Adaptive portal CT reconstruction: A simulation study

In radiotherapy, radiation treatment beams contain valuable information for patient setup verification. These beams may be used for portal CT reconstr uction. However, direct use of the beam data for reconstruction may yield i nadequate CT images simply because these beams cover only a part of the pat ient body. In this study, we use the treatment beams in addition to a set o f regular CT projection beams to reconstruct a locally enhanced portal CT i mage. This approach is called adaptive portal CT reconstruction. A computer simulation demonstrated the advantages of the approach. The image reconstr uction was carried out by the multilevel scheme algebraic reconstruction te chnique. Results indicated that the image quality of adaptive portal CT rec onstruction is equivalent to that obtained from a full set of projections. This proposed technique should be not only valuable for three-dimensional r adiotherapy verification, but also applicable to diagnostic CT imaging. (C) 2000 American Association of Physicists in Medicine. [S0094-2405(00)02110- 6].