"Heart scans" are not always heart scans

Beware of the media reports now being issued that warn that "CT heart scans" pose a risk for cancer.

One report can be viewed at

This was triggered by a Columbia University study of risk for cancer based on the dose of radiation used in CT coronary angiograms. Theoretically, exposure to the radiation dose of CT coronary angiography can raise risk for cancer by 1 in 143 women if radiated in their 20s just from that single exposure.

If you've been following the Track Your Plaque discussion, as well as my diatribes in the Heart Scan Blog, you know that the media got it all wrong. The "heart scans" they are referring to are not the same as the heart scans that we discuss for the Track Your Plaque program.

A conventional heart scan (of the sort we refer to) exposes the recipient to 4 chest x-rays of radiation if an EBT device is used, around 8-10 chest x-rays of radiation if a 64-slice CT scanner is used. For the quality of information we obtain from these screening heart scans, we feel that it's an acceptable exposure.

The "heart scan" this study and subsequent reports refer to is not truly a screening heart scan, but a CT coronary angiogram, or CTA. CTAs are performed on the same CT or EBT devices, but involve far more radiation. CTA exposes the recipient to about 100 chest x-rays of radiation on a 64-slice device (more or less, depending on the way it is performed.) Just a couple of years ago, some centers were performing CTA on 16-slice devices, a practice I and the Track Your Plaque program vocally opposed, since up to 400 chest-rays of radiation were required! I even called a number of centers advising them that they were putting the public in jeopardy. CTAs also require injection of x-ray dye, just like any conventional angiogram.

CTA on 64-slice CT scanners require the same radiation exposure as a conventional heart catheterization, an issue glossed over in most conversations. In other words, the test that many of my colleageus so casually recommend poses a similar risk.

The message: the test I advocate for screening for coronary heart disease is a CT or EBT heart scan, not a CT coronary angiogram. CTA is a useful test and will get better and better as the engineers discover ways to reduce radiation exposure. But, in 2007, CTA is a diagnostic device, not a screening device. If you require an abdominal CT scan because your doctor suspects pancreatic cancer, or a CT scan of the brain because you might have a life-threatening aneurysm causing double-vision or seizures, it would be silly to not undergo the scan because of long-term and theoretical cancer risk.

But undergoing a CT coronary angiogram for screening purposes is ridiculous with present technology. I've said it before and I will say it--shout it--again:

CT coronary angiograms are not screening procedures; they are diagnostic procedures that should be taken seriously and do indeed pose measurable risk for cancer, a risk that is presently unacceptable for a screening test.

You wouldn't undergo a mammogram to screen for breast cancer if it exposed you to 100 chest x-rays of radiation, would you? Screening tests should be safe, reliable, accurate, and inexpensive. CT coronary angiography is none of these things. Genuine heart scans--the kind the Track Your Plaque program talks about and relies on--is all of those things.

Comments (6) -

  • Anonymous

    7/19/2007 12:16:00 AM |

    Dr. Davis, would you please specify the millisievert values you are assuming for chest x-ray, EBCT Ca score, MSCT Ca score, and CT angiogram? I just got a 64-slice Ca score and they told me I received an effective dose of 2 mSv. Would a CT angiography typically result in 20 mSv?

  • Dr. Davis

    7/19/2007 12:59:00 AM |


    Please see my Blog post, CT scans and radiation exposure at http://heartscanblog.blogspot.com/2007/06/ct-scans-and-radiation-exposure.html

    You may notice some differences. There's enormous variation in exposure, depending on how it's measured, how the scan is performed, type and manufacturer of scanner. However, you can get a good idea of ballpark figures from the table in the blog post.

  • Dr. Davis

    7/19/2007 1:02:00 AM |

    Let me try that URL again:


    Or, go to the left sidebar of Blog contents and see "CT scans and radiation"

  • JT

    7/22/2007 1:55:00 AM |

    I watch Fox news.  And with that statement I'm sure some are rolling their eyes.  Never before in the history of America has declaring what news channel one watches apparently pigeonholed one on their political views.  

    Like many I get my news from different locations: internet blogs, TV, radio, magazines, newspapers, etc, but in the morning I often watch Fox and Friends.  I do so for two reasons I suppose, the first being that I enjoy the joking around / humor on the set.  The second reason why I watch Fox is because it goes out of its way to present two sides of a debate.  It seems revolutionary what Fox has done to TV news - present two sides of a story.  Some people become terribly wound up over this.  On a personal note, I have an "ultra liberal" uncle, by his own definition, that in all honesty is so upset over Fox news and me watching it that he no longer communicates with me.  Uncle Gordon probably has never watched Fox News.  He only knows what he has heard.  And knowing him if he did watch he would only see the conservatives and not notice the liberal view point.  I hope one of these days he calms down and we can find ourselves on friendly terms again.  Change is hard for some to come to terms with.          

    When reading this blog, it disturbed me.  I wish that all news reporters tried harder to present two sides to a story. These high radiation reports would be easy to demonstrate as being only half true.  But instead, because of poorly researched, unprofessional reporting, there undoubtedly will be Americans that will decide to not have a life saving CT heart scan for fear of radiation poisoning.  And that is sad.

  • Dr. Davis

    7/22/2007 3:09:00 AM |

    Hi, JT--

    I couldn't agree more.

    If there's one theme that presents itself over and over lately, it is the struggle to discern the truth in the sea of information we're all presented with every day. I can only hope that we all zig-zag towards a real truth over time.

  • Darwin

    7/24/2007 6:34:00 PM |

    Re the CTCA - new study out concerning radiation exposure for young women.