Part 1 - important (notes) Flashcards by Gabriella Santangelo

Infrasound

<20 Hz

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Audible Sound

20 - 20,000 Hz

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Ultrasonic

> 20,000 to 20 Khz

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Diagnostic ultrasound

2 to 15 Mhz

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Time to complete one cycle
Unchanged by monographer
Sec/usec
Determined by : Source

Period

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of cycles/ sec (affects ———-penetration & axial res)
Unchanged by monographer
Hertz
Determined by: source

Frequency

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Rate work is performed
Unchanged by monographer
watts
Determined by Source

Power

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Concentration of energy in a sound beam
Changed by sonographer
watts/cm^2
Determined by source

Intensity

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Length/distance of single cycle
mm,cm
Changed by sonographer
Determined by source & Medium

wavelength

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Rate sound travels in a medium
Unchanged by sonographer
m/sec
determined by : medium

prop speed

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Amplitude , Power & Intensity are all related how ?

Direct

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Period & Frequency are related how

Inverse

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Power & area are related how

Inverse

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Wavelength & frequency are related how

Inverse

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Stiffness & Speed are related how

Direct

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Speed & Density are related how

Inverse

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Frequency , speed, intensity and power are related how

UNRELATED

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3 bigness parameters changed by the output power

Amplitude
Power
Intensity

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Intensity equation

Power/Area

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Wavelength equation

Propagation Speed/Frequency

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Soft tissue / wavelength equation

1.54 mm / Frequency

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Speed equation

Frequency x wavelength

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The speed in Air is

330 m/s

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The speed in lung is

500 m/s

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The speed in fat is

1450 m/s

The speed in Soft tissue/ Blood is

1540 m/s

The speed in tendon is ...

1850 m/s

The speed of bone is

3500 m/s

Start of a pulse to the end of that pulse Not changed by soon Usec Determined by - source

Pulse duration

Start of pulse to start of next pulse (on & off time) Changed by sono M/sec Determined by source

PRP

of cycles per second Changed by sono 1/sec Hz Determined by source

PRF

% or fraction of time system transmits Changed by sono No units Determined by source

Duty Factor

length / distance a pulse occupies Not changed by sono mm/ cm Determined by source & Medim

SPL

These parameters are changed by depth of view ..

PRP, PRF, Duty factor

PRP and imaging depth are related how

Direct

PRF & Imaging depth are related how

Inverse

Duty Factor & imaging depth are related how

Inverse

PRP & PRF are related how

Inverse

PRF & duty factor are related how

Direct proportional

- Listening time (increase) - PRP (increase) - PRF (decrease) - Duty Factor (decrease)

Deep imaging

- Listening time (decreases) - PRP (decreases) - PRF (increases) - Duty factor (increases)

Shallow imaging

Equation for pulse duration

of cycles x period

Equation 2 for PD

of cycles in a pulse / frequency

SPL equation

of cycles x wavelength

Duty factor equation

Pulse duration/ PRP x 100

Largest value intensity

SPTP

Smallest value intensity

SATA

related to bio effects intensity

SPTA

beam coefficient uniformity

SP/SA

largest to smallest order of intensities

SPTP > Im > SPPA > SPTA > SATA

Which of the following intensities change with maximum imaging depth ?

SPTA or SATA

Decrease of intensity, power & amplitude as wave travels through body unrelated to propagation speed

Attentuation

Longer distance , higher frequency

More attenuation

Short distance, lower frequency

Less attenuation

Water has what type of attenuation

Extremely low

Blood,urine,biologic fluids has what type of attenuation

Low

Fat have what type of attenuation

Low

Soft tissue has what type of attenuation

Intermediate

Muscle has what type of attenuation

Higher

Bone & lung have what type of attenuation

Even higher

Air has what type of attenuation

Extremely high

High frequency sound, and medium with high attenuation

Thin half value

Low frequency sound, Media with low attenuation

Thick half value

Depends on these two factors & is directly related to them 1. Frequency 2. Distance of a wave (path length)

Attenuation in ST

What components contribute to attenuation

1. absorption 2. reflection 3. scattering

Sound energy converts to heat

Absorption

Strikes a boundary & returns to the transducer

Reflection

Specular reflection

smooth reflector

Diffuse/backscatter

rough & disorganized , random

Boundary of media are irregular & redirected in all directions

Scattering

uniformly, omni direction, example red blood cell

Rayleigh scattering

Attenuation coefficient equation

Frequency / 2

Soft tissue attuen equation

0.5 dB / frequency

Total attenuation equation

Attenuation coefficient x distance

1. Normal incident 2. Different Impedance What occurs?

Reflection

1. Oblique incidence 2. Different prop speeds What occurs?

Refraction

Transmitted & reflected intensity = ?

Incident intensity

This law deals w/ refraction

Snells law

If speed 2 = Speed 1

No refraction, transmission angle = incident angle

If speed 2 is greater than speed 1

Transmission angle greater than incident angle

If speed 2 is less than speed 2

Transmission angle is less than incident angle