Image guidance in radiotherapy

Institute Quantivision (IQ) success story

Radiotherapy is an important treatment technique for cancer that 50% of cancer patients receive. Integrated image guidance (IGRT) systems have been recently introduced, enhancing the precision delivery to mm level in many situations. One of the most popular solutions is cone-beam CT integrated with the medical linear accelerators. Prof. M van Herk is the project leader of the IGRT research team at NKI that develops and implements cone-beam CT based IGRT software in-house since 2002. Since 2005 their software is marketed by Elekta Oncology systems. The NKI group acts as a subcontractor and delivers and maintains the entire image reconstruction and registration component to Elekta. Validation work of the system for certification purposes is done jointly.

Since 2005, the system has been extended by NKI to provide 4D image acquisition and analysis for lung radiotherapy, where respiratory motion would otherwise hamper the accuracy of image guidance (released 2010). The most recent release of the system occurred this year, and adds amongst others the possibility to provide patient imaging during rotational beam delivery.

The NKI software is licensed to one of the two big radiotherapy vendors. More than 80% of their machines that are being sold are equipped with our software. The market value of these IGRT enabled linear accelerators amounts to about 750 M euro per year for this vendor alone. Other venders are following suit.

The impact of IGRT on clinical care is enormous. For instance, the application of high-dose hypofractionated therapies has grown an order of magnitude the last 5 years due to increased certainty of delivery. The local control rate of this technique for small lung tumors is over 90% and it is therefore a viable, patient friendly and cheap option to replace surgery with less complications. In many cases, safety margins have been reduced thereby limiting the amount of complications and their associated management costs. The accuracy of delivery is now so high that target volume delineation is now the weakest link, and more the focus needs to be placed on diagnostic imaging to better initially localize the tumor.

The role of IQ in this process is to provide better imaging of the tumor, for instance by the integration of endoscopic images and optical coherence tomography into the target volume delineation process, improved quantitative (e.g. PET) imaging to provide better subvolume targeting and response monitoring, and the development of imaging techniques to study normal tissue damage close to the tumor.