Questions Flashcards
high bone marrow examinations
- barium enema
- upper GI series
- abdominal angiography
biological effects of ionizing radiation that are manifested in offspring
genetic effects
cell line used as an indicator of somatic effects of radiation
bone marrow
photocathode gives off what in proportion to the intensity of fluorescent light?
electrons
in an x-ray system with ABC and an x-ray tube BELOW the table, moving the image intensifier AWAY from the patient will do what to the patient’s radiation exposure?
increase
cell type most sensitive to radiation
lymphocytes
strong correlation between the mean radiation dose received by bone marrow and what?
leukemia
what is half-value layer (HVL)?
thickness of absorbing material necessary to reduce x-ray intensity to 1/2 its original value
collision between an x-ray photon and INNER orbital electron, knocking the electron out of its orbit
photoelectric effect
what organ is NOT used for somatic dose measurements
thyroid
what are required to be posted in x-ray areas?
- form RH-2364 “Notice to Employees”
- copy of operating procedures
tighter collimation to reduce the FOV will cause image brightness to
reduce
minimum lead equivalent thickness for protective aprons
0.5 mm
probability of an effect occurring
stochastic effect
severity of an effect that has occurred
nonstochastic effect, aka, deterministic effect
in digital imaging, adjusting the window level changes
contrast
photoconductive target function
allows an electron charge to be generated
can operator exposure occur after the dead-man switch is released?
NO
hypothesis states that any radiation dose has some degree of effect
non-threshold
type of sterility resulting from a 50 rad exposure to gonads
temporary
reason filters are used in film badges
measure doses over a wide range of energies
type of image receptor converts x-rays into an electrical charge using an array (matrix) of detector elements
flat panel detector
bucky slot cover lead equivalent thickness
0.25 mm
dose equivalent limit to an embryo/fetus during the ENTIRE pregnancy for an occupational exposure of a pregnant woman
5 mSv
image characteristics greatest at the center of the image intensifier
- resolution
- detail
- brightness
an operator should use a thyroid shield when
performing fluoroscopy and standing close to the patient
type of image receptor uses either direct or indirect methods to convert x-rays into an electrical charge
flat panel detector
conversion factor formula
intensity of output phosphor ÷ mrads/s
term refers to the standardized method of evaluating the brightness of an image intensifier
conversion factor
closed-circuit systems transmit signals through
cables
component of a fluoroscopic system that speeds up electrons
accelerating anode
when the fluoroscopy time limit has been reached, the manual-reset timer must do the following
- produce an audible signal
- interrupt the x-ray beam
minification gain x flux gain =
total brightness gain
occurs when the diameter of the image from the optical system is SMALLER than the shortest dimension of the film
underframing
mild adverse effects from contrast media
- mild nausea/vomiting
- limited urticaria
- limited “itchy” throat
- nasal congestion
- sneezing/runny nose
moderate adverse effects from contrast media
- protracted nausea/vomiting
- diffuse urticaria
- diffuse erythema
- facial edema w/o difficulty breathing
- wheezing w/o hypoxia
severe adverse effects from contrast media
- facial edema w/ difficulty breathing
- diffuse erythema w/ hypotension
- laryngeal edema or wheezing w/ hypoxia
- anaphylactic shock
minimum required thickness of protective curtains
0.25 mm Pb equivalent
when should the State be notified If an occupational worker receives an exposure of 0.02 Sv for 3 consecutive calendar quarters?
w/i 30 days
immediate notification to the Radiologic Health Branch is required if an individual has received
- total effective dose equivalent ≥ 25 rems (0.25 Sv)
- eye dose equivalent ≥ 75 rems (0.75 Sv)
- shallow-dose equivalent to the skin or extremities ≥ 250 rads (2.5 Sv)
24-hour notification to the Radiologic Health Branch is required if an individual has received
- total effective dose equivalent ≥ 5 rems (0.05 Sv)
- eye dose equivalent ≥ 15 rems (0.15 Sv)
- shallow-dose equivalent to the skin or extremities ≥ 50 rads (0.5 Sv)
doubling exposure time does what to the total exposure of the patient
doubles
legal aspects of taking X-rays fall under
- civil law
- regulatory law
- administrative law
how many days after the onset of menses is it safest to perform x-rays?
