ssd-_alpha_10_manual__number_2_mn1-5205_rev_18_sept.pdf
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MN1-5205 Rev.18
ULTRASOUND DIAGNOSTIC
INSTRUMENT
SSD-α10
Manual Number : MN1-5205
Rev.18
0123
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MN1-5205 Rev.18
VS-FlexGrid Pro
Copyright(C)1999 Videosoft Corporation
Portions of this software are based in part on the work of the Independent JPEG Group.
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MN1-5205 Rev.18
Safety alert symbols
Safety alert symbols
The four indications [Danger], [Warning], [Caution] and [Note] used on this instrument and in this instruction manual have the following meaning.
Danger
Indicates an imminently hazardous situation which, if not avoided, will result in death or serious injury.
A warning message is inserted here.
Warning
Indicates a potentially hazardous situation which, if not avoided, could result in death or serious injury.
A warning message is inserted here.
Caution
Indicates a potentially hazardous situation which, if not avoided, may result in minor or moderate injury.
A caution message is inserted here.
Note
Indicates a strong request concerning an item that must be observed in order to prevent damage or deterioration of the instrument and also to ensure that it is used efficiently.
An explanatory text is inserted here.
Classification of SSD-α10
• Protection against electric shock: Class I medical electrical equipment
• Applied parts:Type BF applied parts
• Protection against defibrillator emissions: Not compatible with defibrillator-proof applied parts
• Protection against harmful ingress of water or particulate matter: Ordinary protection (IPX0)
• Level of safety for use in air and flammable anesthetic gas, or in oxygen/nitrous oxide and flammable anesthetic
gas:
This instrument is not suitable for use in air and flammable anesthetic gas, or in oxygen/nitrous oxide and flammable anesthetic gas.
• Operation mode: Continuous operation
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MN1-5205 Rev.18
CONTENTS
This book consists of two separate volumes.
These two volumes have the same table of contents and the index respectively.
1. Precautions for Use
1-1.
1-2.
Purpose of Use ............................................................................................................................................. 1-1
1-1-1.
Precautions concerning acoustic power ....................................................................................... 1-2
1-1-2.
Use with an ultrasound contrast agent ......................................................................................... 1-2
1-1-3.
Use with a general pharmaceutical .............................................................................................. 1-2
1-1-4.
Use with Other Medical Devices ................................................................................................. 1-3
Classification................................................................................................................................................ 1-4
1-2-1.
According to the type of protection against electric shock:......................................................... 1-4
1-2-2.
According to the degree of protection against electric shock: ..................................................... 1-4
1-2-3.
According to the degree of protection against harmful ingress of water ..................................... 1-4
1-2-4.
According to the degree of safety of application in the presence of a flammable anaesthetic mixture
with air or with oxygen or nitrous oxide1-4
1-2-5.
According to the mode of operation............................................................................................. 1-4
1-3.
Safety ........................................................................................................................................................... 1-5
1-4.
Environmental Conditions ........................................................................................................................... 1-6
1-4-1.
Working environment .................................................................................................................. 1-6
1-4-2.
Storage environment and moving / transport environment.......................................................... 1-6
1-5.
Power Requirements .................................................................................................................................... 1-7
1-6.
Electromagnetic compatibility ..................................................................................................................... 1-8
1-7.
1-6-1.
The prevention of electromagnetic wave disorders ..................................................................... 1-8
1-6-2.
The guideline of electromagnetic compatibility .......................................................................... 1-9
1-6-3.
Guidance and declaration directive concerning electromagnetic emission ................................. 1-9
1-6-4.
Restrictions for use..................................................................................................................... 1-10
1-6-5.
Essential performance ................................................................................................................ 1-10
1-6-6.
Guidance and Declaration directive concerning electromagnetic immunity ............................ 1-12
1-6-7.
Guidance and Declaration directive concerning electromagnetic immunity
(conduction RF and emission RF).............................................................................................. 1-13
Safety Instructions for Connecting Network Devices................................................................................ 1-15
1-7-1.
1-8.
