The Risks Associated with Ionizing Radiation in Medical Imaging Practice - Assignment Example

THE RISKS ASSOCIATED WITH IONIZING RADIATION IN MEDICAL IMAGING PRACTICE, AND THE PRECAUTION REQUIRED TO PROTECT AGAINST THEM Introduction In the electromagnetic (EM) spectrum the portion that represents sufficient energy that is enough to pass through matter and actually extricate orbital electrons to form charged ions is termed as ionizing radiation. The ions that are produced as a result of these radiations are capable of bringing about biological changes (Holmes, White and Gaffney, 2011). It is an established fact that the longer wave length, lower frequency waves have less energy and is used for heating and radio. However, the shorter wave length, higher frequency waves such as X-rays and gamma rays are used in the medical imaging techniques and can be biologically fatal (WHO, 2011) (Figure 1). Ionizing radiation can be categorized into two forms. The first one is the radiation in the form of EM wave, such as an x-ray or gamma ray and the second one is the radiation in form of particle, such as an alpha or beta particle, neutron, or proton (DeLima Associates 1993, 1-48). X-rays are radiations that are artificially generated using machine. Gamma rays are EM waves that are released from the nucleus of an unsteady atom. The various forms of ionizing radiation have different effect on the biological systems (Holmes, White and Gaffney, 2011). However, these radiations are of great use in the medical science and have contributed significantly in medical imaging practice. This paper highlights the risks linked with the use of ionizing radiation in medical imaging practice and the necessary precautions that needs to be taken while handling it. Roentgen was the person who discovered X-rays in the year 1895. Since then the use of ionizing radiation in medicine expanded (Holmes, White and Gaffney, 2011). Today, medical science uses both ionizing and non-ionizing radiations in imaging techniques. The ultrasound uses the acoustic pulses for echo-ranging imaging or in case of magnetic resonance imaging (MRI) radio-waves are combined with high-field magnets to produce images. Both ultrasound and MRI make use of non-ionizing radiations. On the other hand the medical imaging techniques that use ionizing radiation consist of those images produced by the use of x-rays or gamma rays. Both x-rays and gamma rays are high energy, short wave-length EM radiation that can penetrate through almost all tissues. Gamma rays are produced as a result of nuclear decays of radioactive tracers that are introduced into the body and x-rays come from x-ray tube in which high speed electrons are bombarded to a small spot on a tungsten anode target. When radiation passes through the body, it is differentially captivated by tissues. For example, calcium is abundantly present in the body and has a higher atomic weight when compared to hydrogen that forms a major component of tissue water. Therefore, the ionizing radiation is taken up differently in different parts of the tissue. In this process if the tissue atoms are ionized, they become chemically reactive and can cause serious cell damage. Therefore, when these medical imaging techniques are inevitably used precautions need to be taken. One of the most common imaging techniques is the X-rays which is highly useful diagnostically by both computed tomography and film (Yale University School of Medicine 2004). All of us at some point of time have an x-ray examination that aids the physicians’ to diagnose disease or damage in the body structure. In another diagnostic procedure the radionuclides are administered to patients and with the help of detectors outside the body, the functioning of the organs can be observed. Hence when the physicians need to get an idea of any problem inside the body, they use one of these imaging procedures. In general the radiation doses used in these imaging processes are low. Figure 2 shows the average radiation dose of common radiographic procedures. If we compare the radiation dose that is used in imaging with that used in the treatment of malignant diseases, the later is much higher. The use of pharmaceuticals labeled with radionuclides for the diagnosis or therapy is called nuclear medicine. When radiation beams are used to treat patients, the procedure is called radiotherapy (iaea.org n.d.). Health Risks Ionizing radiation causes damage to cells and tissues by the production of free radicals that in general are known to set a chain of reactions in the body. If the free radicals are generated at the nucleus of the cell, DNA is damaged. It is also possible that ionizing radiation may damage DNA molecules by ionizing them or breaking DNA molecules. As a result of radiation exposure it is possible that the damage caused to the tissues especially in the form of mutation, can lead to radiation sickness, cancer (Camphausen and Lawrence 2008), and even death. Further, if the dose is high enough the electrons that are released with negative charge and the ions with positive charge are capable of tissue damage and may result in radiation poisoning. When the radiation dose is less it may result in cancer or additional long-term problems. All of us are exposed to very low doses of radiations in normal circumstances particularly from the natural and