Planning target volume assessment in lung tumors during 3D conformal radiotherapy by means of an aSi electronic portal imaging device in cine mode

Purpose: The major uncertainties in treating lung cancer are the repositioning errors and respiratory lung tumor motion. Typically, margins are added to the clinical target volume (CTV) to obtain a planning target volume (PTV) allowing the accommodation of such uncertainties. We want to test a new technique to assess the adequacy of the chosen PTV using an aSi electronic portal imaging device (EPID). Methods: Four patients affected by lung cancer and treated by radical 3D conformal radiotherapy (3DRT) were studied. During treatment the EPID was used in cine mode acquisition: acquired images were used to the aim. Results and conclusions: Treatment monitoring with an EPID in cine mode is shown to be a clinically feasible and useful tool.