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FINAL for dr. chiu
PET, Ultrasound, MRI, XRAY/CT and pulse oximetry
123
Engineering
Undergraduate 3
02/14/2011

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Cards

Term

What is transmutation?

Definition
Isotopes will release energy and matter form their nucleus and often transform into a new element.
Term
What is the equation for Half-Life?
Definition

At=A0e-λt

where decay constant is found by 

λ=loge(2)/t1/2

Term
What are the main particulate radiation resulting from radioactive decay?
Definition
Alpha, Beta and Gamma
Term
The electromagnetic ionizing radiations resulting from radioactive decay are called what?
Definition
Gamma rays
Term
What results from ISOMERIC Transition?
Definition
emission of gamma rays
Term
What is a positron?
Definition
A positively charged electron and its also an anti matter
Term
When converting Carbon-11 to Boron-11 what is essentially happening?
Definition

Carbon-11==>

Boron-11+positron+neutron

Term
PET scans use Carbon, nitrogen, oxygen and F because?
Definition
THey all go through beta decay and emit positrons and because they are abundant through the body (biochemistry)
Term
What is a meta-stable state?
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

Term
Isomeric Transition is what?
Definition

releasing the energy in the form of a gamma ray photon 

Here the energy level depends on the element involved.

Term
When a positron collides with an electron, the 2 particles _____ eachother and produces 2 photons traveling in _____ direction
Definition

annihilate

opposite directions

Term
The most common tracer compound is ___
Definition

18

fluerodeoxyglucose

used for glucose metabolism

glucose consumption and to detect different glucose metabolic rates

Term
Positron decay or postron emission  happens when a single positron reacts with an electron through annihilation produces ___
Definition

2 gamma rays ( 2 photons) each at 511 keV AS ALWAYS 

we get 511 keV from E=mc2

Term
PET uses a gamma emitter.  What is this?
Definition
Gamma emitter is the transofmration associated with the emission of a photon of a precise energy
Term
SPECT uses a beta plus emitter, what is this?
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
Term
What is the photon detector inside PET?
Definition
2 photons are detected simultaneously so it is know that the annihilation point is on teh line joining the 2 detected points
Term
What is the photon detector in a SPECT?
Definition
a single photon does not bear information about its direction when it hits the crystal
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 ___.

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

 

Term
What is a scintillation crystal?
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.
Term
What kind of crystals did the original scintillation camera use?
Definition
The initial anger scintillation camera used scintillation crystals made of sodium-iodide (NaI)
Term
Scinitllation detectors are more sensitive to ___ than ___
Definition
more sensitive to EMR than gas filled chambers.
Term
What process involves the emission  light protons after the deposition of energy in the crystal by ionizing radiation?
Definition
scintillation
Term
What is the most commonly used collimator?
Definition
the parallel hole collimator
Term
What is the purpose of the photomultiplier tube?
Definition
This part of the gamma camera converts light signal into electrical signal and amplify the electrical signal
Term
What is the function of the coincident detection circuit?
Definition
it is to determine whether gamma rays detected can be considered "simultaneous" hence constitue an event.
Term
What are X-rays?
Definition
they are electrogmagnetic waves whose frequencies are higher than light.
Term
What is ionizing radiation?
Definition
It is used in X-Rays and it is the radiation capable of ejecting electrons from atoms.
Term
What is the defintion of an atomic number?
Definition
# of protons
Term
What is the definiation of mass number?
Definition
Number of protons plus the number of neutrons
Term
What ionizaton radiation?
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.
Term
What is an EMR made of?
Definition
it is comprised of an electric wave and a magnetic wave moving at a right angle to eachother
Term
EMR has no __ and no __
Definition
no mass and no charge
Term
What are photons?
Definition
packets of energy
Term
What is the equation for the energy of photons?
Definition

E=hV where

h= planks constant (6.62*10-34)

V is the frequency of radiation

Term
What is the equation for EM wavelength?
Definition
λ=c/v
Term
How can a subatomic particle be considered to be ionizing radiation?
Definition
if it possesses enough kinetic energy to ionize an atom
Term
ON the color spectrum, wavelength increase ____, frequency increases ___
Definition

