Ultrasound Principles and Techniques: Perioperative uses Flashcards
What is amplitude, when it comes to ultrasound?*
Amplitude: The strength of the sound beam. The difference between the maximum value and the average. *******
Please note: amplitude is not the difference between the maximum and minimum values of the wave. **
What is attenuation?
Attenuation-* loss of sound energy* (interruption) when the wave travels through tissue due to absorption, reflection and scattering of sound energy
What is Echogenicity?
Echogenicity- degree of brightness displayed in an ultrasound image. Influenced by the amount of beam returning to the transducer (reflected) after it encounters a target structure.
What is the Doppler effect?
Doppler effect-a change in the frequency of sound as a result of motion between a sound source and the receiver (target). It is said to be positive when receiver is moving towards the source and negative when moving away
What is Wavelength?
Wavelength-distance between 2 consecutive peaks or 2 troughs of a wave**
The higher the frequency of the beam the more resolution the image will have but the (BLANK) into tissue will be less*
The higher the frequency of the beam the more resolution the image will have but the (PENETRATION) into tissue will be less
The lower the frequency the less resolution but the tissue penetration will be (BLANK).*
The lower the frequency the less resolution but the tissue penetration will be (INCREASED).
Images that are bright on the screen indicate (BLANK) tissues, more opaque images indicate (BLANK) tissue.*
Images that are bright on the screen indicate (HYPERECHOIC) tissues, more opaque images indicate (HYPOECHOIC) tissue.
The reason that frequency and tissue penetration are (BLANK) proportional is that velocity through a medium is constant and
V= frequency (f) X wavelength (λ)
The reason that frequency and tissue penetration are (INVERSELY) proportional is that velocity through a medium is constant and
V= frequency (f) X wavelength (λ)
If frequency increases or decreases the wavelength must increase or decrease in (which) direction to maintain the constant velocity**
If frequency increases or decreases the wavelength must increase or decrease in (THE OPPOSITE) direction to maintain the constant velocity
The FREQUENCY of the transducer
The HIGHER the frequency, the (BLANK) it can penetrate
The HIGHER the frequency, the LESS it can penetrate
The FREQUENCY of the transducer
The LOWER the frequency, the (BLANK) it can penetrate
The LOWER the frequency, the DEEPER it can penetrate
How do tendons appear on ultrasound?
On long axis view, how do they appear?
=Tendons appear also hyperechoic but the “streaks” appear longer than the nerves. This is due to the composition of the tendon’s outer layer.
=On long axis view they appear with internal hyperechoic lines.
Does the gain change the power output??
Gain controls
receiver gain only
does NOT change power output
Increase gain = brighter
Decrease gain = darker
What does blue and red indicate on the ultrasound?*
Doppler or color flow, this allows for the identification of blood vessels based on flow, red normally indicates flow towards the transducer and blue away from the transducer.*** Note that this does not refer to veins or arteries. It is based on flow.
