title: Four dimensional digital tomosynthesis using on-board imager for the verification of respiratory motion.
abstract: OBJECTIVE
  To evaluate respiratory motion of a patient by generating four-dimensional digital tomosynthesis (4D DTS), extracting respiratory signal from patients' on-board projection data, and ensuring the feasibility of 4D DTS as a localization tool for the targets which have respiratory movement.
  
  
  METHODS
  Four patients with lung and liver cancer were included to verify the feasibility of 4D-DTS with an on-board imager. CBCT acquisition (650-670 projections) was used to reconstruct 4D DTS images and the breath signal of the patients was generated by extracting the motion of diaphragm during data acquisition. Based on the extracted signal, the projection data was divided into four phases: peak-exhale phase, mid-inhale phase, peak-inhale phase, and mid-exhale phase. The binned projection data was then used to generate 4D DTS, where the total scan angle was assigned as ±22.5° from rotation center, centered on 0° and 180° for coronal "half-fan" 4D DTS, and 90° and 270° for sagittal "half-fan" 4D DTS. The result was then compared with 4D CBCT which we have also generated with the same phase distribution.
  
  
  RESULTS
  The motion of the diaphragm was evident from the 4D DTS results for peak-exhale, mid-inhale, peak-inhale and mid-exhale phase assignment which was absent in 3D DTS. Compared to the result of 4D CBCT, the view aliasing effect due to arbitrary angle reconstruction was less severe. In addition, the severity of metal artifacts, the image distortion due to presence of metal, was less than that of the 4D CBCT results.
  
  
  CONCLUSIONS
  We have implemented on-board 4D DTS on patients data to visualize the movement of anatomy due to respiratory motion. The results indicate that 4D-DTS could be a promising alternative to 4D CBCT for acquiring the respiratory motion of internal organs just prior to radiotherapy treatment.
authors.affiliation: Department of Radiation Oncology, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Justin C
authors.initials: JC
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Jin Sung
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, Ulsan University Hospital, Ulsan, Korea.
authors.forename: Sung Ho
authors.initials: SH
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, United States of America.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Webster
authors.affiliation: Department of Radiation Oncology, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Soyoung
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Radiation Oncology & Medical Biophysics, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Canada.
authors.forename: William Y
authors.initials: WY
authors.lastname: Song
authors.affiliation: Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Youngyih
authors.initials: Y
authors.lastname: Han
mesh_terms: D054893:Cone-Beam Computed Tomography; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000503:physiopathology; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000503:physiopathology; D009068:Movement; D019047:Phantoms, Imaging; D012119:Respiration