question

electromagnetic radiation

answer

fluctuating fields of electric and magnetic energies

question

electric field

answer

x and y

question

magnetic field

answer

x and z

question

types of radiation

answer

heat, radio/sound, infrared, visable, ultraviolet, x-ray, gamma

question

frequency (nu)

answer

how frequently wave peaks

question

wavelength (lambda)

answer

length from peak to peak/wave to wave

question

low energy

answer

low frequency/long wavelength

question

high energy

answer

high frequency/short wavelength

question

wave "packets"

answer

photon

question

low E behaves

answer

like a wave

question

high E behaves

answer

like a particle

question

photon

answer

chargeless bundle of energy that is massless and travels at the speed of light; can be described as Einstein's theory of relativity

question

atom

answer

the smallest quantity of an element

question

molecule

answer

two or more atoms

question

nucleons

answer

protons and neutrons; held together by binding energy

question

valence electrons

answer

outtermost electrons responsible for almost all chemical interactions and radiation interactions

question

carbon

answer

used to define mass units (amu) at 12.000

question

protons

answer

defines an element's name and properties has 1 unit of positive charge

question

1.00759 amu

answer

proton mass

question

neutrons

answer

neutral nuclear particle with no electric charge slightly heavier than proton very unstable, breakdown to proton, electron, neutrine

question

1.00898 amu

answer

neutron mass

question

electrons

answer

smallest subatomic particle has 1 unit of negative charge held in orbit by binding energy p# and e# equal if electrically neutral called negatron when originating from nucleus

question

0.000549 amu

answer

electron mass

question

1-20

answer

1:1 ratio of proton to neutron

question

20+

answer

1:1.6 ratio of proton to neutron

question

nuclide

answer

proton/neutron combinations (over 1500 combinations)

question

radionuclides

answer

unstable proton/neutron combinations

question

decay modes

answer

unstable combinations of released energy and/or subatomic particles drive the nucleus closer to stability

question

mass defect

answer

relationship between mass and energy seen in strong nuclear forces

question

12.10266 amu

answer

carbon is made up of 6p, 6n, and 6e

question

95.6 MeV

answer

energy needed to overcome binding energy

question

X

answer

chemical symbol or element

question

A

answer

atomic mass number (p + n)

question

Z

answer

atomic number (number of protons)

question

isotoPe

answer

same number of Protons (z) different mass (a)

question

isoBar

answer

same weight/atomic mass (a) different number of protons (z)

question

isomEr

answer

different nuclear Energy same atomic mass (a) same atomic number (z) same elements nucleus is excited state (metastable)

question

isoTone

answer

different atomic mass (a) different atomic number (z) different elements same number of neutrons

question

fission

answer

separation of 2 nucleus energy liberating process (200 MeV on average) may be spontaneous or induced

question

fission products

answer

fragments of fission process usually radioactive generally have Z #'s between 30 (Zn) and 64 (Gd)

question

fusion

answer

two light nuclei come together to form a heavier nucleus new nucleus is lighter than the sum of the 2 nuclei due to energy being released (for elements below 26Iron)

question

transmutation

answer

changing from one element to another (n,p) is carrier free high specific activity

question

fission byproduct

answer

produced usually from 235U products are carrier-free separated by precipitation, chromotography solvent extraction decays by beta minus moderators, control rods, and reflectors serve to mediate this reaction

question

moderators

answer

slow neutrons down so they can interact

question

control rods

answer

absorb the neutrons

question

reflectors

answer

keep neutrons in core to maintain fission

question

neutron activation

answer

generally produces beta emitters so most useful only for radionuclide generators

question

linear accelerator

answer

accelerates subatomic particles (usually +charged) to KE high enough to overcome done by alternating voltages between 2 electrodes mostly used for research

question

cyclotron

answer

has linear tube wrapped up into coil with a target in the center makes commercial availability possible

question

a decay

answer

only for heavier elements, greater than 82 consists of 2 protons and 2 neutrons, helium atom w/out electron A# decreases by 4, Z# decreases by 2 biologically harmful, large size an ionizing charge short range of travel transmutation can be stopped by a sheet of paper

question

B- decay

answer

occurs in neutron-rich nuclei Z# increases by 1 can be biologically harmful slightly greater range than alpha particle isobaric transmutation can be stopped by a layer of clothing; few mm of metal

question

B+ decay

answer

occurs in proton-rich nuclei Z# decreases by 1 causes an annihilation reaction 1.022 MeV, 2 photons @ 511 KeV; 180 degrees apart isobaric transmutation

