Modes, Elevational/Temporal Resolution

3 different modes

A-Mode (amplitude), B-Mode (brightness), M-Mode (motion)

A-mode

graph w/ spiked appearance (determines strength of returning echoes, HIGH spikes=STRONG reflectors)

What colors are strong reflectors, no reflectors, and weak?

strong=bright white

no reflector=anechoic

weak reflector= grays

what is the x-axis of A-Mode

time of flight of pulse/depth

y-axis of A-Mode

strength of reflectors

B-mode

grayscale mode, scan lines displaying as pixels

ON pixel and OFF

ON= white

OFF= black

x-axis for B-Mode

Depth, HORIZONTAL (actually looks vertical)

Z-axis for B-mode

brightness, ANGLED ACROSS

oscilloscope

tool we use to graph a wave

M-Mode

motion, sample rate=PRF

y axis for M-Mode

depth (vertical)

x-axis for m-mode

time (horizontal)

Temporal Resolution

describes moving objects in their correct positions

Real Time Imaging

machine keeping up with sonographer moving transducer

static scanning

creating one frame and displaying it (IMPOSSIBLE to see moving structures)

Frame Rate

frames/second at least 30 f/s, # of pictures created/second

Relationship between frame rate and temporal resolution

increased frame rate=increased temporal resolution

3 factors of frame rate

sound’s speed in medium (fixed)

depth (increased depth, decrease frame rate)

#of pulses per picture decreases= increased frame rate

What is T-FRAME

inverse relationship between frame rate and time

increased frame rate=decrease in time to create a frame (more frames in less time)

Equation for T-Frame

Tframe x Frame Rate=1 (will always be a decimal)

PRP relationship to Frame Rate

inversely

short PRP=shallow imaging=improved frame rate

3 things that change # of pulses/image

1-#of pulses/scan line (single focus/multi focus) increase= decrease in frame rate (more foci=increase in lateral resolution)

2-sector size (wide/narrow) decrease= increase in frame rate

3-lines per angle of sector (line density) decrease= increase in frame rate

Elevational Resolution

creates a thin imaging plane (z-axis)

Another name for elevational resolution

slice thickness (dependent on transducer)

What type of shaped elements create the optimal elevational resolution

Disc shaped elements= BEST elevational resolution

What type of transducer is best for elevational resolution

1 ½ D array transducers= thickness of beam (uses system electronics to focus)

Resolution

the system’s capability to generate accurate images

Spatial Resolution

ability of an imaging system to differentiate and display adjacent structures as being separate (overall DETAIL)

which resolutions does spatial encompass

axial, lateral, elevational

spatial resolution of a digital display is defined as

pixel density

why type of pixel density is superior spatial resolution

high pixel

low pixel density

less pixels per unit, larger pixel size, decreased spatial resolution

dynamic imaging relates to which resolution

temporal resolution

examples of decreasing frame rate

adding more focal zones, increasing #of scan lines (fill-in interpolation), increasing doppler packet size, increasing depth, increasing field of view (sector size)

contrast resolution

system to detect discrete differences between grayscale intensities (echo amplitude)

what improves contrast resolution

improves with more bits per pixel, allows the system to display more shades of gray

What is a bit

smallest configuration of computer memory. Each bit decides a pixels shade of gray

when more bits per pixel are present

more shades of gray can be displayed

contrast resolution is superior when

an image has many shades of gray (allows for isoechoic adjacent structures)

difference between contrast and contrast resolution

contrast=how black and white is our image ? (if you have low contrast=many shades of gray=better contrast resolution (shows more small differences in the grays)

Examples of a decrease in frame rate/temporal resolution

adding more focal zones, increasing number of scan lines (fill in interpolation), increasing doppler packet size, increasing depth, increasing field of view (sector size)