Review The European Society of Therapeutic Radiology and Oncology–European Institute of Radiotherapy (ESTRO–EIR) report on 3D CT-based in-room image guidance systems: A practical and technical review and guide Stine Korreman a , Coen Rasch b , Helen McNair c , Dirk Verellen d , Uwe Oelfke e , Philippe Maingon f , Ben Mijnheer b , Vincent Khoo c,g, * a Department of Radiation Oncology, The Finsen Centre, Rigshospitalet, Copenhagen, Denmark; b Department of Radiation Oncology, The Netherlands Cancer Institute/Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands; c Department of Clinical Oncology, Royal Marsden NHS Foundation Trust, Chelsea and Sutton, London, UK; d UZ Brussel, Oncologisch Centrum, Radiotherapie, Brussels, Belgium; e Department of Medical Physics in Radiation Oncology, Deutsches Krebsforschungzentrum, Heidelberg, Germany; f Département de Radiothérapie, Centre Georges-François-Leclerc, Dijon, France; g Institute of Cancer Research, Chelsea, London, UK article info Article history: Received 31 October 2009 Received in revised form 8 January 2010 Accepted 16 January 2010 Available online 12 February 2010 Keywords: 3D volumetric imaging Cone-beam CT Image-guided radiotherapy kV CT MV CT Quality assurance Radiotherapy abstract The past decade has provided many technological advances in radiotherapy. The European Institute of Radiotherapy (EIR) was established by the European Society of Therapeutic Radiology and Oncology (ESTRO) to provide current consensus statement with evidence-based and pragmatic guidelines on topics of practical relevance for radiation oncology. This report focuses primarily on 3D CT-based in-room image guidance (3DCT-IGRT) systems. It will provide an overview and current standing of 3DCT-IGRT systems addressing the rationale, objectives, principles, applications, and process pathways, both clinical and technical for treatment delivery and quality assurance. These are reviewed for four categories of solu- tions; kV CT and kV CBCT (cone-beam CT) as well as MV CT and MV CBCT. It will also provide a framework and checklist to consider the capability and functionality of these systems as well as the resources needed for implementation. Two different but typical clinical cases (tonsillar and prostate cancer) using 3DCT- IGRT are illustrated with workflow processes via feedback questionnaires from several large clinical cen- tres currently utilizing these systems. The feedback from these clinical centres demonstrates a wide var- iability based on local practices. This report whilst comprehensive is not exhaustive as this area of development remains a very active field for research and development. However, it should serve as a practical guide and framework for all professional groups within the field, focussed on clinicians, phys- icists and radiation therapy technologists interested in IGRT. Ó 2010 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 94 (2010) 129–144 This report from the European Society of Therapeutic Radiology and Oncology (ESTRO)–European Institute of Radiotherapy (EIR) aims to provide the necessary information to meet the needs of radiotherapy professionals interested in applying IGRT solutions. The report is specifically focused on 3DCT-IGRT systems and the process of use of these systems. For the major commercial IGRT solutions, specifications are given which have been updated at the time of completion of the report. However, the focus of this re- port is on generic rather than on specific manufacturer’s issues. The subject of the report is limited to 3DCT-IGRT systems, refer- ring by this only to equipment situated within the treatment room. This means that planar imaging is not covered, neither as 2-dimen- sional (2D) nor as orthogonal 2D–2D (‘semi-3D’) solution. Also the use of flat panel detectors for 2D imaging in systems intended for 3D imaging is not covered, although the possibility exists in some commercially available systems. This definition may limit the scope of the report, but the entire area of in-room IGRT systems would be too comprehensive to be covered in a single report. The subject of 3DCT-IGRT was chosen, as this is the most recent addi- tion to the spectrum of image guidance solutions which is in wide clinical use. This is therefore an area in which many clinics are, presently and in the near future, in the process of purchasing new equipment as well as implementing existing and newly ac- quired equipment into clinical use. This report does not attempt to benchmark different solutions, either generically or with respect to commercial availability, nor does it attempt to rank solutions. A comparison is not undertaken with other categories of in-room image guidance solutions but rather the report reviews the principles, limitations, applications, quality assurance and workflow issues related to the limited sub- ject of 3DCT-IGRT solutions. Additionally, the report attempts to establish the use of a standardized nomenclature or glossary in 0167-8140/$ - see front matter Ó 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.radonc.2010.01.004 * Corresponding author. Address: Department of Clinical Oncology, Royal Mars- den NHS Foundation Trust, Fulham Road, Chelsea, London SW3 6JJ, UK. E-mail address: vincent.khoo@rmh.nhs.uk (V. Khoo). Radiotherapy and Oncology 94 (2010) 129–144 Contents lists available at ScienceDirect Radiotherapy and Oncology journal homepage: www.thegreenjournal.com