Objectives
To have a global picture of the recurrent use of CT imaging to a level where cumulative effective dose (CED) to individual patients may be exceeding 100 mSv at which organ doses typically ...are in a range at which radiation effects are of concern
Methods
The IAEA convened a meeting in 2019 with participants from 26 countries, representatives of various organizations, and experts in radiology, medical physics, radiation biology, and epidemiology. Participants were asked to collect data prior to the meeting on cumulative radiation doses to assess the magnitude of patients above a defined level of CED.
Results
It was observed that the number of patients with CED ≥ 100 mSv is much larger than previously known or anticipated. Studies were presented in the meeting with data from about 3.2 million patients who underwent imaging procedures over periods of between 1 and 5 years in different hospitals. It is probable that an additional 0.9 million patients reach the CED ≥ 100 mSv every year globally.
Conclusions
There is a need for urgent actions by all stakeholders to address the issue of high cumulative radiation doses to patients. The actions include development of appropriateness criteria/referral guidelines by professional societies for patients who require recurrent imaging studies, development of CT machines with lower radiation dose than today by manufacturers, and development of policies by risk management organizations to enhance patient radiation safety. Alert values for cumulative radiation exposures of patients should be set up and introduced in dose monitoring systems.
Key Points
• Recurrent radiological imaging procedures leading to high radiation dose to patients are more common than ever before.
• Tracking of radiation exposure of individual patients provides useful information on cumulative radiation dose.
• There is a need for urgent actions by all stakeholders to address the issue of high cumulative radiation doses to patients.
Objectives
To assess percent of patients undergoing multiple CT exams that leads to cumulative effective dose (CED) of ≥ 100 mSv and determine their age distribution.
Methods
Data was retrieved ...retrospectively from established radiation dose monitoring systems by setting the threshold value of 100 mSv at four institutions covering 324 hospitals. The number of patients with CED ≥ 100 mSv only from recurrent CT exams during a feasible time period between 1 and 5 years was identified. Age and gender distribution of these patients were assessed to identify the magnitude of patients in the relatively lower age group of ≤ 50 years.
Results
Of the 2.5 million (2,504,585) patients who underwent 4.8 million (4,819,661) CT exams during the period of between 1 and 5 years, a total of 33,407 (1.33%) patients received a CED of ≥ 100 mSv with an overall median CED of 130.3 mSv and maximum of 1185 mSv. Although the vast majority (72–86%) of patients are > 50 years of age, nearly 20% (13.4 to 28%) are ≤ 50 years. The minimum time to accrue 100 mSv was a single day at all four institutions, an unreported finding to date.
Conclusions
We are in an unprecedented era, where patients undergoing multiple CT exams and receiving CED ≥ 100 mSv are not uncommon. While underscoring the need for imaging appropriateness, the consideration of the number and percent of patients with high exposures and related clinical necessities creates an urgent need for the industry to develop CT scanners and protocols with sub-mSv radiation dose, a goal that has been lingering.
Key Points
•
We are in an era where patients undergoing multiple CT exams during a short span of 1 to 5 years are not uncommon and a sizable fraction among them are below 50 years of age.
•
This leads to cumulative radiation dose to individual patients at which radiation effects are of real concern.
•
There is an urgent need for the industry to develop CT scanners with sub-mSv radiation dose, a goal that has been lingering.
To estimate ocular radiation doses and prevalence of lens opacities in a group of interventional catheterization professionals and offer practical recommendations based on these findings to avoid ...future lens damage.
Subjects included 58 physicians and 69 nurses and technicians attending an interventional cardiology congress and appropriate unexposed age-matched controls. Lens dose estimates were derived from combining experimental measurements in catheterization laboratories with questionnaire responses regarding workload, types of procedures, and use of eye protection. Lens opacities were observed by dilated slit lamp examination using indirect illumination and retroillumination. The frequency and severity of posterior lens changes were compared between the exposed and unexposed groups. The severity of posterior lens changes was correlated with cumulative eye dose.
Posterior subcapsular lens changes characteristic of ionizing radiation exposure were found in 50% of interventional cardiologists and 41% of nurses and technicians compared with findings of similar lens changes in<10% of controls. Estimated cumulative eye doses ranged from 0.1-18.9 Sv. Most lens injuries result after several years of work without eye protection.
A high prevalence of lens changes likely induced by radiation exposure in the study population suggests an urgent need for improved radiation safety and training, use of eye protection during catheterization procedures, and improved occupational dosimetry.
To estimate cumulative organ doses and age- and gender-stratified cancer mortality risks in patients undergoing recurrent computed tomography (CT) exams.
Cohorts of patients who received cumulative ...effective dose ≥ 100 mSv were stratified into age and gender groups. Organ doses of 27 organs using Monte Carlo methods were available, and the relative risk model from the Biological Effects of Ionizing Radiation VII (BEIR VII) was used to estimate lifetime attributable cancer mortality risks (LACMR).
