title: The advantage of deep-inspiration breath-hold and cone-beam CT based soft-tissue registration for locally advanced lung cancer radiotherapy.
abstract: Three cone-beam computed tomography (CBCT) registration strategies combined with deep-inspiration breath-hold (DIBH) and free-breathing (FB) were explored, in terms of obtaining the smallest planning target volume (PTV).
  
  
  
  CBCT images were acquired pre- and post-treatment in FB and DIBH, for 17 locally advanced lung cancer patients. Bony registration on the spine, and soft-tissue registrations on the primary gross tumor volume (GTV-T) and GTV-Total, including malignant lymph nodes (GTV-N), were retrospectively analyzed. Setup-margins and resulting PTVs were calculated.
  
  
  
  For the spine, the smallest residual misalignments were observed in FB, independently of registration method. For GTV-T and GTV-N, soft-tissue registrations were superior to bony registration, independently of FB or DIBH. Compared to FB, PTV-Totals were during DIBH reduced by 13% and 8% for the soft-tissue and bony registrations, respectively. If intra-fractional motion was included, the corresponding gain of DIBH was reduced to 9% and 7%, respectively. Superiority of DIBH was mainly due to larger clinical target volumes in FB.
  
  
  
  Despite larger setup uncertainties compared to FB, DIBH resulted in smaller PTV-Totals for all registration methods. Soft-tissue registrations were superior to bony registration, independently of FB and DIBH. During DIBH, undesirable arching of the back was identified. Daily CBCT pre-treatment target verification is advised.
authors.affiliation: Department of Oncology, Radiotherapy Research Unit, Herlev Hospital, University of Copenhagen, Denmark; Center for Nuclear Technologies, Technical University of Denmark, Roskilde, Denmark. Electronic address: wivott01@heh.regionh.dk.
authors.forename: Wiviann
authors.initials: W
authors.lastname: Ottosson
authors.affiliation: Department of Oncology, Radiotherapy Research Unit, Herlev Hospital, University of Copenhagen, Denmark.
authors.forename: Fatma
authors.initials: F
authors.lastname: Rahma
authors.affiliation: Department of Oncology, Radiotherapy Research Unit, Herlev Hospital, University of Copenhagen, Denmark.
authors.forename: David
authors.initials: D
authors.lastname: Sjöström
authors.affiliation: Department of Oncology, Radiotherapy Research Unit, Herlev Hospital, University of Copenhagen, Denmark.
authors.forename: Claus F
authors.initials: CF
authors.lastname: Behrens
authors.affiliation: Department of Oncology, Radiotherapy Research Unit, Herlev Hospital, University of Copenhagen, Denmark; Center for Nuclear Technologies, Technical University of Denmark, Roskilde, Denmark.
authors.forename: Patrik
authors.initials: P
authors.lastname: Sibolt
mesh_terms: D062485:Breath Holding; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D047368:Tumor Burden; D035501:Uncertainty
keywords: CBCT imaging; DIBH; Lung cancer; Margins; Setup methods