Wavelength increases to the right

Frequency increases to the left

Term
Does an alpha particle play a role in X-Ray/CT?
Definition
no
Term
Why is tungsten used as an anode in X-Ray?
Definition
Tungsten is used because it not only has a high atomic number (74), but also lowest vapor pressure of all metals
Term
What is the primary source of x-ray from the x-ray tube?
Definition
Bremsstrahlung radiation
Term
During X-ray, energy is transferred to a bound electron, but not enough to ____ it.
Definition
eject
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 ___
Definition
characteristic radiation
Term
What is the symbol for characteristic radiation and bremsstrahlung radiation?
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

Term
What is compton scattering?
Definition
is one of the main mechanisms by which EMR interacts with materials it causes teh formation of an ion
Term
[image]
Definition
KNOW
Term
What effects the probability of coherent scattering?
Definition
the material its traveling through and its incident x ray's energy
Term
What does the photoelectric effect do?
Definition
decreases the number of x rays reaching the detector
Term
What are the 2 situations of the photoelectric effects?
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

Term
What is the intensity equation?
Definition
Ix=I0e-μx
Term
What gas is used in the ionization chamber?
Definition
xenon
Term
Why is a high pressure gas needed in the ionization chamber?
Definition
toincrease teh chance of x ray to zenon gas interactions
Term
What is a function of the anti-scattering plate?
Definition
The plates and ionization chamber act as an anti scatter plate since the x rays must enter from one single direction
Term
eV is a unit of what?
Definition
electron volt is aunit of kinetic energy NOT voltage.
Term
What is an eV?
Definition
the energy gained by an electron when accelerated across one volt potential difference 
Term
What is filtered backprojection?
Definition
is a special method based on projection slice theorem.  IT is also an EXACT formula for the inverse RADON transform
Term
What doe sthe projection slice theorem do?
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

Term
What is beam hardening?
Definition
it is caused by energy selective attenuation of the X ray
Term
What happens to a beams mean energy as it passes through an object?
Definition
The beams mean energy tends to increase as it passes through an object due to the lower energy photons being absorbed
Term
What is undersampling?
Definition
It is an artifact that occurs when too few projections or slices are taken of an object
Term
In practice, the reconstruction algorithm must consider the geometry of the scanner in terms of what?
Definition
in terms of the type of the "beam"
Term
What is a parallel beam?
Definition
Term
What is a helical beam?
Definition
Term
What is a cone beam?
Definition
Term
WHat frequency is ultrasound done with?
Definition
1-20MHz sometimes up to 70 MHz
Term
Why is it important that ultrasound use such high frequencies?
Definition
So the sound waves can travel farther without being absorbed.
Term
What does the transducer in an ultrasound do?
Definition
IT converts electrical signals to acoustic signals
Term
What are transducers in an ultrasound made of?
Definition
a piezoelectric signal
Term
What produce echose back to the transducer in ultrasound?
Definition
Organ boundaries and complex tissues
Term
What does A-mode do?
Definition
INtensity only, gives a signal (line)
Term
What does M- Mode do?
Definition
uses each signal from A mode as a column to construct 2D
Term
What does B-mode do?
Definition
B mode is done by scanning the transducer beam in a plane.
Term
HOw is 3D mode different from the other modes in ultrasound?
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.
Term

What is purpose of this equation?

p(z,t)=Φf(t-c-1z)+Φb(t+c-1z)

 

