Increased use of CT scans raises risk of higher radiation exposures
Tuesday, 30 November 1999 00:00 | 
| Radiology Conferences - RSNA 2007 |
ACR takes issue with a review article in which US researchers argue that the growth of CT scan use over the years has increased the risk of higher radiation exposures.
In a review article, US researchers argue that the growth of CT scan use over the years has increased the risk of higher radiation exposures, which may result in a significant public health problem.
In the article, reported in The New England Journal of Medicine for November 29, Drs. David J. Brenner and Eric J. Hall, from Columbia University Medical Center in New York, discuss the radiation doses in CT scans, the biologic effect of low doses of ionizing radiation, and the risks of CT use.
The authors raise the possibility that the carcinogenic risks from CT imaging may have been underestimated or overlooked in the past. This is concerning because many of the scans performed in the US are probably not medically necessary, they add.
According to the article, more than 62 million CT scans are now performed annually in the US. By comparison, roughly 3 million scans were performed in 1980. The authors credit this tremendous growth in use on technological innovations that have made CT scanning more user-friendly for both patients and practitioners.
This increase in CT usage is largely responsible for the near doubling of the average personal radiation exposure that occurred during the same period.
The authors note that the low doses of radiation received from CT scanning were initially thought to be harmless. However, evidence from atomic bomb survivors exposed to a similar level of radiation suggests that in the long-term, it does translate into an elevated cancer risk.
At the individual level, this risk may seem small, but at the population level it could represent a real public health problem, given how often CT scans are performed. The authors estimate that in the future up to 2 per cent of all malignancies in the US could be due to radiation from CT scans.
CT scans ordered by physicians to protect against litigation, a form of "defensive" medicine, and scans generated repeatedly when medical departments fail to communicate represent some of the potentially unnecessary scans.
Drs. Brenner and Hall offer three suggestions for lowering the radiation risks of CT scans:
ACR responds to NEJM radiation risk study
The American College of Radiology (ACR) responded to the study's publication by saying it was concerned that certain conclusions and comparisons made in the study, 'Computed Tomography -- An Increasing Source of Radiation Exposure,' published in the Nov. 29 issue of the New England Journal of Medicine, may be inappropriate and cause patients to mistakenly avoid getting life-saving medical imaging care.
The study claims that up to 2 per cent of all cancers in the United States may be caused by radiation received from CT scans. Yet, the study authors admit that there are currently no published studies directly linking CT scans (even multiple CT scans) to cancer, the ACR points out.
The study also equates radiation exposure and effects experienced by many atomic bomb survivors in Japan to present day patients who receive computed tomography (CT) scans. Most CT exams are performed in a controlled setting. They result in limited radiation exposure to a small portion of the body. Atomic bomb survivors experienced instantaneous radiation exposure to the whole body. Also, CT exams expose patients solely to x-rays. Atomic blast survivors were exposed to x-rays, particulate radiations, neutrons, and other radioactive materials. The known biological effects are very different for these two scenarios.
"Patients need accurate information on which to base their health care decisions. They may be terribly confused and unduly distressed by some of the statements in this study," said Arl Van Moore Jr., M.D., FACR, chair of the ACR Board of Chancellors.
There is little doubt in the medical community that CT scans help save lives. Advancing technology has increasingly allowed imaging exams to replace more invasive techniques, but has also resulted in increased radiation exposure for Americans.
The College urges patients and providers to visit the 'Radiology Safety' section of the ACR Web site as well as the 'Radiation Safety' section of www.radiologyinfo.org, the patient information site co-managed by the ACR and the Radiological Society of North America (RSNA), for more information regarding radiation exposure from medical imaging exams.
Patients should also keep a record of their X-ray history and before undergoing a scan, should ask their physician:
"The College has long held that no medical test, particularly those utilizing ionizing radiation, should be performed unless the medical benefits clearly outweigh any risk associated with the exam. For example, the ACR has long opposed full body CT scans for asymptomatic patients, one of the exams that the NEJM article authors put forth as a driver of future CT growth," said ACR Chair Moore.
The ACR said it also supports the ‘as low as reasonably achievable’ (ALARA) concept which urges providers to use the minimum level of radiation needed in such exams to achieve the necessary results.
In its response the ACR stressed it has led the effort to eliminate unnecessary radiation dose in imaging for decades. Historic ACR actions to monitor and reduce radiation dose include:
ACR activities to lower radiation dose were recently summarized in the ACR Whitepaper on Radiation Dose in Medicine published in May 2007. In the paper, the ACR Blue Ribbon Panel on Radiation Dose also outlined 33 specific action items to help reduce radiation dose. Below are items already in motion:
N Engl J Med 2007;357:2277-2284.
In the article, reported in The New England Journal of Medicine for November 29, Drs. David J. Brenner and Eric J. Hall, from Columbia University Medical Center in New York, discuss the radiation doses in CT scans, the biologic effect of low doses of ionizing radiation, and the risks of CT use.
The authors raise the possibility that the carcinogenic risks from CT imaging may have been underestimated or overlooked in the past. This is concerning because many of the scans performed in the US are probably not medically necessary, they add.
