NCRP/FDA Regulations & Occupational Exposure Management


-- Please note: ***Articles are Free with membership***

Occupational radiation exposure is regulated by the National Council of Radiation Protection and the FDA. Radiographers are required to know the regulations and maintain their occupational radiation exposure within the guidelines. Employers monitor employee exposures using a Radiation Safety Officer. This article explores the regulations and how they impact on the work of medical imaging professionals. The reader will gain a good understanding of the NCRP guidelines for full and partial body exposure.
>> Also approved for Florida State License.
>> Also approved for Iowa State License.


Author: Nicholas Joseph Jr., RT(R)(CT)
Credits: 1.5

-- Please note: This article is either under construction or in the approval process. There will be no credit available for this article until the approval process has been completed. Passing the test for this article before the approval process has been completed WILL NOT result in full credit being awarded when the approval process has been completed. You must pass the test for this article after the approval process has been completed in order to receive credit for this article.

-----------------

Instructions:

This activity may be available in multiple formats or from different sponsors. ARRT does not allow CE activities such as internet courses, home study programs or directed readings to be repeated for CE credit in the same or any subsequent biennium”

Article navigation:

Objectives

Outline

Introduction

Section 5.1: NCRP reports providing guidelines for radiation protection

Section 5.2: Dimensions of Radiation Measurement

Section 5.3: NCRP Directive to Monitor Occupational Dose

Section 5.4: Dose-equivalent (DE) and Effective Dose Equivalency (EDE)

Section 5.5: Effective Dose Limits and NCRP Recommendations

Section 5.6: Occupational Exposure and ALARA

References

Bottom





Objectives:

Upon completion the reader will be able to:
  • List some of the organizations and state their role in research, standards, enforcement of regulations, and disseminating information about ionizing radiation to the public.
  • Discuss the role and functions of the National Council on Radiation Protection and Measurement (NCRP).
  • State what the BEIR reports are and discuss their relationship to radiation safety standards in health care environments.
  • Match NCRP reports with their title and contents.
  • State the three parts of a radiation safety program that the radiation safety officer (RSO) enforces.
  • List the three common units of radiation measurement and discuss what these units tell us about radiation exposure.
  • Define radiation units' roentgen, rad, rem, and Curie.
  • Define the term RBE and discuss its importance
  • Define the term LET and discuss its role in radiation biology.
  • Discuss what is meant by quality factor and discuss why it is used to describe different types of ionizing radiations.
  • List personnel mandate by the NCRP for personnel monitoring, and give examples of personnel other than radiographers who should be monitored.
  • Define radiation deep dose (DDE) and shallow dose (SDE).
  • Define effective dose and discuss its importance to biological tissue.
  • Discuss why a tissue weighting factor and a radiation weighting factor is used to calculate the effective dose.
  • Discuss why the effective dose is important to occupational exposure, and discuss what the data tells us about long term effects of exposure.
  • Define stochastic and nonstochastic effects of ionizing radiation.
  • Define dose equivalence and tell what units are used to express it.
  • Discuss the proper locations for wearing a radiation monitor for general radiography, fluoroscopy, and during pregnancy.
  • State specific DL's for the hands, lens, and whole body annual and cumulative exposure.
  • State the formula for calculating cumulative life time exposure.
  • State the dose limits for educational training in radiography.
  • State the total dose limits to the fetus for the duration of pregnancy and the monthly dose limit for fetal exposure.
  • State the attenuation percent of a 75 kVp beam by a 0.5 mm Pb equivalent apron, and maternal tissues.
  • State the formula for calculating fetal dose.
  • State the ALARA concept as outlined in federal code 10CFR20.
  • State what is meant by investigational level I and level II under the ALARA mandate.
  • List the three commonly used radiation monitoring devices and discuss their advantages/disadvantages.
  • Discuss the radiation monitoring report and how it should be posted for review to maintain individual privacy.





Outline

Introduction

Section 5.1 NCRP reports providing guidelines for radiation protection

  1. The BEIR reports and their significance to NCRP guidelines.
  2. Specific NCRP reports used in medical radiation protection.
  3. NCRP mandate for radiation safety programs in healthcare settings.

Section 5.2 Dimensions of Radiation Measurements

  1. Radiation measurement units: rad, rem, roentgen, and Curie.
  2. Understanding the relative biological effect of ionizing radiation (RBE).
  3. Concept of linear energy transferred to soft tissue (LET).
  4. Comparing the RBE and Quality factor of different types of ionizing radiation.

