07th of January, 2014
Tuesday Seminar
Deformable Image Registration
HyunSeok Lee
leehseok@snu.ac.kr
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
different measurements.
IR – Rigid Transformation
• Rotation
• Translation
• Scale
 x1 

p1   
 y1 
 x2 

p2   
 y2 
 s1 

s1   
s2 
  

p 2  t  s R p1
 cos(  )  sin( )
R  

sin(

)
cos(

)


  t1 
t1   
t 2 
IR – Affine Transformation
•
•
•
•
Rotation
Translation
Scale
Shear
 x 2   a 13   a 11  a 12   x1 

  
 
y
a
a

a
y
22   1 
 2   23   21
– No more preservation of lengths and angles
– Parallel lines are preserved
IR – Perspective Transformation
• (xo, yo, zo)  world coordinates
• (xi, yi)  image coordinates
xi 
yi 
 fx o
zo  f
 fy o
zo  f
IR – Projective Transformation
• (xp, yp)  Plane Coordinates
• (xi, yi)  Image Coordinates
xi 
a11 x p  a12 y p  a13
a 31 x p  a 32 y p  a 33
yi 
a 21 x p  a 22 y p  a 23
a 31 x p  a 32 y p  a 33
• amn  coefficients from the equations of the
scene and the image planes
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
investigated
– Matching of images from different patients
– Multi-modal registration
• matching images of the same patient acquired by different
imaging technologies
DIR – Algorithm
Deformation
Model
Matching
Criteria
(Objective
Function)
Optimization
Method
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
between image features such as points, lines, and
contours.
• 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
individual 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
essential 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
computing
– 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
distributions difficult.
• Some have decided to do this by “deforming” the dose distributions,
somewhat analogous to deforming the images, but it has been
suggested 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 endto-end tests, phantom tests, and clinical data tests.
– Describe the methods for validation and quality assurance of
image 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