Chapter 4: Pulsed Ultrasound Practice Flashcards

Exactly 50 vocabulary flashcards based on lecture notes covering pulsed ultrasound parameters, depth relationships, and sound wave characteristics.

Pulsed Ultrasound

A collection of cycles traveling together.

Continuous sound waves

Waves that do not generate anatomical images.

Pulsed sound waves

Waves that generate anatomical images of the tissue boundaries.

Shades of grey (grey scale)

Pulsed sound returning from the body creates 2D, B mode images.

Time of flight

The go return time used to determine reflector distance from the transducer.

Pulse duration (PD)

The time from the start of a pulse to the end of that pulse.

PD Units

$\mu S$ (microseconds).

PD Range

$0.1\,\mu S - 1.5\,\mu S$.

PD Determination

Determined by the sound source only.

PD Formula (Cycles)

$PD = n \times T$, where $n$ is the number of cycles (1-3) and $T$ is the period.

PD and Period Relationship

Directly related.

PD and Number of Cycles Relationship

Directly related.

PD and Frequency Relationship

Inversely related.

PD and Image Quality

Pulse duration is inversely related to image quality.

Spatial pulse length (SPL)

The distance from the beginning of the sound pulse to the end of that pulse.

SPL Units

$mm$ (millimeters).

SPL Range

$0.1\,mm - 2.5\,mm$.

SPL Initial Determination

Initially determined by the sound source.

SPL Secondary Determination

Secondary determined by the medium.

LAART

Determined by the spatial pulse length.

SPL and Resolution

Shorter SPL results in better resolution.

SPL Formula

$SPL = n \times \lambda$ (number of cycles times wavelength).

SPL and Wavelength Relationship

Directly related.

SPL and Number of Cycles Relationship

Directly related.

SPL and PD Relationship

Directly related.

Pulse repition period (PRP)

The time from the beginning of one pulse to the beginning of the next, including the off time.

PRP Units

$ms$ (milliseconds).

PRP Range

$0.07\,ms - 0.25\,ms$.

PRP Determination

Determined by imaging depth.

Depth and Listening Time Relationship

Increased depth leads to increased listening time.

Depth and PRP Relationship

Directly related.

PD and PRP Relationship

Pulse duration does not directly affect PRP.

PRP and PRF Relationship

Inversely related and reciprocals.

PRP Formula

$PRP(ms) = \frac{1}{PRF(H2)}$.

Pulse repition frequency (PRF)

The number of pulses transmitted in each second.

PRF Units

$kHz$ (kilohertz).

PRF Range

$4\,kHz - 15\,kHz$.

PRF Determination

Determined by imaging depth.

Depth and PRF Relationship

Inversely related (increased depth yields fewer pulses per second).

PRF in Doppler Studies

The sonographer can change the PRF directly using the velocity scale function without changing depth.

PRF and Scan Lines Example

$PRF = 5\,kHz = 5000$ pulses per second, which creates $5000$ scan lines per frame.

Duty factor (DF)

The fraction of time that pulsed ultrasound is transmitted (ON).

DF Units

Unitless, expressed in decimals or percentages.

DF Formula (using PRP)

$DF = \frac{PD}{PRP}$.

DF Formula (using PRF)

$DF = PD \times PRF$.

DF and PRP Relationship

Inversely related.

DF and PD Relationship

Directly related.

DF and PRF Relationship

Directly related.

Shallow Imaging Characteristics

Decreased depth, decreased PRP (off time only), and increased PRF and DF.

Deep Imaging Characteristics

Increased depth, increased PRP (off time only), and decreased PRF and DF.