O Objetivo desse trabalho é avaliar a Dinâmica Gástrica e o Trânsito Oro-Esofágico em imagens cintilográficas por meio de uma técnica de fluxo óptico chamada Técnica Aprimorada de Demons. Essa técnica permite obter a velocidade dos pixels, também chamada Força de Deformação, em imagens sequenciais aos pares por meio de 3 características das imagens: o gradiente, a intensidade dos pixels e a informação ortogonal ao gradiente. Para alcançar o nosso objetivo, foram utilizadas imagens cintilográficas obtidas no Banco de Imagens do Hospital das Clínicas da USP de Ribeirão Preto. Essas imagens foram adquiridas segundo 2 protocolos: Trânsito Oro-Esofágico e Enchimento Gástrico. Sob o protocolo de Trânsito Oro-Esofágico, foram selecionadas imagens referentes a 9 voluntários saudáveis. Esses, em um período de jejum mínimo de 8 horas, fizeram 10 deglutições de 5 ml de solução fisiológica sendo as deglutições de número 1, 4, 7 e 10 feitas com a solução fisiológica \"marcada\'\' com aproximadamente 26 MBq (cerca de 700 µCi) de 99mTecnécio ligado a moléculas de fitato e adquiridas, pela gamma câmara, como um conjunto de 240 imagens por deglutição. As imagens adquiridas no protocolo de Trânsito Oro-Esofágico foram corrigidas e corregistradas. Os campos de velocidade obtidos foram correlacionados com uma técnica capaz de obter os tempos de trânsito do bolus nas diferentes porções do esôfago. Foi obtida uma alta correlação inversa entre as velocidades e o tempo de trânsito ao longo de todo o esôfago, como esperado. A média das velocidades obtidas no esôfago proximal se aproximou consideravelmente da velocidade da onda peristáltica primária descrita na literatura. Sob o protocolo de Enchimento Gástrico, foram selecionadas imagens referentes a 13 voluntários saudáveis. Os voluntários, em um período de jejum mínimo de 8 horas, ingeriram uma refeição teste líquida \"marcada\'\' com aproximadamente 72 MBq (cerca de 2 mCi) de 99mTecnécio ligado a moléculas de fitato enquanto ocorria a aquisição de um conjunto de 330 imagens pela gamma câmara. As imagens adquiridas no protocolo de Enchimento Gástrico também foram corrigidas e corregistradas. Os campos de velocidades obtidos foram somados para cada par de imagens adquiridas e foi analisada a frequência dominante do módulos desses campos somados no tempo de aquisição por meio da Trânsformada Rápida de Fourier (FFT), com filtro Butterworth bidirecional, em janelas de 4 minutos. Foi obtida a média das frequências dominantes por voluntário e, posteriormente, uma média e um desvio padrão para a amostra de voluntários. Foi feito um teste t de student que revelou que a média amostral da frequência dominante do estômago proximal é condizente com a frequência de contração conhecida na literatura para essa região (1 contração por minuto). Ao se estudar a região distal, foi observado também uma predominância de janelas com frequências próximas a conhecida para contrações do estômago distal (3 contrações por minuto) na maioria dos voluntários. As contrações no estômago também foram analisadas visualmente por meio do divergente do campo de velocidades e do perímetro do estômago nas imagens adquiridas. / The goal of this project is to evaluate the gastric dinamic and the Oro-esophageal transit in scintigraphic images trough an optical flow tecnique called Improved Demons Tecnique. This tecnique provides the velocity of the pixels (also called, Deformation Force - DF) in sequencial images by pairs trough 3 image features: gradient, intensity of the pixels and orthogonal gradient information. To