10-14 days
irradiated animals die from
the same diseases as non-irradiated controls but at a younger age
what are the specified parameters to measure fluoroscopy exposure rates using a phantom?
- maximum 5 rads/min
- 30 cm from the image intensifier
- using a phantom 9 in of water
what must be posted in areas where x-ray machines are being used?
- x-ray supervisor and operator permit
- radiologic technologist certificate
- RHD’s “Notice to Employees” (form RH-2364)
curve used as a basis for regulatory radiation guidelines
curve that intersects the abscissa at the origin
if the x-ray tube is fixed BELOW the table in a system equipped with ABC, what effect will moving the image intensifier AWAY from the patient have?
increase the patient dose
recording system that can reduce patient dose up to 95%
video disc recording
of horizontal lines on a television monitor
525
identify the labeled components
I. = photocathode
II. = input phosphor
what is the process in the image intensifier where electrons are accelerated from the photocathode to the output phosphor?
electron intensification
what is the minification gain in an image intensifier with a 10 in input phosphor and a 1 in output phosphor?
100
point where the dose-effect curve intersects the abscissa
threshold dose
fluoroscopic examinations should
- minimize patient exposure
- minimize operator exposure
- obtain necessary diagnostic information
is a dose to the embryo/fetus considered a genetic dose?
NO
which of the following is directly proportional to the exposure delivered to the patient?
mA
how many rads of acute X-radiation in the diagnostic energy range to the eyes will result in cataracts?
200-300 rads
component that controls the radiation exposure incident at the input phosphor in cine film imaging
aperture
term that refers to the frequency range of a video signal
bandpass
radiation damage exhibited in the offspring of people exposed to radiation
genetic dose
disadvantages of using pocket ionization chambers
- sensitive to mechanical shock
- must be calibrated periodically
- do not provide a permanent record
- information is lost if over-exposed
sends light from the image intensifier to viewing and recording systems
camera control unit
half-value layer (HVL) is a characteristic of an x-rays
quality
thyroid shields are used by operators
when the operator is close to the patient during fluoroscopy
structure does light hit first in the human eye
cornea
factors that lead to radiation exposure to the operator
- radiation leakage from the x-ray housing
- scatter off the patient
- scatter off the collimator
- scatter off the table top
maximum monthly radiation dose to an embryo/fetus
0.5 mSv
mutations from radiation exposure tend to be
deleterious
material that absorbs less penetrating x-rays from the useful beam
filter
minimum total filtration required in fluoroscopic equipment at normal operating voltage
2.5 mm Al equivalent
approximate dose to a fetus from an upper-GI examination of a pregnant patient with a total skin exposure of 5 Roentgens
100 mrads
is NOT a known form of radiation-induced cancer
retinoblastoma
predetermined time limit for a cumulative manual-reset timer
5 minutes
personnel monitoring devices that discharge a capacitor by the ionization of air when in the presence of radiation
- pocket chamber
- pocket ionization chamber
cancers that have been seen in humans exposed to high levels of radiation
- leukemias
- bone malignancies
- skin malignancies
what factors will influence the effect of radiation exposure?
- radiation type
- radiation dose
- cell type
formula to calculate lifetime (cumulative) occupational exposure limit
10 mSv x years
time it it takes to change a fluoroscopic system from a vertical to a horizontal imaging position
2 seconds
what happens if the FOV is held constant and the matrix size decreases?
