RapidArc Delivery Techniques for IMRT

Varian Medical Systems Inc, Palo Alto, Calif, launches a major advance in radiotherapy treatment. Introduced to attendees at this year's ASTRO meeting in Los Angeles, the RapidArc is a form of volumetric arc therapy that operates up to eight times faster than conventional or helical IMRT. Tests have shown that RapidArc delivery can be executed in less than 2.5 minutes, with fewer than 750 MUs. Along with its time efficiency, it is capable of delivering precisely sculpted 3D dose distribution with a single 360° rotation of the linear accelerator gantry. According to Varian researchers, RapidArc therapy can conform the treatment beam more closely to the tumor shape, and therefore is well suited for a variety of clinical sites, such as the prostate, head, and neck.

Utilizing a sophisticated algorithm, RapidArc allows for the Varian linear accelerator to simultaneously change three parameters during treatment: the rotation speed of the gantry, the shape of the treatment aperture using the movement of multileaf collimator leaves, and the delivery dose rate. Varian said it is anticipating a product release date by next spring, pending FDA clearance.

The Spec Sheet

1. Leaf interdigitation, accomplished by a multileaf collimator
2. Sliding-window approach to beam shaping, whereby the collimator leaves are in constant motion
3. Patented gridded gun, allowing for varying of dose rate as a function of the gantry angle

The Visible Difference

Company officials call RapidArc a revolutionary game-changer in the IMRT field, as a delivery technique that aims to improve dose conformity while shortening treatment times by a significant amount. Because IMRT delivery time is reduced, RapidArc has the potential to improve the quality of care and patient comfort, in addition to fostering more affordable treatments in radiation oncology. According to Varian, with RapidArc, doses are much more precisely concentrated on tumors, allowing better protection for surrounding healthy tissues. The company also pointed out that current customers can adopt RapidArc without surrendering their ability to deliver other forms of treatment if needed.

A treatment plan for head and neck cancer using conventional IMRT.	A treatment plan for head and neck cancer using RapidArc delivery. RapidArc achieves treatment objectives better than today's best IMRT techniques.