elastography image sequences
- Author
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Kagadis, G.C. Drazinos, P. Gatos, I. Tsantis, S. Papadimitroulas, P. Spiliopoulos, S. Karnabatidis, D. Theotokas, I. Zoumpoulis, P. Hazle, J.D.
- Abstract
Chronic liver disease (CLD) is currently one of the major causes of death worldwide. If not treated, it may lead to cirrhosis, hepatic carcinoma and death. Ultrasound (US) shear wave elastography (SWE) is a relatively new, popular, non-invasive technique among radiologists. Although many studies have been published validating the SWE technique either in a clinical setting, or by applying machine learning on SWE elastograms, minimal work has been done on comparing the performance of popular pre-trained deep learning networks on CLD assessment. Currently available literature reports suggest technical advancements on specific deep learning structures, with specific inputs and usually on a limited CLD fibrosis stage class group, with limited comparison on competitive deep learning schemes fed with different input types. The aim of the present study is to compare some popular deep learning pre-trained networks using temporally stable and full elastograms, with or without augmentation as well as propose suitable deep learning schemes for CLD diagnosis and progress assessment. 200 liver biopsy validated patients with CLD, underwent US SWE examination. Four images from the same liver area were saved to extract elastograms and processed to exclude areas that were temporally unstable. Then, full and temporally stable masked elastograms for each patient were separately fed into GoogLeNet, AlexNet, VGG16, ResNet50 and DenseNet201 with and without augmentation. The networks were tested for differentiation of CLD stages in seven classification schemes over 30 repetitions using liver biopsy as the reference. All networks achieved maximum mean accuracies ranging from 87.2%-97.4% and area under the receiver operating characteristic curves (AUCs) ranging from 0.979-0.990 while the radiologists had AUCs ranging from 0.800-0.870. ResNet50 and DenseNet201 had better average performance than the other networks. The use of the temporal stability mask led to improved performance on about 50% of inputs and network combinations while augmentation led to lower performance for all networks. These findings can provide potential networks with higher accuracy and better setting in the CLD diagnosis and progress assessment. A larger data set would help identify the best network and settings for CLD assessment in clinical practice. © 2020 Institute of Physics and Engineering in Medicine.
- Published
- 2020
7. Temporal stability assessment in shear wave elasticity images validated by deep learning neural network for chronic liver disease fibrosis stage assessment
- Author
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Gatos, I. Tsantis, S. Spiliopoulos, S. Karnabatidis, D. Theotokas, I. Zoumpoulis, P. Loupas, T. Hazle, J.D. Kagadis, G.C.
- Abstract
Purpose: To automatically detect and isolate areas of low and high stiffness temporal stability in shear wave elastography (SWE) image sequences and define their impact in chronic liver disease (CLD) diagnosis improvement by means of clinical examination study and deep learning algorithm employing convolutional neural networks (CNNs). Materials and Methods: Two hundred SWE image sequences from 88 healthy individuals (F0 fibrosis stage) and 112 CLD patients (46 with mild fibrosis (F1), 16 with significant fibrosis (F2), 22 with severe fibrosis (F3), and 28 with cirrhosis (F4)) were analyzed to detect temporal stiffness stability between frames. An inverse Red, Green, Blue (RGB) colormap-to-stiffness process was performed for each image sequence, followed by a wavelet transform and fuzzy c-means clustering algorithm. This resulted in a binary mask depicting areas of high and low stiffness temporal stability. The mask was then applied to the first image of the SWE sequence, and the derived, masked SWE image was used to estimate its impact in standard clinical examination and CNN classification. Regarding the impact of the masked SWE image in clinical examination, one measurement by two radiologists was performed in each SWE image and two in the corresponding masked image measuring areas with high and low stiffness temporal stability. Then, stiffness stability parameters, interobserver variability evaluation and diagnostic performance by means of ROC analysis were assessed. The masked and unmasked sets of SWE images were fed into a CNN scheme for comparison. Results: The clinical impact evaluation study showed that the masked SWE images decreased the interobserver variability of the radiologists’ measurements in the high stiffness temporal stability areas (interclass correlation coefficient (ICC) = 0.92) compared to the corresponding unmasked ones (ICC = 0.76). In terms of diagnostic accuracy, measurements in the high-stability areas of the masked SWE images (area-under-the-curve (AUC) ranging from 0.800 to 0.851) performed similarly to those in the unmasked SWE images (AUC ranging from 0.805 to 0.893). Regarding the measurements in the low stiffness temporal stability areas of the masked SWE images, results for interobserver variability (ICC = 0.63) and diagnostic accuracy (AUC ranging from 0.622 to 0.791) were poor. Regarding the CNN classification, the masked SWE images showed improved accuracy (ranging from 82.5% to 95.5%) compared to the unmasked ones (ranging from 79.5% to 93.2%) for various CLD stage combinations. Conclusion: Our detection algorithm excludes unreliable areas in SWE images, reduces interobserver variability, and augments CNN's accuracy scores for many combinations of fibrosis stages. © 2019 American Association of Physicists in Medicine
- Published
- 2019
8. A Machine-Learning Algorithm Toward Color Analysis for Chronic Liver Disease Classification, Employing Ultrasound Shear Wave Elastography
- Author
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Gatos, I. Tsantis, S. Spiliopoulos, S. Karnabatidis, D. Theotokas, I. Zoumpoulis, P. Loupas, T. Hazle, J.D. Kagadis, G.C.
- Abstract
The purpose of the present study was to employ a computer-aided diagnosis system that classifies chronic liver disease (CLD) using ultrasound shear wave elastography (SWE) imaging, with a stiffness value-clustering and machine-learning algorithm. A clinical data set of 126 patients (56 healthy controls, 70 with CLD) was analyzed. First, an RGB-to-stiffness inverse mapping technique was employed. A five-cluster segmentation was then performed associating corresponding different-color regions with certain stiffness value ranges acquired from the SWE manufacturer-provided color bar. Subsequently, 35 features (7 for each cluster), indicative of physical characteristics existing within the SWE image, were extracted. A stepwise regression analysis toward feature reduction was used to derive a reduced feature subset that was fed into the support vector machine classification algorithm to classify CLD from healthy cases. The highest accuracy in classification of healthy to CLD subject discrimination from the support vector machine model was 87.3% with sensitivity and specificity values of 93.5% and 81.2%, respectively. Receiver operating characteristic curve analysis gave an area under the curve value of 0.87 (confidence interval: 0.77–0.92). A machine-learning algorithm that quantifies color information in terms of stiffness values from SWE images and discriminates CLD from healthy cases is introduced. New objective parameters and criteria for CLD diagnosis employing SWE images provided by the present study can be considered an important step toward color-based interpretation, and could assist radiologists’ diagnostic performance on a daily basis after being installed in a PC and employed retrospectively, immediately after the examination. © 2017 World Federation for Ultrasound in Medicine & Biology
- Published
- 2017
9. Focal liver lesions segmentation and classification in nonenhanced T2-weighted MRI
- Author
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Gatos, I. Tsantis, S. Karamesini, M. Spiliopoulos, S. Karnabatidis, D. Hazle, J.D. Kagadis, G.C.