- pixel size increases
- spatial resolution decreases
bone marrow areas typically exposed when wearing a lead apron
- clavicles
- skull
- arms
sperm precursors
spermatogonia
film size in spot filming cameras has what effect on dose to the patient?
larger film size = greater radiation dose
tabletop intensity of the X-ray beam for a system operating at 80 kVp should not exceed how many rads per minute
2.2 per mA
as matrix size increases
- pixel size decreases
- spatial resolution increases
major source of secondary radiation in radiography is from
patient’s body
people that must be monitored regardless of their likely exposure
- people who operate mobile x-ray equipment
- people who enter a high radiation area
reproductive cells that are irradiated may have changes in their
- genes
- chromosomes
visual acuity of rods (scotopic vision) is what compared to cones (photopic vision)?
worse
used to compare the spatial resolution of imaging systems
modulation transfer factor (MTF)
with optical coupling between an image intensifier, and viewing and recording systems, how much light is sent to the recording system (cine camera)?
90%
does NOT affect patient exposure
room lighting
of horizontal scan lines on a television monitor
525
reason film badges are used
- provide a record of exposure
- measure operator exposure
accounts for the majority of the population’s exposure to man-made radiation
medical use
acute dose of radiation that forms cataracts
200 rads
effects from radiation exposure that occur long after exposure are referred to as
- delayed effects
- long-term effects
- late effects
Sievert is a measure of
absorbed dose equivalent
animal experiments have shown that deleterious effects to an embryo can be produced with as little as radiation exposure as
10 rad
resolving power measurement
lp/mm
estimated percentage of the population that are exposed to fluoroscopy yearly
5%
pixels are given values for a certain color or gray level; the number of bits used to encode these pixel values is known as
bit depth
primary purpose of protective drapes
to reduce scatter to the operator
digital fluoroscopy systems are commonly used to record images of
vessels
occurs when the diameter of the image from the optical system is LARGER than the shortest dimension of the film, resulting in part of the image being lost
overframing
total number of cycles per second available for display by the television camera
bandwidth (bandpass)
skin dose is a good indicator of
dose to nearby organs
the following are required to be posted in x-ray areas
- supervisors and operators permits
- technologists fluoroscopy permits
- radiographers certificates
what happens to a patient’s entrance skin exposure (ESE) when the FOV is decreased on the image intensifier?
increases
least radiosensitive cell type
muscle
can be directly linked to long-term radiation exposure
cataracts
primary radiation is considered
useful x-ray beam
output phosphor converts electrons into
light
ratio between the vertical resolution and the number of scan lines
Kell factor
in California, how frequently must tube potential (kVp) and current (mA) must be monitored?
weekly
what is an eye dose equivalent, and what is the annual limit?
- radiation exposure to the lens of the eye
- 0.15 Sv
the output phosphor converts photoelectrons into
light photons
how many mA would be used during spot filming
100 mA
thickness (in lead equivalent) of protective curtains
0.25 mm
grainy appearance in an image caused by statistical fluctuation of absorbed X-ray photons
quantum mottle
has all its signals carried through cables
closed circuit TV system
absorbed dose (rads) can result in spontaneous abortion of a fetus
50 rads
medical use accounts for what percentage of the average population’s exposure from man-made radiation?
90%
when electrons are accelerated from the photocathode to the output phosphor
electron intensification
a higher frame rate sequence leads to
- higher patient dose
- improved motion aspect as seen by the operator
major source of secondary radiation in radiography
patient’s body
what are personnel monitoring devices
- pocket ion chamber
- thermoluminescent dosimeter (TLD)
- film badge
increasing the kilovolt peak (kVp) and decreasing the milliamperage (mA) will have what effect on skin exposure?
decrease
in cinefluorography, term for camera shutter opening at the same frequency as x-ray pulses
synchronization
can humans detect ionizing radiation as it passes through their body?
NO
fluoroscopy technologists can do what?
