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the tube
| Question | Answer |
|---|---|
| how fast do e- travel from cathode to anode | half the speed of light |
| kVp vs kEv | kVp- energy of the beam kEv- energy of the individual photon or the projectile electron |
| characteristic radiation | like photoelectric but inside the tube. emits an e- instead of a photon. |
| only _ shell interactions are significant for imaging | K |
| A projectile e- needs a minimum of ______ to produce characteristic radiation | 70 kVp |
| At 70+ kVp, what % are the interactions in the tube? | 15% characteristic and 85% Bremsstrahlung |
| Brem radiation is aka | braking radiation |
| Bremsstrahlung interactions | an incident e- is slowed down as it nears a positively charged nucleus and changes direction. losing some energy |
| In Brem interactions, ___ energy is converted to ___ energy | kinetic to x-ray energy |
| most of the Brem xrays are __ energy in the ___ range | mid energy; 20-150 kVp range |
| Less than 70 kVp, what interactions are occurring in the tube | 100% Brem |
| which interaction has a continuous x-ray spectrum Which has a discrete spectrum | Brem Characteristic |
| what is the image contribution for Brem vs characteristic | Brem- most of diagnostic xrays characteristic- minimal but crucial for contrast |
| what is shown in an xray spectrum | graph of the xray photon quality (x) vs quantity (y) |
| the amplitude of the x-ray spectrum shows | intensity/# of photons |
| the y axis of the xray spectrum shows | photon energy kEv/position |
| increase in mA will shift the x-ray spectrum | up in amplitude. no affect on L/R |
| increase in kVp will shift the x-ray spectrum | right and up |
| Increasing filtration of the beam shifts the x-ray spectrum | down in amplitude and to the right. hardening the beam decreases quantity but increases quality |
| How does changing the target anode materials from tungsten to molybdenum affect xray spectrum | the lower z number of molybdenum creates lower energy photons and thus lowers the spectrum in amplitude and position |
| a higher waveform generator will move the x-ray spectrum | to the right and up |
| the xray spectrum will increase in kVp by _____ % when using 3P or HF vs using 1P | 12-16% |
| formula for Heat Units | HU= mA x time x kVp x generator factor |
| generator factor for single phase, 3phase 6P, 3 phase 12P, hF | single phase- 1.0 3 phase 6p- 1.35 3 phase 12 P- 1.41 High frequency- 1.41 |
| the tubes protective housing can be made of | glass or metal |
| the focusing cup is made of | nickel and copper |
| the filament is made of | thoriated tungsten |
| general purpose xray units will not exceed ____ mA special tubes can get to | 1000 2000 mA |
| filament life | 6-9 hours. 10,000-20,000 exposures |
| stationary anodes are use din | portables and dental xrays |
| general purpose tubes have ___ rpm of the anode | 3,400-3,600 |
| the anode is composed of | tungsten and rhenium |
| a smaller target angle will make the image | sharper |
| anode cooling charts show the | anode cooling over time |
| the blooming effect | when high mA settings cause the beam in the tube to expand. lowers resolution. |
Created by:
user-1989152