Test 1 Flashcards
what is an example of molecular effects of irradiation
any visible signs of molecular/cellular damage
ex. radiation burns
results from molecular damage
formation of structurally changed molecules that may impair cell functions
classifications of cell effect from radiation
direct
indirect
where does energy transfer for direct action
direct energy transfer to macromolecules
effect of direct action?
ionizing particles directly effect macromolecules –> making them inactive or alters function
likeliness of direct action occurring? occurs most often with what?
very low –> 1%
more likely with high-LET, particulate radiation, or alpha radiation
why is direct action less likely to occur?
atom is mainly space = less occurrence to interact
what damage does direct action cause?
double strand break or single strand break = cell death
why is indirect action most likely to occur?
interacts with water (most abundant molecule)
what is radiolysis of water
indirect action radiation that breaks apart water and creates free radicals
what causes damage in indirect action
free radicals transferring energy to macromolecules
what type of radiation is indirect and direct
indirect = secondary
direct = primary
all effects of irradiation in living cells come from?
indirect action
what is a macromolecule?
building material in DNA
what is a free radical
atom/molecule that has a single, unpaired orbital (valence) electron
characteristic of free radical (3)
highly reactive
possible result of cell death
short lifespan
free radicals can cause damage by
ionization
excitation
creation of toxic substances (peroxide/superoxide)
cellular effects of irradiation is characterized by?
amount of radiation given
type of radiation
types of affects from ionizing radiation (7)
Instant death
reproductive death
apoptosis
mitotic death
mitotic delay
permanent or temporary interference with function
chromosome breakage
energy transfer in ionizing radiation
energy transfer to cell’s nucleus
instant death
amount
effect
amount: 1000+ Gy/sec
effect: disrupts cellular form, structure, chemistry
reproductive death
amount
amount: 1-10 Gy
apoptosis
effect
cells die without dividing –> programmed cell death
can occur with or without exposure to radiation
mitotic death
effect
cells die after 1-2 divisions
mitotic delay
amount
effect
amount: 0.01Gy
effect: failure for cell to divide in time
chromosome breakage
effect
ionizing radiation interacts with DNA = loss of genetic material = mutations
point mutation
occurs with?
can be repaired?
occurs with low-LET
Yes by action of repair enzymes
double strand breaks
occurs with?
can be repaired?
occurs with high-LET
Less likely to be repaired
Target theory
when cell DNA is directly or indirectly inactivated by exposure to radiation = cell death
when was the British X-ray and Radium Protection Committee created?
1921
British X-ray and Radium Protection Committee
Purpose?
Flaw?
Purpose: creates guidelines for manufacturers and use of radium/x-ray equipment
Flaw: no accurate measuring techniques or background knowledge
Skin erythema dose
purpose?
flaw?
Purpose: measured radiation exposure by physical appearance of redness over an area of skin
Flaw: inaccurate measurement –> erythema reaction varied from person to person
when was SED used?
1900-1930
tolerance dose AKA
threshold dose
tolerance dose was measured in? when?
Roentgen
when: 1930s
what does tolerance dose measure?
exposure/radiation in air
tolerance dose is established by? for?
British X-ray and Radium Protection Committee
For: radiation control
tolerance dose in 1934?
tolerance dose in 1936?
0.2 R/day
0.1 R/day
maximum permissible dose is measured in?
REM –> radiation equivalent man
Radiation theory in 1930 vs 1950
1930: no adverse effects if doses lower than tolerance dose level
1950: no amount of radiation given is completely safe
when was tolerance dose replaced? replaced with what?
when: 1950
replacement: maximum permissible dose
what determines REM?
1970 dosimetry and risk analysis determined different types of radiation interacted differently with varying organ systems
when was REM replaced? replacement?
1980
Sievert (Sv) for REM
Why is SI units used?
takes consideration of tissue sensitivity caused by equal absorbed doses of different types of ionizing radiation
types of radiation dose-response relationships
threshold
non-threshold
what does radiation dose-response relationships represent?
risk of occurrence of malignancies in population that has been exposed to low levels of ionizing radiation
dose-response curves
as dose increases so do most effects
threshold relationship
below a certain radiation level or dose = no biologic effects observed
non-threshold relationship
any radiation dose has the capability of producing a biologic effect = no radiation is considered safe
who regulates radiation protection? importance?
