Imaging Technology News 9/08

Feature IGRT How IGRT Better Targets the Prostate Cone beam imaging, proton therapy and radiopharmaceuticals hone in on prostate cancer. Amy Ballard, MEd, director of research, Arkansas Urology ne of the primary goals of radiation therapy of the prostate is maximizing dose delivery to the actual cancerous tissue and minimizing radiation exposure to healthy tissue and to insure that the cancer is continuously hit throughout treatment. However, precision of treatment in prostate cancer is especially challenging due to the location of the prostate situated in such close proximity to the bladder and the rectum and the tendency for the prostate to move. Yet new approaches to radiation therapy, such as cone-beam imaging, proton therapy and novel radiopharmaceuticals, are giving physicians a clearer view of how to effectively treat prostate cancer. O treatment. I know the prostate can move unexpectedly during treatment and if the prostate moves out of focus of my treatment beam, then I am under-dosing prostate cancer during those seconds when the prostate is out of my field. With Calypso, we know when that happens instantly and can reposition the field or the patient and make sure that none of our rads are wasted.” In addition to greater confidence in treating the target, the Calypso system has also expedited patient throughput, according to Dr. Sandler, because of its ability to align patients so quickly prior to the start of treatment. In terms of sideeffect reduction, Dr. Sandler has not observed a marked difference. He explained that theoretically the extra precision with the Calypso would decrease the amount of tissue exposed to radiation, which would in turn equate to better tolerated treatments. However, a clinical study has not yet been done to demonstrate its efficacy as it relates to side-effect reduction. patient. Because we use the treatment beam and it is the same energy we use to treat those patients, we don’t have that problem at all even with fairly large patients.” Low dosing to reduce side effects and quality image acquisition are the hallmarks of the new MVision technology. Divvy Up the Dose Although IGRT has made significant advancements in the field of radiation therapy treating prostate cancer, challenges still exist with accuracy. Because the nature of prostate cancer is multifocal and arises simultaneously in numerous areas, one expert in the field poses the question, “Does it makes sense to treat the entire gland with the same dose of radiation?” Adam P. Dicker, M.D., professor and interim chairman of the department of radiation oncology at Jefferson Medical College at Thomas Jefferson University in Philadelphia, PA, and leader of the radiation research and translational biology program at the Kimmel Cancer Center at Thomas Jefferson University Hospital, is a leading expert in the field of IGRT for prostate cancer and recently edited the book, “Image Guided Radiation Therapy of the Prostate.” He explained that regardless of the definitive treatment, whether it be surgery, radiation therapy or cryotherapy, the whole gland ends up being treated with the same dose of radiation. However, he discussed a new technology, proton therapy, being used in a few cancer centers currently that may allow treating the whole gland while delivering a higher dose of image-guided treatment to certain areas of the gland. “Theoretically protons should allow you to have less normal tissue treated because you can define the borders of the prostate and you can define where the beam is going to enter and where it is going to stop and your normal tissue should have minimal toxicity,” Dr. Dicker said. The only drawback with proton therapy is that it does not take into account organ motion. He explained, “They can’t right now modulate the beam and you can’t craft and shape the beam to the same level of precision that you can with photons. There is not a shred of data at the moment that supports the fact that there is a clinical benefit to protons. Protons will reduce toxicity, but there’s not a shred of data that supports that.” His hope is that cancer centers that use proton therapy participate in a clinical trial to gather Prostate continued on page 14 ITNonline.net | September 2008 | ITN | 13 GPS for the Body One such image-guided radiation therapy (IGRT) system, commonly referred to as the “GPS for the Body,” is the Calypso System, designed to provide clinicians with a non-ionizing means to efficiently and objectively measure and monitor organ motion during radiation therapy. It provides continuous real-time tracking identification of implanted Beacon transponders and is used to both set-up and perform tracking of the target organ throughout external beam radiation therapy. Nearly five years ago, Howard Sandler, M.D., professor of radiation oncology and senior associate chair of radiation oncology at the University of Michigan, participated in the initial clinical trials using the system. Commenting on how Calypso has impacted his treatment delivery, he said, “The main advantage is it allows me to be more secure at treating prostate cancer everyday because it allows for continuous tracking of the prostate throughout the Cone Beam Lowers the Dose Another IGRT system making a breakthrough in prostate cancer radiation therapy is Siemens’ MVision Megavoltage Cone Beam Imaging Package, which reduces the entire process of acquisition, reconstruction and registration to less than three minutes for patient positioning with a one-step click of a button. Guillaume Grousset, director of marketing, oncology care systems for Siemens Medical Solutions USA explained, “When [implants are used], MVision allows for extremely low-dose imaging and when I say low dose imaging I mean anywhere between one and three centigrade. One of the very interesting things with MVision is the same radiation we use for treatment, we use for imaging. We account for the dose used for imaging in the treatment plan.” In addition to low-dose imaging, MVision imaging also enables exceptional image acquisition in patients who may have metallic objects near the field of vision as a result of, for example, a hip replacement. In these instances, the MVision does not create any artifacts in the image even in challenging patients, according to Grousset. The MVision is also well-fitted to accommodate large patients. Grousset said, “Traditional kilovoltage imaging is not always powerful enough to go through large patients. You may end up doing a couple of rotations around the patient to acquire enough data to reconstruct your volumetric image and the big question mark is what is the dose to the Prostate motion documented in the daily report demonstrates the motion of the prostate of greater than 1 cm over six minutes. http://www.ITNonline.net

Table of Contents Feed for the Digital Edition of Imaging Technology News 9/08

Imaging Technology News 9/08 Contents IGRT How IGRT Targets the Prostate ASTRO Oncology Information Management Systems (OIMS) Imaging Leading the Intense Race Against Cancer SBRT - The New Treatment of Choice Top IMRT/IGRT Centers to Watch Molecular Imaging: Ready for the Limelight CR or DR in the ER? Have You Hit the Glass Ceiling?

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