Electrical safety Instructions for Connecting Network Devices ................................................ 1-15
Other precautions ....................................................................................................................................... 1-15
2. Meaning of Symbols, Indications and Terms
2-1.
Symbols and Indications .............................................................................................................................. 2-1
2-1-1.
Safety alert symbols ..................................................................................................................... 2-1
2-1-2.
Other symbols and indications ..................................................................................................... 2-2
2-2.
Meaning of Terms........................................................................................................................................ 2-4
2-3.
Position of Labels......................................................................................................................................... 2-5
2
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MN1-5205 Rev.18
3. Installation Method
3-1.
3-2.
Environmental Conditions of Installation Location ..................................................................................... 3-1
3-1-1.
Working environment................................................................................................................... 3-1
3-1-2.
ESD prevention procedures .......................................................................................................... 3-2
3-1-3.
Installation location ...................................................................................................................... 3-3
3-1-4.
Power source................................................................................................................................. 3-3
Installing the Instrument............................................................................................................................... 3-4
3-2-1.
3-3.
Connecting a Probe to the Instrument .......................................................................................................... 3-5
3-3-1.
3-4.
Method of connecting an electronic type probe ........................................................................... 3-5
Connecting Options to the Instrument.......................................................................................................... 3-7
3-4-1.
3-5.
Installation procedure ................................................................................................................... 3-4
Connecting the instrument to the physiological signal terminal .................................................. 3-7
Connecting with Other instrument ............................................................................................................... 3-9
4. Specifications and Name of Each Part
4-1.
Specifications................................................................................................................................................ 4-1
4-2.
Name and Function of Each Part.................................................................................................................. 4-5
4-2-1.
Exterior drawing and name of each part....................................................................................... 4-5
4-2-2.
Front panel .................................................................................................................................... 4-7
4-2-3.
Rear panel ..................................................................................................................................... 4-9
4-2-4.
Caster .......................................................................................................................................... 4-10
4-2-5.
Viewing monitor......................................................................................................................... 4-11
4-2-6.
Physiological signal Connector .................................................................................................. 4-12
5. COMPOSITION
5-1.
Standard composition ................................................................................................................................... 5-1
5-2.
Options.......................................................................................................................................................... 5-2
5-2-1.
Peripheral instrument.................................................................................................................... 5-2
5-2-2.
Table of optional probes (EU nations).......................................................................................... 5-5
5-2-3.
Table of optional probes (Outside EU)......................................................................................... 5-9
6. Principle of Operation
6-1.
Principle of Operation .................................................................................................................................. 6-1
7. Cleaning and Sterilizing
7-1.
7-2.
Method of Cleaning and Sterilizing the Instrument ..................................................................................... 7-1
7-1-1.
Cleaning that is carried out at the end of each day ....................................................................... 7-1
7-1-2.
Cleaning that must be carried out once a week ............................................................................ 7-1
7-1-3.
Cleaning that must be carried out once a month........................................................................... 7-2
7-1-4.
Cleaning that is carried out as necessary after use ....................................................................... 7-2
Cleaning and Sterilizing Conditions............................................................................................................. 7-4
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MN1-5205 Rev.18
8. Preparations for Use
8-1.
8-2.
Starting Inspection ....................................................................................................................................... 8-1
8-1-1.
External Inspection....................................................................................................................... 8-1
8-1-2.
Checking and Replacing Consumables........................................................................................ 8-1
8-1-3.
Cleaning, disinfecting and Sterilizing Probes .............................................................................. 8-1
8-1-4.
Operation check ........................................................................................................................... 8-2
Preparations for Use..................................................................................................................................... 8-2
8-2-1.
Adjusting the monitor .................................................................................................................. 8-2
8-2-2.
Adjusting the height of the operation panel ................................................................................. 8-5
8-2-3.
Adjusting the position of the operation panel .............................................................................. 8-6
8-2-4.
Adjusting the Angle and Position of the Monitor ........................................................................ 8-7
9. Screen Display
9-1.
Character Display......................................................................................................................................... 9-1
9-1-1.
9-2.
