title: Abdominal organ motion measured using 4D CT.
abstract: OBJECTIVE
  To measure respiration-induced abdominal organ motion using four-dimensional computed tomography (4D CT) scanning and to examine the organ paths.
  
  
  METHODS
  During 4D CT scanning, consecutive CT images are acquired of the patient at each couch position. Simultaneously, the patient's respiratory pattern is recorded using an external marker block taped to the patient's abdomen. This pattern is used to retrospectively organize the CT images into multiple three-dimensional images, each representing one breathing phase. These images are analyzed to measure organ motion between each phase. The displacement from end expiration is compared to a displacement limit that represents acceptable dosimetric results (5 mm).
  
  
  RESULTS
  The organs measured in 13 patients were the liver, spleen, and left and right kidneys. Their average superior to inferior absolute displacements were 1.3 cm for the liver, 1.3 cm for the spleen, 1.1 cm for the left kidney, and 1.3 cm for the right kidney. Although the organ paths varied among patients, 5 mm of superior to inferior displacement from end expiration resulted in less than 5 mm of displacement in the other directions for 41 of 43 organs measured.
  
  
  CONCLUSIONS
  Four-dimensional CT scanning can accurately measure abdominal organ motion throughout respiration. This information may result in greater organ sparing and planning target volume coverage.
authors.affiliation: Department of Radiation Oncology, University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA 19107, USA.
authors.forename: Edward D
authors.initials: ED
authors.lastname: Brandner
authors.forename: Andrew
authors.initials: A
authors.lastname: Wu
authors.forename: Hungcheng
authors.initials: H
authors.lastname: Chen
authors.forename: Dwight
authors.initials: D
authors.lastname: Heron
authors.forename: Shalom
authors.initials: S
authors.lastname: Kalnicki
authors.forename: Krishna
authors.initials: K
authors.lastname: Komanduri
authors.forename: Kristina
authors.initials: K
authors.lastname: Gerszten
authors.forename: Steve
authors.initials: S
authors.lastname: Burton
authors.forename: Irfan
authors.initials: I
authors.lastname: Ahmed
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Shou
mesh_terms: D000005:Abdomen; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007668:Kidney / Q000000981:diagnostic imaging; D008099:Liver / Q000000981:diagnostic imaging; D008297:Male; D009068:Movement; D011860:Radiography, Abdominal / Q000379:methods; D012119:Respiration; D013154:Spleen / Q000000981:diagnostic imaging; D013679:Technology, Radiologic / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods*