Put the Probe Here

Question 1

The human ear can pick up frequencies up to _______ Ultrasound machines can produce sound waves with frequencies of ____ to ______

Answer 1

20 kHz 1.5 MHz to 7.5 MHz

Question 2

In Ultrasound, when the sound wave is emitted by the piezoelectric crystals and reflected back by the material being scanned, what 2 things are being measured and what do they tell the computer?

Answer 2

1. The time between the signal impulse and its return : indicates how deeps the structure is. 2. The intensity of the signal: indicates how dense the structure is.

Question 3

How do piezoelectric crystals work?

Answer 3

They transform electrical oscillations (varying voltages in the electrical current) into mechanical oscillations, which are essentially sound waves. They send out sound waves and receive those that get reflected back, and turn them into electrical impulses.

Question 4

What causes ultrasound waves to be reflected back to the probe?

Answer 4

Moving between the interfaces of two different media.

Question 5

In Pulse Wave Doppler, one transducer crystal sends out a signal at a fixed time interval called the __________.

Answer 5

Pulse Repetition Frequency.

Question 6

The main advantage of Pulse Wave Doppler as compared to Continuous Wave Doppler is: _______. The main disadvantage is: _________.

Answer 6

Advantage: It can measure the doppler shift (velocities) at a specifc point that is set by the echocardiographer, called the sample volume.

Disadvantage: Since PW doppler uses a single crystal to send and receive signals, there is a maximum frequency to the signals that can be sent out (called the “pulse repetition frequency”). Therefore, PW has a maximum velocity that it can reliably measure before it is subject to aliasing.

Question 7

Define Nyquist Frequency.

Answer 7

• The maximum Doppler shift (or velocity) you can measure with Pulse Wave Doppler.
• Equals half the Pulse Repetition Frequency.
• Doppler shifts above the Nyquist frequency undergo aliasing.

Question 8

What happens with aliasing?

Answer 8

• Aliasing happens when a velocity (or, doppler shift) being measured by Pulse Wave Doppler exceeds the Nyquist Frequency (half the Pulse Repetition Frequency).
• The result is that the doppler signal (aka velocity jet) appears to be going in the opposite direction.

Question 9

What is the main advantage and disadvantage with Continuous Wave Doppler?

Answer 9

Advantage: There is no maximum doppler shift that can be measured, and therefore no aliasing.

Disadvantage: It cannot measure jet velocities at a specific point, only the maximum velocity (doppler shift) along the path of the ultrasound wave.

Question 10

In Colour Doppler, velocities coming towards the probe are coded ____ (colour) and velocities moving away from the probe are coded ______.

Answer 10

Toward: Red

Away from: Blue

Tip: BART (Blue Away, Red Towards)

Question 11

Tissue Doppler, in general, is used to look at:

Answer 11

Ventricular relaxation and diastolic dysfunction.

Question 12

One advantage of M-mode over 2-D echo is ________ and it is especially useful when you want to do these two things:

Answer 12

Advantage: It has better resolution.

Especially useful when you want to measure wall thickness and measure things that move in the heart, especially valves.

Question 13

What’s the name of the equation you use to convert velocities into pressure, and how do you write it?

Answer 13

The simplified Bernoulli Equation:

Delta P = 4V²

Where P is the pressure difference (gradient) along the path you’re measuring.

Eg. you measure a jet velocity to be 2m/s. The pressure differential is 16.

Question 14

Explain how one uses TR jet velocity to measure PA systolic pressure.

Answer 14

Use the simplified Bernoulli equation to calculate the pressure differential between the RA and RV in systole. Now as long as there’s no pulmonic stenosis (which is rare unless it’s congenital), PA systolic pressure = RV systolic pressure. To determine RV systolic pressure, add the estimated RA pressure to the pressure differential you just calculated. You estimate RA pressure by measuring the IVC’s diameter and inspiratory collapse in the sub-costal view. Table:

Question 15

What pressures can be estimated with the following doppler velocities?

Peak TR velocity

Peak PR velocity

End-diastolic PR velocity

Peak MR velocity

End-diastolic AR velocity

Answer 15

Question 16

Pressure gradients accross valves, both peak and mean, are determined using this equation:

Answer 16

The simplified Bernoulli equation.

Question 17

How is the Continuity Equation written, and what does it mean?

What do we use this equation for in echo?

Answer 17

The Continuity Equation stipulates that the volume of blood flowing into a valve must equal the volume of blood flowing out of a valve.

Flow in = Flow out

aka:

A1 x V1 = A2 x V2

A = area, V = velocity

More accurate to use Velocity Time Integral (VTI) instead of Velocity (V) though

Question 18

When using the Continuity Equation to determine valve area, why do we trace velocity jets instead of just placing the cursor on the maximum velocity like for TR jet determination?

Answer 18

Because in a pulsatile system like the heart, flow velocities vary during an ejection period, starting off slow, speeding up to reach a maximum, then slowing down again. So it is more accurate to calculate the integral.

Question 19

When using the Continuity Equation to measure aortic valve area, A1, V1 (before the valve) and V2 (at or after the valve) are measured in which views and with which type of doppler (PW or CW)?

Answer 19

A1: measured, so no doppler used. Parasternal long axis. Measure the LVOT diameter.

V1: Apical view. PW (b/c want the velocity at that particular point)

V2: Apical view. CW (b/c want the max velocity)

Apical view with the velocities b/c need to line up the ultrasound beam with the direction of blood flow to be accurate.