RAD Boards Flashcards
projection
It is where the CR enters and exists the patient towards the IR
ex: AP is anterior posterior the CR enters the pt anteriorly and exists posteriorly before it interacts with the IR
Position
How the pt body is placed or the placement of the body part in relation to the IR
Axial
angulation of the x-ray tube
ex: cephalic (head) or caudal (feet)
if you see the feet angle to the feet
Pt is laying on their back
supine
what is the term for laying down?
recumbent
Pt is laying on their stomach
prone
What is the Sims position?
Pt is in left lateral, right leg is moved in front of patient
Trendelenburg
Head is lower then the head
“Toes are higher”
Fowlers
Feet are lower than the head
In a decubitus position the patient is supine what is this referred to?
dorsal
In a decubitus position the patient is prone what is this referred to?
ventral
Pt is in a left lateral decubitus what marker do you put?
Right- always mark the side up
Pt is in a left dorsal decubitus what marker do you put?
Left-mark the side closest to the IR
Plane that divides the body into left and right halves (equal)
Mid sagittal
coronal plane
divides the body into anterior and posterior parts
What does the prefix “mid” refer to when speaking about body planes
means split into equal halves
plane that divides the body into superior and inferior parts
transverse or horizontal
movement away from the center of the body
abduction
movement toward the midline
adduction
Pt is asked to rotate their arm towards the midline of the body what kind of movement is this?
medial rotation
RT positions pt’s arm so that it is moving away from midline
abduction
In a PA chest why do you have the PT roll their shoulders forward
puts the scapulas in a more lateral position which allows better visualization of the lungs
how many ribs must be seen on a PA chest
10 posterior ribs
why is the lateral chest performed on the left
heart dips down to the left and it reduces magnification
where is the CR entrance point for a lateral chest
midcoronal plane at the level of T7
what is the purpose of the lordotic view
shows apices of the lungs
is there a tube angle for lordotic?
No
PT takes a few steps forward while having their back against the board
72 inches
what makes a good lordotic image
clavicles are projected above the apices
clavicles appear to be straight
CR of a lordotic chest
3-4 inches below the jugular notch
PT is leaning backward 15-20 degrees
how many posterior ribs are needed to be seen on an AP portable chest
8-9 posterior ribs
for a sthenic pt the top of the IR for a portable AP chest should be placed
1.5 inches (4cm) superior to the soft tissue of the shoulder
how do you know if there is rotation in an AP portable chest
asymmetrical ribs and clavicles
what is the SID for lateral view of a soft tissue neck?
72 SID
ensure that the top of the light field is above the EAM
what is a diagnostic lateral soft tissue neck?
air filled trachea from the pharynx to the midthoracic region
what is the CR for AP soft tissue neck?
1 inch superior to jugular notch
what is the carina associated with?
bifurcation of the trachea
how should the Vascular markings of the lungs appear on a PA chest
should appear thin in the superior portion of the lungs
what health condition demonstrates absence of the diaphragm contour and blunting of the CP angles
pleural effusion
which abnormalities are found in a pt with CHF?
enlarged cardiac size
pulmonary edema
types of radiation measurements
radiation in the primary beam
leakage radiation
amount of radiation absorbed by the pt
amount of radiation absorbed by the healthcare provider
what is leakage radiation measure?
the amount of secondary radiation escaping the x-ray tube
what are the common radiation measurements?
exposure
air KERMA
absorbed dose
equivalent dose
effective dose
what are the two categories of radiation measurement?
air and tissue
what does the radiation in air measure?
measures the radiation intensity
what are the units used to measure radiation intensity (air)
exposure
air KERMA
what does the radiation in tissue measure?
measures dose
what are the measurements used to determine the effects of radiation on tissue?
absorbed
equivalent
effective
how is the intensity of the X-ray beam measured?
exposure
air KERMA
tells us how radiation is coming out of the x-ray tube
how is the leakage radiation from the tube measured?
exposure
air KERMA
how is the INITIAL dose the healthcare provider and pt receive called?
absorbed dose
what does absorbed dose tell us?
absorbed energy
short term effects-skin erythema or hair loss
does NOT do a good job of detecting long-term effects such as cancer
effective dose
solely used to detect long-term effects such as cancer
not used to calculate short-term effects and absorbed energy
if mA is increased what happens to intensity, exposure KERMA, and absorbed equivalent, effective doses?
it increases everything because each calculation is influenced by the same variables
radiation in the air is measured by
exposure
Air KERMA
absorbed dose measures
radiation in tissue
equivalent dose measures
effects of radiation on tissue
what does ESE stand for
entrance skin exposure
ESE measures
the intensity or quantity of radiation in air at the level of the patient’s skin
DAP is used to measure
the total amount of radiation delivered to the patient from diagnostic imaging equipment
if kvp is increased what happens to intensity, exposure KERMA, and absorbed equivalent, effective doses?
it increases everything because each calculation is influenced by the same variables
if distance is increased what happens to intensity, exposure KERMA, and absorbed equivalent, effective doses?
results in the decrease of all the values due to the inverse square law
how does a decrease in kvp affect the absorbed dose to the pt?
decrease in kvp affects the absorbed dose
it also decreases the average energy of the x-ray beam and the total number of photons created
fewer photons means less dose is absorbed by the pt
what are the three types of methods used to quantify radiation in tissue
effective dose
absorbed dose
equivalent dose
radiation that escapes the protective housing of the tube is known as what?
leakage
what is another form of secondary radiation?
scatter
how is scatter produced?
Compton scattering
what is attenuation
is a loss of intensity of the X-ray beam as it passes through matter
what is considered primary radiation
radiation that:
- produced within the pt
2.scatter from interactions within the pt - that escapes the protective housing
- exits the window in the tube housing
radiation that exits the window in the tube housing
what does an X-ray beam interact with as it interacts with matter?
interact with air molecules and knock out an electron out of its orbit
ionization
what does exposure measure?
the number of ionizations in air
how is the X-ray beam’s intensity measured?
through exposure
increase in the x-ray beam leads to the increase of what?
ionizations and exposures
the number of ionizations is directly proportional to what?
number of photons in the x-ray beam
this is the reason why if ionization is increased then exposure (the number of ionization in the air) will increase too
what are the units of exposure?
coulombs/kilogram
what does Coulombs measure?
measures charged particles
1 coulomb is equal to what?
6.242x10^18 ionizations
if mA is increased what happens to photons, ionization, exposure
all increased because the same variables influence all the calculations
if distance is increased what happens to photons, ionization, exposure
all decrease because the same variables influence all the calculations and due to the inverse square law
what does air KERMA measure
measures the energy of ionizations in the air
what does KERMA stand for
kinetic
energy
released per unit
mAss
if the intensity of the beam is increased what happens to ionization energy and air kerma
it increases
what are the units for kerma?
gray
what does 1 gray equate to
1 joule/kilogram
you can use exposure and air kerma to measure
test radiation coming from the tube
measure leakage radiation
measure scatter radiation
how is exposure different from air kerma?
measures only the # of ions in the air
units are coulombs/kilogram
how is air kerma different from exposure?
measures the energy of ions
units are gray
when measuring the intensity of the primary beam what dosimeter position will demonstrate the highest air kerma
the measurement that is closest to the tube
primary bi-product of x-ray interactions in air is
free electrons
the process that x-rays created charged particles such as free electrons
ionization
which of the following best describes radiation exposure
quantity of radiation:
- directed at the pt
- absorbed in the pt
- Passing through the pt
- energy absorbed in the air
quantity of radiation directed at the patient
some of the radiation is absorbed by the tissues of the body where does some of this energy go?
it is absorbed in the photoelectric effect and Compton scattering
what is the total amount of energy absorbed in the body as a result of Compton scattering and photoelectric effect is known as?
absorbed dose
what is the definition of absorbed dose?
energy absorbed in the body per unit mass
remember to think of its units
joule=energy
kilogram=mass
The SI unit of measurement for absorbed dose
gray
radiation effects on tissue
equivalent dose
effective dose
absorbed dose formula
joules/kilograms
what effects does the equivalent dose take into account?
the effects of different radiation types have on anatomy
the type of radiation with the highest equivalent dose
alpha radiation = 2EqD
what is the effective dose used for?
used to assess the degree of radiation including biological damage per different tissue types
what tissue has the lowest tissue weighting factor?
brain (0.01)
what is the weighting factor for X-ray?
