Ch. 17 Harmonics and Contrast Agents Flashcards
____________________ imaging is creation of an image from sound reflections at twice the fundamental frequency
Harmonic Imaging is creation of an image from sound reflections at twice the fundamental frequency
________________________ frequency is the frequency of sound created by the transducer and transmitted into the body.
Fundamental frequency is the frequency of sound created by the transducer and transmitted into the body
____________________ freequency is twice the fundamental (transmitted) frequency
Harmonic Frequency (also called second harmonic frequency) is twice the fundamental (transmitted) frequency
Harmonic frequency sound waves arise from ________________________ behavior
Harmonic frequency sound waves arise from nonlinear behavior
What does Harmonic Imaging do?
Hamonic Imaging gets rid of low level noise
Most useful in improving poor quality images because harmonic frequency waves undergo less distortion
A ____________________________ image is the image created by processing reflections that have the same frequency as the transmitted sound.
A Fundamental Image is the image created by processing reflections that have the same frequency as the transmitted sound
A _____________________________ image is the image created by processing reflections that are twice the fundamental frequency.
A Harmonic Image is the image created by processing reflections that are twice the fundamental frequency.
Harmonic imaging is most effective when the fundamental image is ____________________ because the harmonic frequency waves undergo less distortion
Harmonic imaging is most effective when the fundamental image is suboptimal because the harmonic frequency waves undergo less distorion
Two forms of Harmonics are important in diagnostic sonography what are they?
- Tissue Harmonics
- Contrast Harmonics
Linear means ________________________ or _________________________.
linear systems respond in an even manner.
Linear means proportional or symmetrical
linear systems respond in an even manner
Nonlinear means ___________________ or _____________________________.
A system is nonlinear when it behaves unevenly.
Nonlinear means irregular or disproportionate
Linear behavior is _____________________________.
symmetrical
Nonlinear behavior is _______________________________.
asymmetrical
Energy is converted from Fundamental frequency to the Harmonic frequency; this conversion creates ____________________________ during transmission.
Energy is converted from Fundamental frequency to the Harmonic frequency; this conversion creates Tissue Harmonics during transmission
In tissue harmonics sound travels at slightly _______________ speeds through soft tissue.
In tissue harmonics sound travels at slightly uneven speeds through soft tissue
A sound wave is a series of ____________________ and ____________________.
A sound wave is a series of compressions and rarefractions
In tissue harmonics:
Speed in Compression is ___________________(faster,slower)
Speed in Rarefractions is _____________________(faster,slower)
Speed in Compression is faster
Speed in Rarefractions is slower
During _______________ imaging, significant amounts of artifact arise within the first few centimeters of tissue.
During Fundamental imaging, significant amounts of artifact arise within the first few centimeters of tissue
Do tissue harmonics exist at extremely superficial depths?
no
Tissue harmonics are more likely to be created where?
along the beams main axis
Beams that are most likely to create harmonics are least likely to create ____________________
Beams that are most likely to create harmonics are least likely to create artifacts
Tissue Harmonics are created _______________ in the tissues
Tissue Harmonics are created deeper in the tissues
Tissue Harmonics are created during _________________________
Tissue Harmonics are created during transmission
Tissue Harmonics are created by ____________________ behavior in the speed of sound.
Tissue Harmonics are created by nonlinear behavior in the speed of sound
Harmonic Imaging reduces artifacts by increasing the ___________________________________
Harmonic Imaging reduces artifacts by increasing the signal-to-noise ratio
Where is Tissue Harmonics the best?
middle of the image (slightly deep)
______________________________ Harmonics is an imaging technique specifically designed to utilize harmonic reflections, which are distortion free, while eliminating distorted fundamental reflections.
Pulse Inversion Harmonics is an imaging technique specifically designed to utilize harmonic reflections, which are distortion free, while eliminating distorted fundamental reflections.
Reflections contain both _______________________ and ________________________ frequencies
Reflections contain both fundamental and harmonic frequencies
________________________ imaging creates images from the portion of the reflected sound that has the same frequency as the transmitted sound.
Fundamental Imaging creates images from the portion of the reflected sound that has the same frequency as the transmitted sound.
__________________________ imaging creates images only from the harmonic frequency, which is 2 times the fundamental frequency.
Harmonic Imaging creates images only from the harmonic frequency, which is 2 times the fundamental frequency
____________________________________ is when two consecutive ultrasound pulses are transmitted down each scan line. The First is a typical pulse, Second is an inverted copy that is “out-of-phase” with the first.
Pulse Inversion is when two consecutive ultrasound pulses are transmitted down each scan line. The First is a typical pulse, Second is an inverted copy that is “out-of-phase” with the first.
Wherever a compression exists in the first pulse, a ________________________ exists in the second.
