P2 PROBES

Parts of a probe/tranducer

Electronics, Case/insulation, Backing material, Piezoelectric crystals, matching layer

It is the key element of the system converts electrical energy to mechanical energy

Transducer

electric, referring to the generation of electric charge from mechanical stress. It involves the ability of certain materials, like quartz or specific ceramics, to produce an electric charge when subjected to mechanical stress.

Piezoelectricity

elements convert electric voltages into ultrasound pulses and convert returning echoes back into voltages

Transducer components

What happens in piezoelectric

It generates electricity

What is the principle of the transducer

Piezoelectric crystal

PIezoelectric crystals contains what?

Positive and negative charge called dipole

Components of a single element transducer

Case, Crystal, Damping material, matching layer

heart of transducer is the piezoelectric crystal or transducer element

Crystal

Crystalline materials

Quartz, Lithium niobate, lithium sulfate

piezoelectric crystal converts what?

Electrical energy into mechanical vibrations

What is the most common piezoelectric crystals?

Lead zirconate (PZT) and Poly vinylidene Diflouride (PVDF)

What crystals are responsible for connverting electrical signals into mechanical vibrations vicer versa forming the basis of ultrasound emission and reception?

Lead zirconate (PZT) and Poly vinylidene Diflouride (PVDF)

determines the stress induced signal and capacity of crystals use as an ultrasound receive

Generated electric field

The critical dimension of piezoelectric crystal is its?

Thickness

indicates the efficiency of energy conversion from electrical to mechanical

Electromechanical coupling factor

Thinner elements tend to operate in what frequency?

high

In order to have a single wave move back & forth between the front and back of crystal, the distance from one surface to the next should be

One half wavelength

Maximum energy transfer between the mechanical & electric state occurs?

When thickness is one half the wavelength of UTZ

What celsius will destroy the property of a crystal?

350

What happens if there is a improper cable?

will recieve bad energy

This is positioned behind the piezoelectric crystals also designed to absorb sound waves that propagate backwards

Damping material/Backing

What materials are commonly used for the Damping/backing

Combination of epoxy resin and tungsten powder

What is the use of Damping/backing

Reduces the sensitivity of transducer because it lowers the intensity of output signal

This helps to optimize sound wave transmission between the transducer and the patients skin by reducing impedance mismatch

Matching layer

Composed of epoxy resin-tungsten powder matrix designed to reduce the reflection of UTZ emission at the crystal’s surface

Matching layer

Provides protection to the internal components and serves as structural support for the transducer

Housing

Connects the transducer to the ultrasound machine and transmits electrical signals back and forth

Cable and connector

This is positioned at the front of the transducer directly above the piezoelectric crystals

Acoustic lens

an aqueous gel is applied to the skin before transducer contract this elminates the air layer and facilitates passage of sound in and out of the tissue

Coupling medium

Prevent air between the transducer and the skin of the patient Increase gel=decrease reflection=increase transmission

Acoustic coupling agent

Acoustic coupling agent ingredients

Carbomer, EDTA, Propylene glycol, Trolamine, Distilled water

Fluffy white acidic powder that allows other ingredients in the products to work Hygroscopic powder with a slight characteristic odour.

Carbomer

White crystalline powder, very slightly soluble in water Soluble in solutions of alkali hydroxides

EDTA (edetic acid)

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

Propylene glycol

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

Trolamine

Main solvent/base makes up much of the gel and provides the medium through which ultrasound can travel

Distilled water

Why is gel important?

Elimates air, Improves acoustic coupling/imagequality and allows the probe to move smoothly

ability of images to reproduce small objects

Detail

Refers to reproducing larger objects that have little tissue differentiation

Definition

Results from the unequal magnification of anatomical objects that lie different distances from the image receptor

Distortion

measures the ability of an imaging system to reproduce very small high contrast objects (1mm)

Spatial resolution

Ability to differentiate anatomic structures having similar tissue characteristics

Contrast resolution

Variation in signal level contributed by noise causes brightness flunctuations in the image

Noise

is the ability to image closely spaced interfaces on the axis of the ultrasound beam Symbol: AR
Units (mm)

Axial resolution

axial resolution depends primarily on the length of the ultrasound pulse in space

Spatial Pulse Length

Frequency increases, the wavelength decreases, and if the number of pulses remains constant, the spatial pulse length is reduced→better axial resolution

Ultrasound Frequency

To damp an UTZ beam means to stop the pulse very quickly • Returning echoes are sharpe

Damping factor

is the ability to image closely spaced interfaces perpendicular to the axis of the ultrasound beam

Lateral resolution

Lateral resolution is approx. equal to the effective beam width • Decreasing the beam width improves the lateral resolution by allowing objects close togethe

Beam width

The higher the ____ the better the lateral resolution for a greater range in tissue

Frequency