achieve our goal, scintigraphic images from Hospital das Clínicas of Ribeirão Preto database were used. This images were acquired trough 2 protocols: Oro-Esophageal Transit and Gastric Filling. At the Oro-Esophageal Transit protocol, images from 9 healthy volunteers were chosen. The volunteers, under a fasting of at least 8 hours, made ten swallows of 5 ml saline. The swallows number 1, 4, 7 and 10 were made with the saline labelled with about 26 MBq (about 700 µCi) 99mTc-phytate and acquired, by gamma-camera, as a set of 240 images per swallowing. The images acquired under the protocol Oro-Esophageal Transit were corrected and registered. The velocity fields obtained were correlated to a tecnique capable of obtain the relative transit times of the bolus in each region of the oesophagus. A high inverse correlation were obtained between the velocities and the times of transit in the oesophagus as a whole, as expected. The mean of the velocities obtained in the proximal oesophagus approached considerably of the velocity of primary peristaltic pump described in literature. At the Gastric filling protocol, images from 13 healthy volunteers were chosen. The volunteers, under a fasting of at least 8 hours, ingested a liquid meal labeled with about 72 MBq (about 2 mCi) 99mTc-phytate while a set of 330 images were acquired by gamma-camera. This images were also corrected and registered. The velocity fields were summed for each pair of images acquired and the frequency of the magnitude of this summed field, in the time of acquisition, were analyzed by Fast Fourier Transform, with a bidirectional Butterworth filter, in sliding windows of 4 minutes. A mean of the frequencies per volunteer were obtained and, after, a mean and standard deviation for the sample of volunteers. It was made a t student test that showed that the sample mean of the frequency of the proximal estomach is consistent with the known frequency of the contraction for this region (1 contraction per minute). We also studied the distal region. It was observed a predominance of slider windows with frequencies close to the frequency known for contractions of distal stomach (3 contractions per minute) in most of the volunteers. The stomach contractions were also analyzed visually through the divergent of the velocity fields and the perimeter of the stomach in the acquired images.

The aim of this study is the development of a statistical denoising method, to reduce noise in scintigraphic images, preserving image quality characteristics such as contrast, and resolution. The method is based on principal component analysis (PCA) reduces the volume of image data, preserving a large amount of useful information, by considering that a small number of independent image components contain useful information (signal), whereas a large number of independent components contain statistical noise. Therefore, applying PCA and discarding the image components, which correspond to noise, noise reduction can be achieved. PCA is a multivariate correlation analysis technique which explains algebraically a variance-covariance structure of observed data sets with a few linear combinations of original variables [28-30]. The motivation behind PCA is to find a direction, or a few directions, that explain as much of the variability as possible. This is achieved because each direction is associated with a linear sum of the variables, which are linear sums of the initial variables. Thus, the first principal component is the linear sum corresponding to the direction of greatest variability. The