artificial sources, such as cosmic rays, medical X-rays and nuclear power plants. However, the impact of these radiations is a subject of contemporary debate. According to a report released by the U.S. National Research Council (BEIR VII report) the overall cancer risk associated with background sources of radiation was relatively low. There are also arguments that suggest that low-level doses of ionizing radiation are favorable, as they are responsible for stimulating the immune system and self-repair mechanisms of cells and this theory is called “radiation hormesis”. The radioactive materials that are used in producing the ionization radiation, release α particles from the nuclei of helium, β particles that are rapidly moving electrons or positrons, or gamma rays. It is possible to easily protect us from α and β particles with the help of a sheet of paper or aluminum foil respectively. If α and β particles are released inside the body, the possibility of damage or radiation poisoning is high. However, gamma rays are comparatively less ionizing but require thicker shielding for protection. The damage caused by the gamma rays can be comparable to that caused by X-rays, and comprise radiation burns and also cancer, through mutations. The self defenses mechanism opposes germline mutation by either setting right the changes in the DNA or by cell apoptosis of the damaged cells. The ionizing radiations from the imaging techniques are less damaging when compared to radiations from the environment. For instance, the radioactive iodine does not exhibit any difference and is treated as normal iodine by the body and used by the thyroid. However, the bioaccumulation of radioactive iodine is known to cause thyroid cancer (Robbins and Schneider 2000, 197-203). Hence there are chances that radioactive elements may bioaccumulate in nature and may cause damage to the biological systems. Researchers have found the dose of ionizing radiation that can be fatal to human beings. 300 joules of X-rays or -ray and 15 joules of -particle can turn out to be fatal for the average human. As a result of scientific advancement and the awareness about ionizing radiation, the average dose from medical x-rays has come down and has increased the sensitivity of the photographic film. This has helped in reducing the exposure to harmful radiations of x-rays. Studies suggest that an average American is exposed to 0.170 rem of ionizing radiation annually. Further, a Committee on the Biological Effects of Ionizing Radiation of the National Academy of Sciences of late projected that “a raise dose to 1 rem annually would cause an additional 169 deaths from cancer per million people exposed” (“Ionizing Radiation”, n.d). In general, it is said that the cells in the human body that are vigorously dividing and are active are more sensitive to radiation when compared to cells that are not actively dividing. Hence, the risks of ionizing radiation is more in the cells of bone marrow, the reproductive organs, the epithelium of the intestine, and the skin when compared to cells in the liver, kidney, muscle, brain, and bone(“Ionizing Radiation”, n.d). Protection from Radiation While using medical imaging with ionizing radiation it is essential to follow stringent laws by the national and internations commities. In general, it can be divided into three catogories i.e. protecting the medical staff from occupational exposture, protecting the patients from excess radiation and protecting the general public from radiation. The main factors that control the amount, or dose, of radiation received from a source depends on time, distance and the shelding or the protective cloting used. A combination of these three factors can help in reducing the exposure. For example, if the radioligist or the operator is trained well to reduce the time taken for a procedure, the exposture to harmful radiation can be reduced considerably. Similarly, shielding potency or thickness is typically calculated in units of g/cm2. Medical imaging rooms where x-ray is used, the plaster on the rooms has to contain barium sulphate. Additionally, the x-ray operators in general protect themselves by staying behind leaded glass screen and wearing lead aprons. It is found that most of the materials used can shield one from gamma or x-rays if there is enough thickness (Joseph and Phalen 2006). In general, most of the countries follow the international recommendations for ionizing radiation put fourth by the International Commission on Radiological Protection (ICRP)1. For instance, there needs to be proper justification, limitation and optimization done before the radiations are utilized. Radiations should be used only if its use outweighs the disadvantages from it. Each and every individual need to be protected from radiation risks and the radiation dose should be as low as possible. Risk Estimates When the medical imaging using ionizing radiations is considered, it is essential to estimate the risks associated with the technique. Studies have suggested that the risks of developing cancer are directly related to the amount of radiation dose absorbed and the type of x-ray examination. For instance, in case of a CT examination with a radiation dose of ten millisieverts (mSv), it relates to the increase in the possibility of fatal cancer by 1 in 2000. When this was compared to the