Foundations of Radiography Radiographic Equipment and Radiologic Safety

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Foundations of Radiography, Radiographic Equipment, and Radiologic Safety Chapter 38 Copyright © 2009, 2006

Foundations of Radiography, Radiographic Equipment, and Radiologic Safety Chapter 38 Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Chapter 38 Lesson 38. 1 Copyright © 2009, 2006 by Saunders, an imprint of

Chapter 38 Lesson 38. 1 Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Learning Objectives Pronounce, define, and spell the Key Terms. Describe the uses of dental

Learning Objectives Pronounce, define, and spell the Key Terms. Describe the uses of dental radiographs. Describe the discovery of x-radiation. Name the highlights in the history of dental radiography. Explain what happens during ionization. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Introduction The dental assistant must have a thorough knowledge and understanding of the importance

Introduction The dental assistant must have a thorough knowledge and understanding of the importance and uses of dental radiographs. The dental assistant must understand the fundamental concepts of atomic and molecular structure and have a working knowledge of ionizing radiation and the properties of x-rays. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Introduction (Cont’d) Radiation used to produce dental radiographs has the capacity to cause damage

Introduction (Cont’d) Radiation used to produce dental radiographs has the capacity to cause damage to all types of living tissues. Any exposure to radiation, no matter how small, has the potential to cause biologic changes to the operator and the patient. The dental assistant must have a thorough understanding of the characteristics of radiation to minimize radiation exposure to both the dental patient and the operator. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Discovery of Radiation Wilhelm Conrad Roentgen (pronounced rentken), a Bavarian physicist, discovered the xray

Discovery of Radiation Wilhelm Conrad Roentgen (pronounced rentken), a Bavarian physicist, discovered the xray on November 8, 1895. For many years x-rays were referred to as roentgen rays, radiology was referred to as roentgenology, and radiographs were known as roentgenographs. During his lifetime, Roentgen was awarded many honors and distinctions, including the first Nobel Prize ever awarded in physics, in 1901. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -1 A, Wilhelm Conrad Roentgen (1845– 1923), discoverer of x-rays. (Frommer HH,

Fig. 38 -1 A, Wilhelm Conrad Roentgen (1845– 1923), discoverer of x-rays. (Frommer HH, Stabulas-Savage J: Radiology for the dental professional, ed 8, St Louis, 2005, Mosby. ) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -1 B, Crookes tube, which Roentgen worked with at the time of

Fig. 38 -1 B, Crookes tube, which Roentgen worked with at the time of the discovery of x-rays in 1895. (Frommer HH, Stabulas-Savage J: Radiology for the dental professional, ed 8, St Louis, 2005, Mosby. ) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Pioneers in Dental Radiography Otto Walkoff made the first dental radiograph. Dr. C. Edmund

Pioneers in Dental Radiography Otto Walkoff made the first dental radiograph. Dr. C. Edmund Kells, a New Orleans dentist, is credited with the first practical use of radiographs in dentistry, in 1896. Dental radiography has progressed from these early discoveries to the science it is today. New technology continues to improve our diagnostic abilities. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Radiation Physics All things in this world are composed of energy and matter. Energy

Radiation Physics All things in this world are composed of energy and matter. Energy is defined as the capacity to do work. Matter is anything that occupies space and has form or shape. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Energy Although energy can neither be created nor destroyed, it can change form. Atoms

Energy Although energy can neither be created nor destroyed, it can change form. Atoms contain energy. The energy that holds the nucleus together is called nuclear-binding energy. The energy holding electrons, negatively charged particles, in their shells is known as electron-binding energy. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Matter Matter has many forms, including solids, liquids, and gases. Matter is composed of

Matter Matter has many forms, including solids, liquids, and gases. Matter is composed of atoms grouped together in specific arrangements called molecules. A molecule is the smallest particle of substance that retains the property of the original substance. The fundamental unit of matter for discussion in this chapter is the atom. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Atomic Structure The atom consists of two parts: Central nucleus Ø Orbiting electrons Ø