Automatic display area................................................................................................................. 9-2
Graphic Display ........................................................................................................................................... 9-4
10. After Using the Instrument
10-1.
Switching OFF the Instrument................................................................................................................... 10-1
10-1-1.
10-2.
10-3.
Procedure for switching OFF the instrument ............................................................................. 10-1
Cleaning the Instrument ............................................................................................................................. 10-1
10-2-1.
Cleaning that is carried out at the end of each day .................................................................... 10-1
10-2-2.
Cleaning that must be carried out once a week.......................................................................... 10-2
10-2-3.
Cleaning that is carried out as necessary after use..................................................................... 10-2
State of the Instrument and Accessories .................................................................................................... 10-2
11. Storing the Instrument
11-1.
Preparations for Storing the Instrument ..................................................................................................... 11-1
11-1-1.
11-2.
Storage preparation procedure ................................................................................................... 11-1
Storage Location and Environmental Conditions ...................................................................................... 11-2
11-2-1.
Storage environment .................................................................................................................. 11-2
12. Moving the Instrument
12-1.
12-2.
Instrument
12-3.
Precaution for moving................................................................................................................................ 12-1
State of the Instrument and Accessories Before Moving the
12-1
12-2-1.
Moving preparation.................................................................................................................... 12-1
12-2-2.
Moving procedure ...................................................................................................................... 12-3
Inspection Before Re-use ........................................................................................................................... 12-3
13. Safety Inspection
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MN1-5205 Rev.18
13-1.
13-2.
Maintenance and Inspection ....................................................................................................................... 13-1
13-1-1.
Weekly inspection ...................................................................................................................... 13-1
13-1-2.
Monthly inspection ..................................................................................................................... 13-1
13-1-3.
Issues that require caution about electrostatic discharge (ESD)................................................. 13-2
Safety Inspection ........................................................................................................................................ 13-3
13-2-1.
13-3.
Periodic Safety Inspection Procedure, and Measurement .......................................................... 13-3
Checking the Measurement Accuracy........................................................................................................ 13-6
13-3-1.
Inspection method....................................................................................................................... 13-6
13-3-2.
Evaluation of results ................................................................................................................... 13-7
13-3-3.
Inspection Procedure .................................................................................................................. 13-8
13-4.
Measurement Accuracy Inspection Data Sheet ........................................................................................ 13-11
13-5.
ULTRASOUND DIAGNOSTIC INSTRUMENT Safety Inspection Data Sheet.................................... 13-14
14. Troubleshooting
14-1.
Trouble list.................................................................................................................................................. 14-1
14-2.
Messages..................................................................................................................................................... 14-2
14-2-1.
Message ...................................................................................................................................... 14-3
14-2-2.
Assistant Messages ..................................................................................................................... 14-9
15. DISPOSAL the Instrument
15-1.
Precaution of disposal................................................................................................................................. 15-1
15-2.
Disposal of Old Electrical & Electronic Instrument................................................................................... 15-1
16. Probe use and care
16-1.
16-2.
Application use ........................................................................................................................................... 16-1
16-1-1.
Contra indication ........................................................................................................................ 16-1
16-1-2.
Warnings..................................................................................................................................... 16-1
16-1-3.
External Inspection ..................................................................................................................... 16-1
Connecting a Probe to the Instrument ........................................................................................................ 16-2
16-2-1.
Method of connecting an electronic type probe ......................................................................... 16-2
16-3.
About activating of probe ........................................................................................................................... 16-4
16-4.
Usable probe ............................................................................................................................................... 16-5
16-4-1.
16-5.
Use of probe................................................................................................................................ 16-5
16-4-2.
Specifications.............................................................................................................................. 16-7
16-4-3.
Clinical Measurement Accuracy............................................................................................... 16-10
16-4-4.
Clinical Measurement Range.................................................................................................... 16-11
Handling and maintenance of probe......................................................................................................... 16-13
16-5-1.
Caution about handling............................................................................................................. 16-13
16-5-2.
Precautions for performing a puncture operation ..................................................................... 16-14
16-5-3.
