(a)   between the sound source and the receiver creates a frequency change

The (a)   is a low frequency that rides on top of the much higher frequency transducer

(a)   = reflected frequency - transmitted frequency

When velocity is halved, the doppler shift is (a)  

Modern ultrasound systems actually measure the (a)   between the received and transmitted sound waves

The x-axis of doppler spectrum represents ___ while the y-axis represents __

(a)  

When the blood cells are moving (a)   to the sound beam, the entire velocity is measured

(a)   velocity = true velocity x cosine (angle)

Cosine 0 indicated movement (a)   the transducer

Cosine 180 indicates flow (a)   from the transducer

The most common clinical doppler devices are (a)   , which distinguish the direction of flow toward or away from the transducer

Bi directional spectral doppler tracing. Flow toward the transducer is (a)   the baseline

Bi directional spectral flow. Flow away from the transducer is (a)   the baseline

(a)   is a commonly used signal processing technique for bi directional doppler

Requires two crystals in the transducer

(a)  

It has the ability to measure very high velocities

(a)  

CW doppler: Exact location of the moving blood cells can not be determined. This is called (a)  

Simultaneous anatomic imaging and doppler is called - (a)  

Do Not use backing material

(a)  

Range resolution, range specificity, freedom from range ambiguity artifact is great advantages of (a)  

With (a)   the sonographer positions a small marker, called sample volume or gate

Aliasing is a disadvantage of (a)  

Regrading aliasing, the top of the image is (a)  

Aliasing appears on the (a)   of the spectrum

Aliasing occurs when the sampling rate is too (a)   in comparison to the measured blood velocities

(a)   = PRF/2

Is the highest doppler frequency or velocity that can be measured without the appearance of aliasing

(a)  

When the sample volume is deep, the PRF is low and the nyquist limit is (a)  

Deeper sample volumes have a lower PRF and creates (a)  

When the sample volume is shallow, the PRF is high, velocity is sampled many times per second, and the nyquist limit is (a)  

(a)   Nyquist limit accurately measures the velocities without aliasing

Reduce doppler shift, raise the nyquist limit

(a)  

(a)   frequency transducers create more aliasing

Adjust scale to its maximum

(a)  

2. 2. Select a new ultrasonic view with a shallower sample volume

3. 3. Select a new ultrasonic view with a shallower sample volume

5. 3. Select a lower frequency transducer

4. 4. Use baseline shift

5. 5. Use CW doppler

Adjusting scale (a)   nyquist limit

Shallower view, (a)   nyquist limit

Lower frequency transducer, (a)   doppler shift

Zero baseline shift, (a)   remains but display more appealing

CW doppler. (a)   aliases but range ambiguity

Range resolution, sample volume, sample volume, limited maximum velocity, aliasing

(a)  

Range ambiguity, region of overlap, unlimited maximum velocity, no aliasing

(a)  

• Found in veins or slower-moving arterial blood.

• Doppler shifts: 100 Hz to 1 kHz

• Common in medium-sized arteries, such as renal or carotid arteries.

• Doppler shifts: 1 kHz to 5 kHz

• Found in high-speed arterial blood flow, such as in the aorta or stenotic vessels.

• Doppler shifts: 5 kHz to 10 kHz or higher

• Higher ultrasound frequencies (e.g., 5-10 MHz) used in superficial structures lead to (a)   Doppler shifts.

Lower ultrasound frequencies (e.g., 2-5 MHz) used in deeper structures result in (a)   Doppler shifts

A typical Doppler shift in the (a)   can range from 1 kHz to 5 kHz, depending on the blood flow velocity and the ultrasound frequency used

A Doppler shift in the (a)   might be in the range of 100 Hz to 1 kHz, due to slower blood flow velocities.

If the PRF is set at 10 kHz, the Nyquist limit is 5 kHz. If the Doppler shift exceeds 5 kHz, the system incorrectly interprets the frequency causing (a)  

• Involves mixing the received signal with two reference signals that are 90 degrees out of phase with each other (I/Q demodulation).

• Provides information about both the magnitude and direction of the Doppler shift

• Common in spectral Doppler.

• Involves rectifying the Doppler signal to produce a positive-only signal and then applying a low-pass filter to extract the envelope of the signal, which represents the amplitude variations

Combines B-mode imaging (grayscale) with spectral Doppler to provide anatomical and flow information simultaneously

(a)  

• The reflected Doppler signals are processed using (a)   to create a spectrum displaying velocities (frequency shifts) on the vertical axis and time on the horizontal axis. The intensity of the signal represents the number of blood cells moving at each velocity.