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Radiation Safety: A Growing Concern

Aimee J. Phillips, MS, RT(R)(M)(CV)(QM)

   *Educational Services Specialist, Marietta Memorial Hospital, Marietta, Ohio.
   Address correspondence to: Aimee J. Phillips, MS, RT(R)(M)(CV)(QM), Educational Services, Marietta Memorial Hospital, 401 Matthew Street, Marietta, Ohio 45750. E-mail: aphillips@mmhospital.org.

Disclosure Statement: Ms Phillips reports having no significant financial or advisory relationships with corporate organizations related to this activity.

ABSTRACT

One of the basic principles of radiation protection is that radiation dose should always be kept as low as reasonably achievable, or ALARA. Although radiation safety practices are essentially basic, they seem to have become challenging as the number of diagnostic procedures and types of imaging equipment continue to expand. Even though new radiology equipment has drastically improved image quality and speed, it is now much easier to expose patients to excessive amounts of radiation. Therefore, the healthcare team must remain educated in regard to radiation safety so that they can protect their patients and themselves. In addition, the general population is more aware of radiation risks than ever before, and as a result, they demand and deserve accurate information regarding radiation protection. The following article discusses the basics of radiation safety as they relate to different imaging modalities and equipment to provide imaging professionals with the information they need to adequately address their patient's concerns.

Introduction
There are several important principles of radiation protection, the main one being that radiation dose should always be kept as low as reasonably achievable (ALARA). Although these practices are essentially basic, it can be challenging to apply them as the number of diagnostic procedures and types of imaging equipment continue to expand. Even though new radiology equipment has drastically improved image quality and speed, it is now much easier to expose patients to excessive amounts of radiation, making it necessary for healthcare professions to be continually educated about radiation safety to protect their patients and themselves. The general population also is more aware of radiation risks than ever before, and as a result, they demand and deserve accurate information regarding radiation protection. This article will include discussion regarding: radiation types, risks and exposure limits; ALARA principles as applied to radiation workers, co-workers and the public; personnel monitoring and survey equipment; and radiation safety in multiple modalities.

Radiation Basics
Definitions
There are several important definitions with which radiologic technologists should be familiar. These basic definitions are outlined below and provide a foundation for imaging professionals.

Overall, radiation protection may be defined as effective measure employed by radiation workers to safeguard patients, personnel, and the general public from unnecessary exposure to ionizing radiation. Protective measures take into consideration both human and environmental physical determinants, technical elements, and procedural factors. They consist of tools and techniques used to minimize radiation exposure.1

Radioactivity is the process of nuclear decay or disintegration whereby an unstable isotope releases energy in the form of particles and/or electromagnetic radiation. Radiation is classified as ionizing or non-ionizing according to the effects it has on matter. Ionizing radiation is radiation that is capable of producing ions when interacting with matter. It is both natural and man-made. Natural sources include cosmic rays, gamma rays from the Earth, radon decay products in the air, and various radionuclides found naturally in food and drink. Artificial sources include medical X-rays, fallout from the testing of nuclear weapons in the atmosphere, discharges of radioactive waste from the nuclear industry, industrial gamma rays, and miscellaneous items such as consumer products. In a more simplistic form, ionizing radiation includes cosmic rays, X-rays, and radiation from radioactive materials.2

Radiation interactions include direct and indirect interactions. Direct interaction is when ionizing radiation produces damage by knocking electrons off atoms. Indirect interactions occur by ionizing atoms in human cells that can initiate chemical changes which may harm the cell.

Figure 1Alpha, beta, gamma and X-rays are all ionizing radiation. For the nature of this article, the focus will be on man-made ionizing medical radiation (ie, gamma and X-rays).

Finally, medical radiation exposure results from the use of diagnostic X-ray machines and radiopharmaceuticals in medicine. As noted in Figure 1,3 diagnostic medical X-ray and nuclear medicine procedures are the 2 largest sources of artificial radiation and account for 15% of the total average effective dose of the population of the United States.1

Types of Ionizing Radiation: Alpha, Beta, Gamma, and X-Rays
Alpha radiation is radiation that is not able to penetrate the skin and is often referenced as positive radiation.4 Alpha-emitting materials can be harmful to humans if the materials are inhaled, swallowed, or absorbed through open wounds.5 Alpha is considered particulate radiation, which is a specific form of ionizing radiation consisting of atomic or subatomic particles that carry energy in the form of kinetic energy or mass in motion.4 

Beta radiation may travel meters in air and is moderately penetrating and is sometimes noted as negative radiation.4 It can penetrate human skin to the "germinal layer," where new skin cells are produced. If beta-emitting contaminants are allowed to remain on the skin for a prolonged period of time, they may cause skin injury. They also may be harmful if deposited internally.6 Beta is also considered particulate radiation.

