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abbie hopkins

on 8 April 2014

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Harmonic Imaging - What is it?
1990s University Of Rochester New York
Development of second and higher order harmonic responses of a tissue to an ultrasound beam

A sharper image is produced
Harmonics result from non-linear behavior of sound
Most effective when the fundamental image is poor.
Harmonics undergoes less distortion

Harmonics vs conventional US
Potential future of US
4D Ultrasound
Ultrasound Imaging
What is it?

Harmonic Imaging Vs Conventional Imaging
2 Harmonic Imaging
1 Conventional Imaging
In Harmonic Imaging, the signal returned by the tissue includes not only the transmitted “fundamental” frequency but also signals of the “harmonic” frequency - twice the fundamental frequency.

The ultrasound system separates out the two components and processes the harmonic signal alone.

The Second Harmonic
Higher Order Harmonics
Higher order harmonics are not used to make images:


1. The range of frequencies that transducers detect is not large to capture higher frequency signals.

2. Higher order harmonics are progressively lower in amplitude

3. The higher frequencies are quickly lost as they pass through tissue

Recently, superharmonic imaging (SHI) has been introduced, which uses the third to the fifth harmonics. This has the added edge of
spatial resolution.
How Are Harmonics Generated?
As a result of:

1) Use of Contrast Agents
2) Interactions with tissues

In conventional imaging, when tissue is evaluated with frequencies centered at 2 MHz, most echoes that come back to the transducer are related to the same 2 MHz frequency band.

Harmonics are multiples of this beam:

Transmitting a band of frequencies centered at 2 MHz will produce harmonic frequency bands centered at 4 MHz, 6 MHz, 8 MHz, etc..

Only the lowest frequency harmonic (double the fundamental frequency) is used to form images.

This doubled frequency sound is called the second harmonic.

The harmonic signals do not come from the ultrasound system itself but are generated in the body.
Contrast Agents
To generate harmonic signals using the patient is injected with a contrast agent containing tiny bubbles.

These are “Microbubbles”

Note: Contrast agents must meet the following five requirements:
Metabolically inert
Long lasting
Strong reflector of ultrasound
Small enough to pass though capillaries.


1-7 microns
Enclosed in membrane

Microbubbles - How do they work?

Act as contrast agents by behaving differently from solid or watery tissues;
They are compressed and expanded more readily
They change their diameter by two to tenfold
They have a natural frequency at which they respond most actively;
This frequency for 1-7 micron microbubbles is in the 2-10 MHz
range that is used for diagnostic imaging
Hence they are much more
than comparable tissue elements such as red blood cells.

There is a difference in
acoustic impedance:
the pulse bounces off the interface between the bubble and surroundings.

The bubble vibrates in response to the shock from the pulse.

This is much like a bell ringing when struck by its clapper.

This vibration generates a
harmonic signal at twice the frequency of the original pulse.

How are the responses generated
How is this beneficial?
Only the strong signal returning from the body (at twice the fundamental frequency) will be the signal that comes back from places where the bubbles are.

Hence, high contrast images are produced.

Free of interference that makes conventional ultrasound imaging difficult.

Bubbles in the tissue is not the only way in which harmonics can be generated

Waves are distorted by properties of tissue.

1. Interactions with tissues
2. Interactions With Tissues
The tissue can affect the speed of sound in the tissue.

When tissue is compressed, the speed of sound increases.

When the tissue is relaxed, the speed of sound decreases.

A sound wave moving through the body is a pressure wave.

This pressure wave compresses and relaxes the tissue as it moves through.

3. Interactions with tissues
The Distortion becomes more pronounced as the wave passes through tissue

Distortion causes harmonics to be produced

Fat distorts wave more strongly than other tissues

Water distorts to a lesser extent

Despite tissue type, the resulting waveform contains fundamental and harmonic frequencies

4. Interactions with tissues
5. Interactions with tissues

The ability to create harmonics in tissues is an effect that is seen in varying degrees throughout the ultrasound field of view.


1. Harmonic Imaging:

A. Creation of an image from sound reflections 10 times the frequency of the transmitted sound.

B. Creation of an image from sound reflection twice the frequency of the transmitted sound.

C. Creation of an image from sound reflection with the same frequency of the transmitted sound.

2. Fundamental Frequency:

A. The frequency of sound created by the transducer and transmitted into the body.

B. The frequency of a sound created by a sound beam.

C. The frequency of sound created by the transducer and released from the body.

7 main Advantages of harmonics produced by the body over conventional ultrasound
3. Improved contrast resolution
7. Improved lateral rotation
5. Ability to obtain images from larger patients.
6. Reduce slice thickness
4. Reduce side-
1. Improve signal to
noise ratio
2. Reduce noise and clutter
Harmonics vs conventional US studies
A study comparing THI and conventional ultrasound
left: an ultrasonic image of an adult heart at the fundamental frequency
same ultrasonic image using tissue harmonic imaging
69 year old woman with ureteral stone. Sonograms of ureteral stone. A -Tisue harmonic iamging , B- 2.5MHz conventional imaging, C=4.0Hz conventional imaging
Comparing THI and conventional imaging in larger patients
Renal carcinoma in an obese patients. Exophytic solid mass in the lower pole of the left kidney is seen on the harmonic image (a) and not on the conventional image (B), which demonstrates the benefits of harmonic imaging in obese patients.
5 renal cyst - (a) because of marked clearing of noise, the harmonic image demonstrates separation and a mural nodule withing the cyst. (b) conventional US image shows artifact from noise

Conventional vs harmonic imaging
4. How do harmonics produce a better image in larger patients?

