{"id":{"repo_id":"greece","oai_identifier":"oai:10442/1733"},"canonical_url":"https://search.dev.ndltd.org/etd/greece/oai:10442/1733","repository":{"repo_id":"greece","name":"Greek National Archive of PhD Theses","base_url":"https://phdtheses.ekt.gr/eadd_oai/request"},"display":{"title":"Ανάπτυξη συστήματος τομογραφικής απεικόνισης σε εξομοιωτή ακτινοθεραπείας","abstract":"A method of optimized efficiency for the retrospective reconstruction of tomograms is presented. The method has been developed for use with isocentric fluoroscopic units and is capable of performing Digital Tomosynthesis of anatomical planes with any orientation and at any distance from the isocenter. Optimization of efficiency has been achieved by segmenting the reconstruction process into discrete transformations that are specific to groups of pixels, rather than performing pixel by pixel operations. These involve a number of projections of the acquired image matrices as well as parallel translations and summing. Application of this method has resulted in an estimated 60-fold reduction of computing time, thus maintaining computer power requirements to a minimum. A technique has also been developed for the separation and subsequent removal of undesirable information from the reconstructed plane. The method involves the reconstruction of the blur originating in user-selected \"noisy\" planes as this appears on the plane of interest. This is achieved by projecting the reconstructed images of the selected plane on the image formation plane for all viewing angles and subsequently, synthesizing its blurred image on the plane of interest. There are no restrictions as to the number and the location of the planes to be removed. The technique can be modified to suit any reconstruction algorithm. The proposed algorithm and the noise removal technique were experimentally tested with the use of the phantom and were also evaluated on clinical images.","abstract_html":"A method of optimized efficiency for the retrospective reconstruction of tomograms is presented. The method has been developed for use with isocentric fluoroscopic units and is capable of performing Digital Tomosynthesis of anatomical planes with any orientation and at any distance from the isocenter. Optimization of efficiency has been achieved by segmenting the reconstruction process into discrete transformations that are specific to groups of pixels, rather than performing pixel by pixel operations. These involve a number of projections of the acquired image matrices as well as parallel translations and summing. Application of this method has resulted in an estimated 60-fold reduction of computing time, thus maintaining computer power requirements to a minimum. A technique has also been developed for the separation and subsequent removal of undesirable information from the reconstructed plane. The method involves the reconstruction of the blur originating in user-selected "noisy" planes as this appears on the plane of interest. This is achieved by projecting the reconstructed images of the selected plane on the image formation plane for all viewing angles and subsequently, synthesizing its blurred image on the plane of interest. There are no restrictions as to the number and the location of the planes to be removed. The technique can be modified to suit any reconstruction algorithm. The proposed algorithm and the noise removal technique were experimentally tested with the use of the phantom and were also evaluated on clinical images.","abstract_has_math":false,"creators":["Kolitsi, Zoi","Κολίτση, Ζωή"],"institution":"University of Patras","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":1991,"date_issued":"1991","date_published":"1991","updated_at":"2026-07-24T02:25:05Z","subjects":["Ανακατασκευή εικόνας","Τομογραφία περιορισμένης γωνίας","Τομογραφικός θόρυβος","Τομοσύνθεση","Ψηφιακή τομοσύνθεση","Digital tomosynthesis","Image processing","Image reconstruction","Limited-angle tomography","Tomographic noise","Ιατρική και Επιστήμες Υγείας","Άλλες Ιατρικές Επιστήμες","Medical and Health Sciences","Other Medical