Precision Matters
In medicine, radiation has been used to treat cancer and other abnormalities with good results for almost one hundred years. Pure energy delivered in beams, radiation works by damaging the DNA of tumor cells so they can no longer reproduce.
Since the early 1990’s, the physicians and oncologists at the VCU Medical Center have been on a constant drive to deliver higher, more effective doses of radiation to tumors while sparing the surrounding normal tissue. In this effort, we have advanced through three technologies, each one building upon the previous to provide ever greater precision.
From Flashlight Beam to Laser Pointer
Although the technological explanations can be quite complex, the significance of our progress can be compared to the leap from a household flashlight to a high-tech laser pointer.
At the VCU Medical Center, our earliest use of radiation treatment was like focusing the beam of a flashlight on the center of the bull’s eye. The light hit the center target accurately, just as we intended, but the beam lit up the surrounding area as well. If the bull’s eye was the tumor, and the surrounding rings were healthy tissue, it would mean that healthy tissue also received radiation. Clearly, greater precision was needed.
Next, think about a laser pointer, which can produce a narrow beam of light that can be aimed with great exactitude and allows almost no spillover of light on nearby surfaces. This characterizes our capabilities in the 1990’s. And because of the greater precision, we could deliver higher doses of radiation with less damage to surrounding tissue.
Now imagine that the bull’s eye target is resting deep inside your brain, near important structures that allow you to think and move normally. Using the ExacTrac® guidance system to augment the accuracy of Trilogy™ real-time imaging and treatment, high doses of radiation can be delivered exactly to the target, with room to spare for the safety of those nearby structures.
At VCU, pioneering radiation physicists have advanced the use of image guided stereotactic techniques from treating problems confined to the head to our ability to treat the entire body. Imagine that bull’s eye inside a patient’s chest, moving up and down with the motion of their breathing. Today, for the first time ever, using real-time image guidance and computerized robotic positioning of the body, we can keep the beam of radiation exactly in the center of the target, even while the bull’s eye moves with breathing!
The benefits are tremendous: Many tumors that were considered inoperable because they are too close to a blood vessel or organ, can now be treated. Surrounding tissue is spared, and the precision with which we maintain a “safety margin” is greatly improved. Recovery is faster and outcomes are improved.
Three Great Leaps Forward
- Stereotactic Radiosurgery and Radiotherapy
- Intensity Modulated Radiotherapy
- Image-Guided Radiation Treatment
Here’s a more technical description of the major advances in precision that have happened over the past 20 years.
Stereotactic Radiosurgery (SRS) was the first big advance – the transition from flashlight to laser pointer. Stereotactic radiosurgery is medical terminology describing a radiation treatment that uses a 3-dimensional scanning device, along with other special equipment, to position the patient and precisely deliver a large radiation dose to a tumor or other target while sparing as much of the normal tissue as possible (given the degree of accuracy). Stereotactic Radiotherapy (SRT) uses the same technologies, but the radiation is divided over several treatments, instead of being given in a single dose.
SRS painlessly shrinks or eliminates tumors and abnormalities using focused beams of radiation. Though it’s called radiosurgery, it is a bloodless, non-invasive procedure that does not involve the making of any incisions. Recovery and healing are fast, and patients can resume normal activities shortly after treatment.
The two commonly used forms of SRS are the Gamma Knife® Cobalt-60 systems and systems like the Trilogy that use powerful linear accelerators to deliver beneficial radiation.
Intensity Modulated Radiotherapy (IMRT) was the second advance. IMRT is medical terminology for varying the intensity of the radiation beam, so that the radiation dose to the tumor is different (and greater) than to the surrounding normal tissue. IMRT further improved the precision with which radiation could be delivered, allowing physicians to use even higher doses.
Even this amount of precision has its limits. Changes in the exact position of a tumor can occur over the course of a treatment, due to body movement caused by breathing for example.
Image-Guided Radiotherapy and Radiosurgery (IGRT) is the newest leap forward. By combining the delivery of the radiation with the real-time imaging of cancer tumors and abnormalities in one system, physicians can now hit a moving target.
At the VCU Medical Center, we have taken the most advanced image-guided radiation treatment system in the world and enhanced it for even greater precision! We are the first center anywhere to combine Trilogy and the ExacTrac X-ray. Our oncologists and neurosurgeons can now deliver doses of radiation to tumors subject to movement with the greatest accuracy ever achieved.
