Preventing radiation damage in popular medical technique

November 26, 2000

At a major conference here this week, a team of medical physicists and radiologists is proposing guidelines for reducing the number of complications during an increasingly popular type of surgical approach, known as fluoroscopy-guided intervention. Performed over 700,000 times in U.S. hospitals last year, this approach typically involves threading a specially equipped catheter tube into a patient's body to perform an operation, more commonly termed an "intervention" among medical professionals, and monitoring the procedure's progress with x rays. However, at least 100 documented cases show that fluoroscopy-guided intervention can "burn" or damage normal tissue. Now, at this week's meeting of the Radiological Society of North America (RSNA), radiologists and physicists at the University of Texas-Houston Medical School will explain how this outcome can be prevented, by making slight technical modifications and educating practitioners of this technique.

Fluoroscopy-guided intervention procedures are performed in many parts of the body, such as the brain, heart, and abdomen. For example, they can treat aneurysms in the brain, by equipping a catheter with special loops which can coil up to block the flow of blood inside the aneurysm. Compared to traditional surgery, the direct intervention approach has many advantages. By positioning a catheter into the area that needs to be treated, doctors can perform interventions inside the body without making any major cuts or incisions. This approach typically leads to shorter recovery times, and shorter hospital stays.

In addition, doctors obtain a continuous video image of the region that is being treated, in real time. They do this by using x-rays in conjunction with a special "contrast agent," typically an iodine-containing liquid, which is injected into the bloodstream to improve the visibility of the images. Sent into the body, the x rays provide a clear image of internal structures in the body. The iodine-containing contrast agent absorbs x rays particularly well. When injected into the bloodstream, it does a good job of delineating the body's network of blood vessels and showing activity in them.

Problems arise in fluoroscopy-guided intervention procedures because they can last for a long time, and this can bring in a continuous influx of x rays, says Louis Wagner, a medical physicist at the University of Texas Medical School in Houston and a member of the American Association of Physicists in Medicine, which is organizing several meetings at RSNA. The x-ray dose from fluoroscopy is low, on a second-to-second basis. However, constant use of these x-rays over a long period of time can cause tissue-damaging "radiation burns," he says.

Wagner has documented 75 of these "burns," and knows of over 100 injuries overall to patients and medical personnel. "We suspect there are a lot more injuries, and we want to get the word out on how to avoid them," he says.

Unfortunately, many medical practitioners may be unaware that these radiation-based tissue injuries are created, says Wagner, who will show a sequence of them at a weeklong exhibit taking place at the RSNA meeting.

The "burn" injuries can occur in the following way. Our bodies are made mostly of water. Sent into the body, x rays can ionize water molecules, meaning that they can remove one or more of their electrons and make them unstable. Water molecules therefore get transformed into "free radicals" which can then react with and destroy surrounding cellular matter. The longer the procedure, the more tissue damage can occur.

Preventing this damage is relatively simple, says Wagner. Ensuring that physicians are well-trained to complete such procedures promptly and efficiently is one way. Training physicians to administer x-ray doses efficiently in fluroscopy equipment is another. Knowing the visual signs of these injuries is yet another major step so that physicians can avoid affected skin in patients who need multiple procedures over a course of months to years. Lastly, he says, manufacturers can modify fluoroscopy equipment so that the x-rays come in short pulses rather than in continuous streams. They can also filter x-rays so that only the most useful x rays for imaging are used, lowering the overall dose.
Louis Wagner
Radiology Dept
University of Texas-Houston Medical School
713-500-7670, x2670

Titus Koenig, MD, et al., "Radiation Injury to the Skin Caused by Fluoroscopic Procedures: Lessons On Radiation Management," a scientific exhibit to be presented at the meeting of the Radiological Society of North America, Chicago, Illinois, November 26-December 1, 2000.

More information:
Radiological Society of North America

American Association of Physicists in Medicine
College Park, MD

American Institute of Physics

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