Cleaning of probe ..................................................................................................................... 16-15
16-5-4.
Disinfection of probe ................................................................................................................ 16-15
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MN1-5205 Rev.18
16-6.
16-5-5.
Sterilization of probe................................................................................................................ 16-15
16-5-6.
Probe cover............................................................................................................................... 16-15
16-5-7.
Maintenance and Inspection..................................................................................................... 16-15
Transesophageal Echocardiogram probe ................................................................................................. 16-16
16-6-1.
Temperature control System .................................................................................................... 16-16
16-6-2.
Monitoring Surface Temperature............................................................................................. 16-16
17. Acoustic Output Safety Information
17-1.
About acoustic output index ...................................................................................................................... 17-1
17-1-1.
Mechanical index (MI)............................................................................................................... 17-1
17-1-2.
Thermal index (TI)..................................................................................................................... 17-1
17-2.
Ultrasound wave, interaction between vital tissues ................................................................................... 17-3
17-3.
Possible Biological Effects ........................................................................................................................ 17-4
17-4.
17-3-1.
Mechanical effects ..................................................................................................................... 17-4
17-3-2.
Thermal ...................................................................................................................................... 17-5
Derivation and Meaning of MI/TI ............................................................................................................. 17-6
17-4-1.
Introduction ................................................................................................................................ 17-6
17-4-2.
Mechanical index (MI)............................................................................................................... 17-6
17-4-3.
Thermal index (TI)..................................................................................................................... 17-7
17-5.
Setting condition influencing device output .............................................................................................. 17-9
17-6.
Recommendation on ALARA (As Low As Reasonably Achievable)..................................................... 17-10
17-7.
Default Setting ......................................................................................................................................... 17-11
17-8.
Protocol for calculating the measurement uncertainties .......................................................................... 17-12
17-9.
Reference ................................................................................................................................................. 17-21
17-10. Acoustic Output Tables............................................................................................................................ 17-22
17-10-1. Acoustic Output Measurements ............................................................................................... 17-22
17-10-2. Convex Sector Probe................................................................................................................ 17-25
17-10-3. Phased Array Sector Probe..................................................................................................... 17-103
17-10-4. Linear Probe ........................................................................................................................... 17-175
17-10-5. Combination Probe................................................................................................................. 17-247
17-10-6. 3D Probe................................................................................................................................. 17-260
17-10-7. Mechanical Radial Probe ....................................................................................................... 17-278
17-10-8. Mechanical Annular Array Sector Probe .............................................................................. 17-282
17-10-9. Independent Probe.................................................................................................................. 17-284
17-10-10.Ultrasonic Gastrovideo Scope................................................................................................ 17-288
17-10-11.Ultrasonic Bronchofiber videoscope...................................................................................... 17-324
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MN1-5205 Rev.18
17-1.About acoustic output index
17. Acoustic Output Safety Information
17-1. About acoustic output index
With this device, an output index about possibility of influence (biological influence) to a living body is displayed.
The displayed indexes are the four kinds. Of these, one kind shows a mechanical influence to the living body, and
other three show the influence of heat to the living body.
17-1-1. Mechanical index (MI)
A mechanical index (MI) is an index indicating possibility of mechanical influence to a living body.
The mechanical influence to the living body is caused by the compression of air bubbles when a supersonic
compressed wave is passing through the whole organization. With the passing through, an interlocking movement
(the flow) produces pressure to the circumference with discharging energy by cavitation.
Because the thermal effect is not so significant in the mode of B, B/M, and M respectively, the mechanical index
becomes important.
The mechanical index is displayed on all modes.
In other imaging modes, the issue of thermal effect is also important.
17-1-2. Thermal index (TI)
17-1-2-1. Soft tissue Thermal Index (TIS)
The soft tissue thermal index is an index to show the possibility of a temperature elevation when an ultrasound beam
is passing through soft tissue or focusing on application subjects ( heart, embryo, and abdominal scans).
TIS can be displayed on all modes.
