CT scans and radiation exposure



The NY Times ran an article called

With Rise in Radiation Exposure, Experts Urge Caution on Tests at

http://www.nytimes.com/2007/06/19/health/19cons.html?_r=1&adxnnl=1&oref=slogin&adxnnlx=1182254102-vQpytpx6W/Z9gvAaNPDZvA



“This is an absolutely sentinel event, a wake-up call,” said Dr. Fred A. Mettler Jr., principal investigator for the study, by the National Council on Radiation Protection. “Medical exposure now dwarfs that of all other sources.”


Where do CT heart scans fall?

Let's first take a look at exposure measured for different sorts of tests:



Typical effective radiation dose values

Computed tomography Milliseverts (mSv)

Head CT 1 – 2 mSv
Pelvis CT 3 – 4 mSv
Chest CT 5 – 7 mSv
Abdomen CT 5 – 7 mSv
Abdomen/pelvis CT 8 – 11 mSv
Coronary CT angiography 5 – 12 mSv

Non-CT Milliseverts (mSv)

Hand radiograph Less than 0.1 mSv
Chest radiograph Less than 0.1 mSv
Mammogram 0.3 – 0.6 mSv
Barium enema exam 3 – 6 mSv
Coronary angiogram 5 – 10 mSv
Sestamibi myocardial perfusion (per injection) 6 – 9 mSv
Thallium myocardial perfusion (per injection) 26 – 35 mSv

Source: Cynthia H. McCullough, Ph.D., Mayo Clinic, Rochester, MN


If you have a heart scan on an EBT device, then your exposure is 0.5-0.6 mSv, roughly the same as a mammogram or several standard chest x-rays.

A heart scan on a 16- or 64-slice multidetector device, your exposure is around 1.0-2.0 mSv, about the same as 2-3 mammograms, though dose can vary with this technology depending on how it is performed (gated to the EKG, device settings, etc.)

CT coronary angiography presents a different story. This is where radiation really escalates and puts the radiation exposure issue in the spotlight. As Dr. Cynthia McCullough's chart shows above, the radiation exposure with CT coronary angiograms is 5-12 mSv, the equivalent of 100 chest x-rays or 20 mammograms. Now that's a problem.

The exposure is about the same for a pelvic or abdominal CT. The problem is that some centers are using CT coronary angiograms as screening procedures and even advocating their use annually. This is where the alarm needs to be sounded. These tests, as wonderful as the information and image quality can be, are not screening tests. Just like a pelvic CT, they are diagnostic tests done for legimate medical questions. They are not screening tests to be applied broadly and used year after year.

Always be mindful of your radiation exposure, as the NY Times article rightly advises. However, don't be so frightened that you are kept from obtaining truly useful information from, for instance, a CT heart scan (not angiography) at a modest radiation cost.



Detail on radiation exposure with CT coronary angiograms on multidetector devices can be found at Hausleiter J, Meyer T, Hadamitzyky M et al. Radiation Dose Estimates From Cardiac Multislice Computed Tomography in Daily Practice: Impact of Different Scanning Protocols on Effective Dose Estimates. Circulation 2006;113:1305-1310, one of several studies on this issue.

Comments (8) -

  • Anonymous

    6/20/2007 1:13:00 AM |

    I had a calcium score scan on a 64-slice machine at the Morristown Hospital in New Jersey. No contrast was injected. The technician did three separate scans that included the lung, even thought I didn't for a lung scan. I wonder why three scans were taken. Does it mean that I had three times the radiation?

  • Dr. Davis

    6/20/2007 1:22:00 AM |

    Hi,
    Of course I can't comment specifically on what was done, but it is common practice to perform 1) a "scout" film for the technologist to identify the location of important "landmarks" like the sternum and the top and bottom of the heart to minimize the window of exposure, and 2) lung imaging as a routine part of  heart imaging, not necessarily an additional scan.

    If an additional and unrequested lung scan was performed, you may want to call and ask why this policy is in operation.

  • Anonymous

    6/21/2007 4:35:00 AM |

    What do you feel about yearly nuclear stress tests for people with CAD?  The radiation exposure seems high and the ability of a stress test to pick subtle changes in flow is low.  In the absence of symptoms it would appear that the common practice of nuclear stress tests for people with CAD is a questionable practice.

  • Dr. Davis

    6/21/2007 12:14:00 PM |

    I agree. The radiation is excessive. I tend to follow that route only when nothing else is possible. An alternative for stress testing is stress echocardiogram in its various forms, none of which involve radiation. They still suffer the other pitfalls of stress testing, of course, but do not involve radiation.

  • Mike

    12/20/2008 11:40:00 AM |

    I just launched a webiste that may answer some of your questions.  www.xrayrisk.com. It allows you to calculate your cancer risk based on studies you have had and answers some faq on radiation exposure and cancer.

  • Anonymous

    12/6/2009 12:52:26 AM |

    There are several ways to estimate your cancer risk - the best site for background information is probably the Image Gently campaign.

    The American College of Radiology has similar information pages for patients and the general public.

    To track your exposure, as Mike said there's the xrayrisk website.
    There's also a program for the iphone called Radiation Passport that tracks all of your radiation exposure and gives you the associated risk of developing cancer from your radiation exposure.

  • buy jeans

    11/3/2010 6:33:12 PM |

    CT coronary angiography presents a different story. This is where radiation really escalates and puts the radiation exposure issue in the spotlight. As Dr. Cynthia McCullough's chart shows above, the radiation exposure with CT coronary angiograms is 5-12 mSv, the equivalent of 100 chest x-rays or 20 mammograms. Now that's a problem.

