Pulse-echo Instrumentation - Week 2

A comprehensive set of practice flashcards covering display modes, real-time imaging, frame rate, system components, processing, recording/archiving, and artifacts from the Week 2 Sono2580 notes.

In ultrasound, what does A-mode display plot on the X-axis and Y-axis?

X-axis shows depth; Y-axis shows amplitude (no Z-axis).

In ultrasound, what is plotted along the X-axis in B-mode and how is amplitude represented?

X-axis shows depth; amplitude is represented by brightness (Z-axis), with the Y-axis unused.

What does M-mode display show and how are axes defined?

X-axis is time; Y-axis is depth; it shows reflector location as it changes over time.

What is Real-time imaging in ultrasound?

The production and display of a motion-picture-like sequence, with frames displayed rapidly to depict ongoing events.

What does 'duplex' imaging mean in ultrasound?

A machine that displays real-time imaging together with Doppler simultaneously.

What is frame rate in ultrasound and what does it affect?

The number of frames displayed per second; it directly affects temporal resolution.

What is Tframe and how is it related to frame rate?

Tframe is the time for one frame; frame rate = 1 / Tframe.

List factors that determine frame rate in ultrasound.

Sound speed in tissue, imaging depth, number of pulses per frame (multi-focus), sector size, and line density.

How are frame rate and depth related?

Frame rate is inversely related to imaging depth (deeper imaging lowers frame rate); Tframe × frame rate = 1.

What does PRP stand for and how is it related to PRF?

PRP = Pulse Repetition Period; PRF is the reciprocal of PRP (PRF = 1/PRP).

What do PRF and PRP determine in ultrasound imaging?

The maximum imaging depth (depth of view) and the frame rate; shallower imaging allows higher PRF/shorter PRP, deeper imaging lowers them.

What is the Pulser and what does it control during transmission?

The Pulser generates electrical signals to excite the PZT crystals; it controls amplitude, PRP, and PRF during transmission.

What is Signal-to-Noise Ratio (SNR) and how can it be improved?

SNR is the ratio of meaningful signal to noise; increasing transducer output power increases SNR (noise levels stay constant).

What are the main functions of the Beam Former?

Creates and distributes delay patterns for the array during transmission, applies apodization, establishes receive delays for dynamic focusing, controls dynamic aperture, and serves as transmit/receive switch to protect the receiver.

What are the receiver functions in order of operation?

Amplification, Compensation, Compression, Demodulation, Reject.

What is preprocessing vs. postprocessing in ultrasound imaging?

Preprocessing occurs before storage and permanently changes the image; postprocessing occurs after storage and can be reversed.

Give examples of preprocessing operations.

Time-Gain Compensation (TGC), log compression, black/white inversion, frame averaging, write magnification.

Give examples of postprocessing operations.

Read magnification, edge enhancement, fill-in interpolation, contrast variation, smoothing.

What is PACS and what are its major advantages?

Picture Archiving and Communications System; advantages include instant access to archived studies, no data degradation over time, and store-and-forward telemedicine.

What is Magneto-Optical (M-O) storage and why is it used with PACS?

A storage method that stores large data on a single disc and cannot be erased by magnetic fields; provides high security for medical imaging data.

What is an artifact in ultrasound imaging?

An error in imaging; artifacts can be not real, not seen, not in correct size/shape/position/brightness, caused by assumptions violations, equipment issues, physics, or operator error.

What are the six core assumptions of ultrasound imaging?

1) Sound travels in a straight line. 2) Sound travels directly to a reflector and back. 3) Sound travels in soft tissue at ~1,540 m/s. 4) Reflections arise only from structures in the beam’s main axis. 5) The imaging plane is very thin. 6) Reflection strength relates to tissue characteristics.

Name some common artifact types and their general appearances.

Shadowing, enhancement, comet tail/ring down, reverberations, mirror image, refraction, side lobe, grating lobe; artifacts may be deeper than anatomy or displaced from true location.

What is shadowing by refraction?

An artifact caused by bending of the beam at interfaces, leading to dark regions not corresponding to true anatomy; different from standard shadowing.