17-1-2-2. Bone Thermal index(TIB)
Bone thermal index (TIB) is an index to show the possibility of a temperature elevation in applications (scans for an
embryo of the second three months of pregnancy or the third three months of pregnancy, and fonticuli cranii of the
neonatal head), which are forming a focus close to bones after passing through soft tissues in front.
TIB can be displayed on all modes and at the time of transducer use. In addition, with scan modes including B mode
imaging, the value of TIB becomes equal to the value of TIS.
17-1-2-3. Cranial Bone Thermal index (TIC)
Cranial bone thermal index(TIC) is an index to show the possibility of a temperature elevation in an application
(head inspection of adult and infant) that an ultrasound beam passes existing bones in the vicinity of body surface
(the part where a beam enters to the body).
TIC can be displayed on all modes.
The border between a safe level and a danger level of biological effects is important for the operators.
WFUMB have issued some indicators.
This section consists of 334 pages.
17-1
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MN1-5205 Rev.18
17-1.About acoustic output index
For example, "you should think that temperature rise more than 4 degrees Celsius in five minutes is potentially dangerous for embryos and embryo tissues" and so on.
On the other hand, the index gives us a display of condition more susceptible to thermal effects and(or) mechanical
effects related to the living body system in comparison with other parameters such as the sound pressure or its intensity.
For example, we suggest that it is better to avoid TI value with more than a certain upper limit range (more than 1.0)
in obstetrics use.
Such a limit gives us a rational safety margin in consideration of the advice of WFUMB mentioned above.
When specific clinical consequences are not provided with lower values, it may justify to increase the output, nevertheless, should pay special attention for limiting exposure time. When examining an embryo whose mother is running with a fever, you should be particularly careful for a high TI value in order to avoid unnecessary heat load.
The following list shows an indication of significance of MI/TI in clinical use by IEC 60601 - 2-37.
Relative importance of keeping a sound output index low at various examinations
Mechanical index (MI)
It is more important
It is not so important
• It uses contrast media
• When there is no gas existing :
• Heart scanning
(pulmonary irradiation)
For example, most tissues imaging
• Abdominal scanning (enteric gas)
Thermal index (TI)
• Scanning in the first trimester
• Fetal skull and spinal cord
• Tissue with good perfusion
For example, Liver and spleen
• The patient who runs a fever
• Heart scanning
• Tissue with little perfusion
• Blood vessel scanning
• If ribs or bones are irradiated: TIB
Caution
It has been thought that cavitation is hard to be generated with the frequency of ultrasonic diagnostic instrument because it is as high as several MHz to several dozen MHz.
However, according to the animal experiment, it is reported that the tissues where originally air bubbles exist
such as lung and bowel are easy to receive the damage of petechia in low sound pressure.
As for the fetal pulmonary tissues which do not do pulmonary respiration, there is a report of supersonic
experiment that they are hard to be affected.
From these facts, it is requested to be careful for using contrast agent to inject air bubbles intentionally.
17-2
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MN1-5205 Rev.18
17-2.Ultrasound wave, interaction between vital tissues
17-2. Ultrasound wave, interaction between vital tissues
Ultrasound introduces energy into the body. This energy, as the same as sound, generates a physical pressure wave.
Typical frequencies range from 3 MHz (megahertz,or millions of cycles per second) to 10 MHz.
In this device, ultrasound images are produced with "receiving" a part of the energy of the transmitted ultrasound
wave by the transducer, which energy is reflected from the irradiated internal body system. As for the reflected
acoustic wave, the most of the energy is absorbed by the tissues and only a fraction of it is reflected.
In ultrasound irradiation, the energy absorbed in the body system may cause some processes within tissues.
These processes are classed as mechanical and thermal process, respectively.
Mechanical effects are due to the pressure waves causing mechanical or physical movement of the tissues and tissue
components. These components such as cells, fluids, etc., oscillate. If conditions are favorable, it is possible that
these oscillations may affect the structure or function of living tissues. At present, mechanical effects are thought to
be instantaneous in nature, and depend roughly on the intensity of the ultrasound pulse.
An extreme example of the mechanical effects of ultrasound is shock - wave lithotripsy, where focused ultrasound
waves are used to break apart kidney stones.
