Intro To Rad Unit 2 Flashcards
-Physics -Radiographic Equipment -Prime Factors -Image Quality Factors -Image Accessories -Geometric Factors -Math
Physics-
The branch of science that deals with matter and energy and their relationship to each other.
Atom
smallest particle of an element that still has its properties
Atomic Number
of protons in an atom
-positive charged
-determine what and where atom is on periodic table
Atomic Mass-
Particles in nucleus of atoms
protons+neutrons
Electrons-
Exist around nucleus in shells; determine how atom combines with other atoms
Ionization-
The charging of atoms
(can be negative-gained electrons or
positive-lost electrons)
Radiation
Energy transmitted by waves through space;causes ionization
X-rays-
man-made ionizing radiation
Gamma ray
Naturally occurring ionizing radiation given off from atoms like radioactive isotopes as they decay.
Electromagnetic Spectrum order:
-x-rays
-gamma rays
-Ultra Violet
-visible light
-infra red
-radio waves
Three ways to write the speed of light:
-186,000 miles/sec
-3X10^10 cm/sec
-3X10^8 m/sec
The shorter the wavelength-
The more penetrating
Sine waves
waves of energy
Wave length distance is_
from peak to peak
Amplitude-
The height of peak
Cycle-
distance from peak, valley, peak, and valley
Frequency-
the smaller the sound wave-
number of cycles per second
-the more penetrating
Properties of x-rays-(12)
-highly penetrating
-invisible
-short wavelength
-electrically neutral
-polyenergetic/heterogenous
-liberate small amounts of heat when passing through matter
-travel in straight lines
-cause ionization
-cause fluorescence
-affect photorgraphic film
-produce secondary and scattered radiation
-produce chemical and biological changes
Scattered radiation-
hits patient and changes direction
Condition for Production:(diagnostic)
- source of electrons
2.speeding electrons up
3.suddenly stopping electrons - need a glass tube
Condition for Production (not diagnostic):
- source of electrons
2.speeding electrons up
3.suddenly stopping electrons
The source of electrons in a radiographic tube come from-
amerage(current) heats filament that causes in thermionic emission
Thermionic emission-
the liberation of electrons by virtue of its own temperature
How fast do electrons speed up in a radiographic tube?
half the speed of light
The electrons are stopped in a radiographic tube by__ and results in_
-interaction with target
-99% heat and 1% electromagnetic radiation
Cathode-
the negative charged side of x-ray tube
-contains 2 wires; tungsten filament
Filament
-cathode or anode?
2 wires made of tungsten that are the source of electrons
-cathode
Focusing cup
-cathode or anode?
made of?
negatively charged that repels electrons and concentrates the electron beam on the focal spot of the anode
-cathode
-made of molybdenum
Anode-
made of? (2)
The positive charged side of tube that has a surface called a target and a focal spot
-made of tungsten and rhenium
Tungsten is used in radiographic tube because-
it has a high atomic number which gives it a high melting point
Glass envelope-
made of pyrex to withstand the extra high heat not directed to focal spot
Housing-
made of-
insulation, cooling, and protection
-made of metal and lead; insulating oil
Primary radiation-
radiation leaving the tube window open
Leakage-
Anything leaving other parts of the tube
(housing should prevent leakage)
Attenuated-
Absorption and scatter; does not reach the image receptor (cassette)
Remnant-
passes completely through patient and exposes image receptor; direct transmission
mA-
current-amperage
milliamperage-heats up the filament
intensity and quantity of electrons
-the higher the mA the hotter the filament
Time(seconds)-
controls how long the electrons come out
-expressed as a fraction or decimal
-shorter exposure time for less motion
kVp-
causes-
-kilovoltage peak
-the quality/ strength of x-ray beam; wavelength
-1 kV = 1,000 volts of electricity
-causes contrast of image( gray scale)
-increase in kVp is shorter wavelength
Distance(SID)-
;distance from tube to image; source to image distance
- as distance gets further away, spatial resolution increases, magnification decreases, and image receptor exposure decreases.
the higher the mA-
the hotter the filament and more xray electrons will be created( intensity and quantity)
-greater image receptor exposure
Formula for image receptor exposure-
mA X Time = mAs
Inverse square law-
formula?-
Thumb rule-
- when the distance changes and you want to know what the new intensity will be ; finding intensity( R mR)
-old intensity/new intensity=new distance^2/old didstance^2
½ SID = 4 X mR*
2X SID = ¼ mR
Why do you need more radiation for father away images?
due to the beam diverging and covering a larger area
Exposure Maintenance Law-
Formula-
used to find the new mAs technique when the SID changes and want to maintain IR exposure
-mAs1/mAs2 = D1^2/D1^2
IR exposure definition-
double the mA=__
Double the time=__
the amount of radiation a patient receives.
-double the IR exposure
-double the IR exposure(increases chance of motion)
most dense to least dense on x-ray image-(5)
-metal
-bone
-muscle
-soft tissue
-air
Subject Contrast-
digital or analog?
result of differential absorption of dif. tissues in the body due to atomic number differences and tissue thickness differences of the patient.
‘digital
Contrast resolution-
the ability to distinguish anatomical structures of similar subject contrast
Gray scale-
how many colors we have represented
-low kVP=short gray scale(black and white), high subject contrast
-high kVp= long gray scale, low subject contrast
For the 15% rule when you have too much exposure you-
Multiply kvp by .15 and then subtract product to the original kVp
For the 15% rule when you have too little exposure you-
Multiply kVp by .15 and then add product to original kVp
Half Value Layer-
The thickness of absorbing material needed to reduce the intensity of x ray beam to 1/2 it’s original value before it hits patient
2N^2
N=number of shells
k=2
L=8
M=18
Heterogenous-
many wavelengths
Half value layer-
reduces beam intensity before hitting patient
Grid-
-protects patient?
placed between patient and image receptor to absorb scattered or secondary radiation
-to get better image NOT to protect patient
Radioopaque-
Radiolucent-
- absorbs x-rays(shows up white on x-rays) bone
-x-ray passes through( shows up black on x-ray)
Beam restrictors-
protects patient?
-collimator;beam limiting device
reduce scatter and secondary radiation-patient exposure decreases, subject contrast increases,
Filtration-
built in tube feature that removes lower energy(long wavelengths) radiation before it reaches the patient.
-lowers patient entrance exposure (ESE)
table-
radiolucent and tilts 15/90
Image receptor-
CR-
DR-
to record the image to have a permanent record
- uses special cassette
-uses digital sensor
casette ID contains-
name, date, patient ID number, and facility name
spatial resolution-
can control by
voluntary-
involuntary-
sharpness of detail in representing the true edges of anatomy on image; how crisp edges of different bones are
-communicate to get them to not move
-try to use short exposure time
The smaller the focal spot-
-the limiting factor is-
the better the spatial resolution
-heat produced by high techniques required for thick anatomy
Umbra-
Penumbra-
‘pure shadow
-blur
Small focal spot-
large focal spot-
small anatomy
-large anatomy
Increased SiD=
increased spatial resolution and decreased IR exposure
OID-
distance between part being radiographed and image receptor
decreased OID= increased spatial resolution
Ideal spatial resolution-
-small focal spot size
long SID
short OID
limited motion
small pixel size
Magnification-
size distortion; different between real size of object affected by SiD and OID
Foreshortening-
elongation-
- made smaller
- made longer in pic
