On-line cone beam CT image guidance for vocal cord tumor targeting

Sarah O S Osman*, Hans C J de Boer, Eleftheria Astreinidou, Anne Gangsaas, Ben J M Heijmen, Peter C. Levendag

*Corresponding author for this work

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Background and purpose: We are developing a technique for highly focused vocal cord irradiation in early glottic carcinoma to optimally treat a target volume confined to a single cord. This technique, in contrast with the conventional methods, aims at sparing the healthy vocal cord. As such a technique requires sub-mm daily targeting accuracy to be effective, we investigate the accuracy achievable with on-line kV-cone beam CT (CBCT) corrections. Materials and methods: CBCT scans were obtained in 10 early glottic cancer patients in each treatment fraction. The grey value registration available in X-ray volume imaging (XVI) software (Elekta, Synergy) was applied to a volume of interest encompassing the thyroid cartilage. After application of the thus derived corrections, residue displacements with respect to the planning CT scan were measured at clearly identifiable relevant landmarks. The intra- and inter-observer variations were also measured. Results: While before correction the systematic displacements of the vocal cords were as large as 2.4 ± 3.3 mm (cranial-caudal population mean ± SD Σ), daily CBCT registration and correction reduced these values to less than 0.2 ± 0.5 mm in all directions. Random positioning errors (SD σ) were reduced to less than 1 mm. Correcting only for translations and not for rotations did not appreciably affect this accuracy. The residue random displacements partly stem from intra-observer variations (SD = 0.2-0.6 mm). Conclusion: The use of CBCT for daily image guidance in combination with standard mask fixation reduced systematic and random set-up errors of the vocal cords to <1 mm prior to the delivery of each fraction dose. Thus, this facilitates the high targeting precision required for a single vocal cord irradiation.

Original languageEnglish
Pages (from-to)8-13
Number of pages6
JournalRadiotherapy and Oncology
Volume93
Issue number1
DOIs
Publication statusPublished - 01 Oct 2009

Keywords

  • Cone beam CT
  • Glottic carcinoma
  • IGRT
  • On-line corrections
  • Voice preservation

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Hematology

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  • Cite this

    Osman, S. O. S., de Boer, H. C. J., Astreinidou, E., Gangsaas, A., Heijmen, B. J. M., & Levendag, P. C. (2009). On-line cone beam CT image guidance for vocal cord tumor targeting. Radiotherapy and Oncology, 93(1), 8-13. https://doi.org/10.1016/j.radonc.2009.05.015