Cutting-Edge Radiation Technology
SmartBeam High Resolution IMRT
The advances in radiation delivery made over the last 40 years were all designed around a single premise: Maximize dose to the tumor while minimizing dose to the surrounding normal tissue. The evolution of our science – from cerrobend blocks to 3D conformal therapy and now Intensity Modulated Radiation Therapy (IMRT) represents a continued reduction in dose delivered to normal tissues, leading to better outcomes. Varian Medical Systems has played a leading role in this evolution by developing advanced tools that optimize patient care.
With the introduction of the Millennium 120 multileaf collimator and CadPlan PLUS / Helios software, Varian’s SmartBeam IMRT can now deliver the highest resolution treatment ever. Use of high-resolution IMRT has proven to reduce radiation exposure to normal tissue by as much as 30% over conventional IMRT treatments while providing a more uniform dose to the target. This target uniformity is necessary if IMRT is to be used as a replacement for conventional therapy. The reduced dose to normal tissue permits the oncologist greater freedom to explore the clinical effects of target dose escalation with less patient risk.
An Integrated IMRT Process in the Battle Against Cancer
In the battle against cancer, you need the best weapons available. Varian’s SmartBeam high resolution IMRT is the only complete turnkey IMRT system available today, integrating treatment planning, delivery and verification into one seamless and comprehensive process.
The concept of IMRT is based on dividing the intensity of a radiation beam into a matrix of beam pixels which effectively pinpoints and destroys cancer cells while minimizing damage to surrounding healthy tissue. Using smaller and smaller pixels, high resolution IMRT more accurately shapes the radiation dose to the target and spares normal tissue.
Treatment planning for high resolution therapy depends on automated 3D image analysis, sophisticated segmentation tools and rapid, accurate dosimetric calculations. SmartBeam IMRT treatments are planned using the CadPlan PLUS / Helios system. Helios’s inverse planning completes the optimization process in as little as 15 minutes.
Optimized treatment plans are available in the VARiS® information system for automated delivery on the Clinac EX in
less than 15 minutes. The EX with the integrated 120 leaf MLC and Helios provides 2.5 by 5 mm pencil beam resolution, delivering the highest resolution available.
Throughout the clinical process, images acquired by XimaVision™ and PortalVision™ imaging systems identify position and treatment verification information. Varian’s Generation 6 system is the only system capable of providing precise, closed loop control, of the simulation, planning, delivery and verification process.
Smart IMRT Techniques & Planning
ELECTRONIC COMPENSATION: For many years, clinicians have used wedges and metal compensators to reduce “hot spots” within the treatment volume. However, wedges only adjust for homogeneity in one direction and metal compensators are time consuming to manufacture.
Varian’s CadPlan PLUS Forward Planning IMRT solution combined with the dynamic multileaf collimator provide the most efficient and effective tool for the reduction of “hot spots” caused by missing or inhomogeneous tissues.
CONFORMAL ARC THERAPY: Varian’s SmartBeam combines the advantages of arc therapy with 3D conformal therapy. The Conformal Arc Therapy option, available only on Varian’s dynamic MLC, will adjust the beam aperture to conform to the 3D projection of the tumor as it is rotated around the target.
Another technique used to reduce the dose to normal surrounding tissues and to control the “hot spots” within the target volume is referred to as “field within a field” or “multiple cone down therapy.” The dMLC software allows the clinician to link all of the coned down fields into a single treatment for fast easy delivery.
DYNAMIC IMRT: The ability to reduce the dose to normal tissues surrounding the tumor is a function of the resolution of the IMRT delivery. Increasing the resolution of a multiple static treatment ultimately leads to a sliding window technique. Varian, with the MLC-120, offers the highest resolution and therefore the greatest tissue sparing of any IMRT system.
The results are demonstrated on this Dose Volume Histrogram of a glioblastoma in close proximity to the optic nerve. (Data courtesy of Stanford University)
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