Gamma and X-rays are electromagnetic radiation such as visible light, radio waves, and ultraviolet light. These electromagnetic radiations only differ in the amount of energy they have. Gamma rays and X-rays are the most energetic of these electromagnetic radiations. Gamma radiation is able to travel many meters in air and many centimeters in human tissue. Gamma and X-rays are "penetrating radiation." Radioactive materials that emit gamma radiation and X-rays constitute both an external and internal hazard to humans. Dense materials are needed for shielding from gamma radiation. Gamma radiation and X-rays frequently accompany the emission of alpha and beta radiation.7 There is no such thing as a "pure" gamma emitter. Gamma rays are used to form images in nuclear medicine and include technetium-99m. Another gamma emitter, cesium-137, is used for calibration of nuclear instruments. X-rays are used to form images in radiography, fluoroscopy, mammography, and computed tomography (CT).

Gamma and X-rays are considered electromagnetic radiation, and will be the focus of this article. Figure 2 demonstrates the penetrating ability of alpha, beta, gamma, and X-rays.8

Figure 2

Units of Radiation Exposure
There are 2 systems for measuring the intensity of radiation or units of radiation exposure. They are the classical or conventional system (sometimes also known as the traditional system) and the SI system or Systeme International. The classical/conventional system was developed and defined over the past century and is often the most familiar to the radiology community in the United States. It is sometimes referred to as the "Three Rs": the roentgen, rad and rem.

The SI system is derived from the metric system and has been adopted by most organizations and the radiology community for the purpose of having 1 unified system. The SI units are coulomb/kilogram, gray, and sievert. Due to familiarity, the traditional measurement units continue to be used by the radiology community.

Because radiation affects people, we must be able to measure its presence. We also need to relate the amount of radiation received by the body to its physiological effects. Two terms used to relate the amount of radiation received by the body are exposure and dose. When you are exposed to radiation, your body absorbs a dose of radiation. Certain units are used to properly express the measurement. For radiation measurements they are9:

  • Roentgen (R): This is the traditional unit used to measure exposure. It only applies to absorption of gamma rays and X-rays in air. It is named after the German physicist who discovered X-ray, Wilhelm Conrad Roentgen. This unit of radiation dose is normally measured by a physicist. The SI equivalent is the coulomb/kilogram (C/kg).

              1 R = 2.58 x 10-4 C/kg

          If conversion between the 2 units is necessary, the conversion is:

              1 C/kg of air = 3876 R

  • rad (Radiation absorbed dose): This is the traditional unit of absorbed energy or dose. rad is the amount of energy deposited per unit weight of human tissue. This is the quantity most directly related to biological effects. Absorbed does expresses the concentration of radiation energy actually absorbed in tissue. The SI equivalent is the gray (Gy).

              100 rad = 1 Gy

  • rem (radiation equivalent man): The rem is used for specifying biologically equivalent dose and is the traditional measure for biological exposure to radiation after compensating for the type of radiation involved. It is the unit of occupational exposure and biological risk. The SI equivalent is the Sievert (Sv).

              100 rem = 1 Sv

Not all radiation has the same biological effect, even for the same amount of absorbed dose. rem attempts to take into account the variation in biologic harm that is produced by different types of radiation.1 It enables the calculation of effective dose, a dose that takes into account the dose for all types of ionizing radiation to organs or tissues in the human body being irradiated and the overall harm or the weighting factor of those biologic components for developing a radiation-induced cancer.1 Equivalent dose is often expressed in terms of thousandths of a rem, or mrem. To determine equivalent dose (rem), multiply absorbed dose (rad) by a quality factor (Q) that is unique to the type of radiation.

              rem = rad x Q

To summarize, exposure may be described as the amount of ionizing radiation that may strike an object such as the human body when in the vicinity of a radiation source. Absorbed dose is the deposition of energy per unit mass by ionizing radiation in the patient's body tissue. Dose equivalent is a quantity that attempts to summarize all of the aspects of different types of ionizing radiation that may lead to biologic harm.1

Table 1Quality Factor
Quality factor is defined as the factor by which the absorbed dose (rad or gray) must be multiplied to obtain a quantity that expresses, on a common scale for all ionizing radiation, the biological damage (rem or sievert) to the exposed tissue. It is used because some types of radiation, such as alpha particles, are more biologically damaging to live tissue than other types of radiation when the absorbed dose from both is equal. The term, quality factor, has now been replaced by "radiation weighting factor" in the latest system of recommendations for radiation protection.10 Table 1 demonstrates the quality factors for frequently encountered types of radiation.10

Risks
Exposure to ionizing radiation affects various organs and tissues in the body and may result in a finite possibility for radiation-induced disease in persons exposed to the radiation, and in their descendants. Health effects are know to be influenced by radiation characteristics and biological factors and include cancer induction, genetically determined ill health, nonspecific life shortening, developmental abnormalities, and degenerative diseases. Some factors that can affect the probability and significance of potential effects are:

  • Age: Response to radiation differs with age. Children are more sensitive to exposure than most adults.
  • Acute or chronic exposure: Was exposure delivered over a short period of time or spread over an extended period?
  • Internal or external exposure: External means the source of radiation is outside the body and internal means the source of radiation was ingested, inhaled, absorbed, or injected.
  • What part and how much: Was the exposure localized to a specific area?
  • Type of radiation: Forms of radiation differ in their penetrating power and ability to cause damage to biological tissues.

