Dental Radiography - History & Physics (1) Flashcards
Who was the father of xrays
willhelm Roentgen
when were X-rays first discovered
in 1895
The X in xrays was used to name them due to
their unknown nature
Dr Otto walkhoff took the
first dental X-ray (on himself) in 1896
dr otto walkhoff subjected himself to how many minutes of radiation on one xray
25 minutes
Dr c Edmund kells was the first to
take a dental xray on a patient in 1896
The first hot cathode xray tube was developed by
William d Coolidge
Ionizing radiation can
remove elections from atoms
nonionizing radiation is able to ___ but docent have enough energy to
can heat things but not enough energy to remove electrons
Radiation is
energy carried by waves of a stream of particles through space or matter
X-radiation is
high energy radiation from the collision of electrons on a metal target in xray tubes
Xradiation is AKA
ionizing electromagnetic radiation
An Xray is known as a
beam of energy with power to penetrate through objects and record the shadows on a image receptor
what is radiology
the study of radiation in medicine
A radiograph is a
image produced on a receipt by exposing it to ionizing radiation
radiography is the art and science of
making radiographs through exposure
ALARA
as low as reasonably achievable
alara is in place to
protect everyone and reduce exposure as much as possible without compromising the need for diagnostic records
a radiation protection officer can only be the dentist and is responsible for
safe practice, ensures safety of equipment, and proper operation of it
Matter is known as
anything occupying space and has a shape or form
atoms are
basic form of matter containing energy
sub atomic particles make up
an atom (electrons, protons, neutrons)
molecules are
atom groupings - smallest particle of a substance that retains original state
Capacity to do work is
energy
energy can’t be destroyed or created but it can
change form
the central nucleus is composed of
protons and neutrons
electrons are negativley charged and ___ the nucleus
orbiting
Nuclear binding energy is responsible for
holding the nucleus together
electron shells are located where
a specific distance from the nucleus and each shell represents a different energy level
Shell L is the ___ and has the __ energy level
closest, energy
what is designated by letters l,m,n,o,p,q
electron shells
Mass number is
protons + neutrons
equal protons and neutrons are the
atomic number
Attraction between protons and electrons is the
electrostatic force
centrifugal force is what
pulls electrons away from nucleus
the balance of electrostatic force and centrifugal force keeping electrons in orbit is known as
biding energy
Radioactivity is the process of
unstable atoms undergoing spontaneous disintegration in order to become balanced
what is an ion
an atom that has gained or lost an electron
are ions electrically balanced
no
Ionization is the
production of ions / process if converting atoms to
if an atom gains a extra election it is now considered
more negative
what are the two types/categorys of ionizing radiation
particulate and electromagnetic
particulate ionizing radiation is
tiny particles (with mass) travelling in a straight line at high speeds
there are two sub types of particulate radiation called
beta particles and cathode rays
beta particles are
electrons from nucleus of radioactive atoms
a cathode ray is composed of
high speed electrons travelling from an xray tube
ionizing electromagnetic radiation is a
wavelike energy with no mass, travelling through space or matter
can electromagnetic radiation be ionizing or nonionzing
yes
photons make up
ionizing electromagnetic radiation
photons travel at the speed of light in a
straight line with a wavelike motion
do photons have mass
no
wave concept has 3 parts, what are they
velocity, wavelength, frequency
velocity is the
speed of the wave
wavelength is the
distance between the crests of two waves
what does wavelength determine
the energy and penetrating power of a ray
the shorter the wavelength, ____ penetrating power and energy
higher
frequency is the
number of waves that pass a certain point in a given time
a short wavelength results in a __ frequency
high
mA
milliamperage
mA is in control of
the quantity of electrons that are produced
mA is the electrical current coming from the
cathode - regulates temp of filament for production of electrons
What 3 factors impact density and contrast
mA, kVp, exposure time
What is the recommended setting of mA
7-15 mA, 10 is most common
increasing the mA will make the density ___
darker - less contrast
kV or kVp
kilovoltage
kVp controls the
quality of an xray beam (wave length size)
voltage rate for kVp
70-90 kVp
kV controls how ___ electrons move from the cathode to anode
fast
the faster an electron moves to anode the ___ the wavelength
shorter
a quality wave length is a
short wavelength
the speed of electrons is controlled by adjusting the
kVp
the amount of electrons is controlled by adjusting the
mA
if more electrons are produced the more wavelengths are produced leading to a ___ image
darker
if an image comes out to dense (dark) you would adjust the ___ to make it lighter and have more contast
mA
if adjustments to kVp and mA don’t fix the image you would check what next
the machine it self, could’ve been bumped and knocked out of place or broken
