Novalis project
The NOVALIS BODY project can be considered as a synthesis of the previous work in that the experience on image-guided radiotherapy (IGRT), intensity modulated radiotherapy (IMRT) and stereotactic radiosurgery (SRS) are combined.
At start-up the major clinical endpoints were the improvement of the stereotactic radiosurgery procedures for intracranial applications and extrapolation of the radiosurgery procedures for treatment of the prostate. Prior to the clinical implementation, both required investigating the generation of conformal dose distributions by means of intensity modulated radiosurgery (IMRS) and improvement of the then current methods in real-time target localization. The clinical implementation, in turn, required a multidisciplinary approach including Medical Physics, Radiation Oncology, Neurosurgery and Urology, enhancing the already existing collaboration.
NATIONAL AND INTERNATIONAL CONTEXT
Furthermore does ExacTrac’s unique combination of x-ray imaging and infrared tracking permit the correlation of the internal 3-dimensional tumor motion with the patient’s breathing cycle (Gating).
The UZ Brussel is world BETA-test center for the combination of infrared marker technology with X-ray imaging and an Amorphous Silicon detector for on-line target localization using a robotic treatment couch . The Novalis system is originally designed for intracranial stereotactic radiosurgery, yet where conventional radiosurgery devices are restricted to small (i.e. smaller than 3 cm) intracranial lesions, the NOVALIS system is limited to a 10 x 10 cm² field size only and not restricted to intracranial applications. The latter makes it possible to extend the radiosurgery technology to extracranial applications.
The NOVALIS BODY project is the result of an intense collaboration between BrainLAB and the UZ Brussel. It already leaded to interesting publications concerning medical physics as well as radiation oncology. In the past 5 years different new research topics have been added to the project. The latest topic that caught our interest is delivering breathing synchronized irradiations with the Novalis system using BrainLAB’s Adaptive Gating software. By that much more normal tissue is spared from radiation while maintaining uniform dose distribution to the tumor, contributing to reduced side effects and better treatment outcomes.
NOVALIS BODY combines the real-time tracking device for infrared markers (ExacTrac) with stereoscopic X-ray imaging. The system, consisting of 2 X-ray tubes and an amorphous silicon detector, has been developed to detect and correct set-up errors from outside the treatment room prior to the treatment. Two major functions are supported: Automated fusion of the actual treatment images with Digitally Reconstructed Radiographs (DRRs: based on CT information) representing the desired treatment position and Matching of implanted radio opaque markers. This approach has been successfully implemented and validated for clinical use in the treatment of prostate cancer.
Stereotactic radiosurgery is a painless therapy that works with radiation and is used to treat mainly brain tumors and other abnormalities of the brain. It is a non-surgical approach where high-dose radiation is applied to precisely defined areas of the brain. For accurate location of points inside the brain an external, three-dimensional frame of reference based on the Cartesian coordinate system is used. This method is called stereotaxy.
Stereotactic radiosurgery relies on a computer-assisted radiosurgery system like BrainSCAN that focuses multiple beams from different directions directly to the tumor or abnormality. When beams are applied from many different directions, the highest concentration is achieved where all the beams intersect, in the so-called isocenter of the treatment machine. At the same time, radiation exposure of surrounding healthy tissue and of critical structures such as the optic nerve or the brain stem are minimized, because dosage from each direction amounts to only a fraction of the total dose.
Radiosurgery treatment is recommended for arteriovenous malformations (also called AVMs), acoustic neuromas and tumors that are inaccessible to surgical means because they are either located deep in the brain or next to critical structures. In these cases radiosurgery offers an alternative to open craniotomy.
Novalis Shaped Beam Surgery is the most advanced method of performing Stereotactic Radiosurgery available today.
Novalis continuously shapes the treatment beam to match the size and shape of the tumor or AVM from all angles, ensuring that the lesion receives the fully prescribed dose while protecting healthy brain tissue.
The procedure is virtually painless, and the patient remains awake for the entire procedure. Furthermore, treatment with Novalis does not require lengthy hospital stays or rehabilitation. A patient can undergo treatment in the morning and return to normal routine by the afternoon.
Apart from dynamic conformal shaping the NOVALIS system also allows for Intensity Modulated Radiation Therapy (IMRT) techniques.
Extracranial lesions
In 2001 the UZ Brussel has started radiosurgery procedures for extracranial lesions such as prostate cancer and liver metastasis. This is made possible by combining a real-time tracking device for infrared markers (ExacTrac) and stereoscopic X-ray imaging, allowing for automated patient positioning at millimeter level, prior to the treatment. The NOVALIS BODY project, which is the result of an intense collaboration between BrainLAB and the UZ Brussel, achieved very positive results.