Figure 3The effects from the exposure to ionizing radiation may be classified as either somatic or genetic.11 Teratogenic effects also must be addressed.

Somatic effects are not usually seen in medical workers during the course of their work in the medical environment. In order to see a radiation response in humans within a few days to weeks after exposure, the dose must be quite high. Somatic effects of radiation include skin erythema, cataracts, and radiation-induced malignancies. Figure 3 shows damage to the hand from high-dose X-ray exposure.12

Somatic radiation effects can be acute or delayed. Acute effects include skin reddening, hair loss, and radiation burns. Delayed effects include cataract formation and cancer induction that can occur months or years after radiation exposure. The probability of developing radiation-induced cancer increases with radiation does, but the severity of the malignancy is independent of the radiation does. Table 2 outlines a few radiation effects and the threshold dose required to achieve the effect.12

Table 2Genetic effects do not produce any significantly observable effect in the exposed individual but may appear in descendants of the exposed individual.11 The effects may lie dormant for several generations. It is unlikely that any worker in the medical environment would be exposed to ionizing radiation at a level high enough to cause genetic effects.

Teratogenic effects are those such as cancer or congenital malformation. These effects can be observed in children who where exposed during the fetal and embryonic stages of development.

It is important to set limits for the protection of radiation workers and the general public because of the known biological effects of exposure to ionizing radiation.11 Dose limits need to be established to limit the risks of stochastic effects and to prevent deterministic effects (also known as nonstochastic events).

  • Stochastic Effects: Those for which no threshold dose of radiation exists (the effect my potentially occur following any amount of exposure). They are random in nature, and regardless of the dose, some will experience an effect. As the dose goes up, the chance of experiencing an effect also increases. Examples include cancer and genetic defects.
  • Deterministic Effects (Nonstochastic Effects): A threshold dose is assumed in order to have a deterministic effect. They are biologic somatic effects that can be directly related to the dose received.1 As dose increases, the severity of the effect increases. Although the dose has to be high to demonstrate the effect, once that dose is reached, the probability of and effect is very high. For example, if a certain dose of radiation produces a skin burn, a higher dose of radiation will cause the skin burn to be more severe; however, a dose below the threshold level for skin burn will not demonstrate the effect.1 Such radiation doses are usually much greater than those typically encountered by a patient in diagnostic radiology. Examples include cataract formation, skin reddening (erythema), and sterility.

Figure 4Exposure Limits
Dose limits are in part based on effective dose equivalent and differences in tissue sensitivities. Figure 4 demonstrates tissue and organ sensitivity from most radiosensitive to least radiosensitive.

In diagnostic radiology, the main source of occupational exposure is from scattered radiation from the patient-particularly from fluoroscopically guided procedures. Pregnant personnel have lower limits, which apply only with voluntary declaration of pregnancy.13 Recommended exposure limits are set by the US National Council on Radiation Protection (NRCP) and worldwide by the International Council on Radiation Protection. Annual occupational dose limits are:

  • Whole Body: 5000 mrem/year
  • Lens of Eye: 15 000 mrem/year
  • Extremities, Skin, and Individual Tissue: 50 000 mrem/year
  • Minors: 500 mrem/year
  • Embryo/fetus:   500 mrem/9 months
  • General Public: 100 mrem/year

ALARA
Radiation cannot be seen, smelled, or heard. That is why the ALARA concept (As Low as Reasonably Achievable) is at the forefront of our profession. ALARA is the responsibility of all healthcare professionals dealing with radiation, however the burden largely falls on the technologist as a professional caregiver and operator of the radiation-emitting equipment. These individuals are responsible for compliance with radiation safety requirements, and must be familiar with and follow specific instructions for protocols and radiation protection. Radiation exposure must be kept to the lowest achievable level by using protective equipment and following the principles of ALARA. ALARA applies to both internal and external exposure, as well as occupational and public exposure. ALARA is far-reaching and must be applied to ensure that individual dose, collective dose, radioactive waste, and radioactive emissions are all as low as reasonably achievable. The basic principles of ALARA are:

  • Time
  • Distance
  • Shielding

Time
Radiation Dose Received = Dose Rate x Time. Therefore the least amount of time spent around radiation, the lower the dose, whether it be for a patient or healthcare team member. Time around radiation can be reduced through careful planning of X-ray procedures, making sure all equipment is available and in working condition, and by performing "dry runs" of certain procedures without radiation to ensure that everything is in place to reduce time. This type of preparation also can better prepare the imaging team, so they do not feel rushed through procedures. Another way to decrease time is to determine who needs to be present during a procedure. Whenever possible, either remain out of the room or behind protective barriers.

