SPI RESOLUTIONS AND EQUATIONS

What I axial resolution determined by?

SPL (spatial pulse length)

What is lateral resolution determined by?

Width of the sound beam

• Narrower sound beams have better resolution

What is temporal resolution determined by?

Frame rate

• Higher frame = better resolution

• Lower frame = poorer resolution

What are the other names for axial resolution?

• Longitudinal

• Axial

• Range

• Radial

• Depth

What are other names for lateral resolution?

• Lateral

• Angular

• Transverse

• Azimuthal

What is the equation for pulse duration?

• Pulse duration (µs) = # of cycles x period (µs)

• Pulse duration (µs) = # of cycles/frequency (MHz)

What is the formula for frequency?

Cycles per second (Hz) = 1/period (s)

What is the formula for intensity?

Intensity (W/m²) = Power (W) / Area (m²)

What iss the formula for wavelength?

Wavelength (mm) = 1.54 (mm/microseconds) / Frequency (MHz)

What is the formula for propagation speed?

Propagation Speed (m/s) = Wavelength (m) × Frequency (Hz)

What is the formula for spatial pulse length?

Spatial Pulse Length (mm) = Number of Cycles × Wavelength (mm)

What is the formula for duty factor?

Duty Factor (%) = Pulse Duration / PRP x 100

What is the formula for total attenuation?

Total Attenuation (dB) = Attenuation Coefficient (dB/cm) × Distance (cm)

What is the formula for attenuation coefficient?

• Attenuation Coefficient (dB/cm) = frequency (MHz)/2

• Atten. coef. = 0.5 (dB/cm)/MHz

What is the formula for impedance?

Impedance (rayls) = Density (kg/m3) x propagation speed (m/s)

What is the formula for the Intensity transmitted coefficient?

Intensity Transmitted Coefficient (ITC) (%) = Intensity Transmitted / Incident Intensity x 100 = 1 intensity reflection coefficient

What is the formula for Incident intensity?

• Incident intensity= reflected intensity + transmitted intensity

• Coefficients are reported as percentages: (100% = reflected coefficient + transmitted coefficient)

What is the range equation for depth?

Depth (mm) = 1.54mm/ µs x go-return time (µs)/2

What is the range equation for PRP?

PRP (µs) = Imaging depth (cm) x 13 µs/cm

What is the range equation for PFR

PFR (Hz) = 77,000 cm/s / Imaging depth (cm)

What is the formula for axial resolution in soft tissue?

Axial resolution (mm) = 0.77 mm x the # of cycles in a pulse/frequency (MHz)

What is the formula for quality factor?

Quality factor = main frequency/bandwidth

What is the formula for T frame?

T frame = # pulses x T frame x frame rate =1

What is the formula of growth for Decibels

• +3 dB = double

• +10 dB = 10x larger

• Intensity increases 10 fold - 3 dB = half

• Intensity ½ its value -10 dB = one tenth or Intensity 1/10 its value

What is the formula for rayleigh scattering and frequency

• Rayleigh scattering = frequency⁴

• Directly related to the fourth power of frequency, meaning scattered intensity increases as the frequency increases.