federal
Important: improve radiographic quality and reduces patient dose
what is the purpose of the control panel
indicates the conditions of exposure and when the tube is energized (visual and audible)
what indicators are on the control panel
kVp and mA indicators
what are the radiographic protection features
Protective tube housing
control panel
source to image receptor distance indicator
collimation
operator shield
types of radiation monitoring
personnel
area monitoring
do we only use SI units for radiation monitoring
NO
traditional and SI unit
purpose for radiation monitoring
ensures occupational radiation exposure levels kept below annual effective dose limit
what is the annual limit radiation dose
50mSv or 5 rem
personal dosimetry
monitors radiation exposure of any person occupationally exposed regularly to ionizing radiation
importance of personnel monitoring
indicates worker habits
determines occupational exposure over time
types of personal dosimeters
optically stimulated luminescence dosimeters (OSL)
film badge
thermoluminescent dosimeters (TLDs)
pocket ionization chambers
what contains aluminum oxide film
OSL
how does the filter work in OSL
attenuation of different degrees depending on the energy of the photon
Pros of OSL
light, easy to carry, not effected by heat/moisture/pressure
film badge composition
film holder
filter
film packet
how does filter work in film badges
measures energy of radiation –> determines if exposure was from scatter or primary beam
pros of film badge
cheap/effective to monitor large numbers of personnel
film = legal doc of radiation exposure
can differentiate types of radiation
what records whole body exposure accumulated at low dose for long periods of time
film badge
con of film badge
very sensitive = heat and moisture can cause fogging
how does TLDs monitor radiation
lithium fluoride crystal
what type of dosimeter best stimulates human tissue
TLDs –> crystals
pros of TLDs
accurate dose measurement
not effected by humidity, pressure, normal temp
cons of TLDs
expensive
single use
how does a pocket ionization chamber function?
has ionization chamber measuring radiation exposure
pro of pocket ionization chamber
immediate exposure readout (in high exposure areas)
compact/convenient
con of pocket ionization chamber
MOST expensive
inaccurate if not read everyday
what is the equivalent dose limit for pregnant women
0.5mSv/month
why is lowering equicalent dose limit important for pregnant women?
lower total lifetime risk of leukemia/other malignancies
how do survey instruments work?
interacts with radiation and ionizes gas (air) in the detector
types of surveying instruments
ionization chamber type survey meter (cutie pie)
proportional counter
geiger-muller detector
criteria for surveying instruments
portable
sturdy
interact with radiation similar to human tissue
detect all kinds of radiation
affordable
when did radiation damage become apparent
early 1896
who were the first to experiment with radiation by self-expose
Friedrich Walkoff
Friedrich Giesel
how did the 2 Friedrichs’ conduct their experiment?
conclusion?
strapped radium salt to their forearm for 2 hours
Conclusion: radiodermitis
who discovered how to protect against radiation
Henri Becquerel
who discovered that radiation effects can leave animals sterile?
how?
when?
Albers-Schonberg
xray testes of rabbits and guinea pigs
1903
who discovered that radiation effects can have abnormal egg development?
how?
when?
Charles Bardeen
xrays frog larvae spermatozoa = eggs abnormal
1907
when did experimentation occur on bacteria
1897 and 1902
when did experimentation occur on seeds
1901
what does the law of bergonie and tribondeau state?
radiosensitivity of cells is directly proportional to reproductive activity and inversely proportional to degree of differentiation
what did J. Bergonie and L. Tribondeau experiment on? When?
radiation effects on testicular germ cells of rabbits
1906
according to the law of bergonie and tribondeau would a stem cell be directly or indirectly proportional?
directly proportional to radiosensitivity
Who discovered xray mutations?
how?
when?
Hermann Muller
experimented on fruit flies –> radiation induced mutations and mutations are hereditary
1926
how did others replicate Muller’s results? when?
experimented on corn and wasps
1928
when did Muller receive his nobel prize
1946
who proposed linear non-threshold model?
Muller
what did the international commission on radiological protection declare in 1954?
irradiation to gonads should be protected as much as possible by collimation or protective screens
what did the international commission on radiological protection declare in 1956?
genetic damage assumes greater importance and recommended a max permitted genetic dose
what did the international commission on radiological protection declare in 1982?
use gonad shielding while doing gonad procedure
-had 0 point –> had longer exposure time
what did US code of federal regulations state? when?
shielding is used to reduce potential hereditary risk
radiation exposure is too low to affect fertility
1976
how is radiation safer today than 1895?
tube design and tube housing
xray protection for workers
digital IR and processing
how did xray protection for workers change since 1895
shielding for operators and pregnant women
exposure time
distance
how did tube design and tube housing change since 1895
filter
collimation
increased SID
what doses has small or nonexistent affect on an embryo or fetus?
less than 100mGy
is linear no-thereshold model supported? why?