Out of the 8956 patients, 6.7% were 16–44 years of age, with median organ doses higher than 200 mGy for stomach and liver, whereas organ doses for nine organs, which included lungs, breasts, colon, red bone marrow, urinary bladder, esophagus, testicles, ovaries, and skin were between 100 and 200 mGy. Thyroid and salivary glands had smaller doses in the range of 45–69 mGy, but the mean dose for each organ was over 100 mGy. The age- and gender-specific median LACMR for the 16–44-years cohort was 0.6 to 0.7 deaths per 100 individuals for males, and 0.8 for females. The mortality estimated figures were highest for patients 16–54 years with slightly lower values for older age groups. Except for the highest age bracket of 75–84 years, the LACMR values for 55–74 years are not lower by orders of magnitude, and thus one cannot ignore risks in this age group.
Organ doses over 100 mGy for most organs and for some organs ≥ 200 mGy with unignorable associated lifetime attributable cancer mortality rates were found.
An updated extension of effective dose was recently introduced, namely relative effective dose (
), incorporating age and sex factors. In this study we extended
application to a population of about ...9000 patients who underwent multiple CT imaging exams, and we compared it with other commonly used radiation protection metrics in terms of their correlation with radiation risk. Using Monte Carlo methods,
, dose-length-product based effective dose (
), organ-dose based effective dose (
), and organ-dose based risk index (
) were calculated for each patient. Each metric's dependency to
was assessed in terms of its sensitivity and specificity.
showed the best sensitivity, specificity, and agreement with
(R
= 0.97); while
yielded the lowest specificity and, along with
, the lowest sensitivity. Compared to other metrics,
provided a closer representation of patient and group risk also incorporating age and sex factors within the established framework of effective dose.
•Estimates were made of number of patients likely receiving cumulative effective dose ≥100 mSv in 5-years from CT exams.•It results in about 2.5 million patients in 35 OECD countries.•Countries were ...classified into Low: 0 to <1, Medium: 1 to <2 and High: ≥2 patients with CED ≥ 100 mSv/1000 population.•There are 2 countries in Low, 24 in medium and 9 in high number group.•Stake holders in patient radiation safety should attend to the issue of high doses to such large number of patients.
To estimate the number of patients in OECD (Organization for Economic Co-operation and Development) countries who receive a cumulative effective dose (CED) ≥ 100 mSv from recurrent computed tomography (CT) exams.
Taking into account recently published data on the number of CTs per patient and the fraction of patients with CED ≥ 100 mSv as well as country-specific data for the number of CT exams/1,000 population from OECD publication, this paper makes estimations for 35 OECD countries.
The estimated total number of patients with CED ≥ 100 mSv for all 35 OECD countries combined in a 5-year period is around 2.5 million (2,493,685) in a population of 1.2 billion (1,176,641,900), i.e., 0.21% of the population. Expressed per 1,000 population, the range is from 0.51 for Finland to 2.94 for the US, a nearly six-fold difference. Countries with more than 2 patients with CED ≥ 100 mSv in a 5-yr period per 1,000 population are: Belgium, France, Iceland, Japan, Korea, Luxembourg, Portugal, Turkey, and US.
The first estimates of the number of patients likely receiving CED ≥ 100 mSv through recurrent CT exams in 35 OECD countries indicate that 2.5 million patients reach this level in a 5-year period. There is an urgent need for various stakeholders including medical physicists, referring physicians, health policy makers, manufacturers of CT equipment and epidemiologists to attend to the issue in the interest of patient radiation safety.
Risk-free society is utopian. We come across risks in everyday life, and we use probabilities to get a feel of how risky a situation is. Risk probability numbers of around 1% are comforting, but an ...intercomparison of numbers among various low risks in popular situations can be enlightening. In this article, we compare risks of complications or death in several surgeries and risks in commercial air travel with risks for patients getting cumulative effective dose (CED) of 100 mSv or more, as the latter is a hot and controversial topic currently. The analysis shows that many common surgeries are a few tens or hundreds of times less risky than the risk from a 100 mSv dose, even though the former often frightens us more. Despite there being a much higher chance of developing cancer from radiation than being involved in a commercial plane accident, there is much less emphasis on patient radiation safety than aviation safety. Further, a look at the system of control on prescription drugs indicates that there is much to learn for policy planning. This analysis may help the International Commission on Radiological Protection (ICRP) in their review of recommendations.
The idea of a benefit-risk analysis has been used for decades, but no one has probably bothered to see if there is a ratio or even questioned the concept because it does give an intuitive sense. ...There are situations where the tendency to lose the balance between the risk and benefit has been observed to move either towards benefit alone or risk alone. This may happen in medicine for benefit alone and in the nuclear industry for risk alone when public perceptions are involved. For example, in medicine, when the risk is uncertain and/or may happen in the long term as against the benefit, which may be immediate, the tendency to ignore risk has been observed. On the other hand, accidents in the nuclear industry shadow the benefits of nuclear power, resulting in authorities abandoning nuclear power in some countries. Similarly, tissue reactions to patients in fluoroscopic guided interventions have been highlighted despite the fact that the stochastic risks in the same procedure may be tens of times higher. Attention has been drawn to the analogy of risks in pharmaceuticals as against radiation and better-developed system for drugs for us to learn from. This article describes situations of losing balance and provides motivation for the International Commission on Radiological Protection to develop solutions for situations that entail immediate benefits with long-term radiation risk, commonly encountered in medical exposure.