The second type of effect, the thermal effect, is due to the tissues absorbing the energy of the ultrasound beam.
When an acoustic wave transmits through the body system, the energy of a sound wave is scattered and absorbed by
the tissues. Unlike mechanical effects, thermal effects are thought to be temporal in nature, and related to a tissue
volume, perfusion rate, exposure time, and duty factor (a fraction of time that the transducer actually transmits).
Among the physiological effects known to occur due to tissue heating are cell death and increased chance for fetal
anomalies.
17-3
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MN1-5205 Rev.18
17-3.Possible Biological Effects
17-3. Possible Biological Effects
17-3-1. Mechanical effects
Mechanical effect is generated by the oscillation of a pressure wave when a ultrasound wave is transmitted to the
body system.
This pressure wave acts on microscopic gas bubbles and other “nucleation sites” in tissue.
These nucleation sites, although presently poorly understood, are believed to serve as starting points for the development of gas bubbles. Because gas is much more compressible than fluid, the microscopic gas bubbles can expand
and contract greatly in comparison to the immediately surrounding tissues and fluid. The large change in size may
damage tissues.
There are two categories of mechanical effects: Steady-state and Transient.
Steady - state effects arise from the repeated expansion and contraction of the micro bubbles in response to the varying pressures in ultrasound pulses. This oscillation can lead to a phenomenon known as “micro streaming”, where
the oscillation of gas bubbles in tissue leads to motion in the fluid around the gas bubbles. This phenomenon has
shown that micro streaming has the possibility of causing disruption of cell membranes.
Transient mechanical effects occur when the pressure change due the oscillating ultrasound wave causes a gas
bubble to expand and then implode violently in a process called “cavitation”. Although this phenomenon occurs on
the microscopic level, it has been demonstrated to produce extremely high temperatures and pressures in the immediate vicinity, which can lead to cell death.
The potential for mechanical effects is related to the peak negative (rarefactional) pressure of the ultrasound wave
and its frequency. Higher values of negative pressure (if amplitude wave becomes large) increase the potential for
mechanical effects. Higher frequencies decrease the potential for mechanical effects.
At this time, there is no solid evidence that cavitation occurs in human tissue with the output intensities available on
current diagnostic ultrasound instrument. However, mechanical effects are theoretically possible.
17-4
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17-3.Possible Biological Effects
17-3-2. Thermal
Thermal effects occur over longer periods of time, where absorption of the ultrasound energy results is heating of
tissues. Excessive heating can lead to disruptions in cellular processes and structures, specially in developing fetal
tissues. As stated above, the energy which is producing image by receiving reflected energy from the body’s internal
tissues by the transducer is very limited out of the total energy transmitted to the body system. The rest of the energy
must be absorbed by the tissues. With this absorption, heat is developed mainly in two areas such as a part irradiated
by the beam and a part received a concentrated beam.
Because of difference in their physical properties, different tissues absorb ultrasound energy at different rates. Absorption is affected by the ultrasonic power (energy per unit of time), the volume of tissues involved and its perfusion
rate, or the amount of blood flow through the target tissues. Bone tissue, with its higher density and lower perfusion
than soft tissues, absorbs more ultrasound energy. Bone tissue at the surface will absorb the largest portion, and has
the highest susceptibility to heating from ultrasound exposure.
Bone tissue not at the surface, but at the focus point of the beam, will also absorb a higher portion of energy.
Soft tissues absorbs the least.
Because tissue absorbs ultrasound energy at different rates, a single model to describe all of the different properties
of different tissues is not available.
Currently, there are three different models to describe thermal effects in tissue. The three models are 1) Soft tissues
2) Bone at focus and 3) Bone at the surface.
The type of ultrasound beam also influences the potential for thermal effects. In non-scanning mode (example: Dmode), as the position and direction of an ultrasound beam converging energy are fixed, the ultrasound energy of
high-density occurs for a comparatively small tissue volume. This tends to increase the thermal effects in the tissue.
