SPI Review: Resolutions, Thermal and Mechanical Index

What is the ACCURACY in space, time, and contrast?

Resolution

What is the ability to detect structures that are CLOSE together in great DETAIL?

Spatial resolution

What is DETAIL resolution that creates images with better DETAIL?

Spatial resolution

The number of pixels is _______ related to the spatial resolution?

Directly

An INCREASE in the number of pixels does what to the spatial resolution?

Improves it

A DECREASE in the number of pixels does what to the spatial resolution?

Degrades it

The size of the pixels is _______ related to the spatial resolution?

Directly

An INCREASE in the size of the pixels does what to the spatial resolution?

Improves it

An DECREASE in the size of the pixels does what to the spatial resolution?

Degrades it

The line density is ________ related to the spatial resolution?

Directly

A HIGH line density does what to the spatial resolution?

Improves it

A LOW line density does what to the spatial resolution?

Degrades it

What are the three types of spatial resolution?

1. Axial

2. Lateral

3. Elevational

Spatial compunding _________ SPATIAL resolution?

Improves

Fill-in-interpolation _________ SPATIAL resolution?

Improves

Coded excitation _________ SPATIAL resolution?

Improves

Write magnification _________ SPATIAL resolution?

Improves

Analog converter _________ SPATIAL resolution?

Improves

Multi-focusing _________ SPATIAL resolution?

Improves

Decreasing depth (shallower) _________ SPATIAL resolution?

Improves

Decreasing depth (shallower) _________ SPATIAL resolution?

Degrades

Increasing depth (deeper) _________ SPATIAL resolution?

Degrades

Read magnification _________ SPATIAL resolution?

Degrades

What type of resolutoion is the distingusih between two structures that are PARALLEL to the sound beam?

Axial resolution

What type of resolution does LARRD relate to?

Axial resolution

What does LARRD stand for?

• Longitudinal

• Axial

• Range

• Radial

• Depth

What determines axial resolution?

Spatial pulse length

SHORTER SPL ________ axial resolution.

Improves

SPL=____1_____ x______2_____

1. number of cycles

2. Wavelength

How can you achieve and SHORTER pulse length?

Fewer number of cycles and shorter wavelengths

What are used in transducers to achieve fewer number of cycles?

Backing material

True or False

Backing material leads to LESS ringing and FEWER number of cycles in a pulse which will SHORTEN the SPL to IMPROVE spatial resolution.

True

_________ frequencies IMPROVE spatial resolution.

Higher

What type of resolution distinguishes between two structures that are PERPENDICULAR to the sound beam?

Lateral resolution

What type of resolution does LATA relate to?

Lateral resolution

What does LATA mean?

• Lateral

• Azimuthal

• Transverse

• Angular

What determines lateral resolution?

Beam width/diameter

True or False

Beam width varies with depth.

True

___________ frequency at the near field is LONGER and beam width diverges LESS in the far field.

Higher

LESS divergence means __1____ diameter and ____2_____ frequency.

1. Larger

2. Higher

MORE divergence means __1____ diameter and ____2_____ frequency.

1. Smaller

2. Lower

Multi-foci IMPROVES what type of resolution?

Lateral

LATERAL resolution is best at the ____1_____ of the sound beam where it is ____2______.

1. Focus/ focal point

2. Narrowest

Increasing depth (shallower) _______ LATERAL resolution.

Degrades

HIGHER frequency (LARGE diameter, THIN PZT) _________ LATERAL resolution.

Improves

NARROW beam width _________ LATERAL resolution.

Improves

Imaging at the FOCAL(focus) region will _________ LATERAL resolution.

Improves

HIGH line density _________ LATERAL resolution.

Improves

Using a LINEAR sequential/switched transducer or a ANNULAR phased transducer _________ LATERAL resolution.

Improves

Dynamic aperture _________ LATERAL resolution.

Improves

Dynamic focusing _________ LATERAL resolution.

Improves

THIN HVL (half-value layer) _________ LATERAL resolution.

Improves

To get the beam diameter the NARROWEST what type of transducer should you use?

A HIGH frequency transducer with a LARGE diameter and THIN PZT crystal

Why does a LINEAR sequential transducer have GREAT LATERAL resolution?

Because the shape of the sector is rectangualr and the scan lines produces from it has consistant lateral resolution all the way down (doesn’t spread out)

What allows us to avoid a DECREASE the penetration, while still being able to use a HIGH frequency transducer and increase the FRESENAL ZONE to image DEEPER?

