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GB/T 19890-2005 PDF in English


GB/T 19890-2005 (GB/T19890-2005, GBT 19890-2005, GBT19890-2005)
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GB/T 19890-2005: PDF in English (GBT 19890-2005)

GB/T 19890-2005
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 17.140.01
A 59
Acoustics - High intensity focused ultrasound (HIFU)
measurements of acoustic power and field characteristics
ISSUED ON: SEPTEMBER 09, 2005
IMPLEMENTED ON: APRIL 01, 2006
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3 
Introduction ... 4 
1 Scope ... 5 
2 Normative references ... 5 
3 Terms and definitions... 5 
4 General ... 10 
5 Requirements of measurement system ... 11 
5.1 Requirements for radiation force balance system ... 11 
5.2 Requirements for hydrophone measurement system ... 11 
5.3 Requirements for measurement water tank ... 13 
5.4 Requirements for water and degassing ... 16 
5.5 Requirements for high-intensity focusing system under test ... 16 
5.6 Requirements for measuring instruments ... 16 
6 Sound power measurement methods ... 17 
6.1 Measurement of radiation force ... 17 
6.2 Calculation of sound power ... 17 
7 Measurement of sound field characteristics ... 20 
7.1 Measurement preparations ... 20 
7.2 Alignment of hydrophone ... 20 
7.3 Measurement steps ... 20 
References ... 25 
Acoustics - High intensity focused ultrasound (HIFU)
measurements of acoustic power and field characteristics
1 Scope
This standard specifies the measurement conditions and methods, for sound power and
sound field characteristic parameters of high-intensity focused ultrasound (HIFU) in
water, within the frequency range of 0.5 MHz ~ 5 MHz.
This standard applies to high-intensity focused ultrasound systems.
Note 1: This standard uses SI units. In some parameter descriptions, such as the beam area
parameter and the sound intensity parameter, it may be more convenient to use other units. For
example: The unit of sound beam area can be cm2; the unit of sound intensity can be W/cm2 or
kW/cm2.
Note 2: The measurement range specified in this standard: the power is not more than 500 W;
the sound intensity is not more than 5000 W/cm2.
2 Normative references
The provisions in following documents become the provisions of this Standard through
reference in this Standard. For the dated references, the subsequent amendments
(excluding corrections) or revisions do not apply to this Standard; however, parties who
reach an agreement based on this Standard are encouraged to study if the latest versions
of these documents are applicable. For undated references, the latest edition of the
referenced document applies.
GB/T 3947-1996 Acoustical terminology
3 Terms and definitions
The terms and definitions, as determined in GB/T 3947-1996, as well as the following
terms and definitions, apply to this standard.
3.1
High intensity focused ultrasound (HIFU)
Using methods such as acoustics and electronics, to converge the ultrasonic beam
5 Requirements of measurement system
5.1 Requirements for radiation force balance system
5.1.1 Target requirements
This standard recommends the use of an absorbing target: the sound pressure reflection
coefficient is required to be ≤ 5%; the sound pressure transmission coefficient is less
than 10%. The area of the target is large enough, that its diameter or minimum
dimension is greater than 1.5 times the -26 dB beam width, in the intercepted plane.
5.1.2 Requirements for target support (or suspension) system
The support of the target shall have sufficient stability; the horizontal displacement of
the target during the measurement shall be small enough, to not affect the measurement
results. Keep the target surface perpendicular to the beam axis.
5.1.3 Force measuring system
The force measuring system can use an electronic balance or a force measuring sensor
system. The measurement precision is required to be better than 10-3 N.
5.2 Requirements for hydrophone measurement system
5.2.1 Requirements for hydrophones
5.2.1.1 Requirements for hydrophone sensitivity
The free-field voltage sensitivity, at the end of the hydrophone cable, is not less than 10
nV/Pa.
5.2.1.2 Bandwidth requirements for hydrophones
The fluctuation of the hydrophone's sensitivity shall be within ±6 dB, when changing
in the 2-octave range of the acoustic operating frequency.
5.2.1.3 Directivity requirements for hydrophones
At the acoustic operating frequency, the main beam width of sound pressure -6 dB in
the direction of the acoustic axis is ≥ 70°.
5.2.1.4 Determination of effective radius of hydrophone
Measure θ-3 dB and θ-6 dB. Use formulas (2) and (3), to calculate α-3 dB and α-6 dB. Use
formula (4), to calculate the arithmetic mean of the two, which is the effective radius α
Figure 4 -- Configuration of the HIFU sound field with beam down, as measured
by the hydrophone method
5.4 Requirements for water and degassing
5.4.1 Water quality requirements
It is required to use purified water or tap water after purification.
5.4.2 Degassing requirements
The water in the water tank must be degassed, to meet the requirement of oxygen
content ≤ 4 mg/L.
Note: The water after degassing shall be strictly prevented from shaking, stirring,
spraying, or other operations, during the filling process, so as to avoid the re-
dissolving of air causing the oxygen content to exceed the standard.
5.4.3 Water temperature requirements
The water in the water tank is kept at (23 ± 3) °C.
5.5 Requirements for high-intensity focusing system under test
5.5.1 Requirements for the frequency stability of the high-intensity focusing
system under test
After preheating for 15 min, the frequency stability reaches 10-4/4 h.
