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657 Operator ProtectionEDUCATIONAL OBJECTIVESUpon completing this chapter, the student will be able to:1. Dene the key terms listed at the beginning of the chapter.2. Discuss concepts related to operator dosage and protection, including maximum permissible dose (MPD), exposure technique, radiation monitoring, protective barriers, and the ALARA principle (concept).3. Discuss how to deal with patients’ concerns about and possible fear of dental radiographs.radiation that an occupationally or nonoccupationally involved person can receive within a specic period of time without experiencing injury. At present, the NCRP’s recom-mendation regarding the MPD of whole-body radiation for persons occupationally concerned with ionizing radiation, such as dental professionals (including dentists), is 50 mSv (5000 mrem) per year. is is in contrast to the current recommended MPD of 5 mSv/year (500 mrem/year) for the general public (nonoccupationally involved persons) if the exposure is infrequent. Additionally, the NCRP states that for pregnant dental professionals, the recommended MPD should not exceed 0.5 mSv (50 mrem) per month during the pregnancy.It is also recommended by the NCRP that dental person-nel should not exceed a maximum accumulated lifetime dose known as the cumulative eective dose (CUMEfd). e NCRP states that for an occupationally involved individual, it should not be in excess of N (the person’s age) × 10 mSv. For example, if the dental radiographer is 28 years old, the radiographer’s CUMEfd would be 28 × 10 mSv (1000 mrems), which is 280 mSv (28,000 mrems). However, another option in calculating a maximum accumulated lifetime dose is to use the following equation: Nage mSvmrems=()−×()18 50 5000In this equation, the rst 18 years of one’s life is removed from the lifetime dose, because it is not recommended that a person work with x-radiation before the age of 18 years old.Introductionis chapter addresses the steps that should be taken to protect the dental professional from unnecessary radiation exposure in the dental occupational facility. It is of utmost importance for operators to follow radiation safety regula-tions while working with x-radiation in their workplace. ere are radiation safety regulations at both the federal and state levels in the United States. However, the state-governed radiation safety regulations vary from state to state. Consequently, dental professionals should be familiar with their state’s regulations.Operator Dosage and Protectione sources of potential exposure to the dental professional are the primary beam, head leakage from the tube, and secondary (scatter) radiation originating from the patient, x-ray machine, or objects in the operatory. rough the use of careful technique in a well-designed, well-equipped, and well-monitored oce, the occupational exposure of dental professionals to ionizing radiation can be kept to a minimum. In eect, the occupational dose should be zero.Maximum Permissible Dosee National Council on Radiation Protection and Mea-surements (NCRP) denes the maximum permissible dose (MPD) as the maximum amount of whole-body KEY TERMSALARA principle (concept)barriercumulative eective dose (CUMEfd)exposure techniquelm badgemaximum permissible dose (MPD)monitoring devicespocket dosimetersprimary radiationsecondary radiation 66 CHAPTER 7 Operator Protectionby the dental radiographer, patient, or any other person (e.g., patient’s companion). ere should not be any excep-tions to this rule. Ideally, for proper exposure technique, the operator should be a minimum of 6 feet (2 meters) away from the tube head (the source of radiation) and behind a suitable (acceptable) barrier when the exposure is made.Federal and state regulations require that every x-ray machine be equipped with an activated exposure switch that allows operators to properly position themselves 6 feet (2 meters) away from the source of radiation (i.e., the tube head). Although not as crucial as distance and shielding, knowing the areas of minimum scatter is important to the operator. ese areas are at right angles (perpendicular) to the x-ray beam and toward the back of the patient (Fig. 7.1). e areas of highest scatter are in back of the tube head and behind the patient. Correct positioning of the operator still necessitates the minimum 6-foot distance and adequate barrier protection (Figs. 7.2 and 7.3). Also, operators must make sure that coworkers are not in the way of the primary beam or scatter radiation. Operators should check that the work area in all directions is clear before pressing the exposure button.Radiation MonitoringHow