- Abstract
Purpose: To automatically segment and classify focal liver lesions (FLLs) on nonenhanced T2-weighted magnetic resonance imaging (MRI) scans using a computer-aided diagnosis (CAD) algorithm. Methods: 71 FLLs (30 benign lesions, 19 hepatocellular carcinomas, and 22 metastases) on T2-weighted MRI scans were delineated by the proposed CAD scheme. The FLL segmentation procedure involved wavelet multiscale analysis to extract accurate edge information and mean intensity values for consecutive edges computed using horizontal and vertical analysis that were fed into the subsequent fuzzy C-means algorithm for final FLL border extraction. Texture information for each extracted lesion was derived using 42 first- and second-order textural features from grayscale value histogram, co-occurrence, and run-length matrices. Twelve morphological features were also extracted to capture any shape differentiation between classes. Feature selection was performed with stepwise multilinear regression analysis that led to a reduced feature subset. A multiclass Probabilistic Neural Network (PNN) classifier was then designed and used for lesion classification. PNN model evaluation was performed using the leave-one-out (LOO) method and receiver operating characteristic (ROC) curve analysis. Results: The mean overlap between the automatically segmented FLLs and the manual segmentations performed by radiologists was 0.91 ± 0.12. The highest classification accuracies in the PNN model for the benign, hepatocellular carcinoma, and metastatic FLLs were 94.1%, 91.4%, and 94.1%, respectively, with sensitivity/specificity values of 90%/97.3%, 89.5%/92.2%, and 90.9%/95.6% respectively. The overall classification accuracy for the proposed system was 90.1%. Conclusions: Our diagnostic system using sophisticated FLL segmentation and classification algorithms is a powerful tool for routine clinical MRI-based liver evaluation and can be a supplement to contrast-enhanced MRI to prevent unnecessary invasive procedures. © 2017 American Association of Physicists in Medicine.
- Published
- 2017
10. A new computer aided diagnosis system for evaluation of chronic liver disease with ultrasound shear wave elastography imaging
- Author
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Gatos, I. Tsantis, S. Spiliopoulos, S. Karnabatidis, D. Theotokas, I. Zoumpoulis, P. Loupas, T. Hazle, J.D. Kagadis, G.C.
- Abstract
Purpose: Classify chronic liver disease (CLD) from ultrasound shear-wave elastography (SWE) imaging by means of a computer aided diagnosis (CAD) system. Methods: The proposed algorithm employs an inverse mapping technique (red-green-blue to stiffness) to quantify 85 SWE images (54 healthy and 31 with CLD). Texture analysis is then applied involving the automatic calculation of 330 first and second order textural features from every transformed stiffness value map to determine functional features that characterize liver elasticity and describe liver condition for all available stages. Consequently, a stepwise regression analysis feature selection procedure is utilized toward a reduced feature subset that is fed into the support vector machines (SVMs) classification algorithm in the design of the CAD system. Results: With regard to the mapping procedure accuracy, the stiffness map values had an average difference of 0.01?0.001 kPa compared to the quantification results derived from the color-box provided by the built-in software of the ultrasound system. Highest classification accuracy from the SVM model was 87.0% with sensitivity and specificity values of 83.3% and 89.1%, respectively. Receiver operating characteristic curves analysis gave an area under the curve value of 0.85 with [0.770.89] confidence interval. Conclusions: The proposed CAD system employing color to stiffness mapping and classification algorithms offered superior results, comparing the already published clinical studies. It could prove to be of value to physicians improving the diagnostic accuracy of CLD and can be employed as a second opinion tool for avoiding unnecessary invasive procedures. © 2016 Am. Assoc. Phys. Med.
- Published
- 2016
11. TU‐H‐CAMPUS‐IeP3‐05: Computer Aided Diagnosis Employing Automatically Segmented Color‐Specific Regions in Ultrasound Shear Wave Elastography for the Assessment of Chronic Liver Disease
- Author
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Gatos, I., primary, Tsantis, S., additional, and Kagadis, G.C., additional
- Published
- 2016
- Full Text
- View/download PDF
12. Development of a Support Vector Machine - Based Image Analysis System for Focal Liver Lesions Classification in Magnetic Resonance Images
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Gatos, I, primary, Tsantis, S, additional, Karamesini, M, additional, Skouroliakou, A, additional, and Kagadis, G, additional
- Published
- 2015
- Full Text
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13. SU-E-U-01: Automatic Quantitative Analysis of Chronic Liver Disease Employing Shear Wave Ultrasound Elastography
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Gatos, I, primary, Tsantis, S, additional, Skouroliakou, A, additional, Theotokas, I, additional, Zoumpoulis, P, additional, and Kagadis, G, additional
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- 2015
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14. IMMEDIATE IMPLANT PLACEMENT BY USING BONE-ALBUMIN ALLOGRAFT AND CONCENTRATED GROWTH FACTORS (CGFS): PRELIMINARY RESULTS OF A PILOT STUDY.
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INCHINGOLO, F., BALLINI, A., GEORGAKOPOULOS, P. G., INCHINGOLO, A. D., TSANTIS, S., DE VITO, D., CANTORE, S., GEORGAKOPOULOS, I. P., and DIPALMA, G.
- Subjects
DENTAL implants ,HOMOGRAFTS ,GROWTH factors - Abstract
The provision of structural base and soft tissue support in dental implantology still remains a complex task. In the present study a new technique was introduced, which employs Bone-Albumin allograft and Concentrated Growth Factors (CGFs) integrated in a 1-stage immediate implant placement. The allograft is transformed from cubic to cylindrical shape by means of bone cutting forceps, followed by central osteotomy for screwing the implant within the allograft. The implant/graft combination promotes graft union, increases dental stability and minimizes graft resorption. The successful outcome of the proposed technique is evaluated by means of clinical and radiographic data. In conclusion, the proposed method provides a successful immediate dental implantation in terms of osseo-integration, stability and aesthetic results. [ABSTRACT FROM AUTHOR]
- Published
- 2018
15. Measurement of extra low frequency ELF electromagnetic fields in indoor working areas
- Author
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Skouroliakou, A., primary, Kontaxis, P., additional, Anagnostakis, S., additional, Triantopoulos, S., additional, and Tsantis, S., additional
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- 2014
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16. SU-E-U-07: An Edge-Preserving Markov-Random-Fields Model for Speckle Removal in Ultrasound Images
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Tsantis, S, primary, Katsakiori, P, additional, Karnabatidis, D, additional, Skouroliakou, A, additional, Mihailidis, D, additional, and Kagadis, GC, additional
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- 2013
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17. SU‐E‐I‐90: Fast and Robust Algorithm Towards Vessel Lumen and Stent Strut Detection in Optical Coherence Tomography
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Mandelias, K, primary, Tsantis, S, additional, Karnabatidis, D, additional, Katsakiori, P, additional, Mihailidis, D, additional, Nikiforidis, G, additional, and Kagadis, GC, additional
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- 2012
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18. SU-E-I-01: Quantification of Vascular Networks with the Aid of OCT in Order to Evaluate Re-Endothelialization after Peripheral Angioplasty
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Kagadis, GC, primary, Tsantis, S, additional, Bourantas, G, additional, Katsanos, K, additional, Karnabatidis, D, additional, Mihailidis, D, additional, and Nikiforidis, G, additional
- Published
- 2011
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19. Texture based evaluation of osseo integration of oral implants in dental panoramic radiography
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Georgakopoulos, I., primary, Tsantis, S., additional, Korfiatis, P., additional, Costaridou, L., additional, Petsas, T., additional, and Panayiotakis, G., additional
- Published
- 2009
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20. O.2.3 - A DEEP LEARNING DIAGNOSTIC PERFORMANCE COMPARISON ON NON-ALCOHOLIC FATTY LIVER DISEASE PATIENTS USING ULTRASOUND B-MODE IMAGES AND LIVER BIOPSY AS 'GOLD STANDARD'.