Distance
Increasing the distance between the individual and the source of radiation is an effective method to reduce exposure to radiation.11 As distance from the source of radiation is increased, the radiation level decreases dramatically. Doubling the distance from the radiation source reduces exposure by a factor of 4. Tripling the distance reduces exposure by a factor of 9. Maximizing the distance from the source significantly reduces exposure. Exposure varies inversely with the square of the distance from the source and is calculated using the inverse square law. The inverse square law states that the intensity of radiation at a given distance from a point source is inversely proportional to the square of the distance.
Inverse Square
Maximizing the distance from the source is important for minimizing dose when working with all types of radiation. Along with the other methods to increase distance, the use of remote handling tools, or working at arms length in order to maximize distance from the source, is important. Use forceps, tongs, and trays to increase the distance and even move items being worked on away from radiation if possible. Know the radiation intensity in your work area and move to lower dose areas when possible. These recommendations directly affect workers in radiation therapy and nuclear medicine.

Shielding
Shielding is used either when time or distance are ineffective or as an additional exposure reduction strategy. By placing material between the source of radiation and the user, a certain reduction in exposure will be achieved. The degree of exposure reduction will depend on the physical characteristics of the material (atomic number, density, and thickness).11 The type of shielding that is most appropriate to use depends on the nature of the penetrating power of the radiation. Increasing the amount of shielding will decrease the amount of exposure. For fixed X-ray imaging facilities, lead and concrete shielding are used. Mobile shields, lead-equivalent aprons, and gloves should be used when it is not possible to take advantage of fixed structural barriers. This is common during fluoroscopy and mobile procedures. The greater the lead equivalent in the aprons, the greater the protective ability it has. A protective lead apron attenuates approximately 90% of scatter radiation. It is good to keep in mind that as the lead content in the apron increases, so does the weight of the apron.

Time/Distance/Shielding for Patients
Time, distance, and shielding are just as important for the patient as they are for the imaging professional. From diagnostic imaging to radiation therapy, decreasing the amount of time, increasing distance, and providing shielding for the patient helps to decrease dose. Time can be reduced by the radiographer through decreasing repeat images and decreasing fluoroscopy X-ray beam time. Distance can be addressed by making sure that examinations are being performed at the proper source to image receptor distance (SID). Shielding should be used at all times whenever it will not compromise the image by covering up the anatomy being imaged.

Monitoring Devices
Personnel stand near patients for long times, and angulated geometries with C-arm equipment may result in high personnel doses from backscatter.13 As mentioned before, judicious application of time, distance, and shielding need to be applied to reduce dose. Individuals who are regularly exposed to ionizing radiation should be provided with personnel monitoring devices to provide an estimate of the exposure received.11 Personnel monitoring is recommended whenever a possibility exists that an individual will receive more than 1/10 of the recommended dose limit as a result of his or her occupational activities.11 A personnel monitoring device measures the quantity of exposure received. It does not provide radiation protection.

In order to avoid inaccurate dosimeter/personnel monitoring device readings, never remove the internal elements from the protective plastic dosimeter case. When not in use, dosimeters should be stored away from sources of ionizing radiation and should never be exposed to non-occupational radiation. Badges are designed to measure individual exposure on a monthly or even quarterly basis, depending on the work assignment. If the radiation worker is wearing a lead apron, the badge should be clipped to the outside of the lead apron. It is also crucial to exchange the badge in a timely manner to ensure accurate readings. The 3 most common types of personnel monitoring devices are the film badge, the thermoluminescent dosimeter (TLD) ring badges, and the pocket dosimeter.

Figure 5Film Badge
The film badge (Figure 5) is used to measure whole-body exposure and shallow dose.14 It consists of a film packet and a holder. A special film is used which is coated with 2 different emulsions. The film is packaged in a light-proof, vapor-proof envelope preventing light, moisture, or chemical vapors from affecting the film. One side is coated with a large grain, fast emulsion that is sensitive to low levels of exposure. The other side of the film is coated with a fine grain, slow emulsion that is less sensitive to exposure. If the radiation exposure causes the fast emulsion in the processed film to be darkened to a degree that it cannot be interpreted, the fast emulsion is removed and the dose is computed using the slow emulsion.15 The holder has several filters that help determine the type and energy of radiation. When the atoms in the aluminum oxide sheet inside the badge are exposed to radiation, electrons are trapped in an excited state until irradiated with a specific wavelength of laser light. The released energy of excitation, which is given off as visible light, is measured to determine radiation dose. In order for the radiation type and energy to be determined, the dosimeter must be worn so that the front of the dosimeter faces toward the source of radiation.

Film badges are capable of measuring exposures over the range of approximately 10 mrem (0.1 mSv) to 2000 rem (20 Sv) and are most commonly used to measure the total body exposure of the individual. Readings of less than 10 mrem (0.1 mSv) are generally not detectable and may be reported as minimal.11 Personnel who work in high-dose fluoroscopy settings may wear 2 badges for additional monitoring with 1 being worn at the collar level outside the apron and the other at the waist under the apron. When a single film badge is worn, it is at the collar level outside the apron.

