The CyberKnife® System as an Image-guided Intensity Modulated Radiotherapy Device: Rationale and Potential Clinical Applications for CyberKnife Robotic IMRT™
Donald B. Fuller, M.D., Radiation Oncologist Radiosurgery Medical Group (RSMG); CyberKnife Centers of San Diego
In clinical practice, the CyberKnife® Robotic Radiosurgery System has been almost exclusively used as a radiosurgical device, engineered to deliver conformal, ablative radiation treatments in one to five fractions to a wide variety of malignant lesions in the CNS, head and neck, lung, liver, pancreas, prostate and other sites.1-8 Although there is no medical reason why this device has not been used to deliver conventionally fractionated radiotherapy, this function has not previously been described, presumably due to the long treatment times associated with early-generation CyberKnife Systems. Nevertheless, the MultiPlan® Treatment Planning System is capable of computing very elegant intensity modulated radiotherapy (IMRT) dose distributions, and improvements in device efficiency have made the delivery of these IMRT plans feasible in clinical practice, thus leading to new CyberKnife treatment applications that would best be described as “Robotic IMRT™.”
The new CyberKnife VSI™ platform includes a number of enhancements that improve efficiency, including Sequential Optimization treatment planning, the Iris™ Variable Aperture Collimator (which allows for modulation of the beam during treatment9,15), the increased dose rate of a 1,000 MU/min linear accelerator and a 20% increase in robotic traversal speed. In addition, a treatment time reduction tool accessed during plan optimization allows the user to reduce the total number of treatment beams and nodes while still meeting treatment plan objectives.
Collectively, these enhancements create a device that can reduce treatment times by over half compared with predecessor CyberKnife Systems, while maintaining the precision and accuracy of the CyberKnife product.
