Radiography Flashcards
Introduction to Radiography
dentist relies on dental asssistant to capture a radiographic image as accurately as possible to help proper diagnosis.
Dental assistant must understand the fundamental concepts of atomic and molecular structure and have a working knowlege of ionizing radiation and properties of x-ray. Hoe atomic structure of cells is changed by radiation.
Discovery pf Radiation
Whihelm conrad Roentgen (rent-ken) a bavarian physicist, disovered x-radiation on novermber 8, 1895.
Fist enent was recoreded as first radiography of human body is when Roentgen placed his wife’s hand on photographic plate and exposed her to the ray for15 min and image of outline of her bones.
Sir willian crookes and Johann Hittorf redesgned the early cathode tube in 1870.
For many times x-ray was referred to as roentgen rays; radiology was refereed roentgenology; radiographs were know as roentgenographs.
pioneer in dental radiography
two pioneer are credited with applying the new x-ray technology to the practice of dentistry.
-otto walkoff made the first dental radiograph by exposing a photographic plate in his own mouth for 25 min.
- Dr. C. Edmund kells a new orleans dentist is credited the first practical use of radiographs in dentistry in 1896. Dr kells lost fingers, hands result of cancerous tumor of exposing to x-ray.
Digital technology began to enter dental offices in 1987. Many parctices today use digital technology instead of conventional radiography becuase it offers new conveniences and use exposure that are 50-80% less than conventional film
Atomic structure
consists of two parts. Each atom has a nucleus as its center of electrons that revolve orbit around it. 105 diff atoms that knowns to exist.
nucleus composed of particles know as protons and neutrons
Electrons are (-) changed particles. The orbit path of an electron is called an electron shell.
outer layer of electrons can be disrupted during dental radiography. The nucleus of atom is not affected by x-ray. it can only change direction. dental x-rays cannot make atoms radioactive.
Ionization
electrons remain stables in their orbits around the nucleus until x-ray phons collide with them. X-ray have enough energy to push an electron out of its orbit, producing ion in a process called ionization.
Ion (gain or loses) an electron and becomes electrically unbalanced.
Ionization: process by which electrons are removed from the orbital shells of electrically stables atoms through collisions with x-ray photons.
The harmful ionizing effect of x-rays in human begins can result in a disruption of cellular metabolism and cause permanent damage to living cells and tissues
Properties of X-rays
X-rays have unique properties that make them especially used in dentistry.
Electromagnetic radiation: made up of photos that travel through space at the speed of light in a straight line with a wave like motions.
Wavelengh is distance between the peaks o fthe wave and the crest of the nest. the shorter wavelenght the greater its energy.
Components of dental dental x-ray machine
-Tube Head: consists of tightly sealed, metal housing that contains the x-ray tube that produced dental x-ray. Metal housing is filled with insulating oil that surround the x-ray tube. The oil prevents overheating by obsorbing the heat created in the production of x-ray.
-Extension: arm also knows as the yoke. important function in positioning the tube head.
-Control Panel: mater switch, indicator light , exposure button.
The Tube Head
The x-ray tube is heart if r-ray. contains the cathode with filament circuits with generates electrons directed to anode.
The position indicating device (PID) is open lead lined cylinder that extends from the opening of the metal housing of the tube head. short and long. aim the x-ray beam
How x rays are produced
- x-ray machine is pulgged into wall outlet.
- The machine is tuned on, allowing electric current to enter the control panel.
- current travels from the control through electrical wires in extension arm to tube head.
- The current travels through the step down transformer to the filament of the cathode.
-Filament circuit uses three to five volts (v) to heat the tungsten filament in the cathode portion of the x-ray tube.
-The heating of the filament results in the thermionic emissionl.
How x rays are produced cont
-The electrons in the cloud are accelerated across the r-ray tube to the anode.
- The molybdenum cup in the cathode directs the elctrons to the tungsten target in the anode.
-the electrons travel from the cathode to the anode.
- the x-ray travel through the unleaded glass window, the tube head seal, and the aluminum filter.
- Aluminum filter removes the longer wavelength x-rays. The longer wavelengths are removed because they are less penetrating and therefore not used in dental radiology.
- The x-ray beam travels through the collimator.
- x-ray beam travel down the lead lined PID and exit at the end of the PID.
- At this point the photnons are directed through the patient’s cheek through the structures in question and toward the film.
Types Radiation
different type of radiation. when waves or energy pass through a medium or space.
Types
- Primary radiation: consists of x-rays that com from the target of the x-ray tube.
- secondary radiation: x-radiation created when the primary beam interacts with matter.
- scatter radiation: is a form of secondary radiation. It results when an x-ray bean has been deflected from its path by interaction with matter.
Biologic effects of radiation
latent period: to log between exposure to radiation and when symptoms or malignancies can occur.
Acute Radiation: exposure that occures when a large does of radiations is absorbed in a shot period, such as in a nuclear accident.
Chronic Radiation: when a small amount of radiation are absorbed repeated over a long period.
Genetic and somatic effects
x-ray affect both
genetic somatic cells.
genetic cells are the reproductive cells: sperm and ova.
genetic Mutations: damaged genetic information in cells that is passed from one genetic to next.
somatic cells: tissues made up of cells that ultimately from the body organs (skin, bone, liver, and so on) but not passed on future generations
Critical organs
- skin
- thyroid gland
-lens of eye - bone marrow
cell types that are most sensitive to radiation are those that generally
- Have a high mitotic rate (cells dividing)
- will most likely undergo many future mitoses.
-Are primitive (less differentiated cells that will be most likely with genetic signal) in their differentiation
non-dividing cells that are very radiosensitive
-Lymphocytes: white blood cells in the immune system.
-Oocytes: female reproductive cells.
Radiation measurements
two sets of systems are used to define the way in which radiation is measured.
- older system is referred to as the traditional or standard system
- the newer system is the metric equivalent, know as system internationale , or SI.
