Radiology Lecture 12.docx

Lecture 12 Chapter 4 – Radiation Protection Many of the early pioneers in dental radiography suffered from the adverse effects of radiation. Some of these pioneers lost their fingers, limbs, and, ultimately, lives to excessive doses of radiation. The hazards of radiation are now well documented,...

Lecture 12 Chapter 4 – Radiation Protection Many of the early pioneers in dental radiography suffered from the adverse effects of radiation. Some of these pioneers lost their fingers, limbs, and, ultimately, lives to excessive doses of radiation. The hazards of radiation are now well documented, and radiation protection measures can be used to minimize radiation exposure for both the dental patient and the dental radiographer. Patient protection measures can be used before any x-radiation exposure. Proper prescribing of dental images and the use of equipment that complies with state and federal radiation guidelines can minimize the amount of x-radiation that a dental patient receives. The first important step in limiting the amount of x-radiation received by a dental patient is the proper prescribing, or ordering, of dental images. WHAT IS THE FIRST STEP IN PATIENT RADIATION PROTECTION? PROPER RADIOGRAPH PRESCRIPTION WHAT X-RAYS SHOULD A CHILD WITH A HISTORY OF DECAY HAVE? BITEWINGS AND OCCLUSAL WHEN SHOULD X-RAYS BE TAKEN ON AN ADULT WHO HAS LOW CARIES RISK, AND HAD 4BW ONE YEAR AGO? BW EVERY 24-36 MONTHS TABLE 4-1 Two types of filtration (the use of absorbing materials for removing low-energy x-rays from the primary beam) are used in the dental x-ray tubehead: inherent filtration and added filtration. Inherent filtration takes place when the primary beam passes through the glass window of the x-ray tube, the insulating oil, and the tubehead seal. Added filtration refers to the placement of aluminum disks in the path of the x-ray beam between the collimator and the tubehead seal in the dental x-ray machine Added filtration of the x-ray beam results in a higher energy and more penetrating useful beam. State and federal laws dictate that dental x-ray machines operating at or below 70 kilovoltage (kV) require a minimum total (inherent plus added filtration) of 1.5 mm aluminum filtration, and machines operating above 70 kV require a minimum total of 2.5 mm aluminum filtration. WHAT DOES INHERENT PLUS ADDED FILTRATION EQUAL? TOTAL FILTRATION Collimation (the collimator) is used to restrict the size and shape of the x-ray beam and to reduce patient exposure. A collimator, or lead plate with a hole in the middle (sometimes referred to as a diaphragm), is fitted directly over the opening of the machine housing where the x-ray beam exits the tube head A rectangular collimator restricts the size of the x-ray beam to an area slightly larger than a size 2 intraoral receptor and considerably reduces patient exposure. A rectangular collimator exposes 60% less tissue than a circular collimator. A circular collimator produces a cone-shaped beam that is 2.75 inches in diameter, considerably larger than a size 2 intraoral receptor. Position-indicating Device (PID) A closed, plastic cone (conical) PID produces scatter radiation. When the x-rays exited the pointed cone, the beam penetrated the plastic and produced excess scatter radiation. To eliminate this cone-produced scatter radiation, the conical PID is no longer used in dentistry. The term cone, however, may still be used to refer to the PID. Both rectangular and circular PIDs are typically available in two lengths: short (8- inch) and long (16-inch). The PID aims and shapes the x-ray beam. The long PID is preferred because less divergence of the x-ray beam occurs, resulting in less scatter radiation. Like the rectangular collimator, the rectangular PID is most effective in reducing patient exposure. WHICH PID WOULD DECREASE PATIENT EXPOSURE THE MOST? 16” RECTANGULAR PID WHY? LESS TISSUE IS IRRADIATED AND LESS SCATTER RADIATION PRODUCED Patient protection measures are used during as well as before x-ray exposure. A thyroid collar, lead apron, digital sensors or fast film, and beam alignment devices are all used during x-ray exposure to limit the amount of radiation received by the patient. The thyroid collar is a flexible lead shield that is placed securely around the patient's neck to protect the thyroid gland from scatter radiation The use of the thyroid collar is recommended for all intraoral exposures. The lead apron is a flexible shield placed over the patient's chest and lap to protect the reproductive and blood-forming tissues from scatter radiation; the lead prevents the radiation from reaching these radiosensitive organs Use of a lead apron is recommended for both intraoral and extraoral exposures. Receptors Digital receptor Less radiation required Currently, F-speed film, or InSight, is the fastest intraoral film available and is recommended by the ADA. F-speed film provides an additional 20% reduction in exposure over E- speed films And 60% reduction in exposure from earlier D-speed film, or Ultra- Speed. Beam alignment devices are also effective in reducing a patient's exposure to x- radiation. Proper exposure factor selection can limit the amount of radiation that a patient receives Proper technique helps to create a diagnostic image and to reduce the amount of exposure a patient receives. After the receptors have been exposed, meticulous handling, proper processing techniques, and image retrieval are critical for the production of high-quality diagnostic images. Proper receptor handling is necessary to produce diagnostic images and to limit patient exposure to x-radiation. Proper film processing (developing) and proper retrieval of digital images are also necessary to produce diagnostic images and to limit patient exposure to x- radiation. WHAT IS THE FASTEST FILM CURRENTLY AVAILABLE? F-SPEED DOES PROPER IMAGE RETRIEVAL REDUCE PATIENT RADIATION EXPOSURE? YES The dental radiographer must avoid the primary beam. To avoid the primary beam, which travels in a straight line, the dental radiographer must position himself or herself perpendicular to the primary beam, or at a 90-degree to 135-degree angle to the beam The dental radiographer should leave the room or stand behind a barrier/wall. The dental radiographer should be at least 6 feet away from the x-ray tube head. NEVER hold the receptor in place for a patient. NEVER hold the tube head. WHAT IS THE MAIN THING THE DENTAL RADIOGRAPHER SHOULD AVOID? THE PRIMARY BEAM WHAT ANGLE SHOULD THE DENTAL RADIOGRAPHER STAND WHILE TAKING DENTAL IMAGES? 