According to the article, more than 62 million CT scans are now performed annually in the US. By comparison, roughly 3 million scans were performed in 1980. The authors credit this tremendous growth in use on technological innovations that have made CT scanning more user-friendly for both patients and practitioners.
This increase in CT usage is largely responsible for the near doubling of the average personal radiation exposure that occurred during the same period.
The authors note that the low doses of radiation received from CT scanning were initially thought to be harmless. However, evidence from atomic bomb survivors exposed to a similar level of radiation suggests that in the long-term, it does translate into an elevated cancer risk.
At the individual level, this risk may seem small, but at the population level it could represent a real public health problem, given how often CT scans are performed. The authors estimate that in the future up to 2 per cent of all malignancies in the US could be due to radiation from CT scans.
CT scans ordered by physicians to protect against litigation, a form of "defensive" medicine, and scans generated repeatedly when medical departments fail to communicate represent some of the potentially unnecessary scans.
Drs. Brenner and Hall offer three suggestions for lowering the radiation risks of CT scans:
- Reduce the CT-related radiation dose at the patient level.
- Replace CT evaluation with assessment by non-radiation imaging modalities, such as MRI and ultrasound, when feasible.
- Reduce the total number of CT scans performed.
ACR responds to NEJM radiation risk study
The American College of Radiology (ACR) responded to the study's publication by saying it was concerned that certain conclusions and comparisons made in the study, 'Computed Tomography -- An Increasing Source of Radiation Exposure,' published in the Nov. 29 issue of the New England Journal of Medicine, may be inappropriate and cause patients to mistakenly avoid getting life-saving medical imaging care.
The study claims that up to 2 per cent of all cancers in the United States may be caused by radiation received from CT scans. Yet, the study authors admit that there are currently no published studies directly linking CT scans (even multiple CT scans) to cancer, the ACR points out.
The study also equates radiation exposure and effects experienced by many atomic bomb survivors in Japan to present day patients who receive computed tomography (CT) scans. Most CT exams are performed in a controlled setting. They result in limited radiation exposure to a small portion of the body. Atomic bomb survivors experienced instantaneous radiation exposure to the whole body. Also, CT exams expose patients solely to x-rays. Atomic blast survivors were exposed to x-rays, particulate radiations, neutrons, and other radioactive materials. The known biological effects are very different for these two scenarios.
"Patients need accurate information on which to base their health care decisions. They may be terribly confused and unduly distressed by some of the statements in this study," said Arl Van Moore Jr., M.D., FACR, chair of the ACR Board of Chancellors.
There is little doubt in the medical community that CT scans help save lives. Advancing technology has increasingly allowed imaging exams to replace more invasive techniques, but has also resulted in increased radiation exposure for Americans.
The College urges patients and providers to visit the 'Radiology Safety' section of the ACR Web site as well as the 'Radiation Safety' section of www.radiologyinfo.org, the patient information site co-managed by the ACR and the Radiological Society of North America (RSNA), for more information regarding radiation exposure from medical imaging exams.
Patients should also keep a record of their X-ray history and before undergoing a scan, should ask their physician:
- Why do I need this exam?
- How will having this exam improve my health care?
- Are there alternatives that do not use radiation which are equally as good (e.g.. MRI, ultrasound, etc.)
- Is this facility ACR accredited? (ensures that physician and staff meet education and training standards and that equipment is surveyed regularly by medical physicist to ensure that it is functioning properly).
"The College has long held that no medical test, particularly those utilizing ionizing radiation, should be performed unless the medical benefits clearly outweigh any risk associated with the exam. For example, the ACR has long opposed full body CT scans for asymptomatic patients, one of the exams that the NEJM article authors put forth as a driver of future CT growth," said ACR Chair Moore.
The ACR said it also supports the ‘as low as reasonably achievable’ (ALARA) concept which urges providers to use the minimum level of radiation needed in such exams to achieve the necessary results.
In its response the ACR stressed it has led the effort to eliminate unnecessary radiation dose in imaging for decades. Historic ACR actions to monitor and reduce radiation dose include:
- ACR Appropriateness Criteria (1993) which help radiologists and referring physicians prescribe the most appropriate imaging exam for more than 200 clinical conditions (can help patients avoid unnecessary exposure to scans utilizing radiation when others such as MRI and ultrasound, which do not use radiation, may be better for that particular condition).
- Accreditation of facilities which offer X-ray technologies (including dose assessments):
1. Mammography (1987).
2. Stereotactic Breast Biopsy (1996).
3. CT (2002). - Practice Guidelines and Technical Standards (1990) which layout the acceptable protocols for performing imaging exams (including CT).
ACR activities to lower radiation dose were recently summarized in the ACR Whitepaper on Radiation Dose in Medicine published in May 2007. In the paper, the ACR Blue Ribbon Panel on Radiation Dose also outlined 33 specific action items to help reduce radiation dose. Below are items already in motion:
- Creation of a Dose Registry (2008) including CT dose and the ability to establish bench marks.
- Working with other medical specialties on radiation dose awareness. An example of this is the upcoming 'Consensus Conference on Imaging Safety and Quality for Children in the Emergency Setting' scheduled for Feb. 2008 (cosponsored by the Society for Pediatric Radiology).
N Engl J Med 2007;357:2277-2284.
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