Abstract
The uses of radiation revolutionized medicine when experimentation on its potential applications begun. X-Ray technology, discovered by Wilhem Roentgen, is currently used as a common tool for diagnostics; Henri Becquerel, Marie Curie and Pierre Curie dedicated themselves to further investigations in the field, discovering additional radioactive materials (polonium and radium); radiation therapy is a popular treatment for cancer. This paper analyzes the historical background behind these two applications of radiation in the medical field. Moreover, the different types of radiotherapy are described (external-beam radiation therapy, internal radiation therapy). The concept of radiation homeostasis, which is the notion that low-dose radiation may provide bio-positive benefits for overall health is presented. These bio-positive effects include stimulation of the immune system, fertility, lifespan and others. Lastly, the deleterious effects of excessive short and long-term exposure to radiation are explained. Among these risks are cancer, acute radiation syndrome, cutaneous radiation injury, fetus malformation, and others.
Introduction
Radiation refers to the direct transmission of heat or electromagnetic energy through space or another medium (Business Dictionary). There are many types of radiation, including electromagnetic, radio, visible light, x-rays, ultrasound, and others. However, perhaps the most important classification of radiation divides it in: ionizing radiation and non-ionizing radiation.
The uses of radiation are numerous, yet its applications in the health field stand out in particular. From X-Rays to therapy, radiation has taken a place of vital importance in medicine for the diagnosis, monitoring and treatment of several conditions, including cancer.
This paper will focus on the immediate and long term effects of exposure to radiation over health, as well as on the historical events or discoveries that have led to its widespread adoption as an inherent component of medical practice.
Ionizing and Non-Ionizing Radiation
According to the World Health Organization, ionizing radiation is “radiation with enough energy so that during an interaction with an atom, it can remove tightly bound electrons from the orbit of an atom, causing the atom to become charged or ionized”.
Ionizing radiation is known for being generally detrimental to health and potentially lethal, with the exception of its uses for radiation therapy. Its effects are classified in deterministic effects and stochastic effects. The former includes radiation burns, chronic radiation syndrome, and others. The latter includes cancer, birth defects and heritable mutations.
Conversely, non-ionizing radiation is the “radiation in the part of the electromagnetic spectrum where there is insufficient energy to cause ionization. It includes radio waves, microwaves, infrared, ultraviolet and visible radiation.” (World Health Organization). Non-ionizing can also pose a risk to health, as over-exposure may lead to burns and other non-mutagenic effects.
The effects of radiation on health are highly dependent on the intensity or amount of energy of the radiation, its nature, time of exposure and other factors. It is through the manipulation of these variables that beneficial applications of radiation have been discovered in the field of medicine.
History of Radiation in Medicine
X-Ray Technology
The discovery of X-Rays is accredited to Wilhelm Conrad Roentgen, Professor at the Wuerzburg University in Germany. Roentgen was experimenting with cathode-ray tubes in his laboratory in 1895, when he noticed a fluorescent glow of crystals near the tube. After shielding the tube with dark paper, he observed a green fluorescent glow being emitted by the tube that could be seen from a few feet away (NDT Resource Center). Subsequently, he noted the ray could pass through most materials, with the exception of bone and metal, thus casting a shadow of objects of that nature. In 1895, he generated the first X-Ray image, a film of his wife’s hand, shown in Figure 1.
Reed contends that Roentgen’s discovery startled the scientific community, and multiple experiments following his example took place. Not a month had passed since the first X-Ray film had been generated, when radiograph use begun to spread in the United States and Europe for diagnostics. Six months later, the technology was being used to locate bullets in injured soldiers at battlefields. The first diagnostics using X-Ray technology in the United States occurred in February 1896, just two months after Roentgen’s experiments.
Figure 1.- First X-Ray Film
Source: Reed, Amy
Not long after Roentgen’s discovery, French scientist Henri Becquerel discovered a second source of radiation: natural phosphorescence or radioactivity. Becquerel noted that upon exposure to sunlight, certain minerals produce a flow, which he succeeded in capturing on film by using photographic plates (NDT Resource Center).
Following Becquerel’s experiments, polish scientist Marie Curie and her husband, Pierre Curie, embarked on the search for additional radioactive elements, besides Becquerel’s preferred element for experimentation: uranium. In 1898, the couple discovered a new radioactive element which they named polonium; the same year, they added radium to this list, which eventually became the premier source of industrial gamma rays.
In modern times, the medical uses of X-Rays include radiographs, CT scanning (computed tomography), fluoroscopy and radiotherapy, which will be further explained in the following sections of this paper.
Radiotherapy
Roentgen’s discovery sets the foundation for experimentation in the field of radiation for medical use. Cancer Research UK enlightens how a few weeks after Roentgen’s lecture called “Concerning a New Type of Ray” in 1986, medical student Emil Grubbe used radiation as a cancer treatment for the first time, in Chicago.