90-135 DEGREE ANGLE FROM THE PRIMARY BEAM Radiation monitoring can also be used to protect the dental radiographer and includes the monitoring of both equipment and personnel. Each radiographer should have his or her own badge; the badge should be worn at waist level whenever the dental radiographer is exposing x-ray films or digital sensors. Radiation legislation in the United States varies greatly from state to state, in some states, before a dental radiographer can expose patients to radiation, he or she must successfully complete a radiation safety examination. T/F: ONLY THE DENTAL PERSONNEL SHOULD BE MONITORED FOR RADATION EXPOSURE PROTECTION. FALSE, EQUIPMENT AND PERSONNEL SHOULD BE MONITORED WHERE SHOULD THE RADIATION BADGE BE WORN? AT THE WAIST The maximum permissible dose (MPD) is defined by the National Council on Radiation Protection and Measurements (NCRP) as the maximum dose equivalent that a body is permitted to receive within a specific period. This is the dose of radiation a body can endure with little to no injury. The most recent NCRP report states that the current MPD for occupationally exposed persons, or those who work with radiation (e.g., dental radiographers), is 50 mSv/year (0.05 Sv/year or 5.0 rem/year). It is recommended that dental radiographers not exceed a maximum dose of 50 mSv in any 1 year. For pregnant dental personnel, the radiation exposure limit is 0.5 mSv per month during the pregnancy months. WHAT DOES MPD STAND FOR? MAXIMUM PERMISSIBLE DOSE WHAT IS THE RADIATION EXPOSURE LIMIT FOR PREGNANT DENTAL PERONNEL? .5mSv/MO WHAT IS THE TOTAL AMOUNT OF RADIATION A PREGNANT DENTAL PROVIDER CAN HAVE IN HER PREGNANCY? 4.5mSv Occupationally exposed workers must not exceed an accumulated lifetime radiation dose. This is referred to as the cumulative occupational dose. the NCRP has recommended that an individual's cumulative occupational effective dose not exceed the worker's age multiplied by 10 mSv. Thus for a 50-year-old worker, the NCRP would recommend a cumulative occupational dose of no more than 50 × 10 mSv = 500 mSv (0.5 Sv). The ALARA (“as low as reasonably achievable”) concept states that all exposure to radiation must be kept to a minimum. Only take x-rays for diagnostic purposes Use lowest possible kV, mA, and exposure time Some x-ray machines can only have the exposure time adjusted. Use fastest film or digital Use long, rectangular PID Use tube head with aluminum filter and lead collimator Use lead apron and thyroid collar Use film-holding devices and avoid retakes Test equipment for efficiency and proper function WHAT IS THE CUMMULATIVE OCCUPATIONAL DOSE FOR A 20 YEAR OLD? 200mSv WHAT DOES ALARA STAND FOR? AS LOW AS REASONABLY ACHIEVABLE Chapter 12 – Dental Images and the Dental Radiographer The dental radiographer must understand the importance of dental images and the reasons why dental images are a necessary component of comprehensive patient care. A dental image is a two-dimensional representation of a three-dimensional object produced by the passage of x-rays through teeth and supporting structures. Dental images are a necessary component of comprehensive patient care. Images enable the dental professional to identify many conditions that may otherwise go undetected and to see many conditions that are not apparent clinically. An oral examination without dental images limits the dental practitioner's knowledge to what is seen clinically, that is, teeth and soft tissues. One of the most important uses of dental images is for detection of diseases, lesions, and conditions of the teeth and bones that cannot be identified by clinical examination alone. The primary benefit of dental images to the patient is detection of disease. When images are properly prescribed and exposed, their benefit far outweighs the risk of small doses of x-radiation Some of the more common diseases, lesions, and conditions found on dental images include the following: Missing teeth Extra teeth Impacted teeth Dental caries Periodontal disease Tooth abnormalities Retained roots Cysts and tumors Images can be used to educate the dental patient about some of these common conditions that are only detected through the use of dental images. The dental radiographer is any person who positions, exposes, and processes dental x- ray image receptors. In the typical dental practice, the dental radiographer is a dental auxiliary, either a dental hygienist or a dental assistant. The dentist can also be a dental radiographer. The dental radiographer must have sufficient knowledge and technical skills to perform dental imaging procedures and must have a thorough understanding of his or her responsibilities and professional goals. Assigned responsibilities in regard to dental imaging may include the following: Positioning and exposure of dental x-ray imaging receptors Processing of dental x-ray films Data retrieval of digital images Mounting and identification of dental images Education of patients about dental imaging Maintenance of darkroom and processing equipment Implementation and monitoring of quality control tests Ordering of dental x-ray equipment and related supplies Retakes resulting in unnecessary patient exposure to x-radiation must be avoided at all times. Operator protection must also be a primary concern for the dental radiographer. To avoid occupational exposure to x-radiation, the dental radiographer must always avoid the primary beam and maintain an adequate distance, proper position, and proper shielding from x-rays during the procedure. Patient education is another priority for the dental radiographer. The dental radiographer must play an active role in the education of patients concerning radiation exposure, patient protection, and the value and uses of dental images Operator competence must always be a concern of the dental radiographer, who must strive to maintain or improve professional competence by attending continuing education courses and lectures, studying professional books and journals, and reviewing and updating dental imaging techniques. Patients always appreciate the auxiliary who does not waste time and who works in a competent and efficient manner.