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PubMed2005

Radiation biology: concepts for radiation protection.

The opportunity to write a historical review of the field of radiation biology allows for the viewing of the development and maturity of a field of study, thereby being able to provide the appropriate context for the earlier years of research and its findings. The pioneering work of Muller, Sax, and McClintock, and many others, has stood the test of time. The idea that x-rays could damage the genetic material and result in interactions that could lead to gene mutations and a range of chromosomal alterations is now interpretable in terms of induced DNA damage and errors of DNA repair. The expanded idea that such genetic alterations can be induced by DNA damage that is produced by one or two tracks of ionizing radiation remains the mainstay of radiation biology. The impact of the more recent molecular approaches to unraveling the mechanism behind this simple concept has confirmed this fundamental observation. The remarkable advances have allowed for a fairly complete understanding of the specific types of DNA damage induced by ionizing radiations and the pivotal role played by the errors of repair of double-strand breaks. Given our considerably enhanced knowledge of the details of the DNA repair processes involved, misrepair is a very unlikely event. The role of potential confounders of the concept of dose-response (e.g., bystander effects, genomic instability, and adaptive responses) is taking on a growing importance to the field. The evolving need is to begin to consider mechanistically-based dose-response models for cancer risk such that any potential impact of confounders on the response at low, environmental doses can be assessed. Thus, radiation biology research has always had a focus on how best to protect human health from radiation exposures and will continue to do so.

Animals↗
PubMed1995

[Radiation protection in medicine].

Medical uses of radiation became by far the greatest man-made source of doses to the population at large. As technology and health care improved there has been an increase in the usage of radiation, measured by the frequency of procedures per caput and by the levels of individual and collective dose. From the early 1920's there has been the gradually developing pressure to eliminate unnecessary exposures and to reduce individual doses. Justification of practices and optimization of protection became the leading principles for keeping individual doses and the number of patients exposed As Low As Reasonably Achievable. However, less attention has been given to optimization in medical applications than in most other radiological fields. The range of doses associated with the same procedure is often extremely large, which implies that there is considerable scope for dose reduction. The first important factor is to increase awareness of the relative ease with which doses can be reduced. This requires familiarity with the levels of dose connected with the various procedures and with techniques of quality control. A new and potentially very strong tool is provided by dose constraints, which should be selected by appropriate professional bodies and which should be used in practice as a quantitative guide to good practice. The key elements of optimization of protection, based on the ICRP recommendations were discussed.

Humans↗
PubMed1978

Biological effects and radiation protection in the dental office.

In conclusion, it is important to point out that dentistry's contribution to the United States population's radiation exposure is small. Significant improvements have been made, but since dentistry is only one of the contributors to the population's total exposure to radiation, it is important that we make every effort to keep our contribution as low as is practical. Unnecessary exposure should be reduced whenever possible but this should not be used to deter the practitioner from obtaining radiographs when they are clinically indicated. It is very likely that the risk to the United States population resulting from failure to obtain adequate diagnostic information when radiographs are indicated is considerably greater than any risk resulting from their use.

Age Factors↗
PubMed1986

The development of biomedical approaches and concepts in radiofrequency radiation protection.

The approaches and concepts used in the development of radiofrequency radiation (RFR) protection guidelines evolved over the past quarter of a century. The values of exposure limits (EL) proposed by various groups are converging. Early guides specified ELs in incident power density. Recent ELs are based on considerations of the relationship between bioeffects and the magnitude of the whole body average specific absorption rate (WBA-SAR) and current densities induced in the body. Both these quantities may be considered as dosimetric ones. Thresholds for untoward health effects expressed in terms of these quantities were suggested, and may be considered as basic ELs. It is possible to derive a frequency-dependent relationship between incident RFR fields and WBA-SAR and/or induced current densities in the body. ELs specified for the purpose of determining compliance in terms of electric and magnetic field strengths or equivalent plane-wave power density existing at a point where a person could be present, but measured in the absence of the exposed subject, may be considered as derived working limits. The rationales offered for the recommended ELs indicate that the principal consideration in establishing limits for frequencies of 10 MHz and higher is the prevention of thermal injury, thermal being defined as relatable to heating, i.e. an increase in temperature. At lower frequencies, below 100 kHz or 30 kHz, direct effects on membranes of nerve and muscle cells may be the limiting factor. An additional consideration is the hazard of shock and burns from contact with ungrounded large metal objects that are charged by RFR fields. Recent advances in RFR dosimetry led to concerns that exposure to presently accepted derived ELs may result in large local SARs and induced current densities in certain parts of the body. The present review concludes that further refinements to the basis for RFR should be introduced. Threshold for health hazards should be investigated taking into account both direct and thermal bioeffects of RFR. The dose-thermal effects relationships should be quantified using the concepts of SAR, SA and thermal dosage. Several unresolved questions, such as the biological basis for SAR time-averaging, and the limitation of pulse peak power, are briefly discussed.

Adult↗