Radiation is a double edge sword that truly cuts both ways. The radiation administered to patients is intended to help visualize and treat patient’s maladies is the same, albeit at lower doses, as the radiation that causes mutations at the cellular level and can have carcinogenic effects. The same reactions that leveled cities in Japan, allow medical professionals to help save lives. Those who started using radiation science typically died of radiation-induced diseases and complications but they did so while forwarding a field that modern peoples have been fortunate enough to be a part of and benefit from.
One of the most truthful statements that could be stated about the field of radiography is that it is a license to administer a known carcinogen to the general public. The term “x-ray” was dubbed because the rays have wavelengths between that of ultraviolet and gamma rays and when they were newly discovered they had an err of mystery and many years later, there are still many mysteries in the role and workings of these reactions. These photons, moving faster than light, move through the human body produce latent images on film and electronic receptors that save lives and allow for trained specialists to diagnose and treat mankind’s illnesses and injuries.
Purpose
The purpose of the study will be to gather sufficient information on ocular cataract risks to the radiographer to determine whether or not being employed as a radiologic technologist puts technologists at increased risk for developing cataracts more so than the general public. Looking at previously conducted research from a variety of sources and consolidating that information about the risks and at what point cataracts might become more likely to occur. The question about whether or not lifestyle choices outside of being employed as a radiographer have any bearing upon the incidence of cataract formation.
Significance
According to the Bureau of Labor Statistics (2016), there are over two hundred thousand x-ray technologists being employed in the United States alone, information about pathology such as cataracts would affect a very high number of people. Although continuing education and radiation safety courses are offered and implemented, there are often questions remaining about specific risks. In this case, risks about cataract formation in the eyes. This information might not affect radiologic technologist alone, but also the patients who have a high number of x-rays or CT scans throughout his/her lives and has questions regarding the risks to the eye.
Operational Definitions
Operational definitions for the study would be scatter radiation, grays, rems, rads, radiologic technologist and radiographer. Grays are used in radiation studies or dose reports in medical facilities to assign an amount to the radiation dose that is assumed to be absorbed by a patient or imaging staff member. One gray (Gy), is equal to one hundred radiation absorbed dose (rad) (Chandler, 2001). Rem is “roentgen equivalent in man”. Rads and rems are equal amounts and typically used interchangeably. Scatter radiation refers to the x-ray photons that either glance off the patient and table or bounce off these objects and bounce back outward into the surrounding room. Scatter radiation is typically the primary source of radiation that imaging professionals are exposed to. Radiologic technologists are the professionals who scan, x-ray, and work with patients daily and send those images to a Radiologist or ordering physician for a final reading. The terms radiologic technologist (RT) and radiographer are used interchangeably. Radiation damage at the atomic level occurs when an electron or electrons are knocked out of their outer orbit around a cell nucleus.
A cataract is a hardening or opacity over the lens of the eye that typically follows a progressive and subtle onset (IAEA, 2013). Cataracts negatively alter the vision of the impaired person. Over time, vision impairment or routine eye examinations lead to identification of the issue. This loss of vision typically occurs due to the buildup of protein and water in the areas of the lens that influence vision quality (NEI, 2015). There are three common types of cataracts; nuclear which affect the center of the lens of the eye, cataracts of the cortex surrounding the eye are known as cortical and finally the type which is the most commonly associated with radiation damage the “posterior sub-scapular” type of cataract (IAEA, 2013). Posterior sub-scapular cataracts occur in the back of the eye underneath the lens capsule (IAEA, 2013).
Questions
Does being employed as a RT put technologists at increased risk for developing cataracts more so than the general public? Do lifestyle choices outside of being employed as a radiographer have any bearing upon the incidence of cataract formation? Are the current safety protocols sufficient and up to date with what present studies would suggest?
Hypothesis
A reasonable hypothesis is that being employed as a RT puts one at a slightly increased risk of developing cataracts. The null hypothesis would be there is no increased risk of cataracts to radiologic technologists than the public.
Review of Research
Some of the first mass doses of radiation given to the public have been atomic bomb detonations and nuclear disasters. These events, however unfortunate, have given researchers the ability to study radiation effects on a large population of people. Studies from Chernobyl, Hiroshima and Nagasaki survivors have all shown a correlation between the radiation received to those survivors and cataracts (Ainsbury, 2009). However, it must be taken into consideration that the levels of radiation involved in these studies would be much higher than the controlled amount that a typical occupational radiation worker might be exposed to in their working lives. Upon review, it would appear that ionizing radiation, the term for radiation that has the potential to knock electrons from their orbital axis, does cause an increased risk in the incidence of cataract formations of the eye. As with all things in the human body long-term low doses of radiation or one large acute dose seem to correlate with negative outcomes physiologically.
The percentages increase directly proportionate to age. Age is not the only factor that plays into the cycle of cataract formation of the eyes however as the International Atomic Energy Agency cites both ultraviolet radiation and ionizing radiation as risk factors in increased cataract rates (IAEA, 2013). In more moderate lower doses, such as the kind that would be used in medicine and not atomic eruption or nuclear meltdown, a study performed by Hall et al. found that children who had undergone radiation therapy to the head and neck region were 17% more likely to have a posterior subscapsular opacity than a control group who had not. Opacities were 37% in the children who had undergone treatments versus 20% for the control group (Hall, 1999.)
