DSON 5018: SIP Formulas

Decibel notation for intensity

Used for power values:

• acoustic power: measured in W

• intensity: measured in W/cm²

Decibel notation for amplitude

Used for amplitude values:

• voltage: V, mV

• Wave amplitude: pressure (Pa) or displacement (m)

Intensity

Wavelength

Acoustic impedance

also units in rayles

Intensity reflection coefficient

multiply by 100 to get the percentage of signal that is bounced back to the transducer, rest gets carried through

Snell’s Law of Refraction

Attenuation

Transducer frequency from crystal thickness

F₀= operating frequency

Quality factor

Range equation

T= time for pulse to travel to interface and echo back to transducer

D= distance of interface from transducer (x2 to account for there and back)

V= speed of sound, 1540 m/s always assumed

Beam width equation

Near field

• Can only change frequency (diameter set by manufac.)

  • but if diameter of crystal increases → also increases NFL

• Increase frequency —> decreases wavelength —> increases NFL

Far field

• Can only change frequency (diameter set by manufac.)

  • but if diameter of crystal increases → also decreases divergence angle

• Increase frequency —> decreases wavelength —> decreases divergence angle (higher resolution)

Axial resolution and Spatial pulse length

Determine number of discrete pieces of information a computer can display for each parameter

Pulse repetition frequency

Scan line density

Power

P is proportional to A²

P is proportional to I

Period

1/f

Doppler equation

Simplified formula for scanning: v= (fd)/(cosθ)

Doppler frequency

Signal intensity is proportional to…

Cosine angle charge and notes

Flow (Q)

Flow (mL) = cross-sectional area x velocity time interval

Q= CSA x VTI.

Poiseuille’s Law

Flow through the arterial system is:
Q= ΔP/ R

R= resistance to flow

Duty Factor