search for the second principal component is restricted to variables that are uncorrelated with the first principal component. To assess the performance of the proposed denoising method was compared to four conventional noise reduction methods, employing quantitative image quality characteristics (noise and spatial resolution characteristics). Specifically, the linear filter (smooth 3x3 and smooth 5x5), and the non-linear filter (median 3x3 and median 5x5) were used. Additionally to demonstrate the applicability of the proposed method, it was applied to clinical planar scintigraphic images. / Ο όρος Πυρηνική Ιατρική περιγράφει τις διαγνωστικές και θεραπευτικές διαδικασίες, που απαιτούν την εισαγωγή ραδιοφαρμάκων στον οργανισμό. Οι απεικονιστικές τεχνικές της πυρηνικής ιατρικής αξιοποιούν το γεγονός ότι η ακτινοβολία των ραδιενεργών νουκλιδίων μπορεί να διαπεράσει τους ιστούς και να ανιχνευθεί εξωτερικά, καθιστώντας δυνατή τη μελέτη φυσιολογικών και βιοχημικών διαδικασιών εν εξελίξει σε ζωντανούς οργανισμούς. Η απεικόνιση πυρηνικής ιατρικής χρησιμοποιείται ευρέως στην κλινική πράξη. Σε σύγκριση με άλλες απεικονιστικές τεχνικές έχει το πλεονέκτημα ότι μπορεί να δώσει ταυτόχρονα ανατομικές και λειτουργικές πληροφορίες. Το μειονέκτημα όμως των εικόνων πυρηνικής ιατρικής είναι ο πολύ χαμηλός λόγος σήματος-προς-θόρυβο (signal-to-noise ratio-SNR) σε σχέση με εικόνες άλλων απεικονιστικών τεχνικών. Η εικόνα στην πυρηνική ιατρική αντιστοιχεί στην κατανομή ραδιενεργού υλικού μέσα στο σώμα του ασθενούς. Η τιμή κάθε pixel της εικόνας σχετίζεται με τον αριθμό των γ-φωτονίων που ανιχνεύονται σε μια περίοδο χρόνου. Οι τιμές αυτές ακολουθούν μια στατιστική κατανομή (κατανομή Poisson), λόγω της τυχαίας φύσης της διάσπασης του χορηγούμενου ραδιενεργού υλικού. Η διακύμανση μιας τυχαίας Poisson μεταβλητής ισούται με τη μέση τιμή της και συνεπώς για να μειωθεί η επίδραση του Poisson θορύβου, ο αριθμός των φωτονίων που ανιχνεύονται πρέπει να αυξηθεί. Αυτό μπορεί να επιτευχθεί με τρεις τρόπους. Πρώτον, με αύξηση του χρόνου καταγραφής, που συνεπάγεται όμως αυξημένο κίνδυνο μετακίνησης του ασθενή. Δεύτερον, με αύξηση της δόσης ραδιενεργού υλικού, που δίνεται στον ασθενή, κάτι που προφανώς είναι ανεπιθύμητο. Η τελευταία λύση είναι η χρήση γ-κάμερας με πολλαπλούς ανιχνευτές ή με πολύ ευαίσθητο ανιχνευτή, που συνεπάγεται αυξημένο κόστος και πολυπλοκότητα. Για το λόγο αυτό, τεχνικές ψηφιακής επεξεργασίας για μείωση θορύβου εικόνας μπορούν να συνεισφέρουν σημαντικά στη βελτίωση της εικόνας στην πυρηνική ιατρική. Οι κλασικές τεχνικές μείωσης θορύβου κάνουν χρήση γραμμικών φίλτρων εξομάλυνσης (smoothing filters) για την αντικατάσταση της τιμής κάθε εικονοστοιχείου (pixel) με μια μέση τιμή ,η οποία προκύπτει από τη γειτονιά του. Τα φίλτρα αυτά όμως έχουν το μειονέκτημα ότι μειώνουν την αντίθεση και τη διακριτική ικανότητα της εικόνας. Μη γραμμικά φίλτρα, όπως το median φίλτρο, διατηρούν σε πολλές περιπτώσεις την αντίθεση των δομών, αλλά επίσης υποβαθμίζουν την ποιότητα εικόνας. Ένας από τους λόγους, που οι συμβατικές τεχνικές δεν έχουν ικανοποιητικά αποτελέσματα είναι ότι δεν αντιμετωπίζουν το γεγονός ότι ο θόρυβος σε κάθε pixel εξαρτάται από την ένταση του σήματος (signal dependent noise). Για το λόγο αυτό έχουν προταθεί πρασαρμοζόμενα (adaptive) φίλτρα μείωσης θορύβου. Η κατηγορία των φίλτρων αυτών χρησιμοποιεί στατιστικά κριτήρια για την επιλογή των γειτονικών pixels, που χρησιμοποιούνται για τον υπολογισμό της τιμής του κεντρικού pixel. Στη συγκεκριμένη διπλωματική εργασία υλοποιήθηκε μέθοδος μείωσης θορύβου, που βασίζεται στη Ανάλυση