Chapter 1 & 2 // Radiology

what 3 components make up a dental x-ray machine?

1. control panel 2. extension arm 3. tubehead

X-rays differ in energy and wavelength. Kinetic energy of the electrons is converted to c-ray photons through one of the two mechanisms

1. general (braking) radiation 2. characteristic radiation

1. plate or tungsten; a focal spot and converts bombarding electrons into x-ray photons. 2. dissipates the heat away from the tungsten target

1. tungsten target 2. copper stem

Characteristic radiation accounts for a very small part of x-rays produced in the dental x-ray machine. It occurs only at...

70 kV and above because the binding energy of the k-shell electron is approximately 70 keV

total transfer of energy from the x-ray photon to the atoms of matter through which the x-ray beam passes.

Absorption

sheets of 0.5 mm thick aluminum placed in the path of the x-ray beam, filter out the non-penetrating, longer wavelength x-rays

Aluminum disks

The measurement of the number of electrons moving through the cathode filament. measured in amperes (A) or milliamperes (mA)

Amperage

Positive electrode -has wafer-thin tungsten plate embedded in a solid copper rod -the anode converts electrons into x-ray photons. The anode also include the tungsten target and copper stem.

Anode

serves as a voltage compensator that corrects for minor fluctuations in the current

Autotransformer

How are atoms arranged on the periodic table?

By atomic number on the period table of the elements

How are molecules formed?

By the transfer of electrons or by the sharing of electrons between the outermost shells of atoms

Exposed first dental radiograph in United States (skull) on a living person 1896

C. Edmund Kells

Negative electrode - tungsten filament; coiled wire made of tungsten, which produces electrons when heated. -molybdenum cup; focuses the electrons into a narrow beam and directs the beam across the tube toward the tungsten target of the anode

Cathode

produced when a high-speed electron dislodges an inner-shell electron from the tungsten atom and causes ionization of that atom. once the electron is dislodged, the remaining orbiting electrons are rearranged to fill the vacancy .

Characteristic radiation

what is a particle concept?

Characterizes electromagnetic radiations as discrete bundles of energy called photons or quanta

ionization takes place, an x-ray phonton collides with a loosely bound outer-shell elctron and gives up part of its energy to eject the electron from its orbit; the x-ray photon loses energy and continues in a different direction at a lower energy level, incident photon still exists

Compton scatter

Manufactured pre wrapped intraoral film....

Eastman Kodak, 1913

Introduction of the long-cone paralleling technique

F. Gordon Fitzgerald, 1947

From 1896 to 1913....

Hand- wrapped glass photographic plates or film were wrapped in black paper and rubber.

Uses 65,000 to 100,000 volts; provides the high voltage required to accelerate electrons and to generate x-rays in the x-ray tube, and is controlled by the kilovoltage settings

High voltage circuit

First to expose a panoramic radiograph

Hisatugu Numata - 1933

oil that surrounds the x-ray tube and transformers inside the tubehead; prevents overheating by absorbing the heat created by the production of x-rays.

Insulating oil

The x-ray photons that pass through a patient without interaction are responsible for producing densities and make dental radiographies possible.

It is possible for an x-ray photon to be completely absorbed within matter, or the tissues of a patient.

where is the strongest binding energy, closest to the nucleus, found?

K shell, whereas electrons located in the outer shells have a weak binding energy.

Lead plate with a central hole that fits directly over the opening of the metal housing, where the X-rays exit; restricts the size of the X-ray beam.

Lead collimator

leaded-glass vacuum tube that prevents x-rays from escaping in all directions; one end of the tube has a "window" that permits the x ray beam to exit the tube and directs the x-ray beam toward the aluminum disks, lead collimator, and PID. (pushing beams through)

Lead glass housing

The metal body of the tubehead that surrounds the X-ray tube and transformers and is filled with oil; protects the X-ray tube and grounds the high voltage components

Metal housing

Made the first dental radiograph 1895

Otto Walkhoff

Aims and shapes the x-ray beam; open ended, lead lined cylinder that extends from the opening of the metal housing of the tubehead. Sometimes referred to as the cone.

Position indicating device (PID)

refers to the penetrating x-ray beam that is produced at the target of the anode and that exits the tubehead

Primary radiation (useful beam)

conversion of AC to DC

Rectification

A form of secondary radiation that occurs when an x-ray beam has been deflected from its path by interaction with matter. scatter radiation is deflected in all directions by the patient's tissues and travels to all parts of the body and dental operatory.

Scatter radiation

radiation that is created when the primary beam interacts with matter. in dental terms, matter includes the soft tissues of the head, bones of the skull, and teeth.

Secondary radiation (less penetrating than primary radiation)

Compton Scatter: It is possible for an x-ray photon to be deflected from its path during its passage through matter.