NO
human body can repair faster than that of a fly
has there been proven hereditary effects from radiation
Not in diagnostic radiation
Difference between old and new xray equipment
OLD: large doses at longer exposure times
NEW: better image quality for lower doses at shorter exposure times
Who studied the differences between old and new xray equipment
Gerrit Kemerink
AAPM announcement in 2019? why this decision?
no more gonad shield for gonad procedures
WHY? difficult to position –> leads to repeats = more radiation
Problems with gonadal shielding
AEC affected
histogram, LUT, rescaling errors
increase patient radiation dose
somatic or non-somatic?
irradiation of genetic material (sperm or egg) is _____?
non-somatic
stochastic effects
probability that effect happens depends on received dose not the severity of the effect
deterministic effects
both probability and severity are dependent on dose
what effect is acute radiation syndrome
deterministic somatic effect
somatic effect
living organism that has been exposed to radiation sustaining biologic damage
acute radiation syndrome (ARS) is also known as
radiation sickness
when does acute radiation syndrome (ARS) occur
(humans) after whole body receives large doses of ionizing radiation given over a short period of time
example of acute radiation syndrome occurrence
Hiroshima bombing
Chernobyl
radiation therapy patients (measured sub-lethal doses)
type of radiation in acute radiation syndrome (ARS)
particulate radiation
4 stages to acute radiation syndrome (ARS)
prodromal (initial)
latent
manifest illness
recovery or death
3 types of possible syndromes to acute radiation syndromes (ARS)
hematopoietic syndrome
gastrointestinal syndrome
cerebrovascular syndrome
in radiation therapy how many doses can patient receive with ARS
2-3
hematopoietic syndrome is also known as
bone marrow syndrome
when does hematopoietic syndrome occur
whole body exposed
threshold dose from 1-10
what happens with hematopoietic syndrome
RBC, WBC, and platelets decrease = decrease in bone marrow stem cells, lower immune response, lower blood clotting
risk factor of hematopoietic syndrome
prone to infection and hemorrhage
possible organ failures
bone marrow destruction = death
< 2yr/o death in 6-8 weeks ; >2yr/o die faster
is hematopoietic syndrome survival possible?
Yes
is exposure not lethal (1-2 doses) bone marrow cells repopulate within 3 weeks to 6 months after irradiation
how to enhance survival rate for hematopoietic syndrome
intense supportive care
hematologic procedures –> 5+ bone marrow transplants
when does gastrointestinal syndrome occur
threshold dose 6-10
symptoms of gastrointestinal syndrome
severe nausea
vomiting
diarrhea up to 24hrs
gastrointestinal syndrome
what occurs during latent period
symptoms disappear up to 5 days
gastrointestinal syndrome
what occurs during manifest illness stage
severe nausea
vomiting
diarrhea
signs of high dose rad –> fatigue, fever, anemia etc
can death occur with gastrointestinal syndrome? if so why?
yes due to damage to cells in gastrointestinal tract (SI) = infection, fluid loss, or electrolyte imbalance
can someone survive gastrointestinal syndrome?
NO - dies in 3-10 days without support
with support can live a few days longer
is gastrointestinal syndrome survival time dependent on dose
no
higher risk of death
hematopoietic syndrome or gastrointestinal syndrome
hematopoietic syndrome –> lower threshold = will die before death by GI syndrome
how does cerebrovascular syndrome occur
CNS and cardiovascular system received doses of 20-50
is cerebrovascular syndrome survivable?
no death within hrs to 2 or 3 days after exposure
cerebrovascular syndrome
symptoms of prodromal stage
excessive nervousness
confusion
severe nausea
vomiting
Diarrhea
loss of vision
burning sensation
loss of consciousness
cerebrovascular syndrome
symptoms of latent period
12hrs symptoms lessen or disappear
cerebrovascular syndrome
symptoms of prodromal SEVERE
disorientation
ataxia
cranial swelling
fatigue
seizures
Electrolyte imbalance
meningitis
coma
what occurs when the body receives a high radiation dose?
destructive response = cell death, enzyme repair, and recovery
what determines the organ’s potential for recovery
amount of functional damage
given repeated exposures what % is irreparable?
