MRIcroGL is an open source GPU-accelerated volume renderer for Linux, Windows and OSX. It uses Delphi or Lazarus/FPC as well as GLScene and PascalScript. Volume rendering is a useful tool for visualizing medical images.
http://www.mricro.com/mricrogl/
In addition, I would like to draw attention to a $300 US bounty I have posted for anyone who can add hardware accelerated shading, similar to the Cg code listed in Klais Engle's book
http://wiki.lazarus.freepascal.org/Bounties#Multi-platform_bounties
MRIcroGL est une projet d'accélération du rendu pour LINUX, WINDOWS et OSX. Il utilise DELPHI ou LAZARUS et permet de visualiser des images médicales.