Section 5.3 NCRP Directive to Monitor Occupational dose

  1. NCRP mandate for monitoring occupational radiation exposure.
  2. Conditions and personnel whose radiation exposure must be monitored.
  3. Measuring deep dose (DDE), shallow dose (SDE), and eye dose (LDE).
  4. Calculating the effective dose and understanding tissue weighting factor and radiation weighing factor in dose measurements.

Section 5.4 Dose equivalence (DE) and Effective dose equivalency (EDE)

  1. Purpose of calculating DE and EDE.
  2. British and S.I units of dose equivalency.

Section 5.5 Effective dose limits and NCRP Recommendations

  1. NCRP reports No 91, 105, and 116.
  2. NCRP Effective dose limits for occupational workers.
  3. Maintaining a radiation safety program that provides room for fetal exposure at anytime should pregnancy be declared.
  4. Calculating fetal dose following attenuation by a 0.5 mm Pb apron and maternal tissues.

Section 5.6 Occupational Exposure and ALARA compliance

  1. Federal mandate for ALARA 10 CFR 20.
  2. Investigational levels established under ALARA.
  3. Monitoring occupational radiation exposure and monitoring devices.
  4. Reading the radiation monitoring report.
  5. Confidentiality under HIPPA when posting radiation monitoring report




Introduction

Perhaps nothing is more regulated in the United States and worldwide than is the use of ionizing radiation, radiation sources, and byproducts of nuclear energy. Regulations that directly apply to the medical use of ionizing radiations are found in publications from six major international organizations and three national organizations. The professional radiographer should have some idea of who these organizations are and their role in administration of radiation safety and protection guidelines. Six international organizations that input information are the: International Commission on Radiological Protection (ICRP), United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), Biological Effects of Ionizing Radiation Committee (BEIR), International Commission on Radiological Units and Measurements (ICRU), Radiation Effects Research Foundation (RERF), and International Radiation Protection Association (IRPA). International organizations do not have authority to enforce their recommendations on nations worldwide; therefore, most countries have their own regulatory agencies through which international cooperation exists. Examples of United States Agencies are: National Council on Radiation Protection and Measurement (NCRP), Nuclear Regulatory Commission (NRC), and the Food and Drug Administration (FDA). Through these organizations and many others, radiation research, recommendations on standards, enforcement of regulations, and disseminating information to the public are accomplished.

image001

Recommendations from the NCRP concerning medical ionizing radiation use and occupational exposure rely on the application of the principle of benefit of exposure to ionizing radiation outweighs its risk. The NCRP also functions as a scientific body that collects, analyzes, develops, and disseminates information for the sake of the public through recommendations on protection and safety from ionizing radiation. Furthermore, the NCRP provides concepts about radiation quantitative and qualitative properties and the applications of measurements in the area of radiation protection. For medical imaging standards, recommendations from the NCRP are considered guidelines that must be followed by all radiology departments and imaging professionals in the United States.




Section 5.1: NCRP reports providing guidelines for radiation protection

NCRP recommendations are directly related to the BEIR V report of 1990. The National Research Council (NRC) under the auspice of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine have issued five reports all of which are titled Biological Effects of Ionizing Radiation (BEIR reports). The most recent of which is the BEIR V report from which many radiation protection recommendations set by the NCRP are based. Some of the more recent NCRP reports that have direct standards for medical ionizing radiation use are contained in these documents and can be ordered directly from the NCRP:

image002

The goals of these reports when used for medical radiation safety programs is to foster a radiation protection program that prevents deterministic effects, and decrease the probability of stochastic effects as a result of occupational exposure to ionizing radiation. Three main parts of a radiation safety program that are enforceable by the designated radiation safety officer (RSO) are: 1) exposure to ionizing radiation overall nets benefits, 2) ALARA is prescribed by all imaging personnel, 3) dose limits are enforced (NCRP report No. 116).

Most health care workers understand that when a radiology procedure or examination is ordered by the patient's physician it is because it may provide beneficial diagnostic information that will help in the patient's treatment. Medical imaging professionals receiving physicians’ orders interpret them as a prescription to administer a prescribed dose of ionizing radiation sufficient to acquire diagnostic images for radiological interpretation. Therefore, no exposure of any person should occur in a medical setting without the written orders of a physician. Orders for radiographic imaging are given the same high standards as a prescription for medication, radiographic orders must come from a licensed physician or owing to their consent of the order. Upon receiving the written or verbal request for a study or procedure, the radiographer may need to consult with the patient's physician or radiologist for clarification of the order, or specific preparation of the patient for the procedure. Proper communication with the patient and physicians is part of the ALARA mandate and does have other legal reflections.

