Three-dimensional localisation based on projectional and tomographic imagecorrelation: an application for digital tomosynthesis

Accurate three-dimensional tumor localisation in Radiotherapy, is critical to the treatment outcome, particularly when high dose gradients are present . A number of techniques have been proposed for the localisation of anatomi cal structures or markers. The present study proposes an approach to a conc urrent maximisation of localisation accuracy and efficiency by correlation of tomographic and projectional images. The method introduces an element of direct verification and interactive optimisation of the process. Tomograph ic images are used for the identification of a point of interest. Its posit ion is computed within the treatment co-ordinate system and verification of this position is achieved by obtaining the beam's eye view of the identifi ed point on two projection radiographs. The key element of the approach is that all images used should be part of one single image data set. The imple mentation of this localisation method, as part of the functionality of a Di gital Tomosynthesis prototype, has provided an integrated facility for loca lisation, of optimised accuracy and precision, while easy and efficient to use. The considerations are general and apply in principle to any imaging s ystem that can augment tomographic images with projections. (C) 1999 IPEM. Published by Elsevier Science Ltd. All rights reserved.