12/9/2014 Medical Physiology CC:Echocardiology Harold Smulyan Flashcards Preview

Unit 5 > 12/9/2014 Medical Physiology CC:Echocardiology Harold Smulyan > Flashcards

Flashcards in 12/9/2014 Medical Physiology CC:Echocardiology Harold Smulyan Deck (13):
1

Frequency

Pitch – in the audible range

2

Audible Sound

Humans – 15,000 to 20,000 Hz
Dogs – 40,000 Hz

3

Ultrasound

Over 20,000 Hz
*Travels in straight lines

4

Velocity

• Independent of Frequency

• Dependent on the MEDIUM

5

Why are the lungs your deadly enemies when you are doing echocardiography?

Because they absorb the ultrasound and you can't see the heart

6

Ultrasound (propagated wave) ___ and ___ by an interface between two media of different acoustic impedance

reflected; refracted

7

T or F: Most of the sound in medical ultrasound gets refracted rather than reflected

True, that's why ultrasound images are not great

8

In ultrasound we are interested in:

distance and the time it takes to get back

d=(velocity)x(time)

9

Piezoelectric effect

Electricity resulting from pressure

10

Transducer probe

Probe that sends and receives the sound waves

11

How is the piezoelectric effect used in medical ultrasound?

1. Probe w/ one or more piezoelectric crystals

2. electric current applied to crystals

3. rapid shape changes or vibration of crystals produce sound waves that travel outward

4. when sound or pressure waves hit the crystals --> emission of electrical currents
* same crystals can be used to send and receive sound waves

12

Describe the Doppler effect in the context of its applicability in medical ultrasound

Target --> blood cells

1. target stationary
freq transmitted = freq received

2. target moving towards transducer
freq transmitted < freq received
*red

3. target moving away from transducer
freq transmitted > freq received
*blue

13

What are the different views of an ultrasound in 2D?

Parasternal Long Axis

Parasternal Short Axis
- aortic, tricuspid & pulmonic valve level
- mitral valve level
- mid-ventricular level
- apical level

Apical
- 4 or 2 chambers

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