Comparison between infrared optical and stereoscopic X-ray technologies for patient setup in image guided stereotactic radiotherapy

Barbara Tagaste, Marco Riboldi, Maria F. Spadea, Simone Bellante, Guido Baroni, Raffaella Cambria, Cristina Garibaldi, Mario Ciocca, Gianpiero Catalano, Daniela Alterio, Roberto Orecchia

Research output: Contribution to journalArticlepeer-review


Purpose: To compare infrared (IR) optical vs. stereoscopic X-ray technologies for patient setup in image-guided stereotactic radiotherapy. Methods and Materials: Retrospective data analysis of 233 fractions in 127 patients treated with hypofractionated stereotactic radiotherapy was performed. Patient setup at the linear accelerator was carried out by means of combined IR optical localization and stereoscopic X-ray image fusion in 6 degrees of freedom (6D). Data were analyzed to evaluate the geometric and dosimetric discrepancy between the two patient setup strategies. Results: Differences between IR optical localization and 6D X-ray image fusion parameters were on average within the expected localization accuracy, as limited by CT image resolution (3 mm). A disagreement between the two systems below 1 mm in all directions was measured in patients treated for cranial tumors. In extracranial sites, larger discrepancies and higher variability were observed as a function of the initial patient alignment. The compensation of IR-detected rotational errors resulted in a significantly improved agreement with 6D X-ray image fusion. On the basis of the bony anatomy registrations, the measured differences were found not to be sensitive to patient breathing. The related dosimetric analysis showed that IR-based patient setup caused limited variations in three cases, with 7% maximum dose reduction in the clinical target volume and no dose increase in organs at risk. Conclusions: In conclusion, patient setup driven by IR external surrogates localization in 6D featured comparable accuracy with respect to procedures based on stereoscopic X-ray imaging.

Original languageEnglish
Pages (from-to)1706-1714
Number of pages9
JournalInternational Journal of Radiation Oncology Biology Physics
Issue number5
Publication statusPublished - Apr 1 2012


  • Image-guided radiotherapy
  • Patient setup
  • Stereotactic irradiation

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Radiation
  • Cancer Research


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