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
Term
What is a plane wave in ultrasound?
Definition
A special case of acoustic wave traveling only one spatial dimension and time
Term
How does an acoustic wave travel through the medium?
Definition
by compression and expansion of that material
Term
Explain reflection
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
Term
Explain refraction
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
Term
What is the equation for characteristic impedance?
Definition
is the Density times velocity
Term
What is the eqn for acoustic pressure?
Definition
p equals acoustic impedance (Z) times velocity
Term
Attenuation accounts for loss in ___
Definition
loss in amplitude. It includes absorption, scattering and mode conversion
Term
What does scattering refer to?
Definition
Scattering refers to the generation of secondary spherical waves as wave propogates
Term
What does absorption refer to in ultrasound?
Definition
absorption converts the ultrasound wave into thermal energy
Term
What is the doppler effect?
Definition
is the relationship between the changes in he frequency of the wave due to the motion of the source
Term
What does it mean if the doppler frequency is negative?
Definition
the source is moving away from the receiver
Term
What is the equation for doppler frequency?
Definition
fD=vcos(Θ)*fO/c
Term
What is case 1 in Doppler Frequency?
Definition
Case 1 states that the source of the wave is moving while the reciever (or transducer) is stationary
Term
What is case 2 in doppler frequency?
Definition
Case 2 is when a source is stationary and the reciever is moving
Term
When do you have both cases simultaneously in doppler effect?
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

Term
What is geometric approximation in regards to ultrasound?
Definition
near the transducer, we can treate the acoustic wave as if it were confined to a cylindrical shape propogating forward.
Term
The farther the transducer is from the thing we are imaging, the ___ approximation is used?
Definition
Further distance is the fresnel approximation
Term

at an even farther distance the transducer is from the thing we are imaging, the ___ approximation is used?

Definition
Fraunhofer approximation is used at even further distances
Term
The slit size (a) is also what?
Definition
The slit size is also the diameter of the transducer.
Term
What does pulse echo mode refer to in ultrasound?
Definition
The operation of using the same transducer for both generation and reception of ultrasound
Term
we assume the velocity of sound in human soft tissue and calculate the time it takes for the signal to travel ____
Definition
to the tissue and back (ROUND TRIP)
Term
NMR is concerned with what?
Definition
nuclei of atoms, not with radioactivity like as in the other 3 imaging modalities
Term
Only nuclei that have either ODD atomic number or ODD mass number can have ___
Definition
Angular momentum
Term
explain right hand rule for MRI
Definition
Align thumb to magnetic field. then spin follows the fingers
Term
There is normally no macroscopic magnetic field in MRI because of what
Definition
because the random oriented individual nuclear spins cancel eachother out in the macropscopic level
Term
A simple rotation of the magnetization vector about the longitudinal (z) axis is what?
Definition
Precession
Term
What does M and L stand for in MRI equations?
Definition

M is the magnetic moment

L is the angular momentum

Term
What is the gyromagnetic ratio?
Definition
defined as the ratio of magnetic dipole moment to the mechanical angular momentum of a system
Term
In MRI, the static magnetic field is orientated how?
Definition
along the Z axis
Term
In MRI, hwo is the RF field orientated?
Definition
in x-y plane
Term
___ describes the forced and relaxation behavior of magnetic spin.
Definition
Bloch Equation
Term
In absense of an applied RF magnetic field, the ___ ___ decays towards zero with T2
Definition
Transverse magnetization
Term

In absense of an applied RF magnetic field, the ___ ___ returns toward the equilibrium value Mo with T1

Definition
Longitudinal Magnetization
Term
_ is typically between 250-2500ms.
Definition
T1
Term
___ is typically between 25-250ms.
Definition
T2
Term
__ is applied in z direction in MRI
Definition
T1
Term
___  is applied in the x-y plane in MRI
Definition
T2
Term
 During relaxation, the nuclei lose energy and emity their own RF signal called FID. This results in what?
Definition
FID results in a decrease in energy
Term
_____ is generated by the transverse spins recovering their coherance after loss of coherance followed by the 180 degree RF pulse
Definition
Spin echo
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.
Definition
Gradient coils
Term
___ is done using the gradient coils in the Z direction.
Definition
Phase selection and frequency encoding
Term

 

___ is done using the gradient coils in the X direction.

 

Definition
Slice selection
Term

 

___ is done using the gradient coils in the Y direction.

 

Definition
Phase encoding
Term

___ is done using the gradient coils in the Z direction.

Definition
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