  • Medical CT

    11/29/2010 4:34:03 AM |

    The CT scanner was originally designed to take pictures of the brain. Now it is much more advanced and is used for taking pictures of virtually any part of the body.

    The scanner is particularly good at testing for bleeding in the brain, for aneurysms (when the wall of an artery swells up), brain tumours and brain damage. It can also find tumours and abscesses throughout the body and is used to assess types of lung disease.

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A fictional tale of medical economics in heart disease

A fictional tale of medical economics in heart disease

Dr. Robert Connors is the hospital’s most prized cardiologist.

Practically a fixture in the cath lab, he generates more revenues for the hospital than any of his colleagues. Last year alone, he performed over 1500 procedures, bringing in $18 million dollars to the cath lab, $27 million to the hospital. Dr. Connors is very good at what he does: 55-years old, he has been involved in high-tech heart care since the “early days,” 25 years ago, when hospital procedures really began to take off.

Over his career, he has personally performed over 25,000 heart procedures and has built a reputation as a skilled operator of complex coronary procedures. Because of his skills, he enjoys a vigorous flow of referrals for procedures from dozens of primary care physicians. His skill has also earned him referrals from cardiologist colleagues who seek his abilities for difficult cases.

On any day, Dr. Connors typically schedules up to 12 procedures. His entire day is spent in the cath lab, usually from 7 am until 6 pm. He meets many patients for the first time on the catheterization laboratory table as staff shave their groin, preparing for the procedure. Much of the procedure itself is not even performed by Dr. Connors, but by one or another cardiologists-in-training, a “fellow,” or member of the fellowship the hospital proudly maintains as a clinical teaching institution. Nor will Dr. Connors talk to most patients at the close of the procedure. He leaves that to either the fellow or a nurse. Dr. Connors views himself as a procedural specialist, not someone who has to take care of patients. He gave up seeing patients in his office over 10 years ago.

Dr. Connors’ procedural enthusiasm gained him the attention of drug and medical device manufacturers. Because Dr. Connors lectures widely and advises colleagues, his comments can dramatically alter perceptions of the value of a technology. He has, on many occasions, catapulted an unpopular device to most-asked-for among colleagues, bringing millions of dollars in revenues to the manufacturer. One particularly lucrative arrangement he made around 10 years ago involved a “closure” device, a $400 single-use plug used to close the access site made during heart catheterizations. By swaying his colleagues at _______ Hospital, 50 orders per day (one per procedure) tallied $20,000 every day, $7.1 million dollars per year for the manufacturer. Although he’d used other devices on the market, the 5,000 shares of stock he was offered encouraged him to issue glowing comments to colleagues on the superiority of this specific brand of closure device. Now over 90% of all catheterizations at _______ Hospital conclude with the device manufactured by the company in which Dr. Connors maintains partial ownership.

Negative comments, on the other hand, topple other products when Dr. Connors sees fit to pan them. For this reason, device and drug manufacturers run straight to Dr. Connors to gain his good graces as soon as possible after a product is released into the market. Because the competition is just as likely to do the same, it has often come down to a bidding war, the company providing the most lucrative arrangement most likely to win.

Thus, Dr. Connors proudly boasts of how many times he has flown to Hawaii, Europe, and other exotic locations at industry expense. He also boasts of how, for $100,000 paid to him for a “consulting fee,” he can overturn the choice of products lining hospital shelves. As the hospital’s annual budget for coronary devices will top $84,000,000 this year, device manufacturers regard the sum paid Connors as a profitable investment.

Despite his lofty status in the hospital, Dr. Connors has long expressed a love-hate relationship with ________ Hospital. While he enjoys his work and has made a more than comfortable income, he has long felt that the hospital administration didn’t truly appreciate his contributions. Five years ago, he therefore demanded that he be made “Director of Research.” After all, he had hired a nurse to help him coordinate enrollment of patients into several device trials brought to him by medical device manufacturers. When he encountered an initial lukewarm response from hospital administrators, he threatened to take his “business” elsewhere to a competing hospital. Hospital administrators gave in. They provided him with the title he wanted, along with $100,000 annual “stipend.”

Just fiction? Make no bones about it: Cardiac care is business, big business. And there's money to be made, lots of it.


Copyright 2008 William Davis, MD

Comments (2) -

  • Anonymous

    3/23/2008 12:24:00 PM |

    For a chuckle thought to mention a  story this morning.  I pass on to others what you write about heart disease and my father has recently joined me in doing the same.  Dad lives in a small community in Florida and several of his neighbors are doctors.  One retired doctor dad recently met has found what you write of great interest.  After looking at your sight, he was telling my father that long before vitamin D became as popular as it has in the last few years, he had been urging his patients to supplement their diet with D3.  The doctor is apparently famous in his field as he is a pioneer in sex change procedures and medicines, which even though I know is serious for people that feel they need a sex change, I can't help but chuckle like a young boy at his former line of work.  My father was telling me that his doctor neighbor is in his 80s and yet would have never guessed it.  He looks like he is in his 50s or 60s.  The doctor credits taking vitamin D for most of life for his youthfulness.

    I better end this and make the internet rounds.  I have a few exotic car forum to visit.  The Porsche, Ferrari, Lotus, etc. high end car sights is where you find doctors hanging out.  It's like donut shops to cops.

  • Rich

    3/24/2008 5:07:00 AM |

    Dr. Davis: We need to get as many medical journalists as possible to read this and other brilliant posts by you.
    -Rich

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