SON 111 Chapter 4: Pulsed Wave Ultrasound Vocabulary

Vocabulary flashcards covering core terms, concepts, and formulas from SON 111 Chapter 4 Pulsed Wave Ultrasound.

Pulsed Wave (PW) Ultrasound

An ultrasound modality that alternates between transmitting sound bursts and listening for returning echoes, providing range resolution and imaging capabilities.

Continuous Wave (CW) Ultrasound

An ultrasound modality that continuously transmits and receives sound using two separate crystals, incapable of producing anatomical images due to range ambiguity.

Range Ambiguity

The inability of a system to identify the start and end of an individual sound pulse to calculate round-trip time and echo depth, characteristic of continuous wave ultrasound.

Aliasing

An artifact in pulsed wave Doppler occurring when sampling at a finite pulse repetition frequency ($\text{PRF}$), which limits the maximum measurable velocity.

Damping

A material process that absorbs energy behind the crystal to reduce ringing, decrease cycles per pulse, shorten pulse duration and spatial pulse length, and improve axial resolution.

Wavelength ($\lambda$)

The length or distance of one cycle, calculated in soft tissue as $\lambda (\text{mm}) = \frac{1.54}{\text{frequency (MHz)}}$.

Spatial Pulse Length (SPL)

The physical distance that a pulse occupies in space, calculated as $\text{SPL} = \text{number of cycles} \times \lambda$.

Pulse Duration (PD)

The actual time from the start of a pulse to the end of that pulse, calculated as $\text{PD} = \text{number of cycles} \times \text{period}$.

Period

The time required to complete one single cycle, calculated as $\text{period} = \frac{1}{\text{frequency}}$.

Pulse Repetition Period (PRP)

The time from the start of one pulse to the start of the next pulse, calculated as $\text{PRP} = \text{PD} + \text{listening time}$.

Pulse Repetition Frequency (PRF)

The number of pulses transmitted by the system into the body per second, calculated as $\text{PRF} = \frac{1}{\text{PRP}}$.

Duty Factor (DF)

The percentage of time that sound is actively being transmitted, calculated as $\text{DF} = \frac{\text{PD}}{\text{PRP}} \times 100\%$.

Axial Resolution

The ability of an ultrasound system to display two reflectors as separate structures along the beam axis, calculated as $\text{axial resolution} = \frac{\text{SPL}}{2}$.

Acoustic Line Time (ALT)

The time required for round-trip sound travel per line in soft tissue, approximated as $\text{ALT} \approx 13\,\mu\text{s/cm} \times \text{depth (cm)}$.

Frame Time (FT)

The total time required to create a single complete image frame, calculated as $\text{FT} = \text{ALT} \times \text{number of lines}$.

Frame Rate (FR)

The number of complete image frames created per second, calculated as $\text{FR} = \frac{1}{\text{FT}}$.

Color Frame Time (CFT)

The time required for color image acquisition, calculated as $\text{CFT} = \text{ALT} \times \text{color lines} \times \text{packet size}$.

Scanline

A single acoustic line formed by a transmitted sound pulse.

Frame

The complete ultrasound image made from all individual scanlines.

Packet Size

The number of pulses (also known as ensemble size) transmitted along a color display line to estimate blood flow.