Stereotactic body radiation therapy (SBRT) and respiratory gating in lung cancer: dosimetric and radiobiological considerations

Tania De La Fuente Herman, Maria T. Vlachaki, Terence S. Herman, Kerry Hibbitts, Julie A. Stoner, Salahuddin Ahmad

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


The purpose of this study was to assess the impact of respiratory gating on tumor and normal tissue dosimetry in patients treated with SBRT for early stage non-small cell lung cancer (NSCLC). Twenty patients with stage I NSCLC were studied. Treatment planning was performed using four-dimensional computed tomography (4D CT) with free breathing (Plan I), near-end inhalation (Plan II), and near-end exhalation (Plan III). The prescription dose was 60 Gy in three fractions. The tumor displacement was most pronounced for lower peripheral lesions (average 7.0 mm, range 4.1-14.3 mm) when compared to upper peripheral (average 2.4mm, range 1.0-5.1 mm) or central lesions (average 2.9 mm, range 1.0-4.1 mm). In this study, the pencil beam convolution (PBC) algorithm with modified Batho power law for tissue heterogeneity was used for dose calculation. There were no significant differences in tumor and normal tissue dosimetry among the three gated plans. Tumor location however, significantly influenced tumor doses because of the necessity of respecting normal tissue constraints of centrally located structures. For plans I, II and III, average doses to central lesions were lower as compared with peripheral lesions by 4.88 Gy, 8.24 Gy and 6.93 Gy for minimum PTV and 0.98, 1.65 and 0.87 Gy for mean PTV dose, respectively. As a result, the mean single fraction equivalent dose (SFED) values were also lower for central compared to peripheral lesions. In addition, central lesions resulted in higher mean doses for lung, esophagus, and ipsilateral bronchus by 1.24, 1.93 and 7.75 Gy, respectively. These results indicate that the tumor location is the most important determinant of dosimetric optimization of SBRT plans. Respiratory gating proved unhelpful in the planning of these patients with severe COPD.

Original languageEnglish (US)
Pages (from-to)158-169
Number of pages12
JournalJournal of Applied Clinical Medical Physics
Issue number1
StatePublished - 2010
Externally publishedYes


  • 4D CT
  • Lung cancer
  • Radiobiological modeling
  • SBRT

ASJC Scopus subject areas

  • Radiation
  • Instrumentation
  • Radiology Nuclear Medicine and imaging


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