Atomic Structure The atom consists of two parts: Central nucleus Ø Orbiting electrons Ø An atom is identified by the composition of its nucleus and the arrangement of its orbiting electrons; at present, 105 different atoms are known to exist. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Atomic Structure (Cont’d) The arrangement within the atom is similar to that of the

Atomic Structure (Cont’d) The arrangement within the atom is similar to that of the solar system. The atom has a nucleus as its center or sun, and the electrons revolve (orbit) around it like planets. The electrons remain stable in their orbit unless disturbed or moved. Orbiting electrons can be disturbed by x-rays. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -3 Diagrammatic representation of an oxygen atom. Copyright © 2009, 2006 by

Fig. 38 -3 Diagrammatic representation of an oxygen atom. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Nucleus The nucleus, or dense core, of the atom is composed of particles known

Nucleus The nucleus, or dense core, of the atom is composed of particles known as protons and neutrons. Protons carry positive electrical charges; neutrons carry no electrical charge. Dental x-rays do not affect the tightly bound nucleus of the atom and are only changed in direction or scattered. Dental x-rays cannot make atoms radioactive; therefore patients do not give off x-rays after the x-ray machine stops producing x-rays. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Electrons are tiny negatively charged particles with very little mass. Electrons orbit around the

Electrons are tiny negatively charged particles with very little mass. Electrons orbit around the nucleus of an atom. The orbit path of an electron is called an electron shell. Each shell can contain only a specific number of electrons. The electrons are maintained in orbit by electron-binding energy, a force similar to the force of gravity on earth. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Ionization The electrons remain stable in their orbits around the nucleus until x-ray photons

Ionization The electrons remain stable in their orbits around the nucleus until x-ray photons collide with them. (A photon is a minute bundle of pure energy that has no weight or mass. ) X-rays have enough energy to push an electron out of its orbit, producing an ion (an atoms that gains or lose an electron and becomes electrically unbalanced) in a process called ionization. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Ionization (Cont’d) Ionization is the process by which electrons are removed from the orbital

Ionization (Cont’d) Ionization is the process by which electrons are removed from the orbital shells of electrically stable atoms through collisions with x-ray photons. When an electron is removed from the atom, an ion pair results. The harmful ionizing effect of x-rays in human beings can result in a disruption of cellular metabolism and can cause permanent damage to living cells and tissues. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -4 A molecule of water (H 2 O) consists of two atoms

Fig. 38 -4 A molecule of water (H 2 O) consists of two atoms of hydrogen connected to one atom of oxygen. (From Haring JI, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders. ) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Chapter 38 Lesson 38. 2 Copyright © 2009, 2006 by Saunders, an imprint of

Chapter 38 Lesson 38. 2 Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Learning Objectives Describe the properties of x-radiation. Label the parts of the dental x-ray

Learning Objectives Describe the properties of x-radiation. Label the parts of the dental x-ray tubehead and tube. Explain how radiographs are produced. Identify the range of kilovoltage and milliamperage required for dental radiography. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Learning Objectives (Cont’d) Describe the effect of the kilovoltage on the quality of the

Learning Objectives (Cont’d) Describe the effect of the kilovoltage on the quality of the x-ray beam. Describe how the milliamperage affects the quality of the x-ray beam. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Properties of X-Rays The dental assistant must be familiar with the unique characteristics of

Properties of X-Rays The dental assistant must be familiar with the unique characteristics of x-rays. X-rays are a form of energy that can penetrate matter. Like visible light, radar, radio, and television waves, they belong to a group called electromagnetic radiation. Electromagnetic radiation is made up of photons that travel through space at the speed of light in a straight line with a wavelike motion. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -6 Electromagnetic spectrum, showing the various wavelengths of radiation typically used. Copyright