can dental professionals and dentists know the amount of occupational exposure of radiation that they receive? Concerned personnel can use two methods to measure the levels of radiation and potential exposure. First, a Certied Radiation Equipment Safety Ocer (CRESO) can perform a radiation survey using ionization chambers to determine radiation levels during exposures at all locations in the Another regulating organization, the International Com-mission on Radiation Protection (ICRP) has recommended that the yearly MPD for occupationally involved personnel be 20 mSv (2000 mrem). ey also recommend an MPD of 1 mSv (100 mrem) per year for the general public. Both recommendations are set lower than the MPD for occupationally involved individuals and the general public set by the NCRP. However, the NCRP, in its most recent report, has chosen to maintain its suggested MPD for dental personnel as stated previously (5000 mrem/year; 50 mSv/year). Ultimately, dental professionals (including dentists) should strive for an occupational dose of zero. If one’s occu-pational dose is zero, any downward change in the MPD would produce no cause for concern because zero is zero. Zero exposure is not dicult to achieve in a dental facility that is well designed, well equipped, and well monitored and whose members have an awareness of radiation hygiene. A dental professional should not fear working with x-rays but should be knowledgeable regarding their safe use and potential abuse.HELPFUL HINTWhen working with x-radiation, it’s better to be safe than sorry! Protect yourselves and your colleagues from unnecessary exposure in the workplace.0LQLPXPVFDWWHU0LQLPXPVFDWWHU0D[LPXPVFDWWHU0D[LPXPVFDWWHU• Figure 7.1 Areas of minimum and maximum scatter during dental x-ray exposure. Exposure TechniqueDental professionals (including dentists) should never be in the path of the primary beam. ey should not hold any receptor (lm packet, digital sensor, or phosphor plate) in the patient’s mouth nor should a drifting tube head be held 67CHAPTER 7 Operator Protectionprovide an accurate reading of occupational exposure. Each operator should have one’s own badge, which should not be shared with other members of the dental facility. If clipped to a pocket, it should not be covered with a pen or piece of jewelry that might shield the badge. Dental professionals should not wear the badge outside the oce, especially in sunlight, and they should remove it if they are having medical or dental x-rays because it is intended to measure only occupational exposure.Protective Barrierse walls, oor, and ceiling of the x-ray operatory must be of such construction that the surrounding areas are shielded from both primary and secondary radiation. is does not mean that they must be lead lined. Many materials used in construction today in the proper thickness provide adequate protective shielding. Because of the relatively low workload and the low x-ray energies used (60–90 kV), dental oces with concrete or cinder block walls have enough inherent shielding in wall construction materials. Drywall construc-tion, if of proper thickness, is also sucient for dental shielding.e shielding or barrier requirements are based on such factors as workload, use and occupancy factors, maximum kilovoltage, and distance from the tube head. e formula W × U × T is used to calculate the guide number. In this formula, W is the workload (in milliampere minutes per week), and U is the use factor. e walls in dental radiography have a higher use factor (14) than the oors or ceiling (116), because the central ray is never directed straight up or down. T is the occupancy factor, which accounts for whether a person is behind the barrier all the time, as is one seated at a desk (T = 1); sometimes, as in a waiting room (T = 14); or occasionally, as in a passageway (T = 18). e guide number is correlated with the proper kilovoltage and distance in reference tables found in Report 35 by • Figure 7.2 The dental professional must stand outside the path of the primary beam. Here, the operator is outside the operatory for safety. • Figure 7.3 Portable x-ray shield. • Figure 7.4 A direct ion storage (DIS) dosimeter measures the ionizing radiation exposure dose incident by calculating the amount of proportional change in the voltage across the memory cells. (Courtesy Mirion Technologies, Dosimetry Service Division, Irvine, CA [www.mirion.com].)oce. is type of survey, which is very much like a survey done by local or state agencies, checks the reliability of the x-ray machine and protective barriers. It does not monitor the day-to-day activity of the concerned personnel.e second method is