1
why is the absorbed dose used?
it is used to predict short-term or early radiation injuries
examples of short-term radiation injuries
sperm depression
skin erythema
epilation
what kind of tissues absorb more radiation
tissues that have
a high atomic number
high density
when looking at a radiograph what do the dark areas represent?
low absorbtion of the x-ray
means it has low z# and low density
what are examples of tissues that absorb a minimal amount of radiation?
tissues that have air
fat
what is an example of a tissue that absorbs a moderate amount of radiation (appears gray on a radiograph)
muscle
what is the absorbed dose affected by?
mA
kVp
distance
density and z#
what is the definition of linear energy transfer?
the rate at which radiation energy is deposited in matter
what causes more biological harm?
higher LET
true or false X-rays have a high LET
false
true or false alpha particles have a high LET
true
what is the formula for an equivalent dose?
EqD=D(absorbed dose) xWr (radiation weighting factor)
what happens to relative biological effectiveness, radiation weighting factor, and equivalent dose if LET is increased?
everything is increased
what is the purpose of the equivalent dose?
used to compare the biological damage from different radiation types
factors that affect equivalent dose?
radiation type
absorbed dose
mAs
kVp
exposure time
distance
units for equivalent doses?
sierverts
the formula for effective dose
EfD= D (absorbed dose) x Wr (radiation weighting factor) x Wt (tissue weighting factor)
the most sensitive tissue to radiation is
bone marrow
the least sensitive tissue to radiation is
brain
why are the values of effective dose and equivalent dose different despite having the same value of absorbed dose?
tissues have different sensitivities to radiation therefore they have different tissue weighting factor
what is another term for effective dose?
whole body dose
why would we use an effective dose?
to compare the risk of cancer based on different radiation types and tissue types
identify long-term effects of radiation exposure
factors that affect effective dose?
absorbed dose
radiation type (Wr)
tissue type (Wt)
mAs
kVp
distance
what do you do if a question asks you to calculate the effective dose when there are two different types of tissues?
you add the values up and then multiply by the absorbed dose and radiation weighting factor
what factors are needed to calculate an effective dose?
absorbed dose
exposed tissue types
radiation type
true or false the skin is sensitive to radiation
false
the risk of radiation-induced stochastic effects is reduced by adherence to which of the following dose limits?
effective dose limits to the whole body
why are vital signs important in medical imaging?
helps evaluate the critical functions of the body
what is the normal temperature for an adult?
98.6 (oral)
how many degrees difference is the tympanic temperature?
+1
how many degrees of difference is the axillary temperature?
-1
how many degrees difference is the rectal temperature?
+1
what is the pulse rate?
the number of pulses per minute
what is pulse amplitude?
signifies the strength of the pulse
what is the average pulse rate?
60-100bpm
what is the definition of blood pressure?
The lateral force exerted on the arterial walls.
what is the average blood pressure of a healthy adult?
systolic (contraction)=100 to 120
diastolic(relaxing)= 60-80
what is the definition of respiratory rate?
is the number of breath cycles (inspiration and expiration) per minute
what is the average respiratory rate?
12-20 breaths per minute
what tool is used to measure oxygen saturation in the blood?
pulse oximeter
what is the normal percentage of oxygen saturation?
90-100%
which blood pressure reading is associated with the left ventricle?
systolic
what should a technologist do if you identify an abnormal viral sign in a pt?
stop the procedure
help stabilize the pt
call for help
the diastolic bp is a measurement of the pressure exerted on the arterial walls during
relaxation of the left ventricle
In a trauma situation which two arteries are best for assessing a pt pulse due to their larger size?
carotid
femoral
what is an EKG?
it is an electrical image of the heart
what is the P-wave in an EKG?
represents the electrical activity through the atria
what is the QRS complex?
movements of electrical pulses through the ventricles
aka ventricular systole
what is the ST segment?
shows the ventricles contracting but no electrical activity is flowing through it
what is the T-wave?
shows when the ventricles are resetting electrically and preparing for their next muscle contraction aka ventricular diastole
when is ekg used in medical imaging?
EKG gating
it allows images of the heart without motion blur and images are collected in between beats
the first phase of contraction of the heart involves the contraction of the
right and left atria
from the ventricles, blood is pushed
into the pulmonary artery and aorta
how many leads are connected to the pt during an EKG
3
what are the two types of lab testing that are used in diagnostic imaging?
kidney function
blood clotting
what is BUN?
blood, urea, nitrogen
normal: 7-21
What kind of health condition is associated with a BUN above 21
means the kidneys are struggling to function properly
What kind of health condition is associated with a BUN above 50
suspected renal failure
do not give intravenous contrast
what is creatinine?
chemical byproduct of metabolism (muscles)
normal: 0.7-1.5
creatine value of 1.5 indicates
pt kidney cant filter iodinated contrast
what factors affect the value of creatinine?
age
gender
muscle mass
hydration status
why is identifying creatinine levels important in diagnostic imaging?
can be a contraindication for injecting IV contrast
ONLY when the level is HIGH
what is GFR
glomerular filtration rate
estimates the filtration of the kidneys
normal: 90-120
what does a GFR level below 90 indicate?
pt kidney is not properly functioning to filter out the contrast
what factors affect GFR?
age
gender
muscle mass
hydration status
what is a pt test?
prothrombin time measures the liquid portion of blood to clot
normal: 11-13.5s
what contraindication is associated with a patient whose pt is above 13.5s
patient’s blood is not clotting properly
what is a ptt test?
partial thromboplastin time
normal: 25-35s
what is an INR test?
international normalized ratio
identifies blood coagulation
normal: 0.8-1.2s
what is the platelets test?
identifies blood coagulation
normal: 150k-400k
what does a high platelet count indicate?
clotting disorders
what does a low platelet count indicate?
bleeding disorders
what are the contraindications for interventional or invasive procedures?
PT
PTT
INR
platelets
what are the contraindications for intravenous contrast?
BUN
Creatinine
GFR
what information would a GFR test provide?
rate at which the kidneys filter waste from the blood
true or false water-soluble iodine is the only contrast that is considered safe for IV injection
true
what is an ionic contrast?
when placed in a solution it breaks up into ions (charged)
NOT desirable
why is ionic contrast not desirable?
due to charged particles, it is highly toxic
high osmolarity
what does the term osmolarity refer to?
concentration of particles in a solution
what factors should be taken into account before a pt is given contrast?
diet
renal function
allergy premedication
what are the diet factors pts need to take into account before contrast injection?
pre-hydrated for 1 day
NPO for 1 hour
post hydration 1 day- reduces the toxicity of contrast
what lab tests need to be done before IV contrast injection?
BUN
creatinine
GFR
what are some medications that are used for pt who have an allergy to iodine?
corticosteroid (prednisone)
anti histamines (benadryl)
what is the most common complication of IV contrast injection?
extravasation- leakage of contrast outside the vessel
what can the pt experience when there is extravasation?
swelling
burning
tightness
what do you do if there is extravasation present?
inform radiologist
elevate the extremity
hot and cold compress
what are some common allergic reactions to contrast (mild)
scattered hives
pruritus
rhinorrhea
coughing
what do you do if a pt is experiencing a mild reaction?
monitor 20-30 mins
monitor vital signs
antihistamines
what are examples of a moderate reaction?
diffuse hives
persistent vomiting
laryngeal edema
tachycardia
what do you do if a pt is experiencing a moderate reaction?
monitor pt
vital signs
IV access
antihistamines
what are examples of a severe reaction?
altered mental status
pulmonary edema
laryngeal edema
tachycardia
what do you do if a pt is experiencing a severe reaction?
code blue
epinephrine
what is nephrotoxicity?
decrease in renal function following contrast administration
risk is increased if there are past renal issues
what drug is administered to a pt who is experiencing an allergic reaction to iodinated contrast?
diphenhydramine
why is barium a common contrast agent?
high atomic number (56)
allows for a higher attenuation
is barium sulfate water soluble?
