title: Organ motion in pediatric high-risk neuroblastoma patients using four-dimensional computed tomography.
abstract: OBJECTIVE
  High-risk neuroblastoma (HR-NBL) requires multimodality treatment, including external beam radiation of the primary tumor site following resection. Radiotherapy planning must take into account motion of the target and adjacent normal anatomy, both of which are poorly understood in the pediatric population, and which may differ significantly from those in adults.
  
  
  METHODS
  We examined 4DCT scans of 15 consecutive pediatric patients treated for HR-NBL, most with tumors in the abdominal cavity. The diaphragm and organs at risk were contoured at full inhale, full exhale, and on free-breathing scans. Maximum displacement of organs between full inhale and full exhale was measured in the anterior, posterior, superior, inferior, left, and right directions, as was displacement of centroids in the A/P, S/I, and L/R axes. Contours on free-breathing scans were compared to those on 4D scans.
  
  
  RESULTS
  Maximum displacement was along the S/I axis, with the superior aspects of organs moving more than the inferior, implying organ compression with respiration. Liver and spleen exhibited the largest motion, which correlated strongly with the S/I motion of the diaphragm. The maximum organ motion observed in the abdomen and thorax were 4.5 mm and 7.4 mm, respectively, while maximum diaphragm displacement was 5.7 mm. Overall findings mirrored observations in adults, but with smaller magnitudes, as expected. No consistent margins could be added to the free-breathing scans to encompass the motion determined using 4DCT.
  
  
  CONCLUSIONS
  Organ motion within the pediatric abdomen and pelvis is similar to that observed in adults, but with smaller magnitude. Precise margins to accommodate motion are patient-specific, underscoring the need for 4DCT scanning when possible.
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, 19104, USA.
authors.forename: Sneha
authors.initials: S
authors.lastname: Kannan
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, 19104, USA.
authors.forename: Boon-Keng Kevin
authors.initials: BK
authors.lastname: Teo
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, 19104, USA.
authors.forename: Timothy
authors.initials: T
authors.lastname: Solberg
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, 19104, USA.
authors.forename: Christine
authors.initials: C
authors.lastname: Hill-Kayser
mesh_terms: D002648:Child; D002675:Child, Preschool; D005260:Female; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007223:Infant; D008297:Male; D009038:Motion; D009447:Neuroblastoma / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D058958:Organs at Risk / Q000000981:diagnostic imaging* / Q000528:radiation effects; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D012119:Respiration; D012307:Risk Factors
keywords: 4DCT; neuroblastoma; organ motion; pediatric