Imaging performance of a CaWO4/CMOS sensor

The aim of this study was to investigate the modulation transfer function (MTF) and the effective gain transfer function (eGTF) of a non-destruc­­tive testing (NDT)/industrial inspection complementary metal oxide semi­conductor (CMOS) sensor in conjunction with a thin calcium tungstate (CaWO4) screen. Thin screen samples, with dimensions of 2.7x3.6 cm2 and thick­ness of 118.9 μm, estimated from scanning electron microscopy-SEM im­ages, were extracted from an Agfa Curix universal screen and coupled to the active area of an active pixel (APS) CMOS sensor. MTF was assessed using the slanted-edge method, following the IEC 62220-1-1:2015 method. MTF values were found high across the examined spatial frequency range. eGTF was found maximum when CaWO4 was combined with charge-coupled devices (CCD) of broadband anti-reflection (AR) coating (17.52 at 0 cycles/mm). The com­bi­nation of the thin CaWO4 screen with the CMOS sensor provided very pro­mis­ing image resolution and adequate efficiency properties, thus could be also con­sidered for use in CMOS based X-ray imaging devices, for various applications

Development of new digital signal and image analysis and pattern recognition methods in medical applications

Objective: The objective of the present PhD Thesis was the development and application of image analysis and pattern recognition methods, using histopathology images of laryngeal tumors which had been immunohistochemically (IHC) stained for p63 expression, for: a) investigating the association between P63 stained nuclei and histologic grade in laryngeal tumor lesions, b) designing a decision support system (DSS) for discriminating between low and high grade laryngeal cancer cases, and c) developing DSS-system for predicting the 5-year survival of patients with laryngeal squamous cell carcinoma.Material and Methods: Biopsy specimens from laryngeal tumor lesions of 55 patients diagnosed with laryngeal squamous cell carcinomas were Hematoxylin & Eosin (HE) stained for histological tumour grade and stage assessment, and immunohistochemically (IHC) stained for P63 expression. Four non-overlapping microscopy images were digitized from each patient’s IHC specimens, in regions indicated by the expert physician. In each image, P63 positively expressed nuclei were identified, by specially designed segmentation method, and the percentage of P63 expressed nuclei was computed. A number of textural and morphological features were generated from each of the P63 stained nuclei and data thus formed was used to form three classes (21 lesions of grade I, 34 lesions of grade II and grade III). Features of high discriminatory power amongst the classes were determined, employing non-parametric statistical methods, and the effect of tumour grade on the nucleus structure was analysed. Next, two DSS-systems were developed, employing the CUDA parallel programming capabilities of Nvidia GPU cards for achieving high precision designs. One DSS was designed to discriminate low from high grade laryngeal cancer lesions and another to predict 5-year survival of patients with laryngeal cancer. Results-Conclusions: Textural features that sustained statistically significant differences between low and high grade lesions revealed that with advancing grade, %P63 expression decreased, P63 stained nuclei appeared of lower image intensity, more inhomogeneous, of higher local contrast, containing smaller randomly distributed dissimilar structures and having more irregular shape. DSS performance in classifying laryngeal cancer cases as low grade and high grade was 85.7% and 94.1% respectively. The system’s overall accuracy was 90.9% and its estimated accuracy to “unseen” by the system cases was 80%. The DSS accuracy in assessing the 5-year survival of patients with laryngeal cancer was 90.5%, and texture in p63 expressed nuclei appeared coarser and with more edges in the 5-year non-survivors.Σκοπός: Ο σκοπός της παρούσας διατριβής ήταν η ανάπτυξη και υλοποίηση μεθόδων επεξεργασίας και ανάλυσης ιατρικών εικόνων μικροσκοπίου από υλικό βιοψίας καρκίνου του λάρυγγα καθώς και ο σχεδιασμός και υλοποίηση συστημάτων υποστήριξης διάγνωσης με μεθόδους αναγνώρισης προτύπων με στόχο: α) την διερεύνηση της μεταβολής της δομής του κυττάρου με αυξανόμενο βαθμό κακοήθειας του καρκίνου, β) την διάγνωση του βαθμού κακοήθειας του όγκου και γ) την εκτίμηση της πενταετούς, από πρώτη διάγνωση, επιβίωσης ασθενών με καρκίνο του λάρυγγα.Υλικό και μέθοδοι: Το υλικό προήρχετο από πενήντα πέντε (55) βιοψίες καρκίνου του λάρυγγα, από ισάριθμους ασθενείς, με επιβεβαίωση ως προς τον βαθμό κακοήθειας του όγκου (21-18-16 όγκοι με Ι-ΙΙ-ΙΙΙ βαθμού κακοήθεια, αντίστοιχα). Όλο το ιστοπαθολογικό υλικό παραχωρήθηκε από το τμήμα Παθολογοανατομίας του Πανεπιστημιακού Νοσοκομείου της Πάτρας. Το υλικό βιοψίας είχε ειδικά παρασκευαστεί, είχε χρώση p63, και είχε συσκευαστεί σε ειδικές καλυπτρίδες. Το υλικό ελέγχθηκε σε οπτικό μικροσκόπιο και τέσσερεις εικόνες, ειδικά επιλεγμένες από την έμπειρη παθολογοανατόμο ιατρό, ψηφιοποιήθηκαν προς περεταίρω επεξεργασία. Υλοποιήθηκαν μέθοδοι επεξεργασίας εικόνας και μη-επιβλεπόμενης ταξινόμησης για την τμηματοποίηση της εικόνας και την εύρεση των πυρήνων του κυττάρου που είχαν εκφραστεί με p63 χρώση. Από τους πυρήνες προέκυψαν εξήντα δύο (62) χαρακτηριστικά από την υφή, περίγραμμα, σχήμα, μορφή και διασπορά (συγκέντρωση) των πυρήνων στο κύτταρο και κάθε ασθενής αντιπροσωπεύθηκε από ένα διάνυσμα 62 τιμών, που ήταν οι μέσες τιμές των χαρακτηριστικών από όλους τους πυρήνες στις 4 εικόνες μικροσκοπίου του όγκου. Εξετάστηκε η μεταξύ κατηγοριών (3 κατηγορίες Ι, ΙΙ, ΙΙΙ βαθμού κακοήθεια) διαχωριστική ικανότητα των χαρακτηριστικών, βρέθηκαν εκείνα που είχαν στατιστικά σημαντικές διαφορές μεταξύ των κατηγοριών και αναλύθηκε η επίδραση του βαθμού κακοήθειας στην σύσταση της δομής του πυρήνα. Στη συνέχεια, η επεξεργασία μεταφέρθηκε στους επεξεργαστές μίας κάρτας γραφικών και έγινε χρήση παράλληλου προγραμματισμού για τον βέλτιστο σχεδιασμό συστημάτων υποστήριξης απόφασης, λόγω του υπερβολικού φόρτου επεξεργασίας που ήταν χρονικά απαγορευτικός για να πραγματοποιηθεί ο σχεδιασμός στους επεξεργαστές του Η/Υ. Σχεδιάστηκε ένα σύστημα υποστήριξης απόφασης για την διάγνωση του βαθμού κακοήθειας του καρκίνου του λάρυγγα καθώς και ένα άλλο για την εκτίμηση της πιθανότητας πενταετούς επιβίωσης του ασθενούς, χρησιμοποιώντας τον ταξινομητή πιθανοκρατικών νευρωνικών δικτύων (PNN), την εξαντλητική αναζήτηση συνδυασμών χαρακτηριστικών, και των LOO και ECV μεθόδων αξιολόγησης της ακρίβειας ταξινόμησης.Αποτελέσματα-Συμπεράσματα: Τα αποτελέσματα έδειξαν ότι με αυξανόμενο το βαθμό κακοήθειας του καρκίνου του λάρυγγα το ποσοστό P63 έκφρασης μειώνεται, η ένταση απεικόνισης των p63 εκφρασμένων πυρήνων μειώνεται, η υφή των καθίσταται πιο ανομοιογενής, αποτελούμενη από μικρότερα ανόμοια δομικά στοιχεία τυχαία κατανεμημένα, και το σχήμα των πυρήνων καθίσταται περισσότερο ακανόνιστο.Στο σύστημα υποστήριξης διάγνωσης για το βαθμό κακοήθειας, τα ποσοστά διάγνωσης ήταν υψηλά με περίπου 90% συνολική ακρίβεια στην εκτίμηση του βαθμού κακοήθειας στα δεδομένα της μελέτης και για χαρακτηριστικά που σχετίζονταν με την ομοιογένεια της υφής των πυρήνων, των δομών εντός του πυρήνα, και της διασποράς ή συγκέντρωσης των πυρήνων.Στο σύστημα υποστήριξης διάγνωσης για την εκτίμηση της πενταετούς επιβίωσης των ασθενών με καρκίνο του λάρυγγα η ακρίβεια στα δεδομένα της μελέτης ήταν περίπου 90% και τα χαρακτηριστικά που χρησιμοποιήθηκαν στον καλύτερο σχεδιασμό σχετίζονταν με το περιεχόμενο υψηλής συχνότητας της εικόνας του πυρήνα, με την ανισοτροπία στην τυχαιότητα των τόνων της υφής του πυρήνα, με το σχήμα του πυρήνα, και τον βαθμό κακοήθειας του όγκου. Η μελέτη έδειξε επίσης ότι χαρακτηριστικά σχετιζόμενα με την ύπαρξη ακμών στην επιφάνεια του πυρήνα διαχώριζαν στατιστικά σημαντικά τις δύο κατηγορίες πενταετούς επιβίωσης αναδεικνύοντας έτσι το ότι η υφή των πυρήνων των αποβιωσάντων ασθενών ήταν περισσότερο τραχεία σε στατιστικά σημαντικό βαθμό

