Image-guided lung radiotherapy: Bringing technology into routine clinical practice

18093 Background: Cone-beam CT (CBCT), an imaging system integrated into the RT treatment unit, produces 3D images far superior to the conventional 2D portal images used for verification of patient (pt) set-up. This allows direct matching to the RT treatment planning CT images, potentially increasing the precision of RT delivery. We report on the broad implementation of this new RT image-guided paradigm in lung cancer patients at our center. Methods: All lung cancer pts undergoing radical RT were planned using 4DCT and imaged daily for repositioning with CBCT since 04/06. Initially, CBCT datasets were compared with the planning CT to assess the setup error (bone surrogate), using two immobilisation methods: evacuated bags (EB) and chest-board (ChB). Discrepancies >3 mm between the two datasets, in any direction, were corrected before the start of each RT fraction. Data were retrospectively analyzed to assess the initial and residual discrepancies (43 pts; 1,128 CBCTs).Alternative matching strategies were ...