Test 2 Flashcards
What is ionizing radiation?
Radiation that has enough energy to remove electrons from atoms, creating ions
Why is ionizing radiation dangerous?
When electrons are stripped from atoms they can interact with other biological molecules (strands of DNA which in turn causes mutations in cells) in the body. The radiation intensity depends on exposure time and strength of radiation
True or False: Radiation damage in an individual can be passed onto their offspring
True. Damage to the genetic code in reproductive cells can show up in future generations
What is the name of the device that monitors your personal radiation intake? How does it work?
A Dosimeter contains a Lithium or Calcium Fluoride crystal that absorbs radiation. When the crystal is heated it releases stored energy which can then be measured in the form of visible light
What is secondary radiation? What can lead to this?
Most often “scatter radiation” which is radiation that has deflected off of an object and onto you. Increased kvp and increased field size can cause this.
Why are persons under 19 more likely to develop cancer from radiation exposure?
Tissues are still growing, meaning that cell divisions are more freuently. Cells are more suspectible to radiation damage and mutation during division
When manually restraining, what equipment should be worn? (4 items)
Apron, gloves, glasses and thyroid protectors all of which are lined with lead
Why is the wall colour important when designing a developing/dark room?
Lighter colours reflect less light
Why is the colour of the safelight important?
Red light does not affect film due to its wave length
How do you test a safelight?
Expose film in 1/4 increments for 1 minute each. If it is working properly, you will just see a black film. If it is not working properly, you will see 4 different shades of exposure
What is reticulation? What causes it?
Wrinkles or cracks in the film causes by temperature difference between the developer and fixer
What will happen if you do not rinse/wash your radiograph?
The image will darken over time
What are 2 main differences between manual and automatic processors?
Automatic uses a higher temperature and does not rinse between developer and fixer, rather Automatic has a series of squeegee like structures
Legally, how long must radiographs be kept for?
5 yrs
What are “x-rays” and how do they compare to visible light?
X-rays are electromagnetic radiation. They have greater energy and a shorter wavelength
What is excitation and how does it work?
A method of transporting energy through space. A collision with a moving particle excites the atom which causes an electron to “jump” or accelerate to a higher energy level (orbit). When the electron “falls” back down from the unstable position it releases the energy as electromagnetic radiation (photon)
The shorter the wavelength, the _______ the energy
Greater
How are x-rays formed in an x-ray machine?
Negatively charged electrons are emitted from a cathode (via heating process) and accelerated (via kVp) toward a positively charged anode (metal surface). The electrons react with the metal anode and when they collide with a nucleus, they knock an electron out of an inner ring of the target metal atom. This starts the process of excitation which releases an electromagnetic photon (x-ray). This actually only happens to 1% of electrons. The other 99% will miss and generate heat instead
What is brehmsstrahlung or “braking radiation”
The process of the electrons decelerating and releasing electromagnetic radiation when hitting the metal anode
What factors effect exposure? How?
Higher kVp = stronger beam with more penetrating power Higher mAs = longer duration of exposure = more electrons converted into x-rays Shorter SID = more penetrating power
What does milliamperage (mA in mAs) do?
It is responsible for heating the cathode. More heat = more electrons
What is thermionic emission?
The process of heating the cathode to release electrons
How can you differentiate if the density of a film was caused by the kVp setting or the mAs setting? How can you correct it?
First, determine if the problem was the kVp by looking at the penetration of the image. (No details means a low kVp). If penetration was not a problem, then the mAs is the problem. If the film does not have high density but the penetration is okay, double the mAs. If the film is over penetrated you will see grey bones. Lower kVp 10-15%
What is contrast? How does it apply to radiographs of soft tissue vs bone?
The difference between the adjacent densities of the film (black, white, shades of grey). You want high contrast for bones (lower kVp) and low contrast for soft tissue. (higher kVp)
