tuesday seminar deformable image registration hyunseok lee [email protected] 07 th of january, 2014
TRANSCRIPT
Contents
• What is Image Registration?
• Deformable Image Registration– Basic concept– Algorithm– Products– Open source
• Debates about dose deform
• TG132
What is image registration?
• Image registration is the process of transforming different sets of data into one coordinate system.
• Registration is necessary in order to be able to compare or integrate the data obtained from differ-ent measurements.
IR – Rigid Transformation
• Rotation• Translation• Scale
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)sin()cos(
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2
22 y
xp
1
11 y
xp
2
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ss
2
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IR – Affine Transformation
• Rotation• Translation• Scale• Shear
– No more preservation of lengths and angles– Parallel lines are preserved
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1
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2
2
y
x
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y
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IR – Perspective Transformation
• (xo, yo, zo) world coordinates
• (xi, yi) image coordinates
fz
fxx
o
oi
fz
fyy
o
oi
IR – Projective Transformation
• (xp, yp) Plane Coordinates• (xi, yi) Image Coordinates
• amn coefficients from the equations of the scene and the image planes
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ppi
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IR – Non-Rigid Transformation
• Needed for inter-subject registration and distortion correction
• Non-linear
• Many different parameterizations
• Too much flexibility in the transformation can lead to undesirable results
Deformable Image Registration
• Fundamental task in medical image processing
• Typical uses– Longitudinal studies
• where temporal structural or anatomical changes are investi-gated
– Matching of images from different patients– Multi-modal registration
• matching images of the same patient acquired by different imaging technologies
DIR – Algorithm
Deformation Model
Optimization Method
Matching Criteria (Ob-jective Func-
tion)
DIR – Products
• MIM Software Inc.– Intensity-based free-form deformable registration
(VoxAlign)
– PET/CT, MR/CT and 4D data sets deformable fusion– Atlas-based auto-contouring– Dose Accumulation– Adaptive re-contouring– Deformable registration QA and reporting
Intensity-based Methods
• Intensity-based methods compare intensity patterns in images via correlation metrics
• Sum of Squared Differences• Normalized Cross-Correlation• Mutual Information
Feature-based Methods
• Feature-based methods find correspondence be-tween image features such as points, lines, and con-tours.
• Distance between corresponding points• Similarity metric between feature values
– e.g. curvature-based registration
Free-form Deformations
• The general idea is to deform an image by manipulating a regular grid of control points that are distributed across the image at an arbitrary mesh resolution.
• Control points can be moved and the position of individ-ual pixels between the control points is computed from the positions of surrounding control points.
DIR – Products
• Mirada Medical– Algorithms are based on published algorithms but
have been developed and optimized for particular RO use-cases and modality combinations.
• e.g. CT-CT Optic Flow algorithm for PET/CT fusion• e.g. CT-MR multi-modal algorithm for MRI fusion
– Multimodal deformable fusion• CT, PET, PET/CT, MRI and CBCT, including 4D data sets
– Automatic contouring• using an atlas or previously contoured case
– Dose warping and summation– Adaptive therapy
DIR – Products
• Velocity Medical Solutions– Multi-resolution modified basis spline algorithm– Multi-modality demons algorithm
– Multi-modality deformable image registration• CT, MR, PET and SPECT
– Atlas-based auto-contouring– Treatment response assessment
DIR – Open Source
• ITK– Insight Segmentation and Registration Toolkit– An extensive suite of software tools for image analysis– Implemented in C++– http://www.itk.org/itkindex.html
DIR – Open Source
• DIRART– Deformable Image Registration and Adaptive Radiotherapy– It contains well implemented DIR algorithms and the essen-
tial functions for ART applications.– Implemented in MATLAB– Need CERR– https://code.google.com/p/dirart/
DIR – Open Source
• Plastimatch– For high performance volumetric registration of medical
images– ITK-based algorithms for translation, rigid, affine,
demons, and B-spline registration• Some methods are GPU and multicore accelerated
– Implemented in C++– Plugin to 3D Slicer
• software package for visualization and medical image comput-ing
– http://plastimatch.org/
Debate about dose deform
It is not appropriate to “deform” dose along with DIR in ART
• For ART it is common to collect images of the patient throughout the course of therapy.
• Because of temporal variations, it is usually necessary to deform images so as to merge them into a cohesive dataset.
• This image registration makes the accurate merging of dose distri-butions difficult.
• Some have decided to do this by “deforming” the dose distributions, somewhat analogous to deforming the images, but it has been sug-gested that this is not appropriate.
Task Group No. 132
• Use of Image Registration and Fusion Algorithms and
Techniques in Radiotherapy
– Emphasis the importance of acceptance testing, including end-
to-end tests, phantom tests, and clinical data tests.
– Describe the methods for validation and quality assurance of im-
age registration techniques.
– Describe techniques for patient specific validation.
Deformable PRESAGE® dosimeter
Discussion & Question
Thank you for your attention
DIR – Algorithm
• Deformation Model
DIR – Algorithm
• Matching Criteria (Objective Function)
DIR – Algorithm
• Optimization Method