Acoustics—Characteristics and measurements of field of pressure pulse lithotripters
Some standard content:
GB/T16407
This standard is formulated based on the actual test practice of the acoustic field characteristics of various models of pressure pulse lithotripters in China and with reference to the IECTC87 working group document \tJltrasonics--Prcssure pulse lithotripters—Characteristics of fields\. This standard was proposed by the Ultrasonic and Underwater Acoustic Sub-Technical Committee of the National Acoustic Standardization Technical Committee and is under the jurisdiction of the National Acoustic Standardization Committee. The drafting unit of this standard is the 721 Factory of China State Shipbuilding Corporation. Participating drafting units: Institute of Acoustics, Chinese Academy of Sciences, Wuhan Institute of Physics, Chinese Academy of Sciences and Suzhou Huaxing Medical Equipment Co., Ltd., China Aerodynamic Technology Development Center.
The main contributors of this standard are: Zheng Jinhong, Hua Wenhao, Gao Mingxian, Zhu Chunqing, Zhang Dejun and Du Qianxin. 1 Scope
National Standard of the People's Republic of China
Acoustics-Characteristies and measurements of field of pressure pulse lithotriplersGB/T 16407
This standard specifies the parameters and measurement methods for characterizing the acoustic field characteristics of extracorporeal pressure pulse lithotriplers. This standard is applicable to liquid-electric, piezoelectric and magnetic focusing medical extracorporeal pressure pulse lithotriplers. 2 Referenced Standards
The following standards contain provisions that constitute the provisions of this standard by reference in this standard: When this standard was published, the versions shown were valid. All standards are subject to revision. Parties using this standard should explore the possibility of using the latest versions of the following standards: GB/3947-1996 Acoustic Terminology
GH/T4128-1995 Standard Hydrophone (NEQTEC500: 1974/1EC866: 1987) GB/T15611-1995 High-frequency Hydrophone Calibration 3 Definitions
This standard adopts the following definitions.
3.1 Extracorporeal Lithotripsy Equipment that produces vocal pulses outside the human body to crush stones in the body. 3.2 Hydrophone (Underwater Microphone) Hydrophone (Underwater Microphone) Electroacoustic transducer used to receive underwater acoustic signals (see 6.82 in GB3947). Note: Due to differences in operating principles, characteristics and structures, there are hydrophones such as pressure, sound pressure, constant, finger, small electric, and optical fiber. 3.3 End-aft-closed sensitivity of a hydrophone (Mt.) The ratio of the output pressure at the end of the cable or connector to the instantaneous sound pressure of the plane wave field at the center of the hydrophone when the hydrophone is removed after the hydrophone is connected to a load with a specified input impedance. Unit: volt per Pascal [V/Pa]. 3.4 Sound pressure (p) The difference between the pressure in the medium and the static pressure when there is a sound wave. Unit: Pa [1.21 in GB3947]. 3.5 Sound intensity (I,) Sound intensity (sound energy flux density, sound powerdensity) At a certain point, the average sound energy passing through a unit area perpendicular to the specified direction within a unit time, unit, watt per square meter, W/m, (see GB394711.26).
3.6 Pressure pulsepressurcpulsc
The sound pressure pulse generated by the extracorporeal pressure pulse lithotripsy. 3.7 Sound pressure pulse waveformpressure pulsewavefarnApproved by the State Administration of Technical Supervision on May 27, 1996, implemented on December 1, 1996
GB/T 16407—1996
The instantaneous waveform of the instantaneous sound pressure at a specified position in the pressure pulse sound field, see Figure 1. 3.8 Pulse intensity integral (I) pulse-intensityintcgral In the pressure pulse sound field, the integral of the instantaneous sound intensity at a certain point over the duration of the entire pulse waveform, unit: joule [ear] per square meter, J/m. 3.9 Acoustic pulse energy (E) energy The integral of the pulse sound intensity over the spot cross section, unit: joule [ear]. 3.10 Positive sound pressure [compression pulse width (tp+) compressional pulse duralian The time difference between the two instantaneous sound pressures before and after the peak of the positive sound pressure pulse, whose sound pressure value is equal to 50% of the pulse peak value, unit: microsecond. See Figure 1.
