Ultrasound

Question 1

Tell me the principles of how an image is formed on U/S

Answer 1

electrical impulses sent to transducer (probe) vibrate piezoelectric crystals in the probe, which send out high frequency sound waves. these sound waves go into the tissues. the sound waves are reflected back to the probe when they encounter differences in tissue density or a reflector surface (echo). the crystals pick up these sound waves and vibrate, sending back an electric signal.

Question 2

what is attenuation?

Answer 2

progressive weakening of sound waves as they pass through tissues (lower quality the further through the tissues)

Question 3

what is acoustic impedance?

Answer 3

resistance of tissues to propagation of sound waves (bone has high impedance

Question 4

what is reflection? what direction are they?

Answer 4

proportion of waves that return to the transducer; perpendicular

occurs when there’s a change in acoustic impedance

(most with bone and air)

Question 5

what is refraction? what direction are they?

Answer 5

bending of sound waves around interface; not perpendicular

causes shadows to appear under curved structures

Question 6

what is scatter?

Answer 6

when sound waves encounter an irregular surface

Question 7

what is absorption?

Answer 7

tissues capturing energy of waves

most with fluid

Question 8

what are the common U/S artifacts?

Answer 8

• specular reflector
• non-specular reflector
• shadow
• enhancement
• reverberation
• beam width artifact
• electrical interference

Question 9

what is a specular reflector?

Answer 9

parallel white line produced when beam strikes a smooth interface wider than beam

picture: diaphragm is acting as a specular reflector

Question 10

what is a non-specular reflector?

Answer 10

white line when interface is irregular or narrower

Question 11

what is a shadow?

Answer 11

from blockage of bone, FB, gas, etc or deviation of beam

Question 12

what is enhancement?

Answer 12

bright echoes under a structure due to enhanced transmission through fluid

Question 13

what is reverberation?

Answer 13

series of parallel white lines equidistant due to echo bouncing between 2 strong interfaces

Question 14

what is beam width artifact?

Answer 14

fuzzy edges of large fluid-filled structures due to partial fill-in of a non echoic area with echodense artifact

Question 15

what is electrical interference?

Answer 15

caused by an external electrical source interring (ex. motor running)

Question 16

what do follicles look like on US? how are they measured?

Answer 16

black, round, fluid filled structures

(W+H)/2

Question 17

what is a cystic follicle? how can you tell the difference between a follicular cyst and a luteal cyst?

Answer 17

large follicule ≥25mm, no CL present (no ovulatory crown)
follicular = thin walled
luteal = thick walled

Question 18

what does a CL look like?
When can you detect it on US?

Answer 18

black central cavity irregularly shaped filled with tissue

detectable 1-2 post-ovulation until next ovulation

Question 19

P4 levels are highly correlated to what in the bovine ovary?

Answer 19

area of lutenized tissue

Question 20

_____ regression of the CL occurs before _____ regression

Answer 20

functional, morphologic

Question 21

uterine coiling is most problematic when? and least problematic when?

Answer 21

most: diestrus
least: estrus

Question 22

tell me about the fluid in the uterus of a cow for US

what does it look like on US?

Answer 22

begins to increase 3-4 days pre-estrus, peaks during estrus, then declines 3 days post estrus

uterine edema = black on US

Question 23

tell me about cow pregnancy dx using US. like what’s happening on what day?

Answer 23

• 20d: embryo first detectable, surrounded by a small circular area of fluid
• 25d: embryo detectable at base of first uterine curl or between 2nd and 3rd curl; detection of chorioallantoic fluid
• 40d: fetal heartbeat = most reliable preg dx

Question 24

what is the difference between cows and horses in terms of what the early embryo does to alert the mother of its presence?

Answer 24

cow: elongates to fill horn and signal presence while fixed

horse: expands to become larger and actively migrates to signal presence

Question 25

tell me the difference b/t embryo death before and after 25 days?

Answer 25

<25d: caused by CL regression

> 25d: embryo death, but CL stays 5-30d
- fetal membranes not resorbed, but deteriorate and float (echogenic debris)
- when CL regresses, cervix opens and membranes are expelled

Question 26

what is the genital tubercle? what does it look like on US?

Answer 26

used to dx sex

echo dense, bilobed structure b/t rear legs at 45 d

Question 27

what can be used to determine sex on US? when? what happens for males and females?

Answer 27

genital tubercle (forms at 45d, can be used to determine sex at 53d until 100d)

female clitoris: GT migrates a short distance posterior, ventral to tail, looks like an = sign

male penis: GI migrates further posterior to umbilicus

Question 28

tell me what an normal male testicle looks like on US?

Answer 28

parenchyma: homogenous and mod echogeniticy; increase echogenicity with maturity

mediastinum: more echongenic line than parenchyma

epididymus: tail and plexus easy to ID, head and body not