CT Perfusion Scans: Pretty Pictures, But No Better Treatments

CT perfusion scans, often done on patients suspected of having a stroke, produce beautiful, detailed pictures of the human brain undergoing oxygen deprivation and tissue damage. But they don’t do anything to advance treatment, according to candid radiologists. This adds a new layer to the story of massive radiation overdoses with these tests at some institutions with undertrained technologists and undertested machines.

Dr. George Lantos, an associate professor of radiology and neurology, Albert Einstein College of Medicine in the Bronx, explained it this way in a letter to the New York http://www.nytimes.com/2010/08/09/opinion/l09radiation.html?_r=1&ref=opinionTimes in response to the recent investigative piece on overdoses around the country:

One important point not emphasized in the article is that this is a case where diagnostic capability far exceeds accepted effective therapy. To date, the only widely used drug in acute stroke therapy is the clot-dissolving agent tissue plasminogen activator (tPA), approved by the Food and Drug Administration in 1996. The only imaging test required for the use of tPA is a computed tomography (CT) scan, done without the use of intravenously injected contrast material.

The purpose of the CT scan is to exclude brain hemorrhage, the presence of which frequently can’t be determined by physical examination alone. CT perfusion exams discussed in the article are very informative, giving precise, detailed images of the degree of nourishment of brain tissue and where such nourishment may be decreased during a stroke.

The problem is that there is no F.D.A.-approved therapy that uses the information from perfusion scans in the setting of acute stroke. Even the injection of the iodinated contrast material for this test is an “off label” application as far as the F.D.A.-approved package insert is concerned.

My stroke neurologists and I have decided that if treatment does not yet depend on the results, these tests should not be done outside the context of a clinical trial, no matter how beautiful and informative the images are. At our center, we have therefore not jumped on the bandwagon of routine CT perfusion tests in the setting of acute stroke, possibly sparing our patients the complications mentioned.

Dr. Lantos’s letter highlights a frequent problem for expensive American-style medicine: imaging technology runs ahead of effective treatments. This is true for several other kinds of CT scans, such as “virtual colonoscopies” done with CT scanners, and similar scans done on the heart’s arteries. In all these cases, careful questioning of the doctors will usually reveal that the results of the test will NOT change treatment one way or the other. The scans just yield nicely detailed images. For treatment, however, one has to look directly into the colon with a telescope-type device, or directly into the heart’s arteries with a catheter.

The whole set of letters on this issue in the Times are worth reading.

One from the American College of Radiology talks about how mandatory adoption of the ACR’s voluntary testing and accreditation program would go a long way toward reducing inadvertent overdoses.

Another talks about yet another aspect of unregulated, unnecessary radiation: from CT scans done in dentists’ offices.

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