The current practice for controlling ionizing radiation exposures is ALARA – (As Low As Reasonably Achievable). This practice is based on acceptance of the 1950s vintage assertion that all exposure to radiation, down to a single low energy gamma ray, carries a greater than zero probability of causing a genetic mutation that might result in either a hereditary defect or cancer.
Some medical imaging professionals who use diagnostic tools employing radiation or radioactive materials believe that they should acknowledge and accept that patients have a legitimate reason to be concerned about radiation. By assuring the patient that they do everything they can to avoid exposures, they believe patients are reassured. ALARA means that their care provider is taking the smallest risk possible while still obtaining information needed to help them avoid even greater risks.
Other imaging professionals accept the evidence supporting their understanding that doses associated with proper medical imaging procedures are far below the doses that might cause harm. They believe that the policy of emphasizing ALARA principles contributes to patient concerns and may even cause some patients to avoid needed procedures.
In January, the journal Medical Physics published a Point/Counterpoint debate on this controversy with the following proposition.
Advocating for use of the ALARA principle in the context of medical imaging fails to recognize that the risk is hypothetical and so serves to reinforce patients’ fears of radiation.
Colin G. Orton Ph.D. Professor Emeritus, Wayne State University, provided the proposal and the discussion introduction. Jeffry A. Siegel, Ph.D. argued for the proposition. Cynthia H. McCollough, Ph.D. argued against the proposition. Both debaters provided brief opening statements and a single round of rebuttals responding to the other’s opening statement.
For the Point/Counterpoint section of Medical Physics, this is the standard stopping point. As a result of existing policy and technical limitations, the Medical Physics editor rejected follow-up contributions related to the published discussion.
According to correspondence made available to Atomic Insights, the journal editor recognizes that some discussions deserve a mechanism for continued engagement, additional points and further interaction with people who might not have been initially invited to provide their views. He even acknowledged that this topic is one that deserves additional exchanges, so he might revisit his rejection decision after making alterations to the current web site software.
While that journal is developing the technical capability to host such discussions, authors of the rejected letters decided that the Atomic Insights comment feature might provide an interim solution.
As a continuation of the excellent debate started by Drs Siegel and McCollough here are additional contributions.
J. J. Bevelacqua
This correspondence addresses the Point/Counterpoint debate by Drs. Jeffry A. Siegel and Cynthia H. McCollough on the use of the ALARA principle in medical imaging.1 The as low as reasonably achievable (ALARA) principle is based upon the linear no-threshold hypothesis (LNTH) that assumes low doses of ionizing radiation are harmful and should be minimized. Using superficial arguments, LNTH/ALARA appears to be a beneficial philosophy, but upon examination of relevant data and experience, it accomplishes a result that is opposite to its intent2-6. In attempting to protect patients from an imagined detriment, the arguments fostered by Dr. McCollough limit the use and application of a vital diagnostic tool.
Dr. McCollough defends ALARA in medical imaging by extrapolating the observed carcinogenic effect of high-dose radiation to the low-dose range used in medical imaging. She notes, “current biological and epidemiological evidence cannot definitively prove that low doses of radiation are safe”. This statement inherently relies on the flawed LNTH and its ALARA derivative. As such, it fails to acknowledge studies observing a reduction of cancers following low-dose rate exposures7 and publications that illustrate significant flaws in the LNTH3,7,8.
As applied to medical imaging, Siegel1 and Siegel and coworkers2 succinctly outline the fallacy of the LNTH and its illegitimate ALARA progeny. These authors note that credible evidence of imaging-related carcinogenic risk at low absorbed dose (2 observe that the LNTH and associated ALARA concepts are fatally flawed and focus only on molecular damage while ignoring protective, organismal biologic responses. The societal harm caused by the LNTH and ALARA has been well documented1-8.
The LNTH also affects acceptance of the use of radiation and radioactive materials and causes the ALARA concept to create harm rather than the presumed benefit. These concepts create a world in which ALARA becomes A Law against Radiation Applications, and radiophobia is continually reinforced.
Radiophobia has inhibited research using low-dose radiation in the detection, prevention, and treatment of cancer and other diseases. Unwarranted fears caused by belief in the LNTH have also effectively inhibited research involving unique applications of radiation and radioactive materials. These applications include the use of low-dose radiation as a treatment protocol.
Patients have refused computed tomography scans and physicians are not prescribing these procedures because the LNTH/ALARA dogma has created concern for the subsequent radiation detriment. This fear could result in missed diagnoses because imaging doses are too low to produce adequate tissue resolution6.
LNTH/ALARA induced radiophobia promotes increased regulations of radiation and radioactive materials. The associated costs to implement compliance further dampen the expansion and use of radiation and radioactive materials. Regulations affect consumer, medical, industrial, healthcare, and research applications and result in significantly increased costs with very limited benefit.
