Stereotactic body radiation therapy: Evaluation of setup accuracy and targeting methods for a new couch integrated immobilization system

John H. Heinzerling, Lech Papiez, Stanley Chien, John Anderson, Kenneth Forster, Geoffrey Zhang, Robert Timmerman

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

A new stereotactic frame system was designed at Indiana University to utilize the precision motion control of newer accelerator couches and treat obese patients previously untreatable in other frame systems during stereotactic body radiation therapy (SBRT). The repositioning accuracy and target reproducibility of this frame was evaluated in the treatment of both lung and liver tumors. The external coordinate system on the new frame was validated using a phantom system. Translational motions were carried out using couch motors. Five patients were treated with SBRT and twenty-three verification CT scans were acquired. The displacement of the gross tumor volume (GTV) and adjacent vertebral body between the original CT scan and the verification CT scans was determined. The mean setup accuracy for the patient study was less than 5 mm. Mean displacement of the GTV was 3.0 mm (0.0-6.0 mm) in the lateral (x) direction, 4.1 mm (0.0-8.9 mm) in the superior-inferior (y) direction, and 2.6 mm (0.0-10.0 mm) in the cranio-caudal (z) direction. Comparison of vertebral body position showed mean displacement of 2.4 mm (0.0 to 8.0 mm), 1.9 mm (0.0 mm to 2.0 mm), and 0.9 mm (0.0 to 5.0 mm) for the same shift directions. Repositioning could be accurately carried out from an initial reference position using the treatment couch controllers. Adequate set-up accuracy using a frame system capable of accommodating wide girth patients was achieved and was comparable to other published studies for narrower frames. With these results, a 5 mm expansion for PTV margins remains the standard for our institution.

Original languageEnglish (US)
Pages (from-to)197-206
Number of pages10
JournalTechnology in Cancer Research and Treatment
Volume7
Issue number3
DOIs
StatePublished - Jun 2008

Keywords

  • Abdominal compression
  • Body frame
  • Immobilization
  • Radiosurgery
  • Stereotactic

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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