PHY 2 Final Prep Flashcards by Sonography ♡

If the relative output power of an ultrasound instrument is calibrated in decibels and the operator increases the output by 20 dB, what would the beam intensity be increased by?

One hundred times.

(A 10 dB increase = ×10 increase in intensity
A 20 dB increase = ×10 ×10 = ×100 increase in intensity)

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Refraction is a change in what parameter of the ultrasound beam?

Direction

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A real-time instrument produces images at 30 frames per second. The maximum imaging depth is 15 cm.
The line density is constant. To increase the maximum imaging depth to 30 cm, you would change the frame rate to how many frames per second?

15 fps

(The system shows 30 images per second when looking 15 cm deep.
If you want to look twice as deep (30 cm), the system needs more time for the signal to go down and come back. Because of that, it can only show half as many images per second so it isn’t as much work on the machine to look deeper into the body.)

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What is the relationship between pulse repetition frequency and imaging depth?

Inversely related

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A 7.5 MHz transducer produces approximately what size wavelength in soft tissue?

0.2 mm

Wavelength =
Speed of sound in soft tissue ≈ 1540 m/s
Frequency = 7.5 MHz = 7,500,000 Hz

1540 / 7500000 =0.000205

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When comparing gray scale and bistable imaging systems, what does a gray scale imaging system display that is not seen with a bistable system?

A range of reflection amplitudes.

(Bistable imaging shows only two brightness levels: black or white (on/off).
Gray scale imaging shows many levels of brightness, representing a range of echo strengths (amplitudes).
This allows gray scale systems to provide more detailed images compared to bistable systems.)

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In general, a Doppler frequency shift could result from…

A moving sound source and a stationary listener.
A stationary sound source and a moving listener
A moving sound source and a moving listener

(Note: could NOT result in a stationary sound source and a stationary listener)

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How many shades of gray is a four bit digital scan converter memory capable of storing?

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What technique is used to fill in empty data between scan lines?

Interpolation

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What are three factors which could cause the presence of FALSE sludge/debris in a cystic mass?

Reverberation artifact
Scanning at high gain
Side lobe artifact

(Note: NOT Speed of sound artifact)

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A linear array transducer scans by generating lines of insonation from:

Different points, each line traveling parallel to each other

(A linear array transducer works by originating from different points along the transducer surface and
Traveling parallel (not angled) (straight line))

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You are scanning the liver and the beam travels through a mass in the right lobe that has a propagation speed of 1.62 millimeter/microsecond. Where will the mass be placed on the screen?

Too anterior from its actual position.

(Since the sound travels faster than expected, the system thinks it took less time to reach the structure and return. But it doesn’t know the speed is faster—it assumes 1.54 mm/μs—so it underestimates the depth and the mass will be displayed closer to the surface (i.e., too shallow) on the screen than it actually is.)

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There are several differences between pulsed and continuous wave Doppler. What is one true statement about continuous wave Doppler?

Continuous wave Doppler:

Simultaneously transmits and receives ultrasound.

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What do interfaces that produce echoes depend on?

change in acoustic impedance

(The greater the mismatch in impedance between two tissues, the stronger the reflection (echo))

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Aliasing occurs when the Doppler shift exceeds the:

Nyquist limit

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Using color flow Doppler, if you steer the color window to the right or left, the frame rate will:

Not be changed.

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You are scanning an interface at normal incidence in which the acoustic impedance is unchanged from one media into the other, but the acoustic velocity is 2 times higher in media one than it is in media 2. What likely will occur?

There will be no reflected sound.

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What does Huygens Principle refer to?

Constructive and destructive interference of sound waved from multiple sources.

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You are experiencing blossoming while scanning a patients carotid artery. This is making the vessel look as though it is larger than what it actually is. How do you eliminate the color Doppler artifact?

Turn the color Doppler gain down

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In diagnostic medical sonography, the wavelength of a 2.25 MHz ultrasound beam is:

0.7 mm

(Wavelength = Propagation speed / Frequency)

(Frequency must be in Hz)
(2.25 MHz x 10^6 = 2,250,000 Hz)

(1540 m/s / 2250000 Hz = 0.7 mm)

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Doppler power mode will display:

1.Doppler signal strength
2. Tissue perfusion
3. Presence of flow within small vessels

(Note: does NOT display flow velocity)

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Spectral broadening will cause what change in a spectral analysis tracing?

Vertical thickening

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The cosine of the angle in the Doppler forums refers to the angle between…

The beam transmitted and the direction of flow

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During pulse-wave Doppler you send a 5MHz beam and then you received back a 4.89 MHZ beam. Which direction will the blood be moving?

