Imaging Technology News - January/February 2009 - (Page 7)

Feature RADIATION THERAPY RT Solutions for Troublesome Tumors New approach to technology gives IMRT, SRS a boost. Radiotherapy technology by Varian Medical Systems reportedly offers all the benefits of IMRT in dramatically shorter treatment times. By Amy Lillard W hile gated imaging has made significant strides in improving precision and accuracy in delivering radiation dose, the radiation oncologist’s bane still remains how to avoid radiating surrounding healthy tissue. In the last year, there have been enhancements to existing technologies, in particular intensitymodulated radiation therapy (IMRT), imageguided radiation therapy (IGRT) and stereotactic radiosurgery (SRS), that have made precision more accurate than ever. But which of these systems most effectively narrows margins, targets moving tumors and also limits side effects? tumor and the surrounding organs to contour the shape of radiation beams to the exact size and shape of the tumor. Still, the dynamic and irregular shape of tumors often results in exposing healthy tissue to radiation. In response to the need to deliver high-intensity doses with greater precision, manufacturers have improved upon existing technology - IMRT, IGRT and SRS systems - with faster and more agile delivery systems. “We’re making use of intensity modulation more these days for highly conformal plans,” said Jay Burmeister, Ph.D., DABR, chief of physics at Karmanos Cancer Center and director of education in radiation oncology, Wayne State University School of Medicine. “But when we move toward these highly conformal treatment plans, the risk is far greater. Certainly in the old days when we used radiation with much larger fields, we irradiated significant amounts of normal tissue, but tumor targeting was not as critical. Whereas here, if we’re ultra conformal, we can not only irradiate healthy tissue but miss part of the target as well. We have the potential for double jeopardy.” As a result, radiation oncology as a field is looking for tools to better target radiation, particularly for tumor movement. With the advent of highly advanced targeting technology, many radiation oncologists are able to provide more patient safety and better efficacy at the same time. we’ve used in the past is its dose distribution capability,” said Burmeister, a Hi-Art user. “When you incorporate rotational, helical delivery as opposed to a few discrete beams, you have the possibility for better plan quality, especially with complex cases. For a relatively simple convex tumor, you won’t find much difference between IMRT delivery systems. But when you’re trying to treat large or irregularly shaped targets, with organs at risk in close proximity, the rotational therapy with Hi-Art can be far superior to static-beam IMRT.” Burmeister and his clinic’s case distribution, including prostate, lung and head and neck tumors, features many tough jobs that defy con- Challenging Tumors, Increasing Demands One of the challenges of delivering radiation treatment is the dynamic nature of tumors. Because tumors move between and during treatments, oncologists compensate for this movement by either widening the margins surrounding the tumor or making the radiation beam larger. Additionally, many tumors are oddly shaped, difficult to access and nestled among critical organs. The radiation oncologist’s first recourse is in treatment planning, creating a 3D model of the We’re making use of intensity modulation more these days for highly conformal plans. — Jay Burmeister, Ph.D., DABR Karmanos Cancer Center The Need for Speed New technologies are enhancing IGRT targeting and treatment through multiple means, whether its helical radiation delivery, lightningfast dosing or a variety of arc choices. What distinguishes one system from the other is the method for dose distribution. The TomoTherapy Hi-Art system delivers radiation through beams emitted in a spiral. The goal and the result is a higher focus on the tumor and less on vulnerable surrounding structures. The TomoTherapy system involves creating a CT image immediately prior to treatment, enabling radiation oncologists to adjust the tumor position and radiation before and during treatment. The Hi-Art delivers radiation continuously with thousands of narrow beamlets, from all angles around the patient, all targeting the specific tumor position and shape. “What separates Hi-Art from other systems CyberKnife is a noninvasive frameless stereotactic radiosurgery system that enables stereotactic radiosurgery anywhere in the body. ventional IMRT. As such, the Tomo system is often their go-to machine for complex cases. “The way the Tomo treats patients is fundamentally different than static-beam IMRT,” said Burmeister. “In addition to the increased number of IMRT beamlets available, you end up treating individual regions of tissue in shorter time, even though the overall treatment time could be longer. Since patients are moved through a slit of radiation, the time for any individual volume of tissue to receive its radiation dose is smaller than for conventional IMRT. Getting the absorbed dose into the target in a shorter amount of time prevents tumor cells from repairing during a treatment course. Tomotherapy and volumetric arc therapies share this advantage over traditional IMRT delivery methods.” The Varian Medical Systems RapidArc combines the use of both IMRT and IGRT to deliver a treatment in less than two minutes. By producing as little as 600 MU per fraction compared to up to 3,000 MU in conventional IMRT, using a single 360-degree rotation and shaving treatment time to two minutes or less, radiation is delivered to the whole volume of the tumor in record time, minimizing discomfort and side effects. At the Center for Radiation Therapy in Beverly Hills, Suzanne Evans, RTT, utilizes the Radiation Therapy continued on page 8 ITNonline.net | Jan/Feb 2009 | ITN | 7 http://www.ITNonline.net

Table of Contents Feed for the Digital Edition of Imaging Technology News - January/February 2009

Imaging Technology News - January/February 2009 Contents IMRT Imaging RT Solutions for Troublesome Tumors PACS Radiology to Close the Imaging Loop Will Web-Based PACS Take Over? Is CT Dose Under Control? The Best in Digital Mammography Breast Biopsy Systems MX Series Monitors Provide University of Pennsylvania Quality Assurance Reduce Waste to Raise Revenue

Imaging Technology News - January/February 2009

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