The ITK Software Guide Second Edition Updated for ITK version 2.4

nez Luis Iba Will Schroeder Lydia Ng Josh Cates and the Insight Software Consortium

November 21, 2005

http://www.itk.org Email: insight-users@itk.org

The purpose of computing is Insight, not numbers. Richard Hamming

Abstract

The Insight Toolkit (ITK) is an open-source software toolkit for performing registration and segmentation. Segmentation is the process of identifying and classifying data found in a digitally sampled representation. Typically the sampled representation is an image acquired from such medical instrumentation as CT or MRI scanners. Registration is the task of aligning or developing correspondences between data. For example, in the medical environment, a CT scan may be aligned with a MRI scan in order to combine the information contained in both. ITK is implemented in C++. It is cross-platform, using a build environment known as CMake to manage the compilation process in a platform-independent way. In addition, an automated wrapping process (Cable) generates interfaces between C++ and interpreted programming languages such as Tcl, Java, and Python. This enables developers to create software using a variety of programming languages. ITKs C++ implementation style is referred to as generic programming, which is to say that it uses templates so that the same code can be applied generically to any class or type that happens to support the operations used. Such C++ templating means that the code is highly efcient, and that many software problems are discovered at compile-time, rather than at run-time during program execution. Because ITK is an open-source project, developers from around the world can use, debug, maintain, and extend the software. ITK uses a model of software development referred to as Extreme Programming. Extreme Programming collapses the usual software creation methodology into a simultaneous and iterative process of design-implement-test-release. The key features of Extreme Programming are communication and testing. Communication among the members of the ITK community is what helps manage the rapid evolution of the software. Testing is what keeps the software stable. In ITK, an extensive testing process (using a system known as Dart) is in place that measures the quality on a daily basis. The ITK Testing Dashboard is posted continuously, reecting the quality of the software at any moment. This book is a guide to using and developing with ITK. The sample code in the directory provides a companion to the material presented here. The most recent version of this document is available online at http://www.itk.org/ItkSoftwareGuide.pdf .

Contributors

The Insight Toolkit (ITK) has been created by the efforts of many talented individuals and prestigious organizations. It is also due in great part to the vision of the program established by Dr. Terry Yoo and Dr. Michael Ackerman at the National Library of Medicine. This book lists a few of these contributors in the following paragraphs. Not all developers of ITK are credited here, so please visit the Web pages at http://www.itk.org/HTML/About.htm for the names of additional contributors, as well as checking the CVS source logs for code contributions. The following is a brief description of the contributors to this software guide and their contributions. is principal author of this text. He assisted in the design and layout of the text, Luis Ib anez A implemented the bulk of the L TEX and CMake build process, and was responsible for the bulk of the content. He also developed most of the example code found in the Insight/Examples directory. Will Schroeder helped design and establish the organization of this text and the Insight/Examples directory. He is principal content editor, and has authored several chapters. Lydia Ng authored the description for the registration framework and its components, the section on the multiresolution framework, and the section on deformable registration methods. She also edited the section on the resampling image lter and the sections on various level set segmentation algorithms. Joshua Cates authored the iterators chapter and the text and examples describing watershed segmentation. He also co-authored the level-set segmentation material. Jisung Kim authored the chapter on the statistics framework. Julien Jomier contributed the chapter on spatial objects and examples on model-based registration using spatial objects.

vi

Karthik Krishnan recongured the process for automatically generating images from all the examples. Added a large number of new examples and updated the Filtering and Segmentation chapters for the second edition. Stephen Aylward contributed material describing spatial objects and their application. Tessa Sundaram contributed the section on deformable registration using the nite element method. YinPeng Jin contributed the examples on hybrid segmentation methods. Celina Imielinska authored the section describing the principles of hybrid segmentation methods. Mark Foskey contributed the examples on the AutomaticTopologyMeshSource class. Mathieu Malaterre contributed the entire section on the description and use of DICOM readers and writers based on the GDCM library. He also contributed an example on the use of the VTKImageIO class. Gavin Baker contributed the section on how to write composite lters. Also known as minipipeline lters.

CONTENTS

I Introduction1 Welcome 1.1 1.2 1.3 Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . How to Learn ITK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Software Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.1 1.4 Obtaining the Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13 3 4 4 4 5 6 6 6 7 9 9

Downloading ITK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.1 1.4.2 1.4.3 1.4.4 1.4.5 1.4.6 Downloading Packaged Releases . . . . . . . . . . . . . . . . . . . . . . . . . . Downloading from CVS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Join the Mailing List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Directory Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.5 1.6

The Insight Community and Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 A Brief History of ITK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 13

2 Installation 2.1

Conguring ITK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.1.1 2.1.2 Preparing CMake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Conguring ITK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.2

Getting Started With ITK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

viii

Contents

2.2.1

Hello World ! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 19

3 System Overview 3.1 3.2

System Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Essential System Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 3.2.6 3.2.7 Generic Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Include Files and Class Denitions . . . . . . . . . . . . . . . . . . . . . . . . . 21 Object Factories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Smart Pointers and Memory Management . . . . . . . . . . . . . . . . . . . . . 22 Error Handling and Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Event Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Multi-Threading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.3 3.4 3.5 3.6 3.7

Numerics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Data Representation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Data Processing Pipeline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Spatial Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Wrapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

II Users Guide4 DataRepresentation 4.1

3335

Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 4.1.1 4.1.2 4.1.3 4.1.4 4.1.5 4.1.6 4.1.7 Creating an Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Reading an Image from a File . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Accessing Pixel Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Dening Origin and Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 RGB Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Vector Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Importing Image Data from a Buffer . . . . . . . . . . . . . . . . . . . . . . . . 46

4.2

PointSet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 4.2.1 4.2.2 4.2.3 Creating a PointSet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Getting Access to Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Getting Access to Data in Points . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Contents

ix

4.2.4 4.2.5 4.2.6 4.3

RGB as Pixel Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Vectors as Pixel Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Normals as Pixel Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.3.1 4.3.2 4.3.3 4.3.4 4.3.5 4.3.6 4.3.7 4.3.8 4.3.9 4.3.10 Creating a Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Inserting Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Managing Data in Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Customizing the Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Topology and the K-Complex . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Representing a PolyLine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Simplifying Mesh Creation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Iterating Through Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Visiting Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 More on Visiting Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

4.4

Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 4.4.1 Creating a PolyLineParametricPath . . . . . . . . . . . . . . . . . . . . . . . . . 95

4.5

Containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 101

5 Spatial Objects 5.1 5.2 5.3 5.4 5.5

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 SpatialObject Tree Container . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Transformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 Types of Spatial Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 5.5.1 5.5.2 5.5.3 5.5.4 5.5.5 5.5.6 5.5.7 5.5.8 ArrowSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 BlobSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 CylinderSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 EllipseSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 GaussianSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 GroupSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 ImageSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 ImageMaskSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

x

Contents

5.5.9 5.5.10 5.5.11 5.5.12 5.5.13

LandmarkSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 LineSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 MeshSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 SurfaceSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 TubeSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 VesselTubeSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 DTITubeSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

5.6 5.7 5.8

SceneSpatialObject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 Read/Write SpatialObjects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 Statistics Computation via SpatialObjects . . . . . . . . . . . . . . . . . . . . . . . . . . 136 139

6 Filtering 6.1

Thresholding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 6.1.1 6.1.2 Binary Thresholding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 General Thresholding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

6.2

Edge Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 6.2.1 Canny Edge Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

6.3

Casting and Intensity Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 6.3.1 6.3.2 Linear Mappings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 Non Linear Mappings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