to have personnel wear monitor-ing devices, such as pocket dosimeters or lm badges. Of the two methods, lm badges are less expensive and more widely used. Film badge service is readily available from many radiation survey companies at a nominal monthly cost. e badge (Fig. 7.4) is usually worn for a specied period of time. It contains a sensor that is labeled with the wearer’s name and, in some cases, the wearer’s identication number as well. At the end of the prescribed reporting period, the lm badge is returned to the survey company, where it is processed. e density on the receptor is compared with standards, and the exposure is determined. e report that is returned to the dental oce contains not only the exposure for the reporting period but also the accumulated quarterly, yearly, and (if available) lifetime exposure of the individual. e lm badge should be worn in the oce at all times to 68 CHAPTER 7 Operator Protectionof dental radiographs. Recent years have been marked by a rise in members of the public who are more aware of the risks associated with x-radiation exposure. e media have been replete with stories warning of the danger of medical and dental radiographs.Dental professionals, through knowledge and under-standing, must be able to allay patients’ fears and explain the necessity of radiographs for proper dental treatment. A patient is likely to question the dental supportive sta, as well as the dentist, about the potential danger of radi-ography. It may be helpful to explain to the patient how essential radiographs are in the detection and management of diseases and treatment planning. It is important to stress that the benet of a dental radiographic examination in a safe and protected environment outweighs the risks of exposure. Patients also can be informed of federal and local laws enacted for their protection. e patient should be informed that the radiographs that are exposed are “pre-scribed” according to their immediate dental health needs, risk factors for dental diseases, and radiation history. ey can be reminded of the various ways that they are protected against unnecessary radiation exposure, such as wearing a protective (lead or lead equivalent) apron and thyroid collar, the use of digital sensors or fast-speed lm, and the avoidance of retakes by employing proper radiographic techniques. It may also be helpful to emphasize that the lm or sensor is being held by a receptor-holding device rather than by the patient’s nger. In addition, there are also printed educational materials that can be distributed to the patients either in support of or in place of an informal chairside discussion.the NCRP. ese tables give the specications of materials necessary for adequate shielding for the given conditions.Pregnancye pregnant dental professional, in relation to occupa-tional exposure, should not be compared with the pregnant patient, as discussed in Chapter 5. In a well-designed and well-monitored dental oce, the occupational exposure should be zero. If a pregnant dental professional or dentist follows proper procedure in such an oce, there is no risk to the fetus. A pregnant worker should wear a lm badge to document occupational exposure and allay any fears. e courts have held that there is no reason to change chairside or other duties during pregnancy because of concern about radiation exposure. As previously mentioned, the NCRP states that for pregnant dental professionals, the recom-mended MPD should not exceed 0.5 mSv (50 mrem) per month during the pregnancy. However, there are specially designed lead aprons available for pregnant operator usage if they are requested by the operator or deemed necessary.ALARA Principle (Concept)As discussed in Chapter 6, the ALARA principle (concept) is an acronym for “as low as reasonably achievable. is principle applies to both patient and operator protection in the eld of dental radiography. e clinical application of this concept to the dental practice encourages dental profes-sionals to minimize radiation exposure to their patients and to themselves while maximizing the diagnostic capabilities of x-ray exposure.Patient Concerns and EducationDental professionals and dentists should understand and be sensitive to patients’ concerns about and possible fear Chapter Summary• epotentialsourcesofradiationexposuretothedentalprofessional are head leakage from the x-ray tube head; the primary beam of radiation; and secondary (scatter) radiation originating from the patient, the x-ray machine, or objects in the x-ray operatory.• Technically,thex-rayexposuretothedentalprofessionalin a well-monitored, well-designed, well-equipped oce should be zero if all of the radiation safety precautions are adhered to accordingly.