- report a diagnosis to a patient if ordered by a licentiate of the healing arts
- position patients correctly during fluoroscopy
- check that images are of high enough quality
purpose of an electron gun
to produce a scanning electron beam
factors directly proportional to milliamperage (mA)
- X-ray output
- radiation dose to patient
clinical benefits of PACS
- simultaneous viewing of images
- faster turnaround of diagnosis
- digital images
what is NOT a clinical benefit of PACS?
hard copy backups
maximum kilovoltage peak (kVp) typically used during fluoroscopy
150 kVp
x-ray operator is required to wear personnel monitoring equipment when?
only when working
resolution of modern cesium iodide image intensifier tubes
4 lp/mm
main disadvantage of thermoluminescent dosimeters (TLD)
exposures can only be read once
should be checked to confirm a patient’s identity prior to conducting a radiographic exam
- name
- DOB
film badge readings are recorded using this unit of measurement
Sievert
standardized method of evaluating the brightness of an image intensifier
conversion factor
approximate exposure a patient would receive during 5 minutes of fluoroscopy
10-30 rads
why is a single anatomic dose reading NOT representative of the total somatic effect from radiological examinations?
- protective shielding
- x-ray beam may restricted to one area
- radiation doses are not uniformly distributed
term referring to the ability of the human eye to perceive fine detail
visual acuity
for fluoroscopic systems with x-ray tubes located UNDER the table, the most scattered radiation is directed
towards the floor
may cause an image artifact during a radiographic procedure
- buttons on gowns
- catheters
an estimated 95% dose reduction can be achieved when using this during fluoroscopy
video disc recording
ability to differentiate small objects as separate images (line pairs per millimeter) is
resolution
if the Bucky tray is moved to the end of the examination table, leaving an opening at the gonadal level, this must be automatically covered with at least
0.25 mm lead equivalent
fall-off in brightness at the periphery of an image
vignetting
must happen to the exposure in a fluoroscopic system if the useful beam is no longer aimed at the image intensifier
must be automatically turned off
Bucky tray location during fluoroscopy
foot of exam table
television monitor consists of
- cathode ray tube
- contrast control function
- brightness control function
- picture tube
grainy or blotchy appearance of a fluoroscopic image is a result of
- statistical fluctuations
- quantum mottle
- low number of absorbed photons
the use of fluorescence for the observation of a dynamic image
fluoroscopy
best spatial resolution
biggest matrix size
in California, how long do an individual’s radiation monitoring records need to be preserved by the employer?
indefintely
exposure to an operator who is wearing a lead apron and facing the patient occurs primarily to the following body parts
- skull
- clavicles
- arms
allows the measurement of radiation doses over a wide range of energies in a film badge
filter
somatic changes caused by radiation
- decreased fertility
- cancer
- injuries to a fetus
most radiosensitive cell type
leukocyte (white blood cell)
line pair grid measures this image characteristic
resolution
an image that is not created by the intersection of light rays and is used for computational purposes
virtual image
factors that will influence the effect of radiation exposure
- radiation type
- radiation dose
- cell type
loss of image brightness at the periphery of an image is a result of
- lower brightness gain at the periphery
- periphery of image is displayed over a larger area than the center
film badges should be attached
above the apron at collar level
focal spot size of a fluoroscopic x-ray tube is _____ than the focal spot size of a radiographic x-ray tube
often smaller
unit is used to measure the input intensity of an x-ray tube
mA
stochastic effects
- somatic effects
- carcinogenesis
thermoluminescent dosimeters (TLD) are made from
lithium fluoride
personnel radiation monitors used
to check that individuals receive less than the maximum allowed radiation dose
in a fluoroscopic system with ABC and an X-ray tube UNDER the table, moving the image intensifier AWAY from the patient does what?
- increases patient dose
- decreases # of x-rays intercepted by the image intensifier
annual occupational dose equivalent limit for lens of the eye (eye dose equivalent)
0.15 Sv
maximum exposure rate allowed for fluoroscopic equipment manufactured after August 1, 1974, with automatic exposure controls (AEC)
10 rads/min
geneticists in general agree that most genetic mutations are
harmful
what barrier must be in the walls and floors exposed to the primary beam?
primary barrier
factors important for obtaining high quality fluoroscopic images
- centering area of interest
- no motion during imaging
- appropriate patient positioning
best ways to reduce operator exposure
- decreasing exposure time
- increasing operator distance from radiation source
- using lead apron
primary cause of shape distortion
geometric factors
how soon must the State Department of Health be notified if an occupational worker receives an exposure of 0.05 Sv to the skin or extremities?
no notification needed
characteristics of contrast media
- low toxicity
- high atomic number
decreasing exposure
decreases the # of absorbed photons
long-term effects from radiation exposure that are of greater concern from a public health standpoint
- genetic effects
- carcinogenic effects
total filtration must be used in fluoroscopic tubes operating above 70 kVp
2.5mm aluminum equivalent
before doing any radiographic or fluoroscopic procedure what must be done?