Fig. 38 -6 Electromagnetic spectrum, showing the various wavelengths of radiation typically used. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Properties of X-Rays (Cont’d) The shorter the wavelength, the greater its energy. The high

Properties of X-Rays (Cont’d) The shorter the wavelength, the greater its energy. The high energy of short wavelengths means that they can penetrate matter more easily than longer wavelengths can. X-rays have unique properties that make them especially useful in dentistry. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -7 A, Wavelength is the distance between the crest (peak) of one

Fig. 38 -7 A, Wavelength is the distance between the crest (peak) of one wave and the crest of the next. B, The shorter the wavelength, the greater the energy and penetration, the longer the wavelength, the less energy and less penetration. (From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders. ) A B Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Components of the Dental X-Ray Machine Dental x-ray machines may vary somewhat in size

Components of the Dental X-Ray Machine Dental x-ray machines may vary somewhat in size and appearance, but all machines will have three primary components: The tubehead Ø An extension arm Ø The control panel Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -8 Dental x-ray machine and arm. A, Tubehead. B, Position-indicator device (PID).

Fig. 38 -8 Dental x-ray machine and arm. A, Tubehead. B, Position-indicator device (PID). C, Extension arm. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

The Tubehead The x-ray tubehead is tightly sealed; heavy metal housing contains the x-ray

The Tubehead The x-ray tubehead is tightly sealed; heavy metal housing contains the x-ray tube that produces dental x-rays. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -9 Diagram of the dental x-ray tubehead. (From Haring J, Jansen L:

Fig. 38 -9 Diagram of the dental x-ray tubehead. (From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders. ) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -10 X-ray tube. (Courtesy of Xintek Inc. ) Copyright © 2009, 2006

Fig. 38 -10 X-ray tube. (Courtesy of Xintek Inc. ) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Components of the Tubehead The metal body of the tubehead that houses the x-ray

Components of the Tubehead The metal body of the tubehead that houses the x-ray tube is called the metal housing. It is filled with insulating oil. Insulating oil surrounds the x-ray tube and prevents overheating by absorbing the heat created in the production of x-rays. Tubehead seal is made of leaded glass or aluminum. It seals the oil in the tubehead. The x-ray tube is the heart of the x-ray– generating unit. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Components of the Tubehead (Cont’d) The transformer alters the voltage of incoming electric current.

Components of the Tubehead (Cont’d) The transformer alters the voltage of incoming electric current. The aluminum filter is aluminum sheets 0. 5 mm thick. The lead collimator is a metal disc with a small opening in the center to control the size and shape of the x-ray beam as it leaves the tubehead. The PID is the open-ended, lead-lined cylinder that extends from the opening of the metal housing of the tubehead. It is used to aim the x-ray beam. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

The X-Ray Tube The vacuum environment allows the electrons to flow with minimum resistance

The X-Ray Tube The vacuum environment allows the electrons to flow with minimum resistance between the electrodes: Cathode Ø Anode Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

The Cathode The cathode consists of a tungsten filament in a focusing cup made

The Cathode The cathode consists of a tungsten filament in a focusing cup made of molybdenum. The purpose of the cathode is to supply the electrons necessary to generate x-rays. Electrons are generated in the x-ray tube at the cathode. The hotter the filament becomes, the more electrons are produced. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

The Anode The anode is the target for the electrons. It is composed of

The Anode The anode is the target for the electrons. It is composed of a tungsten target (a small block of tungsten) that is embedded in the larger copper stem. The copper around the target conducts heat away from the target, reducing wear and tear on the target. The purpose of the tungsten target is to serve as a focal spot and convert the bombarding electrons into x-ray photons. The x-rays at the center of this beam are known as the central ray. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -16 The production of dental x-rays occurs in the x-ray tube. (From

Fig. 38 -16 The production of dental x-rays occurs in the x-ray tube. (From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders. ) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

