Intra and Interfraction Mediastinal Nodal Region Motion: Implications for Internal Target Volume Expansions

Jonathan G. Thomas, Rojano Kashani, James M. Balter, Daniel Tatro, Feng Ming Kong, Charlie C. Pan

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

The purpose of this study was to determine the intra and interfraction motion of mediastinal lymph node regions. Ten patients with nonsmall-cell lung cancer underwent controlled inhale and exhale computed tomography (CT) scans during two sessions (40 total datasets) and mediastinal nodal stations 1-8 were outlined. Corresponding CT scans from different sessions were registered to remove setup error and, in this reference frame, the centroid of each nodal station was compared for right-left (RL), anterior-posterior (AP), and superior-inferior (SI) displacement. In addition, an anisotropic volume expansion encompassing the change of the nodal region margins in all directions was used. Intrafraction displacement was determined by comparing same session inhale-exhale scans. Interfraction reproducibility of nodal regions was determined by comparing the same respiratory phase scans between two sessions. Intrafraction displacement of centroid varied between nodal stations. All nodal regions moved posteriorly and superiorly with exhalation, and inferior nodal stations showed the most motion. Based on anisotropic expansion, nodal regions expanded mostly in the RL direction from inhale to exhale. The interpatient variations in intrafraction displacement were large compared with the displacements themselves. Moreover, there was substantial interfractional displacement (∼5 mm). Mediastinal lymph node regions clearly move during breathing. In addition, deformation of nodal regions between inhale and exhale occurs. The degree of motion and deformation varies by station and by individual. This study indicates the potential advantage of characterizing individualized nodal region motion to safely maximize conformality of mediastinal nodal targets.

Original languageEnglish (US)
Pages (from-to)133-139
Number of pages7
JournalMedical Dosimetry
Volume34
Issue number2
DOIs
StatePublished - Jun 1 2009

Keywords

  • Interfraction motion
  • Intrafraction motion
  • Lung cancer
  • Mediastinal lymph node

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology
  • Oncology
  • Radiology Nuclear Medicine and imaging

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