MPD
maximum permissible dose
what’s the MPD for a worker
0.05 sv
for a pregnant worker the MPD is
2 msv
low contrast images would show lots of
grey shades
high contrast images would be primarily __
black and white shades
why would you increase the mA when taking xrays on a heavier person
the density of the individual effects the penetrating power of a beam - needs more to get through
the step down transformer sends low voltage electricity into the
cathode only
bremsstrahlung radiation is
breaking radiation - sudden stop of electrons when they hit the target
Exposure is measured in impulses/second - how Many impulses in 1 second
60 impulses per second
exposure time is the
interval of time in which xrays are produced
longer exposure time results in more waves created making the image
darker
if you increase the exposure time, you would need to do what to the kVp and mA
decrease both to compensate, and vice versa if shorter time
what factors effect the exposure time
length of PID, type of receptor, age of patient, type of tissue
if the PID is longer, you would have to increase what to compensate for the distance
exposure settings would need to increase
intensity is a combination of
quality and quantity
an ampere is
measurement of electrons flowing through cathode
TRD
target to receptor distance (longest)
TOD
target to object (tooth) distance
TSD
target to surface distance (skin)
Primary radiation is
the beam produced by target that exits tubehead
secondary radiation is
created when it interacts with soft tissue
scatter radiation
result of beam deflecting from path due to interaction with matter
background radiation
from normal objects (phones)
leakage radiation
produced by machines due to fault
how long is a quality assurance log book kept
6 years
a tubehead is equipped with what 3 things for patient protection
aluminum disks, lead collimater, PID
how much aluminum filtration is needed for a 70 kvp machine
1.5 mm
if machine is operating above 70 kvp how much filtration is needed
2.5mm
lead collimators are responsible for
restricting the size of the beam exiting
lead collar is only used for which type of xray
inta oral only
what is the fastest intra oral film
F speed film (insight)
what is used to prevent hand exposure to radiation
a film holding device
how far must you stand while xray in progress
3m or 9ft
asepsis protocol in radiology
all equipment must be disinfected after each patient, and barriers used when possible
film holders are sterilized after each use
universal standard precuations
cumulative effect
radiation can cause damage that is irreversible and tissues don’t return
latent period is
the time between exposure and symptoms
total dose
amount of radiation absorbed
direct theory is damage occurring from radiation that
directly hits critical areas of cell
indirect theory is xray energy that
absorbs within a cell and causes toxin formation
what is the most sensitive cells
blood forming tissues (bone marrow)
erythema
radiation dermatitis, red rash
short term effects are
acute
long term effects are chronic and
are associated with small amounts of radiation in long periods of time
genetic effects damage
reproductive cells (ova and sperm)
somatic effects are damage to tissues not inherited and repair within
24 hours
the risk of damage to bone marrow cells is
development of leukaemia
extra oral xrays are
panoramic
intraoral xrays are
with tubehead
electrodes are
cathode and anode
why is the xray tube vacuum sealed
to allow electrons to flow with minimal resistance between electrodes
the cathode has 2 main components
the tungsten filament and molybdenum cup
the molybdenum cup is for
forcing electrons into a narrow beam towards anode
tungsten filament produces
electrons with heat
the anode has 2 components
the tungsten target and copper stem
the tungsten target is incasing a copper stem to
dissipate heat of the target
99% of electrons produced by cathode are converted into
heat
only 1% of electrons will
hit the target and become waves
central ray
xrays at the center of beam through collimater
melting point of tungsten is
3422 c
what shape is never used for PID’s
square
SI
systeme internationale
what kind of rays are the most dangerous
gamma rays
what is the radiation pattern at the skin that should now be exceeded
2.75” or 7cm
Penumbra
a blurred or indistinct area surrounding an image
primary radiation is the most …
penetrating form of radiation
scatter radiation is a form of
secondary radiation - created by beam interacting with matter
a sensor is a __ with a chip and electrical current
solid state image receptor
what is the focal spot of the anode
the tungsten target
the step down transformer is responsible for
decreasing the voltage that is coming into the tube head from the extension arm. from 220>110>5>3 volts
how many volts are used to heat tungsten filament
3-5
thermionic emission is the
release of electrons from tungsten filament
radiolucent structures appear
dark on a radiograph
why do radiolucent structures appear dark
because radiation can easily pass through them
radioplaque structures appear how on a radiograph
white or light grey
why do radioplaque structures appear white or light grey
because radiation does now easily pass through them
the energy of a photon is knows as ___
quality