The PID The open end of the lead-lined PID is placed against the patient’s

The PID The open end of the lead-lined PID is placed against the patient’s face during film exposure. The PID may be cylindrical or rectangular. The rectangular PID limits the size of the beam to that of a dental film. PIDs used in dentistry are usually 8, 12, or 16 inches long. The choice of length is determined by the radiographic technique being used. The long (12 - to 16 -inch) PID is more effective in reducing exposure to the patient than a short (8 -inch) PID because there is less divergence (separation) of the beam. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

The Extension Arm The extension arm encloses the wire between the tubehead and the

The Extension Arm The extension arm encloses the wire between the tubehead and the control panel. It also has an important function in positioning the tubehead. The extension arm folds up and can be swiveled from side to side. If the extension arm is left in an extended position when the machine is not in use, the weight of the tubehead can cause it to become loose, and the tubehead will drift (slip out of position) after it is positioned for an exposure. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

The Control Panel The control panel of an x-ray unit contains: The master switch

The Control Panel The control panel of an x-ray unit contains: The master switch Ø Indicator light Ø Exposure button Ø Indicator light Ø Control devices (time, milliamperage [m. A] selector, and kilovoltage [k. Vp] selector) Ø A single centrally located control panel may be used to operate several tubeheads located in separate treatment rooms. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

How X-Rays Are Produced The x-ray machine is plugged into the wall outlet, and

How X-Rays Are Produced The x-ray machine is plugged into the wall outlet, and when the machine is turned on the electric current enters the control panel. The current travels from the control panel to the tubehead through electrical wires in the extension arm. The current travels through the step-down transformer to the filament of the cathode. The filament circuit uses 3 to 5 V to heat the tungsten filament in the cathode portion of the x-ray tube. The heating of the filament results in thermionic emission. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

How X-Rays Are Produced (Cont’d) When the exposure button is pushed, the highvoltage circuit

How X-Rays Are Produced (Cont’d) When the exposure button is pushed, the highvoltage circuit is activated. The electrons in the cloud are accelerated across the x-ray tube to the anode. The molybdenum cup in the cathode directs the electrons to the tungsten target in the anode. The electrons travel from the cathode to the anode. When the electrons strike the tungsten target, their energy of motion (kinetic energy) is converted to x-ray energy and heat. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

How X-Rays Are Produced (Cont’d) Less than 1% of the energy is converted to

How X-Rays Are Produced (Cont’d) Less than 1% of the energy is converted to x-rays; the remaining 99% is lost as heat. The heat is carried away from the copper stem and absorbed by the insulating oil in the tubehead. The x-rays travel through the unleaded glass window, the tubehead seal, and the aluminum filter. The aluminum filter removes the longer-wavelength xrays. The x-ray beam travels through the collimator. The x-ray beam then travels down the lead-lined PID and exits at the end of the PID. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Types of Radiation Primary radiation is the x-rays that come from the target of

Types of Radiation Primary radiation is the x-rays that come from the target of the x-ray tube. Secondary radiation is x-radiation that is created when the primary beam interacts with matter. Scatter is a form of secondary radiation. It results when an x-ray beam has been deflected from its path by interaction with matter. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -17 Types of radiation interaction with the patient. 1, Primary. 2, Secondary.

Fig. 38 -17 Types of radiation interaction with the patient. 1, Primary. 2, Secondary. 3, Scatter. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Visual Characteristics Three qualities are necessary for a good radiograph: Contrast Ø Density Ø

Visual Characteristics Three qualities are necessary for a good radiograph: Contrast Ø Density Ø Image detail Ø The dental assistant must understand how variations in the character of the x-ray beam influence the quality of the resulting radiographs. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Radiolucency and Radiopacity Radiolucent structures allow x-rays to pass through them. Radiolucent structures appears

