Improving visualisation of bronchi in three-dimensional rendering of

103 Pages·2007·1.83 MB·English

Examensarbete
Improving visualisation of bronchi in three-dimensional
rendering of CT data
Kristian Ko¨ps´en
LiTH - IMT / MI20 - EX - - 07 / 446 - - SE

Improving visualisation of bronchi in three-dimensional
rendering of CT data
Department of Biomedical Engineering, Linko¨pings Universitet
Kristian K¨ops´en
LiTH - IMT / MI20 - EX - - 07 / 446 - - SE
Examensarbete: 20 p
Level: D
Supervisors: Mats Andersson,
Department of Biomedical Engineering, Linko¨pings Universitet
Fredrik Karlsson,
Sectra Imtec AB
Examiner: Hans Knutsson,
Department of Biomedical Engineering, Linko¨pings Universitet
Linko¨ping: January 2007

Datum
Avdelning, Institution
Date
Division, Department
Institutionen fo¨r Medicinsk Teknik January 2007
581 85 LINKO¨PING
SWEDEN
Spr˚ak Rapporttyp ISBN
Language Report category
ISRN
Svenska/Swedish Licentiatavhandling
LiTH - IMT / MI20 - EX - - 07 / 446 - - SE
x Engelska/English x Examensarbete
C-uppsats Serietitel och serienummer ISSN
D-uppsats Titleofseries,numbering
O¨vrigrapport
URL fo¨r elektronisk version
http://www.ep.liu.se/
Titel
Improving visualisation of bronchi in three-dimensional rendering of CT data
Title
Fo¨rfattare Kristian Ko¨ps´en
Author
Sammanfattning
Abstract
ThemedicalimagingsystemSectraPACSfromSectraImteccontainsa3Dmodethat
can be used for visualising image stacks from e.g. computed tomography. Various
structures of humananatomy can be visualised in the 3D mode, but visualisationsof
the bronchial tree of the lungs rarely become good enough to be useful. The goal of
this work was to investigate ways of improving such visualisations.
Variousapproacheswerestudied, evaluatedandtested. Thefactthatmosteffortwas
needed for small structures with sizes similar to the resolution of the images made
things slightly more complicated. A method classifying neighbourhoods based on
localstructureemergedasmostpromising,andwasusedasfoundationforaproposed
algorithm. Itcreatesamaskrepresentingthepresenceofbronchi,allowingthehiding
of uninteresting structures in its proximity. The algorithm was then implemented so
that it could be tested together with the existing system.
The method was found to work well and was able to detect the smaller tubes of
the bronchial tree and output the desired classification mask. Its usefulness was
somewhat reduced by issues relating to speed, and the fact that many computed
tomographyimagestackslackthenecessaryresolutionforvisualisingthe finerdetails
of the bronchial tree.
Nyckelord
computed tomography, bronchi, visualisation, image enhancement
Keyword
vi
Abstract
ThemedicalimagingsystemSectraPACSfromSectraImteccontainsa3Dmode
that can be used for visualising image stacks from e.g. computed tomography.
Various structures of human anatomy can be visualised in the 3D mode, but
visualisations of the bronchial tree of the lungs rarely become good enough to
be useful. The goal of this work was to investigate ways of improving such
visualisations.
Various approaches were studied, evaluated and tested. The fact that most
effort was needed for small structures with sizes similar to the resolutionof the
images made things slightly more complicated. A method classifying neigh-
bourhoods based on local structure emerged as most promising, and was used
asfoundationforaproposedalgorithm. Itcreatesamaskrepresentingthepres-
ence of bronchi,allowingthe hiding ofuninteresting structures in its proximity.
The algorithm was then implemented so that it could be tested together with
the existing system.
Themethodwasfoundtoworkwellandwasabletodetectthesmallertubes
of the bronchial tree and output the desired classification mask. Its usefulness
was somewhat reduced by issues relating to speed, and the fact that many
computedtomographyimagestackslackthenecessaryresolutionforvisualising
the finer details of the bronchial tree.
Keywords: computedtomography,bronchi,visualisation,imageenhancement
K¨ops´en, 2007. vii
viii
Acknowledgements
First ofall, I wouldlike to thank Sectra Imtec for giving me the opportunity to
perform this very interesting project. Thank you, Fredrik Karlsson for keeping
me on trackand positive, andeveryone at PD RADIT for help, goodideas and
being part of a pleasant work environment.
I would also like to thank Mats Andersson and Hans Knutsson at IMT for
useful opinions, feedback and suggestions.
K¨ops´en, 2007. ix
x