Baseline characteristics in laparoscopic simulator performance: The impact of personal computer (PC)-gaming experience and visuospatial ability

Background: Learning via simulators is under constant development, and it is important to further optimize simulator training curricula. This study investigates the impact of personal computer-gaming experience, visuospatial skills, and repetitive training on laparoscopic simulator performance and specifically on the constituent parameters of the simulator score. Methods: Forty-sevenmedical students completed 3 consecutive-Minimally Invasive Surgical Trainer-Virtual Reality simulator trials. Previously, they performed a visuospatial test and completed a questionnaire regarding baseline characteristics and personal computer-gaming experience. Linear regression was used to analyze the relationship between simulator performance and type of personal computer-gaming experience and visuospatial ability. Results: During the first 2 Minimally Invasive Surgical Trainer-Virtual Reality simulation tasks, there was an association between personal computer-gaming experience and the coordination parameters of the score (eg, EconDiath task 1: P=.0047; EconDiath task 2: P=.0102; EconDiath task 3: P=.0836). The type of game category played seemed to have an impact on the coordination parameters (eg, EconDiath task 1-3 for sport games versus no-sport games: P=.01, P=.0013, and P=.01, respectively). In the first-Minimally Invasive Surgical Trainer task, visuospatial ability correlated with Minimally Invasive Surgical Trainer simulator performance but was abolished with repetitive training (overall Minimally Invasive Surgical Trainer score task 1-3: P = .0122, P = .0991, and P = .3506, respectively). Sex-specific differences were noted initially but were abolished with training. Conclusion: Sport games versus no-sport games demonstrated a significantly better Minimally Invasive Surgical Trainer performance. Furthermore, repetitive laparoscopic simulator training may compensate for a previous lack of personal computer-gaming experience, low visuospatial ability, and sex differences.(C) 2020 Published by Elsevier Inc

Variable selection in nonlinear modeling based on RBF networks and evolutionary computation

In this paper a novel variable selection method based on Radial Basis Function (RBF) neural networks and genetic algorithms is presented. The fuzzy means algorithm is utilized as the training method for the RBF networks, due to its inherent speed, the deterministic approach of selecting the hidden node centers and the fact that it involves only a single tuning parameter. The trade-off between the accuracy and parsimony of the produced model is handled by using Final Prediction Error criterion, based on the RBF training and validation errors, as a fitness function of the proposed genetic algorithm. The tuning parameter required by the fuzzy means algorithm is treated as a free variable by the genetic algorithm. The proposed method was tested in benchmark data sets stemming from the scientific communities of time-series prediction and medicinal chemistry and produced promising results

Baseline characteristics in laparoscopic simulator performance : The impact of personal computer (PC)–gaming experience and visuospatial ability

Background: Learning via simulators is under constant development, and it is important to further optimize simulator training curricula. This study investigates the impact of personal computer–gaming experience, visuospatial skills, and repetitive training on laparoscopic simulator performance and specifically on the constituent parameters of the simulator score. Methods: Forty-seven medical students completed 3 consecutive Minimally Invasive Surgical Trainer–Virtual Reality simulator trials. Previously, they performed a visuospatial test and completed a questionnaire regarding baseline characteristics and personal computer–gaming experience. Linear regression was used to analyze the relationship between simulator performance and type of personal computer–gaming experience and visuospatial ability. Results: During the first 2 Minimally Invasive Surgical Trainer–Virtual Reality simulation tasks, there was an association between personal computer–gaming experience and the coordination parameters of the score (eg, EconDiath task 1: P = .0047; EconDiath task 2: P = .0102; EconDiath task 3: P = .0836). The type of game category played seemed to have an impact on the coordination parameters (eg, EconDiath task 1–3 for sport games versus no-sport games: P = .01, P = .0013, and P = .01, respectively). In the first Minimally Invasive Surgical Trainer task, visuospatial ability correlated with Minimally Invasive Surgical Trainer simulator performance but was abolished with repetitive training (overall Minimally Invasive Surgical Trainer score task 1–3: P = .0122, P = .0991, and P = .3506, respectively). Sex-specific differences were noted initially but were abolished with training. Conclusion: Sport games versus no-sport games demonstrated a significantly better Minimally Invasive Surgical Trainer performance. Furthermore, repetitive laparoscopic simulator training may compensate for a previous lack of personal computer–gaming experience, low visuospatial ability, and sex differences

