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X-Ray tube anatomy
| Question | Answer |
|---|---|
| What is the purpose of the X-Ray tube? | To produce a controlled x-Ray beam |
| What two things are controlled manually when the machine is set? | The amount of x-rays produced (# of x-Ray photons produced) and the penetrating power of x-rays (mean energy of the x-Ray photons) |
| What controls the number of x-Ray photons produced? | The milliamperage (mAs) |
| What controls the penetrating power of the x-rays? | Kilovoltage peak (kVp) |
| What happens to the x-Ray beam when the kVp is increased? | The energy, wavelength, and penetrating power increase |
| 5 things needed for the production of x-rays | The source of electrons (mA), the method of accelerating the electrons (kVp), a vacuum environment, a target to hit (for electrons), and a physical means of dissipating heat. |
| Diode | The x-Ray tube. |
| The two parts of the diode? | Cathode and anode |
| What is the charge of the cathode and anode? | Cathode-negative charge Anode-positive charge |
| What surrounds the diode? | A glass envelope which forms a vacuum |
| Where do electrons interact to produce x-rays? | At the anode |
| Purpose of the cathode | Source of electrons, focus and direct electrons towards target(anode) |
| The two major parts of the cathode? | Filament and focusing cup |
| Structure of the filament and what is it composed of? | Coiled tungsten wire |
| Why is filament made of tungsten? | Has a high melting point and is more resilient (less likely to burn out). |
| Why is it important for tungsten to have a high atomic number? | The higher the more electrons available to generate an electron cloud. |
| How many filaments can be found in the cathode of a large stationary machine? And a small portable one? | Large-two Small- one |
| What size is the focal spot associated with a short filament? Long filament? | Short-small focal spot on the anode Long-long focal spot on the anode |
| What happens to the number of electrons produced as the mA is increased? | the number of electrons is increased |
| What is the focusing cup composed of? Why is it important? | Molybdenum. It has a high melting point that does not conduct heat, and is negatively charged (not gonna spread out). |
| What is the purpose of the focusing cup? | It directs (focuses) the electron cloud toward the anode. |
| What is the target of the anode composed of? Why? | Tungsten because it has a high melting point. |
| What is the base of the anode composed of? Why? | Copper because it has a high melting point and conducts heat well. |
| the two types of anodes | Stationary and rotating. |
| In what type of machine is a stationary anode found? | portable x-ray units or dental units. |
| Advantages or disadvantages of a stationary anode? | Ad-no moving parts, smaller, portable, durable Dis-Overheating |
| In what type of machine is a rotating anode found? | stationary (non-portable) x-ray machines. |
| what is the construction of the rotating anode? What is the disk composed of? the spindle? | heavy tungsten disk with a beveled edge (target are), molybdenum spindle. |
| why is the spindle composed of molybdenum? | it protects vulnerable parts of machine. |
| why is it important for the rotating disc to rotate? | It provides a cooler surface for the electron stream to strike. |
| what are the advantages and disadvantages of the rotating disc? | ad- higher surface area of target, better heat dissipation, more x-rays produced. dis-more expensive, and more easily damaged. |
| What is the focal spot of the anode? | area of the target where electrons collide and x-rays are generated. |
| Which size effective focal spot produces the best detail on the radiograph? | the smaller effective focal spot. |
| Which focal spot relates to the ability of the machine to handle heat? | the actual focal spot |
| which focal spot can be seen when you look up into the x-ray tube? | effective focal spot |
| Heel effect | a variation in intensity of the x-ray beam emitted from the x-ray tube. |
| Which end of the x-ray tube is the beam the strongest? | the cathode end. |
| How can you take advantage of the heel effect? | can use to get "balanced" radiograph of different tissue densities or thickness. |
| Tube envelope | surrounds the anode and cathode usually made of glass |
| what is another name for the tube envelope? | glass envelope. |
| What is the function of the tube envelope? | prevents collision of electrons with air molecules, prevents oxidation of mechanical parts, and forms and maintains the vacuum. |
| What is the tube housing? | Heavy metal case that protects and supports the tube. |
| What is the tube housing lined with? why? | lead, it is inherent filtration so it absorbs stray radiation. |
| What is attached to the exit port of the tube housing? | the beam limiting device (collimator) |
| what is the purpose of the oil found in the tube housing? | provides electrical insulation, cooling of tube by convection, and more inherent filtration. |
| Steps of x-ray production |
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vanessaxoxox50