No
what is it called when barium is introduced into the GI tract?
enteral
what is it called when barium is introduced outside the GI tract?
parenteral
intrathecal
intra-articular
intravenous
is barium sulfate water safe for parenteral injections?
no
what do you do if there is a perforated bowel in the GI tract?
do not use barium
only use water-soluble iodinated contrast
what is the CR for RAO sternum?
center at T7 and 1 inch from the midsagittal plane
what is the recommended SID for an RAO view of the sternum?
30 inches
how much rotation is needed for an RAO view of the sternum?
15-20 degrees
in a ribs series for a PA view where do you pout the affected side?
place anterior injuries or affected side close to the IR
What is the SID for a rib series?
40 inches
what is the CR for AP lower ribs?
on the midsagittal plane midway between the xiphoid process and the lower rib margin
what ribs need to be included in the lower rib view?
ribs 8-12
what ribs need to be included in the upper rib view?
ribs 1-10
what is the SID for oblique upper ribs?
72 inches
what is the CR for oblique upper ribs?
midway between the jugular notch and xiphoid process then move towards the lateral side in question
what is the purpose of doing oblique ribs?
shows the posterior portion
what is the appropriate placement of the top of the IR for an AP above ribs?
1.5-2 inches above the shoulder
which two views of the following would best demonstrate a pt who is experiencing left anterior rib pain?
PA of the affected side
RAO
what needs to be demonstrated on a diagnostic AP KUB
lower diaphragm
pubic symphysis
soft tissue anatomy within the abdominal cavity
For AP upright KUB how is the midsaggittal plane positioned?
perpendicular to the IR
what is a diagnostic dorsal decubitus KUB?
free of motion
superimposed ilia
lumbar vertebrae pedicles and open intervertebral foramina
what is the CR for dorsal decubitus KUB?
2 inches above the crest
when performing a decubitus KUB why do you need to place the pt on a radiolucent pad? (PT is a on a stretcher)
elevates the pt off the stretcher or x-ray table. Ensures that the side down is included in the radiograph
why are KUBs ordered?
tube and line placement
abdominal pain
kidney stones
what is the most distal portion of the small bowel?
ileum
which quadrant is the gallbladder found in?
RUQ
which organ is positioned transversely across the upper abdomen?
pancreas
what is a series circuit?
a circuit where all the lines are connected end to end in a line
What is the difference between a series and a parallel circuit?
series circuit has one line and the current flows in one direction and is constant but the voltage drops at each resistor.
parallel circuit has multiple sections that break off from the main circuit. The current is not constant but the voltage is
pro of series circuits?
uses simpler wiring
easier detection of faults in a circuit
cons of series circuits?
if one component stops working then the entire circuit stops working
total current forumla
- the total current in a series current is the same as any current through any resistor
I(t)=I(1)=I(2)=I(3)
this is because the current flows in one direction
- total resistance is equal to the sum of all individual resistances
Rt=R1+R2+R3
voltage drop
voltage changes at each resistor
total voltage
Vt=V1+V2+V3
what is Ohm’s law?
V(voltage)=I(current) x R(resistance)
the resistance of electric flow through a circuit is measured in
ohm
a series circuit is a circuit in which components are connected.
to the power source end to end in a line
in a series circuit, all resistors share what?
the total voltage of the circuit
in a series circuit question when it asks what is the total voltage how do you solve the problem?
multiply the Amps to each of the resistances and then add their values together
in a series circuit question when it asks what is the total resistance how do you solve the problem?
you just add up all the resistance
what is a parallel circuit?
network of electrical components each connected to the power source by a different path
maintains the consistent voltage across the circuit
if a component fails in a parallel circuit what happens?
the circuit continues to operate but because each component is connected to the power separately
formula for calculating total resistance in a parallel circuit
1/rotal resistance(Rt)=1/R1 + 1/R2 + 1/R3
in a parallel circuit does voltage fluctuate across the circuit?
no
which of the following measurements remains constant in a parallel circuit?
volts
what is the purpose of Ohm’s law?
describes the relationship between voltage, resistance, and current within an electrical current
what does Ohm’s law state?
current is directly proportional to voltage and inversely proportional to resistance
what is voltage
the force that pushes electrons through a circuit
what is resistance
the force that slows down electrons in a circuit
what is current?
the rate at which electrons flow through the circuit
what is the voltage formula?
V= I x R
what is the resistance formula?
R= V/I
what is the current formula?
I= V/R
what is the relationship between current and voltage according to Ohm’s law?
as current increases, voltage increases
what is the relationship between current and resistance according to Ohm’s law?
as current increases, resistance increases
in a series circuit, all resistors share which of the following
the total voltage of the circuit
what remains constant in a series circuit
current
The name of the first X-ray tube?
Crookes tube
The modern X-ray tube is based on this type of tube.
Coolidge tube
leakage radiation must fall below this number
100m Roentgens /h at one meter (3.2 feet) from the tube
The charge of the cathode
negative
the charge of the anode
positive
the glass envelope of the X-ray tube is composed of
Pyrex glass
the filaments are located within
the focusing cup
the lowest kv setting possible for producing characteristic radiation
69 kvp
what is the purpose of the cathode?
creates free electrons through thermionic emission
what is the purpose of the anode?
absorbs electrons and creates X-rays
what is the purpose of the glass envelope?
creates an air-free vacuum around the cathode and anode
prevents the tube from blowing up or corroding
what is the glass envelope made out of?
borosilicate glass (pyrex), metal, or ceramic
what is the purpose of the tube housing?
prevents X-rays from being emitted throughout the exam room
how much leakage radiation does the tube housing need to keep?
maximum (0.88 mGy/hr)
what is the effective limit of mA that can be used?
1000
what is it called when a cathode tube has 2 filaments?
dual focus
what is the purpose of the small filament (cathode)?
creates a tight and very narrow X-ray beam which allows for high spatial resolution
small mA
used on small anatomy
small exposures
A narrow electron beam increases what?
spatial resolution
what are the benefits of stationary anode?
simple design
used for low exposures
what are the cons of stationary anode?
low heat capacity
benefits of a rotating anode?
high heat capacity
high exposures
what is responsible for rotating the anode?
induction motor
induces the anode to spin
what is the induction motor composed of?
2 stators- electromagnets that help turn the rotor
rotor- rotating tube shafe attached to the anode disc
bearings- low friction spheres that allow for free rotation of the rotor
the term space charge within the X-ray tube refers to
free electrons
what are the two interactions that occur on the anode and are responsible for the creation of X-ray photons?
bremsstrahlung radiation and characteristic radiation
what is the principal advantage of using the large filament within a dual-focus X-ray tube?
increased heat capacity
The typical angulation of the anode is between
6 to 20 degrees
what is the purpose of the anode angle?
increases the surface area of the focal spot which increases the ability of the anode to absorb heat
decreases focal spot size which increases spatial resolution
what are the cons of the anode angle?
causes a variant of the beam intensity
higher intensity on the cathode side rather than the anode
what is the anode heel effect?
decreased x-ray beam intensity on the anode side of the beam
as the anode angle decreases heat dissipation
decreases
as the anode angle decreases the heel effect
increases
as the anode angle increases spatial resolution
decreases
as the anode angle increases the surface area
increases
beam intensity is greatest closer to
cathode
It is recommended to place the abdomen under the ________ side of the x-ray tube
cathode
As SID increases, the heel effect
decreases
As field size increases, the anode heel effect
increases
how can the anode heel effect be used as an advantage?
