Module 2A - Units 1-3

Define elastography.

Quantifying and imaging the elastic properties of tissue and masses using U/S.

Elastography measures changes in the ______ of the tissue based on its ______ when a ______ is applied.

Strain, stiffness, stress.

List some tissue characterizations obtained from B-mode imaging.

Echotexture

Echogenicity

Size

Shape

List some tissue characteristics obtained from Doppler modalities.

Presence and direction of blood

Type of flow

Velocity

Name and describe the two techniques for applying stress to tissue for elastography.

Axial strain - hand compression on tissue

Shear wave - transverse waves applied to tissue

Elastography shows soft tissue displaces ______ when compression is applied, whereas stiff tissue displaces _____.

more, less

In elastography, RF data is used to…

Compare information from the same depth/location both pre and post compression.

Define strain.

Rate of displacement.

Why would a clinician prefer shear wave elastography over axial strain?

Shear wave gives a quantifiable value of stiffness.

Provide an example of when elastography would be used in cardiac sonography.

Speckle tracking (stain imaging) is used in GLS to assess myocardial mechanics.

EFOV is also called…

Panoramic imaging.

List some advantages to EFOV.

Directly visualize and image spatial relationships within the body

Accurately measure large structures and/or pathologies

Interpret images easily

What is the first model with EFOV technology?

Static B-scan.

Describe how current EFOV technology uses a transducer with a small FOV to create a large image.

Translation of the transducer along the same axis. The machine stitches the images together.

List and Describe the two techniques for EFOV.

1. EFOV generated in real time

2. Acquired frames in memory (Cineloop) are processed, then displayed as a panoramic image

Which EFOV technique is preferred by sonographers? Why?

Real time EFOV because there is less risk of error.

List 2 techniques for extending FOV.

Vector scan

EFOV (panoramic imaging)

Explain the two concepts used by the computer processing to accurately stitch the images together in EFOV.

Image registration - sequential order the frame is acquired

Feature matching - identification of common features in sequential frames that allow for overlap

List some limitations to EFOV.

Tissue motion (patient)

Off plane transducer rotation (sonographer)

List some limitations to imaging blood with Doppler.

Angle dependent

Long SPL → poor axial resolution

Booming and bleeding artifact

Aliasing

Decreased temporal resolution

Name 2 technologies for imaging blood.

Doppler modalities

B-flow imaging

List some advantages of B-flow imaging.

No aliasing

No blooming

Angle independent

Flow direction indicated

Tissue and B-flow displayed simultaneously

High axial and temporal resolution

Explain the physics concepts behind B-flow.

Extended BW resolution and high frame rate detects the Rayleigh scatter and displays the position and amplitude.

What modality is used in this image?

B-flow

List some clinical applications of B-flow imaging.

Blood vessel wall or plaque irregularities

Residual lumen from a stenosis measurement

Thyroid nodule activity assessment

Kidney perfusion

Vascular disease after transfemoral catheterization

Liver and spleen vasculature

Neonatal head vessels

Explain the computing process behind B-flow imaging.

Coded excitation - each pulse has a long PD and is composed of a code of mini pulses. The pattern of mini pulses is decrypted during processing to create the image.

Name the two factors the binary code is based on in B-flow imaging.

1. Timing of all the mini pulses

2. Amplitude of each mini pulse

Define deconvolution (also known as matched filtering).

Decoding binary code through mathematical analysis.

List some advantages to B-flow encoding the pulses.

↑PD → ↑signal intensity → ↑SNR → enhance visualization of weak reflectors

Post-professing filtering can suppress tissue echoes and enhance Rayleigh scatter → blood appears brighter than tissue