Beam aperture

Shutting OFF crystals mean ___1____ diameter, which means _____2_____ frequency and ____3___ depth and a ____4______in penetration.

1. Smaller

2. Lower

3. Shallower

4. Decrease

True or False

The whole point of dymanic aperture is the NARROW the beam at varies depths and wherever the beam is narrowest (focus/focal point) is where LATERAL resolution is the BEST.

True

When the beam diverges LESS in the far field with a LARGER diameter and THINNER crystal, which allows us to use a _____1______ frequency with ___2_____ _____2______ to AVOID the LOSS of resolution and LESS penetration. This INCREASES (DEEPER in the body) the near zone length due to these higher frequencies.

1. Higher

2. Beam aperture

When the beam diverges MORE in the far field with a SMALLER diameter and THICKER crystal, which leads to the use of a _____1______ frequency. This DECREASES (SHALLOWER in the body) the near zone length due to these lower frequencies.

1. Lower

LOW line density _________ LATERAL resolution.

Degrades

LOW frequency (SMALL diameter and THICKER PZT crystals) _________ LATERAL resolution.

Degrades

THICK HVL (half-value layer) _________ LATERAL resolution.

Degrades

Why does INCREASING depth (deeper in the body) DEGRADE lateral resolution?

The distance between each scan line spread out more as it travels deeper in the body.

What type of resolution is on the 3rd dimension of the beam’s HEIGHT?

Elevational resolution

What type of resolution is also known as Slice thickness?

Elevational resolution

The NARROWER/THINNER the thickness of the HEIGHT of the sound beam, the _________ the ELEVATIONAL resolution.

Better

Elevational resolution is the _______ of the ultrasound beam.

Height

A 1.5 (1 ½) multi-dimensional transducer will ___1____ ELEVATIONAL resolution because it will ADD ON ____2_____ (stacks on more cyrstals).

1. Improve

2. Height

What type of resolution has the ability to differentiate structures with SIMILAR shades of gray from one another?

Contrast resolution

Moving the FOCUS to the AOI will increase _______ resolution, which in turn increases CONTRAST reolution.

Lateral

Images with MANY shades of gray have ________ CONTRAST resolution.

Better

Images with MANY shades of gray have BETTER contrast resolution, but _____ CONTRAST.

Low

Images with FEWER shades of gray have ________ CONTRAST resolution.

Poorer

Images with FEWER shades of gray have POORER contrast resolution, but _____ CONTRAST.

High

What are the smallest building blocks of a DIGITAL picture?

Pixel element

Pixel element is known as what?

Pixels

ONE single Pixel represents _____ shade of gray.

One

What is the number of pixels per inch?

Pixel density

MORE pixels per inch __________ SPATIAL resolution.

Improves

LESS pixels per inch __________ SPATIAL resolution.

Degrades

What is the smallest amount of computer memory?

Binary element

Binary element is also known as what?

Bit

Binary numbers are _________ (0 or 1).

Bistable

What are a group of bits (0100100)?

Binary numbers

What has 8 bits?

A byte

What has 2 bytes or 16 bits?

A word

The MORE bits we have to a SINGLE pixel, the ___1____ shades of gray we have which ___2____ CONTRAST resolution.

1. More

2. Improves

The LESS bits we have to a SINGLE pixel, the ___1____ shades of gray we have which ___2____ CONTRAST resolution.

1. Fewer

2. Degrades

__________ compression means HIGH contrast, which tells us theres a NARROW dynmaic range, few choices/shades of gray, but MORE black/whites. This overall DEGRADES our CONTRAST resolution.

High

__________ compression means LOW contrast, which tells us theres a WIDER dynmaic range, many choices/shades of gray, but LESS black/whites. This overall IMPROVES our CONTRAST resolution.

Low

Pre or Post processing

TGC

Pre

Pre or Post processing

Compression

Pre

Pre or Post processing

Write magnification

Pre

Pre or Post processing

Persistance (temporal compounding/temporal averaging)

Pre

Pre or Post processing

Spatial compounding

Pre

Pre or Post processing

Edge enhancement

Pre

Pre or Post processing

Fill-in-interpolation

Pre

Pre or Post processing

Any change after freeze time

Post

Pre or Post processing

Read magnification

Post

Pre or Post processing

Contrast variation

Post