Another issue in radiation protection is that of effective dose limits for occupational exposure. Dose equivalence limits are directives incumbent upon all imaging and non imaging personnel who may routinely be exposed to ionizing radiations. Physicians, nurses, respiratory care specialist, and certainly surgery personnel are affected by these regulations whether they know and practice them or not. In some institutions surgery personnel operate mini-C-arm fluoroscopy units without a basic understanding of the physical principles of ionizing radiations, or specific education in patient and personnel radiation safety. This continuing educational series will enhance their understanding and provide a basic training course on all aspects of ionizing radiation exposure.




Section 5.2: Dimensions of Radiation Measurement

The NCRP recommends that any health care worker who is likely to receive one-tenth of the maximum annual dose equivalent limits be monitored by the radiation safety officer and/or a radiation safety committee. Occupational exposure (NCRP) is stated in terms of effective dose equivalency or effective dose. To understand these NCRP occupational dose limits it is important to understand radiation units adopted by the International Commission on Radiation Units and Measurements (ICRU) who is charged with defining radiation units for international communities as a whole. There are two dimensions used to define radiation measurement: ionization of matter, and deposition of energy into an absorber. Three commonly used units are important to measuring these dimensions of radiation, they are: roentgen (R), rad, rem, and a fourth, the Curie describes atomic disintegration over time.

The roentgen is the unit used to describe the ionization of atoms in air as radiation passes through space. The roentgen actually describes the intensity of a beam of x-rays or gamma rays up to 3 MeV; it is applied only to x-rays or gamma radiation and cannot be used to describe particulate radiations such as alpha, beta, positrons, and neutrons. The roentgen is the unit of radiation exposure and calibration of x-ray generating equipment. The unit of the roentgen (R) is Coulombs/kg. The International Commission on Radiation Units and Measurements (ICRP) set the value of the roentgen at 2.58 x 10-4 coulombs/kg (C/kg or C kg-1) in air.

image003

The radiation absorbed dose (rad) is a unit that describes any type of radiation not just electromagnetic radiations, in a medium other than air. As ionizing radiation passes through matter it imparts energy into the medium ionizing it. One rad is equivalent to 100 ergs of energy absorbed in a gram of material (in our practice, tissue). Notice that the term rad does not reference the intensity of the radiation source, only the amount of energy the absorber absorbs. The ICRU adopted the S.I unit Gray (Gy) as the unit of dose. The Gray is expressed in joules per kilogram (1 Gy = 100 rad). The importance of the rad is that it describes absorption of ionizing radiation in matter and is related to biological damage in tissue. As the amount of energy ionizing radiation transfers to tissue increases so does the quantity of rad. Particulate radiations have high linear energy transfer values (LET) and can cause significant biological effects whereas low LET radiations (gamma and x-rays) will significantly fewer ionizations in tissue and therefore less biological damage. The rad is limited as a unit because it does not reference the biological effect of various types of ionizing radiations like alpha and beta particles and for this reason is an unacceptable unit of occupational exposure.

image004

The roentgen equivalent man (rem) is the unit of biological dose for human exposure, from one or many types of ionizing radiation(s). It incorporates the biological effectiveness (RBE) of different types of ionizing radiation in different types of tissues. The rem is the unit of occupational exposure.

image005

The RBE allows us to compare the ratio of the effects of x-rays or gamma rays to any other type of ionizing radiation producing an identical effect. For example, comparing the amount of photons needed to produce cataract to the amount of alpha particles to produce the same effect. The alpha particle is then assigned a RBE value that can be used in the calculation of the rem. Photon energy for experimental calculation of RBE is fixed at 200-250 kilovolts which is called the orthovoltage range. What the RBE tells us is that different types of ionizing radiations will have different biological effects in different types of tissues. For example, equal doses of x-rays and alpha particles to the same biological tissue will have different effects on that tissue. This is because of the difference in the physical properties of the two types of radiation and their ionization ability. Electromagnetic radiations such as gamma and x-rays have no mass or charge, and can traverse unlimited distance in space. An alpha particle is relatively large by comparison to a photon of electromagnetic radiation, and will be completely absorbed by the human skin. Radiation types having a high quality factor (QF) will also have high LET and a greater potential to biological damage because of the many ionizations they cause over a short track length.

image006

An alpha particle is large, having two protons and two neutrons; it is like a helium atom, but with no electrons. An alpha particle will contain two electrostatic charges making it a source that causes much ionization. We would expect that alpha particles deposit high LET in tissues relative to x-rays. But, due to its mass and charge the alpha particle travels only a short distance in tissue; whereas gamma photons and x-rays will pass through tissue depositing little energy.