- Author
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Gatos, I., Drazinos, P., Tsantis, S., Zoumpoulis, P., Theotokas, I., and Kagadis, G.
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- 2022
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21. COMPUTER-AIDED CHARACTERIZATION OF THYROID NODULES BY IMAGE ANALYSIS METHODS
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TSANTIS, S., primary, KALATZIS, I., additional, PILIOURAS, N., additional, CAVOURAS, D., additional, DIMITROPOULOS, N., additional, and NIKIFORIDIS, G., additional
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- 2003
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22. DENOISING SONOGRAPHIC IMAGES OF THYROID NODULES VIA SINGULARITY DETECTION EMPLOYING THE WAVELET TRANSFORM MODULUS MAXIMA
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TSANTIS, S., primary, CAVOURAS, D., additional, DIMITROPOULOS, N., additional, and NIKIFORIDIS, G., additional
- Published
- 2003
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23. RADIATION DETECTION EFFICIENCY EVALUATION OF YAP: CE SCINTILLATOR BY MONTE-CARLO METHODS
- Author
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NIKOLOPOULOS, D., primary, LIAPARINOS, P., additional, TSANTIS, S., additional, CAVOURAS, D., additional, KANDARAKIS, I., additional, and PANAYIOTAKIS, G., additional
- Published
- 2003
- Full Text
- View/download PDF
24. Computer-based quantification of an atraumatic sinus augmentation technique using CBCT
- Author
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Inchingolo, F., Dipalma, G., Paduanelli, G., Oliveira, L. A., Inchingolo, A. M., Georgakopoulos, P. I., Inchingolo, A. D., Giuseppina Malcangi, Athanasiou, E., Fotopoulou, E., Tsantis, S., Georgakopoulos, I. P., Diem Kieu, N. C., Gargiulo Isacco, C., Ballini, A., Goker, F., Mortellaro, C., Greco Lucchina, A., and Del Fabbro, M.
25. Immediate implant placement by using bone-albumin allograft and concentrated growth factors (CGFS): Preliminary results of a pilot study
- Author
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Inchingolo, F., Ballini, A., Georgakopoulos, P. G., Inchingolo, A. D., Tsantis, S., Vito, D., Stefania Cantore, Georgakopoulos, I. P., and Dipalma, G.
26. Venous drug-eluting vs. bare-metal Stenting: An experimental animal study using frequency- domain optical coherence tomography
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Kitrou, P. M., Stavros Spiliopoulos, Katsanos, K., Tsantis, S., Diamantopoulos, A., Kallidonis, P., Kyriakopoulou, M., Kagadis, G. C., Karnabatidis, D., and Siablis, D.
27. An improved algorithm for foetal heart rate baseline in CTG.
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Abel, E., Tsantis, S., Mires, G., and Taylor, G.
- Published
- 1999
- Full Text
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28. Comparison of deep learning schemes in grading non-alcoholic fatty liver disease using B-mode ultrasound hepatorenal window images with liver biopsy as the gold standard.
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Drazinos P, Gatos I, Katsakiori PF, Tsantis S, Syrmas E, Spiliopoulos S, Karnabatidis D, Theotokas I, Zoumpoulis P, Hazle JD, and Kagadis GC
- Subjects
- Humans, Male, Middle Aged, Biopsy, Female, Image Processing, Computer-Assisted methods, Adult, Reference Standards, Kidney diagnostic imaging, Kidney pathology, ROC Curve, Aged, Deep Learning, Non-alcoholic Fatty Liver Disease diagnostic imaging, Non-alcoholic Fatty Liver Disease pathology, Liver diagnostic imaging, Liver pathology, Ultrasonography
- Abstract
Background/introduction: To evaluate the performance of pre-trained deep learning schemes (DLS) in hepatic steatosis (HS) grading of Non-Alcoholic Fatty Liver Disease (NAFLD) patients, using as input B-mode US images containing right kidney (RK) cortex and liver parenchyma (LP) areas indicated by an expert radiologist., Methods: A total of 112 consecutively enrolled, biopsy-validated NAFLD patients underwent a regular abdominal B-mode US examination. For each patient, a radiologist obtained a B-mode US image containing RK cortex and LP and marked a point between the RK and LP, around which a window was automatically cropped. The cropped image dataset was augmented using up-sampling, and the augmented and non-augmented datasets were sorted by HS grade. Each dataset was split into training (70%) and testing (30%), and fed separately as input to InceptionV3, MobileNetV2, ResNet50, DenseNet201, and NASNetMobile pre-trained DLS. A receiver operating characteristic (ROC) analysis of hepatorenal index (HRI) measurements by the radiologist from the same cropped images was used for comparison with the performance of the DLS., Results: With the test data, the DLS reached 89.15 %-93.75 % accuracy when comparing HS grades S0-S1 vs. S2-S3 and 79.69 %-91.21 % accuracy for S0 vs. S1 vs. S2 vs. S3 with augmentation, and 80.45-82.73 % accuracy when comparing S0-S1 vs. S2-S3 and 59.54 %-63.64 % accuracy for S0 vs. S1 vs. S2 vs. S3 without augmentation. The performance of radiologists' HRI measurement after ROC analysis was 82 %, 91.56 %, and 96.19 % for thresholds of S ≥ S1, S ≥ S2, and S = S3, respectively., Conclusion: All networks achieved high performance in HS assessment. DenseNet201 with the use of augmented data seems to be the most efficient supplementary tool for NAFLD diagnosis and grading., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Associazione Italiana di Fisica Medica e Sanitaria. Published by Elsevier Ltd. All rights reserved.)
