Term
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Definition
| Isotopes will release energy and matter form their nucleus and often transform into a new element. |
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Term
| What is the equation for Half-Life? |
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Definition
At=A0e-λt
where decay constant is found by
λ=loge(2)/t1/2
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Term
| What are the main particulate radiation resulting from radioactive decay? |
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Definition
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Term
| The electromagnetic ionizing radiations resulting from radioactive decay are called what? |
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Definition
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Term
| What results from ISOMERIC Transition? |
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Definition
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Term
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Definition
| A positively charged electron and its also an anti matter |
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Term
| When converting Carbon-11 to Boron-11 what is essentially happening? |
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Definition
Carbon-11==>
Boron-11+positron+neutron |
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Term
| PET scans use Carbon, nitrogen, oxygen and F because? |
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Definition
| THey all go through beta decay and emit positrons and because they are abundant through the body (biochemistry) |
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Term
| What is a meta-stable state? |
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Definition
The particle is actually an isomer as it has the same mass number and atomic number. The particle will release energy in the form of gamma photons
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Term
| Isomeric Transition is what? |
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Definition
releasing the energy in the form of a gamma ray photon
Here the energy level depends on the element involved. |
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Term
| When a positron collides with an electron, the 2 particles _____ eachother and produces 2 photons traveling in _____ direction |
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Definition
annihilate
opposite directions |
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Term
| The most common tracer compound is ___ |
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Definition
18F
fluerodeoxyglucose
used for glucose metabolism
glucose consumption and to detect different glucose metabolic rates |
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Term
| Positron decay or postron emission happens when a single positron reacts with an electron through annihilation produces ___ |
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Definition
2 gamma rays ( 2 photons) each at 511 keV AS ALWAYS
we get 511 keV from E=mc2 |
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Term
| PET uses a gamma emitter. What is this? |
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Definition
| Gamma emitter is the transofmration associated with the emission of a photon of a precise energy |
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Term
| SPECT uses a beta plus emitter, what is this? |
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Definition
| the transformation is associated with the emission of positive positrons of variable energy. The positrons will slow down and collide with negative electrons of the medium |
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Term
| What is the photon detector inside PET? |
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Definition
| 2 photons are detected simultaneously so it is know that the annihilation point is on teh line joining the 2 detected points |
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Term
| What is the photon detector in a SPECT? |
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Definition
| a single photon does not bear information about its direction when it hits the crystal |
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Term
Basic steps for PET aquisition?
Detectors pick up ___ as ___
Pulses go rthough a timing component to aquire____
Timing signals from the pick off unit are passed to a ___ which ___. |
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Definition
Detectors pick up photons as pulses
Pulses go though a timing component to aquire correct timings on pulses.
Timing signals from the pick off unit are passed to a gate generator whichgenerates a gate of width τ
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Term
| What is a scintillation crystal? |
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Definition
| This part of the scintillation camera is responsible for the detection of gamma rays and it also converts them into actual photons of light. |
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Term
| What kind of crystals did the original scintillation camera use? |
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Definition
| The initial anger scintillation camera used scintillation crystals made of sodium-iodide (NaI) |
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Term
| Scinitllation detectors are more sensitive to ___ than ___ |
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Definition
| more sensitive to EMR than gas filled chambers. |
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Term
| What process involves the emission light protons after the deposition of energy in the crystal by ionizing radiation? |
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Definition
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Term
| What is the most commonly used collimator? |
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Definition
| the parallel hole collimator |
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Term
| What is the purpose of the photomultiplier tube? |
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Definition
| This part of the gamma camera converts light signal into electrical signal and amplify the electrical signal |
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Term
| What is the function of the coincident detection circuit? |
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Definition
| it is to determine whether gamma rays detected can be considered "simultaneous" hence constitue an event. |
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Term
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Definition
| they are electrogmagnetic waves whose frequencies are higher than light. |
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Term
| What is ionizing radiation? |
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Definition
| It is used in X-Rays and it is the radiation capable of ejecting electrons from atoms. |
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Term
| What is the defintion of an atomic number? |
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Definition
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Term
| What is the definiation of mass number? |
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Definition
| Number of protons plus the number of neutrons |
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Term
| What ionizaton radiation? |
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Definition
| is a high energy form of radiation which is named because it tears electrons from the atoms of the materials through which it passes, leaving behind newly formed ions. |
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Term
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Definition
| it is comprised of an electric wave and a magnetic wave moving at a right angle to eachother |
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Term
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Definition
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Term
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Definition
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Term
| What is the equation for the energy of photons? |
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Definition
E=hV where
h= planks constant (6.62*10-34)
V is the frequency of radiation |