To express the biophysical characteristics of all types of particulate and electromagnetic radiations depositing energy in an absorber, the terms linear energy transfer (LET), and the concept of quality factor (Q) are used. These terms are used to calculate occupational dose in rem. The term LET simply describes the transfer of energy from radiation to matter as it passes through it. The higher the LET value for a type of ionizing radiation, the larger is the relative size of that particle and the greater is the charge it contains. When a large highly charged particle of ionizing radiation passes through matter, it imparts more energy to the absorber tissue than does a photon which has no mass or charge. Large charged particles cause more ionizations than electromagnetic radiation that may lead to cell injury or inactivation. Once the experimental quantity of the RBE is known for a type of radiation it is given a relative value called a quality factor (Q).

image007

In radiology disciplines such as nuclear medicine and radiation therapy, there may be times when an internal radiation dose source is encountered as part of the diagnostic or therapeutic treatment of patients. Internal dose measurements depend on the distribution of the dose material; therefore, a dose distribution factor (DF) is also assigned to the calculation of occupational exposure. The occupational exposure rem dose formula for internal dose would be calculated using the formula rem = Q x DF, otherwise the rem is calculated using the formula:

image008

As we stated earlier there are two principles to measuring ionizing radiation, ionizations and energy deposited. We have also described the energy deposited in terms of LET and its effect on biological tissue as the RBE. The other principle is the specific ionization (SI) which is the average number of ion pairs that are produced per unit of path traveled by the incident radiation. A 1 Mev alpha particle causes approximately 60,000 ion pairs per cm traveled in air; it disperses approximately 34 eV per ion pair created. The SI deals with the number of events and LET calculates the energy loss of the incident radiation in matter.

The fourth description applies to radioisotopes used in nuclear medicine and PET imaging, the Curie, which describes a quantity of radioactive material that disintegrates per second. Decay or disintegration is a process by which a radioactive nucleus changes to another type of atomic nucleus. The ICRU recommends the use of the S.I unit named Becquerel (Bq).




Section 5.3: NCRP Directive to Monitor Occupational Dose

The NCRP mandates personnel monitoring programs for all individuals working with ionizing radiation, which includes radiologist, radiographers, physicians, biomedical repair personnel, and others. In addition, the following preconditions mandate monitoring of personnel by the designated qualified radiation safety officer and/or radiation safety committee:

image009

Along with the responsibility for monitoring personnel comes the responsibility for making sure that any person who is occupationally exposed to ionizing radiation is properly educated and understands the biological effects of ionizing radiation. Any individual who administers a radiation dose for diagnostic or therapeutic purpose must be properly educated in all aspects of patient and occupation radiation safety and protection. Furthermore, the radiation safety officer and committee is responsible for making sure all personnel who are routinely in the proximity of ionizing radiation take proper measures to protect themselves. Personnel who may meet the above criteria include surgery personnel who are regularly exposed during C-arm and cystofluoroscopy, non ARRT registered personnel who operate mini C-arm equipment, nurses who assist in fluoroscopy guided endoscope procedures (e.g. ERCP, bronchoscope, interventional procedures, CT biopsies and drainage procedures, and the like.

The hiring and training of laypersons to perform fluoroscopy is becoming a common practice, even in some of the more reputable hospitals and health care centers. The basic instability in their training is that they only get trained in how to minimally operate the equipment, to wear a lead apron, and little if any training on patient and self radiation safety. A good training program would include tissues at risk, risk assessment, dose equivalence limits, ALARA, shielding, pregnancy and radiation exposure, fluoroscopic exposure and monitoring, and other topics that inspire to reduce the risk to personnel and to the patient.