Radiolucency and Radiopacity Radiolucent structures allow x-rays to pass through them. Radiolucent structures appears dark or black on the radiograph. Air spaces, soft tissues of the body, and the dental pulp appear as radiolucent images. Radiopaque structures do not allow x-rays to pass through them. Radiopaque structures appear white or light gray on the radiograph. Metal, enamel, and dense areas of bone appear as radiopaque images. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -18 Bite-wing radiograph showing a radiopaque (white, a) area of amalgam restoration

Fig. 38 -18 Bite-wing radiograph showing a radiopaque (white, a) area of amalgam restoration and radiolucent (black, b) area of air and cheek tissue. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Contrast The ideal contrast of a film clearly shows the radiopaque white of a

Contrast The ideal contrast of a film clearly shows the radiopaque white of a metal restoration, the radiolucent black of air, and the many shades of gray between. Higher kilovoltage produces more penetrating x-rays and lower radiographic contrast. A 90 -k. Vp setting requires less exposure time and produces a radiograph that has low contrast (more shades of gray). A 70 -k. Vp setting requires a slightly longer exposure time and produces a radiograph with high contrast (fewer shades of gray). Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -19 A, A radiograph produced with lower kilovoltage exhibits high contrast. Many

Fig. 38 -19 A, A radiograph produced with lower kilovoltage exhibits high contrast. Many light and dark areas are seen. (From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders. ) A Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -19 B, A radiograph produced with higher kilovoltage exhibits low contrast. Many

Fig. 38 -19 B, A radiograph produced with higher kilovoltage exhibits low contrast. Many shades of gray are seen instead of black and white. (From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders. ) B Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Density Density is the overall blackness or darkness of a film. A radiograph with

Density Density is the overall blackness or darkness of a film. A radiograph with the correct density enables the dentist to view black areas (air spaces), white areas (enamel, dentin, and bone), and gray areas (soft tissues). The degree of density is determined by the milliampere seconds (m. As). Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Other Factors Influencing Density The distance from the x-ray tube to the patient: If

Other Factors Influencing Density The distance from the x-ray tube to the patient: If the operator lengthens the source-film distance without changing the exposure settings, the resulting radiographs will be light or less dense. The developing time and temperature can affect the overall density. If the processing time is too long, the radiograph will appear dark. The body size of the patient: A patient who is very small or thin requires less radiation than a husky, heavy-boned person. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Geometric Characteristics Three geometric characteristics affect the quality of the radiograph: Sharpness Ø Magnification

Geometric Characteristics Three geometric characteristics affect the quality of the radiograph: Sharpness Ø Magnification Ø Distortion Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Sharpness Sharpness refers to how well the radiograph reproduces the fine details or distinct

Sharpness Sharpness refers to how well the radiograph reproduces the fine details or distinct outlines of an object. Sharpness is sometimes referred to as detail, resolution, or definition. The sharpness of an image is influenced by three : Focal-spot size Ø Film composition Ø Movement Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Chapter 38 Lesson 38. 3 Copyright © 2009, 2006 by Saunders, an imprint of

Chapter 38 Lesson 38. 3 Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Learning Objectives Discuss the effects of radiation exposure on the human body. Identify the

Learning Objectives Discuss the effects of radiation exposure on the human body. Identify the critical organs that are sensitive to radiation. Discuss the risks and benefits of dental radiographs. Describe the methods of protecting the patient from excess radiation. Describe the measures used to protect the operator from excess radiation. Discuss the ALARA concept. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Radiation Safety All ionizing radiations are harmful and produce biologic changes in living tissues.