6.4

Gradients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 6.4.1 6.4.2 6.4.3 Gradient Magnitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 Gradient Magnitude With Smoothing . . . . . . . . . . . . . . . . . . . . . . . 153 Derivative Without Smoothing . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

6.5

Second Order Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 6.5.1 6.5.2 Second Order Recursive Gaussian . . . . . . . . . . . . . . . . . . . . . . . . . 158 Laplacian Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 Laplacian Filter Finite Difference . . . . . . . . . . . . . . . . . . . . . . . . . . 162 Laplacian Filter Recursive Gaussian . . . . . . . . . . . . . . . . . . . . . . . . . 162

6.6

Neighborhood Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 6.6.1 6.6.2 Mean Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 Median Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

Contents

xi

6.6.3

Mathematical Morphology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 Binary Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 Grayscale Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

6.6.4

Voting Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 Binary Median Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 Hole Filling Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 Iterative Hole Filling Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

6.7

Smoothing Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 6.7.1 Blurring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 Discrete Gaussian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 Binomial Blurring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 Recursive Gaussian IIR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 6.7.2 Local Blurring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 Gaussian Blur Image Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 6.7.3 Edge Preserving Smoothing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 Introduction to Anisotropic Diffusion . . . . . . . . . . . . . . . . . . . . . . . . 194 Gradient Anisotropic Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 Curvature Anisotropic Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 Curvature Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 MinMaxCurvature Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 Bilateral Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 6.7.4 Edge Preserving Smoothing in Vector Images . . . . . . . . . . . . . . . . . . . 207 Vector Gradient Anisotropic Diffusion . . . . . . . . . . . . . . . . . . . . . . . . 208 Vector Curvature Anisotropic Diffusion . . . . . . . . . . . . . . . . . . . . . . . 209 6.7.5 Edge Preserving Smoothing in Color Images . . . . . . . . . . . . . . . . . . . 211 Gradient Anisotropic Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 Curvature Anisotropic Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

6.8 6.9

Distance Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 Geometric Transformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 6.9.1 6.9.2 6.9.3 Filters You Should be Afraid to Use . . . . . . . . . . . . . . . . . . . . . . . . 220 Change Information Image Filter . . . . . . . . . . . . . . . . . . . . . . . . . . 220 Flip Image Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

xii

Contents

6.9.4

Resample Image Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 Importance of Spacing and Origin . . . . . . . . . . . . . . . . . . . . . . . . . . 228 A Complete Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 Rotating an Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 Rotating and Scaling an Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Resampling using a deformation eld . . . . . . . . . . . . . . . . . . . . . . . . 242 Subsampling and image in the same space . . . . . . . . . . . . . . . . . . . . . . 244 Resampling an Anisotropic image to make it Isotropic . . . . . . . . . . . . . . . 247

6.10 Frequency Domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 6.10.1 6.10.2 Computing a Fast Fourier Transform (FFT) . . . . . . . . . . . . . . . . . . . . 253 Filtering on the Frequency Domain . . . . . . . . . . . . . . . . . . . . . . . . . 256

6.11 Extracting Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 6.11.1 Surface extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 263

7 Reading and Writing Images 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8

Basic Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 Pluggable Factories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 Using ImageIO Classes Explicitly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 Reading and Writing RGB Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 Reading, Casting and Writing Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270 Extracting Regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 Extracting Slices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 Reading and Writing Vector Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 7.8.1 7.8.2 7.8.3 The Minimal Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 Producing and Writing Covariant Images . . . . . . . . . . . . . . . . . . . . . 279 Reading Covariant Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

7.9

Reading and Writing Complex Images . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 . . . . . . . . . . . . . . . . . . . . . . . . 284

7.10 Extracting Components from Vector Images

7.11 Reading and Writing Image Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 7.11.1 7.11.2 Reading Image Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 Writing Image Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289

Contents

xiii

7.11.3

Reading and Writing Series of RGB Images . . . . . . . . . . . . . . . . . . . . 291

7.12 Reading and Writing DICOM Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 7.12.1 7.12.2 7.12.3 7.12.4 7.12.5 7.12.6 7.12.7 8 Registration 8.1 8.2 8.3 Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 Reading and Writing a 2D Image . . . . . . . . . . . . . . . . . . . . . . . . . . 295 Reading a 2D DICOM Series and Writing a Volume . . . . . . . . . . . . . . . . 298 Reading a 2D DICOM Series and Writing a 2D DICOM Series . . . . . . . . . . 302 Printing DICOM Tags From One Slice . . . . . . . . . . . . . . . . . . . . . . . 305 Printing DICOM Tags From a Series . . . . . . . . . . . . . . . . . . . . . . . . 308 Changing a DICOM Header . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 315

Registration Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 Hello World Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316 Features of the Registration Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . 324 8.3.1 8.3.2 Direction of the Transform Mapping . . . . . . . . . . . . . . . . . . . . . . . . 327 Registration is done in physical space . . . . . . . . . . . . . . . . . . . . . . . 328

8.4 8.5

Monitoring Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328 Multi-Modality Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 8.5.1 8.5.2 8.5.3 Viola-Wells Mutual Information . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Mattes Mutual Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 Plotting joint histograms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345

8.6

Centered Transforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 8.6.1 8.6.2 8.6.3 8.6.4 8.6.5 Rigid Registration in 2D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 Initializing with Image Moments . . . . . . . . . . . . . . . . . . . . . . . . . . 355 Similarity Transform in 2D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364 Rigid Transform in 3D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 Centered Afne Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374

8.7

Multi-Resolution Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 8.7.1 8.7.2 Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 Parameter Tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386

8.8

Transforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392 8.8.1 Geometrical Representation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392

xiv

Contents

8.8.2 8.8.3 8.8.4 8.8.5 8.8.6 8.8.7 8.8.8 8.8.9 8.8.10 8.8.11 8.8.12 8.8.13 8.8.14 8.8.15 8.8.16 8.8.17 8.8.18 8.9

Transform General Properties

. . . . . . . . . . . . . . . . . . . . . . . . . . . 395

Identity Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 Translation Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 Scale Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 Scale Logarithmic Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398 Euler2DTransform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398 CenteredRigid2DTransform . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399 Similarity2DTransform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400 QuaternionRigidTransform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401 VersorTransform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402 VersorRigid3DTransform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403 Euler3DTransform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404 Similarity3DTransform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 Rigid3DPerspectiveTransform . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 AfneTransform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 BSplineDeformableTransform . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 KernelTransforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409

Interpolators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410 8.9.1 8.9.2 8.9.3 8.9.4 Nearest Neighbor Interpolation . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 Linear Interpolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 B-Spline Interpolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 Windowed Sinc Interpolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412

8.10 Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 8.10.1 Mean Squares Metric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 Exploring a Metric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 8.10.2 8.10.3 8.10.4 Normalized Correlation Metric . . . . . . . . . . . . . . . . . . . . . . . . . . . 419 Mean Reciprocal Square Differences . . . . . . . . . . . . . . . . . . . . . . . . 419 Mutual Information Metric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420 Parzen Windowing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420 Viola and Wells Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 Mattes et al. Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422 8.10.5 Kullback-Leibler distance metric . . . . . . . . . . . . . . . . . . . . . . . . . . 422

Contents

xv

8.10.6 8.10.7 8.10.8 8.10.9

Normalized Mutual Information Metric . . . . . . . . . . . . . . . . . . . . . . 423 Mean Squares Histogram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423 Correlation Coefcient Histogram . . . . . . . . . . . . . . . . . . . . . . . . . 424 Cardinality Match Metric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424

