title: Cardiac and respiration induced motion of mediastinal lymph node targets in lung cancer patients throughout the radiotherapy treatment course.
abstract: Involved mediastinal lymph nodes (LNs) are often included in the radiotherapy target for lung cancer patients. Their motion may differ from the primary tumor motion, possibly undermining the loco-regional control. This study determines the detailed differential target motion throughout the treatment course.
  
  
  
  Ten lung cancer patients with 2-4 fiducial markers implanted in LN targets received IMRT with a daily pre-treatment cone-beam CT (CBCT) scan. Offline, the 3D trajectory of the markers was determined from their projected trajectory in the CBCT projections. Frequency analysis was performed to separate the intrafraction motion into a respiratory and cardiac component. The mean setup error of the markers and the motion range were used to calculate margins required for LN targets when setup is based on soft-tissue match.
  
  
  
  Respiration motion was largest in the CC direction and more prominent for more caudal LNs. Cardiac motion was often (73%) largest in the AP direction and tended to be largest for more cranial LNs. Margins for intrafraction motion and daily baseline shifts of LNs were 4.8mm (LR), 6.0mm (CC) and 6.7mm (AP).
  
  
  
  Detailed mapping showed that LN motion was in general governed by breathing, but some LNs had substantial cardiac induced motion.
authors: Department of Oncology, Aarhus University Hospital, Denmark; Institute of Clinical Medicine, Aarhus University, Denmark. Electronic address: maiscmis@rm.dk.
authors: Mai Lykkegaard
authors: ML
authors: Schmidt
authors: Department of Medical Physics, Aarhus University Hospital, Denmark.
authors: Lone
authors: L
authors: Hoffmann
authors: Department of Oncology, Aarhus University Hospital, Denmark.
authors: Marianne Marquard
authors: MM
authors: Knap
authors: Department of Pulmonology, Aarhus University Hospital, Denmark.
authors: Torben Riis
authors: TR
authors: Rasmussen
authors: Department of Pulmonology, Aarhus University Hospital, Denmark.
authors: Birgitte Holst
authors: BH
authors: Folkersen
authors: Department of Oncology, Aarhus University Hospital, Denmark.
authors: Jakob
authors: J
authors: Toftegaard
authors: Department of Medical Physics, Aarhus University Hospital, Denmark.
authors: Ditte Sloth
authors: DS
authors: Møller
authors: Department of Oncology, Aarhus University Hospital, Denmark; Institute of Clinical Medicine, Aarhus University, Denmark.
authors: Per Rugård
authors: PR
authors: Poulsen
mesh_terms: D000368:Aged; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D005260:Female; D057918:Fiducial Markers; D006321:Heart / Q000502:physiology*; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D008198:Lymph Nodes / Q000000981:diagnostic imaging* / Q000528:radiation effects; D008297:Male; D008482:Mediastinum; D008875:Middle Aged; D009038:Motion; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D012119:Respiration
keywords: Differential motion; Interfraction motion; Intrafraction motion; Lung; Lymph node