question

electron capture

answer

occurs in proton-rich nuclei most often a K-shell electron gets absorbed Z# decreases by 1 produces characteristic x-rays competes with positron decay isobaric transmutation

question

isomeric transition

answer

originates from within the nucleus transition between isomers releases gamma ray nucleus termed "metastable" very long range of travel no change A# or Z#, no transmutation lead is needed to shield gamma rays

question

internal conversion

answer

alternative to isomeric transition electron is ejected from its orbit characteristic x-ray produced by filling of vacancies no transmutation 140 KeV

question

no transmutation

answer

isomeric transition & internal conversion

question

transmutation

answer

the conversion of one element to another

question

isobaric transmutation

answer

B- decay, B+ decay, & electron capture

question

alpha decay schematics

answer

southwesterly direction; z-2

question

beta minus decay schematics

answer

southeasterly direction; z+1

question

beta plus decay schematics

answer

southwesterly direction; z-1

question

electron capture decay schematics

answer

southwesterly direction; z-1

question

gamma radiation schematics

answer

southerly direction with no change in z

question

standard chart

answer

isobars, diagonal lower right to upper left isotopes, left to right isotones, bottom to top

question

trilinear chart

answer

isobars, vertically adjacent isotones, diagonally adjacent upper left to lower right isotopes, diagonally adjacent lower left to upper right isomers, vertical line through hexagon

question

parent

answer

original nuclide in any mode of decay

question

daughter

answer

the nuclide to which a parent decays, which may be stable or unstable

question

particulate radiation

answer

alpha, beta, positron

question

non-particulate radiation/EMR

answer

x-rays, gamma rays

question

excitation

answer

(near miss) E passing charged particle or EMR causes metastable excitation of outer shell e-

question

ionization

answer

(direct hit) the particle or EMR with E greater than or equal to BE collides with e- and ejects it from its orbit, creating a positively charged atom and free e-; this is known as ion pair

question

ion pair

answer

the ejected electron and the resultant positively charged atom caused by the removal of electrons

question

ionizing radiation

answer

radiations that create ion pairs

question

alpha particles

answer

rapidly lose energy as they interact with matter cause the removal of electrons from an atom large, relatively slow moving particles that travel through matter in a straight line have the ability to create hundreds of thousands of ionizations in a very short distance due to high mass and +2 charge bowling ball

question

beta particles

answer

travel at a high speed than alpha particles their path may involve several deflections or changes in direction excitation, ionization, brems pool table ball

question

beta particles - excitation

answer

may interact with an orbital electron electron is raised to a temporarily higher energy state energy released in the form of visible or infrared light as it returns to its original state scintillators utilize this application

question

beta particles - ionization

answer

a beta particle collides with the orbital electron of an atom and causes it to be ejected leaves the atom without one electron and thus, a net + charge

question

beta (-/+) & Bremsstrahlung

answer

due to charge, a beta particle may be either attracted to or repulsed by the positively charged nucleus of an atom this attraction/repulsion can cause the beta particle to change direction beta particle must slow down as it changes direction beta particle must release energy in order to slow down this energy released is known as Bremsstrahlung

question

Bremsstrahlung

answer

braking radiation; energy released by beta particle as it slows down due to changing directions seen in radionuclides known as "pure beta emitters" Phosphorous32 is an example plastic/lucite shielding is required to lessen the Brems

question

likelihood of Bremsstrahlung

answer

increases in higher z# materials such as lead low z# such as plastic lessens Brems

question

x-rays & gamma rays

answer

non-particulate photons of varying wavelength, amplitude, and propagation/velocity

question

Electromagnetic radiation interactions with matter

answer

photoelectric effect, compton scatter, pair production, photonuclear disintegration

question

photoelectric effect

answer

low energy gammy ray inner orbital electron "photoelectron" completely absorbs the energy of the gamma ray photoelectron is ejected from orbit characteristic x-rays are given off as inner orbits are filled

question

compton scatter

answer

medium energy gamma ray outer shell electron "compton electron" absorbs a portion of the photon's energy remaining energy is released as a secondary gamma ray

question

pair production

answer

high energy photon greater than or equal to 1.02 MeV interacts near the nucleus two particles are created (beta particle, positron) positron goes on to be involved in annihilation reaction just as with positron decay

question

characteristic x-rays

answer

produced from electron cascades created when the electron in the next energy shell drops to fill the vacancy, transferring lesser BE requirements to the valance shell

question

Auger electrons

answer

produced when either a photoelectron or a characteristic x-ray cause a secondary ionization (usually within the same orbital shell)

question

factors that affect quality of images

answer

scatter & attenuation

question

scatter

answer

deflection of photon due to interaction with matter: patient, air, collimator, crystal

