Most of the research carried out by the FMRIB Analysis Group has been made available to the wider community as a single integrated software package, FSL (FMRIB's Software Library). FSL is available as both source code and as self-contained binary distributions for Linux, MacOS X (Apple), Windows XP (under Cygwin), Solaris (Sun) and IRIX (Silicon Graphics). It is freely available for academic (non-commercial) use. Almost all tools can be run both from the command line and via GUI. The FSL binary distributions come with all necessary third-party software bundled, making installation and setup extremely easy. FSL is in active use in over 1000 laboratories worldwide.
Most FSL tools come with web-based documentation, and the most complex tools (such as FEAT) include comprehensive ``bubble-popup-help'' in the GUI. Example data is supplied in a separate download named FEEDS (FSL Evaluation and Example Data Suite), which as well as providing example data for trying out the various FSL tools, includes a script which runs the core tools automatically and tests the results against supplied results, in order to check that FSL is running correctly. Further support on using FSL is offered via the FSL email list, at www.jiscmail.ac.uk/lists/fsl.html .
As well as the research-derived tools described in this review paper, FSL also includes a series of command-line image utilities, including a program for extracting a range of image statistics from 3D/4D images, and a ``calculator'' utility with a wide range of mathematical operations for 3D/4D image manipulation. FSL also includes an intuitive yet powerful 3D/4D image display tool, FSLView, which allows multiple colour overlays, multiple orthogonal or lightbox views, time series display (graph-based and movie-based), image editing and histogram viewing.