The amount of radiation typically received by the RT depends on several factors. Time, distance, and shielding are the universally known precautions to limit exposures and when the radiologic technologist can position himself or herself at least six feet away from the patient and image receptor being x-rayed the exposure to that technologist is typically none. The lower doses that would be associated with medical imaging are the focus for this study. Merrill’s Atlas of Radiologic Positioning and Procedures radiation exposure triggers a long chain of possible reactions. The initial exposure results in an initial excitation and ionization of cells. This is followed by molecular alteration in which the body responds to by producing enzymes to repair this damage (Bushong, 42). If this process were to repeat on a large enough scale or often enough, this would result in an increased risk in genetic mutation of the cells that manifests in tissue damage, cancers, etc. The risk for this is somewhat small however. A study done by the a committee to study the Biologic Effects of Ionizing Radiation and published by Stewart Bushong in Merrill’s 10th edition, the normal expected mortality from radiation induced illnesses in a population exposed to the working limits of 100 mRads per year would be about 600 deaths from a population of 100,000 people. The baseline malignancy mortality rate in a group this size is approximately 20,560/100,000 males or 16,680/100,000 females so the risk is rather negligible if proper radiation safety precautions are taken (Bushong, 42).
Basic radiation protection protocols state that when organs or tissues are rapidly dividing on a cellular level they are considered more sensitive to radiation or radiosensitive. The eye is one such organ due to the fact that has a lack of blood supply and has to repair over life to repair the lens (Hood, 2017). Other organs of concern are the thyroid, gonads, and breast tissues as cells that are more likely to incur radiation damage due to their quickly dividing nature. This is often why lead shielding is used for these parts of the body for patients and staff when possible who are in the presence of radiation sources. Findings from a 1992 study of the Chernobyl disaster found that children exposed to radiation were almost twice as likely to have ocular opacities or defects than children from another nearby area that had remained unaffected (Day, 1992). Trained Ophthalmologists examined the eyes of 996 exposed children and compared them with 791 other Ukrainian children, finding that 2.8% of exposed children had changes in the lens of the eyes vs only 1% in the control group (Day, 1992). This supported the findings of Otake and Schull and the study conducted on Hiroshima and Nagasaki survivors involving y-rays and an increase in subcapsular opacities (Otake, 1990).
In a study performed by Chodick et al. and published in the American Journal of Epidemiology 35,705 cataract-free radiologic technologists 24-44 years of age were studied over a 20 year period. This study took into account smoking, body mass and other pre-existing independent health variables. After the participants filled out questionnaires at both the beginning and end of the study, the results were calculated and released. A total of 2,382 cataracts were reported. The higher the personal dose received, the higher the risk of a subsequent cataract formation. It was found that smoking was the greatest risk factor in general, but also that high alcohol consumption, diabetes, and obesity also increased the risks of developing cataracts. These have been stated personal health risks and factors in other cataract studies so this finding is slightly predictable. Interestingly moderate alcohol consumption, one to ten drinks/week, decreased the risk overall of developing a cataract (Chodick, 2008). The study did however question previously believed notions about the threshold dose for cataract formation as it found risk increased with no threshold level to achieve, so every dose to the face and neck would increase the percentage of personal risk of cataract formation. The study did find however that in risk assessments the threshold at which cataract formation was likely to occur was much lower than the 1991 ICRP dose of 5 Gy for repeated low dose exposures (ICRP, 1991).
David Fish and et al. were not able to define the risks that ionizing radiation poses to physicians and pain management specialists in fluoroscopy settings in their research review, but also disputed the accepted International Commission on Radiological Protection threshold dose of 500 REM for one single exposure or 800 REM in partial exposures over time (ICRP, 1991). The previously accepted dose threshold set forth by the ICRP for many years of occupational exposure was 15 REM or greater (ICRP, 1991). Fluoroscopy is the practice of taking video x-rays to better follow dynamic moving anatomy and contrast agents (radiopaque substances used to visualize anatomy otherwise unable to be viewed easily.) Due to the fact that general radiography is the type of most importance to this study, most of the radiation general practice RTs would be subjected to is the scatter from fluoroscopy procedures. In their study following interventional and pain management physicians they found that the average physician who is closest to the patient at the time of the exam, performing approximately 40 studies throughout the course of a workweek in a busy practice, would still remain about 10 times lower than under the threshold dose suggested by the ICRP (Fish, 2011). The study also pointed to the need for eye protection such as lead glasses to provide further safety to those working in these settings as lead lined glasses can decrease radiation to the eyes by 70-98% depending upon the angles at play (Cousin, 1987). Although Fish et al. were able to come to a consensus decision about findings, it remains clear they question the ICRP defined risk dose and recommend eye protection to further the safety measures being instituted.
In summary, all the studies whether they were about massive nuclear events and the subsequent fallout or from the fields of medicine and treatment seemed to point to the conclusion that protracted low levels of radiation to the eyes or one acute radiation exposure to the eyes increased the risk of cataract formation. The threshhold at which this risk occurs seems to be a point of contention where previously held beliefs were higher than what newer studies seem to suggest. One thing that is quite clear is that a risk to a working radiographer exists and limiting the dose received by either mechanical means (glasses or lead shields), or distancing onceself further away from the source whenever possible are prudent choices to mitigate the risks involved.
References
- Bureau of Labor and Statistics. (2016). Radiological and MRI technologists. Retrieved from https://www.bls.gov/ooh/healthcare/radiologic-technologists.htm
- Chandler, D. (2011). Explained: Rad, rem, Sieverts, becquerels: A guide to terminology about radiation exposure. Retrieved from http://news.mit.edu/2011/explained-radioactivity-0328.
- International Atomic Energy Agency. (2013) Radiation and cataract: Staff protection. Retrieved from https://rpop.iaea.org/RPOP/RPoP/Content/InformationFor/HealthProfessionals/6_Other ClinicalSpecialities/radiation-cataract/Radiation-and_cataract.htm
- National Eye Institute. (2015). Facts about cataracts. Retrieved from https://nei.nih.gov/health/cataract/cataract_facts
- Christopher T. Hood, M.D. http://www.umkelloggeye.org/conditions-treatments/cataract
2017-10-14-1507981359