Section 5.4: Dose-equivalent (DE) and Effective Dose Equivalency (EDE)

We stated earlier there are two desired outcomes for a radiation protection program for occupational workers: 1) to limit the risk of stochastic radiation disease frequencies to that of nonradiation workers, and 2) prevent non stochastic radiation diseases to zero by setting dose equivalent limits well below the threshold needed for life long cumulative occupational exposure. Stochastic effects are those effects that are considered statistical effects and are all-or-none by occurrence. Theory has it that there is no threshold dose for a purely stochastic disease, it either happens or it does not. This is because any effects caused by ionization that are stochastic in nature follow a linear-nonthreshold dose response pattern. Nonstochastic radiation effects are those in which a threshold for disease exists and any dose below the threshold dose will not produce the specific disease. The key to understanding stochastic versus nonstochastic effects is to understand that as the radiation dose increases, the probability of disease also increases for stochastic effects; however the severity of the disease does not increase. Likewise, as the dose increases beyond the threshold for a particular nonstochastic disease, that disease will most likely occur. So the goal of radiation safety is to avoid the probability of stochastic and nonstochastic effects in patients and health care personnel by limiting their exposure to ALARA and NCRP occupational exposure limits, respectively.

Any exposure to ionizing radiation is a risk, either to the individual or to the individual's progeny. Just because the probability of disease from medical radiation is low there is no excuse to abandon safe practices. Guidelines are in place to encourage radiation workers to remain on the low probability side of somatic and genetic effects. These can be summarized in terms of dose equivalent limits (DE), which are to be enforced. Dose equivalency is defined as the product of the absorbed dose (D) and the quality factor of the radiation (Q), and any other modifying factor (N).

image010

The standard unit of dose equivalency in the British system is the rem: S.I unit is the Sievert (Sv), which is reported on the monthly occupational exposure report. Dose equivalent is defined as the product of the absorbed dose (D) and quality factor (Q) with any modifying factor (N). Notice that the quality factor for x-rays, gamma radiation, and beta particles is one (1). Since these are the types of ionizing radiation encountered from external sources in diagnostic imaging and nuclear medicine, the dose equivalence becomes dose (D). We can then express occupational exposure as a deep dose equivalent at 1 cm called the DDE. Shallow dose equivalence (SDE) is measured at 0.007 cm, and eye dose equivalence (LDE) is measured at 0.3 cm. All three doses are acquired from the monitoring badge also known as the film badge. The current dose limitation system practiced in the United States is mandated by the NCRP and assumes a linear nonthreshold dose-response relationship. Limitations are set at a risk level to allow life time occupational exposure. Measures are also in place to monitor occupational workers and review their radiation records timely so that limits are not exceeded. It is therefore mandatory that all radiation workers comply in all regards to continuing safety education, staying within imposed limits, and safely operate all x-ray equipment. In order to safeguard these standards for the sake of the public, no person should be allowed to operate medical x-ray equipment unless they have specific education and training in radiation safety, and their occupational dose is monitored.

The effective dose (E) is a way of accounting for the different types of ionizing radiation's effects on biological tissues. Different types of tissues have their unique radiosensitivities to ionizing radiation (see part II of this series). For example, brain and nerve tissue is quite radioresistant compared to lymphocytes which are radiosensitive. The effective dose is what is important to occupational exposure because it is always much less than the actual dose recorded by a monitoring badge as long as protective equipment such as lead apron and thyroid shield, and the like are worn. The effective dose takes into consideration a radiation weighting factor (Wr) which corresponds the to quality factor of radiation, a tissue weight factor (Wt) and the absorbed dose (rad). The EDE is the sum of the deep dose equivalents of the different tissues multiplied by that tissues weighting factor (table 5.4).

image011

The effective dose allows us to reasonably express cancer risk due to late effects of ionizing radiation, and to assess the risk of manifest hereditary effects in the first two generations of progeny due to radiation effects on various tissues and organs.

image012

image013

To achieve these readings a radiation monitor must be worn. It is universally accepted that it should be worn at collar level near the thyroid gland on clothing, or outside the lead vest during fluoroscopy. At gonadal level is also acceptable; however, it is not the most common practice except when two or more monitors are worn. When a collar badge is worn on the outside of a lead apron such as during surgical C-arm fluoroscopy, a conversion factor of 0.3 is multiplied with the effective dose. The conversion factor expresses the dose deep to the lead apron rather than the dose to the apron. If shielding is not used routinely during radiographic imaging the value of calculation is the effective dose.




