Ch.1
A number in scientific notation form with a positive exponent has a value greater than?
10
Sound waves are ________ and ________
Mechanical and longitudinal
What is the definition of Period? What is the unit?
Definition: the time from the start of one cycle to the start of the next cycle
Unit: units of time (microseconds, seconds, hours, days)
What are the 5 parameters needed when describing pulsed sound?
Pulse duration, pulse repetition period, pulse repetition frequency, duty factor, spatial pulse length
What are the 5 key words that are related to the intensities of pulsed waves?
Spatial, average, peak, temporal, pulsed
What is the meaning of -3 dB?
Half
How can the depth of a reflector be accurately calculated from the go-return time?
1.54 mm/microseconds x go-return time (microseconds) / 2
What is the thickness of the matching layer?
¼ the wavelength of sound in the matching layer
List the five terms that describe the shape/regions of a sound beam
Focus, near zone, focal length/near zone length, far zone, and focal zone
What are the mnemonic/other names for axial resolution?
Longitudinal, Axial, Range, Radial, and Depth
Which mode shows a dot moving at a constant speed across the system’s display and is then seen as a series of upward spikes?
A-mode
In a mechanical beam, in what two planes does focusing occur?
Horizontal and vertical planes because of the hourglass shape of the sound beam
What does spatial resolution improve with?
Higher line density
The acoustic power of a sound beam emitted from a transducer is determined by the (blank) of the pulser’s signal
Voltage
How many gray shades can be represented by a group of 4 bits?
16 (2*2*2*2)
What is it called when two numbers are multiplied together and the result is 1?
Reciprocal relationship
Sound waves are also known as ________ waves
Acoustic
What is the definition of Frequency? What is the unit?
Definition: the number of cycles per second
Unit: Any unit per second
What type of sound wave cannot create anatomic images?
Continuous wave
What is the most relevant intensity in respect to tissue heating?
SPTA
What are the 2 things attenuation determined by?
Path length, frequency of sound
How is PRP calculated in soft tissue?
Imaging depth (cm) x 13 microseconds/cm
What are the two characteristics of damping material?
High degree of sound absorption and acoustic impedance similar to PZT
What characteristics of a fixed focus transducer determine the focal depth?
Transducer diameter and frequency of the sound
In what two ways is a short pulse created?
Less ringing (fewer cycles in the pulse) and higher frequency
What is represented on the x-axis and y-axis of an A-mode display?
X = reflector depth, Y = represents the strength or amplitude of the reflected signal
Which active element(s) provide the thinnest ultrasound slices and the best elevational resolution within the focal zone?
Disc-shaped crystals (found in mechanical and annular phased array transducers)
A sonographer adjusts an ultrasound scan to double the depth of view from 5cm to 10 cm. If the frame rate remains the same, what also occurs?
Narrower sector
What control do you need to adjust on the ultrasound system when it displays only reflectors in a region close to the transducer but no reflectors that are deep?
Adjust the systems compensation
What electronic component is required to create gray scale imaging or displays?
Scan converter
What is 1,000,000 in scientific notation form?
1.0 x 10^6
What are the 3 acoustic variables?
Pressure, density, distance
What is the definition of Amplitude? What is the unit?
Definition: The difference between the maximum value and the average or undisturbed value of an acoustic variable. The “bigness” of the wave.
Unit: Units of any of the acoustic variable (Pressure: Pascals, Density: kg/cm^3, Distance: any distance)
What is pulse duration?
The actual time from the start of a pulse to the end of that pulse.A single transmit or “on” time.
What is the unit for all intensities?
watts/cm^2
What are 2 forms of reflection?
Specular and diffuse
What is the equation for determining PRF?
77,000 cm/s / Imaging depth (cm)
What is the equation for quality factor?
Main frequency / bandwidth
How do the transducer diameter and frequency affect focal depth?
Transducer diameter and focal depth are directly related (a beam with a larger diameter active element will have a deeper focus), frequency and focal depth are also directly related (an 8 MHz beam will have a deeper focus than a 4 MHz beam)
What are the three methods of focusing, and which is used in array transducers
External focusing, internal focusing, and phased array focusing
What do the x-axis and y-axis of a B-mode display represent?