- appropriate shielding should be placed on the patient
- lead aprons should be worn by all people
- females should be asked if they are pregnant
whole body (total effective dose equivalent) annual occupational dose equivalent limit
0.05 Sv
occupational exposure limit for the entire gestational period for a pregnant worker
5 mSv (0.005 Sv)
Roentgen is a measure of
exposure
what documentation is necessary in order to expose human beings to X-rays for diagnostic purposes?
- technologist fluoroscopy permit
- supervisor and operator radiology certificate, OR
- supervisor and operator fluoroscopy permit
prior to administering a contrast agent, a radiographer must
- alert a physician if there are any concerns
- review the patient’s medical allergies
- complete a patient assessment
long-term effects of radiation manifested in humans as a
statistical increase in rates of disease
a pediatric fluoroscopy exam with a gonad shield should of at least what lead equivalent to protect the child’s gonads?
0.5 mm
an image that is only for computational purposes where the light rays do not actually intersect
virtual image
a lower f-number means more what is available to form an image?
light
a radiation dose with a threshold, and a severity of effect that varies with dose
nonstochastic effect, aka, deterministic effect
unit is analogous to the rem
Sievert
stochastic effects of radiation
probability of an effect occurring from radiation exposure
keeps the light output of the image intensifier constant
automatic brightness control (ABC)
minimum lead equivalent thickness for a gonadal shield
0.5 mm
Kell factor of a 525 scan line system with a vertical resolution of 367
367/525 = 0.7
- can report a diagnosis to a patient if told to do so by a physician
- position patients correctly during fluoroscopy
technologists
minimum required thickness (lead equivalent) of a primary protective barrier for systems operating above 125 kilovolt peak (kVp)
2 mm
imaging method that can reduce patient exposure by taking short x-rays with low frame rates
pulsed fluoroscopy
whole body dose refers to exposure to
- head
- trunk
- arms above elbows
- legs above knees
component of fluoroscopic system that absorbs electrons and emits light photons
output phosphor
Compton scattering involves the interaction of what components
x-ray photon AND outer orbital electron
during mobile (c-arm) fluoroscopy, decreasing the source to skin distance (SSD) does what to the entrance skin exposure (ESE)?
increases it
damage to the CNS from radiation exposure resulting in changes to learning patterns and development can result from radiation exposure during which stage of pregnancy?
second AND third trimesters
unit of energy used to denote work
erg
as cine film is advanced from frame to frame, the coordination of x-ray production is referred to as
synchronization
automatic brightness control (ABC) mode should be monitored with a designated phantom every
week
personnel monitoring device that allows immediate reading of radiation exposure
pocket ionization chamber
standard image intensifier resolution
4 lp/mm
supervisors should give 3 hours of clinical instruction within 1 year of completion of a technologists didactic instruction in the following categories
- GI
- vascular and angiography
- orthopedic
a cine exam using 35 mm film at 30 frames/second compared to fluoroscopy will have what effect on skin exposure?
greater
coordinating the video signal between the camera and monitor serves to
retrace an exact image
increasing the voltage in an image intensifier tube has what effects?
- compresses the electron beam
- moves the crossover point to further away from the output phosphor
grids are used in x-ray systems to improve image quality, but can increase the radiation dose to patients and staff by how much?