- Published
- 2025
- Full Text
- View/download PDF
29. Deep learning networks on chronic liver disease assessment with fine-tuning of shear wave elastography image sequences.
- Author
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Kagadis GC, Drazinos P, Gatos I, Tsantis S, Papadimitroulas P, Spiliopoulos S, Karnabatidis D, Theotokas I, Zoumpoulis P, and Hazle JD
- Subjects
- Biopsy, Chronic Disease, Female, Humans, Liver Diseases pathology, Male, Middle Aged, ROC Curve, Deep Learning, Elasticity Imaging Techniques, Image Processing, Computer-Assisted methods, Liver Diseases diagnostic imaging
- Abstract
Chronic liver disease (CLD) is currently one of the major causes of death worldwide. If not treated, it may lead to cirrhosis, hepatic carcinoma and death. Ultrasound (US) shear wave elastography (SWE) is a relatively new, popular, non-invasive technique among radiologists. Although many studies have been published validating the SWE technique either in a clinical setting, or by applying machine learning on SWE elastograms, minimal work has been done on comparing the performance of popular pre-trained deep learning networks on CLD assessment. Currently available literature reports suggest technical advancements on specific deep learning structures, with specific inputs and usually on a limited CLD fibrosis stage class group, with limited comparison on competitive deep learning schemes fed with different input types. The aim of the present study is to compare some popular deep learning pre-trained networks using temporally stable and full elastograms, with or without augmentation as well as propose suitable deep learning schemes for CLD diagnosis and progress assessment. 200 liver biopsy validated patients with CLD, underwent US SWE examination. Four images from the same liver area were saved to extract elastograms and processed to exclude areas that were temporally unstable. Then, full and temporally stable masked elastograms for each patient were separately fed into GoogLeNet, AlexNet, VGG16, ResNet50 and DenseNet201 with and without augmentation. The networks were tested for differentiation of CLD stages in seven classification schemes over 30 repetitions using liver biopsy as the reference. All networks achieved maximum mean accuracies ranging from 87.2%-97.4% and area under the receiver operating characteristic curves (AUCs) ranging from 0.979-0.990 while the radiologists had AUCs ranging from 0.800-0.870. ResNet50 and DenseNet201 had better average performance than the other networks. The use of the temporal stability mask led to improved performance on about 50% of inputs and network combinations while augmentation led to lower performance for all networks. These findings can provide potential networks with higher accuracy and better setting in the CLD diagnosis and progress assessment. A larger data set would help identify the best network and settings for CLD assessment in clinical practice.
- Published
- 2020
- Full Text
- View/download PDF
30. 2D perfusion DSA with an open-source, semi-automated, color-coded software for the quantification of foot perfusion following infrapopliteal angioplasty: a feasibility study.
- Author
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Kagadis GC, Tsantis S, Gatos I, Spiliopoulos S, Katsanos K, and Karnabatidis D
- Subjects
- Algorithms, Blood Flow Velocity, Feasibility Studies, Female, Humans, Male, Middle Aged, Prospective Studies, Radiographic Image Interpretation, Computer-Assisted, Angiography, Digital Subtraction, Endovascular Procedures methods, Foot blood supply, Ischemia diagnostic imaging, Ischemia surgery, Peripheral Arterial Disease diagnostic imaging, Peripheral Arterial Disease surgery, Software
- Abstract
Background: Foot perfusion has been recently implemented as a new tool for optimizing outcomes of peripheral endovascular procedures. A custom-made, two-dimensional perfusion digital subtraction angiography (PDSA) algorithm has been implemented to quantify outcomes of endovascular treatment of critical limb ischemia (CLI), assist intra-procedural decision-making, and enhance clinical outcomes., Methods: The study was approved by the Hospital's Ethics Committee. This prospective, single-center study included seven consecutive patients scheduled to undergo infrapopliteal endovascular treatment of CLI. Perfusion blood volume (PBV), mean transit time (MTT), and perfusion blood flow (PBF) maps were extracted by analyzing time-intensity curves and signal intensity on the perfused vessel mask. Mean values calculated from user-specified regions of interest (ROIs) on perfusion maps were employed to evaluate pre- and post-endovascular treatment condition. Measurements were performed immediately after final PDSA., Results: In total, five patients (aged 54 ± 16 years, mean ± standard deviation) were analyzed, as two patients were excluded due to significant motion artifacts. Post-procedural MTT presented a mean decrease of 19.1% for all patients and increased only in 1 of 5 patients, demonstrating in 4/5 patients an increase in tissue perfusion after revascularization. Overall mean PBF and PBV values were also analogously increased following revascularization (446% and 69.5% mean, respectively) and in the majority of selected ROIs (13/15 and 12/15 ROIs, respectively)., Conclusions: Quantification of infrapopliteal angioplasty outcomes using this newly proposed, custom-made, intra-procedural PDSA algorithm was performed using PBV, MTT, and PBF maps. Further studies are required to determine its role in peripheral endovascular procedures ( ClinicalTrials.gov Identifier: NCT04356092).
- Published
- 2020
- Full Text
- View/download PDF
31. Computer-based quantification of an atraumatic sinus augmentation technique using CBCT.
- Author
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Inchingolo F, Dipalma G, Paduanelli G, De Oliveira LA, Inchingolo AM, Georgakopoulos PI, Inchingolo AD, Malcangi G, Athanasiou E, Fotopoulou E, Tsantis S, Georgakopoulos IP, Diem Kieu NC, Gargiulo Isacco C, Ballini A, Goker F, Mortellaro C, Greco Lucchina A, and Del Fabbro M
- Subjects
- Bone Transplantation, Humans, Maxillary Sinus diagnostic imaging, Maxillary Sinus surgery, Middle Aged, Prospective Studies, Dental Implants, Platelet-Rich Fibrin, Sinus Floor Augmentation, Spiral Cone-Beam Computed Tomography
- Abstract
Our group recently developed an innovative maxillary sinus augmentation technique without the need of sinus membrane elevation, termed as "IPG" DET protocol. This technique utilizes autologous platelet concentrates (including platelet rich plasma (PRP), platelet rich fibrin (PRF), growth factors (GFs) and CD34+ stem cells), together with bone grafting materials positioned through intentionally perforated Schneider's membrane for flapless implant placement. This study aimed at evaluating the performance of "IPG" DET protocol in terms of new bone formation and implant stability at 8 months post-op. This prospective study consisted of forty-eight patients with a mean age of 52.8 years. A total of eighty-five implants were placed with "IPG" DET protocol in combination with autologous platelet concentrates. CBCT (cone beam computed tomography) was performed at two different time points: pre-operatively and at 8 months post-op. CBCT images were then compared by an intensity-based image algorithm to assess the newly formed bone in terms of gray scale values. Additionally, implant stability quotient (ISQ) was used to estimate implant osseointegration and success rate. The average new bone formation was 5.9 ± 0.9 mm2 per implant. All implants successfully osseointegrated, and ISQ ranged 62.3-71.7. According to the results of this study, "IPG" DET protocol in combination with autologous platelet concentrates is a successful technique for implant-supported rehabilitation of the edentulous posterior maxilla without the need of sinus floor elevation., (Copyright 2020 Biolife Sas. www.biolifesas.org.)