Grubbe’s initiative surged as he suffered dermatitis in his hands and neck, as a result of exposure to radiation when conducting multiple experiments, as he repeatedly generated X-Ray images of his hands. Noting the relation between his line of work and the injuries, he proceeded to attempt carcinoma treatment utilizing the technology (Chicago Radiological Society). The patient was Rose Lee, a 55-year old victim of recurrent breast cancer.
The idea, however, was not solely his. Markel indicates that Grubbe followed a colleague’s suggestion that “any physical agent capable of doing so much damage to normal cells and tissues might offer possibilities, if used as a therapeutic agent, in the treatment of pathological conditions in which irritating, blistering, or even destructive effects might be desirable”. This scientist was J.E. Gilman. Unfortunately, the patient succumbed to the disease a month after her treatment. Subsequent improvements to radiation therapy have made it a popular treatment to kill cancerous tissue, reduce tumor size, reduce pain, etc. Though Lee did not survive her disease, reports indicate that she benefited greatly from Grubbe’s intervention.
The UC San Diego School of Medicine indicates that Claude Regaud (1870-1940) sustained that effectivity of treatment could increase if it was administered more slowly over a prolonged period, a technique known as fractionation.
Types of Radiation Therapy
Radiation therapy is used as a cancer treatment as exposure to high-energy rays has proven successful in damaging cancer cells’ DNA, impeding them from carrying genetic information to the next generation (National Cancer Institute).
Unfortunately, radiotherapy cannot damage, cancer cells without affecting surrounding healthy cells as well. In consideration, treatment for each patient is carefully selected by determining the exact area to be treated and dose to be administered.
External-beam radiation therapy
Mostly administered through photon beams, commonly using machines called Linear Accelerators, which create high-energy radiation.
According to Scripps, the first treatments of this type took place in the mid-1950s at the University of California, Berkeley, and the Harvard Cyclotron Laboratory. The first proton therapy center opened in 1990 in Southern California. There are currently 15 centers of this nature in the United States.
Currently, the most popular type of external-beam radiotherapy is 3D-Conformal Radiation, which allows to target specific areas with high accuracy. Other types of external-beam radiation therapy are: intensity modulated radiation therapy (IMRT), image-guided radiation therapy (IGRT), tomotherapy, stereotactic radiosurgery, stereotactic body radiation therapy and other charged particle beams.
Internal Radiation Therapy
Also known as brachytherapy, it consists of delivering radiation from sources inside or on the body (National Cancer Institute). There are several techniques used to conduct this type of therapy as a cancer treatment, including interstitial brachytherapy, intracavitary brachytherapy, episcleral brachytherapy. These vary with the location of the radiation source.
Brachytherapy can be classified in low-dose-rate treatment and high-dose rate treatment. In the former, therapy last a couple of radiation; in the later, treatment can be given to several sessions.
The biological effects of radiation depend on its energy. The Radiation Effects Research Foundation classifies emissions in high-linear energy transfer radiation (high ET) and low-LET radiations. Low ET produces ionizations sparsely and are less destructive to biomaterial than high-LET. Figure 2 represents the effects of the same dose of low LET and high LET.
Figure 2.- Low and high LET ionizations
Source: Radiation Effects Research Foundation
Statistics
High-Dose Radiation Treatments
Kauffman and McGee studied the influence of radiation over death statistics due to breast cancer treatment. For high-dose radiation treatments, the absolute reduction of breath cancer deaths in the Early Breast Cancer Trialists was 4%. Recent studies, however, show a reduction of 8%.
Low-Dose Radiation from Diagnostic X-Rays
After determining the cumulative radiation dose per individual taking into account number of examinations, views and attendance, and posteriorly analyzing the relation between this dose and mortality rates due to breast cancer, lower mortality rates are attributed to the positive effects of low-dose radiation by X-rays (Kauffman and McGee).
Other Bio-Positive Effects of Radiation
Radiation Homeostasis
According to Luckey, radiation homeostasis or radiation hormesis is “the stimulation, often considered to be beneficial, from low doses of ionizing radiation”. It is believed that exposure to low doses of ionizing radiation may stimulate repair mechanisms that prevent diseases.
The idea of radiation hormesis is supported by over 3,000 scientific research papers that indicate low dose radiation is beneficial in microbes, plants, invertebrates and vertebrates (Luckey). According to Sakamoto, Myonin, Hosor, Ogawa and Nemoto, low-dose radiation is the most effective treatment against malignant lymphoma, as over half the patients in stage I recover completely solely through the use of radiation therapy.
The stimulatory effect of low-radiation over the immune system is supported by several studies, including one conducted by Hashimoto, Shirato and Hosokawa, who implanted tumors in the leg muscles of rats, and proceeded to treat them in three different groups: full-body radiation, local radiation of the tumor and no radiation. The results show that those subject to full body radiation presented fewer metastases. It is believed that radiation can stimulate faster wound healing, resistance to infections, toxins and tumor injections. This type of radiation activates a series of protective processes in the body. The cell defense strategy depends on a series of factors, which include dose, period of dose application or dose rate, and damage in surrounding cells.