Wherever a compression exists in the first pulse, a rarefaction exists in the second
Pulse Inversion Harmonics separate the __________________________ from the ____________________ frequencies
Pulse Inversion Harmonics separate the Harmonics from the Fundamental frequencies
With Pulse Inversion, a __________________________ and then a ____________________ pulse is transmitted down each scan line
With Pulse Inversion, a positive and then a negative pulse is transmitted down each scan line
The pulse reflections are combined in the ________________________
receiver
Two inverse fundamental frequencies are ____________________________ because of destructive interference
Two inverse fundamental frequencies are canceled out because of destructive interference
The Harmonic portions of the reflections are in phase and interfere _______________________________
The Harmonic portions of the reflections are in phase and interfere constructively
With Pulse Inversion, only the ______________________ portions of the reflections remain, which form an image with less distortion.
With Pulse Inversion, only the Harmonic portions of the reflections remain, which form an image with less distortion.
What type of resolution is diminished with pulse inversion?
temporal resolution
______________________________________________ is an imaging technique designed to enhance harmonic reflections which contain less distortion while eliminating distorted fundamental reflections. It achieves the same goals as pulse inversion but uses a different engineering approach
Power Modulation Harmonic Imaging is an imaging technique designed to enhance harmonic reflections which contain less distortion while eliminating distorted fundamental reflections
With Power Modulation, the harmonics are extracted by sending one ________________ pulse, and one ___________ pulse down each scan line.
With Power Modulation, the harmonics are extracted by sending one strong pulse, and one weak pulse down each scan line.
Temporal Resolution is _________________ due to a decrease in the frame rate during power modulation
Temporal Resolution is decreased due to a decrease in the frame rate during power modulation
What is the difference between Pulse Inversion and Power Modulation?
one negative and one positive
one strong pulse and one weak pulse
________________________________, also called microbubbles are gas bubbles encapsulated in a shell.
Contrast Agents, also called microbubbles are gas bubbles encapsulated in a shell
Contrast agents have a different acoustic fingerprint than ______________ or _______________
Contrast agents have a different acoustic fingerprint than blood or tissue
Microbubbles/Contrast agents are either ________________ or _______________ into the body.
Microbubbles/Contrast agents are either injected or ingested into the body
What do Contrast Agents do?
Contrast Agents create strong reflections that light up blood vessels or other anatomy
Contrast Harmonics are created during ___________________ due to ___________________ changes in size of the bubble when exposed to sound beam, what is this called?
Contrast Harmonics are created during reflection due to nonlinear changes in size of the bubble when exposed to the sound beam, this is called Resonance
When exposed to the high pressure component of a sound wave aka Compression, the bubble _____________________ and the pressure inside the bubble ____________________.
When exposed to the high pressure component of a sound wave aka Compression, the bubble shrinks and the pressure inside the bubble increases
When exposed to the low pressure component of a sound beam Rarefaction, the bubble _____________________
When exposed to the low pressure component of a sound beam Rarefaction, the bubble expands
Bubbles ____________ to a greater extent than they ______________.
Bubbles expand to a greater extent than they shrink
The amount of contrast harmonics produced may be estimated by a number called the _____________________________________
The amount of contrast harmonics produced may be estimated by a number called the Mechanical Index
The numerical value of the mechanical index increases with _______________ frequency sound, and _________________ sound waves.
The numerical value of mechanical index increases with lower frequency sound, and stronger sound waves
MI is _______________ (indirectly, directly, unrelated) related to peak rarefractional pressure
MI is Directly related to peak rarefractional pressure
Mechanical Index formula:
MI = peak rarefraction pressure divided by square root of frequency
Tissue Harmonics:
Created during _____________________________ in tissue
Occurs __________________________________________ in tissue
Results from ______________________ behavior of transmitted sound beam
____________ harmonic signal
Tissue Harmonics:
Created during transmission in tissue
Occurs as sound propagates in tissue
Results from nonlinear behavior of transmitted sound beam
weaker harmonic signal
Contrast Harmonics:
Created during _______________________ off of microbubble
Occurs only when contrast agents are present and with MI’s greater than ___________
Results from ____________________ behavior of microbubble
____________________ harmonic signal
Contrast Harmonics:
Created during reflection off of microbubble
Occurs only when contrast agents are present and with MI’s greater than 0.1
Results from nonlinear behavior of microbubble
stronger harmonic signal
What nonlinear behavior creates tissue harmonics?
Sound travels faster in compressions and slower in rarefractions
What nonlinear behavior creates contrast harmonics?
microbubbles expand to a greater extent than they compress
This uneven behavior is called resonance
Beams with an intermediate mechanical index
0.1 to 1.0 create a relatively small amount of harmonics
Beams with a high mechanical index
greater than 1.0 create substantial harmonic signals. Bubble disruption is an ex of extreme nonlinear behavior, which creates very strong harmonic reflections.
___________sound beams do not create harmnincs because the microbubbles expand and contract evenly in a linear fashion
Low mechanical index
Two characteristics of contrast agents are important:
the nature of the outer shell(gas bubbles without shells such as agitated saline shrink and quickly vanish as the gas dissolves in blood)
the gas that fills the microbubble(smaller gas molecules are more likely to leak through the shell and shrink the bubble. Large gas molecules find the shell less permeable and remain trapped within the bubble)
