Not that this is a new subject, as a very similar news story was covered just months ago, but it seems that a recent “study” has gotten a lot of media coverage after concluding that medical imaging is putting patients at a “high risk of radiation exposure.”

Via the New York Times:

Study Finds Radiation Risk for Patients

About 400,000 of those patients receive very high doses, more than the maximum annual exposure allowed for nuclear power plant employees or anyone else who works with radioactive material.

The paper, being published on Thursday, was based on a survey from 2005 to 2007 covering almost one million patients insured by UnitedHealthcare.

It did not estimate the number of cancer cases that the radiation might cause over the next several decades. But Dr. Rita Redberg, a cardiologist and researcher at the University of California, San Francisco, who has extensively studied the use of medical imaging, said it would probably result in tens of thousands of additional cancers.

Each individual patient is at relatively minor additional risk from the tests, Dr. Redberg said, but because they are given to so many people, the cumulative risk is significant.

“It’s certain that there are increased rates of cancer at low levels of radiation, and as you increase the levels of radiation, you increase cancer,” said Dr. Redberg, who was not connected with the new study.

….

“These procedures have a cost, not just in terms of dollars, but in terms of radiation risk,” Dr. Fazel said.

The researchers calculated the amount of radiation received by the patients by looking at insurance codes for various kinds of imaging tests. Exposure is measured in millisieverts; the average American receives about three millisieverts a year from all sources.

The paper found that in at least one of the three years, 1.9 percent of the UnitedHealthcare patients received at least 20 millisieverts of radiation, or nearly seven times the average. Of that group, about 10 percent, or 0.2 percent of all patients, received at least 50 millisieverts, more than the annual maximum that nuclear regulators allow.

Those figures suggest that about four million Americans receive cumulative doses exceeding 20 millisieverts a year.

Federal rules allow physicians to profit from the use of machines they own or lease. But Dr. Harlan M. Krumholz, a cardiologist at Yale and an author of the paper, said financial incentives were only part of the reason the number of tests had risen so fast.

“I think the central driver is more about culture than anything else,” Dr. Krumholz said. “People use imaging instead of examining the patient; they use imaging instead of talking to the patient.

“Patients should be asking the question: ‘Do I really need this test? Is the information in this test going to help in the decision-making process?’ ”

In many cases, there is little evidence that the routine use of scans helps physicians make better decisions, especially in cases where the treatments that follow are also of questionable efficacy.

These sensational reports are really starting to get on my nerves.   For one thing, the statement “It’s certain that there are increased rates of cancer at low levels of radiation, and as you increase the levels of radiation, you increase cancer,” is entirely wrong.   There is zero data to demonstrate that there is ANY increased risk when exposed to levels bellow 10,000 mrem.   (10,000 mrem = 100 mSv).   In fact, there is mounting evidence that any biological effect from such low levels of radiation is more likely to have net benefits rather than risks.

The fact that nuclear radiation workers are limited to 50 mSv of occupational exposure per year shouldn’t be used as some kind of benchmark of what is a “safe” level.   For one thing, that number only covers the occupational radiation exposure, so a worker may be exposed to more than 50 mSv annually, if you factor in the exposure they get when not at work.   The level is set very conservatively by the NRC and is intended to represent a level low enough to assure safety even if there is an error in dosimetry or an accidental exposure to higher levels.

The other thing to consider is that there is no real benefit to the worker from increased exposure to radiation.  This is an important consideration when workplace safety regulations are written.   If the worker receives additional radiation exposure because they are expected to work in a less shielded environment or by working more directly with materials.  On the other hand, medical tests do have a very tangible benefit.

It is also important to note that most patients who receive diagnostic radiology do not get anywhere near the levels quoted in the above article.   To get a total dose of 50 mSv or more, a person would need to have multiple imaging sessions.   The individuals who get such extensive imaging are not simply healthy patients who are getting routine scans to rule out possible problems, but rather are those who have complex medical issues which require imaging to diagnose and monitor.  For example, a person who requires multiple reconstructive surguries after a traumatic accident may require a CT scan before and after each surgury to assess their condition.  A person being treated for cancer may require periodic imaging to monitor the success of treatment and determine the best course of action.