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Term
| What is the equation for EM wavelength? |
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Definition
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Term
| How can a subatomic particle be considered to be ionizing radiation? |
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Definition
| if it possesses enough kinetic energy to ionize an atom |
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Term
| ON the color spectrum, wavelength increase ____, frequency increases ___ |
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Definition
Wavelength increases to the right
Frequency increases to the left |
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Term
| Does an alpha particle play a role in X-Ray/CT? |
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Definition
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Term
| Why is tungsten used as an anode in X-Ray? |
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Definition
| Tungsten is used because it not only has a high atomic number (74), but also lowest vapor pressure of all metals |
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Term
| What is the primary source of x-ray from the x-ray tube? |
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Definition
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Term
| During X-ray, energy is transferred to a bound electron, but not enough to ____ it. |
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Definition
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Term
| The electron will move to a more outer orbit, creating a void or hole that must be filled because the energy transferred to the bound electron wasn't enough to completely eject it. The filling of these holes comprise a secondary radiation called ___ |
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Definition
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Term
| What is the symbol for characteristic radiation and bremsstrahlung radiation? |
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Definition
Kα is characteristic and its the tallest of the radiations
Kβ is the brehmsstrahlung radiation and it is the shorter fatter radiations if shown on a graph |
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Term
| What is compton scattering? |
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Definition
| is one of the main mechanisms by which EMR interacts with materials it causes teh formation of an ion |
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Term
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Definition
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Term
| What effects the probability of coherent scattering? |
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Definition
| the material its traveling through and its incident x ray's energy |
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Term
| What does the photoelectric effect do? |
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Definition
| decreases the number of x rays reaching the detector |
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Term
| What are the 2 situations of the photoelectric effects? |
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Definition
chracteristic x ray transfers its energy from an outer orbit to the hole and produces characteristic radiation.
The characteristic x ray transfers its enery to an outer orbit electron called the anger electron |
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Term
| What is the intensity equation? |
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Definition
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Term
| What gas is used in the ionization chamber? |
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Definition
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Term
| Why is a high pressure gas needed in the ionization chamber? |
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Definition
| toincrease teh chance of x ray to zenon gas interactions |
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Term
| What is a function of the anti-scattering plate? |
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Definition
| The plates and ionization chamber act as an anti scatter plate since the x rays must enter from one single direction |
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Term
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Definition
| electron volt is aunit of kinetic energy NOT voltage. |
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Term
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Definition
| the energy gained by an electron when accelerated across one volt potential difference |
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Term
| What is filtered backprojection? |
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Definition
| is a special method based on projection slice theorem. IT is also an EXACT formula for the inverse RADON transform |
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Term
| What doe sthe projection slice theorem do? |
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Definition
Gives the relationship between 1-D fourier transform of a projection to the 2-D fourier transform of an object!
1-D fourier transform of a projection is a slice of the 2D fourier transform of the object |
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Term
|
Definition
| it is caused by energy selective attenuation of the X ray |
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Term
| What happens to a beams mean energy as it passes through an object? |
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Definition
| The beams mean energy tends to increase as it passes through an object due to the lower energy photons being absorbed |
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Term
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Definition
| It is an artifact that occurs when too few projections or slices are taken of an object |
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Term
| In practice, the reconstruction algorithm must consider the geometry of the scanner in terms of what? |
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Definition
| in terms of the type of the "beam" |
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Term
|
Definition
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Term
|
Definition
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Term
|
Definition
|
|
Term
| WHat frequency is ultrasound done with? |
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Definition
| 1-20MHz sometimes up to 70 MHz |
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Term
| Why is it important that ultrasound use such high frequencies? |
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Definition
| So the sound waves can travel farther without being absorbed. |
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Term
| What does the transducer in an ultrasound do? |
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Definition
| IT converts electrical signals to acoustic signals |
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Term
| What are transducers in an ultrasound made of? |
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Definition
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Term
| What produce echose back to the transducer in ultrasound? |
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Definition
| Organ boundaries and complex tissues |
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Term
|
Definition
| INtensity only, gives a signal (line) |
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Term
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Definition
| uses each signal from A mode as a column to construct 2D |
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Term
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Definition
| B mode is done by scanning the transducer beam in a plane. |
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Term
| HOw is 3D mode different from the other modes in ultrasound? |
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Definition
| 3D mode adds direction information. IT takes multiple snapshots of 2D ultrasounds but uses the 2D ultrasound images taken at various angles to construct an image. |
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Term
What is purpose of this equation?