1.5-2x
must be done to the video signal when the electron beam produces a voltage that is sent to the television camera
- amplified
- synchronized
approximate dose that can cause acute skin erythema
200-300 rads (200-300 centrigray)
total filtration that must be used in fluoroscopic tubes operating above 70 kVp
2.5mm aluminum equivalent
according to the Law of Bergonie and Tribondeau, radiosensitivity depends on
- # of undifferentiated cells
- degree of mitotic activity of cells
- life cycle of exposed cells
lead glass shield that is ceiling supported shield
overhanging shield
must be included on fluoroscopic images
- patient’s name
- patient’s DOB
minimum total filtration required in fluoroscopic equipment at normal operating voltage
2.5 mm Al equivalent
estimated reduction in exposure from diagnostic x-rays that can be achieved without compromising patient benefit
50%
cathode-grid assembly aka
electron gun
aprons of at least 0.25 mm lead equivalent must be worn if the operator is likely to receive this dose of radiation
5 mrads/hr
increase in output image brightness of an image intensifier tube due to the size reduction of the output image is
minification gain
mobile screens are available in what lead equivalent thickness
1 or 2 mm
input phosphor function
absorbs x-rays
organization considered to be the world authority on the safe use of ionizing radiation
International Commission on Radiological Protection (ICRP)
image characteristics greatest at the center of the image intensifier
- resolution
- brightness
turns the video signal into an image
TV monitor
occurs when the milliamperage is increased on an x-ray tube
- increased image brightness
- increased operator exposure
- increased patient exposure
damage due to radiation exposure
dose-rate dependent
visibility of mottle in a system is determined by
- resolution
- contrast
- sensitivity
contrast on the television monitor should be set so that
darkest object is just below the black level
radiation dose produces less damage if
- is spread out over a long period of time
- it is protracted over a long period of time
T/F: dose received by an embryo/fetus is a genetic dose
false
0.25 mm lead equivalent apron will reduce radiation exposure at 75 kVp approximately
97%
during fluoroscopy, the room lighting should be what to enhance visualization of black and white television images?
dim
short term effects of radiation exposure refer to what time periods?
- minutes
- days
- weeks
exposure reduction of a 0.25 mm thick lead apron at 50 kVp
99%
is NOT considered an occupational radiation exposure
radiation exposure for a medical diagnosis
actual radiation exposure compared to the amount recorded by a personnel monitoring device
sometimes much higher
“high radiation area” is an area in which individuals could receive a dose equivalent greater than what in one hour?
1 mSv (0.001 Sv)
projecting an image formed on a curved input phosphor to a flat output phosphor leads to
pincushion distortion
compared to normal size mode, what happens to the patient radiation dose with magnification mode?
increases
used to compare the spatial resolution of imaging systems
modulation transfer function (MTF)
components of a closed-circuit television system
- Vidicon camera
- camera control unit
- monitor
body area that has the largest distribution of fluoroscopic examinations
GI tract
maximum tabletop dose rate when imaging with high level (boost) fluoroscopy
20 rads/min (20 centigray/min)
lower image quality at low radiation doses is a result of
quantum mottle
component that converts an electrical signal into a visible image
monitor (TV monitor)
Genetically Significant Dose (GSD) is a function of
- radiograph examination rate
- # of future children
- average gonad dose per exam
ratio of the intensity of the output phosphor to the input exposure rate in mrads/sec
conversion factor
if the FOV is held constant, what will improve spatial resolution?