Figure 6Thermoluminescent Dosimeter Ring Badges
The TLD ring is used to measure dose to the hand. Individuals who use millicurie amounts of gamma or high-energy beta emitters wear these. Nuclear medicine technologists or others who handle radionuclides or radiopharmaceuticals must wear a ring monitor so radiation exposure of the fingers and extremities can be estimated.16 Incident radiation excites atoms in the crystals in the TLD. When heated (thermo), the "trapped" excited electrons give up a photon (luminescent). A photomultiplier tube amplifies this photon signal and the output is sent to the dosimeter reader to register the dose. TLD's are commonly used for monitoring exposure to the extremities in the form of a ring badge (Figure 6).14 The TLD ring badge should be worn on the hand most often handling radioactive material. The text side of the badge must face the inside of the palm.

Pocket Dosimeters
Pocket dosimeters are a special type of ionization chamber used for personnel dosimetry (Figure 7).17 When irradiated, the radiation ionizes the air in the chamber, which partially neutralizes a previously positively charged electrode causing the hairline fiber to move on an exposure scale. The amount of Figure 7ionization and movement of the fiber is proportional to the radiation exposure of the chamber. Such devices are usually charged and read out on a special charger-reader device. Pocket dosimeters are occasionally used for personnel monitoring in situations in which the convenience of an immediate readout is desired. They do not provide a permanent record of personnel exposure and are not routinely used.11

Care of Personnel Monitoring Devices
The proper care and handling of personnel monitoring devices is essential to obtaining accurate results. The device must be worn only by the individual to whom it is assigned, must work in the proper location for the prescribed time period, and must be turned in for processing when due. Both film badges and TLD dosimeters may be adversely affected by heat, humidity, mechanical pressure, inadvertent exposure to light, and prolonged delay between exposure and processing.11

Groups of personnel dosimeters are provided with a control that must be stored in an unexposed area at the facility and returned with the group for processing. This control provides an unexposed level against which the personnel dosimeters are evaluated.11

Survey Equipment
The survey meter is the most important resource a radiographer has to determine the presence and intensity of radiation. There are different types of survey meters available to measure radiation and locate contamination. Physicists performing equipment testing and radiation workers who handle radiopharmaceuticals most commonly use survey meters for contamination control.

There are several types of survey meters, including Geiger-Mueller (GM); low energy gamma or scintillation; ion chamber; and liquid scintillation counters. The portable GM survey meter is best used for high-energy beta and gamma emitters. It is primarily used to detect the presence of radiation rather than provide exact measurements. The thin crystal scintillation survey meter is used to locate I-125 contamination and to conduct surveys around low-energy X-ray sources. The liquid scintillation counter is not portable but is the most versatile counting instrument because it has a high counting efficiency for a wide range of radionuclides. Gamma counters are not portable and are used to count wipe tests for photon emitters, such as Cr-51 or I-125.18

Radiation Safety
According to the NRCP in 2006, Americans were exposed to more than 7 times as much ionizing radiation from medical procedures as was the case in the early 1980s.The increase was primarily a result of the growth in the use of medical imaging procedures and the utilization of CT and nuclear medicine. The number of CT scans and nuclear medicine procedures performed in the United States in 2006 was estimated to be 67 million and 18 million, respectively.3 Even though these statistics are alarming and we should be doing everything possible to reduce patient exposure and keep exposure ALARA, it sometimes helps to put radiation exposure into perspective. This perspective is good for not only imaging professionals who receive occupational exposure, but also for patients who receive medical exposure. Radiation workers have a duty to address patient concerns regarding radiation exposure.

The greatest concern about ionizing radiation stems from its potential to cause malignant diseases in people exposed to it and inherited defects in later generations. The likelihood of such effects depends on the amount of radiation that a person receives, whether from a natural or artificial source. If the dose is lower, or is delivered over a longer period of time, there is a greater opportunity for the body cells to repair, and there may be no early signs of injury.2 According to the Biological Effects of Ionizing Radiation Committee V, the risk of cancer death is 0.08% per rem for doses received rapidly (acute) and might be 2 to 4 times (0.04% per rem) less than that for doses received over a longer period of time.19 This is only an estimate. Most radiation exposure involves low doses delivered over long periods. At low levels of exposure, studies of cancer incidence in the exposed population do not provide any direct evidence about the relationship between dose and risk because the number of extra cancers that might be expected to result from the radiation exposure is too small (compared to the total number of cancer cases in the population) to detect.2 The benefit of any procedure involving radiation must outweigh the risk of that procedure. Nevertheless, the procedures can be harmful and people must be protected from unnecessary or excessive exposures.

Modality Radiation Safety
Reducing patient exposure and increasing the patients' comfort regarding amounts of radiation can be accomplished primarily through communication and ALARA regardless of what type of radiation procedure is being performed. Communication with the patient is critical. Communication with physicians and the medical team is equally essential.

The clinician should order tests based on their best clinical judgment and the probability of the diagnosis provided by the outcome of the test. Knowing the risk involved with radiation exposure to a patient is not always at the forefront on the clinicians mind, so what can radiographers do? Communicate, communicate, communicate. If it is noticed that the patient has recently had that same test performed and it has been ordered again, double check with the physician or their proxy (eg, physician assistant or nurse practitioner) to assure that it needs to be repeated. Be an advocate for your patient.

