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Ch 6 Rad 150
The X-Ray Tube
| Question | Answer |
|---|---|
| The filament is located on the ____ side and "boils off" _____. | cathode; electrons |
| The filament is made of which material and why? | thoriated tungsten - high melting point - 3400 degrees C. |
| The smaller the focal spot the ____ the effective beam. | smaller |
| The large surface area on a rotating anode is made to dissipate ____. | heat |
| A small focal spot will give an image better ____ _____. | spatial resolution |
| The large focal spot is used when large body parts are imaged and with techniques that produce ____. | high heat |
| What is the ratio for heat and x-ray production? | heat 99% - xray 1% |
| What are three components located on the anode side? | anode, rotor and stators |
| During the anode heel effect more radiation is absorbed on the ____ side. | anode |
| What is an example of the anode heel effect? | x-ray of the foot |
| The metal casing around the tube protects against ___ and ____ and also dissipates ___. | electric shock, radiation leakage; heat |
| Thermionic emission is the boiling off of ____ from the filament. | electrons |
| During the ____ ____ ___, subsequent electrons can not be emitted by the filament because of electrostatic repulsion. | space charge effect |
| Exceeding the ___ ___ will result in the space charge effect. | saturation point (overproduction of e-) |
| Voltage is also known as ___ _____. | potential difference. |
| To produce photons, a ____ is needed to keep x-ray efficiency at 1%. | vacuum |
| ____, ____, and ____ can be used to make filaments. | Tungsten, molybdenum and rhodium |
| Tube warm-up is important to prevent the ___ from breaking. | anode |
| During off-focus radiation, electrons miss the ____ and land on different areas of the target. | focal spot |
| What are the heat units (HU)? | single - 1; 3 phase/6 pulse - 1.35; 3 phase/12 pulse and HF - 1.4 |
| The ___ focal spot size are the e- that hit the patient after it interacts with the target. | effective |
| The ___ focal spot size are the electrons hitting the anode target. | actual |
| The ___ ___ is the actual x-ray source. | focal spot |
| The ___ ___ principle results in an effective focal spot size much less than the actual focal spot size. | line-focus |
| What are the primary components of the tube? | glass envelope, cathode, anode and tube housing |
| The focusing cup is made of ____. | nickel (negatively charged) |
| The smaller the target angle, the ____ the effective focal spot size. | smaller |
| ____ causes tube failure, glass cracking and lose of vacuum. | Arcing |
| Vaporized tungsten will cause photons to be ____. | attenuated |
| External components of the tube include: | housing, glass envelope and induction motor. |
| Internal structures of the tube include: | anode and cathode |
| What kind of chart gives the amount of time needed for the anode to cool down? | Anode cooling chart |
| Protective housing reduces level of rad leakage to less than ____ mR/hour @ __ m. | 100;1 |
| When x-rays are produced, they are emitted ____. | isotropically |
| The tube window contributes to ____ filtration. | inherent |
| The longer the exposure, the more ___ that is produced. | heat |
| Which chart determines safe and unsafe techniques? | tube rating chart |
| Current in each stator winding induces a magnetic field that surrounds the ____. | rotor |
| The rotating ____ is powered by an electromagnetic induction motor. | anode |
| The glass thickness that surrounds the window is ____ al/eq | .5 mm |
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