Tomosynthesis in Digital Dental Xrays

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IMPLEMENTATION OF TOMOSYNTHESIS IN DENTAL X-RAY IMAGING

by

Arda Varlsüha

B.Sc., Electronics Engineering, stanbul Technical University , 2010

Submitted to the Institute of Biomedical Engineering in partial fulllment of the requirements for the degree of Master of Science in Biomedical Engineering

Bo§aziçi University 2012

ii

IMPLEMENTATION OF TOMOSYNTHESIS IN DENTAL X-RAY IMAGING

APPROVED BY:

Prof. Dr. Cengizhan Öztürk (Thesis Advisor)

...................

Assoc. Prof. Dr. Albert Güveni³

...................

Asst. Prof. Dr. “enol Mutlu

...................

DATE OF APPROVAL:

15 June 2012

iii

Acknowledgements

It is a pleasure to thank the many people who made this thesis possible. It is dicult to overstate my gratitude to my supervisor Prof. Dr. Cengizhan Öztürk. Thanks to him I had chance to observe dierent aspects of biomediHe supported me to achieve my goals and provided me with

cal engineering.

opportunities along the way.

I would like to thank the X-Lab team, especially my boss Aytaç Durmaz for his technical, motivational and logistic support in the lab. I also would like to thank to my lab partners, Mustafa Porsuk and Merve Atik for their company and tolerance. I wish them the best of luck.

I thank the other team members of Kandilli, especially Tu§ba Gözdamla and Sevim Tekeli for their support and motivation. essential members at Kandilli for years to come. I hope they will stay as

I would like to thank my best friend slam Tete for all the good times we share for many years. I also like to thank to Cem Sümengen and Bilgin Kzlta³ for their comradery both during and after ITU. I hope that our paths will cross again somewhere and sometime in life.

Finally I would like to thank to my mother and father for all their support from the day I was born. I cannot possibly repay them in any way.

This thesis is dedicated to my grandmother.

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Abstract

IMPLEMENTATION OF TOMOSYNTHESIS IN DENTAL X-RAY IMAGING

Digital tomosynthesis is a method of reconstructing any number of tomographic planes, by using a set of limited angle projections, acquired as the X-ray source moves around the object. The quality of the reconstructed planes is aected by structured artifacts, due to blur from planes other than the planeof-interest. In this project a special multiple projection algorithm along with an out-of-plane blur removal method is implemented to improve the image quality.

In-silico phantom experiments was employed to evaluate the parameters that aect the image quality in tomosynthesis. Dierent groups were created

with varying arc lenghts and projection counts. A blur removal method was implemented during image reconstruction to increase image quality. Image quality was evaluated by both visual assessment and structural similarity analysis. The proposed noise removal algorithm resulted in images with less artifacts.

Preliminary tests of the algorithm were also done in a physical dental phantom. The results showed that the tomosynthesis image reconstruction could be a promising and a low cost method to evaluate digital dental x-rays without excess radiation to the patient.

Keywords: Tomosynthesis, X-ray, Digital imaging, Dental imaging.

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Özet

TOMOSENTEZN D“ X-RAY GÖRÜNTÜLERNE UYGULANMASI

Dijital tomosentez, X ³n kayna§nn nesne etrafnda oluturduu bir hareketle, snrl bir aç diliminde ald§ görüntüleri kullanarak istenen kesitleri olu³turma yöntemidir. Olu³turulan kesitlerin kalitesi, odaklanlan kesitin d³nda kalan kesitlerdeki yaplarn olu³turdu§u bulanklk sebebi ile etkilenebilir. Bu çal³mada, özel bir ço§ul görüntüleme algoritmas uyarlamak ve kesit-d³ bulankl§ giderme metodu, kesitlerin görüntü kalitesini arttrmak için kullanlmtr.

Tomossentezde görüntü kalitesini etkileyen etkenleri de§erlendirmek için bilgisayar ortamnda fantom deneyleri yaplm³tr. Farkl açlarda ve projek-

siyon...
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