Questions and Answers
What is pulse duration?
The actual time from the start of a pulse to the end of that pulse
What is the pulse duration equation?
Pulse duration (μs) = # of cycles in pulse x period (μs)
Shorter duration pulses are desirable for imaging because they create images of greater accuracy.
True
What is spatial pulse length (SPL)?
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What is the relationship of spatial pulse length to cycles and wavelength?
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What is pulse duration?
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What is the distance of the pulse end to end referred to?
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What is the equation for spatial pulse length?
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What characteristics contribute to long pulses?
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What characteristics lead to short pulse lengths?
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What is pulse repetition period?
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When imaging at shallow depths, the time from one pulse to the next is long.
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When imaging more deeply, the time from one pulse to the next is longer.
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Pulse repetition period is unrelated to the period.
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Pulse repetition period and imaging depth are directly related.
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What can a sonographer not change regarding pulse duration?
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Only the listening time portion of the pulse repetition period is changed when the sonographer alters imaging depth.
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What is pulse repetition frequency (PRF)?
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How are pulse repetition frequency and depth related?
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What is the relationship between pulse repetition period and pulse repetition frequency?
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What is the equation for pulse repetition frequency?
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Which of these four values of pulse repetition frequency would have the longest pulse repetition period?
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Which of the following four waves has the highest pulse repetition frequency?
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Which of these four pulses with PRS listed below has the shortest pulse repetition period?
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Which of the following four waves has the lowest pulse repetition frequency?
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Two waves can have identical pulse repetition frequencies even if their pulse repetition periods are different.
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Two waves can have identical PRFs even if their periods are different.
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Two waves can have identical PRFs even if their frequencies are different.
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What is duty factor?
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Study Notes
Pulse Duration
- Defines the time from the start to the end of a pulse, measured in time units.
- Is determined by the sound source and is not adjustable.
Pulse Duration Equation
- Calculated as: pulse duration (μs) = number of cycles in pulse x period (μs).
Imaging and Pulse Duration
- Shorter duration pulses enhance imaging accuracy.
Spatial Pulse Length (SPL)
- Represents the distance occupied by a pulse, measured in distance.
- Determined by both the sound source and the medium, and is non-adjustable.
- Directly proportional to the number of cycles and wavelength, and inversely proportional to frequency.
SPL Equation
- Calculated as: SPL (mm) = number of cycles x wavelength (mm).
- Characteristics for long pulses include many cycles and longer wavelengths, while short pulse lengths have fewer and shorter wavelength cycles.
Pulse Repetition Period
- The interval from the start of one pulse to the next, measured in time.
- Determined by the sound source and is adjustable.
Imaging Depth and Pulse Repetition Period
- Imaging at shallow depths results in shorter intervals between pulses.
- Deeper imaging causes longer intervals.
- PRP and imaging depth have a direct relationship.
Pulse Duration and Sonographer Control
- Sonographers cannot change pulse duration as it is a fixed characteristic of the transducer.
Altering Imaging Depth
- Only the listening time portion of the pulse repetition period is modified when imaging depth is adjusted.
Pulse Repetition Frequency (PRF)
- Indicates the number of pulses transmitted per second, measured in Hz.
- Determined by the sound source, which is not adjustable.
PRF and Depth Relationship
- Inversely related: increasing depth decreases PRF, while decreasing depth increases PRF.
Pulse Repetition Period and Frequency Relation
- They are reciprocals: a longer PRP corresponds to a lower PRF and a shorter PRP corresponds to a higher PRF.
PRF Equation
- Expressed as: PRF x PRP = 1, or PRF = 1/PRP.
Multiple Choice Questions on PRF
- The longest pulse repetition period is associated with a PRF of 6 Hz.
- A pulse repetition period of 5 ms corresponds to the highest PRF.
- A PRF of 20 kHz corresponds to the shortest pulse repetition period.
- The pulse repetition frequency with the lowest value is associated with a period of 8 s.
True or False Statements
- Two waves cannot have identical PRFs if their pulse repetition periods differ (False).
- Identical PRFs may exist even if their periods are different (True).
- Two waves can have identical PRFs even if their frequencies differ (True).
Duty Factor
- Represents the proportion of time that the system is actively transmitting pulses.
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Test your understanding of key concepts from Chapter 4 on ultrasound physics with these flashcards. Focus on important terms like pulse duration and its impact on imaging accuracy. Perfect for reinforcing knowledge for exams or class discussions.
