Onboard cone beam CT with flexible image trajectories to improve image quality and longitudinal coverage - Simulation and phantom study

Deshan Yang, Jun Tan, Hua Li, Sreekrishna M. Goddu, Harold Li

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


Onboard CBCT for radiation linear accelerators suffers from limited longitudinal coverage and various image quality problems, especially at wider cone angles. Such problems prevent CBCT being applied in full potentials for many clinical cancer sites, including head-neck, and for many quantitative applications, including tumor response evaluation and daily radiation dose computation. We propose to use CBCT with flexible X-ray source trajectories to overcome these limitations. The core idea is to combine gantry rotation with simultaneous couch motion. Longitudinal coverage can therefore be extended without limitation. Image quality can be enhanced by applying advanced exact CBCT reconstruction algorithm. However, unlike diagnostic CT where helical CBCT is widely used, LINAC onboard CBCT because gantry can only rotate within 360 degrees and couch table cannot move during gantry rotation. To solve the hardware problem, we program the new Varian TrueBeam LINAC machine in developer mode to realize simultaneous gantry and couch motion so to simulate any flexible scan trajectories. We also implemented CBCT simulation algorithms with digital phantoms to support any flexible source trajectories. We implemented and improved Katsevich exact reconstruction algorithm for image reconstruction from projection data obtained in phantom simulations. We have studied a few different source trajectory models including double circle, helical and saddle. The initial digital phantom results were encouraging. The longitudinal coverage was extended. Image quality has been improved using Katsevich reconstruction algorithm. Physics phantom studies on TrueBeam LINAC machine is our next step.

Original languageEnglish (US)
Title of host publicationMedical Imaging 2012
Subtitle of host publicationPhysics of Medical Imaging
Publication statusPublished - May 4 2012
EventMedical Imaging 2012: Physics of Medical Imaging - San Diego, CA, United States
Duration: Feb 5 2012Feb 8 2012


OtherMedical Imaging 2012: Physics of Medical Imaging
CountryUnited States
CitySan Diego, CA



  • Cone-beam CT (CBCT)
  • helical CBCT
  • Katsevich
  • reconstruction
  • Varian TrueBeam

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Biomaterials
  • Radiology Nuclear Medicine and imaging

Cite this

Yang, D., Tan, J., Li, H., Goddu, S. M., & Li, H. (2012). Onboard cone beam CT with flexible image trajectories to improve image quality and longitudinal coverage - Simulation and phantom study. In Medical Imaging 2012: Physics of Medical Imaging (Vol. 8313). [83132Q] https://doi.org/10.1117/12.910851