It is totally inappropriate for the authors of this study, or for any professional, to speculate about the benefit of these diagnostic tests.  There may be some cases where they are overused or unnecessary, but each patient is an individual case and many certainly do benefit from diagnostic imaging. To say that “People use imaging instead of examining the patient; they use imaging instead of talking to the patient,” is a statement that ignores the realities of medicine and the complexities of the human body.   For most of history, doctors were forced to “guess” what was going on inside the body of  a patient.   They could ask questions and note symptoms, but in the end, knowing that “it hurts here” doesn’t always reveal why it hurts.   The human body is very complex and has numerous interdependent systems.   Doctors were simply flying blind, estimating what the most likely cause of a problem was. With such little information, it is easy to mistake a brain tumor for a migraine.

That all began to change with the invention of the X-ray.   For the first time, it was possible to actually see what was going on and observe the cause of problems directly.   Prior to the x-ray only invasive and dangerous exploratory surgery could provide such insight.    Yet the earliest x-rays were of little use for observing soft tissue and generally were limited to bone injuries.   They revolutionized the field of orthopedic medicine, but only later did x-rays become useful for general purpose diagnosis.

Today, x-ray imaging can be used for a far wider range of diagnostic procedures.  Better resolution imaging, digital processing, three dimensional rendering and other technologies have made x-ray imaging more useful than its earliest doctors could have dreamed.   The CT scan first arrived  in the late 1970’s.   CT scans can create thin “slices” of a patients body and display both bone and soft tissue.   In their early days, they were very expensive and only avaliable at a few hospitals.   Yet today, with cheaper computer systems, improved resolutions and other developments, CT scan machines have become widely avaliable and are better than ever.   They are now commonly used for evaluating traumatic injuries and diagnosing cancer.    Additionally, tests like PET scans and real-time surgical fluoroscopy are no longer confined to research institutions.

Today, doctors are no longer forced to find out what they’re dealing with the moment they open up a patient for surgery.   Whether or not this is really “necessary” is something that has been a matter of debate.   Sure, it is possible to conduct brain surgery without first having a number of accurate scans to show where blood vessels, neurological structures and bone are located and the condition that they are all in, but being surprised in this circumstance is generally not something that most would want.   Additionally, there are plenty of diagnostic imaging procedures that result in a clean bill of health.   Does this make them unnecessary?   It’s easy to say in hindsight that it was not necessary to preform a diagnostic procedure t0o look for something like a tumor, if none are found, but on occasion some are found and lives are saved.   Even for those who end up with a negative result, it does rule out one problem and can provide some peace of mind.

Imaging of the spine of a patient with scoliosis prior to corrective surgery
is shown by three methods: A traditional X-ray, a two dimensional CT-scan
and finally a Three dimensional rendering of CT-scan data. Note that the first
image onlygives a vague impression of how the bones are aligned. The second
gives a better idea, but only of one cross-section, and the third clearly shows
all the shapes and deformations to the individual vertebrae.
(click to enlarge)

Some real reasons for the increase in medical imaging include:

• It has become more avaliable and affordable
• The usefulness of diagnostic imaging has become more and more apparent to doctors
• New techniques mean that diagnostic imaging can be useful in circumstances where it previously was not of use
• The data it provides is better than ever
• Treatments and surgical methods are more complex and precise than ever before, making imaging data all the  more important

Of course, there are imaging methods that do not use ionizing radiation, such as MRI’s and ultrasound. All imaging techniques have their strengths and weaknesses. Whether an MRI or CT scan is the optimal method of imaging a given patient is ultimately something that should be the decision of a doctor.   When it is not apparent whether or not a condition is present, it should also be a doctor’s decision as to whether or not imaging is warranted.    Being told that “You might have cancer, but it’s more likely that you don’t,” does not necessarily mean that you shouldn’t get checked out.   Given the low risk associated with such procedures, it is worth it even if 90% of those screened turn out to be negative.

Additionally, it is worth considering that patients who receive heart surgery using real-time fluoroscopic angiograms to guide cathaders into their body have a much lower mortality than those who are operated on by more invasive options.    Orthopedic surgery also has higher success rates when it is guided by good imaging data.  In dentistry, many teeth have been saved from having to be pulled, by detecting cavities early by x-ray.    And while most mammograms come back showing no indication of cancer, a few do, and those save lives.

Does this make imaging unnecessary?   I don’t think so.   But then again, I have a vested interest in this kind of thing, because I don’t want to die.   Thus, if I have any indications of a medical problem and imaging is recommended, I’ll take it!   Just like my Junior Highschool shop teacher taught:  measure twice, cut once.  (or in some cases, don’t cut at all)

As always, the source recommended for objective information on radiation risk and safety, avaliable in plain English and from expert sources is HPS

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This entry was posted on Sunday, August 30th, 2009 at 3:10 pm and is filed under Bad Science, Culture, Good Science, Quackery, media. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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