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lrogers{at}ajroffice.org
Or a less abbreviated, more circumspect response might be, "Hey, there's more to this CT dose reduction than we thought. It is not as simple as it seemed initially, but we're working on it."
Then again, you might also encounter a longer, more telling, evasive reply beginning with, "Well, exposure dose in CT is a most complex issue." And, after a clearing of the throat, "We are quite busy. Our referring physicians have come to expect high-quality CT examinations. Indeed, the demand for CT has been so great that we have not, as yet, found the time to modify our examination techniques to lower exposure doses. We are really short-handed right now. We do, however, plan to look into changing our CT parameters sometime soon." And then, after a pregnant pause, "We really don't examine many kids. Why do you ask? Is there some government regulation or reimbursement situation that we haven't heard about that requires us to lower the CT exposure dose?"
It has now been 2 years since the piece by Brenner et al. [1] and the related articles [2, 3] appeared in the AJR and created quite a clamor about the potential implications of radiation doses received by children undergoing CT. Public interest may have waned since then, but the profession, indeed the entire radiology community—radiologists, physicists, radiobiologists, manufacturers, and, yes, even government regulators and overseers—has responded favorably to the alert by Brenner et al. A great deal has been accomplished.
I daresay, by now, most radiology practices have appropriately modified their CT examination parameters to sharply reduce the radiation exposure received by children. And if you have not, shame on you, because you should have.
More and more evidence has appeared in the radiology literature that tells us, in most circumstances, CT exposure doses could also be significantly reduced in adults. Two such articles [4, 5] appear in this issue. Tack et al. [4] report success with the use of only 30 mAs in multidetector CT of patients with suspected renal colic. Katz et al. [5] follow with a commentary that provides an excellent review of the issues surrounding CT dose reduction in general and for adults in particular. These articles certainly provide a primer on CT-dose reduction in adults.
Last November, the National Council on Radiation Protection and Measurements (NCRP), underwritten with a grant from the Diagnostic Imaging Branch of the National Cancer Institute, convened a symposium entitled Computed Tomography: Patient Dose. The intent was to bring all concerned parties to the table, to empanel an entire team: radiologists, physicists, radiobiologists, manufacturers, and state and federal regulators to review the current status of CT dose reduction and to formulate recommendations for future strategies to encourage, support, and lend direction to these efforts. The meeting was a success; its laudable goals were achieved.
At this meeting, radiologists provided the appropriate clinical background. The CT accreditation program of the American College of Radiology received the plaudits of those assembled. Physicists explored the problems of dose measurement in CT and drew attention to the need for a standard definition as well a standard means of measuring CT exposure dose.
Radiobiologists reviewed the threshold/no threshold radiation effect as it applies to the doses received in CT. This remains quite a contentious issue: good people on both sides of the equation have chosen to disagree, with no agreement in the immediate offing. The threshold/no threshold argument should be set aside and not derail our push to reduce radiation exposure in CT, particularly in view of the fact that exposure dose in CT can be considerable to begin with and the potential incremental dose reduction is significant, on the order of 40-60% or more.
At the NCRP meeting, manufacturers reported on the various means that they have devised to reduce CT exposure and to display on the control panel the radiation dose delivered during a given CT examination. Manufacturers proudly extolled the dose-reducing virtues of their new CT equipment and trumpeted the dose-reducing benefits of add-on upgrades now available for existing machines. You are certain to hear about these developments at meetings and through the mails. The manufacturers' application specialists and tech reps have been brought up to speed on how best to adapt existing CT equipment to the requirement of reducing exposure. Call on them to help with yours.
And finally, state and federal regulators listened intently and seem to conclude that the CT-dose-reduction train is moving in the desired direction. They applauded the progress to date and announced that they will continue to monitor the situation closely; but apparently, in view of the collective progress to date, they see no need to take any new CT regulatory initiatives at this time. Welcome news. Government regulation should assure patient safety but, at the same time, allow technical innovation and clinical improvements without compromise of patient care. To date, and much to the public's best interest, that is just what our regulators have done.
Exposure dose from CT was our dark secret that lurked in the shadows cast by the dazzling diagnostic capabilities of CT. It is good that the issue of CT exposure has been brought out into the light of day. Our patients are now better served. On examination, we have found that there is nothing to fear. CT exposure can be controlled, exposure doses have been reduced, and undoubtedly further reductions are on the way.
So, "How are we doing with low-dose CT?" Quite well, thank you. We all got together—radiologists, physicists, radiobiologists, manufacturers, and regulators—and we did it: we lowered the exposure doses in CT.
Congratulations! The drinks are on me!
References
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