In addition, in B mode, as the position and direction of ultrasound beam are variable, the energy of ultrasound is
scattered in a comparatively large volume of tissues so that the perfusion ratio becomes high and the process of heat
becomes not so significant.
At this time, there is no solid evidence that the temperature elevation with currently available diagnostic ultrasound
instrument are harmful to the human body.
17-5
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MN1-5205 Rev.18
17-4.Derivation and Meaning of MI/TI
17-4. Derivation and Meaning of MI/TI
17-4-1. Introduction
In conventional systems, there has been no facility to display sound output data in a form that users can easily understand. Because no output was displayed in real time, it was difficult for the user to judge the level of acoustic
irradiation for the patient during examination. Formerly, as a means to control sound output at an approved safety
level, Food & Drug Administration (FDA) has established the irradiation limit volume according to the purpose of
use.
In 1992, AIUM (The American Institute of Ultrasound in Medicine) and NEMA (National Electrical Manufacturers
Association) published the Self standard indicating "real time representation of TI/MI criteria" (AIUM/NEMA:
Standard for real-time display of thermal and mechanical acoustic output indices on diagnostic instrument) to display an index susceptible to causing thermal effects and mechanical effects. This standard has established the method calculating and displaying indexes relatively susceptible to causing an acoustic process to a living body system.
With the index displayed by the screen of an ultrasound diagnostic device, it is possible for the user to deal with the
risks of irradiation in comparison with clinical advantage and one can decide an appropriate output level in each examination. In these days, in any kind of ultrasound wave diagnostic examination, the user can control the sound
output while confirming the index that is displayed in real time.
In the system like this device which has realized an "Output Display Standard," it can display to the user the indication relatively susceptible for causing mechanical effects or thermal effects to a living body system with displaying
an exponent.
These indexes are calculated based on a living body tissue irradiation model. When the value of each index becomes
1.0 or more, it shows that the risks producing biological effects are high. However, this index is not an absolute
measured value to show an indication susceptible to biological effects, but a relative measured value based on a current theory.
17-4-2. Mechanical index (MI)
The smallest sound pressure threshold that is necessary to crash minute air bubbles in liquid with the pressure of
cavitation was theoretically calculated, by Apfel and Hollandin in 1991, with the size of an air bubble and the
supersonic wave frequency as variables.
They showed that the sound pressure threshold is in proportion to the route of frequency where there are air bubbles
of the most suitable size.
The calculation type of MI was defined with this relation.
MI =
pr,α f awf
C MI
-1/2
-1/2
C MI
pr,α
=1 MPaMHz
: attenuated peak-rarefactional acoustic pressure (MPa)
f awf
: acoustic working frequency (MHz)
17-6
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17-4.Derivation and Meaning of MI/TI
Here, CMI is a standardization coefficient, and it is 1[MPaMHz-1/2].
Therefore, there is no unit in the MI. MI is led by a cavitation phenomenon of air bubbles in liquid.
There is, however, a recent report that the mechanism of damage of lung tissues by an ultrasound wave is caused by
mechanical tears of lung cell membrane at a place where an ultrasoundwave is incident on the lung tissues, in other
words, not caused by crashing of air bubbles by cavitation. In that case, the frequency dependence characteristics
become obscure than the cavitation phenomenon, and particularly in high frequency, the MI value is tend to be
underestimated.
Therefore, when echography is conducted in lung tissue periphery, caution is requested for keeping MI value as low
as possible. As attenuation in a living body works exponentially, before considering decrement in high frequency,
peak-rarefactional acoustic pressure pr becomes high even in the same MI value in high frequency.
When liquor amnii or bladder goes along the course where it seems that attenuation coefficient is less than
0.3dB/cm/MHz, attention is more necessary because the sound pressure that tissues receive has the possibility of
high even if the value of MI is low.
17-4-3. Thermal index (TI)
TI is defined that supersonic wave output Pα[mW] which is damped with a living body is divided by supersonic
wave output Pdeg[mW] that it is necessary for raising 1°C of the living body organization.
TI =
Pα
P deg
Pα : attenuated output power
TI has no unit as well as the MI. Pdeg varies by the living body organization and the mode of a diagnosis device.