8.10.10 Kappa Statistics Metric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424 8.10.11 Gradient Difference Metric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425 8.11 Optimizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426 8.11.1 8.11.2 8.11.3 8.11.4 Registration using Match Cardinality metric . . . . . . . . . . . . . . . . . . . . 429 Registration using the One plus One Evolutionary Optimizer . . . . . . . . . . . 431 Registration using masks constructed with Spatial objects . . . . . . . . . . . . . 432 Rigid registrations incorporating prior knowledge . . . . . . . . . . . . . . . . . 434

8.12 Image Pyramids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437 8.13 Deformable Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 8.14 Demons Deformable Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461 8.15 Visualizing Deformation elds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469 8.15.1 8.15.2 Visualizing 2D deformation elds . . . . . . . . . . . . . . . . . . . . . . . . . 470 Visualizing 3D deformation elds . . . . . . . . . . . . . . . . . . . . . . . . . 470

8.16 Model Based Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476 8.17 Point Set Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488 9 Segmentation 9.1 503

Region Growing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503 9.1.1 9.1.2 9.1.3 9.1.4 Connected Threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504 Otsu Segmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507 Neighborhood Connected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 Condence Connected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514 Application of the Condence Connected lter on the Brain Web Data . . . . . . . 517 9.1.5 9.1.6 Isolated Connected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 518 Condence Connected in Vector Images . . . . . . . . . . . . . . . . . . . . . . 521

9.2

Segmentation Based on Watersheds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524 9.2.1 9.2.2 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524 Using the ITK Watershed Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . 527

xvi

Contents

9.3

Level Set Segmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531 9.3.1 9.3.2 9.3.3 9.3.4 9.3.5 9.3.6 9.3.7 Fast Marching Segmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533 Shape Detection Segmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . 541 Geodesic Active Contours Segmentation . . . . . . . . . . . . . . . . . . . . . . 550 Threshold Level Set Segmentation . . . . . . . . . . . . . . . . . . . . . . . . . 555 Canny-Edge Level Set Segmentation . . . . . . . . . . . . . . . . . . . . . . . . 559 Laplacian Level Set Segmentation . . . . . . . . . . . . . . . . . . . . . . . . . 563 Geodesic Active Contours Segmentation With Shape Guidance . . . . . . . . . . 565

9.4

Hybrid Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 9.4.1 9.4.2 9.4.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 Fuzzy Connectedness and Condence Connectedness . . . . . . . . . . . . . . 577

Fuzzy Connectedness and Voronoi Classication . . . . . . . . . . . . . . . . . 580 Example of a Hybrid Segmentation Method . . . . . . . . . . . . . . . . . . . . . 581

9.4.4

Deformable Models and Gibbs Prior . . . . . . . . . . . . . . . . . . . . . . . . 587 Deformable Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 587 Gibbs Prior Image Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594

9.5

Feature Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 596 9.5.1 Hough Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 596 Line Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 596 Circle Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600

10 Statistics

605

10.1 Data Containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605 10.1.1 10.1.2 Sample Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605 Sample Adaptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608 ImageToListAdaptor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608 PointSetToListAdaptor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 610 10.1.3 10.1.4 10.1.5 10.1.6 10.1.7 Histogram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613 Subsample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 616 MembershipSample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 619 MembershipSampleGenerator . . . . . . . . . . . . . . . . . . . . . . . . . . . 622 K-d Tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625

Contents

xvii

10.2 Algorithms and Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 629 10.2.1 Sample Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 630 Mean and Covariance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 630 Weighted Mean and Covariance . . . . . . . . . . . . . . . . . . . . . . . . . . . 632 10.2.2 Sample Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 635 ListSampleToHistogramFilter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 635 ListSampleToHistogramGenerator . . . . . . . . . . . . . . . . . . . . . . . . . . 637 NeighborhoodSampler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 639 SampleToHistogramProjectionFilter . . . . . . . . . . . . . . . . . . . . . . . . . 640 10.2.3 10.2.4 Sample Sorting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643 Probability Density Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 646 Gaussian Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646 10.2.5 Distance Metric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647 Euclidean Distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647 10.2.6 Decision Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649 Maximum Decision Rule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649 Minimum Decision Rule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650 Maximum Ratio Decision Rule . . . . . . . . . . . . . . . . . . . . . . . . . . . 651 10.2.7 Random Variable Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 652 Normal (Gaussian) Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . 652 10.3 Statistics applied to Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 652 10.3.1 Image Histograms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 652 Scalar Image Histogram with Adaptor . . . . . . . . . . . . . . . . . . . . . . . . 652 Scalar Image Histogram with Generator . . . . . . . . . . . . . . . . . . . . . . . 655 Color Image Histogram with Generator . . . . . . . . . . . . . . . . . . . . . . . 657 Color Image Histogram Writing . . . . . . . . . . . . . . . . . . . . . . . . . . . 660 10.3.2 Image Information Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 663 Computing Image Entropy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 663 Computing Images Mutual Information . . . . . . . . . . . . . . . . . . . . . . . 667 10.4 Classication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 672 10.4.1 10.4.2 k-d Tree Based k-Means Clustering . . . . . . . . . . . . . . . . . . . . . . . . 673 K-Means Classication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 679

xviii

Contents

10.4.3 10.4.4 10.4.5

Bayesian Plug-In Classier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 681 Expectation Maximization Mixture Model Estimation . . . . . . . . . . . . . . . 688 Classication using Markov Random Field . . . . . . . . . . . . . . . . . . . . 691

III Developers Guide11 Iterators

699701

11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701 11.2 Programming Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702 11.2.1 11.2.2 11.2.3 11.2.4 Creating Iterators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702 Moving Iterators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702 Accessing Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 704 Iteration Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 705

11.3 Image Iterators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 706 11.3.1 11.3.2 11.3.3 11.3.4 11.3.5 ImageRegionIterator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 706 ImageRegionIteratorWithIndex . . . . . . . . . . . . . . . . . . . . . . . . . . . 708 ImageLinearIteratorWithIndex . . . . . . . . . . . . . . . . . . . . . . . . . . . 710 ImageSliceIteratorWithIndex . . . . . . . . . . . . . . . . . . . . . . . . . . . . 715 ImageRandomConstIteratorWithIndex . . . . . . . . . . . . . . . . . . . . . . . 719

11.4 Neighborhood Iterators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 720 11.4.1 NeighborhoodIterator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726 Basic neighborhood techniques: edge detection . . . . . . . . . . . . . . . . . . . 726 Convolution ltering: Sobel operator . . . . . . . . . . . . . . . . . . . . . . . . 730 Optimizing iteration speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 731 Separable convolution: Gaussian ltering . . . . . . . . . . . . . . . . . . . . . . 733 Slicing the neighborhood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 735 Random access iteration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 736 11.4.2 ShapedNeighborhoodIterator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 738 Shaped neighborhoods: morphological operations . . . . . . . . . . . . . . . . . . 739 12 Image Adaptors 745

12.1 Image Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 746 12.2 Adapting RGB Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 748

Contents

xix

12.3 Adapting Vector Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 751 12.4 Adaptors for Simple Computation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 753 12.5 Adaptors and Writers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 755 13 How To Write A Filter 757

13.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 757 13.2 Overview of Filter Creation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 758 13.3 Streaming Large Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 759 13.3.1 13.3.2 Overview of Pipeline Execution . . . . . . . . . . . . . . . . . . . . . . . . . . 760 Details of Pipeline Execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . 762 UpdateOutputInformation() . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 762 PropagateRequestedRegion() . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 763 UpdateOutputData() . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 764 13.4 Threaded Filter Execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 764 13.5 Filter Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 765 13.5.1 13.5.2 Optional . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 766 Useful Macros . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 766

