Radiation in Medicine A Need for Regulatory Reform (1996) / Chapter Skim
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4 Risks of Ionizing Radiation in Medicine
4 Risks of Ionizing Radiation in Medicine
Pages 111-140
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From page 111... ...
. The next section addresses risk from a different standpoint: the likelihood that unintended exposures will occur as the result of error or accident in the medical use of ionizing radiation.
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From page 112... ...
Scientific consensus groups, including the International Commission on Radiological Protection (ICRP) , the National Council on Radiation Protection and Measurements (NCRP)
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From page 113... ...
This assumption implies a model of radiation injury in which the likelihood of long-term radiation injury increases with dose. As noted earlier, this model is unproved at low levels of radiation exposure.
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From page 114... ...
This concept was based on the premise of a threshold dose, that is, a level of exposure below which ill effects do not occur in exposed persons. The tolerance-dose model of radiation injury, with its implied threshold below which adverse effects of radiation exposure do not occur, was the preferred model of radiation injury until after World War II.
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From page 115... ...
This model is currently accepted by venous advisory groups including those concerned with the BEIR committees, United Nations Scientific Committee on the Effects of Atomic Radiation, NCRP, and ICRP. It is often coupled with a concept that calls for maintenance of radiation exposures at as low as reasonably achievable levels.
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From page 116... ...
RISKS OF IONIZING RADIATION IN MEDICAL TREATMENT Risk of Unintended Exposures In Radiation Medicine The preceding section has addressed the issue of risk from the standpoint of how models quantify the harm, if any, caused to humans who are exposed, under any circumstances, to low-dose radiation. This section addresses risk from a different standpoint: When patients are intentionally exposed to ionizing radiation for medical purposes, do they suffer unintentional exposures as a result of error or accident?
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From page 117... ...
Rates of Misadministration This report refers to errors and unintended events that occur in the course of administering ionizing radiation in medicine as "adverse events." "Misadministrations" and "reportable events" refer to adverse events involving NRCregulated byproduct material and are defined at 10 CFR Part 35 (see Appendix D)
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From page 118... ...
3 (ECRI) data reviewed by the committee showed an occurrence of only 168 total adverse events over a three-year period.
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From page 119... ...
The remaining 415,000 patients were treated with linear accelerator radiation therapy. Thus, the NRC regulatory apparatus is directed at misadministrations involving only about 25 percent of the total radiation therapy patients treated, and only about 0.026 percent of the total of all medication administrations in the United States per year (12 million out of 3.75 billion hospital medication administrations)
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From page 120... ...
First, it advised the NRC to establish common performance indicators to obtain comparable data from all users of byproducts in radiation medicine practice, including both facilities regulated by the NRC and those regulated by Agreement States. The GAO believed that such information would facilitate an evaluation of the effectiveness of the NRC's program and those of the Agreement States.
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From page 121... ...
Misadministrations and Adverse Events In Other Medical Modalities The NRC had asked the Insitute of Medicine to compare the errors in use of byproduct materials and the consequences of those errors with errors occurring in other medical interventions. Adverse events in administration of medications, including chemotherapy, blood transfusions, and surgical interventions, were specifically requested for this comparison.
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From page 122... ...
Chemotherapy ADEs are generally grouped in with other medications in ADE statistics. In the Harvard Medical Practice Study II, ADEs accounted for 19.4 of the total number of disabling adverse events (Leape et al., 1991~.
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From page 123... ...
estimate the mortality rate from the use of anesthesia at 1:5,000 to 1:10,000 patients/ procedures. Blood Transfusions More than 12 million units of red blood cells, 5 million units of platelets, and 2 million units of plasma are administered to patients in the United States each year.
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From page 124... ...
de Planque cited a risk of death from correctly administered radiation therapy from byproduct materials at 1 percent, whereas the additional risk from misadministration of byproduct materials is only 0.0006 percent. She concluded that "even if all misadministrations were successfully eliminated so that, as an incoming cancer patient about to undergo radiation therapy, I could be positively assured that my therapy would be properly administered-my risk of death due to the procedure itself would remain essentially unchanged, or about 1%" (de Planque, 1994~.6 s Dr.
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From page 125... ...
Despite the unavoidably tenuous nature of the comparisons, the information raised the question of whether adverse events in radiation medicine are sufficiently widespread or serious to warrant the current burdens of regulation now directed at the field. Inappropriate and Unnecessary Care In addition to the problem of adverse events and human error, issues of medical services provided when they are not needed (or may even be contraindicated)
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From page 126... ...
training requirements are disproportionate to actual radiation injury risks; and (2) therapeutic training is underprescribed while diagnostic training is overprescribed.
