Monday, January 14, 2008

Radiation hazards of the 64 MSCT

We have been warning for the last 2 years that 64MSCT, commonly used in this country for full body and cardiac checkups, has a very severe radiation hazard. In fact, both the American College of Cardiology and the American Heart Association do not recommend the use of the 64MSCT as a screening tool for Coronary Artery Disease (CAD). This particularly because of the fact that the 64MSCT is not yet proven as a technique for the diagnosis of CAD.

On the average, the positive predictive value (it means that if the scan is positive, the patient has CAD as proven on coronary arteriography) of the 64MSCT in the diagnosis is about 93%, but the negative predictive value is about 98-99%. Therefore, the 64MSCT is very useful for telling us who does not have CAD. Obviously, that is not how it is used by some centers in this country. Every Tom, Dick or Harry (I suppose also Mary, Alice and Janet), can get a scan, it he or she can afford it (It is not cheap either, about RM 2,700).

What is even more harmful (besides taxing the purse) is that a 64MSCT angiogram, subjects the patient to as much radiation as the usually "gold standard" coronary angiogram (namely about 500 CXRs). That is a lot of radiation. A total body checkup 64MSCT scan, carries with it the equivalent radiation of about 2,000 CXRs. What is worse, the scan centers seldom warn the patients about this risk. I have seen many (rather anxious) patients who come to see me for a second opinion, who will tell me that they were never told the radiation risk.

Well this blog is posted now, because a group of radiologist from Switzerland have done a small study testing a 64MSCT machine (Prototype) where the cardiac scans are gated (time to take pictures) to scan the heart only at certain part of the cardiac cycle. They are trying to make the machine more efficient, so that the patient can be subjected to less radiation. The Swiss researches have reported that they can get good pictures with about 1/20 of the radiation. They are concern about the radiation, and maybe through their work, we can soon see a new way of doing the scans so that the patient gets less radiation hazard. That will be very good, especially if the accuracy can also be improved.

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