Κύριων Συνιστωσών (Principal Components Analysis, PCA), προσαρμοσμένη σε εικόνες πυρηνικής ιατρικής. Η μέθοδος αυτή στοχεύει στη μείωση του κβαντικού θορύβου Poisson κατανομής, που εμπεριέχεται σε εικόνες πυρηνικής ιατρικής. Η PCA είναι μια στατιστική τεχνική, που εξετάζει τις σχέσεις που διέπουν τις μεταβλητές ενός συνόλου δεδομένων και βρίσκει ένα υποσύνολο από τις πιο σημαντικές μεταβλητές. Οι νέες μεταβλητές περιγράφονται σαν γραμμικός συνδυασμός των αρχικών μεταβλητών και κατατάσσονται σε σειρά σημαντικότητας σε σχέση με τη διακύμανση των δεδομένων που η κάθε μια εκφράζει. Η πρώτη σημαντική συνιστώσα (principal component) είναι η μεταβλητή που εκφράζει το μέγιστο ποσό διακύμανσης. Η δεύτερη σημαντική συνιστώσα εκφράζει το επόμενο μεγαλύτερο ποσό διακύμανσης και είναι ανεξάρτητη από της πρώτης κ.ο.κ.. Ουσιαστικά, το σύνολο των αρχικών σχετιζόμενων μεταβλητών μετασχηματίζεται σε ένα σύνολο ασυσχέτιστων μεταβλητών, όπου οι λιγότερο σημαντικές μεταβλητές μπορούν να απομακρυνθούν χωρίς ουσιαστική απώλεια πληροφορίας. Η κύρια χρήση της PCA είναι να μειωθεί ο όγκος ενός συνόλου δεδομένων και να οδηγηθούμε σε μια βέλτιστη περιγραφή τους. Στην περίπτωση των εικόνων πυρηνικής ιατρικής μπορούμε να θεωρήσουμε ότι λόγω του στατιστικού χαρακτήρα του θορύβου η χρήσιμη πληροφορία περιέχεται σε μικρό αριθμό συνιστωσών, ενώ ο θόρυβος σε ένα μεγάλο αριθμό μη-σημαντικών συνιστωσών. Εφαρμόζοντας συνεπώς την PCA και αφαιρώντας τις συνιστώσες που αντιστοιχούν στον θόρυβο μπορούμε να επιτύχουμε σημαντική μείωση του. Επίσης πραγματοποιήθηκε συγκριτική αξιολόγηση μεταξύ της προτεινόμενης μεθόδου και άλλων μεθόδων μείωσης θορύβου σε εικόνες πυρηνικής ιατρικής. Συγκεκριμένα, η μέθοδος που βασίζεται στη PCA συγκρίθηκε με το φίλτρο εξομάλυνσης (smooth 3x3 και smooth 5x5) και το μη-γραμμικό φίλτρο (median 3x3 και median 5x5). Όλες οι μέθοδοι εφαρμόστηκαν σε πρότυπες εικόνες πυρηνικής ιατρικής, που αποκτήθηκαν με τη βοήθεια δυο ομοιωμάτων, ενός ομοιώματος με μικρές θερμές περιοχές (hot spots phantom) και ενός ομοιώματος μέτρησης διακριτικής ικανότητας (bar phantom) σε διαφορετικούς χρόνους. Στις επεξεργασμένες εικόνες μετρήθηκαν ο θόρυβος, η αντίθεση, ο λόγος αντίθεσης-προς-θόρυβο (Contrast-to-Noise-ratio, CNR) και το εύρος στο ήμισυ της μέγιστης τιμής (Full-Width-of-Half-Maximum, FWHM). Τα αποτελέσματα της σύγκρισης έδειξαν ότι η μέθοδος που βασίζεται στη PCA μειώνει σημαντικά το θόρυβο, ενώ ταυτόχρονα αυξάνει το λόγο αντίθεσης-προς-θόρυβο. Τέλος, πραγματοποιήθηκε πιλοτική μελέτη προτίμησης από δυο πυρηνικούς ιατρούς μεταξύ των μεθόδων μείωσης θορύβου σε δείγμα κλινικών εικόνων συγκεκριμένων εξετάσεων στατικών λήψεων (οστών, πνευμόνων, θυρεοειδούς, παραθυρεοειδούς και νεφρών). Η μελέτη αυτή έδειξε ότι η PCA μειώνει σημαντικά το θόρυβο, ενώ ταυτόχρονα βελτιώνει οπτικά τις ανατομικές δομές των εικόνων.

O Objetivo desse trabalho é avaliar a Dinâmica Gástrica e o Trânsito Oro-Esofágico em imagens cintilográficas por meio de uma técnica de fluxo óptico chamada Técnica Aprimorada de Demons. Essa técnica permite obter a velocidade dos pixels, também chamada Força de Deformação, em imagens sequenciais aos pares por meio de 3 características das imagens: o gradiente, a intensidade dos pixels e a informação ortogonal ao gradiente. Para alcançar o nosso objetivo, foram utilizadas imagens cintilográficas obtidas no Banco de Imagens do Hospital das Clínicas da USP de Ribeirão Preto. Essas imagens foram adquiridas segundo 2 protocolos: Trânsito Oro-Esofágico e Enchimento Gástrico. Sob o protocolo de Trânsito Oro-Esofágico, foram selecionadas imagens