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fosbinder 5 &6
radiation discovery, X ray tube, x ray production
| Question | Answer |
|---|---|
| who is the father of x-ray? | welhelm conrad roentgen |
| when did he discover x-rays? | november 8 1895 |
| Roentgen was working with what kind of tube when he discovered x-rays? | crooke's tube |
| text book definition of flouresence | The instantaneous production of light resulting from the type of energy. |
| when were biological effects seen? | 1898 -erythema -alteration of chromosomes |
| what year was the 1st nobel prize given for xray in physics | 1901 |
| define - electromagnetic radiation | radiation that has both electrical and magnetic properties |
| define - electromagnetic spectrum | energy can generally be described as behaving according to the wave concept of physics or the particle concept of physics. |
| define - x-rays have a dual nature | they act as waves and as particles |
| where are x-rays found on the electromagnetic spectrum | on the higher end of the electromagnetic spectrum. second highest below gamma rays. |
| electromagnetic spectrum in order. highest -lowest | -gamma rays -xrays -ultraviolet -visible light -infrared - micro waves -radio-frequency |
| define - wavelength | The distance between each crest of trough |
| define - frequency | The number of waves passing a given point |
| What is the relationship between wavelength and frequency | inversely proportional. As wave length increases, frequency decreases |
| How do x-rays behave? | x- rays behave as particles and move as photons or quanta. |
| define - photon/quantum | A small discrete bundle of energy. |
| Energy of an individual photon is expressed in units of..... | kiloelectron volts (kev) |
| characteristics of x-rays (14 total) 1-5 | 1.They are invisible 2.They are electrically neutral 3.They have no mass 4.They travel at the speed of light in a vacuum 5.They cannot be optically focused |
| characteristics of x-rays (14 total) 6-9 | 6.They form a polyentergetic beam. or heterogenous beam 7.They can be produced in a range of energies 8.They travel in a straight line 9.They can cause some substances to fluorescence |
| characteristics of x-rays (14 total) 10-14 | 10.They can cause chemical changes in radiographic and photographic film. 11.They can penetrate the human body 12.They can be absorbed or scattered in the human body 13.They can produce secondary radiation 14.They can cause damage to diving tissue. |
| define- x-ray production | x-ray production requires a rapidly moving stream of electrons that has either accelerated or stopped |
| 3 characteristics of the Cathode | 1.negative electron. 2.source of e- 3.contains filaments and a focusing cup |
| define- filaments | Coiled tungsten wire that, once heated is the source of e- for x-ray production . |
| define- dual focusing cup | tubes that have 2 filaments (small & large) |
| focusing cup | made of nickel and has a negative electrical charge to keep e- produced from filament from spreading apart. used to focus stream of e- |
| 4 characteristics of the anode | 1.Positively charged electron 2.Rotating or stationary 3.Consists of a target 4.Rotating anodes consists of a rotor and a stator |
| rotation speeds for the anode | 3,000-10,000 revolutions per minute (RPM'S) to help reduce heat on target (single phase= 3,000) |
| target | part of the anode that decelerate or stops e- in tube current and allows production of x-rays. |
| what is the target made of? | 90% tungsten and 10% of rhenium |
| Why tungsten? | -high atomic # and melting point of 3370 |
| what is the base for the target made of? | tungsten rhenium alloy is a layer or track that is embedded in a base of molybdenum and graphite |
| How much is the face of the target angled? | 6-20 to help x-rays exit the tube |
| 5 parts of the anode | 1.target 2.stator 3.rotor 4.anode stem 5.actual focal spot |
| define- stator | electric motor that turns rotor at high speeds |
| define- rotoe | rigidly connected to target and anode stem |
| define- anode stem | allows heat to be transferred from target anode. |
| define- actual focal spot | physical area of target that is bombarded by e- |
| name the 2 types of anodes | 1.stationary 2.rotating |
| stationary anode | -fixed focal spot -can't withstand high heat loads like rotating anode |
| rotating anode | -focal track -can withstand high heat load because of roation |
| 3 parts of tube housing | 1.glass envelop 2.insulating oil 3.metal tube housing |
| 4 purposes of the glass envelop | 1.houses tube structure 2.air is evacuated 3.provides insulation from electrical shock 4.dissipates heat |