Away from the probe

(Since the received frequency (4.89 MHz) is lower than the transmitted frequency (5 MHz), it indicates a negative Doppler shift, which means the blood is moving away from the probe.)

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T/F Power Doppler is more sensitive to detecting minor differences in flow direction over color Doppler.

False (Power Doppler is NOT sensitive to flow direction; color Doppler is.)

T/F Shadowing results in decreased echo amplitudes.

True

List three examples of “useful” artifacts:

1.Posterior enhancement from the bladder while scanning a female pelvis. 2. Twinkle artifact from Adenomyomatosis 3. Shadowing posterior from a kidney stone (Note: Liver mirrored on the opposite side of the diaphragm is NOT useful)

An increase in bits per pixel will increase the…

contrast resolution (Bits per pixel determine how many shades of gray can be represented in an image. More bits per pixel = more possible gray levels = better contrast resolution (the ability to distinguish between small differences in echo intensity).)

What causes enhancement?

weakly attenuating structure (Enhancement (also called posterior acoustic enhancement) is an artifact seen in ultrasound imaging where structures behind a weakly attenuating area (like a cyst or fluid-filled structure) appear brighter than expected.)

What is related to heating?

Absorption

Which zoom method improves spatial resolution ?

write magnification

***WRITTEN A board of pixels is called a _________ .

Matrix

When using a test phantom, what is the dead zone testing for?

The area in the near field that can’t be seen due to reverberation

T/F Harmonic energy is non-existent in the near field.

False (Harmonic energy starts in the near field; so its weak but it is there)

T/F A higher signal to noise ratio implies better imaging with more trustworthy data.

True

What is being measured during the PD and measures/calculates the average intensity within the pulse?

SPPA

T/F Transmural pressure is the amount of pressure that is being exerted on the vein from outside forces.

False. (Transmural pressure is the difference between the pressure inside a vessel and the pressure outside the vessel: Transmural Pressure = Intraluminal Pressure — External Pressure)

Under similar exposure conditions, the expected temperature increase in bone is _____________________ than in soft tissue

significantly greater (Under similar exposure conditions, bone absorbs ultrasound energy much more efficiently than soft tissue. This means: more energy is converted to heat in bone)

When using a chi square to compare a test against the golf standard; the specificity tells you the ability of the test to detect disease.

False (Sensitivity detects the presence of disease; Specificity detects the absence of disease)

T/F Artifacts are distorted portions of the image that have to be corrected.

False (Artifacts do NOT always need to be corrected — they often help in diagnosis)

Inspiration ____________ intrathoracic pressure and ______________ intraabdominal pressure.

Decreases intrathoracic pressure and Increases intrabdominal pressure

T/F A patient with polycythemia will have a decreased blood viscosity.

False. (Polycythemia increases blood viscosity.)

T/F In transient cavitation the bubbles expand and collapse violently causing the bubble to implode.

True (Opposite of stable cavitation)

What is the term used to describe the picture elements?

Pixel

This function in the receiver takes the negative half of a signal and turns it into a positive voltage.

Rectification

Who is at risk for being exposed to bio effects from an ultrasound examination?

Only the patient

You are doing a study to determine if venous Doppler ultrasounds should replace the gold standard which is a venogram. You tested 125 people with both methods. Out of the 125 tested 10 exams were negative sonographically but positive via the venogram. Which of the following indices would that number correlate to?

False negative

What type of experimental bio effect study analyzes populations of individuals?

Epidemiological

Persistence smooths out your image but your ______________ resolution is diminished

Temporal resolution

What would the number 392 be represented as in the binary system?

110001000

According to Poiseuilles equations, a small change in which factor has the greatest influence on volume flow rate?

Radius

Which intensity parameters are just for the “on time”?

SPTP & SPPA

Decreased distal resistance normally has what effect on end-diastolic flow?

Increased diastolic flow

What are four things that are increased when the output (transmit) power control is increased?

1.Patient exposure 2.Dot brightness on a gray scale echo display 3.Amplitude of acoustic pulses transmitted into tissue 4.Amplitude of echoes returning to the transducer (Note: Number of transmit pulses per second is related to PRF, not output power.)

T/F There are test phantoms to access the accuracy of your spectral analysis but there is not one available to evaluate color Doppler accuracy.

False

At a distance of two near zone lengths, the beam diameter is _____________ the transducer diameter.

Equal to

Plant studies are useful primarily to:

Determine conditions in which NONthermal effects occur

The ability of a gray-scale display to distinguish between echoes of slightly different intensities is called:

Contrast resolution

T/F A highly compressed signal will have a greater contrast resolution.

