UTZ MIDTERMS

Ultrasound Transducer

Is a device which converts electrical energy to mechanical energy and vise versa

Physical housing assembly

This contains all the individual components. Provides the necessary structural support and acts as an electrical and acoustic (mechanical) insulator.

Electrical connections

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

Piezoelectric Elements

discovered by Curie brothers in 1880 and found that certain crystalline minerals when subjected to a mechanical force became electrically polarized which means that they generated voltages, vice versa

thinner

piezoelectric materials produce higher resonant frequencies

higher

The _____ the frequency, the BETTER the resolution

15 Mhz

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

3 Mhz

transducer can penetrate deep into the body, but the resolution is not as good as the 15 MHz

Backing Materials

shortens the ultrasound pulse length which improves axial resolution

backing material

control length of vibrations from the front face

 araldite loaded with tungsten powder, plastic, cork, rubber, epoxy resin

backing materials

Acoustic Lens

improve image lateral resolution by reducing the beam width of the transducer

width of the beam

determines the lateral resolution

lateral resolution

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

Aluminum, Perspex, Polystyrene

Acoustic Lens Materials

impedance matching layer

sandwich between the piezoelectric crystal and the patient

Impedance Matching Layer

high-purity gamma alumina powder

>15 times

The difference in acoustic impedance between the crystal and the soft tissues within the patient is large

Spatial Pulse Length

Length of a pulse from front to back

SPL = length of each cycle x the number of cycles in the pulse

formula of spatial pulse length

decreases

SPL increases, Frequency and Resolution ______

Linear Array Transducer

produces parallel scan lines

has a rectangular field of view 

linear array

The width of this image is approximately equal to the length of the transducer head with frequency typically above 4Mhz

utz transducer

heart of utz

convex transducer

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

convex

abdominal and obstetric scanning except echocardiography

frequencies: 3.5 MHz, best suited to image deep lying structures.

Sector Transducers

used whenever there is only  small space available

small footprint and wide field of view.

cardiac, cranial, gynecological (TVS transducer) UTZ.

sector

fan shaped, almost triangular

Acoustic Coupling Agent

prevent air between the transducer and the skin of the patient, pH of 5-10

Carbomer

white, fluffy, acidic.

hygroscopic powder with a slight characteristic odor.

EDTA (Edetic Acid)

white crystalline powder, very slightly soluble in water.

soluble in solutions of alkali hydroxides

Propylene glycol

colorless, odorless, viscous hygroscopic liquid with a slight sweet taste

Trolamine

clear, colorless or slightly yellow, odorless, viscous hygroscopic liquid

10.0g

carbomer formula

0.25g

EDTA formula

75.0g (72.4 ml)

propylene glycol formula

12.5g (11.2 ml)

trolamine formula

up to 500g (500ml)

distilled water forrmula

Power or Output Control

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

Depth/ F.O.V Control

allows the increase or decrease the depth of the FOV on the monitor

Gain

refers to the degree of amplification applied to all returning echo signals, it adjusts the overall brightness of the image

Time Gain Compensation (TGC)

Allows adjustment of brightness of a specific depth of the image

Focal zone

should always be placed at the depth of interest on the UTZ image in order to ensure the best lateral resolution. (focuses on specific area)

Zoom/Res

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

Resolution

describes the ability of an imaging system to differentiate between structures, images or events and display them as separate entities

Spatial Resolution

is the ability to display two structures situated close together as separate images, resolution in space

detailed resolution

spatial resolution is also called as:

Axial or Longitudinal

Resolution along the axis of the beam (down the screen) and depends upon the spatial pulse length

axial or longhitudinal

 it is the ability to distinguish 2 objects parallel to the UTZ beam

linear, longitudinal, depth, range

LLDR

Lateral or Azimuthal

Resolution at right angle to the beam (across the screen) and depends upon the beam width

lateral or azimuthal

It is the ability to distinguish 2 objects perpendicular to the UTZ beam

small

the size of transducer, better lateral resolution

narrow

_________ beam width gives better lateral resolution

Contrast Resolution

ability to differentiate between tissues and display them as different shades of gray

Temporal Resolution

ability to display events which occurs at different times as separated images

temporal resolution

ability to detect that an object has moved over time

30-100 Hz

typical frame rate in echo imaging systems are

Absorption

Main factor causing attenuation

absorption

occurs when ultrasound energy is lost to tissues by its conversion to heat

greater

The higher the frequency of sound wave, the _______ the amount of absorption that will occur

bone

will have a much higher absorption coefficient than soft tissue

Reflection

The waves are thrown back

reflection

Interface much larger than wavelength

Specular Reflection

Reflection will bounce in one direction only

Diffuse Reflection

Reflection will bounce at different directions

Scattering

This occurs when an ultrasound wave strikes a boundary or interface between two small structures, and the wave is scattered in different directions

scattering

Interface much smaller than wavelength

Refraction

When the beam encounters an interface between two different tissues at an oblique angle, the beam will be deviated as it travels on through the tissue

refraction

Interfaces between tissues of differing speeds of sound

Divergence

As a beam of ultrasound travels through tissue, it will diverge due to diffraction effects

Artifacts

is an additional, missing or distorted image which does not conform to the real image of the part being examined

Reverberation

Production of spurious (false) echoes due to repeated reflections

reverberation

Artifact that appears as parallel, equally spaced lines

reverberation

It is the result of the presence of 2 or more strong reflecting surfaces

Acoustic Shadowing

Appears as an area of low amplitude echoes (hypoechoic or anechoic) behind an area of strongly attenuating tissue

gas

If the shadowing contains ringdown echoes, it is likely to be

calculus

If the shadowing is clear shadowing, absent of any ringdown, it is likely to be

Acoustic enhancement

Appears as a localized area of increased echo amplitude behind an area of low attenuation

acoustic enhancement

Caused by weakly attenuating structures

Fluid-filled mass

edge shadowing

Occurs at the edges of rounded structures

Side lobes artifacts

Energy within the ultrasound beam exists as several side lobe radiating at a number of angles from a central lobe

Mirror image

They arise due to specular reflection of the beam at a large smooth interface

mirror image

Fluid-air interface

Diaphragm, heart, liver

Double image

Caused by refraction of the beam and may occur in areas such as the rectus abdominis muscle on the anterior abdominal wall

Equipment-generated artifacts

Incorrect use of the equipment controls can lead to artifacts appearing

directly proportional

relationship of gain and noise

operational modes

Mode is an operational state that a system has been switched to

A-mode display (Amplitude Mode)

Echoes are shown as peak and the distance between the various structures can be measured

a-mode display

Is the display of amplitude spikes of different heights

Strength, depth, height of echo

B-mode display (Brightness mode)

Echoes are seen as bright dots which the position of the reflecting structures on a two-dimensional image; static mode

M-mode display (Motion Mode)

Can be used to determine the velocity of specific organ structures

motion mode

Analogous to recording a video in UTZ

time motion mode

TM mode

position motion mode

PM mode

Ultrasonic Cardiography

UCH

Doppler Mode

Makes use of the Doppler effect in measuring and visualizing blood flow

UTZ Stethoscope

an audio amplifier and speaker are all that necessary to listen to the fetal heart

Ranging mode

doppler mode

dynamic imaging mode

m-mode display