Flashcards in PHY 2 FINAL Deck (189)
What is the frequency of a transducer if the period is 25 million cycles/ sec?
25 MHz Pg. 21
What are the ranges for audible, ultrasound, and infrasound?
Infrasound - less than 20Hz Audible - 20Hz - 20 kHz Ultrasound - greater than 20kHz Pg. 22
What are the seven parameters to describe sound waves? Is it adjustable? What is is determined by?
Period (time)- not adjustable, determined by source
Frequency (Hz)- not adjustable, determined by source
Amplitude (dB)- adjustable, determined by source
Power (W)- adjustable, determined by source
Intensity (W/cm2)- adjustable, determined by source
Wavelength (distance)- not adjustable, determined by source and medium
Speed (m/s)- not adjustable, determined by medium
If intensity remains the same, while power is doubled, what happens to the beam area?
Doubled Pg 44
What are the acoustic variables?
Distance (cm,mm) Pg 12
What would create the longest wavelength?
The lower the frequency, the longer the wavelength pg. 34
What is the term used to describe from the start of a pulse to the end of a pulse?
Pulse duration Pg 49
What scale do we use for decibels?
Logarithmic Pg 77
What will intensity do if you have 3 dBs?
Intensity is doubled at 3dB Pg 78
If initial intensity is less than the final intensity, then what will the gain in decibels be?
Positive, the beam's intensity is increasing pg. 79
Rayleigh scattering is related to ___.
Soft tissue attenuation coefficient is directly related to ___.
Frequency Attenuation coefficient= 0.5dB/cm/MHz
What are the different speeds and attenuation we will find in different mediums?
Medium, Attenuation, speed water, extremely low, 1480m/s blood/urine/biological fluids, low, 1560m/s fat, low 1450m/s soft tissue, intermediate 1540m/s muscle, higher, 1600m/s bong and lung, even higher, 3500m/s (bone) 500m/s (lung) air, extremely high, 300m/s pg. 86 and 37
If two PZT are made from the same material, the thicker crystal will make a pulsed transducer that is ___.
Lower frequency pg. 127
What happens when we exceed the Curie point?
Depolarization Pg 120
Which component of a transducer reduces ringing of a pulse and is made of epoxy resin impregnated with tungsten filaments?
Backing material "Damping element" Pg 115
Know all about crystals and what they may produce (thick/thin crystals, high/low speeds).
Materials which convert sound into electricity and vice versa
Names: Piezoelectric, ferroelectric, PZT, lead zirconate titanate, ceramic, active element, & crystal
High frequency transducer: thinner PZT with higher speeds
Low frequency transducer: thicker PZT with lower speeds
pg. 113 & 125
What resolution is improved by damping material?
Axial Pg 115
Longitudinal pg. 126
The voltage of a pulsed transducer is 6 MHz, what will the frequency be?
Cannot be determined by electrical signal pg. 126
Frequency is given for a continuous wave probe is 6 MHz, what is the operating frequency? (what is the relationship between these two)
Identical (6MHz) pg. 127
What is the order of impedences from greatest to least? (matching layer, skin, gel, PZT)
PZT > matching layer > gel > skin pg. 116
Which component of a transducer contains cork and prevents vibrations in the case from inducing an electrical voltage in the PZT of the transducer?
Acoustic insulator Pg 115
What does the matching layer do?
Increases the percentage of transmitted sound between the active element and the skin; protects the active element pg. 115-116
How are frequency and near zone length related?
Directly Pg 135
Anatomy of a sound wave (5 questions)
-Focus/focal point= where the beam is narrowest
-Near Zone/field, Fresnel Zone= distance from the transducer to the focus
-Near zone length/focal zone length/ focal depth= distance from the transducer face to the focus
-Far zone/ field, Fraunhoffer zone= region deeper than the focus, where the sound beam diverges
-Focal zone= region around the focus where the beam is relatively narrow, where the most accurate images come from
How is the focal length of a sound beam determined?
1) Transducer diameter
2) Frequency of sound
What is the spread of a sound beam in the far field?
Divergence pg. 139
What will create the best lateral resolution in the far field based on frequency and diameter?
The largest diameter and highest frequency (least divergence)
LARRD (multiple questions)
-parallel to beam's axis
-best with less ringing and high frequency pg. 146