ULTRASOUND MIDTERMS: Topic 1 - Ultrasound Transducers

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71 Terms

1

Ultrasound Transducer

is a device which converts one form of energy to another.

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Ultrasound Transducer

Converts electrical energy into sound (mechanical) energy, and vice versa.

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Diagnostic Transducer

act as both a transmitter and receiver of UTZ

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- Physical housing assembly

- Electrical connections

- Piezoelectric elements

- Backing materials

- Acoustic lens

- Impedance matching layer

Components And Construction Of A Typical Transducer

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PHYSICAL HOUSING

This contains all the individual components.

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PHYSICAL HOUSING

Provides the necessary structural support and acts as an electrical and acoustic (mechanical) insulator.

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ELECTRICAL CONNECTIONS

Two __ are formed on the front and back face of the crystal by plating a thin film of gold or silver on these surfaces

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thin film of gold or silver

Two electrical connections are formed on the front and back face of the crystal by plating a __ on these surfaces

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Piezoelectric effect

was discovered by Jacques and Pierre Curie in 1880.

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Curie Brothers (Jacques and Pierre)

Who discovered the piezoelectric effect?

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PIEZOELECTRIC MATERIALS

Curie Brothers found that certain crystalline minerals when subjected to a mechanical force became electrically polarized which means that they generated voltages, vice versa.

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Thinner

__ piezoelectric materials produce higher resonant frequencies.

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QUALITY

The frequency also affects the __ of the ultrasound image

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BETTER

The HIGHER the frequency, the __ the resolution

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LESS

The LOWER the frequency, the __ the resolution

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15 MHz

A __ transducer has very good resolution, but cannot penetrate very deep into the body

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3 MHz

A __ transducer can penetrate deep in the body, but the resolution is not as good as the 15 MHz

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BACKING MATERIALS

shortens the ultrasound pulse length which improves AXIAL RESOLUTION.

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front face

BACKING MATERIALS: We are only interested in the vibrations that come off the __ of the transducer.

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Backing or damping material

To try to eliminate the vibrations from the back face, and to control the length of vibrations from the front face, a __ is used

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1. Araldite loaded with tungsten powder

2. Plastic

3. Cork

4. Rubber

5. Epoxy resin

Damping/ Backing material

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ACOUSTIC LENS

The purpose: to improve image lateral resolution by reducing the beam width of the transducer.

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LATERAL RESOLUTION

The width of the beam determines the __

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LATERAL RESOLUTION

is the ability to resolve structures across or perpendicular to the beam axis.

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1. Aluminium

2. Perspex

3. Polystyrene

Acoustic Lens materials

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IMPEDANCE MATCHING LAYERS

is sandwich between the piezoelectric crystal and the patient.

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IMPEDANCE MATCHING LAYERS

High-purity gamma alumina powder.

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SPATIAL PULSE LENGTH

Length of a pulse from front to back.

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SPL = length of each cycle times the number of cycles in the pulse.

SPATIAL PULSE LENGTH Formula

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Shorter

__ pulse length improves resolution.

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decreases

The spatial pulse length (SPL) usually __ with frequency

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Lower

Higher SPL = _ Resolution

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- Linear Array transducers

- Convex transducers

- Sector transducer

TYPES OF ELECTRONIC ARRAY TRANSDUCERS

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LINEAR ARRAY TRANSDUCERS

Produces a parallel scan lines

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LINEAR ARRAY TRANSDUCERS

Rectangular field of view.

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LINEAR ARRAY TRANSDUCERS

The width of this image is approximately equal to the length of the transducer head.

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LINEAR ARRAY TRANSDUCERS

Vascular (vessels), small parts and musculoskeletal applications.

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LINEAR ARRAY TRANSDUCERS

Breast, scrotum and thyroid Utz

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above 4MHz

LINEAR ARRAY TRANSDUCERS Operate at frequencies typically __.

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CONVEX TRANSDUCERS

Convex in shape which provides a wide field of view which diverges with depth.

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CONVEX TRANSDUCERS

Abdominal and obstetric scanning except echocardiography.

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3.5 MHz

CONVEX TRANSDUCERS Operates at __

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CONVEX TRANSDUCERS

best suited to image deep lying structures.

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SECTOR TRANSDUCERS

Fan shaped, almost triangular.

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SECTOR TRANSDUCERS

Used whenever there is only small space available.

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SECTOR TRANSDUCERS

The small footprint and wide field of view

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SECTOR TRANSDUCERS

Cardiac ultrasound, Cranial ultrasound, Gynaecological (TVS transducer)

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ACOUSTIC COUPLING AGENT

Purpose : "To prevent air between the transducer and the skin of the patient"

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↓ REFLECTION = ↑ TRANSMISSION

↑ GEL = __ REFLECTION = __ TRANSMISSION

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ACOUSTIC COUPLING AGENT

Often referred to as "gel"

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ph 5-10

ACOUSTIC COUPLING AGENT ph

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True

T/F Too much gel is far better than not enough!

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1. Carbomer

2. EDTA (Edetic Acid)

3. Propylene glycol

4. Trolamine

5. Distilled water

ACOUSTIC COUPLING AGENT INGREDIENTS

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CARBOMER

It is a white, fluffy, acidic.

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CARBOMER

Hygroscopic powder with a slight characteristic odour

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EDTA (EDETIC ACID)

A white crystalline powder, very slightly soluble in water.

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EDTA (EDETIC ACID)

Soluble in solutions of alkali hydroxides.

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PROPYLENE GLYCOL

A colourless, odourless, viscous hygroscopic liquid with a slight sweet taste.

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TROLAMINE

A clear, colourless or slightly yellow, odourless, viscous hygroscopic liquid.

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Carbomer = 10.0 g

EDTA = 0.25 g

Propylene Glycol = 75.0 g (72.4 ml)

Trolamine = 12.5 g (11.2 ml)

Distilled Water = Up to 500 g (500 ml)

ACOUSTIC COUPLING AGENT FORMULA

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POWER OR OUTPUT CONTROL

This controls the strength of the voltage spike applied to the crystal at pulse emission.

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↑ intensity

↑ power = __ intensity

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↑ intensity = ↑ strength of echo = ↑ px utz dose

↑ power = __ intensity = __ strength of echo = __ px utz dose

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POWER OR OUTPUT CONTROL

Gain

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DEPTH / F.O.V CONTROL

Allows to increase or decrease the depth of the FOV on the monitor

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↑ area of interest = ↑ visualization

↓ depth = __ area of interest = __ visualization

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GAIN

Refers to the degree of amplification applied to all returning echo signals.

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GAIN

Adjust the overall brightness of the image

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TIME GAIN COMPENSATION (TGC)

Allows adjustment of brightness of a specific depth of the image

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FOCAL ZONE

should always be placed at the depth of interest on the utz image in order to ensure the best Lateral resolution

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ZOOM / RES

Allow magnification of the areas of the UTZ image displayed on the monitor

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