13.6 How To Write A Composite Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767 13.6.1 13.6.2 Implementing a Composite Filter . . . . . . . . . . . . . . . . . . . . . . . . . . 767 A Simple Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 768 773

14 Software Process

14.1 CVS Source Code Repository . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773 14.2 DART Regression Testing System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 774 14.3 Working The Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 776 14.4 The Effectiveness of the Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 776 Index 785

LIST OF FIGURES

2.1 4.1 4.2 5.1 5.2 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9

Cmake user interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 ITK Image Geometrical Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 PointSet with Vectors as PixelType . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 SpatialObject Transformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 SpatialObject Transform Computations . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 BinaryThresholdImageFilter transfer function . . . . . . . . . . . . . . . . . . . . . . . . 140 BinaryThresholdImageFilter output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 ThresholdImageFilter using the threshold-below mode. . . . . . . . . . . . . . . . . . . . 143 ThresholdImageFilter using the threshold-above mode . . . . . . . . . . . . . . . . . . . 143 ThresholdImageFilter using the threshold-outside mode . . . . . . . . . . . . . . . . . . . 143 Sigmoid Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 Effect of the Sigmoid lter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 GradientMagnitudeImageFilter output . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 GradientMagnitudeRecursiveGaussianImageFilter output . . . . . . . . . . . . . . . . . . 156

6.10 Effect of the Derivative lter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 6.11 Output of the LaplacianRecursiveGaussianImageFilter. . . . . . . . . . . . . . . . . . . . 166 6.12 Output of the LaplacianRecursiveGaussianImageFilter. . . . . . . . . . . . . . . . . . . . 168 6.13 Effect of the MedianImageFilter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 6.14 Effect of the Median lter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

xxii

List of Figures

6.15 Effect of erosion and dilation in a binary image. . . . . . . . . . . . . . . . . . . . . . . . 175 6.16 Effect of erosion and dilation in a grayscale image. . . . . . . . . . . . . . . . . . . . . . 177 6.17 Effect of the BinaryMedian lter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 6.18 Effect of many iterations on the BinaryMedian lter. . . . . . . . . . . . . . . . . . . . . 180 6.19 Effect of the VotingBinaryHoleFilling lter. . . . . . . . . . . . . . . . . . . . . . . . . . 183 6.20 Effect of the VotingBinaryIterativeHoleFilling lter. . . . . . . . . . . . . . . . . . . . . . 186 6.21 DiscreteGaussianImageFilter Gaussian diagram. . . . . . . . . . . . . . . . . . . . . . . . 187 6.22 DiscreteGaussianImageFilter output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 6.23 BinomialBlurImageFilter output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 6.24 Output of the SmoothingRecursiveGaussianImageFilter. . . . . . . . . . . . . . . . . . . 193

6.25 GradientAnisotropicDiffusionImageFilter output . . . . . . . . . . . . . . . . . . . . . . 197 6.26 CurvatureAnisotropicDiffusionImageFilter output . . . . . . . . . . . . . . . . . . . . . . 199 6.27 CurvatureFlowImageFilter output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 6.28 MinMaxCurvatureFlow computation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 6.29 MinMaxCurvatureFlowImageFilter output . . . . . . . . . . . . . . . . . . . . . . . . . . 205 6.30 BilateralImageFilter output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 6.31 VectorGradientAnisotropicDiffusionImageFilter output . . . . . . . . . . . . . . . . . . . 210 6.32 VectorCurvatureAnisotropicDiffusionImageFilter output . . . . . . . . . . . . . . . . . . 212 6.33 VectorGradientAnisotropicDiffusionImageFilter on RGB . . . . . . . . . . . . . . . . . . 214 6.34 VectorCurvatureAnisotropicDiffusionImageFilter output on RGB . . . . . . . . . . . . . . 216 6.35 Various Anisotropic Diffusion compared . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 6.36 DanielssonDistanceMapImageFilter output . . . . . . . . . . . . . . . . . . . . . . . . . 218 6.37 SignedDanielssonDistanceMapImageFilter output . . . . . . . . . . . . . . . . . . . . . . 220 6.38 Effect of the MedianImageFilter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 6.39 Effect of the Resample lter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 6.40 Analysis of resampling in common coordinate system . . . . . . . . . . . . . . . . . . . . 226 6.41 ResampleImageFilter with a translation by (30, 50) . . . . . . . . . . . . . . . . . . . 226 6.42 ResampleImageFilter. Analysis of a translation by (30, 50) . . . . . . . . . . . . . . . 227 6.43 ResampleImageFilter highlighting image borders . . . . . . . . . . . . . . . . . . . . . . 228 6.44 ResampleImageFilter selecting the origin of the output image . . . . . . . . . . . . . . . . 230 6.45 ResampleImageFilter selecting the origin of the output image . . . . . . . . . . . . . . . . 230 6.46 ResampleImageFilter selecting the origin of the input image . . . . . . . . . . . . . . . . 231

List of Figures

xxiii

6.47 ResampleImageFilter use of naive viewers . . . . . . . . . . . . . . . . . . . . . . . . . . 232 6.48 ResampleImageFilter and output image spacing . . . . . . . . . . . . . . . . . . . . . . . 233 6.49 ResampleImageFilter naive viewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 6.50 ResampleImageFilter with non-unit spacing . . . . . . . . . . . . . . . . . . . . . . . . . 235 6.51 Effect of a rotation on the resampling lter. . . . . . . . . . . . . . . . . . . . . . . . . . 236 6.52 Input and output image placed in a common reference system . . . . . . . . . . . . . . . . 236 6.53 Effect of the Resample lter rotating an image . . . . . . . . . . . . . . . . . . . . . . . . 239 6.54 Effect of the Resample lter rotating and scaling an image . . . . . . . . . . . . . . . . . 242 7.1 7.2 7.3 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 Collaboration diagram of the ImageIO classes . . . . . . . . . . . . . . . . . . . . . . . . 265 Use cases of ImageIO factories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 Class diagram of ImageIO factories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 Image Registration Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315

Registration Framework Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316 Fixed and Moving images in registration framework . . . . . . . . . . . . . . . . . . . . . 321 HelloWorld registration output images . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 Pipeline structure of the registration example . . . . . . . . . . . . . . . . . . . . . . . . 323 Trace of translations and metrics during registration . . . . . . . . . . . . . . . . . . . . . 325 Registration Coordinate Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326 Command/Observer and the Registration Framework . . . . . . . . . . . . . . . . . . . . 331 Multi-Modality Registration Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338

8.10 Multi-Modality Registration outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 8.11 Multi-Modality Registration plot of translations . . . . . . . . . . . . . . . . . . . . . . . 339 8.12 Multi-Modality Registration plot of metrics . . . . . . . . . . . . . . . . . . . . . . . . . 339 8.13 MattesMutualInformationImageToImageMetric output images . . . . . . . . . . . . . . . 343 8.14 MattesMutualInformationImageToImageMetric output plots . . . . . . . . . . . . . . . . 343 8.15 MattesMutualInformationImageToImageMetric number of bins . . . . . . . . . . . . . . . 344 8.16 Multi-modality joint histograms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 8.17 Rigid2D Registration input images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353 8.18 Rigid2D Registration output images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353 8.19 Rigid2D Registration output plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 8.20 Rigid2D Registration input images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356

