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"Heart scans" are not always heart scans

Posted Aug 26 2008 4:17pm

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

http://www.webmd.com/cancer/news/20070717/ct-heart-scan-radiation-cancer-risk.



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.

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