3.11 Negative sound pressure [rare pulse width (r) rarefactional pulse durarian The time difference between the two instantaneous sound pressures before and after the peak of the negative sound pressure pulse, whose sound pressure value is equal to 50% of the pulse peak value, unit: microsecond. See Figure 1.
3.12 Rise time (t.) rise time
The time it takes for the front part of the positive sound pressure pulse to rise from 10% to 90% of the peak pressure. Unit: nanosecond, n. See Figure 1. 3.13 Positive sound pressure [compression peak (Pi) peak-positive acousticpressure The positive peak value of the acoustic pulse at a point in the pressure pulse sound field, that is, the maximum compression sound pressure. Unit: Pa [scal]. Pa, see Figure 13. {4 Negative acoustic pressure [sparse] peak (p_) peak-negative acoustic pressure The negative peak value of the acoustic pressure pulse at a point in the pressure pulse sound field, that is, the most sparse sound pressure, unit, Pa [scal], Pa, see Figure 1. 3.15 Beam axis beam axis
The line passing through the geometric center of the pressure pulse generator and the focus. 3.16 Focus focus
The position of the maximum positive acoustic pressure peak in the pressure pulse sound field. 3.17 Focal cross-sectional area (Ar) The area of the interface around the focus that is 6B lower than the maximum positive acoustic pressure peak (0B) in the plane perpendicular to the beam axis at the focus. Unit: square millimeter, mm.
3.18 Focal volume (V) The volume of space enclosed by the interface around the focal point that is 6 dB lower than the maximum positive sound pressure peak (0 dB), unit: cubic millimeter, m: 4 Symbol table
Ar——focal spot cross-sectional area:
E——acoustic pulse energy:
P-negative acoustic peak;
, positive sound pressure peak·
Iu—pulse intensity integral +
-rise time:
negative pulse width:
positive pulse width;
focal volume.
5 Measurement conditions
GB/T16407—1996
Figure 1 Diagram of sound pressure pulse
5.1 The measurement is carried out under the sound field conditions close to those used in actual operation, and the following parameters are recorded: driving voltage value of pressure pulse generator:
-discharge rate of pressure pulse generator;
ambient temperature.
5.2 The pressure pulse measurement is carried out in a measuring water tank with good acoustic coupling with the pressure pulse generator. The measuring water tank should be large enough to ensure the free field conditions required for measurement near the focal area. 5.3 Deaerated water at 25±5℃ should be used for measurement. Note: The simplest way to prepare deaerated water is to boil water and keep it for 15 minutes, then cool it to 54℃, fill the bottle, and tightly plug it with a rubber stopper with a glass tube. The glass tube is equipped with a hose, and clamped after filling with water. Cool and store it. Maintain partial vacuum. When in use, open the nozzle and fill it with water to prevent air from being carried in. 6 Measurement equipment
6.1 Measuring water tank
The measuring water tank should be firmly placed above the pressure pulse generator, and the upper and lower water media should be well coupled so that the pressure pulse energy can be well transmitted. The water tank should be large enough to ensure that the focal spot is about a few centimeters away from the reflection boundary. Pay special attention to the distance from the water surface and the distance between the focal spot and the reflection interface. The multiple reflections of the pressure pulse should not interfere with the measurement. The hydrophone should be placed with an appropriate mechanical bracket and placed on a positioning coordinate system so that the measurement position of the hydrophone can be adjusted in three directions relative to the focus. The precise positioning of the hydrophone at the focus position is very important. One axis (axis) of the positioning coordinate system is coaxial with the axis of the sound beam. The relative position of the hydrophone can be measured with an accuracy of ±0.1 mm. 6.2 Hydrophone
The calibration of the standard hydrophone for measurement shall be carried out in accordance with the provisions of GB15611. It is more appropriate to use a probe-shaped hydrophone, which should meet the following conditions:
a) The frequency response within 0.5-5MHz per octave should be less than ±3 dB, b) The dynamic range should be greater than 80MPa
c) The diameter of the sensitive surface should be less than 1.0mm
d) It should be able to ensure the completion of the entire test process. 6.3 Storage oscilloscope or transient recorder
GB/T16407-1996
To observe and measure the output signal of the hydrophone, a storage oscilloscope or transient recorder should be selected. The frequency limit of the instrument shall not be less than 100MHz, and the sampling frequency of analog/digital conversion shall be greater than 5/fr. From the recorded hydrophone output voltage waveform, the following parameters shall be measured and calculated: - positive sound pressure peak value, -1
negative sound pressure peak value, 1
rise time,
- positive pulse width, i.e. +!
