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238 Cards in this Set
- Front
- Back
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Founder of x-rays
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Wilhelm Roentgen
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When were x-rays discovered?
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November 8, 1895
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Where were xrays discovered?
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Wurzburg University in Germany
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When Crookes tube was closer to an object, it was considerably brighter
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Inverse square law
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What year did Wilhelm Roentgen win the Nobel Prize for physics?
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1901
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What was the first xray made?
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Roentgen's wife's hand
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What does xray mean?
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the unknown ray of light
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When was "on a new kind of rays" paper published?
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December 28, 1895
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First medical xray in the US was done on who?
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Eddie McCarthy
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What part of Eddie McCarthy was xrayed?
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distal radius (Colle's fx)
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When and where was the first medical xray taken?
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February 3, 1896
Dartmouth College |
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Who took the first medical xray?
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Frost Brothers
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Inventor of the fluoroscope
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Thomas Edison
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Xray that allows you to see motion
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fluoroscope
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Who holds the record for the most patents?
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Thomas Edison
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Name of Thomas Edison's assistant
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Clarence Dally
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Better version of the Crookes tube?
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Coolidge tube
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Current day xray tube
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coolidge tube
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Who developed the Coolidge tube?
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William Coolidge
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Year coolidge tube was developed?
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1913
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potential energy power
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kv
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penetration of electrons
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kV
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optimal kV for AP lumbar
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80 kvp
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optimal kV for lateral lumbar
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90 kvp
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Why is there protective housing around xray tube?
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reduces intensity of leakage
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Leakage radiation
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<100 mR/hr @ 1 meter
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What is the xray tube housing made out of?
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lead
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What do you call the center of the primary beam?
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central ray
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What do you call the useful beam?
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primary beam
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% of electrons that create xrays?
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1%
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% of electrons that create heat?
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99%
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What determines the optimal kVp?
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the sequence of structures
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What determines the mAS?
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size of the patient
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What determines the # of xrays needed?
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size of the patient
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What happens to the desity when you increase mAS?
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increases
darkens |
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What is directly related to dose?
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mAS
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Golden rule:
What do you never stray from? |
the optimum kVp
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Golden rule:
Eliminate as many what as possible? |
variables
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What are the 2 functions of the tube housing of the xray tube?
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1) prevents against electrocution
2) reduces the intensity of the leakage radiation to less than 100 mR/hr at 1 m. |
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What is the glass envelope of the xray tube made of?
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pyrex glass
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Target
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anode disc
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What is the rod made of?
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Molybdenum
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2 primary parts of the xray tube?
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1) cathode
2) anode (stationary and rotating) |
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Components of the cathode
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- filaments/focal spots
-focusing cup |
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Components of the anode
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-disc
-molybdenum rod |
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What type of anode does the coolidge tube have?
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rotating anode
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What type of unit has only 1 filament?
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dedicated unit
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Name 2 professions that use a dedicated unit.
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1) dentistry
2 mammograms |
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What are the cathode filaments made out of?
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thoriated tungston
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3 reasons why filamets are made out of thoriated tungsten?
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1) high atomic number (74)
2) high thermal conductivity (efficient heat dissipator) 3) high melting point (3400 degrees Celsius) |
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AKA for filament?
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focal spot
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What are 3 things you need to choose for every exposure?
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1) filiament size (small or large)
2) mAS 3) kVp |
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"boiling off" of the electrons in the outer shell of the filament atoms
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themionic emission
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cloud of electrons around the filament
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space charge
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overall darkening of the film
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density
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With which areas of the body do you use the small filament?
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1) C-spine
2) extremities 3) chest |
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With which areas of the body do you use the large filament?
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1) full spine
2) thoracic spine 3) lumbar spine 4) hip |
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Detail and heat with small filament
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more detail
more heat |
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Detail and heat with large filament
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less detail
less heat |
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sharpness clarity
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detail
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focuses the electron beam towards the anode
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focusing cup
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type of anode used in dental, some portable xray machines and other special purpose units not requiring high tube current
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stationary anode
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What is the only advantage of having a rotating anode?
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allows for a larger target area, therefore less heat
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The target of the anode disc is made out of thoriated tungsten. What is it mixed with and why?
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-rhenium
-provides stability (other materials would warp) |
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powers rotating anode?
