title: Liquid fiducial marker performance during radiotherapy of locally advanced non small cell lung cancer.
abstract: We analysed the positional and structural stability of a long-term biodegradable liquid fiducial marker (BioXmark) for radiotherapy in patients with locally advanced lung cancer.
  
  
  
  Markers were injected via endoscopic- or endobronchial ultrasound in lymph nodes and reachable primary tumours. Marker volume and Hounsfield Units (HU) changing rates were estimated using breath-hold CBCT. Inter-fraction variation in marker position relative to gross tumour volume (GTV) position was established, as well as the inter-fraction variation in mediastinal marker registration relative to a carina registration through the treatment.
  
  
  
  Fifteen patients were included and 29 markers analysed. All markers that were in situ at planning were visible through the treatment. Mean HU was 902±165HU for lymph node and 991±219HU for tumour markers. Volume degradation rates were -5% in lymph nodes and -23% in primary tumours. Three-dimensional inter-fraction variation for marker position relative to the GTV position was -0.1±0.7mm in lymph nodes and -1.5±2.3mm in primary tumours. Inter-fraction variations in marker registration relative to carina registration were -0.4±1.2mm in left-right, 0.2±2.0mm in anterior-posterior and -0.5±2.0mm in cranio-caudal directions.
  
  
  
  The liquid fiducial markers were visible and stable in size and position throughout the treatment course.
authors.affiliation: Department of Oncology, University of Copenhagen, Denmark; Niels Bohr Institute, University of Copenhagen, Denmark. Electronic address: jonas.scherman.rydhoeg@regionh.dk.
authors.forename: Jonas Scherman
authors.initials: JS
authors.lastname: Rydhög
authors.affiliation: Department of Oncology, University of Copenhagen, Denmark.
authors.forename: Steen Riisgaard
authors.initials: SR
authors.lastname: Mortensen
authors.affiliation: Department of Clinical Medicine, Bispebjerg Hospital, Denmark.
authors.forename: Klaus Richter
authors.initials: KR
authors.lastname: Larsen
authors.affiliation: Copenhagen Academy for Medical Education and Simulation (CAMES), University of Copenhagen, Denmark; Department of Respiratory Medicine, Gentofte University Hospital, Hellerup, Denmark.
authors.forename: Paul
authors.initials: P
authors.lastname: Clementsen
authors.affiliation: DTU Nanotech, Department of Micro-and Nanotechnology, Technical University of Denmark, Lyngby, Denmark; Nanovi Radiotherapy A/S, Lyngby, Denmark.
authors.forename: Rasmus Irming
authors.initials: RI
authors.lastname: Jølck
authors.affiliation: Department of Oncology, University of Copenhagen, Denmark; Niels Bohr Institute, University of Copenhagen, Denmark.
authors.forename: Mirjana
authors.initials: M
authors.lastname: Josipovic
authors.affiliation: Department of Oncology, University of Copenhagen, Denmark; Niels Bohr Institute, University of Copenhagen, Denmark.
authors.forename: Marianne Camille
authors.initials: MC
authors.lastname: Aznar
authors.affiliation: Department of Oncology, University of Copenhagen, Denmark.
authors.forename: Lena
authors.initials: L
authors.lastname: Specht
authors.affiliation: DTU Nanotech, Department of Micro-and Nanotechnology, Technical University of Denmark, Lyngby, Denmark.
authors.forename: Thomas Lars
authors.initials: TL
authors.lastname: Andresen
authors.affiliation: Department of Oncology, University of Copenhagen, Denmark; Niels Bohr Institute, University of Copenhagen, Denmark.
authors.forename: Per Munck Af
authors.initials: PM
authors.lastname: Rosenschöld
authors.affiliation: Department of Oncology, University of Copenhagen, Denmark.
authors.forename: Gitte Fredberg
authors.initials: GF
authors.lastname: Persson
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D057918:Fiducial Markers; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D008198:Lymph Nodes / Q000000981:diagnostic imaging / Q000473:pathology; D009367:Neoplasm Staging; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014463:Ultrasonography
keywords: Image-guided radiotherapy; Liquid fiducial marker; Marker visibility; NSCLC