The term "scatter" refers to this type of radiation. at the atomic level, the Compton effect accounts for most of the scatter radiation.

coherent scatter occurs when a low energy x-ray photon interacts with an outer-shell electron; no change in the atom occurs, and x-ray photon of scattered radiation is produced.

The x-ray photon is scattered in a different direction from that of the incident photon; no loss of energy and no ionization occurs.

Absorption of Energy and Photoelectric Effect: It is possible for an x ray photon to pass through matter or the tissues of a patient without any interaction.

The x-ray photon passes through the atom uncharged and leaves the atom uncharged.

The aluminum or leaded glass covering of the tubehead that permits the exit of X-rays from the tubehead ; seals the oil in the tubehead and acts as a filter to the X-ray beam

Tubehead seal

Oil immersion of the tubehead 1923

Victor X-ray Corporation

measurement of electrical force that causes electrons to move from a negative pole to a positive one. measured in colts (V) and kilovolts (kV) (the current passing from the cathode to the anode)

Voltage

father of x-rays, discovered in 1895, experimented with vacuum tubes and florescent screens. he noticed screens were glowing even though they were several feet from tube

Wilhelm Conrad Roentgen

developed the first hot-cathode x-ray tube, a high vacuum tube that contained a tungsten filament 1913

William Coolidge

heart of the x-ray generating system

X-ray tube

are electromagnetic radiations believed to move through space as both a particle and a wave?

Yes. Therefore; 2 concepts must be considered. 1. Particle concept 2. Wave concept

Four types of particulate radiations; 1. Electrons (beta particles or cathode rays)

a. beta particles; fast moving electrons emitted from the nucleus of radioactive atoms. b. cathode rays; streams of high-speed electrons that originate in an x-ray tube.

The ejected electron is termed a photoelectron and has a negative charge; it is readily......

absorbed by other atoms.

how are electromagnetic radiations arranged?

according to their energies in what is termed the electromagnetic spectrum.

an electrical current in which the electrons flow in two, opposite directions.

alternating current

Most atoms are normally neutral. What does a neutral atom contain?

an equal number of protons and electrons.

4. Neutrons

are accelerated particles, specifically hydrogen nuclei with a mass of 1 and no electrical charges.

3. Protons

are accelerated particles, specifically hydrogen nuclei, with a mass of 1 and a charge of +1 (positive).

has a central nucleus and orbiting electrons; the identity is determined by by the composition of the nucleus and the arrangement of its orbiting electrons

atom

the number of protons in the nucleus equals the number of electrons outside the nucleus and determines the....

atomic weight of the atom

what are photons?

bundles of energy with no mass or weight, also travels as waves at the speed of light and move through space in a straight line. ("carries energy" of electromagnetic radiation)

how are electrons maintained in their orbits? (known as binding energy)

by electrostatic force (attraction) between positive and negative electrons.

a path for an electrical current 2 electrical circuits are used in the production of x-rays; 1. low-voltage or filament curcuit 2. high-voltage curcuit

circuit

the ejected electron is termed.....

compton electron (recoil electron) (has a negative charge, but the remaining atom has a positive charge)

what are the use of dental images?

confirm or classify diseases; localize lesions and foreign objects; provide information during dental procedures (root canal, implant); evaluate growth and development; illustrate changes secondary to caries, periodontal disease, and trauma; document the condition of patient; and develop a clinical treatment plan.

electromagnetic radiations are man made or occur naturally, what are some examples?

cosmic rays, gamma rays, x-rays, ultra-violet rays, visible light, infrared light, radar waves, microwaves, and radio waves.

A photographic image produced on film by the passage of x-rays through teeth and related structures

dental radiograph

Any person who positions, exposes, and processes x-ray image receptors.

dental radiographer

The production of radiographs of the teeth and adjacent structures by the exposure of image receptors to x-rays.

dental radiography

when electrons flow in one direction through the conductor

electrical current (direct current, DC)

An atom that gains or loses an electron becomes...

electrically unbalanced, known as an ion

an atom with an incomplete filled outer shell is....

electrically unbalanced. it attempts to capture an electron from an adjacent atom.

the propagation of wavelike energy (without mass) through space or matter

electromagnetic radiation

the wave concept characterizes....

electromagnetic radiation as waves and focuses on the properties of velocity, wavelength , and frequency.

how are binding energies of orbital electrons measured?

electron volts (eV) or kilo electron volts (keV)

2. Alpha Particles

emitted from the nuclei of heavy metals and exist as protons and neutrons

electromagnetic radiations can be classified as ionizing or non-ionizing depending on their...

energy levels. (electromagnetic spectrum)