• e maximum permissible dose (MPD), as developedby the National Council on Radiation Protection and Measurements (NCRP) and the International Com-mission on Radiation Protection (ICRP), is dened as the maximum amount of whole-body radiation that an occupationally or nonoccupationally involved individual can receive within an established period of time without experiencing injury.• eoperatorshouldbe6feetawayfromthex-raysourceand/or behind an acceptable barrier while exposing a patient to x-radiation.• Dental radiographers can wear a personal monitoringdevice, such as a pocket dosimeter or lm badge, to detect any radiation exposure that they may have received in the working environment.• erearespecicrecommendationsforpregnantdentalprofessionals who are in a working environment where dental radiographs are being exposed.• Dental professionals should be prepared to obtain theknowledge and understanding necessary to allay a patient’s concerns and fears pertaining to dental radiography. 69CHAPTER 7 Operator ProtectionChapter Review QuestionsMultiple Choice1. e MPD for whole-body ionizing radiation exposure for occupationally involved persons is currently: a. 500 mSv per year b. 5 mSv per year c. 5000 mSv per year d. 50 mSv per year2. It is recommended that dental personnel not exceed a maximum accumulated lifetime radiation dose known as the: a. Cumulative maximum allowance b. Cumulative dose allowance c. Cumulative eective dose d. Cumulative regulated dose e. Cumulative exposure dose equivalent3. e areas of minimum scatter while exposing radiographs are (indicate all that apply): a. Areas that are at right angles to the primary beam b. Toward the front of the patient c. In the back of the tube head d. Behind the patient e. Toward the back of the patient4. e acronym CRESO pertaining to radiation monitor-ing stands for: a. Certicate for Radiation Eects Systems Organizer b. Contracted Radiation Eciency Systems Ocer c. Certied Radiation Equipment Safety Ocer d. Contracts for Radiation Equipment State-based Organization e. Certied Radiation Eciency Systems Organizer5. e ALARA principle (concept) refers to minimizing radiation exposure to the patient only. Operator pro-tection is not a concern when abiding by the ALARA principle (concept). (Indicate all that apply.) a. Both statements are true. b. Both statements are false. c. e rst statement is true, and the second statement is false. d. e rst statement is false, and the second statement is true. e. e statements are related.Critical Thinking Exercises1. e barrier or shielding requirements for those surfaces involved in workplace radiation protection are based on several factors. a. Name these factors. b. Explain what the equation W × U × T is used to calculate. c. Explain what each of the components in the equation W × U × T stand for and how they are related to establishing safe barriers and shielding in a dental facility.2. One of your coworkers just found out that she is preg-nant and is concerned about exposing dental radiographs on patients in the dental facility where you both work. What information could you provide to her regarding her current status? Include all of the following in your explanation: a. What is the risk to the fetus in a well-designed and well-monitored dental oce? b. What is the risk to the fetus if the dental professional follows proper radiographic procedures? c. What personal radiation devices can be worn to docu-ment occupational exposure and protect the pregnant dental professional? d. What do the courts recommend? e. What is the NCRP-recommended MPD for pregnant dental radiographers?BibliographyAmerican Academy of Dental Radiology, Quality Assurance Com-mittee: Recommendations for quality assurance in dental radiog-raphy, Oral Surg 55:421–426, 1983.American Dental Association: e benets of x-rays. Chicago, IL, 1993, American Dental Association.Goren AD, Lundeen RC, Deahl ST 2nd, et al: Updated quality assurance self assessment exercise in intraoral and panoramic radi-ology, American Academy of Oral and Maxillofacial Radiology, Radiology Practice Committee, Oral Surg Oral Med Oral Pathol Oral Radiol Endod 89:369–374, 2000.Macdonald JCF, Reid JA, Berthory D: Dry wall construction as a dental radiation barrier, Oral Surg 55:319–326, 1983.National Council on Radiation Protection and Measurements. NCRP Report No. 145, Radiation Protection in Dentistry, 2004.National Council on Radiation Protection and Measurements. NCRP Report No. 116, Limits of Exposure to Ionizing Radiation, 1993.Plunket L: When an employee becomes pregnant, N Y State Dent J 62:9–11, 1996.