Radiation Safety All ionizing radiations are harmful and produce biologic changes in living tissues. The amount of x-radiation used in dental radiography is small, but biologic changes do occur. The dental assistant must understand how the harmful effects of radiation occur and how to discuss the risks of radiation with patients. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Ionization Ionization is the harmful effect of x-rays in human beings that can result

Ionization Ionization is the harmful effect of x-rays in human beings that can result in a disruption of cellular metabolism and cause permanent damage to living cells and tissues. Ionization is the process by which electrons are removed from electrically stable atoms through collisions with x-ray photons. The atoms that lose electrons become positive ions; as such, they are unstable and capable of interacting with (and damaging) other atoms, tissues, or chemicals. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Biologic Effects of Radiation Exposure to radiation can bring about changes in body chemicals,

Biologic Effects of Radiation Exposure to radiation can bring about changes in body chemicals, cells, tissues, and organs. The effects of the radiation may not become evident for many years after the x-rays were absorbed. This time lag is called the latent period. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Cumulative Effects Exposure to radiation has a cumulative effect over a lifetime. When tissues

Cumulative Effects Exposure to radiation has a cumulative effect over a lifetime. When tissues are exposed to x-rays, some damage occurs. Tissues have the capacity to repair some of the damage; however, they do not return to their original state. The cumulative effect of radiation exposure can be compared with cumulative effect from repeated exposure over the years to the rays of the sun. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Acute and Chronic Radiation Exposure Acute radiation exposure occurs when a large dose of

Acute and Chronic Radiation Exposure Acute radiation exposure occurs when a large dose of radiation is absorbed in a short period, such as in a nuclear accident. Chronic radiation exposure occurs when small amounts of radiation are absorbed repeatedly over a long period. It may be years after the original exposure before the effects of chronic radiation exposure are observed. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Genetic and Somatic Effects X-rays affect both genetic and somatic cells. Genetic cells are

Genetic and Somatic Effects X-rays affect both genetic and somatic cells. Genetic cells are the reproductive cells (sperm and ova). Damage to genetic cells is passed on to succeeding generations. These changes are referred to as genetic mutations. All other cells in the body belong to the classification of somatic tissue. (Somatic means “referring to the body. ”) X-rays can damage somatic tissue, but the damage is not passed on to future generations. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -21 Comparison of somatic and genetic effects of radiation. (From Haring J,

Fig. 38 -21 Comparison of somatic and genetic effects of radiation. (From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders. ) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Critical Organs Certain organs are considered critical: Skin Ø Thyroid gland Ø Lens of

Critical Organs Certain organs are considered critical: Skin Ø Thyroid gland Ø Lens of the eye Ø Bone marrow Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Radiation Measurements Radiation can be measured in a manner similar to that used to

Radiation Measurements Radiation can be measured in a manner similar to that used to measure time, distance, and weight. Two sets of systems are used to define the way in which radiation is measured. The older system is referred to as the traditional or standard system. The newer system is the metric equivalent, known as the Système Internationale, or SI. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Traditional Units of Radiation Measurement The roentgen (R) The radiation absorbed dose (rad) Ø

Traditional Units of Radiation Measurement The roentgen (R) The radiation absorbed dose (rad) Ø The roentgen equivalent [in] man (rem) Ø SI units Coulombs per kilogram (C/kg) Ø Gray (Gy) Ø Sievert (Sv) Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Maximum Permissible Dose The maximum permissible dose (MPD) of whole-body radiation for those who

Maximum Permissible Dose The maximum permissible dose (MPD) of whole-body radiation for those who are occupationally exposed to radiation is 5000 mrem (5. 0 rem) per year, or 100 mrem per week. This amount of radiation to the whole body carries very little chance of injury. For nonoccupationally exposed persons, the current MPD is 500 mrem (5 m. Sv) per year. Dental personnel should strive for an occupational dose of 0 by adhering to strict radiation-protection practices. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Radiation Risks and Benefits Background radiation comes from natural sources such as radioactive materials

Radiation Risks and Benefits Background radiation comes from natural sources such as radioactive materials in the ground and cosmic radiation from space. Exposure from medical or dental sources is an additional radiation risk. When dental radiographs are prescribed and exposed, the benefit of disease detection far outweighs the risk of biologic damage from receiving small doses of radiation. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Responsibilities of the Dentist To prescribe radiographs only for diagnostic purposes. To ensure that

