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Return to Doctors Develop New Ways to Reduce Radiation Exposure Overview

More on Doctors Develop New Ways to Reduce Radiation Exposure

Doctors Develop New Ways to Reduce Radiation Exposure

New York (Sep 22, 2010)

technician and patient at a CT scanner

Computed tomography (CT) scans are now commonplace in medicine and for good reason. They provide accurate images that improve diagnostic accuracy and guide treatment for a number of conditions. The downside is that they also expose patients to radiation and this is a drawback of increasing concern. Decades ago, patients may have had a few x-rays now and then. Today, they can have numerous scans with each one having a great deal more radiation than an x-ray.

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"The traditional dose of radiation from coronary CT angiography for the evaluation of coronary artery disease is equivalent to 1,000 chest radiographs," explains Andrew J. Einstein, M.D., an Assistant Attending Cardiologist at NewYork-Presbyterian/Columbia University Medical Center. Dr. Einstein wanted to help change this. So did Michael L. Loftus, M.D., a radiology resident at NewYork-Presbyterian/Weill Cornell Medical Center.

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The two physicians embarked on separate projects.

Reducing Radiation Exposure While Examining the Heart

Dr. Einstein's work explored using a volume CT scanner during angiography to examine the heart's coronary arteries. A volume scanner is a special type of CT scanner able to capture an image of the entire heart at one time over a single heartbeat. The machines are uncommon – NewYork-Presbyterian is the only hospital to have one in New York City – and expensive. But they offer improvements over a traditional helical CT scanner.

Traditional scanners can capture only approximately one to two inches of the heart at a time, forcing doctors to take multiple images over several heartbeats and stitch them together. The stitching doesn't always go well because the coronary arteries and heart move over the course of several heartbeats. As a result, the accuracy of the scans may be reduced. Plus, more x-rays can equal more exposure to radiation.

Andrew J. Einstein, M.D.
Andrew J. Einstein, M.D.

"The virtue of acquiring everything over a single heartbeat is that there is less potential for motion artifact and artifacts introduced by this stitching together," Dr. Einstein explained. "It is our belief that avoiding at least this one type of artifact will improve the quality of the images, which should translate into improved diagnosis."

Having access to a high-tech machine helped obtain an accurate image, but there was still work to do with regard to reducing the amount of radiation exposure patients may experience. "Our goal was to study and accurately characterize the amount of radiation that patients undergo from scans and see what the effects of various dose reduction methods are on the amount of radiation that patients receive," Dr. Einstein said.

After gathering data, Dr. Einstein worked to use a scanning mode that would use the minimum amount of radiation required, while still delivering a high-quality image. The results were dramatic. "What we found was that using an optimal combination of dose reduction methods we were able to reduce the dose of radiation by over 90%," reported Dr. Einstein. The findings were published in the March issue of Radiology (vol 254; no 3: 698-706).

Image of a human heart produced by a volume CT scanner. (courtesy of Dr. Einstein)

Dr. Einstein noted that the Hospital's continual pursuit of improved patient care is one of the many reasons why it is the top ranking cardiovascular institute in the New York Metropolitan area, according to US News & World Report. "The breadth and depth of expertise in the diagnosis and treatment of heart disease available at New York-Presbyterian is unsurpassed in the New York City area," he said.

Reducing Radiation Exposure While Examining the Brain

While Dr. Einstein's work focused on modifying the scans to reduce radiation exposure, Dr. Loftus' work focused on developing guidelines so that scans are used when they can obtain the best result (and, therefore, reduce or eliminate the need for additional scans). His study began as a quality improvement initiative designed to reduce radiation exposure in patients with aneurysmal subarachnoid hemorrhage (bleeding in the brain resulting from rupture of an artery or vein) – a population in whom the benefits of these scans greatly outweigh the potential harm.

Michael L. Loftus, M.D.
Michael L. Loftus, M.D.

His study concerned CT angiography (CTA) and CT perfusion studies, which offer more specialized imaging than standard CT scans of the head, but also expose patients to higher radiation doses. "Our goal is to use [these technologies] at optimal time points to maximize the benefit while minimizing the potential risks," said Dr. Loftus.

The researchers developed guidelines that describe the optimal time points to use the imaging studies and limits for the number of CTA and CT perfusion studies to be performed based on whether or not the patient is showing symptoms of subarachnoid hemorrhage (SAH) (such as a severe headache, vomiting, and confusion) and/or vasospasm (a spasm and constriction of blood vessels). The imaging guidelines were created by the neuro-radiologists in collaboration with physicians who order the studies, which Dr. Loftus said was essential for changing practice.

The algorithm included the following guidelines:

  • Patients without symptoms of aneurysmal SAH undergo a maximum of three CTA or CT perfusion examinations at 0-3, 6-8, and 10-14 days after aneurysmal SAH.
  • Patients with symptoms of aneurysmal SAH undergo an additional scan on the day of symptom onset for improved diagnostic accuracy for vasospasm.
  • Patients treated for vasospasm may undergo a follow-up scan 24-48 hours after treatment for assessment of adequate treatment response.
  • Importantly, the algorithm emphasizes end points in imaging these patients with CTA and CT perfusion, so as to limit further exposure to radiation.

Ten months after implementing the algorithm, the intervention was linked to a 32% reduction in the number of certain types of scans performed for each patient and a 12% decrease in overall radiation exposure. The study showed that "structured imaging guidelines can alter practice patterns when they are created in collaboration with the ordering physicians and they can result in improved utilization of imaging resources and improved patient safety." The findings were reported in the July issue of American Journal of Roentgenology (vol 195: 176-180).

CT scan of a human brain
A CT scan revealing veins and arteries in a
human brain. (courtesy of Dr. Loftus)

Many of the risks of radiation exposure from medical imaging are theoretical at this point and are based on the assumption that large amounts of radiation are harmful and, thus, lesser amounts are associated with incrementally smaller risks, Dr. Loftus explained. The theoretical risks include delayed wound healing, erythema, carcinogenic effects, and congenital defects; these effects are typically not seen at the dose levels used for most medical imaging, according to Dr. Loftus. "The minimal theoretical risks are outweighed by the benefits of the information that an appropriately ordered scan provides, especially in patients with aneurysmal subarachnoid hemorrhage," he said. "However, a particular goal of our department focuses on radiation safety and reducing radiation exposure to patients without compromising image quality."

The researchers hope to apply the principles behind the algorithm to other patient populations that undergo a frequent number of scans or high dose scans. This study is one example of the Hospital's "emphasis on critically evaluating and analyzing everything we do in an effort to constantly improve patient outcomes and experiences," Dr. Loftus said.

Contributing faculty for this article:

Andrew J. Einstein, M.D. is an Assistant Attending Cardiologist at NewYork-Presbyterian/Columbia University Medical Center and an Assistant Professor in the Department of Medicine (Cardiology Division) and Department of Radiology at Columbia University College of Physicians and Surgeons.

Michael L. Loftus, M.D. is a radiology resident at NewYork-Presbyterian/Weill Cornell Medical Center.

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