Use multislice CT for coronary imaging only when EBCT is not available

I read with great interest your excellent May 27 online article, "Pediatric heart scans deliver high radiation dose," which depicts the alarmingly high effective radiation dose to radiosensitive breast structures during a multislice CT angiogram (http://www.dimag.com/showArticle.jhtml.?articleID=163701504).

An interesting presentation at the 2003 RSNA meeting revealed that even a simple coronary heart scan performed with a 16-slice spiral in an adult woman exposes her breasts to 3.7 rads. When challenged, the presenting radiologist could only defend the practice by stating her hope that her department "carefully examines the risk/benefit ratio before each scan."

Certainly, the risk needs to be kept low, and the benefit (of using a relatively invalidated spiral scanner for cardiac CT, often by radiology groups with little background in preventive cardiology) is questionable.

The effective dose to radiosensitive anterior structures from the electron-beam coronary heart scan procedure and electron-beam angiogram is markedly less than a 16-slice MSCT spiral for two reasons. The total dose with EBCT imaging is substantially lower, while the effective dose to breasts is modest, as only 17% of the total radiation passes anteriorly with this unique modality.

The total dose in adult MSCT angiograms is several times that of an electron-beam angiogram, which can accomplish the procedure at a fraction of the dose of a conventional angiogram. When it comes to effective doses to the breast, the discordance is greatly magnified. The importance of keeping procedure dose low is amplified for children, as their total cumulative lifetime exposure remains a question.

From an "information/millisievert" standpoint, a risk/benefit ratio, and certainly in accordance with the ALARA principle, one should consider using such a spiral scanner for coronary imaging only when there are no highly validated electron-beam CT scanners available.

-James Ehrlich, M.D.

President, Society for Responsible Preventive Imaging

Denver, CO