Responsibilities of the Dentist To prescribe radiographs only for diagnostic purposes. To ensure that all radiographic equipment is properly installed and maintained in a safe working condition. To provide appropriate shielding to protect staff and patients from the effects of radiation. To require that anyone exposing radiographs be properly trained and appropriately supervised while exposing radiographs. To obey all state radiographic licensing requirements, rules, and regulations. To participate in obtaining informed consent. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Equipment for Radiation Protection The dental tubehead must be equipped with certain appropriate components:

Equipment for Radiation Protection The dental tubehead must be equipped with certain appropriate components: Aluminium filters Ø Lead collimators Ø PIDs Ø Equipment should be checked on a regular basis by state or federal regulating agencies. Faulty or malfunctioning equipment should be repaired immediately. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Aluminum Filter The purpose of the aluminum filter is to remove the low-energy, long-wavelength,

Aluminum Filter The purpose of the aluminum filter is to remove the low-energy, long-wavelength, and least penetrating x-rays from the x-ray beam. These x-rays are harmful to the patient and are not useful in producing a diagnosticquality radiograph. X-ray machines operating at 70 k. Vp or higher must have aluminum filtration of 2. 5 mm. This is a federal requirement. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Collimator The collimator is used to restrict the size and shape of the x-ray

Collimator The collimator is used to restrict the size and shape of the x-ray beam as a means of reducing patient exposure. A collimator may have either a round or rectangular opening. A rectangular collimator restricts the beam to an area slightly larger than a size 2 intraoral film and significantly reduces patient exposure. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

The PID appears as an extension of the x-ray tubehead. It is used to

The PID appears as an extension of the x-ray tubehead. It is used to direct the x-ray beam. Round and rectangular PIDs are available in two lengths: Short (8 -inch) Ø Long (16 -inch) Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Patient Protection Lead apron and thyroid collar: A lead apron and thyroid collar must

Patient Protection Lead apron and thyroid collar: A lead apron and thyroid collar must be used on all patients for all exposures. Ø This rule applies to all patients, regardless of the patient’s age or sex or the number of films being exposed. Ø The lead apron should cover the patient from the neck to the lap to protect the reproductive and blood-forming tissues from scatter radiation. Many states mandate the use of a lead apron. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -23 The lead apron and thyroid collar must be large enough to

Fig. 38 -23 The lead apron and thyroid collar must be large enough to cover the seated patient from the neck to above the knees. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fast-Speed Film The size of silver bromide crystals is the main factor in determining

Fast-Speed Film The size of silver bromide crystals is the main factor in determining the film speed: the larger the crystals, the faster the film. A fast film requires less exposure to produce a quality radiograph. Fast-speed film is the single most effective method of reducing a patient’s exposure to x-radiation. Fast-speed film is available for both intraoral and extraoral radiography. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Film-Holding Devices The use of a film-holding instrument keeps the patient’s hands and fingers

Film-Holding Devices The use of a film-holding instrument keeps the patient’s hands and fingers from being exposed to x-radiation. The film holder also keeps the film in a stable position and helps the operator proper position the film and the PID. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -24 The patient’s fingers are unnecessarily exposed to radiation when film holders

Fig. 38 -24 The patient’s fingers are unnecessarily exposed to radiation when film holders are not used. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Exposure Factors Using the proper exposure factors also limits the amount of x-radiation the

Exposure Factors Using the proper exposure factors also limits the amount of x-radiation the patient is exposed to. Adjusting the kilovoltage peak, milliamperage, and time settings controls the exposure factors. A setting of 70 to 90 k. Vp keeps patient exposure to a minimum. On some dental units, the kilovoltage peak and milliamperage settings are preset by the manufacturer and cannot be adjusted. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Proper Technique Proper technique is necessary to ensure the diagnostic quality of films and

