RapidArc Rotational Radiation Therapy 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 Scanning (CBCT), in a treatment which significantly reduces treatment times and radiation exposure for the patient. RapidArc technology from Varian Medical Systems, the world leader in radiation research and development, is the culmination of combining all of these technologies. It takes precision delivery and targeting to the next level. RapidArc delivers radiation often in less than 90 seconds per fraction. RapidArc is an “IMRT Arc therapy” using a single rotation of the linac gantry to deliver a precise IMRT plan 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.
Using prostate cancer as an example: When receiving a typical IMRT or IGRT treatment, the gantry of the linear accelerator rotates to several fixed beam angles to treat the prostate – usually there are five to seven specific angled beams that are used during each, with each beam 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, non-cancerous tissues is also limited. However, when receiving a RapidArc treatment, there are NO angles in which the beam must stop. 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 plan for the patient. The result is that less normal tissue will be zapped with high doses in the treatment fields, which means fewer side effects and less normal tissue damage.
RapidArc delivers its radiation in 90 seconds or less. Conventional IMRT and IGRT treatments take about 4-8 minutes to deliver radiation, which is also quite speedy, but nothing compares to the speed of the state-of-the-art RapidArc. 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 in the exact and precise position. However, the longer the treatment beam is on, the more chance that some minor shifts in the prostate position can occur. Thus, RapidArc provides even more targeting precision by ensuring that the treatment is started and completed in such a fast period of time. It 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.