title: The validity of surgical clips as radiographic markers for the tumour resection cavity in head and neck cancer treatment.
abstract: BACKGROUND
  A prerequisite of irradiation after advanced head and neck tumour resection is the accurate localization of the tumour resection margin. The purpose of the following study is to evaluate the use of surgical clips placed in the tumour resection margins for use as radiographic markers to facilitate focussed adjuvant radiation therapy.
  
  
  METHODS
  To evaluate whether the clips remain predictive for the resection margin, we analysed the deviation of each clip in two postoperative CT scans on different days. Bone registration points were used to fuse the two CT scans in the region of the primary tumour and the distances between corresponding clips were measured.
  
  
  RESULTS
  The tumour resection margins were labelled with an average of 18 titanium clips. In total 282 clips were evaluated. Metric analysis of clip deviation between the two postoperative CT scans found a mean distance of 4.5 mm ± 2.5 mm with a range of 0.5-11.8 mm. No significant statistical relationship of the clip differences as a function of time, the method of reconstruction or administered radiotherapy could be demonstrated.
  
  
  CONCLUSIONS
  Placement of surgical clips in the cavity walls after complete tumour resection provides an easy and inexpensive approach for defining resection margins and allows for increased accuracy of adjuvant treatment. Clinical trial number DRKS00007534.
authors.affiliation: Department of Oral and Maxillofacial Surgery, University Medical Center Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany. Electronic address: gido.bittermann@uniklinik-freiburg.de.
authors.forename: Gido
authors.initials: G
authors.lastname: Bittermann
authors.affiliation: Department of Oral and Maxillofacial Surgery, University Medical Center Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany.
authors.forename: Pit
authors.initials: P
authors.lastname: Voss
authors.affiliation: Department of Oral and Maxillofacial Surgery, University Medical Center Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Duttenhoefer
authors.affiliation: Oral and Maxillofacial Surgery, University Hannover, Carl-Neubergstr. 1, D-30625 Hannover, Germany.
authors.forename: Ruediger
authors.initials: R
authors.lastname: Zimmerer
authors.affiliation: Center for Medical Biometry and Medical Informatics, Institute for Medical Biometry and Statistics, Medical Center - University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany.
authors.forename: Kirstin
authors.initials: K
authors.lastname: Vach
authors.affiliation: Department of Oral and Maxillofacial Surgery, University Medical Center Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany.
authors.forename: Marc C
authors.initials: MC
authors.lastname: Metzger
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D057918:Fiducial Markers; D005500:Follow-Up Studies; D058752:Free Tissue Flaps / Q000637:transplantation; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D000072662:Margins of Excision; D037981:Neck Dissection / Q000379:methods; D011446:Prospective Studies; D018714:Radiotherapy, Adjuvant; D019651:Plastic Surgery Procedures / Q000379:methods; D015203:Reproducibility of Results; D013525:Surgical Instruments; D014025:Titanium / Q000737:chemistry; D014057:Tomography, X-Ray Computed / Q000379:methods*; D058106:Wound Closure Techniques
chemical_list: D001672:Biocompatible Materials; D014025:Titanium
keywords: Adjuvant radiotherapy; Clip migration; Clips; Tumour bed delineation