SPI Review 4 Flashcards
odd field are written by the elctron beam, then the even feild are written, this is called
interlaced display
how long does it take to create one display feild
1/60th of a sec
on typical tv a complete image is created in _____ and the frame rate is ______
1/30th of a sec
30Hz
only 2 choices, white or black, on or off, high contrast narrow dynamic range, poor contrast res
bistable
many levels of brightness, the assignment of diff gray shades for each echo amplitude, diff colors represent diff signal strengths, low contrast, wide dynamic range, improved contrast res
gray scale
determines the brilliance of the signals displayed
brightness
determines the range of brilliancies that are displayed, bistable images are high contrast
contrast
controls
brightness
contrast
real world, a variable attains a continuum of values
analog
computer world, a variable attains only discete values
digital
“the numbers”
digital image data
the smallest element of a digital picture
pixel
the greater the pixel density the greater the detail in the imaged, this is called
spatial detail resolution
spatial res of a crt is determined by
the number of tv lines per frame
a group of __ is assigned to each pixel to store the gray scale color assigned to that ____
bit
pixel
the more bits per pixel, the more shades of gray and the better the _______
contrast resolution
the smallest amount of digital storage, a group of bits, a series of 1 and 0
binary digit
a bit is _____ it has a value of either 0 or 1
bistable
a group of 8 bits
a byte
2 bytes =
16 bits
binary numbers are based on
2
decimal numbers are based on
10
how to calculate the number of gray shades that a collection of bits can represent
find out how many bits are assigned to each pixel
x the number 2 by itself the same number of times as there are bits
the number of gray shades displayed by
“n” bits is 2n
what is the number of shades that can be represented by 10 bits
2 to the 10th
1024
preprocessing
log compression fill in interpolation spatial compouding TGC write magnification persistant time gain?
related to the ability of humans to see the gray scale diff in anatomic structures, lower the high level echoes and boosts the low level echoes. the image dattas dynamic range is reduced
log compression
pre processing, controlled by sonographer
performed on frozen images
post processing
electrical signals from the transducer are ____ and must be converted into _______
analog
digital form
occurs after the image data is in the scan converter, is not re scanned and reads only part of the old data from the original image
read magnification
when the size of an image increases, if the number of pixels is unchanged, pixel size increases **
occurs upon acquisition of the US reflections, preprocessing, system re scans region of interest
write magnification
when the size of an image increases, if pixel size is unchanged, the number of pixels increase***
improves image detail (spatial res) by filling in the missing data
fill in interpolation
example, the edges of a circular structure will be better defined**
scan lines are steered by the transducer in diff directions so structures are interrogated by more than one pulse
spatial compounding
in spatial compounding
speckle and clutter are reduced
spatial res is iimproved
temp res and frame rate are reduced
shadows are reduced or eliminated
only _____ ______ trans use spatial compounding since they are steered ______
phased array
electronically
in spatial compounding the frames are ______ improving ____ __ _____ _____
averaged
signal to noise ratio
the averaging of previous frames to the displayed image, adds a “history” to the current image
persistence aka temporal averaging
persistence good for
smoother image
reduces noise
stationary or slow miving structures
edge enhancement is used for
emphasize the boundary between diff tissues and distinguish interfaces between structures w diff gray scale characterisitic
the ratio of the largest to smallest signal strength that each component processes
dynamic range
the dynamic range of the display indicates the number of
gray shades
narrow dynamic range
few choices
bistable (Black and white)
high contrast
wide dynamic range
many choices
gray scale
low contrast
units for dynamic range
dB, a relatice measurement
the dynamic range of a signal ____ the more it is processed
decreases
transducers dynamic range is the ____ of all the systems components
greatest
the ___ _____ has the lowest dynamic range
recording device
PACS stands for
picture archiving and communications system
combines magnetic and laser technology
magneto optical
digital imaging and communications in medicine provides standards for medical imaging networks
DICOM
fluid moving at a constant speed or velocity
steady flow
fluid miving with a variable velocity, accelerates and decelerates, results from cardiac contraction
pulsatile flow
normal pulsatile flow
60/min
fluid moving with a variable velocity, accelerates and decelerates, results from respiration
phasic flow
normal phasic flow
15/min
the volume of a moving fluid, how much
flow
the speed or swiftness of moving fluid, how fast
velocity
_____ flow may have parabolic or plug patterns
laminar
layers travel at individual speeds with _______ flow
parabolic flow
in parabolic flow the speed is the highest at the
center of the lumen
flow found in normal physiologic states
laminar
small regions of laminar flow will have _____ _____ and _____ _______ ______
similar velocities and narrow doppler specta
chaotic flow in many directions and speeds
turbulents flow
turbulent flow is associated with
cardiovascular pathology and increased velocities
small regions of turbulent flow have vastly different volovitites
dopper spectral broadeneing
flow energy is lost and converted to
sound-murmurs or bruits
vibrations-thrill
a swirling pattern of rotational flow
vortex
eddy currents are
turbulent flow
turbulence may be identified as
spectral broadening
a unitless number indicating whether flow is laminar or turbulent
reynolds number
reynolds number for turbulent flow
> 2,000
reynolds number for laminar flow
blood flows when the total fluid energy at one location differs from the total fluid energy at another location, this is called
energy gradient
energy associated with moving objects
kinetic energy
a form of potential or stored energy that has the ability to perform work
pressure energy
energy is imparted to blood by the contraction of the _____ _____ called ______
left ventricle
systole
three forms of energy loss
frictional loss
viscous loss
inertial loss
the conversion of other forms of energy into heat
friction
ex. blood sliding across vessel walls
describes the thickness of fluid
viscosity
units poise**
causes increased blood viscosity
thick fluid
increased hematocrit or hemoglobin (polythemia or erythrocytosis)
relates to the tendency of a fluid to resist changes in it velocity, objects at rest tend to stay at rest
inertia (inertial loss)
inertial loss results from
pulsatile flow, both acceleration and deceleration
velocity changes at a stenosis
a narrowing or irregularity in a lumen
stenosis
stenosis causes
changes in flow direction
increased velocity in the stenosis
turbulence at exit
pressure gradient accross the stenosis
arterial flow loses its pulatile nature and becomes more continuous
highest velocity at the point of max narrowing, pressure is the lowest here
bernoullis principle
factors that determine resistence
radious of lumen (most imiportant)
length
viscosity of fluid
the weight of the blood pressing on the vessel from heart level to the point of measurement
hydrostatic pressure
pressure measured is greater than circulatory pressure cause hydrostatic pressure is positive
below the heart
pressure measured is less than circulatory pressure because hydrostatic pressure is negative
above the heart
there is no column of blood pressing on the vessels of the body, hydrostatic pressure is 0 at all locations
supine position
pressures measured are true circulatory pressures
standing position
hand extended above heart the pressure is
50mmHg
standing
head pressure is
30mmHg
heart level pressure while standiing
0mmHg
at anke pressure is while standing
100mmHg
while standing pressure at the knee is
75mmHg
calculate pressure measurement
subtract hydrostatic from systolic pressure
vessel collapse, when opposing vessels walls touch each other, when blood pressure is 0mmHg
coaptation
during inspiration the diaphragm
diaphragm presses into abd
during expiration the diaphragm
diaphragm presses into thorax
during inspiration
abd pressure increases
venous flow in legs decrease
pressure in thorax decreases
venous return to the heart increases (arms and abd into the thorax)
during expiration
abd pressure decreases
venous flow in legs increases
thorax pressure increases
venous return to the heart decreases (arms and abd into the thorax)