- Published
- 2019
32. Temporal stability assessment in shear wave elasticity images validated by deep learning neural network for chronic liver disease fibrosis stage assessment.
- Author
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Gatos I, Tsantis S, Spiliopoulos S, Karnabatidis D, Theotokas I, Zoumpoulis P, Loupas T, Hazle JD, and Kagadis GC
- Subjects
- Case-Control Studies, Chronic Disease, Fibrosis, Humans, Reproducibility of Results, Time Factors, Deep Learning, Elasticity Imaging Techniques, Image Processing, Computer-Assisted methods, Liver diagnostic imaging, Liver pathology, Liver Cirrhosis diagnostic imaging
- Abstract
Purpose: To automatically detect and isolate areas of low and high stiffness temporal stability in shear wave elastography (SWE) image sequences and define their impact in chronic liver disease (CLD) diagnosis improvement by means of clinical examination study and deep learning algorithm employing convolutional neural networks (CNNs)., Materials and Methods: Two hundred SWE image sequences from 88 healthy individuals (F0 fibrosis stage) and 112 CLD patients (46 with mild fibrosis (F1), 16 with significant fibrosis (F2), 22 with severe fibrosis (F3), and 28 with cirrhosis (F4)) were analyzed to detect temporal stiffness stability between frames. An inverse Red, Green, Blue (RGB) colormap-to-stiffness process was performed for each image sequence, followed by a wavelet transform and fuzzy c-means clustering algorithm. This resulted in a binary mask depicting areas of high and low stiffness temporal stability. The mask was then applied to the first image of the SWE sequence, and the derived, masked SWE image was used to estimate its impact in standard clinical examination and CNN classification. Regarding the impact of the masked SWE image in clinical examination, one measurement by two radiologists was performed in each SWE image and two in the corresponding masked image measuring areas with high and low stiffness temporal stability. Then, stiffness stability parameters, interobserver variability evaluation and diagnostic performance by means of ROC analysis were assessed. The masked and unmasked sets of SWE images were fed into a CNN scheme for comparison., Results: The clinical impact evaluation study showed that the masked SWE images decreased the interobserver variability of the radiologists' measurements in the high stiffness temporal stability areas (interclass correlation coefficient (ICC) = 0.92) compared to the corresponding unmasked ones (ICC = 0.76). In terms of diagnostic accuracy, measurements in the high-stability areas of the masked SWE images (area-under-the-curve (AUC) ranging from 0.800 to 0.851) performed similarly to those in the unmasked SWE images (AUC ranging from 0.805 to 0.893). Regarding the measurements in the low stiffness temporal stability areas of the masked SWE images, results for interobserver variability (ICC = 0.63) and diagnostic accuracy (AUC ranging from 0.622 to 0.791) were poor. Regarding the CNN classification, the masked SWE images showed improved accuracy (ranging from 82.5% to 95.5%) compared to the unmasked ones (ranging from 79.5% to 93.2%) for various CLD stage combinations., Conclusion: Our detection algorithm excludes unreliable areas in SWE images, reduces interobserver variability, and augments CNN's accuracy scores for many combinations of fibrosis stages., (© 2019 American Association of Physicists in Medicine.)
- Published
- 2019
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33. A Machine-Learning Algorithm Toward Color Analysis for Chronic Liver Disease Classification, Employing Ultrasound Shear Wave Elastography.
- Author
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Gatos I, Tsantis S, Spiliopoulos S, Karnabatidis D, Theotokas I, Zoumpoulis P, Loupas T, Hazle JD, and Kagadis GC
- Subjects
- Adolescent, Aged, Algorithms, Chronic Disease, Color, Female, Humans, Liver diagnostic imaging, Male, Middle Aged, Sensitivity and Specificity, Young Adult, Diagnosis, Computer-Assisted methods, Elasticity Imaging Techniques methods, Liver Diseases diagnostic imaging, Machine Learning
- Abstract
The purpose of the present study was to employ a computer-aided diagnosis system that classifies chronic liver disease (CLD) using ultrasound shear wave elastography (SWE) imaging, with a stiffness value-clustering and machine-learning algorithm. A clinical data set of 126 patients (56 healthy controls, 70 with CLD) was analyzed. First, an RGB-to-stiffness inverse mapping technique was employed. A five-cluster segmentation was then performed associating corresponding different-color regions with certain stiffness value ranges acquired from the SWE manufacturer-provided color bar. Subsequently, 35 features (7 for each cluster), indicative of physical characteristics existing within the SWE image, were extracted. A stepwise regression analysis toward feature reduction was used to derive a reduced feature subset that was fed into the support vector machine classification algorithm to classify CLD from healthy cases. The highest accuracy in classification of healthy to CLD subject discrimination from the support vector machine model was 87.3% with sensitivity and specificity values of 93.5% and 81.2%, respectively. Receiver operating characteristic curve analysis gave an area under the curve value of 0.87 (confidence interval: 0.77-0.92). A machine-learning algorithm that quantifies color information in terms of stiffness values from SWE images and discriminates CLD from healthy cases is introduced. New objective parameters and criteria for CLD diagnosis employing SWE images provided by the present study can be considered an important step toward color-based interpretation, and could assist radiologists' diagnostic performance on a daily basis after being installed in a PC and employed retrospectively, immediately after the examination., (Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.)
- Published
- 2017
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34. Focal liver lesions segmentation and classification in nonenhanced T2-weighted MRI.