- increasing the # of pixels
groups of people that showed early evidence of the potential harmful effects of large dose exposure to ionizing radiation
- radiologists
- radium Industry workers
disease seen in early radiologists
leukemia
fluoroscopic system that keeps the light output of the image intensifier constant over variations of patient thickness and density
ABS (automatic brightness stabilization)
inverse square law (intensity of radiation is proportional to the square of the distance from the source)
I1(D1)2 = I2(D2)2
thyroid shield thickness
0.25 mm and 0.5 mm
personnel monitoring device that’s accurate w/i 9% of the actual exposure dose
thermoluminescent dosimeter (TLD)
electrons are focused by the
electrostatic lenses
cornerstone principle of minimizing radiation exposure in medicine
As Low As Reasonably Achievable (ALARA)
area most susceptible to radiation induced cancer
hematopoietic tissue
severity of radiation injury on the cellular level is dependent on
location of the radiation interaction w/i the cell
time required for the eye to recognize an image
visual acuity
maximum mA setting typically used during fluoroscopy
5 mA
approximate radiation exposure from a routine upper gastrointestinal (GI) study
100 mrads
percentage of the active bone marrow of the body does a lead apron cover
70%
image processing tasks used in digital imaging
- edge enhancement
- road mapping
- temporal frame averaging
record keeping is NOT required by the State of California Radiation Control Regulations for
all personnel hired by the radiology department
T/F: humans detect ionizing radiation as it passes through their body
false
altered genetic information that is passed on to cells of the offspring
genetic dose
minimum required total filtration that must be permanently fixed in the useful beam for fluoroscopy
2.5 mm Al equivalent
relative increase in exposure when using magnification mode, where the center 6 inches of the input screen is now visualized over the entire 9 inch window
2.25
increase in patient radiation dose = (normal mode size)2/(magnification mode size)2
mobile C-arm fluoroscopy systems do NOT require
protective curtains
laboratory and clinical methods will generally not show injury until what exposure of rads is reached
25 rads
contrast agent volume is determined by what following factors?
- patient size
- area being imaged
“radiation area” is an area in which individuals could receive a dose equivalent greater than what in one hour?
0.05 mSv (0.00005 Sv)
increasing the kilovoltage peak (kVp) and decreasing the milliamperage (mA) does what to skin exposure?
decreases skin exposure
pixel characteristics
- smallest element of a digital image
- pixels make up a square matrix
- characterized by location, size, and value
basic building blocks of life and the majority of cell information is stored in
DNA
distortion around the edge of an image due to geometric problems in the shape of an image intensification tube
pincushion distortion
control methods by the brightness sensor in an automatic brightness stabilization (ABS) circuit
- variable mA, preset kVp
- variable mA with kVp following
- variable kVp with selected mA
- variable kVp, variable mA
which is NOT a control method by the brightness sensor in an automatic brightness stabilization (ABS) circuit?
preset kVp with mA following
minimum required thickness (lead equivalent) of a primary protective barrier for systems operating above 125 kVp
2 mm
indicator of somatic effects of radiation
bone marrow
resolving power is measured by
lp/mm
lifetime (cumulative) occupational exposure limit for a 45 year old worker
450 mSv
10 mSv x years
mobile screens are available in this lead equivalent thickness
0.5 mm
how much light is sent to the viewing system (vidicon) between an optical coupling between an image intensifier, and viewing and recording systems?
10%
lowest radiation dose film badges can detect
10 mrads
exposure rate at the tabletop can exceed 10 rads/min if
using ABC on large patients
used to adjust contrast resolution
- window level
- window width
needs to be coordinated with the same frequency of X-ray pulses during cine film generation
camera shutter
temporary sterility to a woman may result from what dose to the gonads?
30 rads
in an image intensifier, this converts light photons to photoelectrons
photocathode
normal viewing distance for binocular vision
16-24 in
pixels are given values for a certain color or gray level; the # of bits used to encode these pixel values is known as
bit depth
term referring to the random probability of an effect occurring
stochastic effect
limiting exposure to no more than 0.05 Sv/yr (50 mSv/yr) will have what effect on stochastic effects of radiation?
limit them
reading of a personnel radiation device is considered a
whole-body dose
what height above the tabletop for an unexposed border on the fluoroscopic screen be visible when automatic collimating devices are used?
ALL heights
what height above the tabletop for an unexposed border on the fluoroscopic screen be visible when manual collimation is used and the collimator is FULLY open?
