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)
What object can be used to limit scatter radiation? When would you use it?
A grid. Body parts over 10cm in thickness require the grid
What are the 4 basic cautions during patient positioning?
- Patient welfare 2. Resraint/immobilization that will be needed 3. Potential trauma to area of interest 4. Exposure to restrainers
What views are required when taking a radiograph?
Almost always 2 views, a lateral and a VD or less commonly a DV
We are instructed to take a thoracic radiograph. Where do you measure? What are the peripheral borders? Inspiration or Expiration, Why?
Measure: Caudal border of Scapula Peripheral borders: Scapulohumeral articulation to L1. Inspiration because we want a gap between the diaphragm and the heart
We are instructed to take an abdominal radiograph. Where do you measure? What are the peripheral borders? Inspiration or Expiration, Why?
Measure: Thoracic-lumbar junction (Caudal portion of 13th rib in canines, 2-3 finger widths caudal in felines) Peripheral borders: T-9 to Femoral head Expiration so that diaphragm is cranial and out of the way
What are the 5 steps of manual developing?
- Developer for 5 mins (At 20 degrees C) 2. Rinse in water for 30 seconds 3. Fixer for twice the developing time (10 mins) 4. Final rinse for 2x fixing time (20 mins) 5. Dry 5-10 mins
What does the Developer do?
Converts exposed silver halide crystals to black metallic silver
What 2 purposes does the Fixer provide?
Clears away unexposed silver halide crystals and hardens the emulsion
True or false: It is safe to dump Developer and Fixer down the drain.
False. It is safe to dump Developer down the drain but since the used Fixer has reminants of unexposed silver halide crystals it is unsafe and needs to be treated as a biohazard
What part of the limb is “Distal”? What part is “Proximal”?
Distal: Distal to the elbow/stifle (to carpus) Proximal: Up to and including the elbow/stifle
What position would an animal be in if we were taking a Proximal limb radiograph?
Dorsal recumbency
For a proximal limb radiograph, the fore limb is in the Caudal-Cranial position. What does this mean?
It means that the underside of the limb (Caudal, which we want to call Dorsal) is facing up to the tube head, so the beam goes in through the Caudal side of the limb and out through the Cranial side and through the table
For a proximal limb radiograph, the hind limb is in the Cranial-Caudal position. What does this mean?
It means that the Cranial portion of the limb (the top of the limb) is facing up toward the tube head so the beam is coming in through the Cranial portion and exiting through the Caudal portion into the table
For a distal limb radiograph, in what position do we place a fore limb?
Dorsopalmar (In through the top of the paw, out through the bottom)
For a distal limb radiograph, in what position do we place a hind limb?
Planterodorsal (In through the bottom of the hind paw, out through the top)
If you were to radiograph a long bone, what would be included in the view?
The joint, distal and proximal bone
If you were to radiograph a joint, what would you include in the view?
Include 1/3rd of the limb distal and proximal to the joint
True or False: When radiographing a limb, it is best to have the affected limb facing up so it is closer to the tubehead
False. The affected limb should always be down so it is closest to the film
When radiographing the left limb, what happens to the right limb?
It is pulled caudally out of the field of view
What is a special precaution when taking a radiograph of the elbow joint?
It needs to be flexed
If both limbs need to be in the view, such as for patellar radiographs, which limb is pulled cranially?
Affected limb
Limbs are measured at the _______ for radiographs
thickest portion
What is a precaution with taking Scapula lateral views?
Sedation is needed
What common mistake is made on Shoulder Lateral views?
The limb is not extended and the skull and cervical vertebrae are therefore not extended
We use a Grid to radiograph a body part that is over _____ cm thick
10
What is the main purpose of the Grid?
To minimize scatter from reaching the film
How does a Grid reduce scatter?
It contains specifically angled pieces of lead that coordinate with the angle of the x-rays coming down. It only lets primary beam through to the film while the rest is absorbed by the lead
As you ______ scatter, you _____ contrast (increase or decrease)
Increase, Decrease
Although the Grid is often placed under the table, where else can we put it? (2)
As a part of the cassette or loosely above the cassette
Characteristics that make up a Grid include:
Grid Focus, Grid Cut-Off, Grid Efficiency
What is the Grid Focus?
Distance from the focal spot to the Grid (tube head to Grid)
What is the Grid Cut Off? What causes this?
Progressive decrease in transmitted x-ray intensity toward the edges caused by absorption of primary x-rays by the grid lines.This is often caused by the Focal Spot & Grid not being at optimal distance from each other.
What are 3 secondary ways that Grid Cut Off can occur?
Improper centering under the tube, tilting the grid or tilting the tube
What is the Grid Efficiency?
How well a Grid can absorb scatter radiation in the production of a radiograph.
How does the Grid increase efficiency?
Absorbs scatter therefore reducing greyness and increasing contrast
What components are in the Grid?
The ratio height and the Lines per centimeter
What is the Grid Ratio?
Relationship of the height of the lead strips to the distance between them.
The higher the Grid ratio, the ______ the efficiency of the Grid
higher
What is the concern of using a high Grid Ratio?
It absorbs scatter but can also absorb primary beam so exposure factors must be increased
Describe the Lines per Centimeter component of a Grid
The more lead lines per centimeter, the more surface area to absorb scatter radiation
What Grid Pattern do we use? What does this mean?
Focused Grid, where the beam comes down to the table on an angle outward
What happened here? How can we fix it?
Grid Cut Off due to improper use or placement of the Grid. To fix this, reposition the Grid.
What went wrong with this radiograph?
Grid Cut Off
What does this image represent?
A Focused Grid type of Grid Pattern
You are taking a lateral picture of the Skull. Where do you measure? Where is the center of the beam? What are the peripheral borders?
Measure: Highest part of the Zygomatic arch (cheekbone)
Center: Lateral canthus of eye
Peripheral borders: Tip of nose to base of skull
How do we position the animal for a lateral skull radiograph?
Lateral recumbency & a foam pad proping the mandible and neck up
You are taking a DV view of the skull. Where do you measure? What do you include? Where is the beam centered?
Measure thickest part of cranium, include the entire skull and center the beam between the 2 lateral canthae of eyes
What are the positioning requirements for a DV skull radiograph?
Sternal recumbency with forelimbs natural. Sandbag over neck region.
What is one way we can tell the animal is straight before doing a DV skull radiograph?
The “line” between the medial canthae is parallel to the table
Why would we perform a Rostrocaudal view of the skull?
To see the frontal sinuses, tympanic bullae or odontoid processes
You set up the patient for a Rostrocaudal view of the frontal sinuses. Then you learn that you need to take an image of the tympanic bullae. How do you alter your positioning to get the best view?
Pull the nose caudally 10-15 degrees
What view and position would we use to get the best view of the Nasal Cavities?
VD with mouth open
When you hear the Veterinarian mention the “horse heads” on a radiograph, what are they referring to?
Intervertebral spaces
All different views of the spine reuire both a VD and a Lateral image. What is the exception to this rule?
- VD
- Extended lateral
- Flexed/hyperxtended