In a KUB for example place the thinnest portion of the patient under the anode side of the beam this allows for a more even exposure of the IR
the anode heel effect is defined as a variation in which of the following?
beam quality across the X-ray field
the use of an X-ray tube with a large anode angle results in
increased
focal spot size
heat capacity
the use of an X-ray tube with a large anode angle results in
decreased:
focal spot size
heat capacity
True or false the cathode side always have a higher intensity than the CR?
true
what is a potential negative consequence of an increased anode angle?
increased effective focal spot
what happens if the anode angle decreases?
effective focal spot decreases and the heel effect increases
what is the line focus principle?
relationship between the actual focal spot on the anode and the effective focal spot that extends from the anode
what does the line focus principle affect?
heat capacity, spatial resolution, and beam coverage
what is the actual focal spot?
located on the anode
the physical area where electrons are converted into X-rays
what is the effective focal spot?
the width of the X-ray beam as it is projected at the patient
what does an effective focal spot influence?
affects the creation of penumbra and spatial resolution
what does a small effective focal spot allow for?
decrease penumbra
increase spatial resolution
what are the pros of having a smaller anode angle?
very narrow effective focal spot
well aligned beam
high spatial resolution
what are the pros of having a smaller anode angle?
reduces the size of the actual which means more concentrated heat
smaller exposure factors
smaller field size (beam coverage)
when would you use a small anode angle?
extremity imaging
dental
mammography
when would you use a large anode angle?
large exposure techniques and large field size
ex: spine, KUB, pelvis
does off-focus radiation increase patient dose?
yes because it exposes the pt outside the collimated area
does off-focus radiation reduce spatial resolution?
maybe processed as part of the image resulting in decreased spatial resolution
caused by failure of histogram analysis
how would you fix off-focus radiation?
use post-shuttering to eliminate any miss exposed areas
how does off-focus radiation occur?
occurs when electrons collide with tube components outside of the focal spot
which component of the X-ray tube contains the focal spot?
anode target
during the histogram process, the computer may identify off-focus radiation as
values of interests
what areas should be shuttered? (off-focus radiation)
bright white
collimator shadows
what does tube loading refer to?
refers to the heat created within the X-ray tube
what is the equation for heat units?
kvp x mAs x w
w=wave form factor
what is the purpose of a tube rating?
refers to max exposure allows exposure factors can be safely used without overheating the tube (kvp, mAs)
what are the tube loading factors?
exposure time
anode angle
filament size
anode rotation speed
if the exposure time was increased and the mA was decreased what happens to the heat capacity?
it increased due to the longer exposure time which gives it more time to dissipate heat
what is the waveform factor for a 3-phase six pulse x generator?
1.35
you can reduce the chance of excessive heat production and X-ray tube damage by modifying the
filament size
what is the purpose of the anode cooling chart?
time before taking another exposure (mAs)
when using a large anode angle this results in
increased focal spot (larger)
increased heat capacity
what is contrast?
visible difference in brightness between two adjacent areas in the image
an image with a large number of BLACK and WHITE shades
high contrast
short grayscale
an image with many shades of grey
low contrast
long grayscale-more white or grey
short scale
high contrast
less shades of gray
the material used for strips in grids
lead (most common)
tungsten
platinum
what affects image contrast?
kVp and grids (procedural factors)
patient factors (size and pathology)
computer processing
post-processing
monitordisplay caibraation
what is a part of the computer processing step?
histogram analysis
lookup tables
both affect contrast if values are wrong
which of these terms describes a radiographic image with widely varying brightness
short scale
high contrast
which factor is the most important factor controlling image contrast in radiography
computer processing
what is the grayscale?
total brightness levels visible in the image
high contrast is defined by
short grayscale and a few shades of grey
low contrast is defined by
long grayscale and many shades of grey
which of the following might make it difficult to visualize the anatomy and pathology of the abdomen
long grayscale and many shades of grey
long grayscale is synonymous with
low contrast and many shades of grey
large visible differences in brightness are defined as
short gray scale
high contrast
few shades of grey
factors that influence image contrast
kVp
OID
grids
filtration
collimation
decrease OID=______________image contrast
decreased image contrast
low contrast
high grid ratios=___________image contrast
increased
high
increased collimation=______________image contrast
increase
tight collimation=_____________scatter
decrease
increasing exposure field=____________________image contrast
decreased
large exposure field=______________scatter
increase
decreasing kVp by 15% has what effect on image contrast?
increase image contrast
which is preferable in diagnostic images high or low contrast?
high contrast because it makes anatomic structures more visible
what are procedural factors?
variables that the technologist can control as part of the exposure
true or false procedural factors such as kvp, grid ratio, and collimation have more influence on image contrast
false because computer processing algorithms are good at correcting images
why does image contrast exist?
signal differences in the remnant beam called differential attenuation
high signal difference=
high contrast
what are the signal intensity influencing factors?
kvp
grid
collimation
when changing the kvp what does that affect in terms of image contrast?
influences signal difference in remnant beam
why do we use grids?
high signal difference=less scatter
increased contrast
what is the term to describe the signal difference in the remnant beam?
differential attenuation
which tissue type corresponds to the highest signal intensity at the IR
bowel gas
has extremely low density which means it attenuates with very little radiation
what is the definition of image contrast?
visible difference in adjacent brightness levels within the radiographic image
what is the definition of subject contrast?
magnitude of the signal difference in the remnant beam as a result of the different absorption characteristics of the tissues and structures making up the part
when looking at the heart on a cxr it will have a low absorption and high signal
no, it will have a high absorption due to its high density and a low signal
why is barium used in GI studies?
because the abdomen has uniform moderate absorption which means they have lower image and subject contrast. Barium helps highlight the anatomy.
A pt has a bowel obstruction How does that affect image and subject contrast?
both increase due to the large amount of air in the abdomen
A pt has bowel ascites (fluid in the abdomen) How does that affect image and subject contrast?
both decrease due to the large amount of liquid in the abdomen
when imaging a bariatric pt for a cxr what happens to the subject and image contrast?
decreases causing the image to look more washed out
what is the primary factor controlling subject contrast?
the absorption characteristics of the tissues and structures being exposed
what term describes a body section that creates a remnant beam having widely varying signal intensities
high subject contrast
imaging subject contrast increases the visibility of anatomy and pathology due to
increased brightness differences between adjacent structures
which contrast factor has the most influence on the image contrast?
digital factors
what is a histogram?
graphical representation of the collection of all exposure frequencies capture by detectors
what is a lookup table?
mathematical process that converts low-contrast raw data into high-contrast image data
what does window width show?
shows the contrast displayed within the image
what happens when the window width is increased?
increases the amount of grey within the image (less contrast)
what computer process adjusts raw radiographic data to create more contrast in the processed data?
lookup table application
which of the following is an image processing factor that influences radiographic image contrast?
histogram analysis
what is the definition of structural resolution?
structural sharpness recorded in the radiographic image
differentiate between different anatomy in a certain area
what are the units for spatial resolution?
line pair per millimeter (LP/mm)
what affects spatial resolution?
patient factors
beam geometry
IR factors
digital image factors
digital display factors
-pixel size
-pixel pitch
-matrix size
which anatomical parts can be used as an indicator of the spatial resolution recorded in a radiographic image?
trabecular bone
what are the patient factors?
-PT size
-PT movement
what are the beam geometry factors?
-SID
-OID
-Focal spot size
what are the image receptor factors?
-detector element size
-pitch
-fill factor
what are the digital imaging factors?
-pixel size
-matrix size
what are the digital display factors?
-pixel size
-pixel pitch
-matrix size
-fill factor
what happens if OID is increased?
leads to lower spatial resolution which causes blurriness this is known as penumbra
what should you do when pt size or pathology is degrading the spatial resolution?
increase SID
focal spot blur formula
FSS x (OID/SOD)
SOD= SID-OID
what is an ideal scenario for maximum spatial resolution?
large SID
Small OID
small effective focal spot
no tube angles
decrease in element size would lead to
increase spatial resolution
what is pitch
it is the distance between one detector element to the next
what is the fill factor?
fraction of the del surface area that is capable of measuring incoming X-ray beams
which part of the X-ray beam has different signal intensities that correspond to the anatomy represented on the image IR
remnant beam
what does DEL stand for in digital radiography?
detector element
which of the following describes the detector element pitch
distance from one DEL to another
what is the definition of matrix size?
the number of pixels in an image
if the matrix size increases_______________
pixel size decrease
what happens to the image if there is a low receptor exposure (fewer photons hit the IR)
quantum mottle
what is the recommended size for monitors for routine radiography?
3MP
what happens to the image if there is a high receptor exposure
saturation
what affects receptor exposure?
prime exposure factors
influencing factors
what are the prime exposure factors?
mA
exposure time
kVp
SID
what are the influencing factors?
