Diagnostic Principles Flashcards
what does radiography do?
help diagnose diseases and conditions
how and when was radiography discovered?
by Physicist Wilhelm Conrad Rontgen in 1895 when he was experimenting with electron flow in vacuum tubes
what is radiation?
- a form of electromagnetic energy
- consists of different types of waves
- made up of particles called photon or quanta
what are the 5 types of radiation waves?
- radiowaves
- visible light
- x-rays
- infrared
- ultraviolet
what is wavelength?
the distance between two consequtive corresponding points on a wave
what is frequency?
the number of cycles of the wave that pass through a stationary point per second
how are wavelength and frequency related?
- inversely
- short wl, high f
- long wl, low f
how is wavelength measured?
in nanometers
what are some properties of x-rays?
- penetrate living tissues and materials
- invisible
- cumulative
- travel at the same speed
how are x-rays produced?
when electrons are slowed down or stopped by the atom of the target area inside the x-ray tube head as a result of the high speed collision of atom
what is an atom?
made up of electrons, protons, and neutrons
what is the melting point and atomic number of tungsten?
high melting point- 3422
atomic number is 74
what is bremsstrahlung?
when an electron passes near the nucleus it is slowed and its path is deflected, energy lost is emitted as a bremsstrahlung x-ray photon
what are the three main requirements for x-ray production?
- a source of electron production
- a target for the electrons to hit
- a method of moving the electron from the source of the target
what is in the x-ray machine?
tube head, a stand, control panel, lead lined table
what is a cathode?
- negative part of the x-ray tube
- made up of a coiled tungsten wire filament housed within a molybdenum focusing cup
- weak electric current
what is the focusing cup?
- heated tungsten sits within focusing cup
- negatively charged so electrons are repelled into a group in the middle
what is mAs?
- milliamperes
- affects the number of x-rays produced
what is the anode?
- the target for the electrons
- made of tungsten
- positively charged
- where the x-ray beam originates
what is kV?
- kilovolts
- strong electric current is applied between the anode and cathode which makes the anode+ and cathode-
what are the two types of anode?
- stationary anode
- rotating anode
what is a stationary anode?
- target area is small so lower mA and kV
- heat dispersed is limited
- found in portable x-ray machines
what is a rotating anode?
- target spread over a rotating disc
- increased surface area
- angled at 20*
- rotates when exposure is made
what is the focal spot - penumbra effect?
- penumbra effect
- penumbra is the lack of detail caused by the focal spot size
- smaller the focal spot, shaper the image
- larger focal spot, lack of detail, more shadow = penumbra
how can you reduce penumbra in a radiographic image?
- use a small focal spot
- increase exposure time
- increase added filtration
- align the tube appropriately
what is in the x-ray tube head?
- cathode and anode
where are the cathode and anode mounted in an x-ray tube head?
In a vacuum inside a pyrex container
why is the pyrex container in an x-ray tube head surrounded by oil?
helps with heat dissipation
what electrical apparatus is involved in an x-ray circuit?
- step up transformer (turns mains volts into kilovolts)
- step down transformer (reduces mains current from amps to milliamps)
- an auto transformer
- a rectifier circuits
what does kV control?
the quality of penetrating power of the x-ray beam
what does kV affect?
- scale of contrast (grey)
- radiographic density (black)
what does mAs determine?
the tube head current, quality of x-rays
what is opacity?
the description of the radiographic appearance of an object - how many x-rays are allowed to pass through that object
what are the 5 radiographic opacities?
- metal
- mineral
- fluid
- fat
- gases
what are the 3 factors that appearance of an anatomic part on a radiograph is related to?
- density and atomic number
- thickness and shape
- surrounding objects