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electric (induction) motor
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allows electrons to spread out to dissipate heat
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anode disc angle
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What is the heat sink made of?
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copper
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speed of rotating anode
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3,400 RPM
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What is the rotor made out of?
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iron
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a series of copper wire loops (an electromagnet)
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stator
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75% of xray models used today are ______ phased?
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single
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Dead man switch
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-2 step process to generate xray
-prevents accidental exposure -protects the machine |
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2 steps for dead man switch?
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1) prep or rotor
2) expose or xray |
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anode speed
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3400 RPM
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What should you do to the machine to prevent damage?
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warm up the machine
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What determines the mas?
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the thickness of the part being xrayed
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What is directly related to the density of the film?
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mas
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Mas setting will change depending on what?
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patient's measurment
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# of xrays in useful beam
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mAs
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mAs equation
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milliamperage x time
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Where you look up the factors?
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technique chart
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What determines xray quality?
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kVp
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Describes the penetrating power of the xrays
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kVp
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inversely related to the contrast of the film
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kVp
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What determines the kVp?
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the sequence of structures the xrays must pass thru
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optimum kVp
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WILL NOT CHANGE from patient to patient
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required to ensure that the electrons flow from the cathode to the anode only
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direct current (DC)
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Xray machines can only use what type of current?
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DC
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the process of converting AC to DC
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rectification of the xray current
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Golden rule:
Don't be afraid of what? |
mAs
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What happens if you cut the mas in half?
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-cut dose in 1/2
-cut time -decreases heat |
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What happens if you cut focal spot size in 1/2?
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better detail
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Benefits of high frequency machines?
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1) cut mas in half
2) cut focal spot size in half 3) computer chip 4) don't need a step up transformer |
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2 types of interrupted voltage ripples
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1) single phase
-1/2 wave rectified -full wave rectified 2) three phase -six pulse -twelve pulse |
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continuous voltage ripple
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high frequency (ossillator)
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AKA for tube rating chart?
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radiographic rating chart
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for a given mA, any combination of kVp and time that lies below mA curve is SAFE
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tube rating chart (radiographic rating chart)
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Always choose ____ mA for a ______ period of time that's safe.
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-highest
-shortest |
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Why do you want to choose a short amount of time for the xray?
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less pt movement = improve detail
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2 things that the anode cooling chart determins?
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1) maximum heat capacity of anode
2) time required for complete cooling after any level of heat input |
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Density units of measure
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Hounsfield units (HU)
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Equation for HU
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MAS x KV (x 1.4 if high frequency)
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2 AKAs for focal film distance (FFD)
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-tube image distance (TID)
-source image distance (SID) |
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AKA for object film distance (OFD)
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object image distance (OID)
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As the FFD increases...?
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magnification decreases
detail increases |
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As the FFd decreases...?
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magnification increases
detail decreases |
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As the OFD/OID increases...?
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magnification increases
detail decreases |
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As the OFD/OID decreases...?
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magnification decreases
detail increases |
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distance frm xray tube to the image receptor
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focal film distance
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distance from the xray tube to the object being xrayed
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source to object distance (sod)
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distanc from the object being xrayed tothe image receptor
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object film distance (ofd)
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What has the smallest exposure?
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chest
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by angling the anode disc, we can have a larger actual focal spot, but a smaller effective focal spot
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line focus principle
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What happens with a small disc angle?
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-more heat
-more detail |
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aka for penumbra?
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edge effect
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lack of detail, because of the divergence of the rays
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penumbra (edge effect)
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less penumbra on the anode side = ?
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more detail
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What happens with a large disc angle?
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-less heat
-less detail |
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Penumbra in relation to disc angle
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penumbra is larger with the larger disc angle
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radiation intensity on the cathode side is greater than on the anode side
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heel effect
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What causes the heel effect?
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electrons interact with target atoms at various depths into the target
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Extremity placement (except hand and wrist)
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proximal end = cathode side
distal end = anode side |
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When does a patient NOT qualify for a full spine xray?
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->26 cm from to back
-multiple changes in posture -elderly with possible pathologies |
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radiation intensity is inversely related to the square of the distance from the source
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inverse square law
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What happens if you double the distance wth the inverse square law?
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-decreases the intensity by 1/4
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What happens if you cut the distance by 1/2 with the inverse square law?