AEC
Grids
filtration
collimation
anode heel effect
patient factors
if mAs is increased________________
the number of photons increases which means there will be more photons striking the IR
if kVp is increased how does this affect the beam?
adds more penetrability
15% rule
increasing kVp by 15% will double receptor exposure
a technologist can identify an image with excessively high mAs based on
an exposure indicator outside of the acceptable range
if the angle of the tube is increased how does that affect the anode heel effect?
decreases it
magnification is the consequence of the
divergent beam
factors that affect magnification
OID
SID
SOD
magnification factor formula
SID/SOD
tells us the actual size of the object-based image on the radiograph
what are the two types of shape distortion?
foreshortening
elongation
how does foreshortening occur?
when the anatomy is not parallel with the IR
how does elongation occur?
tube and receptor are not perpendicular to each other
law of isometry
central ray should be set at half of the angle formed between the object and IR
what projection has foreshortening
lordotic chest
an increase in tube potential would increase receptor exposure by increasing which two of the following?
penetrating ability of the beam
number of photons in the beam
what is most likely the adverse effect of processing an image under the wrong anatomic part?
incorrect image contrast
what term describes the light-emitting components within display monitors?
picture element (pixel)
what computer processing features influence radiographic image contrast?
histogram analysis
look up table
what is referred to as size distortion?
magnification
how does increased kvp affect differential attenuation of the X-ray beam
decreased differential attenuation
large signal differences in the remnant beam will produce a radiographic image demonstrating
high image contrast
how does increasing window width affect the displayed image?
decreased contrast
receptor exposure is affected by
generators
collimation
filtration
the distance between the anatomy being imaged and the focal spot within the X-ray tube is called
source to object distance
when the anatomy being imaged is PARALLEL to the IR and the beam is angled what type of shape distortion is this?
elongation
the term used to describe signal differences in the remnant beam
differential attenuation
matrix size increases______________________
increased spatial resolution
matrix size increases the size of the pixels_________________
increase
grayscale
the total brightness levels that are visible in an image
what post-processing factor affects image contrast?
window width
what is the CR for AP thumb?
1st MCP joint
for PA hand the pts arm should be bent ______________________
90 degrees
Coyle method for the coronoid process
Entering the joint at mid-elbow at a 45° angle towards the coronoid process
the tube is positioned above pt
80 degree elbow bend
Coyle method for radial head
Entering the joint at mid-elbow at a 45° angle towards the radial head
tube in front of pt
90 degree elbow bend
CR for transthoracic humerus
Injured humerus against the image receptor
Perpendicular to the image receptor
Level of the surgical neck
Mid-coronal plane centered to the midline of the image receptor
for transthoracic humerus what must be seen in the lungfield
proximal humerus
greater tubercle in profile
What is ALARA?
as low as reasoning achievable
time
distance
shielding
what is the primary source of occupational dose?
the pt
why is lead used for shielding?
high atomic number
high mass density
high attenuation
what is used to measure shielding?
half-value layers
what lead thickness equivalence is required for protective lead aprons in surgery, general radiography, and fluoroscopy?
0.50mm lead
lead thickness for glasses
0.35mm lead
lead thickness for gloves
0.25mm lead
lead thickness for bucky slot
0.25mm lead
what does positive beam limitation do?
automatically adjusts collimation to adjust to detector size
use of lead to reduce the exposure field size has what effect on radiographic image quality?
increase image contrast
what material are the collimator blades made out of?
lead
positive beam limitation is a safety feature that ensures the size of the X-ray field is no larger than
the detector dimensions
the component of the X-ray assembly that is manipulated by the operator to precisely define the size of the X-ray field
adjustable collimation
the primary benefit of collimating the exposure field size to the required anatomy is
decrease in pt effective dose
entrance skin dose
photons that do not have enough energy to penetrate the pt which are then absorbed in the pt’s skin
what is the most common filtration material?
aluminum
gets rid of low-energy photons
why is aluminum used for filtration?
low atomic number
absorbs most low-energy photons
allows transmission of most high-energy photons
inherent filtration
results from the construction of the tube itself and filters the x-ray beam
glass envelope
insulating oil
window
mirror
inherent + added filtration=
total filtration
what is added filtration?
anything added to the X-ray machine
ex: aluminum
what is the minimum thickness of diagnostic filtration for x-ray tubes operating above 70kvp
2.5mm Al eq
the thickness of inherent filtration for general x-ray tube assemble is equal to
0.5mm AL eq
the thickness of added filtration for general x-ray tube assemble is equal to
2mm AL eq
how does decreasing filtration thickness affect the quantity of the beam
increased quantity
What is the CR for external rotation of the shoulder?
1 inch inferior to the coracoid process or 1 inch of light above the shoulder
What is seen in profile when performing external rotation of the shoulder?
Greater tubercle
What is seen in profile for a internal rotation of the shoulder?
Lesser tubercle
How is the hand position for an AP neutral view of the shoulder?
It is the palm of the hand is on the hip
How is the pt positioning for the Lawrence view?
Pt is spine
Affected arm is abducted (sticking out) and externally rotated resting on a sponge
CR enters the axila
Tube is turned 30 degrees to the table
IR and tube are parallel to each other
What is the purpose of doing the inferosuperior axial or Lawrence method (shoulder)
Demonstrates the relationship of the lateral humerus to the Scapulohumeral joint.
When performing the shoulder Y view where is the CR
Scapulohumeral joint
How do you position AP scapula?
40 SID
CR: 2 inches inferior to the coracoid process or put the top of the light field 2 inches above the shoulder
Place arm above arm to remove scapula from ribs
Exposed on slow respiration
How is lateral scapula positioned?
Affected side against IR
CR at medial aspect of scapula
If affected arm is placed behind back supinated=coracoid and acromion
Across chest= body of scapula
Appropriate criteria for a lateral view of scapula
Scapular body free of rib superimposition
Humerus does not superimpose area of interest
Why must a pt arm be abducted 90 degrees for AP scapula
Moves the scapula laterally to minimize superimposition of ribs
What is the breathing technique for AP clavicle?
Taken on expiration
What is the angle for AP axial clavicle?
15-30 degrees cephalad
What is the breathing technique for AP axial clavicle?
Inspiration
What is the SID for bilateral AC joints?
72 inches
What is the CR for bilateral AC joints?
CR is at the jugular notch
For weighed AC joints what breathing technique is used?
Exposed on expiration
What cassette size do you use for bilateral AC joints?
17x14
What breathing technique is used for AP external rotation of the shoulder
Suspend respiration
For AP hip why do we invert the pt feet?
Elongates the neck of the femur and puts the greater trochanter in profile
Where is the CR for unilateral frog leg hip?
Midway between the ASIS and pubic symphysis
What is the tube angle for danielus miller method
15 degrees posteriorly perpendicular to femoral neck
Positioning for AP axial anterior pelvis outlet view
Cepahilic angle: 20-35 men, 30-45 female
CR:1-2 inches distal to the superior border of pubic symphysis
Positioning for pelvis inlet view
40 degree cuadal
CR: at ASIS
what anatomic structures should be included in an AP axial outlet projection Taylor method?
pubic and ischial bones magnified with pubic bones superimposed over the sacrum and coccyx
what anatomy needs to be seen on the superior inferior axial inlet projection Bridgman method?
superimposed superior and inferior rami of the pubic bones and anterior pelvic bones
what are the requirements for x-ray production?
source of electrons
acceleratation of electrons
deceleration of electrons
where are the electrons produced in the tube?
the filament (cathode)
how are the electrons accelerated?
an electron voltage (kVp) is applied and causes a strong negative charge moving the electrons to the anode side
how are the electrons decelerated?
they strike the anode and release heat and X-ray
an increase in mA increases the number of ________________ and the number of _____________
electrons and photons
an increase in kVp increases the of ________________ and increases _____________
the energy of electrons and x-ray energy
true or false exposure time increases then the number of X-ray photons
true
what is the definition of exposure time?
the amount of time that the electrons are flowing through the tube and the x-rays are being created
the term of electron production
thermionic emission
what is the charge of the filament?
negative
the measurement of tube current
mA
the controller of X-ray intensity (quantity)
mAs
the controller of photon penetrability (energy)
kVp
what condition is required to induce thermionic emission within the cathode filament?
