Physics - Ch. 8 Is it performing well?

Imaging performance is determined by measuring primarily the following:

Detail resolution

Contrast resolution

Penetration and dynamic range

Time gain compensation operation

Accuracy of depth and distance measurement

Tissue-Equivalent Phantoms

simulate tissue properties

Tissue-Equivalent Phantoms allow assessment of:

Detail resolution

Contrast resolution

Penetration

Dynamic range

Time gain compensation

Tissue-Equivalent Phantoms typically contain:

echo free regions and thin nylon lines (to measure detail resolution and distance accuracy)

Axial other terms:

depth, longitudinal, radial

Lateral other terms:

Beamwidth, azimuthal, side-by-side, transverse, angular

In round crystals, beamwidth is ________________ in both planes

symmetric

Axial Resolution other terms

range resolution

Shorter pulse duration, ____________ (better/worse) axial resolution.

better

To resolve 2 objects the distance between them must be at least half of the ______.

SPL

AR = SPL / 2

What is the backing layer made of?

Powdered tungsten with epoxy resin

Does the backing material absorb any of the ring energy?

yes some

__________ (Higher/lower) frequencies form narrower beams.

Higher

What are test objects made of?

nylon lines and scattering layers

Do test objects simulate tissue characteristics?

no

What do test objects evaluate for?

detail resolution, beam profiles

penetration of Doppler beam

ability to discriminate between different flow directions

accuracy of sample volume location

accuracy of measured flow speed

What are Doppler test objects made of?

use a moving solid object like string

can produce pulsatile and reverse motions

Doppler Phantoms

use a flowing blood-mimicking liquid

Doppler Phantoms disadvantages:

presence of bubbles, non uniform flow

Doppler Phantoms advantages:

can simulate clinical conditions (tissue attenuation)

Hydrophone

used to measure the acoustic output of sonographic instruments

Hydrophone measures...

pressure, amplitude and period - from which several other acoustic pulse parameters can be calculated

Small Transducer Hydrophone

mounted on the end of a hollow needle

Large Piezoelectric Membrane Hydrophone

membrane with small metallic electrodes centered on both sides