Are neck nodal volumes drawn on CT slices covered by standard three-field technique?

Giuseppe Sanguineti, Laura R. Culp, Eugene J. Endres, John E. Bayouth

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Purpose Several definitions have been proposed in the past few years on how to contour the various neck nodal levels on CT slices. However, whether the resulting nodal volumes would have been covered by standard techniques is unknown. The purpose of this study was to clarify this issue. Methods and materials Eight patients (N0-N1) with head-and-neck cancer from various primary sites referred to us for definitive radiotherapy were included in this study. Two observers contoured the level Ib-V neck nodal volumes on planning CT according to seven reported definitions. Each observer also drew blocks on digitally reconstructed radiographs for the initial (on-cord) phase of a standard three-field technique (parallel opposed lateral fields and AP supraclavicular field) for three different clinical settings: "medium" larynx (to cover upper, mid, and low jugular nodes), "big" larynx (same as for medium, plus posterior cervical nodes), and "tonsil" (same as for big plus retropharyngeal nodes). Fields blocks were concentrically reduced 5 mm in all directions as a surrogate for the clinical target volume to planning target volume expansion. A plan was created for each of the clinical settings, delivering 2 Gy to the International Commission on Radiation Units and Measurements reference point. The coverage of the nodal levels according to the various definitions was investigated throughout the analysis of the volume receiving 50%, 80%, and 95% of the prescribed dose (V50, V 80, and V95, respectively) and dose covering at least 95% of the volume (D95) values extracted from their cumulative dose-volume histograms in the three clinical settings. Results The V 50 coverage of levels III and IV was adequate for all definitions and trials. For level V, about 3-5% of the volume was outside the 50% isodose of those trials that targeted the posterior cervical chain. Coverage of level Ib was highly dependent on the definition, with up to 21% of the volume outside the standard tonsillar fields. For level II, although the 50% isodose from the tonsillar fields seemed to encompass all definitions, this was not the case for the laryngeal trials. Overall, we found 20-30% of the volumes to be outside the 95% isodose, with larger percentages for levels II and V. Similarly the D 95 results showed all volumes to be underdosed; only about 45% and 65% of levels II and V, on average, received 95% of the prescription dose. Conclusion Within three different clinical settings, we showed that the current definitions provide nodal neck volumes that often fall outside the 50% and 95% isodose lines of the standard three-field technique. Because these volumes are routinely used to define nodal neck volumes for intensity-modulated radiotherapy, the dose-volume objectives of intensity-modulated radiotherapy may not be consistent with those traditionally achieved by the standard three-field technique.

Original languageEnglish
Pages (from-to)725-742
Number of pages18
JournalInternational Journal of Radiation Oncology Biology Physics
Volume59
Issue number3
DOIs
Publication statusPublished - Jul 1 2004

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Neck
Intensity-Modulated Radiotherapy
Larynx
Palatine Tonsil
dosage
Head and Neck Neoplasms
Prescriptions
larynx
radiation therapy
Radiotherapy
Radiation
planning
histograms
coverings
cancer

Keywords

  • Intensity-modulated radiotherapy
  • Neck nodal volumes
  • Standard three-field technique

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Radiation

Cite this

Are neck nodal volumes drawn on CT slices covered by standard three-field technique? / Sanguineti, Giuseppe; Culp, Laura R.; Endres, Eugene J.; Bayouth, John E.

In: International Journal of Radiation Oncology Biology Physics, Vol. 59, No. 3, 01.07.2004, p. 725-742.

Research output: Contribution to journalArticle

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N2 - Purpose Several definitions have been proposed in the past few years on how to contour the various neck nodal levels on CT slices. However, whether the resulting nodal volumes would have been covered by standard techniques is unknown. The purpose of this study was to clarify this issue. Methods and materials Eight patients (N0-N1) with head-and-neck cancer from various primary sites referred to us for definitive radiotherapy were included in this study. Two observers contoured the level Ib-V neck nodal volumes on planning CT according to seven reported definitions. Each observer also drew blocks on digitally reconstructed radiographs for the initial (on-cord) phase of a standard three-field technique (parallel opposed lateral fields and AP supraclavicular field) for three different clinical settings: "medium" larynx (to cover upper, mid, and low jugular nodes), "big" larynx (same as for medium, plus posterior cervical nodes), and "tonsil" (same as for big plus retropharyngeal nodes). Fields blocks were concentrically reduced 5 mm in all directions as a surrogate for the clinical target volume to planning target volume expansion. A plan was created for each of the clinical settings, delivering 2 Gy to the International Commission on Radiation Units and Measurements reference point. The coverage of the nodal levels according to the various definitions was investigated throughout the analysis of the volume receiving 50%, 80%, and 95% of the prescribed dose (V50, V 80, and V95, respectively) and dose covering at least 95% of the volume (D95) values extracted from their cumulative dose-volume histograms in the three clinical settings. Results The V 50 coverage of levels III and IV was adequate for all definitions and trials. For level V, about 3-5% of the volume was outside the 50% isodose of those trials that targeted the posterior cervical chain. Coverage of level Ib was highly dependent on the definition, with up to 21% of the volume outside the standard tonsillar fields. For level II, although the 50% isodose from the tonsillar fields seemed to encompass all definitions, this was not the case for the laryngeal trials. Overall, we found 20-30% of the volumes to be outside the 95% isodose, with larger percentages for levels II and V. Similarly the D 95 results showed all volumes to be underdosed; only about 45% and 65% of levels II and V, on average, received 95% of the prescription dose. Conclusion Within three different clinical settings, we showed that the current definitions provide nodal neck volumes that often fall outside the 50% and 95% isodose lines of the standard three-field technique. Because these volumes are routinely used to define nodal neck volumes for intensity-modulated radiotherapy, the dose-volume objectives of intensity-modulated radiotherapy may not be consistent with those traditionally achieved by the standard three-field technique.

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