high current
when imaging an obese patient what technical factor needs to be increased?
kVp
a chest x-ray demonstrates excessive exposure. How do you decrease the intensity of the beam while maintaining the same beam energy?
decrease mA
brem radiation is produced
by slowing of an incident electron
the inner shell of an atom
k-shell
brem radiation involves
an incident electron and the nucleus of an atom
a brem photon is the result of
energy difference between the incident electron as it passes near the nucleus
the closer the incident electron passes to the nucleus
the higher the energy of the brem photon
how does brems radiation start?
high energy electrons interact with the nucleus of the tungsten atom
bremsstrahlung radiation is created within the X-ray tube when high-energy electrons interact with
electric field of the nucleus
the maximum energy of bremsstrahlung photon that can created during an x-ray exposure is equal to
the energy of the incident photon
the maximum amount of energy of bremsstrahlung photon is controlled by which technical factor
tube potential
the energy of the bremsstrahlung x-ray photon is equal to the
difference between the incoming and outgoing electron energy
the closer to the electron is to the nucleus
the stronger the binding energy
a characteristic X-ray can be defined as
total removal of an electron
Characteristic X-ray production involves
incident electron and inner shell of the electron
cascade effect
movement of an electron from an outer shell into an inner shell
the binding energy and unit of a tungsten atom’s inner shell
69 kEV
lowest kv setting possible for producing characteristic radiation
69 kVp
what technical factor is primarily responsible for controlling the energy of the x-ray beam
mA
what is the definition of attenuation?
a reduction in the x-ray beam intensity as a result of absorption and scatter in matter
what are the 3 x-ray interactions with matter?
transmission
absorbed
scattered
what does intensity refer to?
the number of x-ray photons
after the primary beam has interacted with the patient what is the x-ray beam called?
remnant beam
what are the 3 attenuation reactions?
photoelectric
coherent scattering
compton scattering
what does attenuation mean?
a reduction in the x-ray beam intensity as a result of absorption and scatter in matter
photoelectric absorption
then use of ionization to remove an electron in the inner shell and bring a photon in
coherent scattering
x-ray photon enters then is absorbed by the ENTIRE atom then the energy of photon is released in a different direction
Compton scattering
x-ray photon enters and is partially absorbed by outer electron and ionization takes place. Then remaining energy of the photon is released in a different direction
amount of attenuation is dependent on
part thickness
tissue density
atomic number
beam energy
an increase in anatomy thickness leads to increased_________________
attenuation
which radiographic projection results in the highest percentage of x-ray attenuation?
pelvis because it has more bone
true or false: coherent scattering does have an effect on pt dose?
false
no ionization
no biological harm
true or false: coherent scattering does have an effect on occupational dose dose?
false
scatter is directed toward IR
how does coherent scatter affect the image?
creates scatter
decreases contrast in the image
when does coherent scattering occur?
when there is low photon energy
least likely
true or false: photoelectric absorption does have an effect on pt dose dose?
true
ionization-damaging
true or false: photoelectric absorption does have an effect on occupational dose dose?
false
no scatter
true or false: photoelectric absorption does have an effect on image quality?
good effect because it creates contrast
what are the two products of PE interaction?
free electron
characteristic photon
how does increasing kVp affect the proportion of photoelectric absorption events that occur in pt tissues?
increasing kvp decreases the proportion of PE absorption
what the products of Compton scattering?
free electron
scattered photon
what is the product of coherent scattering?
scattered photon
true or false: Compton scattering is a benefit to pt, occupational dose, and image quality
false due to the ionization and the end product of scatter leads to an increase in exposure to both the pt and healthcare worker
more matter means____________
more scatter
how to reduce Compton scatter
decrease part thickness
use smallest field size
collimate
Use lower kVp
when imaging AP toes how much of an angle do you add to view the joint spaces?
15 cephalad
where do you center for an oblique toe?
MTP joint
how do you position for a lateral toe?
have the pt position like a lateral foot and then use tape to pull the toe in question outwards
how do you position tangential view of the toes?
wrap tape around pt toes and have them pull toes backwards. CR at first metastarsal
what is the recommended collimation for the tangential projection of sesamoids
1-2 inches on either side of the foot
positioning parameters for plantodorsal view of the calcaneus?
40 degree cephalic angle
CR to the base of the third metatarsal
dorsiflex foot
why is there a tube angle for AP foot?
to be perpendicular to the metatarsal joint space
why do we internally rotate 30 degrees for medial oblique foot?
to reduce superimposition of the cuboid
how much do you angle for AP knee
3-5 degrees caudal if ASIS measurement is greater than 19cm
no angulation 19-24cm
3-5 cephalad measurement of 24cm of less
what is the CR for lateral knee?
1 inch inferior to the lateral epicondyle of the femur
angle tube 15-20 degrees
tangential settlegast view Knee
patient is positioned like a sunrise tube matches angle of the IR (upwards)
CR at the knee joint
for the tunnel view of the knee how much should the knee be flexed?
40-60 degrees
for AP proximal femur how should the IR be placed?
top of the IR at the level of ASIS
lateral distal femur how should the IR be placed?
bottom of IR 2 inches distal to the patellar apex
x-ray photon
lots of energy
no mass
no charge
travels at the speed of light
what is wavelength?
measure of one peak to the next
true or false a decreased in wavelength results in an increase in crease frequency with means more energy
true
what units are used for frequency?
hertz
the x-ray beam is composed of one singular energy source
false because it is polyenergetic
what does the term quality refer to
average energy of x-rays
true or false x-ray beams travel out of the tube in all directions
true it is isotropic
electromagnetic spectrum
full range of photon energies
what is frequency
number of wave cycles per second
tube current refers to
flow rate of electrons
exposure time refers to
total amount of time that electrons are flowing
a tech is attempting to increase the x-ray beam intensity without modifying the overall energy of the x-ray beam they should
increase mA will increase the the quantity of photons but it won’t affect the overall energy of the x-ray beam
a tech is attempting to decrease the beam intensity and decrease the penetrability of the beam they should
decrease kVp
true or false if distance is increased then the beam quantity decreases
false
all technical modifications that will increase the beam quantity
increase mA
increase time
increase kVp
decrease distance
decrease filtration
decreasing SID will result in
increased concentration of photons
beam energy is measured in
Kev
kiloelectron volt
beam quality is influenced by
kVp
beam filtration
which of the following will add to the pt dose but not to diagnostic quality of the image
low energy photons
In a fluoro exam where is the x-ray tube positioned?
behind the pt
When using a C-arm when should the backwards R button be used
pt is prone looking away from the smiley face indicator
true or false pediatric fluoro is a sub category of conventional fluoro
true
what are the components of the IR in fluroro?
input phosphor
photocathode
focusing lenses
electrostatic
anode
output phosphor
what is the input phosphor composed of?
cesium iodide
what is the purpose of cesium iodide
helps improve spatial resolution of the image
what is the purpose of electrostatic focusing lenses of a fluoro tube?
helps funnel the photoelectrons into a concentrated stream
what is the output phosphor of the fluoro tube made out of?
zinc cadmium sulfide
what is flux gain?
kinetic energy gained during acceleration from photocathode to output phosphor
minification gain
concentration of photoelectrons from the input phosphor to the output phosphor
what is the flow of energy conversions in fluoro
1.digital signal
2. analog signal
3. light photons
4. photo electrons
5. light photons
6.x-rays
what happens at the input phosphor?
x-ray photons are converted into light photons
what happens at the photocathode
light photons»»photoelectrons
what does the electrostatic lenses do?
focus photoelectrons to anode
what does the output phosphor do>
photoelectrons»>light electrons
what is the purpose of the IR in fluoro imaging?
brightens the fluoroscopic image so that it can be of diagnostic value
what is the role of the anti scatter grid on the IR of the fluoro tube
increase image contrast
which component collects light photons from the output phosphor and converts them to electrons?
charge coupled device
what kind of grids does interventional radiology?
crossed hatched grid
why does fluoro use a lower grid ratio (less space in between)
uses higher kVP to penetrate contrast and lower mA to limit overexposure
where is the grid located in a fluoro tube?