Section 5.5: Effective Dose Limits and NCRP Recommendations

Effective dose limits are set by NCRP recommendations that are stated in their official reports. The dose limits in this study are based on NCRP report No. 91, 105, and 116 and are applied to occupational exposure only. The official method of reviewing occupation exposure is the radiation monitor (film badge, OSL, or thermoluminescent dosimeter) report from a licensed laboratory. The whole body dose is set at 50 mSv each year, which includes weighted tissue factors. Whole body dose is considerably lower than the dose allowed to specific tissues like the skin, extremities, lens of the eye, etc. This is because a whole body dose will affect many organ systems simultaneously whereas local radiation injury does not affect the whole being. Consider the chart on the following page, which demonstrates some current dose limits for various tissues. Skin for example, has a DL of 500 mSv (50 rem/year), which is unlikely to occur in general diagnostic imaging because x-ray machines do not produce high LET radiations like alpha particles. Radiologist, especially interventional radiologist and orthopedic surgeons whose hands are potentially exposed during fluoroscopy have reason to be concerned about extremity exposure. Limits for the hands and extremities are set at 500 mSv (50 rem/yr). To accurately measure the dose to the hands and upper extremities a wrist or finger badge must be worn.

image014

image015

All of the recommendations found in the chart above are important; however of particular concern to the occupational worker is the "involuntary" dose limitations to the fetus/embryo during the entire pregnancy. NCRP guidelines set fetal exposure at a maximum of 5 mSv (0.5 rem) for the entire pregnancy to be calculated once the pregnancy is declared. If that dose has been exceeded at the time of declaration of pregnancy then the dose for the remainder of the pregnancy may not exceed 0.5 mSv (0.05 rem). This is why it is a good radiation monitory protocol for female technologist of childbearing years to be monitored closely so that their dose is averaged out monthly and quarterly as if pregnancy may be declared at any time. This will "reserve" their pregnancy dose over the total gestational time if pregnancy is declared. Radiation exposure to the fetus is limited to 0.5 mSv/month (50 mrem/mo). Although it is not required, sufficient protection practices should be in place so that the maximum pregnancy dose remains available to a technologist at any time in the year. This level of radiation safety practice is difficult for any radiation safety officer; however, it should be attempted since any overexposure must be reported to the NRC under title 10 CFR20.403.

Professional radiographers should be able to answer for themselves and other health care personnel, how much radiation can the fetus be exposed to and how is that dose is calculated? The most common way is for the pregnant technologist to wear two radiation monitors, one at collar level outside the lead apron, the other is worn inside the apron at fetal level. The fetal monitor is a separate reading from the mother’s and must be labeled as such. Some institutions will do a color coding of the second badge so that it is not accidentally exchanged with the collar badge during the time of monitoring. As we have stated in an earlier module a 0.5 mm lead apron will attenuate approximately 90% of a 75 kVp beam; maternal tissues will absorb an additional 70% of the remnant from the apron. Therefore, the exposure to the fetus is less than 30% of the useful beam penetrating a lead apron. So if the collar badge reads 5 mSv (500 mrem) over the pregnancy, the waist badge should read less than 10% or 0.5 mSv (50mrem). Maternal tissues will attenuate 70% of the remnant radiation from the apron so that only 30% reaches the fetus. When compared to the total dose allowed of 5 mSv (500 mrem), working around radiation during pregnancy or even before pregnancy is negligible when safety measures are enforced.

image016

One assumption in this calculation is that the occupational worker does wear a fetal apron (fetal aprons have an additional 0.5 mm lead at fetal level) so that the protection over the fetus is at least 1.0 mm lead equivalence. This is an important point that non radiation workers miss, especially those working in trauma ER situations who assume just wearing an apron during pregnancy is enough. They should be required by the RSO to wear special pregnancy apron and a second monitor if exposed routinely to ionizing radiation during their pregnancy.




