Radiology Lecture 1.docx

Lecture 1 Chapter 1 – Radiation History The purpose of this chapter is to introduce basic dental imaging terms, to detail the importance of dental images, and to review the history of x-radiation. Radiation: A form of energy carried by waves or a stream of particles X-radiation: A high-energy...

Lecture 1 Chapter 1 – Radiation History The purpose of this chapter is to introduce basic dental imaging terms, to detail the importance of dental images, and to review the history of x-radiation. Radiation: A form of energy carried by waves or a stream of particles X-radiation: A high-energy radiation produced by the collision of a beam of electrons with a metal target in an x-ray tube X-ray: A beam of energy that has the power to penetrate substances and record image shadows on receptors (photographic film or digital sensors) Radiology: The science or study of radiation as used in medicine; a branch of medical science that deals with the therapeutic use of x-rays, radioactive substances, and other forms of radiant energy Radiograph: An image or picture produced on a receptor (radiation-sensitive film, phosphor plate, or digital sensor) by exposure to ionizing radiation; a two-dimensional representation of a three-dimensional object Image receptor: A recording medium; examples include x-ray film, phosphor plate, or digital sensor Dental images are a necessary component of comprehensive patient care. Dental images enable the dental professional to identify many conditions that may otherwise go undetected and to see conditions that cannot be identified clinically. An oral examination without dental images limits the dental practitioner to what is seen clinically—the teeth and soft tissue. With the use of dental images, the dental radiographer can obtain a wealth of information about the teeth and supporting bone. Detection is one of the most important uses of dental images. Through the use of dental images, the dental radiographer can detect disease. Many dental diseases and conditions produce no clinical signs or symptoms and are typically discovered only through the use of dental imaging. *Great answer if a patient asks why they need x-rays.* The history of dental radiography begins with the discovery of the x-ray. Wilhelm Conrad Roentgen (pronounced “ren-ken”), a Bavarian physicist, discovered the x- ray on November 8, 1895. This monumental discovery revolutionized the diagnostic capabilities of the medical and dental professions and, as a result, forever changed the practice of medicine and dentistry. Before the discovery of the x-ray, Roentgen had experimented with the production of cathode rays (streams of electrons). He used a vacuum tube, an electrical current, and special screen covered with a material that glowed (fluoresced) when exposed to radiation. He made the following observations about cathode rays: The rays appeared as streams of colored light passing from one end of the tube to the other. The rays did not travel far outside the tube. The rays caused fluorescent screens to glow. Roentgen named his discovery x-rays, the “x” referring to the unknown nature and properties of such rays. (The symbol x is used in mathematics to represent the unknown.) He published a total of three scientific papers detailing the discovery, properties, and characteristics of x-rays. During his lifetime, Roentgen was awarded many honors and distinctions, including the first Nobel Prize ever awarded in physics. *1901* For many years after his discovery, x-rays were referred to as “roentgen rays,” radiology was referred to as “roentgenology,” and radiographs were known as “roentgenographs.” The primitive vacuum tube used by Roentgen in the discovery of x-rays represented the collective findings of many investigators. Before the discovery of x-rays in 1895, a number of European scientists had experimented with fluorescence in sealed glass tubes. In 1838, a German glassblower named Heinrich Geissler built the first vacuum tube, a sealed glass tube from which most of the air had been evacuated. This original vacuum tube, known as the Geissler tube, was modified by a number of investigators and became known by their respective names. Johann Wilhelm Hittorf, a German physicist, used the vacuum tube to study fluorescence (a glow that results when a fluorescent substance is struck by light, cathode rays, or x-rays). In 1870 he observed that the discharges emitted from the negative electrode of the tube traveled in straight lines, produced heat, and resulted in a greenish fluorescence. He called these discharges cathode rays. In 1894, Philip Lenard discovered that cathode rays could penetrate a thin window of aluminum foil built into the walls of the glass tubes and cause fluorescent screens to glow. He noticed that when the tube and screens were separated by at least 3.2 inches (8 cm), the screens would not fluoresce. Shortly after the announcement of the discovery of x-rays in 1895, a German dentist, Otto Walkhoff, made the first dental radiograph. He placed a glass photographic plate wrapped in black paper and rubber in his mouth and submitted himself to 25 minutes of x-ray exposure. In that same year, (1895) W. J. Morton, a New York physician, made the first dental radiograph in the United States using a skull. C. Edmund Kells, a New Orleans dentist, is credited with the first practical use of radiographs in dentistry in 1896. Kells exposed the first dental radiograph in the United States using a living person. During his many experiments, Kells exposed his hands to numerous x-rays every day for years. This overexposure to x-radiation caused the development of numerous cancers in his hands. Kells’ dedication to the development of x-rays in dentistry ultimately cost him his fingers, later his hands, and then his arms. William H. Rollins, a Boston dentist who developed the first dental x-ray unit. While experimenting with radiation, Rollins suffered a burn to his hand. This initiated an interest in radiation protection and later the publication of the first paper on the dangers associated with radiation. From 1896 to 1913, dental x-ray packets consisted of glass photographic plates or film cut into small pieces and hand-wrapped in black paper and rubber. The hand wrapping of intraoral dental x-ray packets was a time-consuming procedure. In 1913 the Eastman Kodak Company manufactured the first prewrapped intraoral films and consequently increased the acceptance and use of x-rays in dentistry. The first machine-made periapical film packets became available in 