The technical side Flashcards
Basic concepts of radiology
Proportionality: relationship between two numbers
Direct: the first number is directly proportional of the second
Ex: circumference of circle directly proportionate to diameter
Indirect: as one number increases the other decreases
Units of Measurement
Length – meters (m)
Measure patients in cm, measure distance from x-ray tube to cassette in m
Time – seconds (s)
Amount of radiation over a given amount of time
Length of time film is in processing chemicals
Contrast studies
Elements and atoms
Elements are composed of atoms
Atoms have a nucleus that contains protons and neutrons and orbiting that nucleus are electrons
Protons = positive charge
Neutrons = neutral (no charge)
Electrons = negative charge
The number of protons and electrons an atom has determine that element’s atomic number
An atom is considered stable when the number of electrons and protons are equal
The atom
Electrons are held in orbit by the proton’s positive charge – this is called Electron Binding Energy
As proton numbers increase, electron numbers increase
This results in an increased distance of electrons from the nucleus lowering the electron binding energy and causing the atom to become less stable
This means the higher the atomic number, the less stable the atoms of that element
Ionization of an atom
When atoms are unstable an electron may leave it’s orbit – this is referred to as ionization or being “boiled off’
The atom would now have a positive charge or be considered ionized
The first step in x-ray production is to boil off the electrons from the filament of the cathode
As atomic weight increases so does that atom’s ability to affect other elements
This principle is used in radiation safety and contrast studies
Isotopes
An atom with the same atomic number but a different atomic mass is an isotope
Atomic mass is the number of the neutrons and protons in the nucleus
Contains the same number of protons but a different number of neutrons
This concept is utilized in contrast media, nuclear medicine, and oncology
Radioactivity
Some atoms exist in abnormal state of excitement characterized by an unstable nucleus
Instability of nucleus caused by imbalance of neutrons and protons with reference to number of electrons orbiting nucleus
Radioactive Disintegration or Decay
Is the atom’s attempt to reach stability
The nucleus spontaneously emits particles and energy and transforms into a different but stable atom
This is an important concept in nuclear medicine
Electromagnetic spectrum
Two major types of energy in x-ray technology: electrical energy and electromagnetism
X-ray technology involves radiation and visible light
Particle wave theory
X-rays travel in straight lines as waves
Have wavelength and frequency
Waves have amplitude
X-rays are also particles
These particles are Photons of pure energy
Photon
Bundle of radiant energy
Smallest quantity of electromagnetic energy
Particles that travel in waves at the speed of light
Wavelenght
measurable distance between two crests or troughs
Frequency
time factor between two crests or troughs
The number of waves passing a given point per unit of time
Shorter wavelength = higher frequency =higher penetration
Longer wavelength =lower frequency = lower penetration
Energy as particles
Photons interact with matter as though they are a particle
Photon particle carries a specific energy dependent on frequency
Energy and frequency are directly proportional
Ex: energy doubles, frequency doubles
X-ray beam is composed of bundles of pure energy (photons) carried by a wave
Discovery of xrays
Discovered in 1895 by German scientist Wilhelm Conrad Roentgen
During an experiment he noticed a cardboard screen coated in platinocyanide glowing a few feet away
Named them “x-rays” because of the unknown nature
In science “x” denotes the unknown
Listed 12 unique properties of x-rays:
Properties of xrays
Invisible
Electrically neutral
No Mass
Travel at the Speed of Light in a Vacuum
Cannot be Focused by a Lens
Form a Polyenergetic (Heterogeneous) Beam
Can be Produced in a Range of Energies (kV)
Travel in Straight lines Lines
Cause Fluorescence in Certain Substances
Can Cause Chemical Changes to Occur in Radiographic and Photographic Film
Can be Absorbed or Scattered by Tissues in the Body; Can Produce Scattered and Secondary Radiation
Can Cause Chemical and Biological Damage to Living Tissue
Electric circuit four important facotrs
Current (I) – Milliamperage is the unit used
Voltage (V) – Speed with which electrons transfer energy along a circuit.
High voltage (kV) produces short-wavelength/high-frequency, highly penetrating x-rays
Resistance (R) – factor that slows the current.
Large diameter = low resistance.
Small diameter = high resistance
Time – timer controls the length of time x-rays are produced.
Determined by setting on control panel
Diagnostic xray production, the power supply
Standard power supplies will not be enough to activate most x-ray units
Need to install transformers (auto, filament and step up) in both the facility and within the unit
In North America, power companies supply an alternating current
Power supply to x-ray unit must not fluctuate – need rectifiers to change alternating current to direct current
Rectifiers will keep the current positive and allow for proper flow in one direction (cathode to anode)
