gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

Installation and preliminary testing of a newly designed patient setup and monitoring system for particle beam therapy

Meeting Abstract

  • M. Riboldi - Bioengineering, Politecnico di Milano University, Milano, Italy
  • A. Pella - Bioengineering, Politecnico di Milano University, Milano, Italy
  • B. Tagaste - Fondazione CNAO, Pavia, Italy
  • G. Baroni - Bioengineering, Politecnico di Milano University, Milano, Italy
  • M. Ciocca - Medical Physics, European Institute of Oncology, Milano, Italy
  • S. Rossi - Fondazione CNAO, Pavia, Italy
  • R. Orecchia - Fondazione CNAO, Pavia, Italy

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog161

doi: 10.3205/09ptcog161, urn:nbn:de:0183-09ptcog1617

Veröffentlicht: 24. September 2009

© 2009 Riboldi et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen ( Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.



Background: CNAO (Centro Nazionale di Adroterapia Oncologica) in Pavia (IT) is an upcoming facility for treating patients with scanned proton and carbon ion beams. The treatment rooms are currently being equipped with newly designed systems for patient setup and monitoring. Our approach to patient setup comprises patient preparation in a dedicated area, transport inside the bunker and automatic positioning, to be supervisioned by infrared optical tracking and X-ray imaging. In-room devices include: a 6 degrees of freedom (6DOF) couch (Patient Positioning System, PPS), an Optical Tracking System (OTS) for external localization and surveillance, and a X-ray imaging device (Patient Verification System, PVS).

Material and methods: Experimental tests to characterize the performance of in-room patient setup devices are currently ongoing in the first treatment room (single horizontal line). The PPS is a 6DOF robotic pantograph featuring a mechanical accuracy below ±0.3 mm and ±0.1°. The OTS is a three cameras system able to localize passive markers and laser spots within 0.2 mm in a 3x2x2 m volume. The PVS installed in this room is a stereoscopic X-ray imaging device suspended from the ceiling, that can rotate around the vertical axis according to the treatment table position. Both X-ray tubes and flat panels are deployed only during imaging, when the tubes pivot whereas the flat panels slide into position. Preliminary activities to investigate the accuracy of PVS were performed at the manufacturer's facility. The accuracy of PVS motion was determined by means of repeated measures, carried out with a high precision laser tracker (±0,01 mmm accuracy). Multiple reference points located on both X-ray tubes and panels were monitored, so that the position of each component could be measured independently. On site, the PPS was benchmarked vs. the OTS by means of a head phantom fitted with 4 passive markers. The PPS was moved in 6DOF within a ±5 mm and ±3° range from isocenter and the final position was measured with the OTS.

Results: A maximum deviation of 0.1 mm in reference points localization was observed over a ±180° continuous PVS rotation, independently of the rotational direction. The absolute PVS rotational accuracy, as determined by repeated PVS rotations at a 60° step, was never beyond the measurement precision, even when changing the starting PVS position over a ±120° range. The accuracy of X-ray tubes and flat panels motion when they are deployed for imaging measured 0.13 mm and 0.02 mm, correspondingly. The head phantom study performed on site showed an agreement between PPS and OTS (mean±SD) within 0.1±0.1 mm and 0.06±0.07° in 30 repeated measurements.

Conclusions: Our results show that sub-millimeter accuracy is available in PPS motion and OTS monitoring for accurate patient setup. Furthermore,the rotating PVS designed for horizontal beam lines ensures top level accuracy and repeatability for in-room X-ray imaging at any given table position (Figure 1 [Fig. 1]).