Dr. Siegel provides a rational argument for rejecting the LNTH/ALARA fallacy. I hope that his arguments will cause professionals to challenge poor science and facilitate the use radiation and radioactive materials to benefit society.
- Siegel JA, McCollough CH, Orton CG. Advocating for use of the ALARA principle in the context of medical imaging fails to recognize that the risk is hypothetical and so serves to reinforce patients’ fears of radiation. Medical Physics. 2016:n/a-n/a.
- Siegel JA, Pennington CW, Sacks B. Subjecting Radiologic Imaging to the Linear No-Threshold Hypothesis: A Non Sequitur of Non-Trivial Proportion. J Nucl Med 2017; 58:1–6.
- Doss M, Little MP, Orton CG. Point/Counterpoint: low-dose radiation is beneficial, not harmful. Med Phys. 2014; 41(7): 070601-1 – 070601-4.
- Calabrese EJ. On the origins of the linear no-threshold (LNT) dogma by means of untruths, artful dodges and blind faith. Environmental Research. 2015; 42: 432- 442.
- Bevelacqua JJ. Health Physics: Radiation-Generating Devices, Characteristics, and Hazards. Wiley-VCH, Weinheim (2016).
Cohen MD. Point: Should the ALARA Concept and Image Gently Campaign Be Terminated? Journal of the American College of Radiology 2016; 13(10): 1195-1198.
- Doss M. COUNTERPOINT: should radiation dose from CT scans be a factor in patient care? No. Chest. 2015;147(4)874:877.
- Sacks B, Meyerson G, Siegel JA. Epidemiology without Biology: False Paradigms, Unfounded Assumptions, and Specious Statistics in Radiation Science (with Commentaries by Inge Schmitz-Feuerhake and Christopher Busby and a Reply by the Authors). Biological Theory. 2016;1-33.
Author: Bill Sacks, Ph.D., M.D.
Retired physicist and diagnostic radiologist
To the Editor: This is a comment on the recent Point/Counterpoint debate published online regarding use of the ALARA principle in medical imaging between the two medical physicists, Jeffry A. Siegel and Cynthia H. McCollough (https://doi.org/10.1002/mp.12012).
Dr. McCollough begins her Opening Statement by referring to the ICRP’s principles for medical radiation protection, but offers them as though they were “The fundamental principles” without questioning them. The two ICRP principles are justification and optimization: first, that the use of any ionizing radiation must confer medical benefit, and second, that the lowest dose necessary for diagnostic quality must be used.
The justification is unarguable, though it should refer not just to ionizing radiation, but to any medical procedure whatsoever. The ICRP’s optimization is not a “fundamental” principle, but rather one that is wholly based on the LNT assumption, which is precisely the point under debate.
The ICRP, as Dr. Siegel ably points out, bases its optimization principle on a falsehood, one that never had any justification, and furthermore one that sees mounting evidence against it and in favor of hormesis (benefit). It is simply not true, as McCollough asserts, that “it is just as difficult to prove hormesis as it is to prove carcinogenic risk.” This unjustified assertion can only be based on a profound ignorance, or dismissal, of the experimental and observational literature.
Even McCollough agrees that “credible evidence of imaging-related low-dose (< 100 mGy) carcinogenic risk is nonexistent.” Thus, the justification principle stands in stark contradiction to the optimization principle that is called for by the ICRP and endorsed by McCollough (despite her agreement that there is no evidence of risk). The former is based on a value judgment and is unarguably valid (in general) and the latter is based on a scientific matter of fact and is completely erroneous.
McCollough’s call for “maintaining the trust of our patients,” by showing them that we pay close attention to avoiding over-irradiating them or their children, is therefore precisely the wrong thing to do. Instead of accommodating to the public’s – and most medical practitioners’ – unwarranted fear of low-dose ionizing radiation, the only way to gain, let alone maintain, the trust of our patients is to disabuse them of this decades-old myth that low doses of radiation are harmful, that they contribute to causing cancer.
Accommodation to a myth that only reinforces radiophobia stands in stark contradiction to the need to appeal to scientific experimental and observational evidence and thereby, over time, disabuse the public and medical professionals of their fear.
The effort to inject into the public discussion the reality of the safety of low-dose radiation, and even its probable double benefit (both directly as a stimulus to enhanced immune surveillance and adaptive protection, and indirectly in the form of needed diagnostic information), as Siegel points out, should be our goal.
Optimizing the public’s awareness of scientific reality is the only justifiable approach for those of us who know that there is no evidential basis for radiophobia and growing evidence of the salutary direct effect of low-dose radiation, as well as its unarguable diagnostic benefit.
Fox Chase Cancer Center
I am writing with reference to the Point/Counterpoint debate by Drs. Jeffry Siegel and Cynthia McCollough regarding the use of the ALARA (As Low As Reasonably Achievable) principle in medical imaging.1 The ALARA principle was established in radiation safety based on the linear no-threshold (LNT) model for radiation-induced cancers, in order to minimize the cancer risk from the use of radiation.