True

T/F When a vein has a dumbbell appearance, the pressure and the volume of blood is low.

True

T/F For continuous wave ultrasound the SATA and the SATP are equal.

True

What happens to the kinetic energy at an area of stenosis?

Increases

The thermal index is a ratio between the acoustic power generated by the probe and the power required to raise the tissue in the medium by 1 degree Fahrenheit.

False (1 degree Celsius)

What parameters can be evaluated with a 100mm test object?

-range accuracy -axial resolution -dead zone (Note: NOT contrast resolution; contrast resolution depends on the relative difference in tissue types)

T/F There are currently no phantoms to test Doppler applications.

False

Acoustic pressure or intensity can be calculated using a(n) _________________.

Hydrophone

If sound waves of 3 MHz, 5 MHz, and 10 MHz are transmitted through the same section of liver reflections, which frequency would reach the transducer first?

Reflections from all three frequencies would have identical transmit times.

What is related to the intensity of a color Doppler image?

Luminance

The conversion of echo voltages to video form is termed _________________ .

Demodulation

Which modality provides precise information regarding the variation in velocities present at a selected location in the field?

Pulsed Doppler with spectral analysis

T/F Flow volume and flow velocity represent the same parameter.

False (Flow velocity and flow volume are two different parameters)

What are three characteristics that are wanted for an initial screening test?

- high sensitivity is important - low false positive rate is important - risk and cost should be low - high specificity is important (Note: low specificity is NOT acceptable)

If there is a stenosis at the right carotid bulb, where will you possibly see turbulent flow?

Proximal right ICA

Color can change in a vessel due to…

1.Change in Doppler angle 2. Increase in flow speed 3. Vessel contour

What is the result of vasoconstriction over a large area?

Flow volume decreases.

Which parameter is used when discussing possible biological effects?

SPTA intensity

The volumetric flow rate (Q) is equal to:

pressure difference (P) multiplied by the resistance (R)

What is the pulse duration of a four cycle pulse in a period of 0.5 microseconds?

2.0 microseconds (#cycles x period = PD)

What is the science of identifying and measuring the characteristics of an ultrasound beam that are relevant to its potential for producing biological effects?

Dosimetry

What all should be kept in a file for EACH ultrasound machine?

All of the following: QA test results Warranty Purchase order Preventative maintenance reports

T/F If the length of the tube increases, the flow rate will also increase.

False. (Radius increases = Flow rate decreases)

What type of ultrasound exam causes the greatest concern regarding bio effects while performing it?

Fetal

Which component of the ultrasound unit determines the firing sequence, delay patterns, and delays during reception for the transducers?

Beamformer.

****WRITTEN Find the PRP from the following information. Round to 1 decimal place at the end of you calculations. Frequency: 4MHz #Cycles: 3 Depth: 6cm #Focus: 2

78.8 micro sec

***WRITTEN Your department is now doing lower extremity arterial studies and would like to eliminate arteriograms as a routine test. You will be comparing your results to the arteriograms to determine if your arterial studies can be relied upon. Of 110 patients tested by both modalities there were 93 shown to be positive for arterial stenosis by both studies. Also, the arteriogram demonstrated 17 negative tests and three of them were ones you found to be positive. What is the positive predictive value?

96.9% PPV = True Positive / (true positives + False Positives) x 100

***WRITTEN What are the 5 functions of the signal processor? They must be named in order.

Amplification Compensation Compression Demodulation Rejection

***WRITTEN What are the 6 assumptions of ultrasound imaging systems?

1. Sound travels in a straight line 2. Reflections come from main beam axis 3. Intensity corresponds to strength 4. Imaging plane is thin 5. Sound travels to reflector and back 6. Sound travels at 1.54 mm/microsecond

***WRITTEN What is the binary number 110101101 equal to?

429

What does the term “bit” mean in computer science?

Binary digit

T/F When there is vasodilation of the lower extremities, cardiac output increases

True

****WRITTEN What does ALARA stand for?

As low as reasonably achievable

Approximately how much time passes between pulse transmission and echo reception from a 5 cm deep interface?

65 microseconds (Sound travels 1 cm in soft tissue in 13 microseconds (µs) round-trip.) (Time=Depth×13μs/cm)

***WRITTEN The incident intensity of a wave is 100 mW/cm^2 Use the information below to find the final intensity. Period: 0.125 microseconds Depth: 5cm

0.32 mW/cm^2

How do you convert MHz to Hz?

X 10^6

PHY 2 Final Prep Flashcards

(94 cards)