Physics FINAL — Fall 2024 Flashcards
- What is the pulse duration if you have a 8 MHz beam and there are 3 cycles in each pulse?
**Do not round until you get to your final answer, then round two decimal places. **
0.38 microseconds
- What is the pulse duration frequency if your transducer is 2 MHz, there are 3 cycles in the pulse, and the target was 4 centimeters away?
Round your answer to 2 decimal places
? 36.4 kHz
- At a frame rate of 24 frames per second, what is the time for a single frame to occur?
Round to 2 decimal places
0.04 sec
- How can the sonographer increase the frame rate?
Decrease the depth of field
- True/False
Is this frame rate achievable?
FR: 37
Line density: 111
Focuses: 3
Depth: 11 cm
False
(Not achievable)
- What determines the resonant frequency of a transducer?
Thickness and propagation speed of the element
- How would 40 Hz best be classified?
Audible sound
- In DMS, what will happen to the wavelength if the frequency is doubled?
It is halved
- What is another name for axial resolution?
Range
- How can a manufacturer improve the axial resolution of a transducer?
Shorten the spatial pulse length
- Where is the best axial resolution?
Axial resolution is equal throughout the entire beam
- What is the lateral resolution equal to?
The beam diameter
- Four factors that affect the lateral resolution of a reflector are:
- transducer frequency
- crystal diameter
- transducer focus
- depth of reflector
(NOTE: lateral resolution is NOT affected by spatial pulse length).
- What is another name for elevational resolution?
Z plane
- Which type of transducer can decrease the slice thickness of the beam?
Linear array with multiple rows of elements
- What is required to display rapid motion when scanning?
Fast frame rate
- True/False:
The line density influences temporal resolution
True
- For an unfocused transducer, what is the approximate beam width at the focal distance and twice the focal distance, given a crystal diameter of 6mm?
6 mm, 12 mm
- The diameter of a flat unfocused 7 MHz transducer is 10 mm. The near zone length is 6 cm. What is the approximate lateral resolution at a depth of 12 cm?
??
- What are four acoustic variables?
Density
Temperature
Particle motion
Pressure
(NOTE: Frequency is NOT an acoustic variable)
- What is the period of a 7 MHz beam?
Do not round until you get to your final answer. Then round to 2 decimal places
0.14 microseconds
- What causes anechoic areas on an image?
No acoustic impedance mismatch
- What does a duty factor of zero represent?
The ultrasound unit is off
- Find the duty factor given the information below:
Frequency: 4 MHz
Cycles: 3
Crystal diameter: 4 mm
Depth: 5 cm
Round to 3 decimal places
0.011
- On which principle does a diagnostic medical sonography transducer operate?
Piezoelectric effect
- What determines the angle of reflection at an interface?
Angle of incidence
- What is the amount of reflection expected from a soft tissue / soft tissue interface ?
1% or less
- The angle between two interfaces is 78 degrees. If the velocity in second medium is less than the first medium, then the transmission angle will be:
Less than the incident angle
- What would cause a strong echo at an interface?
A great change in impedance
- What would be the result of a reflection coefficient of 0.1?
Transmission coefficient of 0.9
- Specular interface occurs only:
At a smooth interface
- What effects non-specular reflections?
Frequency and angle of insonation
- What is the axial resolution if you have a 2MHz beam, the SPL is 4mm, and the beam is traveling 3cm?
2 mm
- What is the axial resolution if there is 3 cycles per pulse in a 4 MHz beam traveling in soft tissue with a crystal diameter of 4 mm?
Do not round until you get to your final answer, then round to 2 decimal places
0.77 mm
- The angle of incidence is equal to 90 degrees. The acoustic impedance of medium one equals four rayls and the propagation speed of medium one equals 1.54 mm/us. The acoustic impedance of medium two equals four rayls and the propagation speed of. medium two equals 1.45 mm/us. What is the IRC?