xxiv

List of Figures

8.21 Rigid2D Registration output images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356 8.22 Rigid2D Registration output plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 8.23 Effect of changing the center of rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . 361 8.24 CenteredTransformInitializer input images . . . . . . . . . . . . . . . . . . . . . . . . . . 362 8.25 CenteredTransformInitializer output images . . . . . . . . . . . . . . . . . . . . . . . . . 362 8.26 CenteredTransformInitializer output plots . . . . . . . . . . . . . . . . . . . . . . . . . . 363 8.27 Fixed and Moving image registered with CenteredSimilarity2DTransform . . . . . . . . . 367 8.28 Output of the CenteredSimilarity2DTransform registration . . . . . . . . . . . . . . . . . 367 8.29 CenteredSimilarity2DTransform registration plots . . . . . . . . . . . . . . . . . . . . . . 368 8.30 CenteredTransformInitializer input images . . . . . . . . . . . . . . . . . . . . . . . . . . 372 8.31 CenteredTransformInitializer output images . . . . . . . . . . . . . . . . . . . . . . . . . 373 8.32 CenteredTransformInitializer output plots . . . . . . . . . . . . . . . . . . . . . . . . . . 373 8.33 AfneTransform registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 8.34 AfneTransform output images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 8.35 AfneTransform output plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 8.36 Multi-Resolution Registration Components . . . . . . . . . . . . . . . . . . . . . . . . . 380 8.37 Conceptual representation of Multi-Resolution registration . . . . . . . . . . . . . . . . . 381 8.38 Multi-Resolution registration input images . . . . . . . . . . . . . . . . . . . . . . . . . . 386 8.39 Multi-Resolution registration output images . . . . . . . . . . . . . . . . . . . . . . . . . 387 8.40 Multi-Resolution Registration Input Images . . . . . . . . . . . . . . . . . . . . . . . . . 390 8.41 Multi-Resolution Registration output plots . . . . . . . . . . . . . . . . . . . . . . . . . . 391 8.42 Geometrical representation objects in ITK . . . . . . . . . . . . . . . . . . . . . . . . . . 392 8.43 Mapping moving image to xed image in Registration . . . . . . . . . . . . . . . . . . . 410 8.44 Need for interpolation in Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410 8.45 BSpline Interpolation Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 8.46 Mean Squares Metric Plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418 8.47 Parzen Windowing in Mutual Information . . . . . . . . . . . . . . . . . . . . . . . . . . 421 8.48 Class diagram of the Optimizer hierarchy . . . . . . . . . . . . . . . . . . . . . . . . . . 427 8.49 FEM-based deformable registration results . . . . . . . . . . . . . . . . . . . . . . . . . . 438 8.50 Demons deformable registration output . . . . . . . . . . . . . . . . . . . . . . . . . . . 447 8.51 Demons deformable registration output . . . . . . . . . . . . . . . . . . . . . . . . . . . 465 8.52 Demons deformable registration output . . . . . . . . . . . . . . . . . . . . . . . . . . . 469

List of Figures

xxv

8.53 Deformation eld magnitudes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471 8.54 Calculator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471 8.55 Visualized Def eld . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472 8.56 Visualized Def eld4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473 8.57 Deformation eld output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475 8.58 Difference image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475 8.59 Model to Image Registration Framework Components . . . . . . . . . . . . . . . . . . . . 476 8.60 Model to Image Registration Framework Concept . . . . . . . . . . . . . . . . . . . . . . 477 8.61 SpatialObject to Image Registration results . . . . . . . . . . . . . . . . . . . . . . . . . 487 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9 ConnectedThreshold segmentation results . . . . . . . . . . . . . . . . . . . . . . . . . . 507 OtsuThresholdImageFilter output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 NeighborhoodConnected segmentation results . . . . . . . . . . . . . . . . . . . . . . . 513

CondenceConnected segmentation results . . . . . . . . . . . . . . . . . . . . . . . . . 517 3DregionGrowingScreenshot1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 518 3DregionGrowingScreenshot1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 518 IsolatedConnected segmentation results . . . . . . . . . . . . . . . . . . . . . . . . . . . 521 VectorCondenceConnected segmentation results . . . . . . . . . . . . . . . . . . . . . . 523 Watershed Catchment Basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525

9.10 Watersheds Hierarchy of Regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526 9.11 Watersheds lter composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526 9.12 Watershed segmentation output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 9.13 Zero Set Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531 9.14 Grid position of the embedded level-set surface. . . . . . . . . . . . . . . . . . . . . . . . 532 9.15 FastMarchingImageFilter collaboration diagram . . . . . . . . . . . . . . . . . . . . . . . 533 9.16 FastMarchingImageFilter intermediate output . . . . . . . . . . . . . . . . . . . . . . . . 540 9.17 FastMarchingImageFilter segmentations . . . . . . . . . . . . . . . . . . . . . . . . . . . 541 9.18 ShapeDetectionLevelSetImageFilter collaboration diagram . . . . . . . . . . . . . . . . . 542 9.19 ShapeDetectionLevelSetImageFilter intermediate output . . . . . . . . . . . . . . . . . . 549 9.20 ShapeDetectionLevelSetImageFilter segmentations . . . . . . . . . . . . . . . . . . . . . 550 9.21 GeodesicActiveContourLevelSetImageFilter collaboration diagram . . . . . . . . . . . . . 551 9.22 GeodesicActiveContourLevelSetImageFilter intermediate output . . . . . . . . . . . . . . 554

xxvi

List of Figures

9.23 GeodesicActiveContourImageFilter segmentations . . . . . . . . . . . . . . . . . . . . . 555 9.24 ThresholdSegmentationLevelSetImageFilter collaboration diagram . . . . . . . . . . . . . 556 9.25 Propagation term for threshold-based level set segmentation . . . . . . . . . . . . . . . . 556 9.26 ThresholdSegmentationLevelSet segmentations . . . . . . . . . . . . . . . . . . . . . . . 558 9.27 CannySegmentationLevelSetImageFilter collaboration diagram . . . . . . . . . . . . . . . 560 9.28 Segmentation results of CannyLevelSetImageFilter . . . . . . . . . . . . . . . . . . . . . 562 9.29 LaplacianSegmentationLevelSetImageFilter collaboration diagram . . . . . . . . . . . . . 563 9.30 Segmentation results of LaplacianLevelSetImageFilter . . . . . . . . . . . . . . . . . . . 566 9.31 GeodesicActiveContourShapePriorLevelSetImageFilter collaboration diagram . . . . . . . 567 9.32 GeodesicActiveContourShapePriorImageFilter input image and initial model . . . . . . . 575 9.33 Corpus callosum PCA modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 576 9.34 GeodesicActiveContourShapePriorImageFilter segmentations . . . . . . . . . . . . . . . . 576 9.35 Hybrid Segmentation Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581 9.36 FuzzyConectedness Filter Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581 9.37 Fuzzy Connectedness Segmentation Diagram . . . . . . . . . . . . . . . . . . . . . . . . 582 9.38 Voronoi Filter class diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582 9.39 Voronoi Diagram Filter classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582 9.40 Voronoi Diagram Segmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582 9.41 Fuzzy Connectedness and Voronoi Diagram Classication . . . . . . . . . . . . . . . . . 583 9.42 Fuzzy Connectedness, Voronoi diagram, and Deformable Models . . . . . . . . . . . . . . 583 9.43 Segmentation results for the hybrid segmentation approach . . . . . . . . . . . . . . . . . 585 9.44 Segmentation result for the hybrid segmentation approach . . . . . . . . . . . . . . . . . . 585 9.45 Deformable model collaboration diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 588 10.1 Sample class inheritance tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 606 10.2 Histogram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 614 10.3 Simple conceptual classier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 672 10.4 Statistical classication framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 673 10.5 Two normal distributions plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 676 10.6 Output of the KMeans classier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 682 10.7 Bayesian plug-in classier for two Gaussian classes . . . . . . . . . . . . . . . . . . . . . 683 10.8 Output of the ScalarImageMarkovRandomField . . . . . . . . . . . . . . . . . . . . . . . 697