A) they produce stronger signals
B) They only have to travel through the fat layers once
C) They can travel through the layers more easily
3. which one is harmonic imaging and which one is conventional imaging
A or B

An ultrasound scan (sometimes called a
sonogram), is a procedure that uses high
frequency sound waves to create an image of part of the inside of the body.

- Lazzaro Spallanzani - first person to provide experimental evidence that non-audible sound exits around us
- Spallazani demonstrated that blind folded bats could navigate around obstacles in the dark, but bumped against them when their mouths were covered (1794)
- An experiment by Jurine and Spallazani - where they plugged ears of bats withwax and found the bats bumped helplessly into obstacles - concluded bats require their sense of hearing in order to find their way
- In 1942 Karl Dussik was the first person to use ultrasound as a diagnostic tool
Principles of Ultrasound
As velocity of sound in tissues is fairly constant, the time between the release of a pulse and the reception of a reflected signal is dependent on the distance; i.e. the depth of the reflecting structure.
The reflecting structures does not only reflect directly back to the transmitter, but scatters the ultrasound in more directions. Thus, the reflecting structures are usually termed scatterers (see image below).
Absorption - Some of the energy of the ultrasound is absorbed by the tissues, and converted to heat. This indicates that it may have biological effects, if the absorbed energy is high enough.

Pancreas, liver, spleen, kidney


Will alert you to the presence of some pathologies, e.g. fatty liver, which appears much brighter than it should
Examples of optimising image quality
Field of view (FOV)
Compound imaging

Looking at organs contained within the abdomen, e.g. liver, spleen and gallbladder
echocardiograms to assess the heart
examining conditions affecting the organs of a woman's pelvis, e.g. uterus, cervix and vagina
guiding medical procedures, such as biopsies
Microbes in imaging
Genetically encoded gas vesicles

Gas containing structures with dimensions of tens to hundreds of nanometers.
Produced by microorganisms to control buoyancy
Natural so avoids problem of high surface tension in small particles
Genetic Coding can be used to produce different properties...
Halobacterium NRC-1 is useful for CONTRAST SPECIFICITY
Anabaena flos-aquae are more stable allowing functionalisation with proteins which leads to clustering opportunitues to ENHANCE the ultrasound signal.
Long term; Cells within the body producing these gas vesicles with tailored properties?

Gall bladder polyp. small polyp on the anterior surface of the gall-bladder is seen on the harmonic image (a) with a marked reduction of noise in the gall-bladder lumen compared with that on the conventional us image (b)
Ultrasound. An illustrated guide.
Second edition. Jane Alty and Edward Hoey
Choudhry. S, Gorman. B, Charboneau. J. W. et al. Comparison of Tissue harmonic imaging with conventional US in Abdominal disease. Imaging and therapuetic technology. 1127-1135
Ultrasound Tissue harmonic imaging. Business opportunity in ultrasound Research Coporation Technologies.
Sharpio. R. Wagreich, J. Parsons. R.B, Stancato-Pasik,A. Ygeh.H.C. Lao.R Tissue Harmonic Imaging Sonography: Evaluation of Image Quality Compared With Convetional Imaging.AJR:171N. November199. 1203-1206
Londhe ND, Anand RS. Numerical Investigation of Superharmonic imaging using Chip Excitation [online]. Journal of Medical Ultrasound. 2011. Available from;

What are the covered structures?
1. B

2. A

3. B

4. B


What are the costs?
Ultrasound machines start at about £6,000 and range up to £120,000.

The price depends on the level of technology.

A small clinic can purchase a simple, black and white ultrasound machine at the low end of the range

Hospitals might pay £100,000 for a color machine that produces 4-Dimensional images.

Most new ultrasound machines fall in the £12,000 to £45,000 range.

Used or refurbished machines - which offer a great opportunity for saving money, they are considerably cheaper.

To give an estimate of real machines on the market:

The GE Voluson E8 Expert BT06 Ultrasound Machine starts at about £69,000.
This machine offers a high resolution 4D probe, high quality volume contrast imaging and a 19-inch, high resolution flat screen monitor.
GE medical systems 1997. Harmonic Imaging
Microbubbles in medical imaging: current applications and future directions. Jonathan R. Lindner. Nature Reviews Drug Discovery 3, 527-533 (June 2004)
GE medical systems 1997. Harmonic Imaging
GE medical systems 1997. Harmonic Imaging
GE medical systems 1997. Harmonic Imaging
GE medical systems 1997. Harmonic Imaging
GE Voluson 730 Expert Ultrasound Machine.
UCLA health system. Endocrine test
G E Medical system. 1997. Harmonic Imaging
G E Medical system. 1997. Harmonic Imaging
G E Medical system. 1997. Harmonic Imaging
Tissue Harmonic Imaging Sonography: Evaluation of Image Quality Compared with Conventional Sonography. 1998
Business Opportunity In Ultrasound. Ultrasound Tissue Harmonic imaging. 2003.

Comparison of Tissue Harmonic Imaging with Conventional US in Abdominal Disease. IMAGING & THERAPEUTIC TECHNOLOGY. 2000.

Comparison of Tissue Harmonic Imaging with Conventional US in Abdominal Disease. IMAGING & THERAPEUTIC TECHNOLOGY. 2000.

Comparison of Tissue Harmonic Imaging with Conventional US in Abdominal Disease. IMAGING & THERAPEUTIC TECHNOLOGY. 2000.
Ultrasound care specialist. Professional & Caring diagnostic Medical Ultrasound services
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