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Rad CH 7,8,9
Radiographic Imaging
| Question | Answer |
|---|---|
| what is the glass tube made of? | pyrex |
| how much is 220 volts in kvp? | 220,000 kvp |
| which way does energy flow for us?? | - Negative to positive - cathode to anode |
| What is current? | the flow of electrical charge from negative to positive chrage. |
| what is amps? | a measure of electricity. short for ampere. The unit to measure current. |
| what is voltage? | a measure of electricity. determines the speed of electrons (current) |
| kilovolatge peak (kvp) | simplified: determines speed. Measure of the potential difference, which controls the quality and affects the quantity of x-ray photons produced in the x-ray tube |
| isaac newton once said | "an object in motion stays in motion until its stopped by force." |
| What charge is the anode? | positive |
| what charge is the cathode? | negative |
| what does the anode do? | decelerate electrons and redirects it down. |
| what is a photon? | x rays that are produced by electron interactions |
| The primary beam is __% heat, __% x ray, and of that x ray percent, only __% hits the IR. | 99% heat 1% x ray .5% |
| attenuation | when an x ray beam loses energy while passing through tissue or other materials |
| what is a photon? | x rays that are produced by electron interactions. |
| IR | image receptor. it receives the signal. |
| primary beam | a powerful beam that comes out of the tube, and stays primary till it hits an object. |
| another word for polyenergetic | heterogenous |
| remnant beam | the beam after hitting the object that goes to the IR. we get our image from this |
| 3 types of attenuation | scatter, absorbed, transmitted |
| scatter | Low energy, very destructive. It increases patient dose, damages us, and impacts image negatively. |
| absorption | |
| ionization can result in | biological effects |
| 2 sources of ionizing radiation | natural man-made |
| examples of natural radiation? | cosmic radiation, uranium, radium |
| examples of man made radiation? | nuclear energy, radionuclides, medical x rays, dental x rays |
| what is man-made radiation known as? | artificial radiation |
| what is natural radiation known as? | background radiation |
| where does most man-made radiation come from? | medical and dental x ray |
| what is needed for x ray production? | 1. source of electrons 2. means for setting them in high speed motion 3. mechanism for decelerating them abruptly. |
| where is the target? | anode. the electrons aim for the target. |
| unit for cathode filament? | mA |
| unit for potential difference? | kVp |
| what is a diode? | |
| what type of tube is the x-ray tube? | it is a diode tube? |
| what maintains a vacuum? | the glass envelope |
| kiloelectron volts (keV) | units of energy equal to 1,000 electron volts |
| the x ray beam is ____ and the energy of the beam is expressed in ___ | heterogenous ; kev |
| the beam leaving the tube that is directed toward the patient | primary beam |
| the beam can undergo what paths after striking matter? | 1. total absorption 2. pass through with no loss of energy 3. undergo scattering and 2nd degree interactions with same loss of energy |
| what are the x ray interactions with matter? | 1. classic coherent scattering 2. Compton scattering 3. photoelectric interactions 4. pair production 5. photodisintegration |
| most important interactions in diagnostic radiography | - photoelectric - Compton |
| classic coherent scattering | Interaction with matter where a low-energy photon (below 10 kiloelectron volts) is absorbed and released with its same energy, frequency, and wavelength but with a change of direction. |
| in classic coherent scattering, the atom gets excited and | emits an x ray with the same energy |
| in classic coherent energy, how much energy gets is transferred to the patient or matter? | none |
| is classic coherent scattering ionizing? | classic coherent scattering is non-ionizing because it does not remove the electron. |
| photoelectric interaction effect | contributes to the image. has to be 70kVp or higher. a photon strikes an inner shell electron, causing its ejection from orbit around the nucleus of an atom with the complete absorption of the photon’s energy. this creates an ionic pair. |
| what is diagnostic x ray? | |
| where does photelectric interactions occur? | photelectric interactions occurs within the diagnostic energy range. |
| what is the octet rule? | |
| in photoelectric effect, as a result of electron cascade release energy in the form of x rays, what is created? | characteristic radiation |
| what interaction is the greatest hazard for patients in diagnostic radiography? | photoelectric effect. |
| compton scattering | higher energy photon strikes a loosely bound outer electron, removing it from its shell, and the remaining energy is released as a scattered photon |
| recoil electron | when a portion of the energy in an outer shell electron creates a free Compton electron. |
| what does the recoil electron do? | it loses electrons through collision and scatters off in random directions, undergoing other interaction as it travels. |
| in Compton scattering, how fast is an electron vacancy filled? | instantly. |
| what absorbs Compton and why? | lead absorbs Compton because it is low energy. |
| pair production | pair production requires very high energy phtons of at least 1.02 MeV of energy. the incoming photon reacts to the nuclear force field around the nucleus and disappears. mainly used in NucMed |
| MeV | maximal extractable value |
| Positron Emission Tomography (PET) | The creation of sectional images of the body that demonstrate the physiologic function of various organs and systems. |
| positron | positively charged electrons |
| negatron | electron with a negative charge |
| in pair production, a positron and negatron will emerge w how much energy? | 1.02MeV (.51 energy) |
| what does an annihilation reaction do? | create 2 photons at opposite directions |
| photodisintegration | x ray photons with a minimum of 10 MeV interacts with the nucleus of an atom causing a state of excited instability. |
| where does photodisintegration occur? | RadTher. not in medical imaging. |
| in photodisintegration, a nuclear fragment is emitted to | to bring electrons to the nucleus. |
| 3 facts about the International System (SI) of Units | 1. based on metric measurement. 2. developed in 1948. 3. units used to measure radiation |
| what are the SI units of measurement? | 1. Roentgen 2. Gray 3. rem 4. air kerma 5. becquerel (used to be curie) |
| roentgen | measure of exposure in air as a result of exposure to x/gamma rays |
| roentgen is measured in | coulombs per kilogram (C/Kg) 2.58x10^-4 C/Kg |
| Gray (Gy) | radiation absorbed dose. measures the amount of radiation absorbed in any medium. 1 Gy = 100 radiation absorbed doses (rad) |
| Radiation equivalent man (rem) | unit of dose for sievert. accounts for different types of radiation and their biguality factor. |
| sievert (Sv) | Unit used to measure the dose equivalence, or biologic effectiveness, of differing radiations; 1 Sv = 100 rem |
| rem accounts for different types of radiation and their | biquality effects |
| rem particles and rem bundles of energy | rem particles: alpha, beta bundles of energy: x-ray, gamma |
| rem is also referred to as | quality factor |
| air quanityt | used to measure energy transferred from radiartion to a material |
| kerma meaning | kinetic energy released in matter |
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