Module 3: Particle Motion & Wave Propagation

Flashcards covering essential vocabulary from the DMS Physics 1 lecture notes on Particle Motion & Wave Propagation, focusing on ultrasound imaging principles.

Sonographer's Role (Operator Control)

Deciding which preset and transducer to use based on requisition and patient history, using safe practices, and correctly labeling images and measurements.

Transducer Activation (Sending)

An electrical current is converted into sound via the reverse piezoelectric effect.

Sound Interaction

Sound waves travel through tissue and produce echoes that return to the transducer.

Transducer Activation (Receiving)

Returning sound waves are converted back to an electrical current by the piezoelectric effect.

Image Display (Ultrasound)

The electrical current is processed by the machine and converted into an image on a monitor.

Piezoelectric Effect

When pressure waves are applied to certain crystals, they produce electric pulses or a voltage.

Reverse Piezoelectric Effect

When electric pulses or voltage are applied to certain crystals, they produce sound waves.

Acoustic

Refers to sound.

Propagation

Refers to travel.

Acoustic Propagation

Refers to the effects tissue cause on sound.

Bioeffects

Refers to the effects of ultrasound on tissue.

Sound (Wave Definition)

A propagating variation (a wave) that carries energy, not matter, and requires a medium to travel.

Acoustic Variables

Qualities of waves that apply when sound travels through a medium, including Pressure, Density, Particle motion, and Temperature.

Pressure (Acoustic Variable)

Variations that can be expressed with a sine wave, where crests represent increased pressure and troughs are decreased pressure.

Density (Acoustic Variable)

The concentration of particles or mass per unit volume. Regions of low density are rarefactions, and regions of high density are compressions.

Rarefactions

Regions of low density in a sound wave.

Compressions

Regions of high density in a sound wave.

Temperature (Acoustic Variable)

Sound is energy and creates heat, important for attenuation and bioeffects.

Mechanical Wave

A type of wave, like sound, that requires a medium to travel and cannot travel through a vacuum.

Electromagnetic Waves

A type of wave, such as X-rays, that does not need a medium to travel.

Longitudinal Waves

Waves characterized by back and forth particle motion parallel to the direction of wave travel.

Transverse Waves

Waves characterized by particle motion perpendicular to the direction of wave travel.

Mode Conversion

The conversion of one type of wave to another form, e.g., longitudinal waves becoming transverse waves at a tissue-bone interface.

Frequency

A measurement of how often something happens; for sound, the number of complete variations an acoustic variable goes through in one second.

Hertz (Hz)

The unit for frequency, representing cycles per second.

Megahertz (MHz)

A unit of frequency representing millions of cycles per second, common in ultrasound.

Period (T)

The time it takes for one complete cycle to occur, measured in seconds or microseconds (\u00b5s) for ultrasound.

Microseconds (\u00b5s)

Millionths of seconds, used to measure period in ultrasound.

Wavelength (\u03bb)

The length of space one cycle takes up, commonly expressed in millimeters.

Propagation Speed (c)

The speed with which a wave moves through a medium; in soft tissue, the average speed is 1.54 mm/\u00b5s or 1540 m/sec.

Amplitude (Amp)

The maximum displacement of an acoustic variable, simple put, it is the strength of the wave determined by the source of sound.

Intensity (I)

The concentration of energy in a sound beam; it is directly related to the square of the amplitude (I \u221d Amp\u00b2) and to power (P) divided by area (a).

Power (of a wave)

The total energy transferred over the entire cross-sectional area of a wave.

Spatial Peak (SP)

The greatest intensity found across the beam, usually at the center.

Spatial Average (SA)

The average intensity measured over the entire beam.

Beam Uniformity Ratio (BUR)

The ratio of spatial peak (SP) to spatial average (SA), calculated as SP/SA.

Temporal Peak (TP)

The greatest intensity found within a pulse.

Pulse Average (PA)

The average intensity for all values found within a pulse; almost identical to temporal peak (TP).

Temporal Average (TA)

The average intensity that includes the dead time between pulses where there is no intensity.

Duty Factor (DF)

The ratio of temporal average (TA) to temporal peak (TP), calculated as TA/TP, indicating the percentage of time the transducer is actively transmitting sound.

SPTP (Spatial Peak Temporal Peak)

The highest intensity measurement in a sound beam.

SPTA (Spatial Peak Temporal Average)

The spatial peak intensity averaged over time, including listening phases; important for biological considerations.

SATA (Spatial Average Temporal Average)

The lowest intensity measurement, representing the spatial average intensity averaged over time.

Ultrasound Mode Intensities (SPTA)

From lowest to highest SPTA values are M mode, Real-time B Mode, Doppler, and Continuous wave.

Artifacts (Ultrasound)

Anything that appears on the screen that is not a real structure or accurately represented.

Propagation Speeds in Tissue

The actual velocities sound travels through different tissues, e.g., Lung (~600 m/s), Fat (~1460 m/s), Liver (~1555 m/s), Muscle (~1600 m/s), and Bone (~4080 m/s).

Range Equation

A formula used to calculate the distance of a reflector from the probe: D = C x t, where D is total go-return distance, C is average speed of sound in soft tissue, and t is the time for the round trip.