A comparative study between the imaging system and the optical tracking system in proton therapy at CNAO

Maxime Desplanques, Barbara Tagaste, Giulia Fontana, Andrea Pella, Marco Riboldi, Giovanni Fattori, Andrea Donno, Guido Baroni, Roberto Orecchia

Research output: Contribution to journalArticlepeer-review


The synergy between in-room imaging and optical tracking, in co-operation with highly accurate robotic patient handling represents a concept for patient-set-up which has been implemented at CNAO (Centro Nazionale di Adroterapia Oncologica). In-room imaging is based on a double oblique X-ray projection system; optical tracking consists of the detection of the position of spherical markers placed directly on the patient's skin or on the immobilization devices. These markers are used as external fiducials during patient positioning and dose delivery. This study reports the results of a comparative analysis between in-room imaging and optical tracking data for patient positioning within the framework of high-precision particle therapy. Differences between the optical tracking system (OTS) and the imaging system (IS) were on average within the expected localization accuracy. On the first 633 fractions for head and neck (H&N) set-up procedures, the corrections applied by the IS, after patient positioning using the OTS only, were for the mostly sub-millimetric regarding the translations (0.4±1.1 mm) and sub-gradual regarding the rotations (0.0°±0.8°). On the first 236 fractions for pelvis localizations the amplitude of the corrections applied by the IS after preliminary optical set-up correction were moderately higher and more dispersed (translations: 1.3±2.9 mm, rotations 0.1±0.9°). Although the indication of the OTS cannot replace information provided by in-room imaging devices and 2D-3D image registration, the reported data show that OTS preliminary correction might greatly support image-based patient set-up refinement and also provide a secondary, independent verification system for patient positioning.

Original languageEnglish
JournalJournal of Radiation Research
Issue numberSUPPL.1
Publication statusPublished - Jul 2013


  • head and neck
  • IGRT
  • optical tracking system
  • particle therapy
  • patient positioning
  • pelvis localizations

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Radiation
  • Health, Toxicology and Mutagenesis


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