Communicate to the patient that because different tissues and organs have varying sensitivity to radiation exposure, the actual radiation risk to different parts of the body from an X-ray procedure varies. The following comparisons of effective radiation dose with background radiation exposure for several procedures could serve as an education tool for patients (Table 3).20

Table 3

Diagnostic imaging
Imaging is often used to diagnose different diseases. Patient dose in diagnostic imaging can be decreased by:

  • Using high kVp technique: Controls the quality or penetrating power of the photons in the beam.
  • Maintaining image quality control: Decreases patient dose by maintaining all equipment and processes at their highest level of accuracy.
  • X-ray beam filtration: Limits the parameters of the useful beam to a specific size and shape, decreasing area of exposure and scatter radiation.
  • Using a long SID: As SID increases, radiation intensity decreases.
  • Avoiding re-takes: Making sure all technical factors and positioning is correct prior to making exposure.
  • X-ray beam collimation: Decrease area of radiation exposure, thus decreasing dose.
  • Using shields: Use all shielding available whenever possible, but do not allow shielding to interfere with image.

There are many tools that can be used in diagnostic imaging to decrease patient and radiographer dose. It is important to use each tool correctly and consider the quality of the resultant image.

Computed tomography
American's exposure to radiation has nearly doubled over the past 2 decades, largely because of tests such as CT.21 The US Food and Drug Administration has been investigating accidental overdoses and may require that imaging machines display patients' radiation dose and sound an alert if doses go above certain levels. The agency would like scanners to be able to make electronic records of radiation doses so patients can keep track of their cumulative dose.21 Another way to decrease CT dose to patients is to use the proper algorithms for specified examinations. Unfortunately, none of these steps will prompt decreased use of CT scanners.

Pediatric computed tomography
When children need a CT scan, it is important to utilize a "child-size" dose to obtain the images. Children are more sensitive to radiation and have a lifetime to manifest those changes.22 The following 5 simple steps can improve pediatric patient care in CT22:

  1. Increase awareness for the need to decrease radiation dose to children during CT scanning. Encourage your fellow professionals to get involved in the effort.
  2. Be committed to make a change in your daily practice by working as a team with your radiologist, physicist, referring doctors, and parents to decrease radiation dose.
  3. Know you practice standards, as designated by the American Society of Radiologic Technologists
  4. Work with your physicist, radiologist, and department manager to review your adult CT protocols; then downsize the protocols for children.
  5. Be involved with your patients. Be the patient's advocate.

Nuclear medicine
In nuclear medicine procedures, a very small amount of radioactive materials is inhaled, injected, or swallowed by the patient. Remember, nuclear medicine involves gamma rays instead of X-rays. However, ALARA must still be practiced.

The 2 potential hazards in nuclear medicine are from radioactive contamination and radiation exposure. Contamination is the uncontrolled spread of radioactive material. Radioactive contamination can be easily detected with the use of Geiger counters or portable scintillation counters. Nuclear medicine technologists perform other forms of radiation protection and quality control; however, many of the same patient safety precautions are followed in this modality as in the others.

When working in the nuclear medicine radioisotope laboratory, otherwise known as the "hot lab," it is important to work quickly and efficiently so as to keep exposure ALARA. Eating, drinking, smoking, and loitering should never be permitted when working with radioisotopes.

Communication with the patient is crucial so they are aware of what they can do to assist during the nuclear medicine study. For example, patients need to remain still while being injected with radioactivity and they also need to maintain a secure seal while inhaling radioisotopes. The following information must be visually inspected and verified on every request before initiating a nuclear medicine procedure16:

  • Patient's name
  • 2nd identifier such as birth date or social security number
  • Requesting physician's name
  • Patient history, condition, and preliminary diagnosis
  • Correct radiopharmaceutical for the examination
  • Contraindications that can interfere with the radiopharmaceutical biodistribution
  • Patient's physical limitations
  • Allergies or potential drug interactions
  • Potential nuclear medicine radiopharmaceutical interference with other diagnostic or therapeutic procedures
  • Patient concerns

Above all, educate the patient on the examination they are having and what they can do to make it a success. Also make them aware of any post-procedure guidelines.

Fluoroscopy: stationary and mobile
During fluoroscopy procedures, the patient dose is principally determined by the on time of the X-ray beam, therefore the dose is proportional to the fluoroscopy time. In order to protect the patient as well as radiation workers, it is important to limit the radiation on time. This can be accomplished through proper room preparation such as having the proper tools needed for the procedure ready and available. Communication with the patient is key. During the procedure, giving instructions to the patient will help the patient tolerate the procedure, be more comfortable, and know what he or she can do to assist. Proper patient positioning and communication often limit the length of fluoroscopy examinations.