List of Figures

xxvii

11.1 ITK image iteration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703 11.2 Copying an image subregion using ImageRegionIterator . . . . . . . . . . . . . . . . . . 709 11.3 Using the ImageRegionIteratorWithIndex . . . . . . . . . . . . . . . . . . . . . . . . . . 711 11.4 Maximum intensity projection using ImageSliceIteratorWithIndex . . . . . . . . . . . . . 719 11.5 Neighborhood iterator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 721 11.6 Some possible neighborhood iterator shapes . . . . . . . . . . . . . . . . . . . . . . . . . 722 11.7 Sobel edge detection results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 729 11.8 Gaussian blurring by convolution ltering . . . . . . . . . . . . . . . . . . . . . . . . . . 734 11.9 Finding local minima . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 738 11.10Binary image morphology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 743 12.1 ImageAdaptor concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 746 12.2 Image Adaptor to RGB Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 750 12.3 Image Adaptor to Vector Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 753 12.4 Image Adaptor for performing computations . . . . . . . . . . . . . . . . . . . . . . . . . 755 13.1 Relationship between DataObjects and ProcessObjects . . . . . . . . . . . . . . . . . . . 758 13.2 The Data Pipeline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 760 13.3 Sequence of the Data Pipeline updating mechanism . . . . . . . . . . . . . . . . . . . . . 761 13.4 Composite Filter Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767 13.5 Composite Filter Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 768 14.1 Dart Quality Dashboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 774

LIST OF TABLES

8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9

Geometrical Elementary Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 Identity Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 Translation Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 Scale Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397 Scale Logarithmic Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . 398 Euler2D Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399 CenteredRigid2D Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 400 Similarity2D Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 401 QuaternionRigid Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 402

8.10 Versor Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403 8.11 Versor Rigid3D Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 403 8.12 Euler3D Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404 8.13 Similarity3D Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 8.14 Rigid3DPerspective Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . 406 8.15 Afne Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 8.16 BSpline Deformable Transform Characteristics . . . . . . . . . . . . . . . . . . . . . . . 408 8.17 LBFGS Optimizer trace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474 9.1 9.2 9.3 ConnectedThreshold example parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 506 IsolatedConnectedImageFilter example parameters . . . . . . . . . . . . . . . . . . . . . 520 FastMarching segmentation example parameters . . . . . . . . . . . . . . . . . . . . . . . 539

xxx

List of Tables

9.4 9.5 9.6

ShapeDetection example parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548 GeodesicActiveContour segmentation example parameters . . . . . . . . . . . . . . . . . 553 ThresholdSegmentationLevelSet segmentation parameters . . . . . . . . . . . . . . . . . 558

11.1 ImageRandomConstIteratorWithIndex usage . . . . . . . . . . . . . . . . . . . . . . . . . 720

Part I

Introduction

CHAPTER

ONE

WelcomeWelcome to the Insight Segmentation and Registration Toolkit (ITK) Software Guide. This book has been updated for ITK 2.4 and later versions of the Insight Toolkit software. ITK is an open-source, object-oriented software system for image processing, segmentation, and registration. Although it is large and complex, ITK is designed to be easy to use once you learn about its basic object-oriented and implementation methodology. The purpose of this Software Guide is to help you learn just this, plus to familiarize you with the important algorithms and data representations found throughout the toolkit. The material is taught using an extensive set of examples that we encourage you to compile and run while you read this guide. ITK is a large system. As a result it is not possible to completely document all ITK objects and their methods in this text. Instead, this guide will introduce you to important system concepts and lead you up the learning curve as fast and efciently as possible. Once you master the basics, we suggest that you take advantage of the many resources available including the Doxygen documentation pages (http://www.itk.org/HTML/Documentation.htm ) and the community of ITK users (see Section 1.5 on page 10.) The Insight Toolkit is an open-source software system. What this means is that the community of ITK users and developers has great impact on the evolution of the software. Users and developers can make signicant contributions to ITK by providing bug reports, bug xes, tests, new classes, and other feedback. Please feel free to contribute your ideas to the community (the ITK user mailing list is the preferred method; a developers mailing list is also available).

1.1 OrganizationThis software guide is divided into three parts, each of which is further divided into several chapters. Part I is a general introduction to ITK, within the next chaptera description of how to install the Insight Toolkit on your computer. This includes installing pre-compiled libraries and executables, and compiling the software from the source code. Part I also introduces basic

4

Chapter 1. Welcome

system concepts such as an overview of the system architecture, and how to build applications in the C++, Tcl, and Python programming languages. Part II describes the system from the user point of view. Dozens of examples are used to illustrate important system features. Part III is for the ITK developer. Part III explains how to create your own classes, extend the system, and interface to various windowing and GUI systems.

1.2 How to Learn ITKThere are two broad categories of users of ITK. First are class developers, those who create classes in C++. The second, users, employ existing C++ classes to build applications. Class developers must be procient in C++, and if they are extending or modifying ITK, they must also be familiar with ITKs internal structures and design (material covered in Part III). Users may or may not use C++, since the compiled C++ class library has been wrapped with the Tcl and Python interpreted languages. However, as a user you must understand the external interface to ITK classes and the relationships between them. The key to learning how to use ITK is to become familiar with its palette of objects and the ways of combining them. If you are a new Insight Toolkit user, begin by installing the software. If you are a class developer, youll want to install the source code and then compile it. Users may only need the precompiled binaries and executables. We recommend that you learn the system by studying the examples and then, if you are a class developer, study the source code. Start by reading Chapter 3, which provides an overview of some of the key concepts in the system, and then review the examples in Part II. You may also wish to compile and run the dozens of examples distributed with the source code found in the directory Insight/Examples. (Please see the le Insight/Examples/README.txt for a description of the examples contained in the various subdirectories.) There are also several hundred tests found in the source distribution in Insight/Testing/Code, most of which are minimally documented testing code. However, they may be useful to see how classes are used together in ITK, especially since they are designed to exercise as much of the functionality of each class as possible.

1.3 Software OrganizationThe following sections describe the directory contents, summarize the software functionality in each directory, and locate the documentation and data.

1.3.1 Obtaining the SoftwareThere are three different ways to access the ITK source code (see Section 1.4 on page 5). 1. from periodic releases available on the ITK Web site,

1.4. Downloading ITK

5

2. from CD-ROM, and 3. from direct access to the CVS source code repository. Ofcial releases are available a few times a year and announced on the ITK Web pages and mailing lists. However, they may not provide the latest and greatest features of the toolkit. In general, the periodic releases and CD-ROM releases are the same, except that the CD release typically contains additional resources and data. CVS access provides immediate access to the latest toolkit additions, but on any given day the source code may not be stable as compared to the ofcial releasesi.e., the code may not compile, it may crash, or it might even produce incorrect results. This software guide assumes that you are working with the ofcial ITK version 2.4 release (available on the ITK Web site). If you are a new user, we highly recommend that you use the released version of the software. It is stable, consistent, and better tested than the code available from the CVS repository. Later, as you gain experience with ITK, you may wish to work from the CVS repository. However, if you do so, please be aware of the ITK quality testing dashboard. The Insight Toolkit is heavily tested using the open-source DART regression testing system (http://public.kitware.com/dashboard.php ). Before updating the CVS repository, make sure that the dashboard is green indicating stable code. If not green it is likely that your software update is unstable. (Learn more about the ITK quality dashboard in Section 14.2 on page 774.)

