Evaluating commercial image registration packages for radiotherapy treatment planning

Multi-modality imaging is involved in almost all oncology applications from diagnosis through treatment planning and follow-up. Commercial image fusion software packages are becoming available but require comprehensive evaluation to ensure reliability of fusion and the underpinning registration algorithm. This is especially critical for target volume delineation in radiotherapy. The present work seeks to assess such accuracy for a number of available registration methods. A National Electrical Manufacturers Association (NEMA) body phantom was used in evaluating computer tomography (CT), magnetic resonance (MR) and PET images. In addition, discussion is provided concerning the choice and geometry of fiducial markers in phantom studies and the effect of window level on target size, in particular in regard to the application of multimodality imaging in treatment planning. In general, the accuracy of fusion of multi-modality images was within 0.5–1.5 mm of actual feature diameters and <2 ml volume of actual values, particularly in CT images.