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User's guide

What is RTK?

RTK is an open source C++ library, not an executable. This means that you must write code that uses RTK and compile it before you will obtain something that you can run and get a result from. It also means that you can adapt or extend RTK to address your problem at hand. To facilitate this over multiple operating systems, compilers, and system configurations, RTK itself must be built from its source code. RTK is based on The Insight Toolkit, therefore you would need to get, configure and compile The Insight Toolkit first.

The three steps to starting to work with RTK are therefore:

  1. Download and Build the ITK source
  2. Download/Obtain/Get the RTK source
  3. Build the RTK library
  4. Write your own code that uses RTK and build it, linking to the RTK library.

In the next sections we describe each of these steps.


In order to compile RTK you will need the following:

  • GIT (in order to get the software)
  • CMake (in order to configure RTK)
  • C/C++ compiler

Step 0 - Getting ITK

RTK currently uses ITK 3.20.

We recommend to look into the ITK wiki in order to compile ITK for your system. The documentation for ITK should be fairly straight forward. Moreover, the concepts for building ITK are very similar to those for RTK. In order to get ITK 3.20 from git:

 git clone git://itk.org/ITK.git
 cd ITK
 git checkout release-3.20

One important CMake option to make sure is enabled is the ITK_USE_REVIEW which should be set to ON when running CMake on ITK.


Not that you don't need to build the examples, the documentation or any of the tests to use ITK with RTK.

Step 1 - Getting RTK

This page documents how to download RTK through Git. Follow the ITK Git download instructions to install Git.

To get the latest source code for RTK:

 git clone git://github.com/SimonRit/RTK.git

Step 2 - Building RTK

Like ITK, in order to build RTK you would need to install [CMake www.cmake.org]. CMake supports out of source build so we recommend to create a binary directory 'RTK-bin'

 mkdir RTK-bin
 cd RTK-bin
 cmake ../RTK

When CMake asks for the ITK_DIR, specify the binary directory where ITK is built.

 ITK_DIR /path to directory/ITK-bin

Step 3 - Running the HelloWorld application

In order to verify the installation of your RTK library, you can run the HelloWorld application. This application is part of the RTK examples and should be built by default. Otherwise make sure that


when configuring RTK with CMake.


Tutorial 0 - Building an HelloWorld application with RTK

RTK is a library, therefore it's meant to be integrated into application. This tutorial shows how to create a simple HelloWorld project that links with RTK. The source code for this tutorial is located in RTK/examples/HelloWorld.

  • First you need to create a CMakeLists.txt with the following lines:
 # This project is designed to be built outside the RTK source tree.
 # Find the RTK libraries and includes
 # Executable
 ADD_EXECUTABLE(HelloWorld HelloWorld.cxx )
  • Create a HelloWorld.cxx file
 #include <rtkFDKBackProjectionImageFilter.h>
 int main(int argc, char **argv)
 // Define the type of pixel and the image dimension
 typedef float OutputPixelType;
 const unsigned int Dimension = 3;
 // Define the type of image
 typedef itk::Image< OutputPixelType, Dimension > OutputImageType;
 // Define and allocate the FDK Back Projection Filter
 typedef rtk::FDKBackProjectionImageFilter<OutputImageType, OutputImageType> BPType;
 BPType::Pointer p = BPType::New();
 std::cout << "RTK Hello World!" << std::endl;
 return 0;
  • Run CMake on the HelloWorld directory and create a HelloWorld-bin
  • Configure and build the project using your favorite compiler
  • Run the HelloWorld application. If everything runs correctly you should see "RTK Hello World!" written on the console.

Tutorial 1 - My first reconstruction

Reconstruct a Sphere


RTK also provide a set of command line applications that are compiled if the cmake option BUILD_APPLICATIONS is turned on. Each application uses [gengetopt] to allow parsing of the command line options. The manual of each application can be obtained with the --help or -h option. They can be executed sequentially in bash scripts.

Script 1 - FDK

FDK Shepp Logan

Script 2 - Forward Projection

POPI projections and reconstruction


A clear understanding of the geometry is essential for the use of a tomography package. The geometry description has been written in a latex document compiled here.