p(z,t)=Φf(t-c-1z)+Φb(t+c-1z)
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Definition
| convert an acoustic pulse signal (as a function of time) to a spatial-temporal equation. YOu can do this by replacing the (t) in the equation with ((t-z)/c) in teh argument of the functions |
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Term
| What is a plane wave in ultrasound? |
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Definition
| A special case of acoustic wave traveling only one spatial dimension and time |
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Term
| How does an acoustic wave travel through the medium? |
|
Definition
| by compression and expansion of that material |
|
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Term
|
Definition
| happens between 2 different mediums and occurs when a wavefront changes its direction at an interface and comes back to the medium it started from |
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Term
|
Definition
| occurs whena wave changes its direction due to a change in speed and can be seen if the direction is at an angle other than 90 or 0 degrees |
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Term
| What is the equation for characteristic impedance? |
|
Definition
| is the Density times velocity |
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Term
| What is the eqn for acoustic pressure? |
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Definition
| p equals acoustic impedance (Z) times velocity |
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Term
| Attenuation accounts for loss in ___ |
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Definition
| loss in amplitude. It includes absorption, scattering and mode conversion |
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Term
| What does scattering refer to? |
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Definition
| Scattering refers to the generation of secondary spherical waves as wave propogates |
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Term
| What does absorption refer to in ultrasound? |
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Definition
| absorption converts the ultrasound wave into thermal energy |
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Term
| What is the doppler effect? |
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Definition
| is the relationship between the changes in he frequency of the wave due to the motion of the source |
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Term
| What does it mean if the doppler frequency is negative? |
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Definition
| the source is moving away from the receiver |
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Term
| What is the equation for doppler frequency? |
|
Definition
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|
Term
| What is case 1 in Doppler Frequency? |
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Definition
| Case 1 states that the source of the wave is moving while the reciever (or transducer) is stationary |
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Term
| What is case 2 in doppler frequency? |
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Definition
| Case 2 is when a source is stationary and the reciever is moving |
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Term
| When do you have both cases simultaneously in doppler effect? |
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Definition
in pulse echo mode meaning that the transducer acts as both teh source of the sound and teh reciever.
The source sends signals to the object, the object acts as a moving reciever and then acts as amoving source when it sends signals back to the transducer |
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Term
| What is geometric approximation in regards to ultrasound? |
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Definition
| near the transducer, we can treate the acoustic wave as if it were confined to a cylindrical shape propogating forward. |
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Term
| The farther the transducer is from the thing we are imaging, the ___ approximation is used? |
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Definition
| Further distance is the fresnel approximation |
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Term
at an even farther distance the transducer is from the thing we are imaging, the ___ approximation is used?
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Definition
| Fraunhofer approximation is used at even further distances |
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Term
| The slit size (a) is also what? |
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Definition
| The slit size is also the diameter of the transducer. |
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Term
| What does pulse echo mode refer to in ultrasound? |
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Definition
| The operation of using the same transducer for both generation and reception of ultrasound |
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Term
| we assume the velocity of sound in human soft tissue and calculate the time it takes for the signal to travel ____ |
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Definition
| to the tissue and back (ROUND TRIP) |
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Term
| NMR is concerned with what? |
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Definition
| nuclei of atoms, not with radioactivity like as in the other 3 imaging modalities |
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Term
| Only nuclei that have either ODD atomic number or ODD mass number can have ___ |
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Definition
|
|
Term
| explain right hand rule for MRI |
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Definition
| Align thumb to magnetic field. then spin follows the fingers |
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Term
| There is normally no macroscopic magnetic field in MRI because of what |
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Definition
| because the random oriented individual nuclear spins cancel eachother out in the macropscopic level |
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Term
| A simple rotation of the magnetization vector about the longitudinal (z) axis is what? |
|
Definition
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|
Term
| What does M and L stand for in MRI equations? |
|
Definition
M is the magnetic moment
L is the angular momentum |
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Term
| What is the gyromagnetic ratio? |
|
Definition
| defined as the ratio of magnetic dipole moment to the mechanical angular momentum of a system |
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|
Term
| In MRI, the static magnetic field is orientated how? |
|
Definition
|
|
Term
| In MRI, hwo is the RF field orientated? |
|
Definition
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|
Term
| ___ describes the forced and relaxation behavior of magnetic spin. |
|
Definition
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|
Term
| In absense of an applied RF magnetic field, the ___ ___ decays towards zero with T2 |
|
Definition
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|
Term
In absense of an applied RF magnetic field, the ___ ___ returns toward the equilibrium value Mo with T1
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Definition
| Longitudinal Magnetization |
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Term
| _ is typically between 250-2500ms. |
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Definition
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|
Term
| ___ is typically between 25-250ms. |
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Definition
|
|
Term
| __ is applied in z direction in MRI |
|
Definition
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|
Term
| ___ is applied in the x-y plane in MRI |
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Definition
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|
Term
| During relaxation, the nuclei lose energy and emity their own RF signal called FID. This results in what? |
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Definition
| FID results in a decrease in energy |
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Term
| _____ is generated by the transverse spins recovering their coherance after loss of coherance followed by the 180 degree RF pulse |
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Definition
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Term
| ___ are used to stimulate the hydrogen nuclei in a specific 2D image plane in the body and then determine the location of those nuclei within that plane as they precess back to their static state. |
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Definition
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Term
| ___ is done using the gradient coils in the Z direction. |
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Definition
| Phase selection and frequency encoding |
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Term
___ is done using the gradient coils in the X direction.
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Definition
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Term
___ is done using the gradient coils in the Y direction.
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Definition
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Term
___ is done using the gradient coils in the Z direction.
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Definition
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