DMS US PHYSICS TEST 1

basic physics, sound, tech

Infrasonic

below 20 hz

Audible sound

20hz-20,000 hz

Ultrasonic

above 20,000 hz

Diagonostic ultrasound

2-20 MHz

soft tissue propagation speed

1540 m/s

High Frequency

• Better resolution

• Less penetration

• More attenuation

Low Frequency

• Worse resolution

• More penetration

Attenuation

loss of sound energy as it travels through tissue

Attenuation caused by

absorption, reflection, scattering

Transmisson

deeper explorer

CPU (central Processing Unit)

the brain of ultrasound machine

RAM

temporary memory, data lost when off

DICOM

• Digital Imaging and Communications in Medicine

• Standard for medical images

• Allows images to be shared between systems

PACS

• Picture Archiving and Communication System

• Stores, retrieves, and displays medical images

• Works with DICOM

Which system stores ultrasound images?

PACS

Piezoelectric Crystals (Transducer)

= pressure electricity

ability to convert mechanical energy into electric

Why do we use ultrasound gel?

To eliminate air

Why doesn’t sound travel in space?

no medium

Why use lower frequency for deeper organs?

• Less attenuation, better penetration

Color Maps (BART)

Blue away Red Toward

Acoustic variables

inform us which waves are sound waves

Examples of acoustic variables are

pressure, density, distance

Acoustic Parameters

describe certain parts of sounds

What are the seven parameters?

wavelength, frequency, power, amplitude, period, intensity, speed

unrelated

two items that are not associated

related

two items that are associated/ affiliated, but the relationship between them does nit have to be specified

Directly related

two items that are associated such that when one item increases the other increases

Inversely related

two items are associated such when one items increases the other decreases

reciprocal relationship

when two numbers are multiplied together result is one

sound

a mechanical longitudinal wave

compression

increase in pressure through medium aka squeezed together

rarefactions

decreases in pressure through medium aka streched apart

Hyperechoic

big difference in impedance = bright echo

Hypoechoic

small difference in impedance = weak echo

Anechoic

no difference in impedance = no echo

Bone

4080 m/s fastest

Air

330 m/s slowest

Transverse wave

particles move perpendicular to the direction

Longitudinal Wave

particles move in same direction as the wave

Upper Metric Scale in order

base, deca, hecto, kilo, mega, giga

Lower Metric Scale in order

base, deci, centi, mili, micro, nano

When you go up on metric scale you should..

divide = up

When you go down metric scale you should..?

multiply = down

High frequency

= short wavelength, more attenuation, shallow penetration.

Low Frequency

= long wavelength, less attenuation, deep penetration.

Propagation Speed = Frequency × Wavelength

c = f × λ

acoustic impedance

total resistance the tissue gives sound wave

impedance = density x speed

In-phase

peaks and troughs of a pair of wave happen at SAME time

Out of Phase

peaks and troughs of a pair of waves happen at different times

constructive interference

amplitude of new wave is greater than both original waves

destructive interference

the amplitude of the new wave is less than one of the original waves