RapidArc or Volumetric Arc Therapy, or VMAT, brings together the most sophisticated technologies (including Intensity Modulated Radiation Therapy (IMRT), Image Guided Radiation Therapy (IGRT), On Board Imaging (OBI) and Cone Beam CT Scan (CBCT) in a treatment that significantly reduces treatment times and radiation exposure.
RapidArc technology from Varian Medical Systems, the world leader in radiation research and development, is the culmination and combination of all of these technologies, taking precision delivery and targeting to the next level, while delivering radiation often in less than 90 seconds per fraction.
RapidArc is an "IMRT Arc Therapy," which means that in a single rotation of the linac gantry, a precise IMRT plan is delivered following IGRT and OBI targeting. This "volumetric arc," often labeled VMAT, for volumetric arc therapy, enhances both the delivery and the targeting of prostate cancer radiation.
RapidArc creates a smoother, more highly shaped radiation treatment that is unlimited in its sophistication. When receiving a typical IMRT or IGRT treatment, the gantry of the linear accelerator rotates to several "fixed" beam angles to treat the prostate - for example usually 5 to 7 specific angled beams are used during each, each one delivering one-fifth or one-seventh of the total radiation for that day. Since these fields are limited to only certain angles, the ability for the radiation to avoid or be minimized to normal tissues is also limited. When receiving a RapidArc treatment, there are NO angles in which the beam stops. The treatment is delivered in one single rotation of the gantry around the body. Since there is no limitation to where and when the beam will be on or off, or how fast or slow it is being delivered from the linac, the physicist and physicians now have nearly unlimited choices and degrees of freedom to design an even more sophisticated and highly conformal treatment. The results are less normal, non-cancerous tissue in the high dose treatment fields, fewer side effects and less normal tissue damage.
RapidArc delivers radiation in 90 seconds or less; conventional IMRT and IGRT treatments take about 4-8 minutes to deliver radiation. Some types of radiation therapies, like Tomotherapy, may take up to 20 minutes to deliver radiation, while some experimental treatments for prostate cancer like Cyberknife, can take up to 40 minutes. Why is a fast treatment better? Remember that the prostate moves due to the bladder and rectal volumes, and in order to make sure that a treatment can be delivered accurately, targeting technologies like IGRT and CBCT must be employed seconds before the treatment beam is turned on, so that the prostate can be right in the exact and precise position. However, the longer that the treatment beam is on, the more chance that some minor shifts in the prostate position can occur. Thus, RapidArc provides even better targeting precision by ensuring that the treatment is started and completed with such speed that it actually decreases the chance that a minor shift in the prostate's position might occur - something that becomes much more likely when the treatment beam is on for 3, 4, 5, 10 or more minutes.
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