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Identifier |
000454335 |
Title |
Διαμόρφωση συστήματος πλοήγησης με δεδομένα από εγκάρσιες απεικονιστικές μεθόδους για την ακριβή τοποθέτηση ραδιενεργού πλάκας σε ασθενείς που υποβάλλονται σε βραχυθεραπεία |
Alternative Title |
Navigation protocol configuration based on data from transverse imaging methods for the precise placement of radioactive source in patients undergoing brachytherapy |
Author
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Λιακόπουλος, Δημήτριος Α.
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Thesis advisor
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Δετοράκης, Ευστάθιος
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Reviewer
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Παπαδάκη, Εφροσύνη
Περυσινάκης, Κωνσταντίνος
Κυμιωνής, Γεώργιος
Παλλήκαρης, Ιωάννης
Χλουβεράκης, Γρηγόριος
Κουβιδάκης, Αλέξανδρος
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Abstract |
Purpose: To estimate dosimetric plan accuracy of Ophthalmic brachytherapy
with ruthenium-106 (106Ru) plaque based on individualized parameter of ocular
geometry. Moreover, to investigate the possibility of creating fusion images from
magnetic tomography (in the preoperative period) and special protocol of dual energy
computed tomography (DECT) (in the postoperative period with plaque placed on the
scleral surface) as a tool for confirming the anatomic accuracy of plaque placement.
Additionally, to determine a protocol of dual energy computed tomography that will
suppress metal artifacts and accurately depict the placed plaque.
Materials and Methods: Thirty patients with intraocular lesions undergone
brachytherapy using plaque 106Ru of inner radius of 12mm. Imaging with magnetic
tomography used to determine the external sclera radius at the tumor site and the tumor
margins. Mathematical algorithm was used to calculate the distance between the
external sclera and the internal surface of the plaque. The differences between the
typical ocular parameters (sclera radius of 12 mm) and individualized parameters in the
applied radiation dose to the tumor apex, the sclera and the tumor margins were
calculated with Plaque SimulatorTM software (Eye Physics LLC, Los Alamitos, CA).
On the second part of the study, six patients with intraocular lesions were included.
Fusion images of preoperative magnetic resonance imaging and postoperative DECT
imaging were constructed in the ImFusion software (ImFusion GmbH, Munchen,
Germany). Clearance margins between the tumor and plaque edge in sagittal, coronal
and transverse planes and also elevation of the posterior edge of the plaque from the
sclera were recorded and correlated with tumor location. Finally, an anthropomorphic
phantom simulating an adult head was used for implementation of nine protocols of
DECT imaging of the orbits after plaque placement. Monochromatic 140keV were
obtained using iterative reconstruction and metal artifact reduction algorithm. The
DECT imaging protocol providing accurate orientation of plaque using minimum
radiation exposure was identified.
Results: Taking into account the individualized ocular and tumor geometry the
calculated applied dose was found to be overestimated at the points of interest namely
the tumor apex, tumor margins and sclera compared to the calculated applied dose using
the typical ocular parameters. The clearance margins were found greater in all planes (sagittal, coronal and transverse) for lesions which are located anteriorly (anterior to the
ocular equator) compared to the posteriorly located lesions. The posterior elevation of
the plaque edge from the sclera was higher for the anteriorly located lesions compared
to the posterior ones. All DECT protocols were found to facilitate accurate plaque
demarcation in spite of some moderate artifacts. The suggested DECT protocol was
found to have a radiation dose exposure to the ocular lens at the lowest limit of the
range that is observed with single energy computed tomography.
Conclusions: The suggested approach of individualized brachytherapy 106Ru
includes a preliminary study encompassing geometrical parameters of the eye and the
tumor from magnetic resonance imaging in order to improve precision of dosimetric
calculation. The individualized dosimetry brachytherapy plan can prevent insufficient
treatment of intraocular tumors especially for eyes with axial length that refrains from
mean values. Additionally, fusion images from DECT and magnetic resonance imaging
can be used as a tool to confirm the accuracy of plaque 106Ru placement in accordance
with the intraocular tumor. The appropriate protocol for orbital DECT imaging after
plaque 106Ru placement was determined and allowed for the plaque demarcation with
minimal artifacts and low radiation exposure for the patient also providing the
possibility for verification of accurate plaque placement.
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Language |
Greek, English |
Subject |
Ophthalmic imaging |
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Ophthalmic oncology |
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Plaque |
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Radiotherapy plate |
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Ακτινοθεραπεία |
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Οφθαλμική απεικόνιση |
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Οφθαλμική ογκολογία |
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Οφθαλμολογία |
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Ραδεινεργός πλάκα |
Issue date |
2023-04-05 |
Collection
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School/Department--School of Medicine--Department of Medicine--Doctoral theses
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Type of Work--Doctoral theses
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Permanent Link |
https://elocus.lib.uoc.gr//dlib/c/3/f/metadata-dlib-1683709406-372168-17218.tkl
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