1.4 Downloading ITKITK can be downloaded without cost from the following web site: http://www.itk.org/HTML/Download.php In order to track the kind of applications for which ITK is being used, you will be asked to complete a form prior to downloading the software. The information you provide in this form will help developers to get a better idea of the interests and skills of the toolkit users. It also assists in future funding requests to sponsoring agencies. Once you ll out this form you will have access to the download page where two options for obtaining the software will be found. (This page can be book marked to facilitate subsequent visits to the download site without having to complete any form again.) You can get the tarball of a stable release or you can get the development version through CVS. The release version is stable and dependable but may lack the latest features of the toolkit. The CVS version will have the latest additions but is inherently unstable and may contain components with work in progress. The following sections describe the details of each one of these two alternatives.

6

Chapter 1. Welcome

1.4.1 Downloading Packaged ReleasesPlease read the GettingStarted.txt1 document rst. It will give you an overview of the download and installation processes. Then choose the tarball that better ts your system. The options are .zip and .tgz les. The rst type is better suited for MS-Windows while the second one is the preferred format for UNIX systems. Once you unzip or untar the le a directory called Insight will be created in your disk and you will be ready for starting the conguration process described in Section 2.1.1 on page 14.

1.4.2 Downloading from CVSThe Concurrent Versions System (CVS) is a tool for software version control [27]. Generally only developers should be using CVS, so here we assume that you know what CVS is and how to use it. For more information about CVS please see Section 14.1 on page 773. (Note: please make sure that you access the software via CVS only when the ITK Quality Dashboard indicates that the code is stable. Learn more about the Quality Dashboard at 14.2 on page 774.) Access ITK via CVS using the following commands (under UNIX and Cygwin): cvs -d :pserver:anonymous@www.itk.org:/cvsroot/Insight login (respond with password "insight") cvs -d :pserver:anonymous@www.itk.org:/cvsroot/Insight co Insight This will trigger the download of the software into a directory named Insight. Any time you want to update your version, it will be enough to change into this directory Insight and type: cvs update -d -P Once you obtain the software you are ready to congure and compile it (see Section 2.1.1 on page 14). First, however, we recommend that you join the mailing list and read the following sections describing the organization of the software.

1.4.3 Join the Mailing ListIt is strongly recommended that you join the users mailing list. This is one of the primary resources for guidance and help regarding the use of the toolkit. You can subscribe to the users list online at http://www.itk.org/HTML/MailingLists.htm1 http://www.itk.org/HTML/GettingStarted.txt

1.4. Downloading ITK

7

The insight-users mailing list is also the best mechanism for expressing your opinions about the toolkit and to let developers know about features that you nd useful, desirable or even unnecessary. ITK developers are committed to creating a self-sustaining open-source ITK community. Feedback from users is fundamental to achieving this goal.

1.4.4 Directory StructureTo begin your ITK odyssey, you will rst need to know something about ITKs software organization and directory structure. Even if you are installing pre-compiled binaries, it is helpful to know enough to navigate through the code base to nd examples, code, and documentation. ITK is organized into several different modules, or CVS checkouts. If you are using an ofcial release or CD release, you will see three important modules: the Insight, InsightDocuments and InsightApplications modules. The source code, examples and applications are found in the Insight module; documentation, tutorials, and material related to the design and marketing of ITK are found in InsightDocuments; and fairly complex applications using ITK (and other systems such as VTK, Qt, and FLTK) are available from InsightApplications. Usually you will work with the Insight module unless you are a developer, are teaching a course, or are looking at the details of various design documents. The InsightApplications module should only be downloaded and compiled once the Insight module is functioning properly. The Insight module contains the following subdirectories: Insight/Auxiliarycode that interfaces packages to ITK. Insight/Codethe heart of the software; the location of the majority of the source code. Insight/Documentationa compact subset of documentation to get users started with ITK. Insight/Examplesa suite of simple, well-documented examples used by this guide and to illustrate important ITK concepts. Insight/Testinga large number of small programs used to test ITK. These examples tend to be minimally documented but may be useful to demonstrate various system concepts. These tests are used by DART to produce the ITK Quality Dashboard (see Section 14.2 on page 774.) Insight/Utilitiessupporting software for the ITK source code. For example, DART and Doxygen support, as well as libraries such as png and zlib. Insight/Validationa series of validation case studies including the source code used to produce the results. Insight/Wrappingsupport for the CABLE wrapping tool. CABLE is used by ITK to build interfaces between the C++ library and various interpreted languages (currently Tcl and Python are supported).

8

Chapter 1. Welcome

The source code directory structurefound in Insight/Codeis important to understand since other directory structures (such as the Testing and Wrapping directories) shadow the structure of the Insight/Code directory. Insight/Code/Commoncore classes, macro denitions, typedefs, and other software constructs central to ITK. Insight/Code/Numericsmathematical library and supporting classes. (Note: ITKs mathematical library is based on the VXL/VNL software package http://vxl.sourceforge.net .) Insight/Code/BasicFiltersbasic image processing lters. Insight/Code/IOclasses that support the reading and writing of data. Insight/Code/Algorithmsthe location of most segmentation and registration algorithms. Insight/Code/SpatialObjectclasses that represent and organize data using spatial relationships (e.g., the leg bone is connected to the hip bone, etc.) Insight/Code/Patentedany patented algorithms are placed here. Using this code in commercial application requires a patent license. Insight/Code/Localan empty directory used by developers and users to experiment with new code. The InsightDocuments module contains the following subdirectories: InsightDocuments/CourseWarematerial related to teaching ITK. InsightDocuments/Developerhistorical documents covering the design and creation of ITK including progress reports and design documents.A TEX styles to produce this work as well as other docu InsightDocuments/LatexL ments.

InsightDocuments/Marketingmarketing yers and literature used to succinctly describe ITK. InsightDocuments/Paperspapers related to the many algorithms, data representations, and software tools used in ITK.A InsightDocuments/SoftwareGuideL TEX les used to create this guide. (Note that A the code found in Insight/Examples is used in conjunction with these L TEX les.)

InsightDocuments/Validationvalidation case studies using ITK.

1.4. Downloading ITK

9

InsightDocuments/Webthe source HTML and other material used to produce the Web pages found at http://www.itk.org . Similar to the Insight module, access to the InsightDocuments module is also available via CVS using the following commands (under UNIX and Cygwin): cvs -d :pserver:anonymous@www.itk.org:/cvsroot/Insight co InsightDocuments The InsightApplications module contains large, relatively complex examples of ITK usage. See the web pages at http://www.itk.org/HTML/Applications.htm for a description. Some of these applications require GUI toolkits such as Qt and FLTK or other packages such as VTK (The Visualization Toolkit http://www.vtk.org ). Do not attempt to compile and build this module until you have successfully built the core Insight module. Similar to the Insight and InsightDocuments module, access to the InsightApplications module is also available via CVS using the following commands (under UNIX and Cygwin): cvs -d:pserver:anonymous@www.itk.org:/cvsroot/Insight \ co InsightApplications

1.4.5 DocumentationBesides this text, there are other documentation resources that you should be aware of. Doxygen Documentation. The Doxygen documentation is an essential resource when working with ITK. These extensive Web pages describe in detail every class and method in the system. The documentation also contains inheritance and collaboration diagrams, listing of event invocations, and data members. The documentation is heavily hyper-linked to other classes and to the source code. The Doxygen documentation is available on the companion CD, or on-line at http://www.itk.org . Make sure that you have the right documentation for your version of the source code. Header Files. Each ITK class is implemented with a .h and .cxx/.txx le (.txx le for templated classes). All methods found in the .h header les are documented and provide a quick way to nd documentation for a particular method. (Indeed, Doxygen uses the header documentation to produces its output.)

