Lesson 5 Flashcards
Ultrasound
mechanical wave
compressions and refractions
longt.
need medium to propagate
above our hearing range - ultrasound
use today 1 to 15 mhz. Why there is this range?
pizoelectric crystals- contract or expand depending on voltage applied.
matches freq and current.
same material to send, recieve etc
z= acoustic impedance. Differs for each material.
use gel because….
UNDERSTAND INVERSE SQUARE LAW. and attenuation. further away from source- intensity increases
MIDTERM
ultrasonography in: depth of sea (boats)
Q: speed of ultraspund in water is 1500 m/s
task is : find how deep our sea if we recieve signal in 2s
= 1500
(sound travels front and back)!!!
WE ONLY WANT FRONT
doppler shift = calculate speed of moving car (camera uses)
dopplergography- cheap non invasive method to find stenosis.
average of distolic and sistolic
MIDTERM questions: bernoullis principle to remember!
Low velocity = pressure to the size of blood pressure is high
high veloxity = pressure is low
Poiseuilles law in midterm!!
Relationship between flow rate and radius of blood vessels
flow rate= volume of blood going thrpough eg blood per (timereferance)
directly proportional to radius to power of 4.
1 cm radius
reduced radius by 1/2 (close artery to 0,5 cm)
how many times will flow rate drop?
(1/2)^4 = 16!
REMEMBER THIS RELATIONSHIP
