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# Tuesday Seminar Deformable Image Registration PowerPoint PPT Presentation

07 th 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?.

Tuesday Seminar Deformable Image Registration

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#### Presentation Transcript

07th of January, 2014

## Tuesday SeminarDeformable Image Registration

HyunSeok Lee

leehseok@snu.ac.kr

### Contents

• What is Image Registration?

• Deformable Image Registration

• Basic concept

• Algorithm

• Products

• Open source

• 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.

• Rotation

• Translation

• Scale

### IR – Affine Transformation

• Rotation

• Translation

• Scale

• Shear

• No more preservation of lengths and angles

• Parallel lines are preserved

### IR – Perspective Transformation

• (xo, yo, zo)  world coordinates

• (xi, yi)  image coordinates

### IR – Projective Transformation

• (xp, yp)  Plane Coordinates

• (xi, yi)  Image Coordinates

• 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 – 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

• 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

• 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

### 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

• It contains well implemented DIR algorithms and the essential functions for ART applications.

• Implemented in MATLAB

• Need CERR

### 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/

### 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.

• 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 image registration techniques.

• Describe techniques for patient specific validation.

### DIR – Algorithm

• Deformation Model

### DIR – Algorithm

• Matching Criteria (Objective Function)

### DIR – Algorithm

• Optimization Method