Resolution for Ultrasound

What newer types of transducers have improved slice thickness resolution?

1 and a half dimensional arrays

Which of the following transducers has the poorest depth resolution? 2.6 MHz and 3 cycles/pulse 1.7 MHz and 4 cycles/pulse 1.7 MHz and 5 cycles/pulse 2.6 MHz and 2 cycles/pulse

1.7 MHz and 5 cycles/pulse

In soft tissue, a 3 cycle, 1 MHz pulse has a length of a pulse which is 4.5 mm. What is the axial resolution? 3mm, 1mm, 1.54mm, or 2.25mm

2.25mm (Axial resolution is spl divided by 2 or one half of spl)

What shape of active element creates the best elevational resolution?

Active elements that are disc shaped which would include mechanical and annular phased array transducers

If you are experiencing an axial resolution artifact how can you get rid of it?

Change to a higher frequency transducer

Beam diameter also varies with __________ so azimuthal resolution also changes with _____________

Depth

Slice thickness resolution is also called ____________________________

Elevational resolution

Lateral resolution is best at the ___________

Focus

Temporal resolution uses units of

Hertz , Hz or per second

Which kind of frequency will improve tranverse resolution? ( High or Low)

Higher frequencies have better lateral or transverse resolution

Damping material is only used for _________transducers

Imaging

What is the main advantage of high line density?

Improved spatial resolution; with high line density each image contains more detail

Imaging depth and frame rate are ____________ related?

Inversely

Other names for axial resolution are______________________________

LARRD; longitudinal, axial, range, radial, depth

Other names for lateral resolution are _________________

LATA; lateral, angular, transverse, and azimuthal

Lines spaced far apart are called __________

Low line density

An axial resolution artifact is more likely to happen with a _________ frequency and a _________pulse

Low; long

Can the sonographer change the spatial pulse length of a transducer?

NO

Which kind of beams have better lateral resolution? (Narrow, wide)

Narrower beams

What is the formula to figure out spatial pulse length if needed?

SPL= wavelength x the number of cycles per pulse

What factors give you the best axial resolution?

Short SPL and PD, shorter wavelength, fewer cycles, higher frequencies, lower numerical values

Axial resolution is determined by the ___________________________

Spatial pulse length

What is the formula for axial resolution?

Spatial pulse length divided by 2

Factor of Superior Temporal Resolution are: Frame rate ( low, high) imaging (shallow, deep) focus (single, multiple) sector (narrow, wide) line density (low, high)

Superior temporal resolution has a high frame rate, shallow imaging, single focus, a narrow sector and low line density

Two different transducers create pulses. Both transducers create sound with a frequency of 4MHz. One transducer creates a pulse which comprises 6 cycles and the other, 3 cycles. Which transducer is more likely to create a more accurate image with relation to axial resolution? AND which transducer has a lower numerical value?

The transducer with 3 cycles will create a more accurate image and the transducer with the lowest numerical value also will have a lower numberical measure of axial resolution

What is the main advantage of multiple focal zones?

With multi-focus each scan line has superior lateral resolution because it is narrow over a wide range of depths

What do the two "A's" stand for in LATA when referring to ____________________

angular and azimuthal, lateral resolution

Deeper imaging __________- (decreases, increases, does not affect) frame rate and _____________(improves, degrades, does not affect) temporal resolution?

decreases; degrades

If a new pulsed transducer has many more cycles in its pulse, the image accuracy (improves, degrades, remains the same)

degrades

Since the speed of sound in a medium is a constant then the maximum imaging ______________determines the frame rate

depth

Axial resolution is measured with units of __________

distance

Lateral resolution or angular resolution is measured in units of ______________

distance

The more cycles in a pulse the ________________(greater, lesser, same) the numerical value of the range resolution is

greater

Superior Lateral resolution has a ________frequency and a _______beam width

high; narrow

Two sonographer controlled settings of an ultrasound system determine frame rate they are the____________

imaging depth and number of pulses in each picture

When line density is high (lines are closely packed together) the number of pulses per image ________ and temporal resolution _________

increases, decreases

When the sonographe expands the sector size the number of pulses required to make an image _________ and temporal resolution ___________

increases, decreases

When the sonographer activates multiple focal zones the frame rate _________ and temporal resolution _______________

increases, diminishes or degrades

Shallower imaging _________(increases, decreases) the frame rate and thereby (improve, degrade) ___________ the temporal resolution

increases, improves

Lateral resolution artifact occurs when a beam is ________ (wider, narrower) then the distance between the two reflectors

wider

Lateral resolution is determined by the _________________________

width of the sound beam

Line density and frame rate are ____________related

inversely

Frame rate and the time for one frame are _________ related and ___________

inversely related; recipricals

The elevational or slice thickness resolution is identical to __________resolution with disc shaped active elements

lateral

A high frequency improves lateral resolution because in the far field hgh frequency transducers diverge ____________ then low frequency transducers, therefore the sound beams are _________-

less; narrower

An artifact in axial resolution is created when a __________pulse strikes two closely spaced structures and result in only ________reflection

long; one

Poor temporal resolution is caused by __________ (low, high) frame rates?

low

Damping material or backing material on a transducer is used to ___________________________________

make less ringing which shortens the pulse and results in better axial resolution

Temporal resolution describes the ability to precisely position ________________________ from ___________________

moving structures, instant to instant

What factors affect the number of pulses needed to create an image?

number of pulses per scan line or multi versus single focus, sector size, and line density

Spatial resolution is related to _________ detail in an image. It is determined by _______________________

overall; sound beam's spacing or line density

Axial resolution measures the ability of a system to display two structures that are very close together when the structures are __________________

parallel to the sound beam

Slice Thickness is measured in a direction ________________ to the imaging plane or ____________________ the imaging plane

perpendicular; above-to-below

Temporal resolution is excellent when a system ___________________

produces many frames per second

What do the two "R's" stand for in LARRD when referring to _______________________

range and radial; axial resolution

A higher frequency improves axial resolution because the higher the frequency the ___________ the pulse

shorter

Lateral resolution is the ability of a system to distinctly identify two structures that are very close together when the structures are _______________

side by side, or perpendicular to the sound beam's main axis

Line density is the _________ between the sound beams

spacing

Frame rate is determined by which two factors?

speed of sound in medium and the depth of the imaging