For the first time in the history of radiotherapy, a focused treatment dose can be precisely targeted to a respiration-induced moving tumour in the lung or the liver. As a result, surrounding healthy and sensitive tissue can be spared much more effectively. Since the system increases treatment accuracy, patients may benefit from reduced side effects and improved clinical results.
Respiration induced motion of lung and liver tumours make the accurate delivery of radiation to these lesions particularly challenging. Up to now, large areas around the tumour had to be treated in order to account for the patient's breathing and ensure that the entire tumour was covered with a sufficiently high treatment dose. This often resulted in a significant volume of healthy and often sensitive tissue being exposed to radiation, preventing physicians from using higher dose levels that could improve treatment outcomes. To spare surrounding normal tissue and to allow higher doses to be delivered, the radiation dose needs to be focused exclusively on the tumour.
"To further enhance our system for the treatment of lung and liver tumours BrainLAB has now complemented its X-Ray-based positioning technology with gating", explained Stefan Vilsmeier, CEO of BrainLAB. "With this new feature, physicians are able to confidently address tumour movement caused by the patient's breathing. Gating allows the radiation beam to be synchronized with the patient's breathing frequency. This means that physicians are able to interrupt the treatment beam in milliseconds and only continue to irradiate when the tumour is located exactly in the path of the beam."
Professor Guy Storme, Head of the Radiotherapy Department at the AZ-VUB Brussels, added: "The robotic couch of the ExacTrac system aligns the patient automatically for treatment. We have measured and published the system's set-up accuracy of around 1 mm, which is the basis for precise gated radiotherapy." (Yan H, et al.; "A phantom study on the positioning accuracy of the Novalis Body system". Med. Phys. 30 .12., December 2003.)
"Once the patient is precisely positioned, ExacTrac Adaptive Gating ensures that the dose delivery is much more accurately focused on the tumour compared to conventional radiotherapy approaches. The whole Adaptive Gating system is entirely automated, allowing us to reduce user interaction and thus keep sources of error to a minimum. In addition, we are now in a position to evaluate more promising dose delivery protocols where we can increase the dose over time. With the new ability to focus the dose on the moving tumour, we expect improved outcomes for our lung and liver tumour patients and reduced side-effects at the same time", added Professor Storme.
BrainLAB's Adaptive Respiratory Gating feature correlates internal tumour motion with the patient's breathing cycle. The system's proven millimeter targeting precision is the basis for delivering a focused dose to the target that is subject to respiration-induced movement. (Verellen D, Soete G, et al.; "Quality assurance of a system for improved target localization and patient set-up that combines real-time infrared tracking and stereoscopic X-ray imaging". Radiotherapy and Oncology 67 (2003) 129-141.) The system's sophisticated and easy to use software automates all treatment steps required for Adaptive Gating such as high-resolution imaging of the patient's internal anatomy, image verification, patient set-up and continuous tracking of the movement.
ExacTrac's infrared tracking technology enables automatic, multiple x-ray image acquisition during the patient's breathing cycle. These x-ray image sets allow the detection of the tumour's three-dimensional movement in relation to a previously implanted marker. The exact magnitude of tumour movement is calculated automatically in 3D, allowing precise synchronization of the "beam-on window" with the patient's breathing frequency.
BrainLAB, a privately held company headquartered in Munich, Germany, was founded in 1989 and is specialized in the development, manufacture, and marketing of medical technology for radiosurgery and radiotherapy, orthopaedics, neurosurgery, and ENT. Among the products developed by BrainLAB are software and hardware components for image-guided surgery and radiotherapy as well as integrated systems for stereotactic radiosurgery.
With about 3000 software applications on nearly 1400 systems installed in over 60 countries, BrainLAB is among the market leaders in image-guided medical technology. BrainLAB today employs more than 580 people worldwide and has 15 offices across Europe, Asia, North and South America. More BrainLAB news is available in this VMW issue's articles Improved treatment of bone fractures with BrainLAB's image-guided VectorVision trauma and Minimally invasive total knee replacement with computer-assisted surgical technique now performed at Abbott Northwestern Hospital.