Proper Technique Proper technique is necessary to ensure the diagnostic quality of films and reduce the amount of radiation to which the patient is exposed. Films that are nondiagnostic must be retaken; this results in additional radiation exposure to the patient. Retakes are a major cause of unnecessary radiation exposure in patients and must be avoided. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

X-Rays During Pregnancy The Guidelines for Prescribing Dental Radiographs, issued by the American Dental

X-Rays During Pregnancy The Guidelines for Prescribing Dental Radiographs, issued by the American Dental Association in conjunction with the Food and Drug Administration, state that dental radiographic procedures “do not need to be altered because of pregnancy. ” When a lead apron is used during dental radiographic procedures, the amount of radiation received in the pelvic region is nearly zero. There is no detectable exposure to the embryo or fetus with the use of a lead apron. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Operator Protection A dental assistant who fails to follow the rules of radiation protection

Operator Protection A dental assistant who fails to follow the rules of radiation protection may suffer the results of chronic radiation exposure. By following these rules, dental personnel can keep their radiation exposure to zero. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Rules for Operator Protection Never stand in the direct line of the primary beam.

Rules for Operator Protection Never stand in the direct line of the primary beam. Always stand behind a lead barrier, if one is available, or the proper thickness of drywall. If a lead barrier is not available, stand at right angles to the beam. Never stand closer than 6 feet to the x-ray unit during an exposure unless you are behind a barrier. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -25 For the sake of safety, the dental assistant must stand out

Fig. 38 -25 For the sake of safety, the dental assistant must stand out of the path of the primary beam. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Personnel Monitoring Three types of monitoring devices are used to determine the amount of

Personnel Monitoring Three types of monitoring devices are used to determine the amount of radiation exposure to personnel: Film badge Ø Pocket dosimeter (pen style) Ø Thermoluminescent, or TLD Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -26 A film badge is used to monitor the amount of radiation

Fig. 38 -26 A film badge is used to monitor the amount of radiation that reaches the dental radiographer. (Courtesy of Global Dosimetry Solutions, Irvine, Calif. ) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Equipment Monitoring Dental x-ray machines must be monitored for radiation leakage. If a dental

Equipment Monitoring Dental x-ray machines must be monitored for radiation leakage. If a dental x-ray tubehead has a faulty tubehead seal, leakage results. Dental x-ray equipment can be monitored through the use of a film device that can be obtained from the manufacturer or from the state health department. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

If the Patient Cannot Cooperate If the patient is a child who is unable

If the Patient Cannot Cooperate If the patient is a child who is unable to cooperate, he or she is seated on the parent’s lap in the dental chair. Both the parent and child are covered with the lead apron, and the parent holds the film in place. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 38 -27 Child sitting on parent’s lap for dental x-ray. Copyright © 2009,

Fig. 38 -27 Child sitting on parent’s lap for dental x-ray. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

ALARA Concept The ALARA concept states that all exposure to radiation must be kept

ALARA Concept The ALARA concept states that all exposure to radiation must be kept to a minimum, or “as low as reasonably achievable. ” Every possible method of reducing exposure to radiation should be used to minimize risk. The radiation-protection measures detailed in this chapter should be used to minimize patient, operator, and staff exposure, keeping radiation exposure “as low as reasonably achievable. ” Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Patient Questions Patients often have questions and concerns about radiation. As a dental assistant.

Patient Questions Patients often have questions and concerns about radiation. As a dental assistant. you must be prepared to answer such questions and educate the dental patient about the importance of radiographs. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Patient Questions (Cont’d) Here are some examples of comments you can make to patients

Patient Questions (Cont’d) Here are some examples of comments you can make to patients during informal discussions: Ø Ø Ø “The doctor orders x-rays on the basis of your individual needs. ” “Our office takes every step possible to protect you from unnecessary radiation. ” “We use a lead apron and thyroid collar to protect your body from stray radiation. ” “We use a high-speed film that requires only minimal amounts of radiation. ” “Do you have any questions before we begin? ” Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.