Uses 3 to 5 volts; regulates the flow of electrical current to the filament of the x-ray tube, and is controlled by the milliampere settings

filament circuit

Speeding electrons slow down because of their interactions with tungsten target in the anode. Many electrons that interact with the tungsten atoms undergo not one but many interactions within the target. most x-rays are produced in this manner; approximately 70% of the x-ray energy produced at the anode can be classified as general radiation

general (braking) radiation

In the electromagnetic spectrum, only _____________ are capable of ionization.

high-energy radiations. (cosmic rays, gamma rays, and x-rays)

a picture or likeness of an object

image

A recording medium; examples include x-ray film, phosphor plate, or digital sensor

image receptor

The creation of digital, print, or film representations of anatomic structures for the purpose of diagnosis

imaging, dental

when an electron is removed from an atom in the ionization process, what is a result?

ion pair. the atom then becomes the positive ion while the ejected electron becomes the negative ion.

production of ions, or the process of converting atoms into ions.

ionization

radiation that is capable of producing ions by removing or adding an electron to an atom

ionization radiation

binding energy is determined by the distance between the nucleus and orbiting electron and.....

is different for each shell

what does the number of protons and neutrons in the nucleus of an atom determine?

mass number / atomic weight

electrons are tiny, negatively charged particles that have very little.....

mass. an electron weighs approximately 1/1800 as much as proton or neutron.

anything that occupies space and has mass; when altered, energy results

matter

When atoms combine they can form____________. Water is an example of this (2 Hydrogens and 1 Oxygen)

molecules

When an atom gains an electron, it becomes...

negative

carry no electrical charge

neutrons

composed of particles known as protons and neutrons; known as the dense core of the atom

nucleus

what part of the atom occupies very little space? (most of the atom is empty space)

nucleus

like planets revolving around the sun, electrons travel around the nucleus in well- defined paths known as...

orbits or shells

tiny particles of matter that possess mass and travel in straight lines at high speeds.

particular radiation

When an atoms loses an electron, it becomes...

positive

Carry a positive electrical charge

protons

form of energy carried by waves or stream particles

radiation

the emission and propagation of energy through space or a substance in the form of waves or particles

radiation

The process by which certain unstable atoms or elements undergo spontaneous disintegration, or decay, in an effort to attain a more balanced nuclear state

radioactivity

An image or picture produced on a receptor by exposure to ionizing radiation; a two dimensional representation of a three-dimensional object

radiograph

The art and science of making radiographs by the exposure of film to x-rays.

radiography

The science or study of radiation as used in medicine.

radiology

decrease the voltage from the incoming 110- or 220- line voltage to the 3 to 5 V used by the filament circuit. this has more wire coils in the primary coil (input coil) than in the secondary coil (output coil)

step-down transformer

increases voltage from incoming 110- or 220- line voltage to the 65,000 to 100,000 volts used by the high voltage circuit. this has more wire coils in the secondary coil (output) than in the primary coil (input coil)

step-up transformer

how can the amperage and the voltage be adjusted in a cathode filament?

the amperage can be increased or decreased by the milliamperage (mA) adjustment on the control panel of the x-ray machine. The voltage is adjusted by the kilovoltage (kV) on the control panel.

What does wavelength mean?

the distance between the crest of one wave and the crest of the next, determines the energy and penetrating power of radiation.

An x-ray photon collides with a tightly bound, inner shell electron and gives up all its energy to eject.....

the electron from its orbit

the k shell is located closest to the nucleus and has...

the highest energy level

what does frequency mean?

the number of wavelengths that pass a given point at a given amount of time

What does velocity describe?

the speed of a wave. (all electromagnetic radiations travel as waves or a continuous sequence of crests at the speed of light.)

Coherent Scatter: another type of scatter radiation that may take place when x-rays interact with matter. it involves an x-ray photon that has its path altered by matter

this is also referred to as the "unmodified scatter"

electricity is the energy used....

to make x-rays.

device that alters the voltage of incoming electricity

transformer

as well as electromagnetic radiations, x-rays have the properties of both....

waves and particles

when is general (braking) radiation produced?

when an electron hits the nucleus of a tungsten atom or when an electron passes very close to the nucleus of a tungsten atom

a high-energy radiation produced by the collision of a beam of electrons with a metal target in an x-ray tube

x- radiation

High energy, ionizing electromagnetic radiation

x-radiation

a beam of energy that has the power to penetrate substances and record image shadows on receptors

x-ray

what interacts with the materials that penerates and causes ionization?

x-ray photons.

a tightly sealed, heavy metal housing that contains the x-ray tube that produces dental x-rays.

x-ray tubehead

weightless bundles of energy (photons) without an electrical charge that travel in waves with a specific frequency at the speed of light

x-rays