10%
why do we see late somatic effects
repeated exposures = irreparable damage
why is late effects so dangerous?
cellular damage = somatic + hereditary damage
can appear months or years afterwards
example of late biological damage
cataracts
leukemia
genetic mutations
what does epidemiology study (3)
incidence, distribution, control of disease in population
ex. who what when why
how is the rate of irradiation related malignancies determined
compares natural incidence of cancer occurring in population
example of radiation can cause cancer
Japan bombing = high doses = cancer
helps est. risk for occupational workers
what do radiobiologist do?
predict risk of malignancies occurring inn low level exposures
dose response curves =
increase dose = increase effects
Recommended by BEIR what curve do we use to predict cancer risk
linear non-threshold curve
what does the linear non-threshold curve mean?
biologic response to ionizing radiation is directly proportional to given dose
if absorbed dose is doubled = biologic response ______
doubled
what does linear-quadratic nonthreshold curve represent
estimates risk associated with low level radiation
which curve better represents stochastic and genetic effect?
linear-quadratic nonthreshold curve
which diseases follow linear-quadratic nonthreshold curve
leukemia
breast cancer
heritable damage
what type of effect appears months or years after exposure?
late somatic effect
ways to get late somatic effect (3)
previous whole or partial body acute exposure (bombing)
previous high radiation doses (therapy)
long term low level doses given over several years (workers)
______ does not increase risk of malignancy
below 0.1 Sv
types of late effects (2)
stochastic
deterministic
example of stochastic?
carcinogenesis
embryologic effect (birth defect)
example of deterministic
cataractogenesis
can cancer always be predicted?
no it is random occurrence –> no threshold and no dose to severity relation
what are prime factors
mAs
kVp
distance
other factors to control x-ray emission
collimation
filter
generators
size of patient body
digital image capture is _____
linear
pros of digital image capture
captures nearly all xray photons
uses computer software
what does computer software do in digital image capture
subtract density values based on diagnostic values of particular body part
window leveling controls? what movement?
brightness/darkness screen image
up and down movement
window width controls? what movement?
ratio of black and white –> contrast
left and right movement
what is a technique chart
range of techniques set for exam and body part size
why do we use technique chart
make best quality image at lowest patient dose possible
when does a variable change in an exposure system
based on thickness of anatomical part
pros to fixed kVp systems (6)
decreased patient dose
more image info
increased consistency of IR exposure
lengthens exposure latitude
reduced xray tube wear
decreased time settings/patient motion
cons of fixed kVp system (2)
more scatter
lower contrast
pros to variable kVp system (5)
allows small changes in kVp adjustments for body part thickness
finer adjustment settings than mAs
higher contrast images
enhanced visibility of fine detail
increased resolution
how to establish an exposure system
- collect exposure data
- make single exposure of optimal diagnostic quality on phantom
- use variety of technical factor combos both above and below average level keeping mAs the same
- measure exposure and density with densitometer
- record all clinical fine-tuning in each exposure
how to establish fixed kVp system
- similar to exposure system establishment
- keep kVp constant while manipulating mAs to get appropriate image
- develop optimal kVp
how to achieve best functioning technique factors
constant large number of variables with single varying factor
how to know when fixed kVp is achieved
uniform constrast
easy series of kilovoltages that mAs values can be added to
max kVp = ______
decreased mAs
why would we use max kVp (4)
give acceptable density/IR exposure
sufficient penetration = acceptable image contrast
lower contrast
minimizes patient exposure
how to establish optimal kVp
determine highest kVp and lowest contrast within acceptable limits
does not have to be the best image just highest of acceptable
kVp is dependent on _____?
body part thickness
thicker the body part = ______
higher kVp
mAs is dependent on _____? (2)
body part thickness
IR exposure
3 criteria of kVp
all contrast is acceptable
small part size = kVp gives adequate penetration
large part size = kVp avoids excessive scatter fog
what does an anatomically programmed radiography system do?
controls exposure factors based on specific anatomical procedures using AEC and exposure control units
what happens if there is no preset available for anatomically programmed radiography systems
tech determines ma, kVp, and distance
what is ionization chamber used for
measures exposure to receptor
cons to ionization chambers
precise positioning over chamber = possible repeats
pros to ionization chambers
tech does not need to set exposure time (mAs)
where is the ionization chamber located
AEC
is mA and kVp fixed in AEC
no can be manually set
how many chambers are in an AEC
3 ionization chambers
how do ionization chambers work?
- select combo of chambers –> control exposure
- Appropriate voltage reached, exposure terminates by operational amplifier
things not to do using an ionization chamber
don’t collimate too closely = overexposure
don’t collimate too wide = underexposure
how is a back up timer established
uses max exposure time to prevent overexposure
based on 150% of anticipated manual exposure time
con to back up time
if too short = image underexposed
what is speed class
the speed of any imaging system expresses sensitivity to radiation exposure
how do we calculate speed class
inherent speed of IR + digital processing speed
why is speed class important
for image acquisition state
given the speed class of 100 what is the average exposure?