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From page 127... ...
in this chapter, the first of these questions is addressed in the present section on risk of unintended exposures in radiation medicine. In this section the committee discusses its finding that approximate rates of misadministrations in the application of byproduct-related radiation procedures are extremely low.
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From page 128... ...
The current state of empirical knowledge makes it difficult or impossible, as pointed out in the discussion of adverse events, to verify a causal connection between an unintended exposure during radiation treatment and a malignancy that occurs 20 years later. The same lack of empirical knowledge causes the conservative assumption to be made-and applied in the linear, no-threshold model that any exposure to ionizing radiation may increase the risk of harmful health effects, no matter how small the exposure.
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From page 129... ...
The higher a hazard rates in these two factors, the higher is its perceived risk. Within this framework, people perceive the risks of nuclear power and those associated with x-rays quite differently (Fischoff et al., 1978~.
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From page 130... ...
Inasmuch as it is reasonable to presume that the common adjective "nuclear," in both nuclear power and nuclear medicine, or the word "radiation" itself, may trigger public concern with respect to risk, this section explores the public perception of radiation and the risks it may pose to health and well-being of patients, health care personnel, and the public. Evidently, people perceive that different sources of radiation exposure pose different levels of possible harm (Kunreuther et al., 1988; Slovic et al., l991b)
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From page 131... ...
Each item was rated on a scale of perceived risk ranging from 1 (very low risk) to 7 (very high risk)
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From page 132... ...
, the public, influenced by radon's natural origin, its occurrence in a familiar setting, and the absence of someone to blame, sees radon as extremely low risk. Similarly, experts rate nuclear power as a lower risk than medical xrays, whereas lay persons think just the opposite (see Table 4.1~.
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From page 133... ...
This was amply demonstrated in a landmark project in medicine (McNeil et al., 1982~. In it, the investigators demonstrated that when individuals are offered the options of surgery or radiation therapy as treatment for lung cancer, the percentage of patients choosing a specific therapy dropped dramatically when success rates were stated in terms of dying rather than surviving.
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From page 134... ...
The subsequent newspaper coverage focused in far greater detail on the study showing increased risk than on the other article (Koren and Klein, 1991~. Implications for Radiation Medicine The past 20 years of research into the perception of risk have seen little attention paid to medical uses of radiation, in contrast to multiple studies evaluating the perception of risks associated with nuclear power and waste.
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From page 135... ...
RISKS OF IONIZING RADIATIONIN MEDICINE Local board authority to close plant Evacuation plan exists On-site government inspector Rewarded for finding problems Responsive to any sign of problems Effective emergency action taken Local advisory board established Public encouraged to tour plant Mandatory drug testing No problems for five years Hold regular public hearings Employees carefully trained Conduct emergency training Community has access to records Serious accident is controlled Nearby health is good Monitor radioactive emissions Employees informed of problems Neighbors notified of problems No evidence of withholding information Contribute to local charities Employees closely supervised Try to meet with public Managers live nearby Operates according to regulations No problems in past year I Record keeping is good I ~ ~ ~ ~ ~ - 1 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ - ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ J ~ ~ ~ ~ ~ ~ 1 Trust-lncreasing Events Trust-Decreasing Events Don't contribute to local charities No public hearings Little communication with community Emergency response plans not rehearsed Officials live far away Poor record keeping Accident occurs in another state Accused of releasing radiation Denied access to records Employees not informed of problems Delayed inspections Public tours not permitted Health nearby worse than average Official lied to government Serious accident is controlled No adequate emergency response plan Plant covered-up problem Employees drunk on job Records were falsified 60 40 20 0 20 40 60 Percentage of People Rating Impact as "Very Powerful" 135 FIGURE 4.2 Differential impact of trust-increasing and trust-decreasing events. NOTE: Only percentages of Category 7 ratings (very powerful impact)
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From page 136... ...
Although comparisons between misadministrations involving NRCregulated materials and adverse events in other medical modalities are imperfect, the committee felt that such a broad contextual view helped it in its assessment of the risks arising from use of byproduct materials. Finally, recognizing that regulation is often as much a response to public pressure as it is to scientific opinion, the committee has included a look into what is known about the public's perception of ionizing radiation.
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From page 137... ...
The Nature of Adverse Events in Hospitalized Patients: Results from the Harvard Medical Practice Study II. New England Journal of Medicine 324:377-384, 1991.
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From page 138... ...
Slovic, P., Layman, M., Kraus, N., Flynn, J., Chalmers, J., and Gesell, G Perceived Risk, Stigma, and Potential Economic Impacts of a High-T evel Nuclear Waste Repository in Nevada.
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From page 139... ...
UNSCEAR. Report of the United Nations Scientific Committee on the Effects of Atomic Radiation.
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