in front of the input phosphor
brightness gain
measure of the ability of the image intensifier to increase the brightness level of them image
conversion factor
percentage that measures the efficiency of the image intensifier
formula for flux gain
output light photons/input x-ray photons
minification gain formula
D^2i/D^2o
i=input phosphor
o=output phosphor
D=diameter
brightness gain formula
flux gain x minification gain
conversion factor formula
intensity of light at the output phosphor/intensity of radiation at the input phosphor
during a fluoro exam what is the purpose of automatic brightness control?
adjusts exposure factors to deliver constant signal intensity to the image receptor
vignetting
decrease in image brightness around the edges of the image due to large OID
how is vignetting fixed?
image processing
adjusting image intensifier
reduce OID
pincushioning
parts of the image appear curved or bent inward towards the center of the image caused my external magnetic fields
how is pin cushioning fixed?
post processing
the components of flat panel detector
scintillation
photodiode
thin film transistor
what is RIS
radiology information system is like cerner and allows them to generate accession numbers
what is HIS
hospital information system
manages operational and healthcare data
DICOM
digital imaging and communications medicine
is universal language to exchange medical information
MIMPS
medical image management and processing system
functions like PACS
components of a CR cassette
2 protective layers
photostimulable phosphor- store and release energy
conductive- increases spatial resolution by absorbing light
support
reflective
raster pattern
related to the processing of CR cassette mirror and image plate
rapid back and fourth pattern
components of DR IR
photoconductor
Thin film transistor
ADC
indirect conversion DR systems
x rays
visible light
electronic signals
direct conversion DR systems
x-rays to electronic signal
what is the purpose of a TFT in DR
after the light photons are converted to electrical signal from the photodiode the electrical signal is then sent to ADC
formula for pixel size
field of view/matrix size
bit depth
total # of possible brightness levels that can be assigned to any given pixel in the digital image
quantiziation
process of assigning brightness levels
modulation transfer function
measures the accuracy of the image compared to the actual object
measures spatial resolution
dynamic range
range of exposures that can be captured by an IR
exposure latitude
range of exposures that produces quality images at an appropriate patient dose
detective quantum efficiency
a score that describes the ability of the imaging system to convert the remnant x-ray beam into a high quality image
capture efficiency
percentage of photons that get absorbed by the detector
chin to chest
what is the purpose of flexing for the C-spine
opens up the space between the spinous process
what is the purpose of extension for C-spine
closes spaces between the spinous processes
true or false when performing flexion of C-spine you do not need the body of the mandible
false
what is the SID for swimmers view?
40
what is the CR for swimmers view?
C7
what SID is used when performing a x-table spine
72
what is the CR for AP T spine
halfway between the jugular notch and the xiphoid process aligned with the midsagittal plane
what is the CR for lateral T spine
T7-arm pit level
make sure to have 1.5 inches above the shoulder
what is the CR for L5S1
1.5 inches inferior crest
2 inches posterior to ASIS
what is the CR for lateral coccyx
3.5 inches posterior from ASIS and 2 inches inferior from ASIS
what is CR for SI joints AP
2.5 inches inferior to ASIS
30 Cephalad tube angle
what is the CR for oblique SI joints
At ASIS and go 1 inch medial
obliquity for SI joints
25-30 degrees
CR for oblique L spine
1.5 inches superior of crest and 2 inches medial from ASIS
stochastic effects
Ex: cancer
random and unpredictable
probability increases as the dose increases but not the severity
AKA non threshold dose
deterministic effects
cataracts, epilation, ,diminished sperm count
only occur when specific dose thresholds are reached
severity of illness increases with the dose
dose for decreased sperm count
150 mGy
dose for epilation
3000 mGy
true or false? cancer be caused by any dose of radation
true
what is the chief biological cause of radiation?
Ionization
target theory
adverse radiation effects are only observed when sensitive target molecules in the cells are affected
what is direct action?
it is when x-ray photon or free electron interacts differently with DNA
RARE
what is indirect action?
AKA radiolysis
x-ray photon interacts with water which breaks into ions that can cause biological damage
double strand breaks
are difficult to repair
low probability of completely fixing
how are double stand breaks caused
indirect action
what are the 3 forms of DNA damage
base pair lesion
single strand breaks
double strand breaks
what is the product of indirect action?
free radicals
early effects
manifests soon after exposure
examples of early effects
skin burns
hair loss
diminished sperm count
AKA deterministic effects
skin erythema occurs
2 Gy or more
late effects
manifests after years of exposure
delayed effects
late effects examples
cataracts and cancer
latency period
period of time between exposure and when symptoms start occuring
true or false late effects are considered deterministic
true
why doesn’t ARS occur in diagnostic imaging?
the entire body needs to be exposed to a very high dose of radiation
hematopoietic syndrome occurs at
at least 1 Gy
Gi syndrome occurs at
at least 10 Gy
cerebrovascular syndrome occurs at
at least 50 Gy
hematopoietic syndrome
inadequate blood cell production/destruction of bone marrow
GI syndrome
destruction of GI tract
pt often die of dehydration and electrolyte balance
cerebrovascular syndrome
damage to the cerebrovascular structures of the brain
prodromal phase
body’s initial reaction to high doses of radiation exposure
latent phase
initial illness appears to resolve
inverse related to the dose
manifest illness
full onset of systemic illness
directly related to dose
what is used to determine how often pt die from ARS
LD50/60
lethal dose of radiation that kills 50% of the population within 60 days
what are the four stages of disease progression
prodromal
latent
manifest
recovery/death
law of bergonie and tibondeau
the most radiosensitive cells are:
immature
unspecialized
rapidly dividing
in the fetal cycle which part of the cycle is the most radiosensitive
pre implantation stage
100 mGy
physical malformations tend to develop in which part of the fetal cycle
organogensis
cerebral effects tend to occur in which part of the fetal cycle
fetal period
variables that affect radiosensitivity
age
tissue type
gender
type of radiation
rate of exposure
tissue radiosensitivity is important when determining which form of measurement
effective dose
densely ionizing
high LET
deposits energy within a shorter distance
causes more damage
oxygen enhancement ratio
the difference in biological harm for each radiation type
which type of cell is the most radiosensitive?
hypoxic cells
fractionation
tumor is exposed to numerous small doses rather than one large dose
what is the OER of x-ray
3x
LET is commonly measured in units of
kiloelectron volts/micrometer
relative biological effectiveness
radiations ability or effectiveness in causing biological damage
What happens if the image is underexposed?
Mottle
Grainy image
Increase kVp and mAs
Receptor exposure
The amount of radiation striking the receptor
Exposure indicator
Numerical expression of the receptor exposure
the process that converts original radiographic histogram to the expected histogram
rescaling
the process that identifies the values of interest in a radiographic histogram
histogram analysis
the process of adding brightness and contrast to exposure values within a radiographic range
look up table conversion
the lowest readings on a histogram represent
collimated tissue
coincidence testing assess
light field accuracy
actual exposure time must be within_______of the indicated exposure time
5%
the actual kVp must be within ___________ of the assigned kVp
5%
the light field must correspond to the actual exposure field with the tolerance of
2%
mGy/mAs measurement between adjacent mA stations should not vary by more than `
10%
x-ray systems must demonstrate consistent exposure reproducibility within a tolerance of
2%
the CR indicator must align to the actual center of the x-ray field within the tolerance of
1%
SID range should be
2%
exposure linearity error range
10%
positioning parameters for lateral skull
anterior oblique
CR: 2 inches above EAM
IPL perpendicular to the edge of the IR
what makes a diagnostic lateral skull x-ray
superimposition of the orbital roofs and greater sphenoid wings
sella turcica in profile
what makes a diagnostic PA skull
symmetric petrous ridges
orbits filled by petrous ridges
postponing parameters for AP Townes skull
30 degrees caudal
2.5 inches above glabella
OML is perpendicular
positioning for AP Townes skull if pt can’t bend chin
bend chin put 37 tube angle and use IOML
diagnostic PA caldwell skull
petrous pyramids sitting at the lower 1/3 portion of the orbit
positioning parameters for SMV skull
IOML is parallel to the IR
CR: 0.75 inches anterior to EAM
for SMV skull the CR should enter where?
sella turcica
positioning parameters for lateral facial bones
Anterior oblique
IPL perpendicular to IR
mid sagittal plane is plane to IR
CR: between the EAM and outer canthus
diagnostic lateral facial bones
superimposed mandibular rami and oribital roofs
sella turcica in profile
for waters (pariteocanthial) facial bones how much of angle does the OML make?