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-increases the intensity of the xrays 4x
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Where does the primary xray occur?
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in the anode
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Where does the secondary xray occur?
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occurs on objects in the path of the primary xray
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AKA for Bremsstrahlung xrays?
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braking xrays
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created when a projectile electro is slowed by the electric field of a target atom nucleus and then changes direction
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Bremsstrahlung or braking xrays
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What happens if you increase directional change?
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increase energy
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created when an inner electron of the target atom is ejected, and an outer one drops down to stabilize the atom
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characteristic xras
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For tungsten, characteristic xrays occur at what kvp?
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69 kv and above
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What changes bremsstrahlung xrays?
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changing the kv
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inner shell electron gets knocked out
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characteristic xrays
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AKA for primary filter?
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HVL = half value layer
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a permanent flter that removes xrays with energy less than 50 kv (AKA "soft xrays")
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primary filter (Half value layer)
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xrays that get absorbed by the patient are called?
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soft xrays
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What "hardens" the xray beam?
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primary filter (half value layer)
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What reduces the strength of the beam by 50%?
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primary filter
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What is the primary filter measured in?
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mm of aluminum
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What type of filter is permanant and required by law?
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primary filter (half value layer)
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HVL and _______ go together.
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gonadal shields
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What happens when xrays are absorbed?
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free radical production
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a permanent filter that hardens the beam even further. Used in special imaging such as mammography.
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secondary filter
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accommodates the thickness variation of the anatomical part
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compensating filter
-AP thoracic -Lateral thoracic -Lateral lumbar |
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AKAs for classical xra interactions?
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-coherent
-Thompson |
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When do classical xray interactions occur?
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at very low energies (below 10 volts or less)
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3 xray interactions in diagnostic range?
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1) classical=coherent=Thompson
2) compton 3) photoelectric effect |
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What goes off in a 45 degree angle and always deters from image quality?
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scatter radiation
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incident xray interacts with an outer-shell electron and ejects it from the atom
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Compton effect
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source of most of the occupational radiation exposure received by xray techs
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Compton effect
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backscatter radiation caused by what?
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compton effect
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incident xray is totally absorbed during ionization of inner shell electron
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photoelectric effect
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When is the photoelectric effect at a higher rate?
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in denser material
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K shell electron
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photoelectron
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a K shell electron is ejected from the atom
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photoelectric effect
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occurs when there is use of contrast materiels, such as Barium
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photoelectric effect
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xray ejects inner shell electron in patient
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photoelectric effect
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xray ejects inner shell electron in anode disc?
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classica effect
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What do you change first on the xray machine? mas or kv?
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mAs
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What creates more scatter than any other tissue?
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fat
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What is the only view where we go to 90kv?
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lateral lumbar
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What determines penetrating power of xrays?
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speed of electrons
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a 15% increase in kVp = ?
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2x density (like doubling the mAs)
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a 15% decrease in kVp =
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1/2 the density (like cutting the mAs in 1/2
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kVp is ________ to contrast.
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inversely proportional
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As kV increases what happens to contrast?
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decrease
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As kV decreases what happens to contrast?
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increases
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more shades of grey
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low contrast
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What is directly related to density?
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mas
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What does doubling the mas do to the density of the xray?
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doubles it
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blackness of the film
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xray density
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whiteness of the part being xrayed
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object density
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film comes out too light
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-need more mas
-multiply by2 |
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film comes out too dark
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-need 1/2 mas
-divide by 2 |
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total # of shades of gray
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scale of contrast
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Image with lots of contrast has a ________ and __________.
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-short scale of contrast
-narrower latitude (more black to white) |
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Image with a little contrast has __________ and ____________.
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-long scale of contrast
-wider latitude |
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step wedge
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sensitometer
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High contrast? ____ kV
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low kV
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Low contrast? _____kV
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High kV
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High kVp produces?
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1) long scale
2) low contrast 3) less contrast |
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Low kVp produces?
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1) short scale
2) high contrast 3) more contrast |
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Normally, xrays arriving at the image receptor consists of:
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1) transmitted xrays
2) scattered xrays |
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Who invented the grid?
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Gustave Bucky
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When were grids invented?
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1913
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Function of grids
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remove scatter radiation
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How does a grid work?
