CT scan radiation very low
Dear Dr. Roach: I became short of breath walking upstairs or during mild exercise, like walking a short distance. My stress test was normal, heart normal and blood pressure good. My doctor has ordered a coronary calcium score. Should I be concerned about the amount of radiation in this CT scan?
P.M. A coronary calcium score is performed by a special CT scanner. It determines the amount of calcium in the coronary arteries. There is a very good but not perfect correlation between calcium in the arteries of the heart and the likelihood of blockages in those arteries. Blockages can cause symptoms, and if they progress or rupture, they can cause a heart attack.
A normal coronary calcium, especially in combination with a normal stress test, makes significant blockages in the artery very unlikely.
All X-rays and CT scans use radiation. However, the amount of radiation from the most modern dedicated coronary calcium CT scanners — called an electron-beam CT — is very small: 0.6 mSv. This is only a little more than a mammogram.
A different test, the computed tomography angiogram (CTA), can give not only a calcium score, but it also uses dye to look at the inside of blood vessels. It gives information very nearly as good as an angiogram from cardiac catheterization. However, the radiation dose is much higher — as much as 1,200 mSv: about 200 times as much radiation.
There are still times when the CTA is the better test, but it is costlier in money, a larger radiation dose and dye (which can occasionally damage kidneys).
Dear Dr. Roach: I am a man, 79 and in good health with diabetes. Recently, I had a routine colonoscopy. One polyp was removed — it was benign — and I was diagnosed with diverticulosis. Eight days after the colonoscopy I began hemorrhaging blood. I spent the next eight days in intensive care, where they performed two colonoscopies, a sigmoidoscopy and a bleeding scan. I was told that if more air had been pumped in during the original colonoscopy, no perforation would have occurred. Is this accurate? Why did eight days lapse before the bleeding started?
F.C. A colonoscopy is a relatively safe test, but even without a biopsy, a colonoscopy can occasionally have a complication. When a biopsy is taken, the risk is higher of both bleeding and perforation.
When a polyp is removed during colonoscopy, the area is cauterized to stop bleeding. This causes a clot and/or scar tissue to form, protecting the area. Days after the procedure, the contents of the colon can scrape off the protective coating and allow the blood vessels to start bleeding again. Delayed bleeding is uncommon, but it's not rare: A one-centimetre polyp had approximately a 1% risk of delayed bleeding, but you had a much more protracted course than most.
I don't perform colonoscopy, but I did not read that more or less air in the colon is a risk factor for developing delayed bleeding. I am sure your physician would have taken all reasonable precautions, but delayed bleeding can happen even under the best conditions.