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Author:Eriksson, Mikael
Title:Comparison of five methods for deformable, multi-modal image registration in prostate and pelvic area
Jämförelse av fem metoder för deformerbar, multimodal bildregistrering i prostata- och bäckenområdet
Publication type:Master's thesis
Publication year:2014
Pages:xiii + 61      Language:   eng
Department/School:Sähkötekniikan korkeakoulu
Main subject:Biologinen tekniikka   (F3013)
Supervisor:Ilmoniemi, Risto
Instructor:Tillander, Matti
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201502211912
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  2654   | Archive
Keywords:deformable image registration
MR-only radiation therapy
prostate cancer
image processing
deformerbar bildregistrering
MR-baserad strålbehandling
prostatacancer
Abstract (eng):Radiation therapy (RT) planning in prostate cancer typically uses both CT images and T2-weighted MR images, for dose calculations and treatment volume delineation, respectively.
By using MRI to generate synthetic attenuation maps based on a T1-weighted, double-echo, gradient echo sequence with Dixon reconstruction (mDixon), CT imaging can be discarded from the planning process, and dose delivery uncertainties due to e.g. patient positioning and image registration errors decrease.
Multi-modal image registration may still be needed to ensure that the mDixon and T2-weighted images are aligned.

The aim of this thesis was to compare five deformable methods for this registration problem; the Demons algorithm, B-spline registration, a fast elastic image registration (FEIR) method, a locally affine hierarchical and a locally rigid hierarchical method.
The methods were evaluated qualitatively (visual assessment) and quantitatively for 19 cases.
In the quantitative analysis anatomical landmark accuracy, normalised cross-correlation of gradient images and the Dice similarity coefficient (DSC) of the bladder, prostate and seminal vesicles were used as evaluation metrics.

The results showed that in cases following the normal RT clinical work-flow, image alignment was good even without registration, but was improved with registration.
When intentional patient movement impaired the initial alignment, the benefit of image registration increased.
FEIR was the best method in terms of visual assessment, quantitative evaluation performance and computational speed, and seems well-suited for use in the MR-only radiotherapy work-flow for prostate cancer.
Abstract (swe):Planering av strålbehandling inom prostatacancer använder vanligtvis både CT bilder och T2-vägda MR bilder, för stråldosberäkningar respektive avgränsning av behandlingsvolymen.
Genom att använda MR för att generera syntetiska attenuationskartor baserat på en T1-vägd, dubbel-eko, gradient-eko sekvens med Dixon rekonstruktion (mDixon), kan CT slopas från planeringsprocessen, och stråldososäkerheter orsakade av t.ex. patientpositionering och felaktig bildregistrering minskar.
Multimodal bildregistrering kan ändå behövas för att försäkra att mDixon och den T2-vägda bilden är korrekt överlappande.

Målet med detta arbete var att jämföra fem deformerbara metoder för detta bildregistreringsproblem; Demons-algoritmen, B-spline registrering, en snabb elastisk bildregistreringsmetod (FEIR), en lokalt affin hierarkisk och en lokalt rigid hierarkisk metod.
Metoderna evaluerades kvalitativt (visuell bedömning) och kvantitativt i 19 fall.
I den kvantitativa analysen användes noggrannhet av anatomiska landmärken, normaliserad korskorrelation av gradientbilderna och Dice likhetskoefficient (DSC) för urinblåsan, prostatan och sädesblåsorna som evalueringskriterier.

Resultaten visade att i fall där det normala kliniska arbetsflödet för strålbehandling följdes var bildernas ursprungliga överlappning god även utan registrering, men förbättrades med registrering.
När patienten avsikligt rörde på sig för att försämra den ursprungliga överlappningen ökade fördelen med att använda bildregistrering.
FEIR var den bästa metoden med avseende på visuell bedömning, kvantitativ evaluering samt beräkningstid, och verkar väl lämpad för användning i det ett fullständigt MR-baserat arbetsflöde för strålbehandling av prostatacancer.
ED:2015-03-08
INSSI record number: 50641
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