referentes a 9 voluntários saudáveis. Esses, em um período de jejum mínimo de 8 horas, fizeram 10 deglutições de 5 ml de solução fisiológica sendo as deglutições de número 1, 4, 7 e 10 feitas com a solução fisiológica \"marcada\'\' com aproximadamente 26 MBq (cerca de 700 µCi) de 99mTecnécio ligado a moléculas de fitato e adquiridas, pela gamma câmara, como um conjunto de 240 imagens por deglutição. As imagens adquiridas no protocolo de Trânsito Oro-Esofágico foram corrigidas e corregistradas. Os campos de velocidade obtidos foram correlacionados com uma técnica capaz de obter os tempos de trânsito do bolus nas diferentes porções do esôfago. Foi obtida uma alta correlação inversa entre as velocidades e o tempo de trânsito ao longo de todo o esôfago, como esperado. A média das velocidades obtidas no esôfago proximal se aproximou consideravelmente da velocidade da onda peristáltica primária descrita na literatura. Sob o protocolo de Enchimento Gástrico, foram selecionadas imagens referentes a 13 voluntários saudáveis. Os voluntários, em um período de jejum mínimo de 8 horas, ingeriram uma refeição teste líquida \"marcada\'\' com aproximadamente 72 MBq (cerca de 2 mCi) de 99mTecnécio ligado a moléculas de fitato enquanto ocorria a aquisição de um conjunto de 330 imagens pela gamma câmara. As imagens adquiridas no protocolo de Enchimento Gástrico também foram corrigidas e corregistradas. Os campos de velocidades obtidos foram somados para cada par de imagens adquiridas e foi analisada a frequência dominante do módulos desses campos somados no tempo de aquisição por meio da Trânsformada Rápida de Fourier (FFT), com filtro Butterworth bidirecional, em janelas de 4 minutos. Foi obtida a média das frequências dominantes por voluntário e, posteriormente, uma média e um desvio padrão para a amostra de voluntários. Foi feito um teste t de student que revelou que a média amostral da frequência dominante do estômago proximal é condizente com a frequência de contração conhecida na literatura para essa região (1 contração por minuto). Ao se estudar a região distal, foi observado também uma predominância de janelas com frequências próximas a conhecida para contrações do estômago distal (3 contrações por minuto) na maioria dos voluntários. As contrações no estômago também foram analisadas visualmente por meio do divergente do campo de velocidades e do perímetro do estômago nas imagens adquiridas. / The goal of this project is to evaluate the gastric dinamic and the Oro-esophageal transit in scintigraphic images trough an optical flow tecnique called Improved Demons Tecnique. This tecnique provides the velocity of the pixels (also called, Deformation Force - DF) in sequencial images by pairs trough 3 image features: gradient, intensity of the pixels and orthogonal gradient information. To achieve our goal, scintigraphic images from Hospital das Clínicas of Ribeirão Preto database were used. This images were acquired trough 2 protocols: Oro-Esophageal Transit and Gastric Filling. At the Oro-Esophageal Transit protocol, images from 9 healthy volunteers were chosen. The volunteers, under a fasting of at least 8 hours, made ten swallows of 5 ml saline. The swallows number 1, 4, 7 and 10 were made with the saline labelled with about 26 MBq (about 700 µCi) 99mTc-phytate and acquired, by gamma-camera, as a set of 240 images per swallowing. The images acquired under the protocol Oro-Esophageal Transit were corrected and registered. The velocity fields obtained were correlated to a tecnique capable of obtain the relative transit times