- negative pulse width, i.e. -
sound pulse energy, 1
7 Measurement procedure
7.1 Spatial measurement
The spatial distribution of sound pressure shall be measured in the measurement hydrophone. By measuring the pressure pulse waveform at different positions near the focal spot, the spatial sound field distribution characteristics can be obtained, thereby giving the focal spot position, shape and size. The sampling space interval shall not exceed 0.5mm in the radial direction and 1mm in the axial direction). Determine the placement position of the hydrophone according to the provisions of Article 6.1. Then start the pressure pulse generator, observe the voltage waveform, and fine-tune the position of the hydrophone. When the voltage waveform has the highest positive pulse peak and the fastest rise time, it is the actual focal position. With this as the symmetry center, use the -3-2 coordinate positioning system to measure the spatial distribution characteristics of the sound pressure, or measure the width of the 6dB isobaric line. First perform the : axis scan to determine the focal spot position, and then perform other measurements.
Spatial distribution can also be quickly displayed by placing pressure-sensitive paper on the appropriate position tube to quickly display the approximate position of the focus. 7.1.1 Two-dimensional focal spot of positive sound pressure peak
Measure the change of the positive sound pressure peak on the focal spot along the axis and the axis, and you can get the focal spot map in two directions. Or measure the positive sound pressure peak on the -2 or - plane, and you can make a one-dimensional isobaric line map. If the deviation of the :6dB width in direction 1 is not greater than 10%, the focal spot is considered to be symmetrical, otherwise it is asymmetrical. At this time, the selection of ~3 direction should be taken in the maximum and minimum directions. 7.1.2 Focal volume
Measure the peak sound pressure value and the width and length of the focal column. The volume enclosed by this interface is the focal column volume, which reflects the spatial distribution of the pressure pulse peak. 7.2 Time domain measurement
The hydrophone is placed at the focal position with a deviation of no more than ±0.5 mm. Use an oscilloscope or transient recorder to measure and record the pressure pulse waveform. The following parameters are read and derived from the time domain waveform. 7.2. 1 Positive and negative sound pressure peaks
According to the polarity and voltage waveform of the hydrophone sensitive element, read the voltage values of the positive sound pressure peak and the negative sound pressure peak respectively, and divide them by the load sensitivity at the end of the hydrophone cable to obtain the corresponding positive and negative sound pressure peaks. The unit of the positive sound pressure pulse peak is expressed in megapascals (MPn). Under normal circumstances, the positive sound pressure peak appears first, followed by the negative sound pressure peak, and the positive sound pressure peak is much larger than the negative sound pressure peak. 7.2.2 Positive and negative sound pressure pulse width and rise time Read the negative sound pressure pulse width based on the pressure pulse waveform. Read the positive pulse rise time at the leading edge of the positive sound pressure pulse waveform. 7.3 Calculation of acoustic pulse energy
The acoustic pulse energy in the focal cross section can be calculated from the results of 7.1 and 7.2. The acoustic pulse energy base is given by the following formula: E
p*(re,t)dtds
GB/T164071996
-Instantaneous sound pressure at (r,) and time t Where: (r.0)-www.bzxz.net
S-Focal cross section under spatial polar coordinates r9 Z.-Characteristic acoustic impedance of water (1.5×10°Pa.s/m) For a circularly symmetric beam
E-2 elements
Where: T(r)
Focal cross section radius
To estimate E, the average value of the measurement results along two orthogonal diameter directions and four radial directions should be used. Formula (2) is approximately calculated as: E = o. 5(I + I. - In formula (2), it is assumed that N + 1 points are taken as radial measurement points between r = and = R, where r =, n = R, and the pulse intensity integral at point rr is m
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