UTZ RTE pt. 1

1918

What year was Sound Navigation and Ranging was used

Infrasound

refers to sound waves with frequencies below 20 Hz, which are typically below the range of human hearing but may be audible at high intensities

Volcanic eruptions

Earthquakes

Ocean waves

Natural source of infrasound include:

Explosions

Industrial machinery

Wind turbines

Human-made sources of Infrasound include:

Inaudible Sound

frequencies below 20 Hz (infrasonic) or above 20 kHz (ultrasonic), which are beyond human hearing

Inaudible frequencies

are widely used in medical applications, such as ultrasound imaging for diagnostics.

Audible Sound

frequencies between 20 Hz and 20 kHz, which the human ear can detect

Ultrasound

refers to sound waves with frequencies above kHz, beyond the range of human hearing, used in various applications

Ultrasound

It is commonly used in industries for non-destructive testing, detecting material flaws, and measuring thickness

underwater communication, animal echolocation, therapeutic treatments like physiotherapy

Ultrasound also plays a role in ____, ____, and ______

Diagnostic ultrasound

a medical application of ultrasound technology used to create real-time images of internal organs, tissues, and blood flow.

It is widely used in obstetrics for monitoring pregnancies and diagnosing conditions affecting organs like the heart, liver, and kidneys, offering a non-invasive and radiation-free imaging option.

Longitudinal / Compression waves

Transverse / Shear waves

Surface / Rayleigh waves

TYPES OF ULTRASOUND WAVES

Longitudinal / Compression waves

are waves in which the particles of the medium move parallel to the direction of the wave’s propagation

Sound waves in air

are a common example of longitudinal waves.

Transverse / Shear waves

are waves in which the particles of the medium move perpendicular to the direction of the wave’s propagation

Water waves

Electromagnetic waves

Light waves

Examples of transverse waves include ___, ___, and ____

Surface / Rayleigh waves

are seismic waves that travel along the Earth’s surface, causing the most damage during earthquakes

Surface / Rayleigh waves

They move slower than body waves but have larger amplitudes, resulting in stronger ground shaking.

Period (T)

Amplitude

Wavelength (�)

Frequency

Velocity

ACOUSTIC VARIABLES

Period

time for one complete cycle

Wavelength

length of one wave cycle

Amplitude

maximum displacement of a variable

Frequency

cycles per second (Hz)

Velocity

frequency x wavelength

inversely

Wavelength is _____ proportional to frequency

Wavelength

determines resolution

megahertz (MHz)

Frequency is measured in?

Frequency

It directly affects image quality and depth penetration

Shorter wavelength

Better resolution

Less penetration (limited to superficial structures)

More absorption

High Frequency means?

BANDWIDTH

Range of frequencies in an ultrasound pulse

Shorter spatial pulse length

Wider range of frequency

Wide Bandwidth means?

Physical Housing

Electrical Connections

Piezoelectric Elements

Matching Layer

Acoustic Lens

Backing Layer (Damping Material)

COMPONENTS OF TRANSDUCER

Physical Housing

● Encloses and protects all internal components

● Provides structural support

● Acts as both electrical and acoustic insulator

Electrical Connections

● Made of a thin film of gold or silver

● Allow transmission of electrical signals to and from the crystals

Piezoelectric Elements

Crystalline materials that produce voltages when exposed to mechanical pressure

Jacques and Pierre Curie

Who discovered Piezoelectric elements?

higher resonant frequencies → better image resolution

Thinner elements - ______ - ___________

Matching Layer

● Located in front of the piezoelectric crystal

● Minimizes the acoustic impedance mismatch between the transducer and the patient’s skin

● Improves transmission of ultrasound energy into the body

Acoustic Lens

● Positions at the tip of the transducer

● Focuses the ultrasound beam at a desired depth

● Helps enhance lateral resolution

Backing Layer (Damping Material)

● Located behind the piezoelectric crystal

● Absorbs excess vibrations after pulse generation

● Shortens the pulse duration, improving axial resolution

epoxy resin loaded with tungsten

What is the Backing layer typically made of?