1920. The films currently used in dental radiography are greatly improved compared with the films of the past. At present, fast film requires a very short exposure time, less than 2% of the initial exposure times used in 1920, which, in turn, reduces the patient’s exposure to radiation. Early years of film, only one side had emulsion coating and required long exposure times As film improved, both sides were coated with emulsion Allowed for much shorter exposure times F. Gordon Fitzgerald, the “father of modern dental radiography,” revived interest in the paralleling technique with the introduction of the long-cone paralleling technique in 1947. The extraoral technique used most often in dentistry is panoramic radiography. Digital imaging allows for instant and easy transmission of images and electronic storage. The capability to reduce patient exposure to radiation while increasing diagnostic potential has profound implications. In 1987, the technology that is used to support dental digital imaging was introduced in France when the first intraoral imaging sensor was introduced. The digital sensor replaced film and required even less radiation exposure! Chapter 7 – Dental X-ray Equipment Before 1974, no federal standards existed for the manufacture of dental x-ray machines. All dental x-ray machines manufactured after 1974 must, however, meet specific federal guidelines regulating diagnostic equipment performance standards. The federal government regulates the manufacture and installation of dental x-ray equipment. State and local governments regulate how dental x-ray equipment is used and dictate codes that pertain to the use of x-radiation. Depending on state and local radiation safety codes, dental x-ray equipment must be registered, inspected, and monitored periodically. A fee is typically charged for such services. A variety of intraoral and extraoral dental x-ray machines is available for diagnostic purposes. Dental x-ray machines vary in both design and operation. Some machines are used only for intraoral exposures. Others are limited to extraoral exposures. State-of-the-art x-ray machines produce a wide variety of imaging types. Some intraoral units are portable and allow for exposures outside of the dental office in sites such as nursing homes and mobile clinics. Handheld x-ray units are approved in many, but not all, states. Each individual state radiation control board determines the use and protection requirements for such units. The typical intraoral dental x-ray machine features three component parts: (1) tubehead, (2) extension arm, and (3) control panel. The tubehead, or tube housing, contains the x-ray tube that produces dental x-rays. Extending from the tubehead opening is the position-indicating device (PID), or cone. The PID may be round or rectangular in shape and restricts the size of the x-ray beam. The extension arm suspends the x-ray tubehead, houses the electrical wires, and allows for movement and positioning of the tubehead. The control panel, which allows the dental radiographer to regulate the x-ray beam, is plugged into an electrical outlet and appears as a console or cabinet. The control panel consists of (1) an on-off switch and indicator light, (2) an exposure button and exposure light, (3) a control device for time, and (4) with some units, control devices for kilovoltage and milliamperage. The on-off switch must be placed in the “on” position to operate the dental x-ray equipment. An indicator light is illuminated when the equipment is turned on. The exposure button activates the machine to produce x-rays. The dental radiographer must firmly depress the exposure button until the preset exposure time is completed. As a visible sign that x-rays are being produced, an exposure light on the control panel is illuminated during x-ray exposure. In addition, a beep sounds during x-ray exposure as an audible signal that x-rays are being produced. The exposure light turns off and the beep stops when the x-ray exposure is completed. The control devices that regulate the x-ray beam include the timer and the kilovoltage (kV) and milliamperage (mA) selectors. The timer determines the length of exposure time in seconds. Common extraoral imaging techniques used in dentistry include the panoramic, cephalometric, skull imaging, and cone-beam computer tomography. The main components of an extraoral x-ray machine consist of the tubehead; positioning devices for the lateral head, chin, forehead, and anterior teeth; and an exposure control panel. The PID may be round or rectangular, as seen in intraoral imaging machines. Most often, the x-ray tubehead is mounted on one side of the machine, where the sensor or detector is located on the opposite side. Stabilizing devices for the head, chin, and sides of the face are not only important in positioning the patient correctly, but also aid in keeping the patient still during exposure time. A bite-block may also be required to keep the anterior teeth separated for ease of viewing anatomic structures. A receptor holder is a device used to hold and align intraoral dental x-ray receptors in the mouth. The simplest holder is a disposable Styrofoam bite-block with a backing plate and a slot for receptor retention; examples include XCP Bite-Block and Stabe Bite-Block (Rinn Corporation). Receptor holders eliminate the need for the patient to stabilize the receptor. With certain intraoral techniques (e.g., paralleling technique), the use of a receptor-holding device is required. Molded-plastic devices that can be sterilized are also available, including the Snap-A-Ray, formerly named EEZEE-Grip, which is a double-ended instrument that holds the receptor between two serrated plastic grips that can be locked in place. A beam alignment device is used to help the dental radiographer position the PID in relation to the tooth and the receptor. EX: RINN XCP Beam alignment devices, which are available from a number of manufacturers, are used to indicate the PID position in relation to the tooth and receptor. The XCP and BAI beam alignment devices (Rinn) feature plastic bite-blocks, plastic aiming rings, and metal indicator arms. These devices are available with bite-blocks designed to hold traditional film or digital sensors. For use in conjunction with a beam alignment device, a collimating device may be retrofitted onto the end of a standard PID to restrict the size of the x-ray beam and limit radiation exposure. Examples of such devices include the IDI Tru-Image™ x-ray positioning system and the Rinn Universal collimator.