The patient becomes the principal source of radiation exposure due to scatter radiation during fluoroscopy procedures. Radiation can scatter up to 6 feet from the surface of the patient where the X-ray beam enters. Yet another reason to maintain excellent communication with the patient is to reduce fluoroscopy time. Fluoroscopy procedures can occur in the operating room, specialty laboratories, and general radiology departments and are used in the diagnosis and treatment of cardiovascular, gastrointestinal, and orthopedic diseases, as well as a tool for interventional procedures, therefore the patient may not always be awake. This does not lessen the need to provided excellent radiation protection.

During fluoroscopy procedures, the radiation source is normally located under the patient, while the image intensifier is located above the patient. This is true regardless of in which department the fluoroscopy equipment is located. Because the largest amount of scatter radiation is produced where the X-ray beam enters the patient, by positioning the X-ray tube below the patient you decrease the amount of scatter radiation that reaches staff. Traditional radiographic/fluoroscopic rooms are fixed units that do not rotate, and they are primarily located in the diagnostic imaging department. C-arm fixed units used for interventional/cardiovascular procedures have the capability to rotate into different positions, and are located either in the imaging department or interventional/catheterization laboratory. Mobile C-arm fluoroscopy units are primarily used in the operating room. Unique to C-arm fluoroscopy is the spacer device which helps maintain distance between the patient and the radiation source.

Good radiation safety practices must be followed in order to protect the patient, physicians, nurses, and technologists. The basic guidelines remain the same. Minimize the time near the radiation source, maximize the distance from the radiation source, and use shielding devices whenever possible. Whenever possible, take 1 or more steps back from the table. By simply taking 2 steps backward from the patient, the radiation exposure will decrease by a factor of 4. Three steps back will decrease the exposure by a factor of 9. Do not put your hand in the beam unless absolutely necessary for the procedure. Use all available shielding. Stationary fluoroscopy units will have lead skirts on the equipment. Utilize mobile lead shielding, lead aprons, thyroid shields, lead gloves, and leaded eyeglasses depending on the type and amount imaging being performed. "Beam On" time needs to be minimized. This needs to be communicated to the physician because they primarily control the fluoroscopy pedal. Use short taps of fluoroscopy. Be aware of fluoroscopy on-time by the watching for the visual "Beam On" light that illuminates when radiation is being generated. Communicate with the physician when the fluoroscopy timer has been reset. Most timers are set for 5-minute intervals. Make sure the clinician is aware of the "last image hold" and "last fluoroscopy hold" feature. They can utilize this feature instead of re-exposing the patient, which in turn re-exposes everyone. Low dose mode is also an option.

The patient's skin should never touch or be near the X-ray source. The image intensifier should be as close to the patient as possible, which will reduce the radiation dose to the patient and staff. Collimation of the X-ray field is key. The field size should never exceed the area of clinical interest. Collimating tightly will reduce patient and staff dose and reduce scatter radiation, which will improve image contrast.

The growing number and types of procedures utilizing fluoroscopy are similar to the increased numbers seen in other modalities. In addition, there are more overweight and obese patient who require higher energy X-rays and higher radiation does to penetrate their bodies. Most increases in radiation doses are being seen in cardiac catheterization and interventional radiography.

Patients should be informed when they are going to have an extended fluoroscopic procedure. They also should be educated about how to identify a skin injury that can occur due to long fluoroscopy times. They need to be aware of pain or tenderness of the skin; redness or any skin discoloration; rash, blisters, or peeling; appearance of sunburn; and hair loss in the affected area.

Mobile imaging
Radiography in the general department is usually under controlled conditions. The room is lead lined for protection. The control panel is the safe area for the radiographer to stand during the exposure, and staff and visitors, guided by posted signs or buzzer systems, are usually made aware of exactly where the radiation danger lies.23 This is not the case for mobile radiography. The radiographer does not have control of the environment, yet is still responsible for the radiation protection of the patient, visitors, roommates, co-workers, and themselves.

In addition to removing people from the area, other radiation protection methods may be used20:

  • Always direct the central beam away from patients who cannot be removed from the room.
  • Keep the exposure time to a minimum.
  • Always use lead shielding if possible.
  • Reduce repeats by double checking positions before exposure or by checking previous radiographs for the fracture site or exposure factors.
  • Use high kVp techniques to reduce patient exposure.
  • Collimate properly to the part of interest
  • Use grids only when necessary because using grids requires higher exposure techniques which will not only increase patient dose but will also increase scattered radiation to the surrounding area.
  • Always advise co-workers and visitors to leave the area during the exposure. Before making the exposure, call out "X-ray" so that others will know to step away.

A lead apron should always be worn by the radiographer and if at all possible stepping back at least 6 feet from the radiation source is advised. If the patient can still be visualized, leaving the room to step around a corner is acceptable. If others cannot leave the room, covering them with a lead shield is advised. Do not assume they know the dangers of radiation. It is the radiographer's responsibility to provided protection and education.