of the bolus in each region of the oesophagus. A high inverse correlation were obtained between the velocities and the times of transit in the oesophagus as a whole, as expected. The mean of the velocities obtained in the proximal oesophagus approached considerably of the velocity of primary peristaltic pump described in literature. At the Gastric filling protocol, images from 13 healthy volunteers were chosen. The volunteers, under a fasting of at least 8 hours, ingested a liquid meal labeled with about 72 MBq (about 2 mCi) 99mTc-phytate while a set of 330 images were acquired by gamma-camera. This images were also corrected and registered. The velocity fields were summed for each pair of images acquired and the frequency of the magnitude of this summed field, in the time of acquisition, were analyzed by Fast Fourier Transform, with a bidirectional Butterworth filter, in sliding windows of 4 minutes. A mean of the frequencies per volunteer were obtained and, after, a mean and standard deviation for the sample of volunteers. It was made a t student test that showed that the sample mean of the frequency of the proximal estomach is consistent with the known frequency of the contraction for this region (1 contraction per minute). We also studied the distal region. It was observed a predominance of slider windows with frequencies close to the frequency known for contractions of distal stomach (3 contractions per minute) in most of the volunteers. The stomach contractions were also analyzed visually through the divergent of the velocity fields and the perimeter of the stomach in the acquired images.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-08-07T19:46:16Z No. of bitstreams: 1 IANNA DUARTE KOBAYASHI DE SOUZA - DISSERTAÇÃO PPGCC 2012..PDF: 9922437 bytes, checksum: d5cbecd7f839d5802dab4ed420e1665b (MD5) / Made available in DSpace on 2018-08-07T19:46:16Z (GMT). No. of bitstreams: 1 IANNA DUARTE KOBAYASHI DE SOUZA - DISSERTAÇÃO PPGCC 2012..PDF: 9922437 bytes, checksum: d5cbecd7f839d5802dab4ed420e1665b (MD5) Previous issue date: 2012-02-29 / O crescimento da incidência da doença arterial coronariana, que atinge parte da população mundial, tem intensificado avanços na área da medicina nuclear, como forma de prevenção e de diagnóstico dessa doença. A cintilografia do miocárdio com técnica SPECT (Single Photon Emission Computed Tomography), associada ao eletrocardiograma, permite a avaliação tanto da funcionalidade quanto da perfusão do músculo cardíaco. Este estudo tem como objetivo principal aplicar técnicas de processamento digital de imagens para segmentar e reorientar automaticamente as imagens 3D de pacientes doentes, geradas por uma gamma camera. Os resultados obtidos foram comparados com os resultados produzidos pela técnica manual e comprovaram a eficácia do método automático proposto. / The increase in incidence of coronary artery disease, which affects part of the world population, has intensified advances in nuclear medicine as a means of prevention and diagnosis of this disease. The myocardial scintigraphy technique SPECT (Single Photon Emission Computed Tomography), associated with the electrocardiogram, enables evaluating both function and perfusion of the heart muscle. The main objective of this study is to apply techniques of digital image processing to segment and reorient automatically the 3D images of sick patients, generated by a gamma camera. The results obtained were compared to those ones produced by a manual technique and the effectiveness of the proposed automatic method was confirmed.