Ultrasound 1 Flashcards
Learning outcomes
Understand the physics of ultrasound.
Understand the basics of an ultrasound scanner including the different types of transducers.
Understand the different modes of scanning used in clinical practice.
What range can humans hear in hertz?
20 to 20000 hertz
What hertz does ultrasound start?
Over 20000 hertz
How does ultrasound work?
Ultrasound uses short pulses that are transmitted into the body. The probe shoots the sound into the body. It listens for the echo or return of the sound. The transducer takes in the reflected, refracted and absorbed sound to create an image.
What are the advantaged and disadvantaged of ultrasound?
Advantages
Ultrasound is safe
No ionizing radiation
The equipment is portable, compact and cheap
Disadvantages
Operator dependent
Structures surrounded by bone like the brain and spinal cord, do not give good images
Not very good for structures in the lung or abdominal organs obscured by gas in the overlying bowel
What are piezoelectric crystals?
Ceramic crystals that deform and vibrate when electronically stimulated which generate sound pulses. When the echoes return to the transducer, it distorts the crystals again to create an image
What are the types of transducers?
Linear array probe
Curved array probe
Phased array probe
Describe the linear array probe
High frequency probe that is linear with a narrow field of vision. Doesn’t distort images. High resolution pictures but superficial imaging only
Describe the curved array probe
Curved convex probe with an extended field of view. Low frequency, picture isn’t as clear and is distorted. Good for deep tissue scanning
Describe the phased array probe
Thin probe that has a medium fov moves in a sweeping motion. Low frequency but can scan deep in tissue (scan through the ribs) because of its small probe or footprint.
What are the modes of imaging?
A-mode imaging: Displaying echos into a 1 dimensional on a graph like image where depth is one axis and the other axis is the location laterally
B-mode imaging: A the spike of the echo is converted into a dot and the brightness of the dot represents the amplitude of the returning signal
M-mode imaging: Brings down a line to the desired tissue to be examined and uses dopplers to be converted into a graph to show movement
3-D imaging: Many 2D cross sections to create 3-D imaging
What is echogenicity and what are the four types of it?
Echogenicity is the ability to bounce an echo, e.g. return the signal in ultrasound examinations.
Anechoic: Black, very low density, nothing or fluids
Hyperechoic: White, very dense tissue, usually bones
Hypoechoic: Gray, between black and white, moderate density
Isoechoic: Same colour all together, structure examined has same density between other surrounding structures
What does the gain and frequency do?
Gain controls the amplification of the returning acoustic signals. Frequency shows the wanted frequency range for imaging or prioritizing depth or image resolution.
What are the 4 probe maneuvers?
PART
Pressure Alignment Rotation Tilt