37 degrees
diagnostic lateral facial bones
petrous ridges below maxillary sinus
for facial bones waters the OML forms what angle to the IR
55 degrees
is the only one that has this
positioning for lateral nasal bones
anterior oblique
IPL is perpendicular
IOML perpendicular to front edge of IR
CR: 0.5 inch inferior to nasion
CR for lateral sinus
midway between outer canthus and EAM
what 2 sinuses are shown on an SMV
sphenoid and ethmoid
what 2 sinuses are shown on a waters
sphenoid and maxillary
millamperage formula
mA x s= mAs
Ma in the x-ray tube is the unit of measure describing
tube current
exposure time
electrons are flowing through the tube
in order to decrease motion blur on an image what should you do?
decrease mA and increase exposure time
SID is defined as the distance from the
anode focal spot to the IR
mA in the x-ray tube is the measurement of
tube current
AEC
provides x-rays with consistent receptor exposure
automatically adjusts exposure time
reduces the chance of over exposing pts
what do ionization chambers do?
measure receptor exposure
true or false AEC controls the mAs
true
when using AEC what does the tech need to adjust
SID
kVp
mA
to change the receptor exposure for the chambers what do you need to do?
adjust the density setting
if there is motion in the radiograph how do you fix it?
increase mA and lower exposure time
when using a grid what technical factor needs to be increased?
mAs in order to maintain appropriate receptor exposure
grid conversion formula
mAs2= mAs1 x GCF2/GCF1
GCF2 is the new grid conversion factor
GCF1 is the old grid conversion factor
when should grids be used?
when the atomic body part exceeds 10cm in thickness
grid ratio
Height of lead strips (h) divided by distance (D). h/D
Increase in grid ratio
Increase in image contrast
Increase in needed mAs value
Increase in patient dose
Material used for strips in grid
Lead (most common)
Tungsten
Platnium
using the incorrect SID with a focused grid results in
grid cut off because focused grids are designed to be used with specific SID
if you angle the tube which type of grid can not be used
crossed because the body part must be perfectly positioned
off level grid error
grid is not perpendicular to CR
lead strips are not in line with path of useful beam
off level grid errors affect:
focused and non focused grids
off center grid error
only affects focused grids
grid is not placed directly under the CR
off focus grid error
SID does not match the design of the focused grid
only affects focused grids
off angulation grid error
x-ray beam is angled against the direction of the grid lines
affects focused and non focused grids
upside down grid error
focused grid is placed upside down
only affects focused grids
inverse square law defines the relationship between
distance and beam intensity
off center grid errors result in
decreased receptor exposure across the entire radiograph
autonomy
Patients have the right to make decisions about their healthcare
tort
A civil wrong that can result in legal liability
who is required to wear a personal dosimeter
anyone who is exposed to a dose exceeding an occupational dose of 5 mSv
positive beam limitation
Automatically adjusts the collimation to match the detector size
what material is used within collimator blades
lead
what is the most common material used for filters
aluminum
why is alluminum used for filtration
Relatively low automatic number
Absorbs low-energy electrons
Allows transmission of most high-energy photons
electronic intensificaiton
electrons are moved at a highspeed from photocathode to the output phosphor
the transformer core is made out of
iron due to its ferromagnetic properties
decrease in anode angles result in
lowest x-ray beam intensity
better spatial resolution
what area of the x-ray tube is struct by electrons during x-ray exposure
actual focal spot
in DR thin film transistors do what?
collect electrical charge
poor IR exposure in a digital image results in
loss of information in the image
what is saturation of an image?
loss of information of an image due to overexposure
image has no shades of grey (black)
what does quantum mottle look like on an image
image has a grainy texture
underexposure
exposure latitude
range of exposures that produces quality images at an appropriate patient dose
purpose of ADC in CR
convert electrical signals into binary signals
what increases the severity of the anode heel effect
decrease SID
when the anode heel degree is lessened
increase field size
large detector element pitch results in
low spatial resolution
what is pitch
the distance between detector elements
veil glare
fall off in brightness at the periphery of an image intensifier image
vignetting
fall off in brightness at the periphery of an image
components of a transformer
core
primary coil
secondary coil
purpose of a rectifier
alternating current to direct current
which of the following will determine the average pixel value
region of interest
what is histogram anaylsis
the process used to identify the usual exposure values in the digital image
what do changes in SID affect?
size
electronic masking
elimination of extraneous light from the edges of a digital radiographic image
what changes are used to improve spatial resolution of an image
decreased focal spot size
decreased OID
increased SID
what is a focal spot?
is the area of the anode surface which receives the beam of electrons from the cathode. It is the apparent source of x-rays.
which two radiation interactions with matter will not result in ionization?
coherent scattering
transmission
what conditions are considered somatic effects of radiation?
cataracts
cancer
fetal effects
the majority of x-ray photons in an x-ray beam are produced by
bremsstrahlung radiation
the primary barriers in an x-ray room must have the thickness of
1/16 or 1.6mm lead
who is required to wear a dosimeter
anyone who may be exposed to an annual occupational dose of 5 mSv
a 0.25mm lead apron will attenuate what percentage of the beam at 75 kVp?
66%
a 0.25mm lead apron will attenuate what percentage of the beam at 50 kVp?
97%
a 0.25mm lead apron will attenuate what percentage of the beam at 100 kVp?
51%
a 0.5mm lead apron will attenuate what percentage of the beam at 75 kVp?
88%
a 0.5mm lead apron will attenuate what percentage of the beam at 50 kVp?
99%
a 0.5mm lead apron will attenuate what percentage of the beam at 100 kVp?
75%
exposure maintenance formula
mAs2= mAs1 x (D2)^2/(D1)^2
if SID is doubled intensity is ___________
decreased four times
if distance is halved intensity _________________
increases 4 times
if mAs are double mAs must _______________
increase 4 times
if mAs is halved mAs must______________
decrease by a factor of 4 times
what controls contrast resolution
bit depth
number of bits per pixel
subject contrast
the remnant beam after interacting with the patient
Nyquist frequency
highest spatial resolution that can be recorded, controlled by pixel pitch
rheostat
regulates thermionic emission
what is the thin film transistor made out of
cesium iodide
what is the purpose of the scintillation layer in indirect conversion
converts x-ray photons to light
what is the purpose of the photodiode in indirect conversion?
converts light into electrical charge
composed of amorphous silicon
what is the purpose of the TFT layer in indirect conversion
comprised of small detector elements that capture the electrical charge and convert it into an image
for direct conversion what material is used?
amorphous selenium
QC test: filtration
annually
tolerance: 2.5mm AL
QC test: collimation
semi-annually
tolerance: 2% of SID
QC test: focal spot
annually
tolerance: 50%
QC test: kVp
annually
tolerance: 10%
QC test: timer
annually
tolerance: 5% (10ms)
QC test: exposure linearity
annually
tolerance: 10%
QC test: exposure reproducibility
annually
tolerance: 5%
QC test: focal spot equipment
slit camera
star test
pinhole
QC test: exposure linearity equipment
step wedge
dosimeter
sampling frequency (CR)
performed by laser
number of times data is recorded on a digital plate when being read
fast sampling frequency—-small pixel pitch—-increased spatial resolution
duodenal bulb hypersthenic
T11 or T12
duodenal bulb shtenic
L1 or L2
Aesthenic or hypersthenic
L3 or L4
secondary barrier lead
1/32mm Lead
personal dosimetry tracks radiation dose to occupational workers
exceed 10% of annual limit must wear dosimeter
Sthenic pt duodenal bulb location
T2-L1
Sthenic pt stomach location
T11-L2
Hypersthenic stomach location
T9-T12
Hypersthenic duodenal bulb location
T11-T12
Hyposthenic and aesthetic duodenal bulb location
T11-L5
Hyposthenic and aesthetic stomach bulb location
L3-L4