X = reflector depth, Z = amplitude information
What is dynamic receive focusing, and when does it occur?
It uses variable time delays, which focus the reflected sound at many depths. This occurs during reception
What form of resolution improves when frame rate increases?
Temporal resolution
What ultrasound component needs to be adjusted when the ultrasound system is overly saturated?
Decrease the output power
What is the number of shades that can be represented by n bits?
2^n
What is the relation when two items are associated such that when one item increases, the other one decreases?
Inversely related
Sound travels in a _______ line
Straight
What is the definition of Power? What is the unit?
Definition: The rate of energy transfer or the rate at which work is performed
Unit: Watts
What is the spatial pulse length?
The distance that a pulse occupies in space from the start to the end of a pulse.
What intensity is the highest?
SPTP
What is the definition of impedance?
The acoustic resistance to sound traveling in a medium
If our depth is shallow, what will the PRP and PRF be?
PRP will be short and PRF will be high
What two characteristics of the active element determine the frequency of sound in the pulsed wave transducer?
The speed of sound in the PZT and the thickness of the PZT
What is the equation for focal depth
Diameter^2 x frequency / 6
What are the mnemonic/other names for lateral resolution?
Lateral, Azimuthal, Transverse, and Angular
What is the only mode that provides information about a reflector’s changing location with respect to time?
M-mode
How is a linear sequential array transducer beam steered, and what image shape does it create?
A small group of the crystals is fired simultaneously, and sloped-patterned phase delays steer the beam. It has a parallelogram-shaped image
What is the time needed to make a single image if the frame rate of an ultrasound system is 20 Hz?
0.05 s
What determines the firing delay patterns for phased array systems?
Beam former
Where does coded excitation take place?
In the pulser
What is the value of the metric unit Giga?
1,000,000,000
What are the 7 acoustic parameters used to describe the characteristics of a sound wave?
Period, frequency, amplitude, power, intensity, wavelength, propagation speed
What is the definition of intensity? What is the unit?
Definition: the concentration of energy in a sound beam
Unit: W/cm^2
What is pulse repetition period?
The time from the start of one pulse to the start of the next pulse. Includes one pulse duration plus one listening time
For what type of ultrasound is the beam always “on”
Continuous wave ultrasound
What does incidence mean?
The angle at which the eave strikes the boundary
The depth of a reflector is 3 cm. What is the time of flight and total distance traveled by the pulse?
Time of flight is 39 microseconds, and the total distance traveled is 6 cm.
What is the frequency of sound from a continuous wave transducer when the transmitter creates a 4 MHz electrical signal?
The acoustic frequency is 4 MHz
What is Huygen’s Principle?
Qualifies how sound waves that are produced by very small sources diverge in a V-shaped wave
What are the four effects of focusing a beam?
Beam diameter in the near field and focal zone is reduced, focal depth is shallower, beam diameter in the far zone increases, and the focal zone is smaller
What do the x-axis and y-axis of an M-mode display represent?
X = time, Y = reflector depth
When an array transducer is used, and the ultrasound system changes the number of crystals along the face of the probe used to transmit pulses and receive reflections, what is this called, and what does it do to lateral resolution?
Variable aperture/dynamic aperture is the number of elements used to create sound beams or to receive reflected echoes. It improves lateral resolution at a wide range of depths
When the frame rate is 30 Hz, how long does it take to create a frame?
1/30 sec
Maintains and organizes the proper timing and interaction of the systems components?
Master Synchronizer
What is DICOM?
Protocols for medical image data.
What are in-phase waves?
What are out-of-phase waves?
In-phase waves: When their peaks or maximum values and their lows or minimum values occur at the same time and at the same location
Out-of-phase waves: When two wave peaks and lows occur at different times. When they are not in sync
What is the definition of wavelength? What is the unit?
Definition: The distance or length of one complete cycle
Unit: mm, meters, any unit of length
What is pulse repetition frequency?
The number of pulses that an ultrasound system transmits into the body each second.
Which law quantifies the physics of refraction?
Snell’s Law
What is the definition of propagation speed? What is the unit?
Definition: The rate at which a sound wave travels through a medium
Unit: units of meters per second or any distance divided by time
What is duty factor?
The percentage or fraction of time that the system transmits a pulse