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Gatos I, Tsantis S, Karamesini M, Spiliopoulos S, Karnabatidis D, Hazle JD, and Kagadis GC
- Subjects
- Contrast Media, Humans, ROC Curve, Sensitivity and Specificity, Algorithms, Carcinoma, Hepatocellular diagnostic imaging, Liver Neoplasms diagnostic imaging, Magnetic Resonance Imaging
- Abstract
Purpose: To automatically segment and classify focal liver lesions (FLLs) on nonenhanced T2-weighted magnetic resonance imaging (MRI) scans using a computer-aided diagnosis (CAD) algorithm., Methods: 71 FLLs (30 benign lesions, 19 hepatocellular carcinomas, and 22 metastases) on T2-weighted MRI scans were delineated by the proposed CAD scheme. The FLL segmentation procedure involved wavelet multiscale analysis to extract accurate edge information and mean intensity values for consecutive edges computed using horizontal and vertical analysis that were fed into the subsequent fuzzy C-means algorithm for final FLL border extraction. Texture information for each extracted lesion was derived using 42 first- and second-order textural features from grayscale value histogram, co-occurrence, and run-length matrices. Twelve morphological features were also extracted to capture any shape differentiation between classes. Feature selection was performed with stepwise multilinear regression analysis that led to a reduced feature subset. A multiclass Probabilistic Neural Network (PNN) classifier was then designed and used for lesion classification. PNN model evaluation was performed using the leave-one-out (LOO) method and receiver operating characteristic (ROC) curve analysis., Results: The mean overlap between the automatically segmented FLLs and the manual segmentations performed by radiologists was 0.91 ± 0.12. The highest classification accuracies in the PNN model for the benign, hepatocellular carcinoma, and metastatic FLLs were 94.1%, 91.4%, and 94.1%, respectively, with sensitivity/specificity values of 90%/97.3%, 89.5%/92.2%, and 90.9%/95.6% respectively. The overall classification accuracy for the proposed system was 90.1%., Conclusions: Our diagnostic system using sophisticated FLL segmentation and classification algorithms is a powerful tool for routine clinical MRI-based liver evaluation and can be a supplement to contrast-enhanced MRI to prevent unnecessary invasive procedures., (© 2017 American Association of Physicists in Medicine.)
- Published
- 2017
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35. A new computer aided diagnosis system for evaluation of chronic liver disease with ultrasound shear wave elastography imaging.
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Gatos I, Tsantis S, Spiliopoulos S, Karnabatidis D, Theotokas I, Zoumpoulis P, Loupas T, Hazle JD, and Kagadis GC
- Subjects
- Adolescent, Adult, Aged, Chronic Disease, Female, Humans, Male, Middle Aged, Young Adult, Diagnosis, Computer-Assisted methods, Elasticity Imaging Techniques methods, Liver Diseases diagnostic imaging, Mechanical Phenomena
- Abstract
Purpose: Classify chronic liver disease (CLD) from ultrasound shear-wave elastography (SWE) imaging by means of a computer aided diagnosis (CAD) system., Methods: The proposed algorithm employs an inverse mapping technique (red-green-blue to stiffness) to quantify 85 SWE images (54 healthy and 31 with CLD). Texture analysis is then applied involving the automatic calculation of 330 first and second order textural features from every transformed stiffness value map to determine functional features that characterize liver elasticity and describe liver condition for all available stages. Consequently, a stepwise regression analysis feature selection procedure is utilized toward a reduced feature subset that is fed into the support vector machines (SVMs) classification algorithm in the design of the CAD system., Results: With regard to the mapping procedure accuracy, the stiffness map values had an average difference of 0.01 ± 0.001 kPa compared to the quantification results derived from the color-box provided by the built-in software of the ultrasound system. Highest classification accuracy from the SVM model was 87.0% with sensitivity and specificity values of 83.3% and 89.1%, respectively. Receiver operating characteristic curves analysis gave an area under the curve value of 0.85 with [0.77-0.89] confidence interval., Conclusions: The proposed CAD system employing color to stiffness mapping and classification algorithms offered superior results, comparing the already published clinical studies. It could prove to be of value to physicians improving the diagnostic accuracy of CLD and can be employed as a second opinion tool for avoiding unnecessary invasive procedures.
- Published
- 2016
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36. A new automated quantification algorithm for the detection and evaluation of focal liver lesions with contrast-enhanced ultrasound.
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Gatos I, Tsantis S, Spiliopoulos S, Skouroliakou A, Theotokas I, Zoumpoulis P, Hazle JD, and Kagadis GC
- Subjects
- Adult, Aged, Area Under Curve, Contrast Media, Female, Humans, Male, Middle Aged, ROC Curve, Ultrasonography, Video Recording, Wavelet Analysis, Young Adult, Image Interpretation, Computer-Assisted methods, Liver diagnostic imaging, Liver Neoplasms diagnostic imaging, Support Vector Machine
- Abstract
Purpose: Detect and classify focal liver lesions (FLLs) from contrast-enhanced ultrasound (CEUS) imaging by means of an automated quantification algorithm., Methods: The proposed algorithm employs a sophisticated segmentation method to detect and contour focal lesions from 52 CEUS video sequences (30 benign and 22 malignant). Lesion detection involves wavelet transform zero crossings utilization as an initialization step to the Markov random field model toward the lesion contour extraction. After FLL detection across frames, time intensity curve (TIC) is computed which provides the contrast agents' behavior at all vascular phases with respect to adjacent parenchyma for each patient. From each TIC, eight features were automatically calculated and employed into the support vector machines (SVMs) classification algorithm in the design of the image analysis model., Results: With regard to FLLs detection accuracy, all lesions detected had an average overlap value of 0.89 ± 0.16 with manual segmentations for all CEUS frame-subsets included in the study. Highest classification accuracy from the SVM model was 90.3%, misdiagnosing three benign and two malignant FLLs with sensitivity and specificity values of 93.1% and 86.9%, respectively., Conclusions: The proposed quantification system that employs FLLs detection and classification algorithms may be of value to physicians as a second opinion tool for avoiding unnecessary invasive procedures.
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- 2015
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37. Venous drug-eluting vs. bare-metal stenting: an experimental animal study using frequency domain optical coherence tomography.
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Kitrou PM, Spiliopoulos S, Katsanos K, Tsantis S, Diamantopoulos A, Kallidonis P, Kyriakopoulou M, Kagadis GC, Karnabatidis D, and Siablis D
- Subjects
- Angiography, Digital Subtraction, Animals, Disease Models, Animal, Follow-Up Studies, Iliac Vein diagnostic imaging, Iliac Vein pathology, Immunosuppressive Agents pharmacology, Male, Peripheral Vascular Diseases diagnostic imaging, Peripheral Vascular Diseases pathology, Prosthesis Design, Rabbits, Sirolimus analogs & derivatives, Sirolimus pharmacology, Time Factors, Angioplasty, Balloon methods, Blood Vessel Prosthesis, Drug-Eluting Stents, Iliac Vein surgery, Peripheral Vascular Diseases surgery, Tomography, Optical Coherence methods
- Abstract
Introduction: This protocol was designed to evaluate the safety and feasibility of implanting drug-eluting stents (DES), as well as to compare their long-term results versus bare-metal stents (BMS), in a rabbit venous model, using frequency-domain optical coherence tomography (FD-OCT)., Methods: Thirteen New Zealand white rabbits underwent implantation of a zotarolimus-eluting stent in the iliac vein (DES Group) and a BMS in the contralateral iliac vein (BMS Group). The study's primary endpoints included technical success and the comparison of in-stent neointimal hyperplasia in the two study groups, using ex vivo FD-OCT, at 3 months., Results: Thirteen DES and 13 BMS were successfully implanted. The technical success rate was 100% (26/26 stents). Three animals (3/13, 23.0%) died within the first 45 days. The remaining 10/13 animals (77%) were euthanized on the 90th day following stent implantation. The 20 stents were successfully removed. Successful ex vivo FD-OCT was performed in all stent-implanted iliac vein segments, 10 in the DES Group and 10 in the BMS Group. There was no statistically significant difference in the mean neointimal thickness between the two groups (3.02 ± 1.19 mm2 in DES Group vs. 2.76 ± 1.17 mm2 in BMS Group; p=0.0501)., Conclusions: In this experimental protocol, DES implantation in the venous system was safe and feasible. Hyperplasia thickness was similar in both groups after 3 months' follow up.