1.4.6 DataThe Insight Toolkit was designed to support the Visible Human Project and its associated data. This data is available from the National Library of Medicine at http://www.nlm.nih.gov/research/visible/visible_human.html . Another source of data can be obtained from the ITK Web site at either of the following:

10

Chapter 1. Welcome

http://www.itk.org/HTML/Data.htm ftp://public.kitware.com/pub/itk/Data/ .

1.5 The Insight Community and SupportITK was created from its inception as a collaborative, community effort. Research, teaching, and commercial uses of the toolkit are expected. If you would like to participate in the community, there are a number of possibilities. Users may actively report bugs, defects in the system API, and/or submit feature requests. Currently the best way to do this is through the ITK users mailing list. Developers may contribute classes or improve existing classes. If you are a developer, you may request permission to join the ITK developers mailing list. Please do so by sending email to will.schroeder at kitware.com. To become a developer you need to demonstrate both a level of competence as well as trustworthiness. You may wish to begin by submitting xes to the ITK users mailing list. Research partnerships with members of the Insight Software Consortium are encouraged. Both NIH and NLM will likely provide limited funding over the next few years, and will encourage the use of ITK in proposed work. For those developing commercial applications with ITK, support and consulting are available from Kitware at http://www.kitware.com . Kitware also offers short ITK courses either at a site of your choice or periodically at Kitware. Educators may wish to use ITK in courses. Materials are being developed for this purpose, e.g., a one-day, conference course and semester-long graduate courses. Watch the ITK web pages or check in the InsightDocuments/CourseWare directory for more information.

1.6 A Brief History of ITKIn 1999 the US National Library of Medicine of the National Institutes of Health awarded six three-year contracts to develop an open-source registration and segmentation toolkit, that eventually came to be known as the Insight Toolkit (ITK) and formed the basis of the Insight Software Consortium. ITKs NIH/NLM Project Manager was Dr. Terry Yoo, who coordinated the six prime contractors composing the Insight consortium. These consortium members included three commercial partnersGE Corporate R&D, Kitware, Inc., and MathSoft (the company name is now Insightful)and three academic partnersUniversity of North Carolina (UNC), University of Tennessee (UT) (Ross Whitaker subsequently moved to University of Utah), and University of Pennsylvania (UPenn). The Principle Investigators for these partners

1.6. A Brief History of ITK

11

were, respectively, Bill Lorensen at GE CRD, Will Schroeder at Kitware, Vikram Chalana at Insightful, Stephen Aylward with Luis Ibanez at UNC (Luis is now at Kitware), Ross Whitaker with Josh Cates at UT (both now at Utah), and Dimitri Metaxas at UPenn (now at Rutgers). In addition, several subcontractors rounded out the consortium including Peter Raitu at Brigham & Womens Hospital, Celina Imielinska and Pat Molholt at Columbia University, Jim Gee at UPenns Grasp Lab, and George Stetten at the University of Pittsburgh. In 2002 the rst ofcial public release of ITK was made available. In addition, the National Library of Medicine awarded thirteen contracts to several organizations to extend ITKs capabilities. NLM funding of Insight Toolkit development is continuing through 2003, with additional application and maintenance support anticipated beyond 2003. If you are interested in potential funding opportunities, we suggest that you contact Dr. Terry Yoo at the National Library of Medicine for more information.

CHAPTER

TWO

InstallationThis section describes the process for installing ITK on your system. Keep in mind that ITK is a toolkit, and as such, once it is installed in your computer there will be no application to run. Rather, you will use ITK to build your own applications. What ITK does providebesides the toolkit properis a large set of test les and examples that will introduce you to ITK concepts and will show you how to use ITK in your own projects. Some of the examples distributed with ITK require third party libraries that you may have to download. For an initial installation of ITK you may want to ignore these extra libraries and just build the toolkit itself. In the past, a large fraction of the trafc on the insight-users mailing list has originated from difculties in getting third party libraries compiled and installed rather than with actual problems building ITK. ITK has been developed and tested across different combinations of operating systems, compilers, and hardware platforms including MS-Windows, Linux on Intel-compatible hardware, Solaris, IRIX, Mac OSX, and Cygwin. It is known to work with the following compilers: Visual Studio 6, .NET 2002, .NET 2003 GCC 2.95.x, 2.96, 3.x SGI MIPSpro 7.3x Borland 5.5 Given the advanced usage of C++ features in the toolkit, some compilers may have difculties processing the code. If you are currently using an outdated compiler this may be an excellent excuse for upgrading this old piece of software!

2.1 Conguring ITKThe challenge of supporting ITK across platforms has been solved through the use of CMake, a cross-platform, open-source build system. CMake is used to control the software compilation

14

Chapter 2. Installation

process using simple platform and compiler independent conguration les. CMake generates native makeles and workspaces that can be used in the compiler environment of your choice. CMake is quite sophisticatedit supports complex environments requiring system conguration, compiler feature testing, and code generation. CMake generates Makeles under UNIX and Cygwin systems and generates Visual Studio workspaces under Windows (and appropriate build les for other compilers like Borland). The information used by CMake is provided by CMakeLists.txt les that are present in every directory of the ITK source tree. These les contain information that the user provides to CMake at conguration time. Typical information includes paths to utilities in the system and the selection of software options specied by the user.

2.1.1 Preparing CMakeCMake can be downloaded at no cost from http://www.cmake.org ITK requires at least CMake version 2.0. You can download binary versions for most of the popular platforms including Windows, Solaris, IRIX, HP, Mac and Linux. Alternatively you can download the source code and build CMake on your system. Follow the instructions in the CMake Web page for downloading and installing the software. Running CMake initially requires that you provide two pieces of information: where the source code directory is located (ITK SOURCE DIR), and where the object code is to be produced (ITK BINARY DIR). These are referred to as the source directory and the binary directory. We recommend setting the binary directory to be different than the source directory (an out-ofsource build), but ITK will still build if they are set to the same directory (an in-source build). On Unix, the binary directory is created by the user and CMake is invoked with the path to the source directory. For example:mkdir Insight-binary cd Insight-binary ccmake ../Insight

On Windows, the CMake GUI is used to specify the source and build directories (Figure 2.1). CMake runs in an interactive mode in that you iteratively select options and congure according to these options. The iteration proceeds until no more options remain to be selected. At this point, a generation step produces the appropriate build les for your conguration. This interactive conguration process can be better understood if you imagine that you are walking through a decision tree. Every option that you select introduces the possibility that new, dependent options may become relevant. These new options are presented by CMake at the top of the options list in its interface. Only when no new options appear after a conguration

2.1. Conguring ITK

15

iteration can you be sure that the necessary decisions have all been made. At this point build les are generated for the current conguration.

2.1.2 Conguring ITK

Figure 2.1: CMake interface. Top) ccmake, the UNIX version based on curses. Bottom) CMakeSetup, the MS-Windows version based on MFC. Figure 2.1 shows the CMake interface for UNIX and MS-Windows. In order to speed up the build process you may want to disable the compilation of the testing and examples. This is done with the variables BUILD TESTING=OFF and BUILD EXAMPLES=OFF. The examples distributed

16

Chapter 2. Installation

with the toolkit are a helpful resource for learning how to use ITK components but are not essential for the use of the toolkit itself. The testing section includes a large number of small programs that exercise the capabilities of ITK classes. Due to the large number of tests, enabling the testing option will considerably increase the build time. It is not desirable t