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transmits only xrays directed on a straight line from the source to the object
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Grid ratio
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height of strip/distance between the strips
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high grid ratio
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-more effective for preventing scatter
-higher the patient radiation dose |
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low grid ratio
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more scatter
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Why do you decrease time of exposure?
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to decrease pt movement to increase detail of the film
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Adding a 10:1 grid ratio will result in a mAs incerase of how much?
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4.5 times
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Function of the bucky
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remove grid line artifact
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Who invented the bucky?
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Hollis E. Potter
-Potter-Bucky diaphragm |
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When do you use the non-grid technique?
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body parts smaller than 8-10cm
-elbows to fingers -knees to toes |
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# of lead strips per inch or centimeter
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grid frequency
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Relationship between grid frequency and patient radiation one.
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the higher the grid frequency the higher the patient radiation zone
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Name the 4 types of grids
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1) linear/parallel grid
2) grid cut off 3) focused grid 4) crossed (hatched) grid |
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the simplest type of grid where all the lead strips are paralll
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linear/parallel grid
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primary xrays cut off from reaching the image receptor
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grid cut off
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lead strips coincide with the divergence of the xray beam with what type of grid?
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focused grid
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2 grid layers with perpendicular lead strips
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crossed (hatched grid
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AKA for air gap
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"Poor man's grd"
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Air gap grids are used with which 3 views?
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1) lateral cervical
2) cervica flexion/extension 3) cervical obliques |
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What is the problem with an off level grid cut off?
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central axis isn't perpendicular to the grid.
partial underexposure |
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What is the problem with an off center grid cut off?
|
xray tube isn't lined up with grid
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What is the problem with an off-focus grid?
|
-xrays taken at SID unspecified for that grid
-the further the gri is from the source, the more severe the grid cutoff |
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What is the problem with an upside-down grid cut off?
|
only about 2" of the center of the film will be exposed
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limits xray beam to required size
|
collimation
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Proof of collimation
|
never exceed film size (needs to b visible on at least 3 sides on the film)
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2 functions of collimation
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1) limits patient radiation dose
2) decrease scatter radiation reaching the film |
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What is the most common beam-restricting device?
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variable-aperture collimator
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What are the 3 factors that contribute to an increase in scatter radiation?
|
1) increased kVp
2) increased xray field size 3) increased patient thickness |
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What do you do when going from a large to a small field of view in the same region?
|
alter mAs keep kVp the same
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What do you do with mAs if cutting the size of the image receptor in 2?
|
increase mAs by 50%
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What do you do with mAs if doubling the size of image receptor?
|
decrease mAs by 50%
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What does increased contract mean?
|
a lot of black and white
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What does decreased contrast mean?
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many shades of grey
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2 kinds of xray timer devices
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1) spinning top test (in dashes)
2) oriental fan method (in degrees) |
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Xray timer devices
|
measure the accuracy of xray timers in half and full wave rectified single phase and high frequency machines
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An exposure of 1/10 s on a single phase full wave rectified would result in how many dots?
|
12
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An exposure of 1/20 s on a single phase full wave rectified would result in how many dots?
|
6
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Equations for spinning top test for single phase
|
120 pulses/second x 1/10 = 12 dots
120 pulses/second x 1/20 = 6 dots |
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Which xray timer device tests single phase machines?
|
spinning top test
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Which xray timer device tests high frequency machines?
|
oriental fan method
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Oriental fan method equations
|
if cylinder spins at 360 degrees per second:
-in 1/10 of a second = 36 degrees on the cylinder -in 1/20 of a second = 18 degrees on the cylinder |
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What tests for timer accuracy?
|
solid state radiation detector
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What operates on an accurate internal clock?
|
solid state radiation detector
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Function of line compensation (high frequency)?
|
to calibrate the kilovoltage
|
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|
keeps a constant voltage automatically since current can vary as much as 5%
|
line compensation (high frequency)
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Where is lne compensation?
|
on operating console
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Minor line compensation button
|
increments of 2
can only turn 5 clicks |
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Major line compensation button
|
increments of 10
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When workig on a single phase machine always set the factors in the following order.
|
1) mA
2) seconds 3) kV |
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device measuring quantity of radiation reaching image receptor
|
automatic exposure control
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flat ionization chamber placed between the pt and image receptor
|
automatic exposure control
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