14 in
are on a fluoroscopic control panel
- mA indicator
- kVp indicator
genetically significant dose is determined by what factors
- # of future children
- x-ray examination rate
- average gonadal dose per examination
affects the amount of scattered radiation during an x-ray exam
- patient entrance skin exposure (ESE)
- exposure time
- kVp
knowledge of long-term biologic effects of chronic low-dose exposure to radiation has been accumulated since
WW2
ratio of brightness between two areas
image contrast (aka, intensifier contrast)
protective curtain thickness (in lead equivalent) must be
0.25 mm
advantages of 3-phase generators
- near constant potential
- relatively high mA available
- higher effective kVp
component that controls the radiation exposure incident at the input phosphor in cine film imaging
aperture
component that changes the magnification mode by changing the FOV
electrostatic lens
high level (boost) fluoroscopy characteristics
- significantly higher tube currents
- a special key and interlock is required with an additional person
- increase in entrance dose rate to the patient
- audible signal must be heard
T/F: secondary radiation (scattered or leakage) has lower energy than the primary beam
true
3 basic types of gonad shields
- flat contact shield
- shaped contact shield
- shadow shield
- 0.25 mm Pb equivalent at 50 kVp
- 0.25 mm Pb equivalent at 75 kVp
- 0.25 mm Pb equivalent at 100 kVp
primary fluoroscopic beam attenuation factors
- 99.4
- 96.1
- 91.4
- 0.5 mm Pb equivalent at 50 kVp
- 0.5 mm Pb equivalent at 75 kVp
- 0.5 mm Pb equivalent at 100 kVp
primary fluoroscopic beam attenuation factors
- 99.9+
- 99.2
- 97.3
examples of information and data management systems that are crucial for the use of radiology in everyday practice
- radiology information systems (RIS)
- hospital information systems (HIS)
- picture archiving and communication system (PACS)
pocket ionization chambers record radiation exposure by
discharging a capacitor
radiation has the potential to do what to cells?
- pass through w/o any damage
- damage
- kill
exposure dose if 500 ergs of x-rays are absorbed by 5 grams of tissue
1 rad
1 gram rad = 100 ergs
when reproductive cells are irradiated there may be changes in
- genes
- chromosomes
lead equivalent thickness of protective glasses to reduce eye radiation exposure by 85-90%
0.25 mm
scattered radiation during an x-ray exam is affected by
- patient entrance skin exposure (ESE)
- exposure time
- kVp
best protective eyewear for the operator to utilize during fluoroscopy
wraparound lead glass eyeglasses
type of contrast reduced by increasing the kVp
subject contrast
f-number of the ____ denotes the speed of a camera
lens
refers to the production of scattered radiation
Compton effect
which body area has the largest distribution of fluoroscopic examinations?
GI tract
type of body habitus that refers to a patient who’s stomach is high, in the middle of the abdomen, and positioned transverse
hypersthenic
increasing the filtration in an x-ray system will
- remove useless low-energy x-rays
- decrease the intensity of the x-ray beam
ALARA is the principle of keeping all radiation doses to what groups as low as possible?
- public
- patients
- operators
components of the Universal Protocol
- verify correct patient
- verify correct procedure
- verify correct site
purpose of image intensified fluoroscopy
- dynamic viewing (angiography)
- real time viewing (live fluoroscopy)
- transient image viewing
materials suitable for use as a tabletop material in an X-ray or fluoroscopic system
- carbon fiber
- aluminum
- Bakelite (plastic)
calculate the total brightness gain for an image intensifier with the following specifications:
- input phosphor diameter: 9 inches
- output phosphor diameter: 1 inch
- flux gain: 50
4050
(9² ÷ 1²) x 50
brightness gain x flux gain
somatic effects damage
individual
personnel monitoring device that indicates radiation exposure by giving off a sound
audible warning device
components of a detector element (DEL) in a flat-panel detector typically include
- scintillation layer
- cesium iodide or gadolinium oxysulfide
- photodiode
- thin-film transistor (TFT)
- capacitor
most amount of scattered radiation occurs at these angles
120 and 135 degrees
highest intensity of scattered radiation occurs at this angle
30 degrees
most common cause of anaphylactic shock seen in radiology
iodine
technically should be iodinated-contrast media, and NOT iodine itself (which is NON-allergenic), but that’s how it’s worded in the exam
size of output phosphor on most modern image intensifiers
1 in
