CT Scans are not all equal:  the machine matters

January 26, 2013

Jacob Schor ND, FABNO



X-ray computed tomography or what is commonly called a CT scan (but usually pronounced as cat scan) is a common technique for ‘seeing’ inside the body for medical purposes.   A computer is used to process multiple X-rays to produce images that appear as cross-sectional slices of the body.  These images can be further processed to generate three-dimensional images. In the last twenty years use of CT scans has increased dramatically.  In 2007 and estimated 72 million CT scans were performed in the United States. A June 2012 study in JAMA reported that CT scans have tripled in the last 15 years. The study, tells us the rate of CT scans per 1,000 American adults rose from 52 in 1996 to 149 in 2010, a growth rate of 7.8% per year.  While perhaps good for the economy, this growth may not be good for our health.  This increase in CT use doubled the mean annual per capita radiation exposure, along with doubling the percentage of the population receiving high exposures.   In the past it was thought that 0.4% of cancers in the United States were due to past CT radiation exposure, in 2007 it was estimated that the rate may have increased 1.5-2%.


It could be even higher now.


CT scans certainly are useful and typically it is thought that these benefits far outweigh the increased risk.  Yet for good reason few patients are happy about undergoing CT scans.  Many of our patients are subjected to CT scans at regular intervals to monitor the course of their disease or to warn of recurrence.  One doesn’t have to be an Einstein to figure out that this recurring radiation exposure may further damage DNA that is already in trouble and may in a way ‘feed’ their disease.


They are of course correct to worry but as CT scans are often seen as a necessary evil, what exactly could we do about it?  Well it turns out that there is something simple that we can do; we can be fussy about where they get the CT scan done.  Not all CT scanning machines are equal.


I had a fascinating conversation the other day with Diane Spalding who runs the CT scanners at Presbyterian St. Luke’s and Rocky Mountain Hospital for Children.  It seems that the amount of radiation exposure varies greatly by machine.  Not just by machine but also by which software is used to combine and enhance the images.  In particular one of their CT scanners, a Toshiba 320, exposes patients to 70% less radiation than the other machines in Denver.  Why aren’t all the hospitals using similar machines?  It sounds as if it is a matter of finances.  These are not cheap machines and once a hospital owns a machine, it is in no rush to replace it with a newer model.


If you have regular CT scans done to monitor your condition you might be well served to make the effort and have your scans done with this newer, safer machine.


This low dose machine is at Rocky Mountain Hospital for Children.  To schedule a scan call them at 303.839.6520.


These machines have another use that should be mentioned.  They can be used to accurately diagnose cardiac conditions and do so more accurately than many of the earlier, riskier, invasive techniques.  St Luke’s is shifting their protocol  to use these CT scanners to check out patients with acute chest pain to figure out whether they need to be hospitalized or can be sent home.


Here’s a link to a short video talking about the cardiac uses for these new CT scans:








JAMA. 2012 Jun 13;307(22):2400-9. doi: 10.1001/jama.2012.5960.

Use of diagnostic imaging studies and associated radiation exposure for patients enrolled in large integrated health care systems, 1996-2010.

Smith-Bindman R, Miglioretti DL, Johnson E, Lee C, Feigelson HS, Flynn M, Greenlee RT, Kruger RL, Hornbrook MC, Roblin D, Solberg LI, Vanneman N, Weinmann S, Williams AE.


N Engl J Med. 2007 Nov 29;357(22):2277-84.

Computed tomography--an increasing source of radiation exposure.

Brenner DJ, Hall EJ.