Section 5.6: Occupational Exposure and ALARA

Besides remaining below the NCRP recommendations for occupational exposure the FDA requires that occupational exposure follow the guidelines of ALARA. ALARA is an acronym from the document by The Office of Standards of The Nuclear Regulatory Commission (NRC), "Principles and Practices for Keeping Occupational Radiation Exposure at Medical Institutions as Low as Reasonably Achievable." The radiographer should know that the principle is not an ideological document, but really exist as a condition for institutional licensure by the NRC. As of January 1, 1994, the ALARA standard was incorporated into Title 10 of the Code of Federal Regulations (10CFR20). The practice of ALARA in patient and personnel radiation safety is binding upon management, the radiation safety officer, and the radiation safety committee to develop awareness in the health care community concerning occupational exposure. Two important investigational levels were established under the ALARA guidelines: 1) when the radiation exposure report is reviewed by the RSO and no individual exceeds level I investigational level, no further scrutiny is required, 2) If the quarterly exposure is between level I and Level II the RSO will review and report results to the radiation safety committee to compare the results of a breach with others doing the same job. If an individual's quarterly exposure is greater than Level II then the RSO must take action and report it to management and the radiation safety committee for further investigation. All records must be readily available to the NRC investigator on demand. It stands to reason that the minimum compliance policy must include all individuals meeting the minimum standard for radiation monitoring.

image017

Monitoring radiation exposure is a simple process that involves monitoring an individual or monitoring a field or area in which radiation is used. Personnel working in diagnostic imaging, interventional radiology, surgery, CT, NM, and PET are monitored. In nuclear medicine and PET imaging, personnel and the work area is monitored.

There are at least three commonly used personal radiation monitoring devices used to monitor occupational workers: Film badge, thermoluminescence dosimeter (TLD), and optically stimulated luminescence (OSL) dosimeter. Radiation monitoring film badges contain filters for quantifying the quality of radiation. The type and energy of ionizing radiation exposure measured with a film badge can only be determined for x-rays, gamma radiation, and beta radiation. Film badges are the least accurate of monitoring devices incapable of recording exposure below 10 mR. Readings below the sensitivity of the film badge is reported as minimum on the film badge report. They are sensitive to temperature and humidity and cannot be left in inappropriate locations such as one’s car or on near the television.

Thermoluminescence dosimeters are more sensitive than film badges and are capable of readings as low as 5 mrem. The TLD uses lithium fluoride crystals to store ionizing radiation exposure. When heated, the crystals emit light that is measured by a photomultiplier tube calibrated to the intensity of ionizing radiation. These monitors are not sensitive to heat and humidity and can be exchanged monthly or quarterly.

Optically stimulated luminescence dosimeter is the current radiation monitoring device of choice. These dosimeters are more sensitive than either film badge or the TLD and can be read up to a year following exposure.

image018
A simple film badge or thermoluminescent dosimeter can be used to monitor radiation dose when worn at collar level. Data from the dosimeter is calculated and reported on the monthly radiation report. The picture to the left is of an OSL dosimeter.

Both federal and all states have laws that require the recording of occupational radiation exposure in the form of either a weekly, monthly, quarterly, or annual report. The radiation exposure report contains specific data including the name of the person being monitored, the number on the monitor assigned to them, and various exposure data. Current radiation exposure, cumulative annual exposure, and lifetime cumulative exposure data must be included in the report. It is the responsibility of the radiation worker to request a transfer of occupational exposure documents from one employer to another when there is a change of employment.

image019

Film monitoring reports are generally posted monthly or quarterly so that the wearers can review their radiation exposure. The technologist should pay special attention to the deep dose-it refers to penetrating radiations (gamma and x-rays); the shallow dose measures soft energy such as beta and low energy photons. When the report is posted in the manner above the RSO must be sure that personal information such as the social security number is removed in compliance with HIPPA standards and privacy laws. Personalized reports can also be requested for each employee so that posting of generalized information can be avoided (see personal report below!)

image020




References

  1. *Bushong, S.C., Radiologic Science for Technologist: Physics, Biology, and *Protection, 7th ed., St. Louis, Missouri: Mosby, Inc. 2001.
  2. *Early, P.J., Principles and Practice of Nuclear Medicine, 2nd ed., St. Louis, Missouri, Mosby Co. 1995.
  3. *Seeram, E., Computed Tomography, Philadelphia, Pennsylvania, W.B. Saunders Co. **1994.
  4. *Selman, J., The Fundamentals of X-ray and Radium Physics, 6th ed. Springfield, Illinois, Thomas Books, 1980.
  5. *Sprawls, P., Physical Principles of Medical Imaging, Rockville, Maryland, 1987, Aspen Publishers, Inc.



Copyright image Copyright 2006 Nicholas Joseph Jr.






-- Please note: This article is either under construction or in the approval process. There will be no credit available for this article until the approval process has been completed. Passing the test for this article before the approval process has been completed WILL NOT result in full credit being awarded when the approval process has been completed. You must pass the test for this article after the approval process has been completed in order to receive credit for this article.

Take the test!