10uGy
what speed class do we typically use? why?
200 speed class
WHY: reduces chance of quantum mottle
high exposure indicator = ______ exposure
over
low exposure indicator = _______ exposure
under
what is target EI
ideal amount of IR exposure for specific speed class
what does exposure indicator represent
Numerical value (preset from manufacturer) that presents IR exposure
what needs to be included on DICOM header for every image?
deviation index read out
errors in histogram analysis can lead to…..?
corrupted EI and DI readouts
pro of using DI
can be used by all manufacturers regardless of their specific methods for EI
given DI of > +3.0
Exposure?
Repeat?
Overexposed –> 100% too high
no repeat unless saturation occurs
given DI of +1 to +3
Exposure?
Repeat?
Overexposed –> 25% - 100% too high
no repeat unless saturation occurs
given DI of -0.5 to +0.5
Exposure?
Repeat?
-20% - +25%
no Target range
given DI of -1 to -3
Exposure?
Repeat?
underexposed –> 20% - 50% too low
Repeat only if radiologist requests
given DI of < -3.0
Exposure?
Repeat?
underexposed –> 50% too low
Repeat –> excessive mottle certain
how can overexposed images be fixed?
windowing
what is saturation
electrical phenomenon when dexels in a particular area have reached max electrical charge stored –> makes tissues appear black
saturation represents?
complete loss of data
ways to lower or raise DI (4)
poor collimation
unusual body habitus
prosthetic devices
gonadal shield
Deviation index indicates? number is derived from?
INDICATES: IR dose which estimates patient dose
DERIVED: pixel values in histogram
how is brightness/density controlled
rescaling
how is grayscale/contrast controlled
LUTs (Gradation)
how is sharpness (spatial resolution) controlled?
pixel size
how is magnification controlled?
matrix size or field of view
how is shape distortion controlled?
part alignment
type of monitor to view monitor
liquid crystal display (LCD)
what is a workstation
computer terminals used to adjust image quality and save changes into PACs
for technologist
what does PACs stand for
picture archiving and communication system
what is a diagnostic workstation
reading room with 3 monitors
for radiologist
component to a light ray
double wave –> electrical perpendicular to magnetic component = electromagnetic radiation
how does polarizing lens work
only parallel waves can pass through polarization filter
perpendicular waves are blocked
what happens if 2 polarizing lens are placed perpendicular from each other?
all light is blocked out
layers to LCD monitor screen (5)
polarizing film
flat wires = electricity conduction
nematic liquid crystal material
perpendicular polarizing film
flat wires
requirement for imaging monitors
fast response
fast refresh time
response time
time necessary for the monitor to change brightness
refresh time
time required by entire monitor screen to reconstruct next frame of dynamic moving image or next “slide” in series
what does AMLCD stand for
Active matrix LCD
pros of AMLCD (4)
entire rows of pixels can be read out one at a time instead of single pixel
meets requirements for LCD
refresh rate 240Hz
each pixel has their own TFT
problems with LCD monitors (3)
input lag
dead pixels
dark spots
input lag
too much processing at once
ex. rescaling, noise reduction, edge enhancement
dead pixels
appearance of permanent white spots = no electrical charge running through pixel
dark spots
permanent spots on monitor screen from stuck pixels that are constantly receiving electrical charge
when should a monitor be replaced (3)
15 defective pixels across entire screen
3 defective pixels in one cm circumference
more than 3 defective pixels adjacent to each other anywhere on the screen
pros of LCD monitors (4)
no distortion of image or change in sharpness
no glare and reflection of ambient light
no flicker
uniform brightness consistency
cons of LCD monitors (5)
pixelation
limited contrast = frequent windowing done by radiologist
sensitive to temperature changes = 15 min warm up for full luminance
viewing angle dependence
what is viewing angle dependence
drop off of brightness depending on viewing angle
must be viewed head on
sharpness in recording latent images is determined by?
size of dexels
sharpness in image processing is determined by?
pixel size
if spatial resolution is unchanged = ________
pixel/dexel size is unchanged
what does hardware pixels determine?
monitor’s inherent resolution capabilities
smaller hardware pixels = _______
better sharpness and inherent spatial resolution
soft pixel
actual displayed light image
how to change soft pixel
zooming the field of view in or out
what is dot pitch known as
pixel pitch
what is dot pitch
distance between centers of any two adjacent hardware pixels
pixel size for high resolution
0.1-0.2 mm
smaller pixel pitch = _______ + ________
smaller pixel size
sharper resolution