0%
- In DMS, how will halving the operating frequency affect the propagation speed?
It will not be affected
- What unit expresses the relative measurement of intensity based on a logarithmic scale?
Decibels
- Fifty decibels (50dB) would represent which intensity ratio?
100,000:1
- What does half-intensity depth correspond to in diagnostic ultrasound?
- 3 dB
- An ultrasound wave leaves the transducer, travels through tissue, and returns 10 microseconds later. What is the distance to the reflector?
7.7 mm
- Why do ultrasound waves travel faster in solids than in liquids?
Solids have higher stiffness
- A real-time instrument produces images at 30 frames per second at an imaging depth of 15 cm. The line density and focus are to remain constant. To increase the maximum imaging depth to 30 cm, what would the frame rate result in?
15 frames per second
- What is the pulse repetition frequency?
Number of ultrasound pulses transmitted per second
- If the transducer Q value is low, its bandwidth is:
High
- The intensity of an ultrasound beam is 1000 mW/cm^2, you increase the power 20 dB. What is the new intensity of the beam?
100,000 mW/cm^2
- Arrays are operated in two ways called ____ and ____
Sequencing and phasing
- In a curved array, the pulses travel ______
Out in different directions
- Written
Name four ways that focusing is accomplished. Not the natural focus of the element, but how that can be altered.
Mirrors
Lenses
Curved surface
Electronically
- Three factors involved in mechanical transducers:
- has a fixed focus
- are the least expensive of all the real time transducers
- transducer is steered mechanically, typically by a motor.
(FALSE: if a crystal breaks, a black line in an erratic place on the screen is seen)
- What will happen to the crystal if you heat a transducer above the Curie point?
Becomes depolarized
- True/False
Only transvaginal probes are constructed in a way that may be autoclaved
False
- Determine the percentage of transmitted power at a boundary if the acoustic impedance of the first medium is 20 (unit) and the acoustic impedance of the second medium is 10 (unit).
The unit is not given so not to interfere with another question.
Do NOT round until you get to your final answer. Then round to 2 decimal places.
11.11%
- Three advantages of focusing:
- increased ability to resolve structures placed close together side-by-side in the imaging field
- improvement of image quality closer to the sound source
- reduction of near field variation in intensity
(Note: NOT increased divergence in the far field)
- This technique is used to help eliminate grading lobe artifacts by sending a stronger electrical signal to the inner elements of the transducer and progressively weaker ones to the outer elements
Apodization
- An ultrasound beam has an initial intensity of 1,000 mW/cm^2. The return echo is 0.001 mW/cm^2. What is the decibel difference?
-60 dB
- One benefit of composite piezoelectric elements over the natural elements is:
Acoustic impedance closer to that of soft tissue
78.The type of ultrasound scattering found with blood cells is termed:
Rayleigh scattering
- True/False
The compression portion of a wave represents an area of low pressure
False
- Dynamic aperture:
Reduces beam width and changes with depth
- Determine the near zone length of a 2 MHz transducer that has a diameter of 12mm
48 mm
- What is the term for the time from the beginning of one pulse to the beginning of the next pulse?
Pulse repetition period
- True/False
Increasing the depth will cause an increase in the duty factor.
False
- True/False
The pulse repetition period will become larger when scanning deeper structures
True
- WRITTEN
List the different names that correspond to the acronym LATA
Lateral
Angular
Transverse
Azimuthal
- WRITTEN
List the different names that correspond to the acronym LARD
Longitudinal, axial, range, radial, depth
- What is the half value layer of an 8MHz transducer?
0.75 cm
- Luez’s law
???
- Snells law
??
- Huygens principle
???
- True/False
Axial resolution is proved with the use of harmonic imaging
False
- Express 7 nanometers in scientific notation
7 x 10^-9
- What is the best category for a 0.00035 MHz beam?
Infrasound
- What is an example of a specular reflector?
Renal capsule
