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RAD6608 Test 1
| Question | Answer |
|---|---|
| who discovered the first xray.. and when? | Wilhelm Conrad Roentgen, in 1895. |
| What were three early uses of x-ray? | 1. dermatology (psorasis, ringworm). 2. hair restoration. 3. shoe fitting |
| What are 6 new imaging modalities? | 1. CT 2. MRI 3. US 4. DEXA 5. Nuclear medicine 6. PET |
| What are 4 other uses of x-rays? | 1. xray crystallography (DNA structure). 2. cosmic research 3. airport security 4. heavy equipment testing |
| What are two types of radiation types? | 1. particulate and 2. electromagnetic |
| What is particulate radiation and what is it used for? | alpha, and beta... used for nuclear medicine (BONE SCANS) |
| What are two types of electromagnetic radiations? | 1. xray and 2. gamma |
| What is xray used for? | for radiography and CT |
| what is gamma used for? | used for nuclear medicine (bone scan) |
| visible light acts more like a ____, and xrays act more as a ____ | visible light acts more as a wave and xrays act more as a particle |
| What are 4 atomic models... and the one we use most? | medieval, dalton, thompson, and BOHR is the number one |
| Describe the Bohr atom | nucleus with electron cloud with different energy levels (shells) |
| What electron shells are the most important for xray? | K and L (inner two rings) |
| electron binding energy is dependent on what/. | the type of element |
| More electrons = ____ binding energies | higher |
| x-ray photons travel at what? | the speed of light |
| in the equation C=(f)(lambda),what are each of the varibales? | C= velocity, f = frequency lambda = amplitude |
| In the equation C=(f)(lambda) what can be modified and what cannot be changed | C (velocity) cannot be changed, and lambda (amplitude) can be modified |
| What is photon energy directly proportional to | frequency |
| what is photon energy inversely proportional to? | wavelength |
| xray energy units is measured in what | electron-volts (eV) |
| strength of xray energy units is relative to what? | kVp (keV) |
| the field contains all strengths from ____ -- )____ setting | 0-kVp setting |
| <10 kVp is what? | crystallography |
| 10-20 kVp is what? | dermatology |
| 30-150 kVp is what? | diagnostic imaging |
| 200 kVp - 1 MVp is what? | radiation therapy |
| 1 Mvp is what/ | industrial xray |
| Xray charactistic moves at what? | C, the speed of light |
| x-ray characteristic have no what and what | no reflection and no refraction |
| xrays are unaffected by what? | by electric or magnectic fields |
| what do xrays affect? | photographic emulsion |
| what can xrays ionize? | matter (i.e DNA) |
| SID? | source image distance |
| FFD? | focal film distance |
| TFD | target film distance |
| SOD | source object distance |
| OFD? | object film distance |
| OID? | object image distance |
| which three acronyms are the same distance?? | SId (source image distance), FFD (focal film distance) and TFD (target film distance) |
| What two acronyms are the same? | OFD (object film distance) and OID (object imagine distance) |
| Which films are established @ 40 inches for SID/FFD/TFD? | AP cervical, apom, thoracic, lumbar, extremities, and abdomen |
| which films are established @ 72 inches for SID/FFD/TFD? | lateral cervical, chest, full spine |
| What is the inverse square law? | that as the distance from the source to the image receptor increases, the radiation intensity decreases by the square of the distance. |
| what can the inverse square law be measured in? | R, rem, or mAs |
| What is the formula for the inverse square law? | I1/I2 = D2^2/d1^2 |
| What happens to the kVp with inverse square law? | stays the same, it does not change. |
| @ 10 feet away from the source, your dose is <__% of the original beam | 1% |
| what four things electricity wise does xray require? | kilovoltage, milliamperage, as well as volts and amps |
| how much volts does xray work @? | 220 V |
| electric current is induced if the circuit is in what? | a changing magnetic field |
| Using ______ the 60Hz frequency of household current creates a _____ magnetic field | using electromagnets the 60hz freq of household current creates a changing magnetic field |
| What is a transformer? | a wire coil wrapped with iron core which induces a magnetic field |
| What is a step up transformer? | More coils at the secondary side which increases the voltage |
| What is a step down transformer? | less coils on secondary side which decreases the voltage |
| What is the relationship between step up/down transformers and amperage? | inversely related |
| What is an autotransformer? | a single winding, used for small increases or decreases in voltage. |
| What is an autotransformer used for? | line compensation, since voltage can vary with other electronic use. (helps regulate voltage) |
| which part of the xray has the autotransformer? | the operating console. |
| what is the operating consol used to regulate? | used to regulate the line voltage to precise standards |
| what does the operating console increase d/t the autotransformer? | increases consistency of the xray beam |
| What does the kVp control in regards to the xray beam? | the QUALITY and QUANTITY of the xray beam (powder of in a shotgun shell) |
| how much does kVp move with kVp major? | 10 kVp per click |
| how much does kVp move with kVp minor/ | 1 kVp per click |
| the reading in the console of the kVp is actually what> | volts |
| What does the mAs control of the xray beam? | just the QUANTITY (shot in a shotgun shell) |
| What is the equation for mAs? | mA x time |
| What must always be set first on the old single phase machines? | ALWAYS the mAs (b/c it changes the resistance) |
| what are the 3 factor settings? | kVp, mA and time |
| what are the 2 factor settings? | kVp and mAs |
| What important factors are set on the operating console? | large vs small focal spot, receiver selection (wall or table), rotor, and expose buttons. |
| What is the expose button aka? | deadman switch |
| What does the rotor button do? | Rotor button is pressed before the expose/deadman switch. It spins rotor up to speed. |
| What is an important rule about the expose button? | must hold button for the entire length of exposure. |
| What are the values of the syncronous timer, and what hz does it use? | all values are factors of 1/60, and timer uses the 60hz of supplied power for timing |
