Collimator angle influence on dose distribution optimization for vertebral metastases using volumetric modulated arc therapy

Pietro Mancosu, Luca Cozzi, Antonella Fogliata, Paola Lattuada, Giacomo Reggiori, Marie Claire Cantone, Pierina Navarria, Marta Scorsetti

Research output: Contribution to journalArticlepeer-review

Abstract

Purpose: The cylindrical symmetry of vertebrae favors the use of volumetric modulated arc therapy in generating a dose "hole" on the center of the vertebrae limiting the dose to the spinal cord. The authors have evaluated if collimator angle is a significant parameter for dose distribution optimization in vertebral metastases. Methods: Three patients with one-three vertebrae involved were considered. Twenty-one differently optimized plans (nine single-arc and 12 double-arc plans) were performed, testing various collimator angle positions. Clinical target volume was defined as the whole vertebrae, excluding the spinal cord canal. The planning target volume (PTV) was defined as CTV+5 mm. Dose prescription was 5×4 Gy2 with normalization to PTV mean dose. The dose at 1 cm3 of spinal cord was limited to 11.5Gy. Results: The best plans in terms of target coverage and spinal cord sparing were achieved by two arcs and Arc1-80°and Arc2-280° collimator angles for all the cases considered (i.e., leaf travel parallel to the spinal cord primary orientation). If one arc is used, only 80° reached the objectives. Conclusions: This study demonstrated the role of collimation rotation for the vertebrae metastasis irradiation, with the leaf travel parallel to the spinal cord primary orientation to be better than other solutions. Thus, optimal choice of collimator angle increases the optimization freedom to shape a desired dose distribution.

Original languageEnglish
Pages (from-to)4133-4137
Number of pages5
JournalMedical Physics
Volume37
Issue number8
DOIs
Publication statusPublished - Aug 2010

Keywords

  • planning optimization
  • RapidArc
  • spinal cord compression
  • volumetric modulated arc therapy (VMAT)

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

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