- Published
- 2014
38. Multiresolution edge detection using enhanced fuzzy c-means clustering for ultrasound image speckle reduction.
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Tsantis S, Spiliopoulos S, Skouroliakou A, Karnabatidis D, Hazle JD, and Kagadis GC
- Subjects
- Artifacts, Cluster Analysis, Humans, Liver diagnostic imaging, Signal-To-Noise Ratio, Software, Thyroid Gland diagnostic imaging, Ultrasonography, Mammary methods, Wavelet Analysis, Algorithms, Image Enhancement methods, Ultrasonography methods
- Abstract
Purpose: Speckle suppression in ultrasound (US) images of various anatomic structures via a novel speckle noise reduction algorithm., Methods: The proposed algorithm employs an enhanced fuzzy c-means (EFCM) clustering and multiresolution wavelet analysis to distinguish edges from speckle noise in US images. The edge detection procedure involves a coarse-to-fine strategy with spatial and interscale constraints so as to classify wavelet local maxima distribution at different frequency bands. As an outcome, an edge map across scales is derived whereas the wavelet coefficients that correspond to speckle are suppressed in the inverse wavelet transform acquiring the denoised US image., Results: A total of 34 thyroid, liver, and breast US examinations were performed on a Logiq 9 US system. Each of these images was subjected to the proposed EFCM algorithm and, for comparison, to commercial speckle reduction imaging (SRI) software and another well-known denoising approach, Pizurica's method. The quantification of the speckle suppression performance in the selected set of US images was carried out via Speckle Suppression Index (SSI) with results of 0.61, 0.71, and 0.73 for EFCM, SRI, and Pizurica's methods, respectively. Peak signal-to-noise ratios of 35.12, 33.95, and 29.78 and edge preservation indices of 0.94, 0.93, and 0.86 were found for the EFCM, SIR, and Pizurica's method, respectively, demonstrating that the proposed method achieves superior speckle reduction performance and edge preservation properties. Based on two independent radiologists' qualitative evaluation the proposed method significantly improved image characteristics over standard baseline B mode images, and those processed with the Pizurica's method. Furthermore, it yielded results similar to those for SRI for breast and thyroid images significantly better results than SRI for liver imaging, thus improving diagnostic accuracy in both superficial and in-depth structures., Conclusions: A new wavelet-based EFCM clustering model was introduced toward noise reduction and detail preservation. The proposed method improves the overall US image quality, which in turn could affect the decision-making on whether additional imaging and/or intervention is needed.
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- 2014
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39. The impact of Platelet Rich Plasma (PRP) in osseointegration of oral implants in dental panoramic radiography: texture based evaluation.
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Georgakopoulos I, Tsantis S, Georgakopoulos P, Korfiatis P, Fanti E, Martelli M, Costaridou L, Petsas T, Panayiotakis G, and Martelli FS
- Abstract
Purpose: In this study the temporal texture differentiation associated with the bone formation properties, around loaded oral implants after Platelet Rich Plasma (PRP) employment, was investigated in Panoramic Radiographs., Materials and Methods: Thirty eligible patients are randomly assigned to two groups. The test group received PRP application around new implants, while in the control group no PRP treatment was made. The bone-to-implant contact region was analyzed in a clinical sample of 60 Digitized Panoramic Radiographs, 30 corresponding to immediate implant loading (Class-I) and 30 after an 8 month follow-up period (Class-II). This region was sampled by 1146 circular Regions-of-Interest (ROIs), resulting from a specifically designed segmentation scheme based on Markov-Random-Fields (MRF). From each ROI, 41 textural features were extracted, then reduced to a subset of 4 features due to redundancy and employed as input to Receiver-Operating-Characteristic (ROC) analysis, to assess the textural differentiation between two classes., Results: The selected subset, achieved Area-Under-Curve (AUC) values ranging from 0.77-0.81 in the PRP group, indicating the significant temporal textural differentiation has been made. In the control group, the AUC values ranged from 0.56-0.68 demonstrating lesser osseo integration activity., Conclusion: This study provides evidences that PRP application may favor bone formation around loaded dental implants that could modify the dental treatment planning.
- Published
- 2014
40. Automatic quantitative analysis of in-stent restenosis using FD-OCT in vivo intra-arterial imaging.
- Author
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Mandelias K, Tsantis S, Spiliopoulos S, Katsakiori PF, Karnabatidis D, Nikiforidis GC, and Kagadis GC
- Subjects
- Humans, Reproducibility of Results, Sensitivity and Specificity, Artificial Intelligence, Endovascular Procedures methods, Femoral Artery pathology, Graft Occlusion, Vascular pathology, Image Interpretation, Computer-Assisted methods, Pattern Recognition, Automated methods, Tomography, Optical Coherence methods
- Abstract
Purpose: A new segmentation technique is implemented for automatic lumen area extraction and stent strut detection in intravascular optical coherence tomography (OCT) images for the purpose of quantitative analysis of in-stent restenosis (ISR). In addition, a user-friendly graphical user interface (GUI) is developed based on the employed algorithm toward clinical use., Methods: Four clinical datasets of frequency-domain OCT scans of the human femoral artery were analyzed. First, a segmentation method based on fuzzy C means (FCM) clustering and wavelet transform (WT) was applied toward inner luminal contour extraction. Subsequently, stent strut positions were detected by utilizing metrics derived from the local maxima of the wavelet transform into the FCM membership function., Results: The inner lumen contour and the position of stent strut were extracted with high precision. Compared to manual segmentation by an expert physician, the automatic lumen contour delineation had an average overlap value of 0.917 ± 0.065 for all OCT images included in the study. The strut detection procedure achieved an overall accuracy of 93.80% and successfully identified 9.57 ± 0.5 struts for every OCT image. Processing time was confined to approximately 2.5 s per OCT frame., Conclusions: A new fast and robust automatic segmentation technique combining FCM and WT for lumen border extraction and strut detection in intravascular OCT images was designed and implemented. The proposed algorithm integrated in a GUI represents a step forward toward the employment of automated quantitative analysis of ISR in clinical practice.
- Published
- 2013
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41. Automatic vessel lumen segmentation and stent strut detection in intravascular optical coherence tomography.