Conclusions
Risks associated with ionizing radiation are complex. There are many variables to consider, such as patient size, age, the region of the body being imaged, and the type of radiation generating equipment being utilized. Imaging procedures are important for determining appropriate treatment and imaging professionals play a vital role in providing not only the images that assist with that treatment but also the patient care that protects and educates the patient. As imaging modalities and the number of procedures continue to grow, it is imperative that radiographers use every means at their disposal to protect the patient, patient families, co-workers, and themselves.

References
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2. Ford J, ed. Radiation, People and the Environment. Vienna, Austria: IAEA Division of Public Information: 2004; Chapters 1, 4, 5. Available at: http://www.iaea.org/Publications/Booklets/RadPeopleEnv/index.html. Accessed July 27, 2010.

3. National Council on Radiation Protection and Measurement. Report No. 160: Ionizing radiation exposure of the population of the United States. Available at: http://www.ncrponline.org/Publications/160press.html. Accessed July 27, 2010.

4. World Health Organization. What is ionizing radiation? Available at: http://www.who.int/ionizing_radiation/about/what_is_ir/en/index.html. Accessed October 26, 2010.

5. Oak Ridge Institute for Science and Education. Guidance for radiation accident management: radiation emergency assistance center/training site. Characteristics of alpha radiation. Available at: http://orise.orau.gov/reacts/guide/alpha.htm. Accessed July 27, 2010.

6. Oak Ridge Institute for Science and Education. Guidance for radiation accident management: radiation emergency assistance center/training site. Characteristics of beta radiation. Available at: http://orise.orau.gov/reacts/guide/beta.htm. Accessed July 27, 2010.

7. Oak Ridge Institute for Science and Education. Guidance for radiation accident management: radiation emergency assistance center/training site. Characteristics of gamma radiation and X-rays. Available at: http://orise.orau.gov/reacts/guide/gamma.htm. Accessed July 27, 2010.

8. Greater-Than-Class C Low-Level Radioactive Waste EIS Information Center. Radiation basics. Available at: http://www.gtcceis.anl.gov/guide/rad/index.cfm. Accessed July 27, 2010.

9. SI radiation measurement units: conversion factors. SteveQuayle.com. Available at: http://www.stevequayle.com/ARAN/rad.conversion.html. Accessed October 29, 2008.

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12. Princeton University. X-ray safety training for users of the Rigaku MiniFlex X-Ray Diffractometer in PRISM. Available at: http://web.princeton.edu/sites/ehs/radiation/Xraytraining/RigakuMiniflexPrism.htm. Accessed October 19, 2010.

13. Brateman. The AAPM/RSNA physics tutorial for residents: radiation safety considerations for diagnostic radiology personnel. RadioGraphics. 1999:19:1037-1055. Available at: http://radiographics.rsna.org/content/19/4/1037.abstract. Accessed on July 27, 2010.

14. US Department of Labor. Occupational Safety & Health Administration. Radiology module. Available at: http://www.osha.gov/SLTC/etools/hospital/clinical/radiology/radiology.html. Accessed October 19, 2010.

15. NDT Education Resource Center. Film badges. Available at: http://www.ndt-ed.org/EducationResources/CommunityCollege/RadiationSafety/radiation_safety_equipment/film_badges.htm. Accessed July 30, 2010.

16. Papp J. Quality Management in the Imaging Sciences. 1st ed. St. Louis, MO: Mosby, Inc; 1998:245.

17. Laurus Systems. Dosimeters and readers. Available at: http://www.laurussystems.com/Dosimeters_and_Readers.htm. Accessed October 19, 2010.

18. Radiation safety for laboratory workers. University of Wisconsin, Milwaukee. Available at: http://www4.uwm.edu/usa/safety/radiation_safety/labworkers_2.cfm. Accessed on August 2, 2010.

19. Radiation and risk. Idaho State University. Available at: http://www.physics.isu.edu/radinf/risk.htm. Accessed on August 3, 2010.

20. Radiation exposure in X-ray examinations. RadiologyInfo.org. Available at: http://www.radiologyinfo.org/en/safety/index.cfm?pg=sfty_xray. Accessed on August 3, 2010.

21. Szabo L. FDA may require safer CT scans to prevent unnecessary radiation. USA Today. Available at: http://www.usatoday.com/news/washington/2010-02-09-fda-radiation-scans_N.htm. Accessed May 5, 2010.

22. What can I do? Technologists. Image Gently: The Alliance for Safety in Pediatric Imaging. Available at: http://www.pedrad.org/associations/5364/ig/index.cfm?page=391. Accessed August 3, 2010.

23. Peart O. Mobile imaging part 2: the equipment, techniques and complications. Imaging. Available at: http://www.rt-image.com/0701mobile2. Accessed August 6, 2010.

 

Comments/Questions

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Radiation Safety: A Growing Concern

 
» Comment From: davehall » Posted on: 11/22/2010 14:38 PM
Good basic review of what all radiographers should already know and practice daily.
 
» Comment From: Mary F. Stoft » Posted on: 11/26/2010 12:02 PM
God information. Updated to todays concerns.
 
» Comment From: ggchavez » Posted on: 05/24/2011 14:24 PM
This was very helpful and educating. I needed the review.
 
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