what frequency waves are audible by human ear?
20Hz to 20kHz
what frequency sound waves to ultrasound use?
20kHz to 20MHz
the ability of certain materials to generate an electric charge in response to applied mechanical stress
piezoelectric effect: allows ultrasond to work
what are the four type of US probes? Uses?
Linear (6-13 MHz): superficial
Curvilinear (2-5 MHz): abdomen
Phased array (1-5 MHz): cardiac
Endoluminal (5-8 MHz): anal, vaginal, oral
High frequency =
low frequency =
describe the process of US
electrical signal-->crystal-->sound wave-->tissue-->sound wave returns-->crystal-->electrical signal-->picture
sound waves can be (4)
absorbed (bone), reflected (diaphragm, organs), scattered (air=bad), refracted
what is attenuation?
the gradual loss of intensity
water has an attentuation of 0 what does this mean?
the strenght of the singal does not change when passing through water
air has an attenuation of 12, what does this mean?
the signal is lost when passing through air
what are the modes of ultrasound
Pulse Wave Doppler
A mode (used in opto)
Anechoic, hyperchoic, hypochoic?
terms used with B mode US:
Anechoic: no echo produced, appear black, fluid (least dense)
Hypoechoic: some echo produced, appears gray, solid organs
Hyperechoic: alot of echo produced, appears white, dense solid strucutres bone (and air although it is white becuase it scatters)
power doppler. good for low flow vessels. gives intesnity of flow
color doppler. gives directionality of flow. red=coming towards, blue=going away
pulse wave doppler
M-mode "motion" can show breathing or heart tones