The use of simulators to acquire ERCP skills : a systematic review

Background and Aims: Endoscopic retrograde cholangiopancreatography (ERCP) is a technically demanding diagnostic and therapeutic endoscopic procedure with a high risk for adverse events such as post-ERCP pancreatitis and bleeding. Since endoscopists with less experience have higher adverse event rates, the training of new residents on ERCP simulators has been suggested to improve the resident's technical skills necessary for ERCP. However, there is a lack of consensus on whether the training program should focus on a threshold number of procedures or be more tailored to the individual's performance. Furthermore, there is also disagreement on which form of simulator(s) should be used. Therefore, the primary outcome of this systematic review was to study the extent to which simulators used for ERCP training are correctly validated. Methods: In 2022, a systematic search of the literature was conducted on MEDLINE and SCOPUS under the guidance of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) 2020 protocol seeking articles with the MeSH terms 'Endoscopic Retrograde Cholangiopancreatography' OR 'ERCP' in combination with 'simulation' OR 'simulator'. Results: The search resulted in 41 references. A total of 19 articles met the inclusion criteria and were included in the qualitative analysis. Only one of the articles fulfilled the criteria of a robust validation study. Conclusions: Since only one of the 19 articles met the requirements for a thorough and correct validation, further studies with sufficient numbers of subjects, that evaluate complete preclinical training programs based on validated ERCP simulators are warranted

Use of saliva stress biomarkers to estimate novice male endoscopist’s stress during training in a high-end simulator

Objective: Simulated endoscopic training can be challenging and stressful for the novice trainee. The absence of a reliable stress detection method during simulated endoscopic training makes estimating trainees’ mental stress difficult to quantify. This study concomitantly measures the responses of four saliva stress biomarkers and compares them to the video score (VS) achieved by novice endoscopists in a reproducibly stressful simulation environment. Methods: Thirty-six male endoscopy naïve surgery residents were enrolled. After an orientation phase, a saliva specimen was collected for cortisol (sC), alpha-amylase (sAA), Chromogranin A (sCgA), and immunoglobulin A (sIgA) measurements (baseline phase, BL). Thereafter, the simulation exercise phase (E) started, practicing in the Fundamentals of Endoscopic Surgery Skills module (GI-Bronch Mentor). Immediately after, a second saliva sample for measuring the above-cited biomarkers was collected. The whole experiment was videotaped, and the VS was calculated. The percentage (E-BL)diff of each of the four saliva biomarkers was calculated and examined for correlation to VS. Results: sCgAdiff showed the best correlation with VS, followed by sAAdiff. Conclusions: sCgA and sAA, are saliva stress biomarkers that are easy to collect non-invasively and showed the best correlation with novice endoscopist’s performance in our simulation setting, and therefore, they could be used for monitoring stress

Use of saliva stress biomarkers to estimate novice male endoscopist's stress during training in a high-end simulator

Objective Simulated endoscopic training can be challenging and stressful for the novice trainee. The absence of a reliable stress detection method during simulated endoscopic training makes estimating trainees' mental stress difficult to quantify. This study concomitantly measures the responses of four saliva stress biomarkers and compares them to the video score (VS) achieved by novice endoscopists in a reproducibly stressful simulation environment. Methods Thirty-six male endoscopy naive surgery residents were enrolled. After an orientation phase, a saliva specimen was collected for cortisol (sC), alpha-amylase (sAA), Chromogranin A (sCgA), and immunoglobulin A (sIgA) measurements (baseline phase, BL). Thereafter, the simulation exercise phase (E) started, practicing in the Fundamentals of Endoscopic Surgery Skills module (GI-Bronch Mentor). Immediately after, a second saliva sample for measuring the above-cited biomarkers was collected. The whole experiment was videotaped, and the VS was calculated. The percentage (E-BL)(diff) of each of the four saliva biomarkers was calculated and examined for correlation to VS. Results sCgA(diff) showed the best correlation with VS, followed by sAA(diff). Conclusions sCgA and sAA, are saliva stress biomarkers that are easy to collect non-invasively and showed the best correlation with novice endoscopist's performance in our simulation setting, and therefore, they could be used for monitoring stress