(a)   is a method of describing the extent to which a signal can vary and still maintain accuracy

Number of available choices

(a)  

Weak signals are (a)   the signals threshold

Measure of the signal magnitude identified and managed by the system

(a)  

Dynamic Range (a)   - varies per component of the system.

Reported in decibels. It is a comparison, a relative measurement, or ratio between the smallest and largest signals

(a)  

Strong signals (a)   the system

The dynamic range of the information (a)   the more it is processed

100-150dB

(a)  

100-120dB

(a)  

40-50dB

(a)  

20-30dB

(a)  

10-30dB

(a)  

Largest and smallest remain the same –
Range is narrowed

(a)  

(a)   is a technique that reduces the dynamic range of a signal without introducing errors

The largest signal remains the largest

(a)  

The smallest signal remains the smallest

(a)  

The range of signals is reduced

(a)  

10:1

(a)  

100:1

(a)  

The best examples for these limitations and reductions of the dynamic range through the different components is the BRIGHTNESS LEVELS available on the (a)  

1000:1

(a)  

Fewer shades of gray
 Narrowest DR is the bistable.
 High contrast

(a)  

More shades of gray

Many choices

Low contrast

(a)  

• The original frequency of the transducer.

• Multiples of the fundamental frequency.

• Twice the original frequency.

• Non-linear

The creation of an image from sound reflections at twice the frequency of the transmitted sound

(a)  

(a)   are more effective, less distortion, and non-linear

The image created by processing reflections that have the same frequency as the transmitted sound

(a)  

The image created by processing reflections that are twice the fundamental frequency

(a)  

Harmonic imaging is most useful in improving poor quality imaging because harmonic frequency waves undergo (a)   distortion

• proportional

  symmetrical

(a)   systems respond in an even manner

• disproportionate, irregular, uneven

A system is (a)   when it behaves unevenly

Non linear behavior is (a)  

Harmonics frequency is produced by (a)   behavior.

As a subbed wave travels in the body, a minuscule amount of energy is converted from fundamental frequency to the harmonic frequency

(a)  

1. Harmonics are present in the (a)   aspect of the sound beam offset of the transducer surface.

Sound wave must propagate a short distance in the medium (a)   transfer of energy occurs from fundamental frequency to the harmonic frequency

Little pulse distortion occurs (a)   the transducer (region free of harmonics).

Tissue harmonic signals DO NOT EXIST at (a)   depths

Harmonics (a)   the signal-to-noise ratio

3. As the sound wave propagates in the medium, harmonics (a)   , and the fundamental frequency becomes more attenuated and distorted (becomes more linear and stops transferring energy to the harmonics).

Weak sound beams (a)   create tissue harmonics

Beams that are most likely to create harmonics are (a)   likely to create artifacts

4.   Then, harmonics start to be (a)   in the medium.

Filters has been replaced by ___ ___ Harmonics.

(a)  

(a)   is an imaging technique specifically designed to utilize harmonic reflections, which are distortion free, while eliminating distorted fundamental reflections

(a)   separate the harmonics from the fundamental frequencies more successfully

With pulse inversion harmonics, (a)   consecutive ultrasound pulses are transmitted down each scan line

Harmonic portions of the reflection are (a)   and interfere constructively, while fundamental signals to the opposite

One advantage of (a)   is that it creates an image with less distortion

One disadvantage of (a)   is that two pulses are transmitted down each scan line and twice the number of pulses are required to create each image. This reduces temporal resolution

(a)   an imaging technique specifically designed to augment harmonic reflections, which contain less distortion, while eliminating distorted fundamental reflections

• Since clutter, grating lobes, and side lobe artifacts are produced by the (a)   . HARMONICS eliminate these artifacts

• Reverberation artifacts are reduced

• Low echo amplitudes do not generate harmonics

• Distortion and scattering depend on the fundamental frequency; then, they are avoided when using harmonics

• Reduction of acoustic noise

• Detection of low-contrast solid lesions is improved

• Acoustic enhancements and shadowing are more easily demonstrated

• Liquid cavities show less filling echoes

• High acoustic pressure occur near the main beam axis and within the focal zone.

• This is the source of harmonics production.

• Then, width of harmonic sound beam is narrower than the width of the fundamental frequency sound beam  improves lateral resolution

Less overall penetration because of higher attenuation for harmonics

(a)  

Contrast agents, also called (a)   , are gas bubbles encapsulated into a shell

• Ingested or Injected (IV)

• Contrast agents create (a)   reflectors

• Contrast agents (a)   chambers, cavities, vessels, etc

• Safe

• Inert

• Long lasting

• Small than capillaries.

(a)   is produced by the non-linear behavior of micro bubbles when they are stroked by the sound beam

Bubble fluctuates size (a)   the sound beam. Resonance

bubble shrinks and pressure within increases

(a)  

bubble expands and pressure within decreases

(a)  

• It is the amount of contrast harmonics produced

(a)   depends on the frequency of the transmitted sound and the rarefaction pressure of the sound wave

• Fundamental frequency and the pressure of the sound wave

• MI (a)   with lower frequencies and high pressure variations

• MI (a)   with higher frequencies and low pressure variations

Low mechanical index sound beams (a)   create harmonics because the micro bubbles expand and contract evenly in a linear fashion

• - outer shell

• - gas within bubble