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February 5, 2009 -- 5:00pm EST

CT Heart Scans, Radiation and the Media
Aquilion™ ONE 320 detector rowA new study, published yesterday in JAMA, describes a wide variation in the measured radiation exposure from CT angiograms, depending on which of 50 centers did the scans, what methods were used and, to some extent, which scanner was used. This report predictably resulted in "glowing" headlines about CT angiograms -- and not the good kind of glowing.... Here's a sampling:

However, the point of this study was not to show that CT scans of the heart have suddenly been found to be dangerous! In fact, the doses recorded at the high end were what was considered "normal" less than a year ago (e.g. NY Times, June 29, 2008). Strikingly, as the accompanying editorial by Dr. Alfred Einstein states:

"The estimated overall median effective dose for CTA...was 12 mSv, somewhat less than the value reported in several earlier studies using 64-slice scanners."

What is actually real important news, for both medical professionals and patients, is that, using dose reduction strategies, CT angiograms of excellent quality were done with exposures of only 2.1 mSv, approximately what New York City residents are exposed to annually, just from walking around. That's why I titled Angioplasty.Org's coverage, "CT Scans of the Heart Can Be Done with Low Radiation Dose." That's news!

Michael Poon, MDAnd the implications for patients and professionals are profound. If you are a patient, says Dr. Michael Poon, past president of the SCCT, ask the imaging center where you have been sent for a CT angiogram, "'What method are you using to lower the dose?' And if they don't know what you're talking about, I would say, 'See you later!'"

For imaging professionals, the PROTECTION I study in JAMA has a clear message: learn the latest dose reduction strategies and work with your equipment vendor to implement them. With radiation at these low levels, CT angiography may mount a challenge to the most often-prescribed nuclear stress test, which carries radiation doses from 12-21 mSv. Of course, you never read headlines such as "Nuclear Stress Test Zaps Patients" because it's been around so long.

Ever since multislice CT scanners became available in 2002-2003, industry and the imaging profession have been working on ways to reduce the radiation exposure. The PROTECTION I study in JAMA shows some positive results, but since 2007, when that data was collected, technology has advanced significantly -- enough so that Dr. Tony DeFrance, for example, regularly performs 320-slice scans with Toshiba's AquilionOne scanner at 1 or 2 mSv. Likewise, physicians such as Dr. Michael Poon are using GE Lightspeed units, and getting in similar ranges. Philips and Siemens have also developed low dose strategies.

As evidenced at the start of this post, whenever a study about CT angiography is published, the popular press jumps on the story with accompanying "dreadlines", doing a disservice to the technology, those who practice it, and certainly to patients.

A shining, and unfortunately rare, exception to this recent spate of news stories, was Dr. Nancy Snyderman, Chief Medical Correspondent for NBC News, who discussed her own CT heart scan with Matt Lauer on yesterday's "Today Show" (video below).

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