Optimized scanning procedures for four-dimensional CT data acquisition in radiation therapy

The goal of conformal radiation techniques is to improve local tumor control through dose escalation to target volumes while at the same time sparing surrounding healthy tissue. Accurate target volume delineation is essential in achieving this goal to avoid inadequate tumor coverage and/or irradiation of an unnecessary volume of healthy tissue. Respiratory motion is known to be the largest intra-fractional organ motion and the most significant source of uncertainty in treatment planning for chest lesions. A method to minimize effects of respiratory motion is to use four-dimensional (4D) radiotherapy.;A novel scanning procedure for 4D CT data acquisition is described in this work. Three single-slice helical scans are acquired simultaneously with the real-time tracking of several markers placed on a moving phantom. At the end of the three scans. CT data is binned into different respiratory phases according to the externally recorded respiratory signal and the scanned volume is reconstructed for several respiratory phases. The 4D CT images obtained show an overall improvement when compared to conventional CT images of a moving phantom.