Exposure to low-dose radiation may even increase fertility, thus improving reproduction capabilities. Experiments conducted by Luckey indicate that rodents exposed to low-dose radiation were more fertile and did not present evidence of other mutations, and maintained overall health for 21 generations.
Moreover, in 1949, Kaplan used low-dose radiation as treatment for infertility, obtaining successful results without adverse effects and no evidence of genetic damage in over half of the treated population. He points, additionally, that “the incidence of genetic damage to the children and grandchildren of this group is less that in the normal population”.
Low-dose radiation is also related to increased lifespan. According to Prekeges, survivors of the Hiroshima and Nagasaki tragedy have lived longer than a control group. Genetic effects among the children of atomic bomb survivors has not been found (Vaiserman). Moreover, between the 1940s and 1950s, Lorenz and others exposed laboratory animals to low doses of radiation, with a resulting increased lifespan of 2 to 14% compared to control groups. Cancer recurrence can be reduced from 40 to 10% through exposure to low-dose radiation.
According to Tubiana, who conducted a retrospective study of radiologists’ cancer mortality, found that doses of 20 mGy per fraction have cumulative effects, the lowest cancer-inducing dose is approximately 500 mGy. To analyze in perspective, Luckey contends that the average adult is exposed to approximately 2 mGy/y from natural sources such as air, water and materials. As a result to constant exposure to low-dose radiation, radiologists’ cancer risk is known to be lower than that of other worker population, but recognition has not been given to radiation exposure but rather to the health state of workers.
The French Academy of Science has accepted the concept of radiation hormesis as valid, as documentation regarding groups subject to exposure to ionizing radiation have presented beneficial consequences or no consequences at all. Among these facts are (a) lowered cancer incidence in workers of plutonium plant, (b) lower cancer death rates on workers of nuclear plants than that of control group, among others.
Lastly, radiation has been proven to be essential for life, as animals that have been under-exposed tend to perish, or become weak due to radiation deficiency. Moreover, insufficient radiation is a factor in the premature development of cancerous cells.
Considering the facts presented above, it is evident that the notion that “all radiation is harmful” is unsubstantiated, and preoccupation over the known negative effects of radiation (caused by prolonged exposure or high-energy radiation) has shadowed the evidence of the benefits low-dose radiation provides.
Health Risks Associated to Radiation
There is a social stigma placed upon radiation, as it is widely conceived as negative or harmful under most circumstances. Previous sections of this paper demonstrate how radiation, in certain doses and applications, proves to be beneficial to human health. However, the fear of radiation is not unsubstantiated, as prolonged exposure to high-energy radiation can indeed be detrimental to health.
The Center for Disease Control and Prevention list the potential deleterious consequences of exposure to radiation, which include:
Acute Radiation Syndrome, which can manifest through nausea, vomiting, headaches and diarrhea. Long term serious effects also include loss of appetite, skin damage, seizures, and even coma.
Cutaneous Radiation Injury: Symptoms include itchiness, tingling, erythema, edema, and others.
Cancer: This may seem contradictory, as previous research indicates radiation therapy as a generally successful treatment for cancer patients. However, it is a fact that people who receive high doses of radiation have a higher risk of suffering from cancer.
For pregnant women who surpass the recommended radiation exposure, excessive radiation may generate health defects on the fetus, which can be mild or severe, and include stunted growth, deformities, irregular brain function or cancer. Miscarriage is also a potential side effect of exposure to radiation.
Exposure to radiation may lead to emotional and psychological distress, memory loss, etc.
Conclusion
Radiation has applications in several fields of human development, but its importance in the field of medicine has revolutionized the way certain diseases are diagnosed, monitored and treated. Firstly, the discovery of X-Rays by Wilhelm Conrad Roentgen, and the subsequent technology developed to generate radiographs, permanently changed the field of diagnostics. The first high-scale use of radiographs relates to the location of bullets in injured soldiers in battlefield hospitals.
Other uses of radiation have become widespread, including its therapeutic use against cancer. The origin of this application is derived from the apparent relation between a scientist’s hand burns due to over-exposure, and the potential for cancerous cell destruction of radiation.
Regarding the biopositive effects of radiation on human health, besides its use as cancer treatment, radiation hormesis is an important concept. This notion supports the idea that exposure to low-dose radiation is beneficial to human health. Evidence supports that exposure to low-dose radiation stimulates the immune system, improves fertility and increased lifespan. However, popular misconception regarding the damaging effects of radiation has prevented the exploitation of its benefits.
Conversely, inadequate exposure to any type of radiation poses numerous health risks, which range from burns or dermatitis, seizures, coma, birth defects, to cancer itself. In consideration, humans are advised to avoid high energy radiation unless otherwise indicated and controlled by medical practitioners. Time and intensity of exposure must be carefully determined on a case-by-case basis, considering each patient’s medical history and disease characteristics.
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