- Author
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Tsantis S, Kagadis GC, Katsanos K, Karnabatidis D, Bourantas G, and Nikiforidis GC
- Subjects
- Femoral Artery surgery, Humans, Hyperplasia etiology, Image Enhancement methods, Image Interpretation, Computer-Assisted methods, Neointima diagnosis, Neointima etiology, Reproducibility of Results, Sensitivity and Specificity, Algorithms, Blood Vessel Prosthesis adverse effects, Femoral Artery pathology, Foreign Bodies diagnosis, Pattern Recognition, Automated methods, Stents adverse effects, Tomography, Optical Coherence methods
- Abstract
Purpose: Optical coherence tomography (OCT) is a catheter-based imaging method that employs near-infrared light to produce high-resolution cross-sectional intravascular images. The authors propose a segmentation technique for automatic lumen area extraction and stent strut detection in intravascular OCT images for the purpose of quantitative analysis of neointimal hyperplasia (NIH)., Methods: A clinical dataset of frequency-domain OCT scans of the human femoral artery was analyzed. First, a segmentation method based on the Markov random field (MRF) model was employed for lumen area identification. Second, textural and edge information derived from local intensity distribution and continuous wavelet transform (CWT) analysis were integrated to extract the inner luminal contour. Finally, the stent strut positions were detected via the introduction of each strut wavelet response across scales into a feature extraction and classification scheme in order to optimize the strut position detection., Results: The inner lumen contour and the position of stent strut were extracted with very high accuracy. Compared with manual segmentation by an expert vascular physician the automatic segmentation had an average overlap value of 0.937 ± 0.045 for all OCT images included in the study. The strut detection accuracy had an area under the curve (AUC) value of 0.95, together with sensitivity and specificity average values of 0.91 and 0.96, respectively., Conclusions: A robust automatic segmentation technique integrating textural and edge information for vessel lumen border extraction and strut detection in intravascular OCT images was designed and presented. The proposed algorithm may be employed for automated quantitative morphological analysis of in-stent neointimal hyperplasia.
- Published
- 2012
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42. Morphological and wavelet features towards sonographic thyroid nodules evaluation.
- Author
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Tsantis S, Dimitropoulos N, Cavouras D, and Nikiforidis G
- Subjects
- Humans, Image Enhancement methods, Neural Networks, Computer, ROC Curve, Subtraction Technique, Thyroid Gland diagnostic imaging, Thyroid Gland pathology, Pattern Recognition, Automated methods, Signal Processing, Computer-Assisted, Thyroid Nodule diagnostic imaging, Thyroid Nodule pathology, Ultrasonography methods
- Abstract
This paper presents a computer-based classification scheme that utilized various morphological and novel wavelet-based features towards malignancy risk evaluation of thyroid nodules in ultrasonography. The study comprised 85 ultrasound images-patients that were cytological confirmed (54 low-risk and 31 high-risk). A set of 20 features (12 based on nodules boundary shape and 8 based on wavelet local maxima located within each nodule) has been generated. Two powerful pattern recognition algorithms (support vector machines and probabilistic neural networks) have been designed and developed in order to quantify the power of differentiation of the introduced features. A comparative study has also been held, in order to estimate the impact speckle had onto the classification procedure. The diagnostic sensitivity and specificity of both classifiers was made by means of receiver operating characteristics (ROC) analysis. In the speckle-free feature set, the area under the ROC curve was 0.96 for the support vector machines classifier whereas for the probabilistic neural networks was 0.91. In the feature set with speckle, the corresponding areas under the ROC curves were 0.88 and 0.86 respectively for the two classifiers. The proposed features can increase the classification accuracy and decrease the rate of missing and misdiagnosis in thyroid cancer control.
- Published
- 2009
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43. Development of a support vector machine-based image analysis system for assessing the thyroid nodule malignancy risk on ultrasound.
- Author
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Tsantis S, Cavouras D, Kalatzis I, Piliouras N, Dimitropoulos N, and Nikiforidis G
- Subjects
- Humans, Risk Assessment methods, Sensitivity and Specificity, Thyroid Neoplasms classification, Thyroid Neoplasms pathology, Thyroid Nodule pathology, Ultrasonography, Algorithms, Image Interpretation, Computer-Assisted methods, Thyroid Neoplasms diagnostic imaging, Thyroid Nodule diagnostic imaging
- Abstract
An SVM-based image analysis system was developed for assessing the malignancy risk of thyroid nodules. Ultrasound images of 120 cytology confirmed thyroid nodules (78 low-risk and 42 high-risk of malignancy) were manually segmented by a physician using a custom developed software in C++. From each nodule, 40 textural features were automatically calculated and were used with the SVM algorithm in the design of the image analysis system. Highest classification accuracy was 96.7%, misdiagnosing two high-risk and two low-risk thyroid nodules. The proposed system may be of value to physicians as a second opinion tool for avoiding unnecessary invasive procedures.
- Published
- 2005
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44. The development and validation of an algorithm for real-time computerised fetal heart rate monitoring in labour.
- Author
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Taylor GM, Mires GJ, Abel EW, Tsantis S, Farrell T, Chien PF, and Liu Y
- Subjects
- Adolescent, Adult, Data Interpretation, Statistical, Female, Humans, Observer Variation, Pregnancy, Prospective Studies, Algorithms, Cardiotocography standards, Heart Rate, Fetal physiology, Labor, Obstetric physiology
- Abstract
Objective: To develop and validate a computerised algorithm for the interpretation of the characteristics of fetal heart rate monitoring in labour., Design: Prospective observational study., Setting: Labour ward in a tertiary hospital., Sample: Intrapartum cardiotocograms from 24 pregnancies., Methods: A computerised algorithm was developed to assess the fetal heart baseline rate, variability, the number of accelerations and the number of decelerations. Twenty five minute segments of cardiotocograms were interpreted by the algorithm and also by seven expert reviewers independently. The reviewers were unaware of the outcome of labour. The reliability of the characteristics of cardiotocography and the validity of the computerised algorithm were assessed using the intraclass correlation coefficient and weighted kappa statistic for continuous and ordinal variables respectively., Results: The inter rater reliability of the baseline fetal heart rate and the number and type of decelerations was good (intraclass correlation coefficient 0.93, 0.93 and 0.79, respectively). The reliability of baseline variability (kappa = 0.27) and accelerations (intraclass correlation coefficient = 0.27) was poor. The computerised algorithm had good agreement with the reviewers for the baseline fetal heart rate (intraclass correlation coefficient 0.91 to 0.98) and the number of decelerations (intraclass correlation coefficient 0.82 to 0.91), but was less valid as regards the number of late decelerations (intraclass correlation coefficient 0.68 to 0.85) and the number of accelerations (intraclass correlation coefficient 0.06 to 0.80), and was invalid as regards baseline variability (kappa 0.00 to 0.34)., Conclusions: The high level of validity of the computerised algorithm for the estimation of the baseline fetal heart rate and the number of decelerations justifies its further technical development.
- Published
- 2000
- Full Text
- View/download PDF
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