PIEZOELECTRIC CRYSTALS

● These materials generate electrical signals when subjected to mechanical pressure and produce mechanical vibrations when an electric voltage is applied.

● Capable of changing electrical signals into mechanical (ultrasound) waves

Piezoelectric Effect

Refers to the ability of certain materials to produce an electric charge in response to mechanical pressure

Lead zirconate titanate (PZT)

What is used in Piezoelectric Effect?

● Quartz

● Tourmaline

● Rochelle salt

Natural Piezoelectric elements

more

Small diameter crystal → ___ beam divergence

ULTRASOUND TRANSDUCER

A handheld device that emits and receives sound waves using piezoelectric crystals to produce medical images

Convex / Curvilinear

● Offers a wider field of view for larger or deeper structures

● Most frequently used for abdomen and obstetrics

length

● The linear transducer’s ____determines the image’s sector width and shape.

Linear / Sector

Offers detailed resolution at superficial depths.

Most frequently used with MSK, nerve, small parts, vascular, and pediatric applications

Phased-Array

● has a small footprint with a sector image shape and features high temporal resolution and penetration

● This allows clinicians to image structures that are moving in real-time

● Most frequently used with applications for cardiac (echocardiography) and transcranial (pediatrics)

Endocavity transducers

● is a specialty transducer used to image structures from inside the body

● This allows for better visualization of structures that are not easy to view with a surface transducer

● The shape of the imaging surface provides a very wide field of view

● Most frequently used for OB/GYN and urology application

Ultrasonography

is a diagnostic imaging technique that uses high-frequency sound waves (ultrasound) to create real-time images of the inside of the body

Ultrasound

is a pressure wave which travels through a medium

longitudinal

In medical imaging, What waves are commonly used?

ATTENUATION

The gradual loss of sound wave energy as it travels through a medium

Absorption

Reflection

Scattering

Refraction

Divergence

Factors of Attenuation

greater

High-frequency waves means ____ attenuation

high

low

Bone & Muscle = ____ attenuation

Fluids & Soft tissue = __ attenuation

Absorption

conversion of sound energy into heat

Reflection

bouncing of sound at tissue interfaces

scattering

redirection of sound in multiple directions

Refraction

- bending of sound wave path

Divergence

- spreading out of the sound beam

Convex / Curvilinear : 2 - 5 MHz

Linear probe: 6 - 15 MHz

Phased Array probe: 2 - 5 MHz

Endocavity probe: 5 - 9 mhZ

FREQUENCY RANGE (MHz) of:

Convex / Curvilinear

Linear probe

Phased Array probe

Endocavity probe

Convex / Curvilinear: Abdominal and obstetric imaging

Linear probe: Vascular, small parts, thyroid, breast,and MSK applications

Phased Array probe: Cardiac (echocardiography), transcranial imaging

Endocavity probe: Transvaginal, transrectal imaging

APPLICATION of

Convex / Curvilinear

Linear probe

Phased Array probe

Endocavity probe

Convex / Curvilinear: Wide, curved

Linear probe: Rectangular FOV

Phased Array probe: Flat faced transducer, wide FOV

Endocavity probe: Curved, narrow

FIELD OF VIEW of

Convex / Curvilinear

Linear probe

Phased Array probe

Endocavity probe

Bone has high absorption,

nearly proportional to the square of frequency

● Soft tissue absorption

is approximately proportional to frequency

Blood → Fat → Nerve → Muscle → Skin → Tendon → Cartilage → Bone

Increasing protein content gives increasing absorption:

Fresnel zone

near field

Fraunhofer zone

far field

ACOUSTIC IMPEDANCE

A property of a medium that resists the transmission of sound

Z = p x c

Z (acoustic impedance), p (density), c (speed of sound)

ACOUSTIC IMPEDANCE is calculated as