Sciences"],"languages":["gre"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["10.12681/eadd/1733"],"render_values":[{"text":"10.12681/eadd/1733","href":"https://doi.org/10.12681/eadd/1733","code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10442/hedi/1733","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Kolitsi, Zoi","Κολίτση, Ζωή"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["1991"]},{"key":"dc:publisher","label":"Institution","values":["University of Patras","Πανεπιστήμιο Πατρών"]},{"key":"dc:type","label":"Dc Type","values":["PhD Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Ανακατασκευή εικόνας","Τομογραφία περιορισμένης γωνίας","Τομογραφικός θόρυβος","Τομοσύνθεση","Ψηφιακή τομοσύνθεση","Digital tomosynthesis","Image processing","Image reconstruction","Limited-angle tomography","Tomographic noise","Ιατρική και Επιστήμες Υγείας","Άλλες Ιατρικές Επιστήμες","Medical and Health Sciences","Other Medical Sciences"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["gre"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["10.12681/eadd/1733","http://hdl.handle.net/10442/hedi/1733"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["A method of optimized efficiency for the retrospective reconstruction of tomograms is presented. The method has been developed for use with isocentric fluoroscopic units and is capable of performing Digital Tomosynthesis of anatomical planes with any orientation and at any distance from the isocenter. Optimization of efficiency has been achieved by segmenting the reconstruction process into discrete transformations that are specific to groups of pixels, rather than performing pixel by pixel operations. These involve a number of projections of the acquired image matrices as well as parallel translations and summing. Application of this method has resulted in an estimated 60-fold reduction of computing time, thus maintaining computer power requirements to a minimum. A technique has also been developed for the separation and subsequent removal of undesirable information from the reconstructed plane. The method involves the reconstruction of the blur originating in user-selected \"noisy\" planes as this appears on the plane of interest. This is achieved by projecting the reconstructed images of the selected plane on the image formation plane for all viewing angles and subsequently, synthesizing its blurred image on the plane of interest. There are no restrictions as to the number and the location of the planes to be removed. The technique can be modified to suit any reconstruction algorithm. The proposed algorithm and the noise removal technique were experimentally tested with the use of the phantom and were also evaluated on clinical images.","Η εργασία αυτή παρουσιάζει μία μέθοδο για την ανακατασκευή τομογραφικών εικόνων, που χαρακτηρίζεται από βελτιστοποιημένη υπολογιστική απόδοση. Η μέθοδος έχει αναπτυχθεί για χρήση με ισοκεντρικά ακτινοσκοπικά μηχανήματα και μπορεί να εκτελεί ψηφιακή τομοσύνθεση ανατομικών επιπέδων τυχαίου προσανατολισμού και απόστασης από το ισόκεντρο. Η βελτιστοποίηση της απόδοσης επιτυγχάνεται με την κατάταξη των ρουτινών της ανακατασκευής σε διακριτούς μετασχηματισμούς που αφορούν ομάδες από pixel και στη συνέχεια την εκτέλεση των πράξεων ομαδικά. Οι μετασχηματισμοί αυτοί περιλαμβάνουν μία σειρά από προβολές των αρχικών λήψεων, παράλληλες μετατοπίσεις και άθροιση μητρών. Η εφαρμογή της μεθόδου απέδωσε μία μείωση του απαιτούμενου υπολογιστικού χρόνου στο 1/60 της αρχικής του τιμής, ελαχιστοποιώντας έτσι τις απαιτήσεις σε υπολογιστική ισχύ. Παράλληλα αναπτύχθηκε μία τεχνική για τον διαχωρισμό και στην συνέχεια την αφαίρεση του τομογραφικού θορύβου από τις ανακατασκευασμένες εικόνες. Ο θόρυβος που προέρχεται από επιλεγμένα από τον χρήστη επίπεδα, ανακατασκευάζεται όπως ακριβώς αυτός παρουσιάζεται στο επίπεδο ενδιαφέροντος. Δεν υπάρχουν περιορισμοί ως προς τον αριθμό και την θέση των προς αφαίρεση επιπέδων, ενώ η τεχνική μπορεί να χρησιμοποιηθεί σε οποιοδήποτε σύστημα ψηφιακής τομοσύνθεσης. Ο αλγόριθμος που αναπτύχθηκε καθώς και η τεχνική της αφαίρεσης του θορύβου αξιολογήθηκαν πειραματικά, με την χρήση ομοιωμάτων και ακολούθησε μία προκαταρκτική κλινική τους αξιολόγηση."]