Ch 1. Fundamentals of Diagnostic Ultrasound Flashcards
What is the assumed average velocity of diagnostic ultrasound?
1540m/sec
The distance between a band of compression or rarefaction is the sounds what?
Wavelength
The number of times a wavelength is repeated per second is what?
Frequency
What is the average velocity of sound traveling through fatty tissue?
1450 m/s
What is the average velocity of sound traveling through gas?
331 m/s
What is the average velocity of sound traveling through bone?
4080 m/s
Higher frequency probes will affect wavelength how?
Higher frequency shortens the wavelength
The product of a tissue’s density and sound velocity within the tissue is known as what?
Acoustic impedance
Acoustic impedance is equal to what times what (formula)
Acoustic impedance (Z) = velocity (v) x tissue density (p)
For the following frequencies what are their respective wavelength values? 2.0 3.0 5.0 7.5 10
Frequency (MHz) Wavelength (mm)
2.0 0.77
3.0 0.51
5.0 0.31
7.5 0.21
10 0.15
Pulse length, frequency of the transducer that determines the ability to separate points along the axis. This is termed what?
Axial resolution
Pulse repetition frequencies (PRF’s) of less than what (range) is needed for diagnostic ultrasound?
1 kHz - 10kHz
Calculate the Interface distance when velocity = 1540 m/s (1.54 microsec), and round-trip time (RT) is 65microsec.
Interface distance = V (1.54 micro/s) x RT (65 micro/sec) / 2
50 mm.
Time gain compensation controls are used to produce an image that is balanced in brightness from near to far field
YAY A GIMME!
A-mode ultrasound is great for figuring out what value?
Amplitude, great for ophthalmic examinations
This refers to the ability to resolve adjacent points perpendicular to the ultrasound beam axis along the scan plane
Lateral resolution
Harmonic mode imaging may be particularly useful for scanning what organ?
Urinary bladder
Spatial compounding in short does what?
Increases image quality by reducing the effect of speckle. Improves image contrast.
An ultrasound artifact produced when minor beams travel off axis to the primary beam and interact with a reflective surface
Secondary lobe artifact or side lobe artifact
Which artifact is produced when a portion of the beam is inside and outside an anechoic structure and can often appear as pseudo sludge in the urinary or gall bladder?
Slice thickness artifact
An artifact produced when the ultrasound beam repeatedly bounces between two highly reflective surfaces or between the transducer and a strong reflector (gas or metal)?
Reverberation artifact
The diffuse echoes between reverberation are known as what artifact?
Ring down artifacts
What artifact is often seen when there is a large difference between acoustic impedances? Often seen with metal, foreign objects or a needle (aspiration)
Comet-tail artifact
An artifact when the ultrasound beam encounters reflective surfaces and the echoes are interpreted in a straight line , often encountered at the lung/diaphragm interface
Mirror Image Artifact
An artifact produced when the sound wave goes through tissues of different impedances and the sound wave changes directions, often causing organ duplication
Refraction artifact
Artifact when two tissues in the near field to an organ have different propagation velocities and causes irregular borders to that organ.
Speed propagation artifact.
Artifact when the ultrasound beam is entirely reflected or absorbed from either bone or metal.
Acoustic shadowing
The shift in sound frequency as sound waves are reflected from moving targets, usually blood cells?
Doppler effect
If motion is toward the transducer, the frequency of returning echoes is higher than that of the transmitted sound. This is what kind of shift?
Positive shift
If the motion is away from the transducer, the frequency of returning echoes is lower than the transmitted sound. This is what kind of shift?
Negative shift
