Ultrasound Chapter 4 Flashcards

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.

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.