ch 17 - Harmonics + Contrast Agents

Harmonics = ___ the fundamental freq

2x

Harmonics are also called “____” harmonics

second

Harmonics result from _____ (linear/non-linear) behavior of sound

non-linear

Harmonics are MOST effective when fundamental image is _____

poor

2 forms of Harmonics

contrast, tissue

Non-linear behaviors means _____ or _____

asymmetrical or irregular

_____ harmonics are created during TRANSMISSION

Tissue

Tissue Harmonics DON’T occur at _______ depths

superficial

Most artifacts occur in the 1st few _____ of transmission

cm

Creating “Tissue” Harmonics involves

• ________ and _________

• sound thru tissue, speed = slightly _____

• travels ____ (faster/slower) during compression, ____ (faster/slower) during rarefaction

• alter in speed = change in wave ____

• _____ (shallow/deep) sound travels = ____ (weak/strong) harmonic waves

compression, rarefaction, uneven, faster, slower, shape, deeper, stronger

inc harmonics = ____ image quality

inc

______ ______ harmonics = create harmonics + get rid of fundamental reflections

Pulse Inversion

Pulse inversion involves a ___ and ____ pulse sent down each line

positive and negative

Disadvantage of Pulse Inversion = ____ the number of ___ need to make an image

2x, pulses

inc Pulse Inversion = ____ frame rate = _____ temporal resolution

dec, dec

Power Modulation Harmonics involves sending one ____ pulse and one ____ pulse down each line

strong, weak

inc Power Mod = ____ frame rate = ____ temporal res

dec, dec

Gradual Harmonic signaling means ____ cannot occur

distortion

Harmonic images cause ___ noise and have a ____ signal-to-noise ratio bc it only uses ____ beams

less, higher, strong

Contrast Agents are also called

microbubbles

Microbubbles are either _____ or ______

swallowed or injected

5 requirements of contrast agents

1. safe

2. metabolically inert

3. long lasting

4. strong reflector

5. pass through capillaries

Contrast Harmonics is created through the interaction bw the ____ freq and the ____

primary, microbubbles

Microbubbles grow/strength due tot the ____ wave

pressure

Harmonics result from the ___ changes in bubble ____ while interacting with sound beam

uneven, size

High pressure causes the bubbles to ___ and the pressure INSIDE ——

shrink, inc

Mechanical Index (MI) is used to estimate the amount of _____ _____

contrast harmonics

MI is dependent on _____ and _____

frequency and pressure

Microbubbles are ____ reflectors, the size of _____ and resonate at ____ MHz

strong, RBC, 2-4

Low MI = _____ (value)

0.1

Low MI = not enough ___ to make bubbles expand/____ = ____ harmonics = _____ behavior (linear/non-linear)

pressure, contract, NO, linear

Higher MI = _____-_____(value)

0.1-1.0

Higher MI = _____ (no/some/lots) harmonics =______ (linear/non-linear) behavior = ____ freq = ____ beam strength

some, non-linear, low, strong

Highest MI = _____ (value)

> 1.0

Highest MI = _____ (no/some/strongest) harmonics = bubble ____ = ______ non-linear behavior = bubbles almost ____

strongest, disruption, extreme, rupture

The ____ is what traps the gas and _____ the life of the bubbles

Shell, inc

Shells are made to be ____

flexible

The ____ gas determines the _____ of the microbubble

internal, stability