| What is the electronic timer? | digital circuitry for timing, with better control. |
| What is AEC timer? | Automatic Exposure Control......... ionization plate "reads" the # of photons striking the target and shits off the exposure when its sufficient. |
| What is the high voltage generator used for, and what type of transformer is it? | used to create the high kVp needed for xray production, and is a step up transformer. |
| what does the transformer control with the volatge? | the amplitude/size |
| High voltage generator wall and transformer electricity vs. xray requires what? | wall & transformer is AC, and xray is DC (direct current) |
| What is high voltage generator electrical requirements solved with? | rectification |
| Ac vs Dc direction? | AC is bidirectional while dc is unidirectional which ensures current only travels in 1 direction using diodes |
| what does rectification half wave use? | 2 diodes, which is wasteful b/c only half of the electrical current is used |
| what does rectification of a full wave use? | a diode bridge//salt bridge (4 diodes) which uses the entire waveform. |
| what does the full wave cut in half | cuts exposure time in half compared to the half wave |
| where in the electrical wave are xray photons produced? | peak of electrical wave |
| the leading and finishing portions of the wave produce ___ quality xrays | low |
| single phase power electrical wave forms @ ___hz produce what? | @ 60 hz produce substantial amount of of low quality xray photons |
| What does three phase power of electrical wave forms produce? | 3 60 hz waveforms - 180 hz effectively, therefore fewer low quality photons |
| What hz are high freq. electrical wave forms @? | 500-25000 hz |
| what does high freq electrical wave forms require and result in? | requires more electronics, and results in a smaller generator footprint. |
| high freq. electrical wave forms are more or less efficient? and offer ____ quality radiation | more efficient and offer higher quality radiation |
| capacitor discharge generators aka? | battery operated |
| what does capacitor discharge generators allow for? and have a large what? | allows for high freq generation from 60 hz 110 V wall outlet to xray.... but has a fairly large generator footprint |
| What is the % voltage ripple of single phase, 1/2 and full wave rectfied? | 100% ripple |
| what is the % voltage ripple of three phase? | 4-14% |
| what is the voltage ripple of high freq.? | <1% |
| ripples effects what with the xray beam? | the quality of the xray beam |
| decreased ripple results in _____ quality of the xray? | higher quality |
| lower quality phtons only contribute to ______, not effective ____ info | contribute to pt dose, not effective xray info |
| how are xray unites rated? | in kW |
| what are most xray units in kW.... and some are? | most are 30 kW... some are 50 kW. |
| what does wattage = | max mA @ 100 kVp and 100 ms |
| single phase units only produce ___% of the wattage of an equivalent high freq machine d/t ____ | 70% d/t ripple |
| What are 3 dif tube types? | 1. crookes tube. 2. cooldige (fixed anode) tube. 3. modern (rotating anode tube) |
| shoot from the ____ to the ____ | cathode to the anode |
| does the anode or cathode create photons when electricity hits? | anode |
| how does the xray tube housing prevent widespread irradiation? | by isotropic formation of radiation |
| xray tube housing also prevents what, and aid in? | prevents electric shock and aids in tube cooling. |
| xray tube is made out of??? | evacuated pyrex or metal |
| xray tube must be a _____ | vacuum |
| the xray tube has a thinner section of glass called the _____, which decreases ___ ____ | called the window, which decreases photon absorption |
| Cathode aka? | filament |
| cathode/filament side creates what? | electron beam |
| most tubes are dual filament, with what? | with a large (2 mm) and small (1mm) focal spots |
| large focal spots for? | for larger body parts |
| small focal spots give better??? | resolution/detial |
| what are filaments made out of? | thoriated tungsten (W, wolffram) |
| thoriated tungsten has a ____ melting point, and ____ thermal expansion, and ____ vaporization | high melting point, and minimal thermal expansion, and minimal vaporization |
| what does vaporization do? | coats the inside of the tube, which leads to arcing, filament thinning and eventual tube failure. |
| filament current heats the ____ | filament. |
| what is thermionic emission? which results in? | electrons are boiled off (the filament), which results in an electron cloud around the filament. |
| what creates the space charge effect? | electron cloud from thermionic emission |
| what is the space charge effect? | hard to get additional electrion boiled off d/t the high negatie change in the cloud, and unguided the e-s would fly all over the tube, d/t inherent repulsion. |
| focusing cup on what side of tube? | cathode side. |
| focusing cup// ?? | Ni |
| what does the focusing cup// ni do? | directs the e- cloud in a linear fashion toward the anode because it is negatively charged |
| Anode aka? | target side |
| anode receives? and creates? | receives e- beam and creates xray phtons |
| in what units does the anode rotate? | in chiro/med xrays units and ct scanners |
| where are stationary anode tubes found? | dental xrays |
| what are three functions of the anode? | 1. electrical conductor 2. mechanical support 3. ***thermal dissipater. |
| what % of energy from xray is convereted into heat? and what % og lectrical energy produces photons? | >99% goes to heat, <1% produces photons |
| what are the materials used for heat dispersal? | tungsten target, molybdenum base and shaft, and graphite backing. |
| what movement helps in heat dispersal? and how so? | rotation which increases the surface area over a stationary anode by 500x |
| ____ RPM increases heat dispersal | 3600 RPM |
| how does angling the target disperse heat? | increases the surface area hit by e-s, and ****decreases effective focal spot size. |
| another method of heat dispersal is _____ in the tube housing | oil bath |
| line focus principle attempts to make a _____ which is _____ | attempts to make a POINT SOURCE which is physically impossible. |
Created by:
margaretrhager
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