occurrence of cancer in natural incidences in US population, it accounts to about 1 chance in 5 cases. That can be summarized as for a person the risk of developing cancer due to radiation is much less than the natural risk of cancer due to various other reasons. However, this risk can increase and can become a serious concern in health care if many are subjected to screening methods using radiation for various unwanted reasons such as monitory benefits. There are still uncertainties regarding the low radiation exposure and cancer development (FDA 2009). Radiation Dose When considering the risks from radiation in medical imaging it is important to make note of the effective doses. For example, the effective doses from investigative CT procedures range from 1 to 10 mSv, depending upon the requirement of the patient. However, if we compare this dose with that of the survivors of atomic bombs in Japan who received minimum doses of 5 to 20 mSv, it can be said that the dose of CT is not much different and there exist a risk of radiation induced cancer mortality (FDA 2009). Depending on the requirement of patients, the radiation dose may vary from partial to whole-body radiation exposures. Additionally, the type of procedure and the type of CT equipment also makes much difference in the radiation dose. In fact, the radiologist may also make certain variations in the radiation dose. There are no standard dosages and hence there are chances of variation. For instance, if the image quality is less the radiation dosage will also be correspondingly less. But if a high quality image is required, then the radiation dose the patient receives will also increase (FDA 2009). There are several safety measures that need to be followed in order to protect the patients and the radiologists from radiation fallouts. For instance, there is enough shielding of the x-ray unit in order to prevent any fallouts, however, it is important that the patients sensitive organs such as gonads, breast, thyroid and eyes that need not be imaged can be shielded by using leaded-impregnated materials. Radiologists and other support staffs need to wear protective leaded aprons (Borrás n.d.). Additionally, there should be stringent restriction for the public from entering the rooms where imaging procedures are carried out. If any patient needs any further assistance from the family members, they should be well protected from radiation by wearing leaded aprons. Any exposure to ionizing radiations during pregnancy should be avoided as it may turn out to be fatal for the fetus. In recent years, there has been a tendency of increased use in the frequency of imaging technologies and thereby there is an increase in the patient doses. According to a report by UNSCEAR, in many countries the radiation exposure is increasing. Additionally, a comparative study of occupational doses also found similar results. The report compared the radiation exposure among “CT technologists, general radiographers, fluoroscopy technologists, radiologists, nurses and radiological technology interns and accomplished that more than eighty percent of CT technologists and radiographers use the protective equipments and do not have considerable exposure” to cause cancer. However the average individual effective dose for interventional procedures is radically superior to usual diagnostic radiology (UNSCEAR 2008). In recent years in the medical field there is an increasing use of the imaging techniques for varied reasons. However, it is important to evaluate the risks and benefits before these techniques are utilized. The different forms of ionizing radiation used in the imaging techniques have different effect on the biological systems. A long and short term exposure of even low dose ionizing radiations can cause changes in the cells and may not be good for health. BIBLIOGRAPHY BEIR VII report. Beir VII: Health Risks from Exposure to Low Levels of Ionizing Radiation. National Academies Press. (18 May, 2011). Borrás Cari n.d. Radiation Protection in Diagnostic Radiology. (20 May 2011). Camphausen K.A, Lawrence R.C. Principles of Radiation Therapy. In Pazdur R, Wagman LD, Camphausen KA, Hoskins WJ (Eds) Cancer Management: A Multidisciplinary Approach. 11 ed. 2008. DeLima Associates. 1993. Case Studies in Environmental Medicine. Agency for Toxic Substances and Disease Registry (ATSDR); 1-48. FDA. 2009. What are the Radiation Risks from CT? (20 May 2011). Holmes Edward B, George L White and David K Gaffney. 2011. Ionizing Radiation Exposure with Medical Imaging. WebMD LLC. (18 May, 2011). iaea.org. n.d. Radiation, People and the Environment. (18 May, 2011). “Ionizing Radiation” n.d. (18 May, 2011). Joseph N. and Phalen J. 2006. Part 3 Cardinal Principles of Radiation Protection. In Online Radiology Continuing Education for Radiology Professionals. (20 May 2011). Robbins J. and Schneider A.B. 2000. Thyroid cancer following exposure to radioactive iodine. Rev Endocr Metab Disord. Apr 1(3):197-203. UNSCEAR. 2008. Sources and effects of ionizing radiation: In UNSCEAR 2008 Report to the General Assembly, with Scientific Annexes. (UNITED NATIONS SCIENTIFIC COMMITTEE ON THE EFFECTS OF ATOMIC RADIATION). New York: United Nations. WHO. 2011. What is Ionizing Radiation? (18 May, 2011). Yale University School of Medicine. 2004. Cardiothoracic Imaging. (18 May, 2011). Read More