5.5.2 Requirements for the electrical power stability of the high-intensity focusing
system under test
After 15 min of preheating, the electrical power stability reaches 10%/4 h.
5.5.3 Requirements of the hydrophone method for the measurement working state
of the high-intensity focusing system under test
In order to ensure the safety and service life of the measuring device, the device under
test is required to have a dedicated pulse measurement working state. This state requires:
the pulse duration is less than or equal to 100 µs; the pulse repetition frequency is less
than 1 kHz.
5.6 Requirements for measuring instruments
The frequency range of the oscilloscope shall be higher than 10 times the sound
operating frequency; the DC vertical gain accuracy shall be ±2% full scale. It has
storage and spectrum analysis functions.
6 Sound power measurement methods
6.1 Measurement of radiation force
The radiation force is measured, using the devices as shown in Figures 1 and 2. In order
to avoid the influence of nonlinearity and acoustic flow on the radiation force
measurement, the axial position of the absorption target shall be set, near the sound
source away from the sound focal point. The absorption target shall be perpendicular to
the sound axis; the bullseye shall be aligned with the sound axis; the distance from the
transducer or the center of the transducer surface should not be greater than 0.7 times
the sound pressure focal length. Before measurement, the absorption target shall be
soaked for 30 minutes; the instrument shall be preheated for 15 minutes.
In order to reduce the influence of thermal drift, it shall measure the short-term (within
2 ~ 3 s) stable value of the balance indication value, when ultrasonic waves are applied
and when ultrasonic waves are interrupted; the difference between the two is the ratio
m -- of the normal radiation force F on the absorption target TO the gravity of
acceleration g. The unit is kg.
Note: When the lever mechanism is used, the force measured by the electronic
balance shall be converted into the actual force on the absorption target, by
calibrating the force arm ratio.
During the measurement, it shall observe the surface of the absorption target and the
transducer at any time; remove the small bubbles appearing on it in time.
6.2 Calculation of sound power
6.2.1 Acoustic power calculation of spherical focusing unit transducer
Where:
P - Sound power, in watts (W);
F - The normal radiation force on the absorption target, in Newton (N);
c - The speed of sound of water, in meters per second (m/s);
Position the hydrophone at the sound focal point, to measure the maximum positive
sound pressure p+ and the maximum negative sound pressure p-:
Where:
U+max - The positive peak value of the output sound pressure signal voltage of the
hydrophone, at the sound focus, in volts (V);
U-max - The negative peak value of the output sound pressure signal voltage of the
hydrophone, at the sound focal point, in volts (V);
ML - The load sensitivity of the hydrophone at free-field cable end, in volts per
pascal (V/Pa).
7.3.1.2 Measurement of acoustic operating frequency (fawf)
Input the instantaneous sound pressure waveform signal, which is measured by the
hydrophone, into the oscilloscope. Use the oscilloscope or other spectrum analyzer, to
measure the sound operating frequency.
7.3.1.3 Measurement of spatial peak intensity (Isp)
Calculate and derive the sound intensity Isp, from the root mean square value of the
sound pressure, during the pulse duration, which is measured at the sound focus:
Where:
Urms,max - The root mean square value of the output voltage of the hydrophone, for
the duration of the pulse, at the sound focal point, in volts (V);
ρ - The density of water, in kilograms per cubic meter (kg/m3);
c - Speed of sound in water, in meters per second (m/s).
7.3.1.4 Temporal average intensity spatially averaged over the -6 dB beam area
Let the hydrophone perform a two-dimensional linear step scanning, at a step Δx = Δy
≤ 0.1 λawf, in the sound pressure focal plane. The measured sound pressure RMS in the
plane is greater than or equal to half of the sound pressure RMS Prms6i, for all points
which is half of maximum sound pressure RMS Prms.max. It shall calculate Isal, using the
following formula:
Where:
Urms6i - The rms value of the output voltage, at the spatial point, where the rms
voltage of the ith sound pressure signal as measured by the hydrophone, in the sound
pressure focal plane, is greater than or equal to half the rms value of the maximum
sound pressure signal voltage, in volts (V);
N - The number of all points in the sound pressure focal plane, where the rms sound
pressure measured by the hydrophone is greater than or equal to half of the
maximum sound pressure rms value.
7.3.2 Measurement of focus parameters
7.3.2.1 Measurement of full width at half (pressure) maximum, FWHM
In the process of measuring Isal, the Urms (xi, yi, Fpres) distribution in the sound pressure
focal plane is determined by the method of hydrophone scanning and the coordinate
positioning system; the maximum size Δdr of the -6 dB focal region is taken.
Scan the hydrophone on the main sound axis (z-axis), to measure the distance Δdz,
between two points whose sound pressure RMS is equal to half the maximum sound
pressure RMS, before and after the sound pressure focal point.
7.3.2.2 Measurement of maximum side lobe level (Lsm)
Use a method similar to measuring Δdr, to find the second maximum (sub-maximum)
Prms,sm of the sound pressure RMS value, in the distribution of Urms (xi, yi, Fpres) in the
sound pressure focal plane. Use the following formula, to calculate the maximum side
lobe level Lsm:
7.3.2.3 Measurement of axial secondary maximum level (Lasm)
In a similar way to measuring Δdz, scan the hydrophone along the z-axis, to measure
the second maximum sound pressure rms on the z-axis, Prms,asm. Calculate the axial
secondary maximum level, by the following formula:
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.