| 3 purposes of insulating oil | 1.surrounds glass envelop 2.provides insulation from electrical shock 3.dissipates heat from tube |
| metal tube housing | completely surrounds everything except for a port (window) that allows primary beam to exit . -what the radiographer manipulates -lined with lead to prevent leakage radiation |
| leakage radiation | any x-rays (other than primary beam) that escape the tube |
| maximum amount of leakage radiation allowed | leakage radiation cannot exceed any more than 100mr/hr at 1 meter from the source while the tube operates at maximum output |
| what is the tubes power source? | 2 electrical connect the high voltage generator to the tube housing. 1 for the cathode and 1 to the anode |
| define- deadman switch | button must be help down for the entire exposure for the exposure to be complete |
| what are the 2 types of exposure buttons? | one button and 2 separate buttons |
| what happens when the rotor button is depressed? | causes the selected filament to warm up and the stator of the anode to turn. |
| filament current | depends on the amount of mA set at the control panel |
| define- thermionic emission | boiling off of e-. when the tungsten filament gains enough heat, the outer shell e- of the filament atoms boil off or are emitted from the filament. |
| define- space charge | e- release from the tungsten atoms that sit in a group just beyond the filament. since all like charges naturally want to repel each other the negatively charged focusing cup kep then all together. |
| what happens to the stator when the rotor is depressed? | begins to drive the rotor to turn the anode. |
| what happens to the cathode when you depress the exposure button? | cathode becomes "super charged" with a negative charge and shoots e- to the anode at a speed corresponding to the kvp set on the control panel |
| what happens to the anode when you depress the exposure button? | the anode becomes "super charged" with a positive charge to attract the e- |
| 2 types of x-ray production | 1.bremsstrahlung 2.characteristic |
| define- bremsstrhlung interaction | the e- loses energy and changes direction. the energy lost reappears as an x-ray photon. |
| define- characteristics interaction | an e- from the cathode knocks a K shell e- out of its orbit and all other outer shell e- move down to occupy the vacancy. As e- are displaced, x-rays of varying energies are produced. |
| during characteristic interactions what is the minimum energy needed to knock out a K shell e- | 70 kvp |
| what is the energy conversion of x-rays | 99% thermal energy (heat) and 1% electromagnetic energy (x-ray) |
| what is x-ray quantity? | number of x-rays produced |
| what is x-ray quality? | penetrating power of x-rays |
| what defines mA? | the tube current is the # of e- flowing per unit of time from the cathode and anode. mA is directly proportional to the amount of energy. controls quantity. |
| exposure time | length of time tube current flows from cathode to anode. changes in time produces same effect as changes in mA. |
| kvp | the speed of e- traveling from cathode to anode increases as kvp increases. influences quantity |
| line focus principle | tilting the anode surface so there is an angle between the surface and the x-ray beam spreads the heat over a larger area while maintaining a smaller focal spot for sharer images. |
| target area | the size of the area on the anode target that is exposed to e- from the tube current. |
| what effect does the size of the filament have on the target? | large=withstands more heat small= produces more detail |
| effective focal spot size | focal spot size measured directly underneath the anode target |
| what is the range an anode can be manufactured? | 6*-20* |
| anode heel effect | Occurs due to the angle of the anode. The cathode side of the tube has more x-rays of higher penetrating force than the anode side because the get absorbed by the anode. |
| how much of x-ray production is heat? | 99% |
| equation for heat units (HU) | HU=mA X Time X Kvp X GF |
| generator factor for single phase | 1.0 |
| generator factor for 3 phase 6 pulse | 1.35 |
| generator factor for 3 phase 12 pulse | 1.41 |
| generator factor for high frequency | 1.45 |
| What are tube rating charts used for? | used to determine if particular exposure is safe to make (determine limits of mA, kvp and time).guidelines must be heeded or else result in permanent damage. |
| What does a anode cooling chart show? | shows the minimum amount of time required for the anode to cool. |
Created by:
lchadderton
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