Title | Physics registry exam Study Guide |
---|---|
Author | Maddie Black |
Course | Ultrasound Instrumentation |
Institution | University of Missouri |
Pages | 5 |
File Size | 114.1 KB |
File Type | |
Total Downloads | 86 |
Total Views | 158 |
Physics registry exam study guide...
SPI STUDY GUIDE 109 106 103 102 101 10-1 10-2 10-3 10-6 10-9
giga mega kilo hecto deca deci cent milli micro nano
G M k h da d c m u n
billion million thousand hundred ten tenth hundredth thousandth millionth billionth
Acoustc variables (PPTD) pressure partcle moton (distance) temperature density Sound is a mechanical, longitudinal wave Parameters describing sound: period (can’t change) frequency (can’t change) amplitude (change) power (change) intensity (change)
Propagaton speed
Wavelength
Determined by sound source: 1. period 2. frequency 3. amplitude 4. power 5. intensity Determined by sound source and medium: 1. wavelength Determined only by the medium: 1. propagaton speed Period- length of tme it takes to complete 1 cycle or tme from start of 1 cycle to next
Frequency- number of cycles per second Hertz: 1 cycle/second Typically, 1 to 10 MHz affects penetraton and axial resoluton Amplitude- the difference between the average value and maximum value of an acoustc Variable (not between max and min. that would be peak to peak amplitude) Power- the rate that work is performed or energy is transferred Intensity- the concentraton of energy in a sound beam Typically, 0.001 (1mW/cm2) to 100 W/cm2 Wavelength- distance or length that 1 cycle occupies Typically, 0.1 to 0.8mm influences longitudinal resoluton can’t change Propagaton speed-speed that sounds travels through a medium determined by density and stffness Density and stffness=opposite Speed and stffness=same compressibility and elastcity= opposite of stffness
Speed of Sound (mm/µs) Air 0.33 Fat 1.45 Water 1.48 Soft Tissue 1.54 Blood 1.57 Muscle 1.58 Bone 4.0 PZT 4.08 Steel 5.0-6.0
GO OVER AMPLITUDE AND INTENSITY Pulse duraton- the tme from start a pulse to the end of the pulse determined by source can’t be changed .5 to 3 microseconds short the pulse=better the image
doesn’t change with depth
Pulse repetton period- tme from the start of one pulse to the start of the next determined by source can be change because can change “listening tme” Pulse repetton frequency- number of pulses that occur in 1 second determined by source can be changed because can change “listening tme” as depth increases, PRF decreases 1 to 10kHz Duty Factor- % of tme that the system is transmitting a pulse determined by the source can be changed-when change depth 0.001 to 0.01 If PRF increases, DF increases depth increases, DF decreases PRP increases, DF decreases PD increases, DF increases Spatal Pulse Length- distance from start of pulse to end of pulse determined by source and medium can’t be changed 0.1 to 1mm DETERMINES LONGITUDINAL RESOLUTION Intensity- the concentraton of energy in a sound beam determined only by sound source can be changed 1. 2. 3. 4. 5. 6.
SPTP SATP SPTA SATA SPPA SAPA
Bio-effects
SPTP= SPTA and SATP=SATA for contnuous wave
Decibels- rato for intensity I/Io 3 6 9 10
1/2 1/4 1/8 1/10
Attenuaton- decrease in intensity and amplitude as sound travels Greater the frequency/pathlength= greater attenuaton 1. absorpton 2. reflecton-depends on acoustc impedance RE ZE a. specular=smooth boundaries- WAVELENGTH IS SMALL IN RELATION TO BOUNDARY ROUGHNESS 3. scattering-BOUNDARY BETWEEN MEDIA HAS IRREGULARITIES (size similar/smaller than pulses wavelength a. Rayleigh-REFLECTOR IS SMALLER THAN PULSES WAVELENGTH higher frequency undergoes this Attenuaton coefficient- the amount of attenuaton per cm does not change with path length Half value layer- depth at which intensity is reduced 1/2 decreases when attenuaton coefficient increases, frequency increases depends on medium and frequency does not change with path length Impedance- resistance to sound travel through a medium characteristc of medium IRC + ITC= 100% Reflected +transmitted intensity= incident intensity IRC=RI/II x 100 ITC=TI/II With oblique incidence- reflecton angle=incident angle NOT SURE if reflecton will occur with oblique incidence????????????? Refracton- change in directon of wave propagaton-SNELL C mismatch and oblique Sin transmission angle Sin incidence angle
=
Prop speed 2 Prop speed 1
Distance= 0.77mm/microsecond x tme 13 microseconds for every cm in ST PAY ATTENTION TO WHETHER IT IS DEPTH OR DISTANCE Piezoelectric effect- materials create voltage when they’re mechanically deformed PZT is also called ceramic curie temperature- if material heated over this, loses its piezoelectricity- depolarizes Damping material advantages: Increases quality by improving LARRD Shortens SPL and PD Decreases numerical value of LARRD
Disadvantages: Decreases transducer sensitvity Increases Bandwidth Decreases Q factor
Bandwidth- the difference between the lowest and highest frequency emitted shorter the pulse the broader the BW Quality factor- degree of damping lower Q factor: o greater damping o pulse length is short o Bandwidth is wide o image is good For an unfocused transducer at the end of near zone: beam diamtere is ½ the transducer diameter and at 2 NZLs beam diameter is equal to transducer diameter...