},{"key":"dc:title","label":"Title","values":["Ανάπτυξη συστήματος τομογραφικής απεικόνισης σε εξομοιωτή ακτινοθεραπείας","Development of a tomographic imaging system for use with a radiotherapy simulator"]}]}],"canonical_facts":{"dc:creator":["Kolitsi, Zoi","Κολίτση, Ζωή"],"dc:date":["1991"],"dc:description":["A method of optimized efficiency for the retrospective reconstruction of tomograms is presented. The method has been developed for use with isocentric fluoroscopic units and is capable of performing Digital Tomosynthesis of anatomical planes with any orientation and at any distance from the isocenter. Optimization of efficiency has been achieved by segmenting the reconstruction process into discrete transformations that are specific to groups of pixels, rather than performing pixel by pixel operations. These involve a number of projections of the acquired image matrices as well as parallel translations and summing. Application of this method has resulted in an estimated 60-fold reduction of computing time, thus maintaining computer power requirements to a minimum. A technique has also been developed for the separation and subsequent removal of undesirable information from the reconstructed plane. The method involves the reconstruction of the blur originating in user-selected \"noisy\" planes as this appears on the plane of interest. This is achieved by projecting the reconstructed images of the selected plane on the image formation plane for all viewing angles and subsequently, synthesizing its blurred image on the plane of interest. There are no restrictions as to the number and the location of the planes to be removed. The technique can be modified to suit any reconstruction algorithm. The proposed algorithm and the noise removal technique were experimentally tested with the use of the phantom and were also evaluated on clinical images.","Η εργασία αυτή παρουσιάζει μία μέθοδο για την ανακατασκευή τομογραφικών εικόνων, που χαρακτηρίζεται από βελτιστοποιημένη υπολογιστική απόδοση. Η μέθοδος έχει αναπτυχθεί για χρήση με ισοκεντρικά ακτινοσκοπικά μηχανήματα και μπορεί να εκτελεί ψηφιακή τομοσύνθεση ανατομικών επιπέδων τυχαίου προσανατολισμού και απόστασης από το ισόκεντρο. Η βελτιστοποίηση της απόδοσης επιτυγχάνεται με την κατάταξη των ρουτινών της ανακατασκευής σε διακριτούς μετασχηματισμούς που αφορούν ομάδες από pixel και στη συνέχεια την εκτέλεση των πράξεων ομαδικά. Οι μετασχηματισμοί αυτοί περιλαμβάνουν μία σειρά από προβολές των αρχικών λήψεων, παράλληλες μετατοπίσεις και άθροιση μητρών. Η εφαρμογή της μεθόδου απέδωσε μία μείωση του απαιτούμενου υπολογιστικού χρόνου στο 1/60 της αρχικής του τιμής, ελαχιστοποιώντας έτσι τις απαιτήσεις σε υπολογιστική ισχύ. Παράλληλα αναπτύχθηκε μία τεχνική για τον διαχωρισμό και στην συνέχεια την αφαίρεση του τομογραφικού θορύβου από τις ανακατασκευασμένες εικόνες. Ο θόρυβος που προέρχεται από επιλεγμένα από τον χρήστη επίπεδα, ανακατασκευάζεται όπως ακριβώς αυτός παρουσιάζεται στο επίπεδο ενδιαφέροντος. Δεν υπάρχουν περιορισμοί ως προς τον αριθμό και την θέση των προς αφαίρεση επιπέδων, ενώ η τεχνική μπορεί να χρησιμοποιηθεί σε οποιοδήποτε σύστημα ψηφιακής τομοσύνθεσης. Ο αλγόριθμος που αναπτύχθηκε καθώς και η τεχνική της αφαίρεσης του θορύβου αξιολογήθηκαν πειραματικά, με την χρήση ομοιωμάτων και ακολούθησε μία προκαταρκτική κλινική τους αξιολόγηση."],"dc:identifier":["10.12681/eadd/1733","http://hdl.handle.net/10442/hedi/1733"],"dc:language":["gre"],"dc:publisher":["University of Patras","Πανεπιστήμιο Πατρών"],"dc:subject":["Ανακατασκευή εικόνας","Τομογραφία περιορισμένης γωνίας","Τομογραφικός θόρυβος","Τομοσύνθεση","Ψηφιακή τομοσύνθεση","Digital tomosynthesis","Image processing","Image reconstruction","Limited-angle tomography","Tomographic noise","Ιατρική και Επιστήμες Υγείας","Άλλες Ιατρικές Επιστήμες","Medical and Health Sciences","Other Medical Sciences"],"dc:title":["Ανάπτυξη συστήματος τομογραφικής απεικόνισης σε εξομοιωτή ακτινοθεραπείας","Development of a tomographic imaging system for use with a radiotherapy simulator"],"dc:type":["PhD Thesis"]},"updated_at":"2026-07-24T02:25:05Z"}