The LNT model is justified based on the assumption that DNA damage and mutations are caused by even very low levels of radiation and increased mutations would result in increased cancers, using the somatic mutation model of cancer. Both of these notions underlying the LNT model have turned out to be wrong.2 Whereas there would be an increase in DNA damage shortly after exposure to low-dose radiation (LDR, there would also be enhanced bodily defenses such as increased production of antioxidants and DNA repair enzymes, collectively referred to as adaptive protection.3
Because of the boosted defenses, there would be less of the naturally occurring DNA damage in the subsequent period, with the net result being reduced overall DNA damage and mutations following exposure to LDR.2 Also, there is plenty of evidence against the mutation model of cancer.2 Thus, since the two concepts underlying the LNT model are not valid, the model is not justifiable. Hence, the concept of ALARA, which is based on the LNT model, should not be used in medical imaging, considering that medical imaging involves LDR exposures only.
Dr. McCollough defends ALARA in medical imaging by referring to the well-known carcinogenic effect of high-dose radiation and then stating “current biological and epidemiological evidence cannot definitively prove that low doses of radiation are safe”. She then concludes that the precautionary principle must be invoked to deal with the uncertain risks of LDR. Her statement ignores the large number of studies that have shown reduction of cancers following LDR exposures4 and so the precautionary principle, which relates to dealing with uncertain risks, should not be applied to LDR.
Whereas there are many publications that appear to support the LNT model, careful scrutiny has shown that they have major flaws rendering their conclusions not trustworthy.4-6 In addition, the data generally recognized as the most important for estimating the health effects of radiation, the atomic bomb survivor data, are no longer consistent with the LNT model but consistent with the concept that low radiation doses reduce cancers.7
Dr. McCollough refers to the public perception of radiation as being bad and justifies ALARA to assuage the resultant public fears. The public perception of radiation is based on the misinformation that has been provided to them regarding the carcinogenicity of even the smallest amount of radiation based on the LNT model. The public needs to be informed about the observed cancer preventive effect of LDR to allay their concerns regarding the low radiation doses from diagnostic imaging.
Dr. McCollough expresses concerns that before the ALARA and Image Gently programs were initiated, some children were being imaged with higher adult doses. However, these were still low doses and would not have caused any harm to the children since the ultimate effect following such low radiation doses would be reduced DNA damage and mutations, after the effects of the adaptive protection are factored in.
Children have much stronger immune system and much lower cancer risk compared to adults. LDR would boost their immune system, reducing their cancer risk even further, based on the immune suppression model of cancer.2 Thus, the statement commonly made, that children are much more radiosensitive than adults, based on the atomic bomb survivor studies which involved high radiation doses, is not applicable to the low radiation doses involved in medical imaging. There was indeed no need to initiate the Image Gently program, and the program should be discontinued in view of its unjustifiability and the harm it has caused to patients in multiple ways, as described by Dr. Siegel.
Dr. McCollough states that the health effects of low doses of radiation are simply too small to demonstrate, quoting a publication from 19808 which based its conclusion on the LNT model, and extending the statement to hormetic effects. In doing so, she ignores the vast amount of literature that shows considerable reduction of cancers following LDR exposures.4 Considering the invalidity of the arguments of Dr. McCollough, there is neither justification nor need for ALARA in medical imaging.
- Siegel JA, McCollough CH, and Orton CG. Advocating for use of the ALARA principle in the context of medical imaging fails to recognize that the risk is hypothetical and so serves to reinforce patients’ fears of radiation. Medical Physics. 2016; doi:10.1002/mp.12012.
- Doss M. Changing the Paradigm of Cancer Screening, Prevention, and Treatment. Dose Response. 2016;14(4):1559325816680539.
- Feinendegen LE, Pollycove M, and Neumann RD, Hormesis by Low Dose Radiation Effects: Low-Dose Cancer Risk Modeling Must Recognize Up-Regulation of Protection, Therapeutic Nuclear Medicine, R.P. Baum, Editor. 2013, Springer.
- Doss M. COUNTERPOINT: should radiation dose from CT scans be a factor in patient care? No. Chest. 2015;147(4):874-7.
- Doss M, Little MP, and Orton CG. Point/Counterpoint: low-dose radiation is beneficial, not harmful. Med Phys. 2014;41(7):070601.
- Sacks B, Meyerson G, and Siegel JA. Epidemiology Without Biology: False Paradigms, Unfounded Assumptions, and Specious Statistics in Radiation Science (with Commentaries by Inge Schmitz-Feuerhake and Christopher Busby and a Reply by the Authors). Biological Theory. 2016;11(2):69-101.
- Doss M. Linear No-Threshold Model vs. Radiation Hormesis. Dose Response. 2013;11(4):480-497.
- Land CE. Estimating cancer risks from low doses of ionizing radiation. Science. 1980;209(4462):1197-203.
Your comments are welcome.