question

results of scatter

answer

change in direction of photon and decrease in energy of photon

question

attenuation

answer

blocking, shielding, or absorption of photons by matter

question

results of attenuation

answer

lower energy photons are more easily/likely attenuated appear as decreased area of uptake on images

question

half-life

answer

time required for half the amount of radioactivity to deplete

question

ways which half-life can be expressed

answer

number of radioactive nuclei (N) amount of activity present (A)

question

calibration time

answer

used to identify amount present at a predetermined time

question

purpose of Nuclear Physics

answer

create an image representing the distribution of a radiolabeled substance within the body

question

emissions recorded from radioactive substance

answer

administered internally recorded externally emissions must be strong enough to exit body

question

80 - 500 KeV

answer

emissions best suited for imaging; sufficient energy to exit body

question

thallium activated sodium iodide crystal

answer

can be stopped by scintillation material

question

lead & tungsten

answer

can be adequately shielded and collimated

question

adds counts we don't want (changes direction & energy)

answer

scatter

question

subtracts counts we want

answer

attenuation

question

number of events

answer

disintegrations; decays because of radioactivity; too few counts degrade image

question

factors that can degrade image

answer

scatter, attenuation, collimator performance, number of events, equipment QC

question

contrast

answer

the ability to differentiate between target & background and different tissue layers

question

thicker/denser crystal

answer

stops more photons increases crystal sensitivity decreases spatial resolution

question

sensitivity

answer

stopping of photons

question

spatial resolution

answer

measure of how close two distinct sources of activity can get and still be distinguished as separate

question

gamma camera collimator

answer

limits and directs radiation emissions from patient

question

parallel hole

answer

direct representation

question

converging

answer

holes are focused toward a single point focal point located in center of field of view causes organ/image to appear magnified

question

pinhole

answer

specific converging collimator for greatest magnification used in ped/neonatal used for thyroid imaging

question

diverging

answer

holes focused away from large plane toward central point allows for larger object to fit within image constraints

question

fan beam

answer

holes converge along one single line of symmetry useful in cardiac/brain SPECT images

question

proportional to resolution

answer

hole length and diameter smaller, longer holes increases resolution

question

septal thickness

answer

thicker will block higher energy photons will prevent image burnout

question

resolution decreases

answer

distance is increased between patient and camera

question

uniformity

answer

ability of camera to show uniform source as uniform image

question

"flood"

answer

uniformity

question

extrinsic flood

answer

done with collimator on uses a sheet source; normally 57Co done as a daily quality control

question

intrinsic flood

answer

done with collimator off uses a point source; normally 99mTC usually performed as weekly quality control

question

resolution

answer

ability to accurately distinguish between two point sources uses a bar phantom and 57Co sheet source done as a weekly quality control normally done in conjunction with linearity with a bar phantom

question

linearity

answer

ability to display straight lines of activity as straight lines on an image uses the bar phantom done as a weekly quality control

question

center of rotation

answer

corrects misalignment of SPECT images taken from multiple projections done as a weekly quality control

question

planar images

answer

high resolution problem of super imposing structures

question

multiple projection w/ SPECT

answer

sacrifice resolution gain better contrast

question

multiple projections

answer

1, 2, 3 head camera 180 degree and 360 degree orbits 180 degree is beneficial in cardiac imaging

question

noise

answer

random radiation events that provide useless information

question

> 1.022 MeV

answer

positron decay is possible proton rich nuclei decay by either EC or B+

question

cyclotron produced

answer

PET radiopharmaceuticals

question

PET radiopharmaceuticals

answer

produced by bombarding with positively charged particles (protons or deuterons)

question

temporal resolution

answer

light converted quickly

question

scintillation material

answer

requires higher density material

question

PET camera

answer

511 KeV

question

bismuth germanate

answer

good stopping power based on high molecular weight poor/slow scintillator yields only a small amount of light poor energy resolution

question

LSO, LYSO, GSO

answer

sacrifice stopping power for greater scintillation properties (more light per KeV and faster scintillation)

question

PET detector arrangement

answer

8,000-20,000 small crystals 3-4mm and 10-30mm in length too small for individual PM tubes

question

16 crystals/PMT; 4 PMT/block

answer

PET detector arrangement

question

true coincidence

answer

desirable 511 KeV photons detected 180 degrees apart

question

scattered coincidence

answer

will misrepresent actual location of event forms a triangle of detected events

question

random coincidence

answer

two separate events scatters are both registered 180 degrees apart from each other creating an artificial event random events increase with greater activity

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