Calculation of TI is based on a simplified assumption for giving information to the examiner during echography.
There are three kinds of TI are available, namely, TIS (soft tissue), TIB (bone) and TIC (skull), the calculation types
are different for solid beam and for scanning beam.
The chart below shows a classification and a diagram of TI.
When the ultrasound beam scans, rise in temperature by supersonic wave is supposed to be highest at the probe
osculating plane regardless of the target tissues.
• In the case of soft tissues of a non-scanning mode, the highest temperature elevation position is somewhere in
between the probe contact surface and the focal point of the wave.
• When soft tissues are closer in front and a bone is behind in the vicinity of the focus, temperature rises most on
the surface of the bone.
When doing diagnoses of an embryo that bones are on forming stage, non-scanning mode such as Doppler mode,
the use of TIB is recommended.
• When you are undecided which TI should be used, it is preferable to refer the following chart to decide where the
bones are located in the domain at which a supersonic wave is irradiated.
17-7
Page 16
MN1-5205 Rev.18
17-4.Derivation and Meaning of MI/TI
Scanning mode
Non-scanning mode
TIS
Thermal index
for soft tissue
Probe
Probe
Soft tissue
TIB
Thermal index
for bone
Soft tissue
Tissue surface
Before a focus
Soft tissue
Probe
Soft tissue
Bone surface
Bone
TIC
Thermal index
for skull
Probe
Probe
Bone
Soft tissue
Bone
Bone surface
Bone surface
Soft tissue
Classification and Diagram of Thermal Index
17-8
Page 17
MN1-5205 Rev.18
17-5.Setting condition influencing device output
17-5. Setting condition influencing device output
It is necessary to understand the setting condition of the ultrasonic diagnostic instrument influencing MI/TI to use
the indicated information of MI/TI more effectively.
MI is calculated by the greatest negative sound pressure like the definitional identity of MI.
TI is in proportion to the value that is averaged by time whereas MI is in proportion to instantaneous value.
The following table shows diagnosis device control settings to influence MI/TI.
Because there is a case not indicated on a screen as for the pulse repetition on frequency of a diagnosis device, it is
recommended to read carefully the instruction manual of a device in use.
ultrasonic diagnostic
instrument control settings
Switch in use or function
MI
Operation mode
Image display mode and Depth
Drive voltage
Acoustic Power switch
Drive frequency
Image freq.
Electronic focus
FOCUS
Drive wave form
POWER knob
Image display mode,
Image Select
Pulse repetition on frequency
Display range
Doppler velocity range
—
Scan width
Scan area, Flow area
—
Gain
Gain
—
Diagnosis instrument setting condition to influence MI/TI
17-9
TI
—
Page 18
MN1-5205 Rev.18
17-6.Recommendation on ALARA (As Low As Reasonably Achievable)
17-6. Recommendation on ALARA (As Low As Reasonably Achievable)
ALARA is an abbreviated name of As Low As Reasonably Achievable.
The concept is to draw diagnosis information to the maximum extent with the lowest supersonic wave sound power
level that can achieve its objective, and the principle is the same as practiced in the use of radioactive rays.
As the practical method, the mechanical index (MI) is to reduce exposure dose and the second practice is to shorten
inspection time.
As the mechanical effect and thermal effect are shown in real time, it is known the latency to a living body at the
same time. These are not accumulated in the body.
To collect images for diagnoses without taking exposure time more than required, the examination must be carried
out effectively. So that, the technique and the experience of operators are important.
1)
Choice of appropriate probe
2)
Choice of drive frequency (higher frequency is lower in MI value)
3)
Choice of electronic focus
4)
Lower Drive voltage
5)
Adjust Gain
Keep in mind these points during examination.
In addition, be more careful before using a contrast agent.
Thermal index (TI),
1)
Select appropriate TI
2)
Is the image adjustment appropriate (raise the gain or etc.) ?
3)
Is it possible to reduce TI value (reduce transmission voltage. lowering pulse repetition of frequency.
In the case of scan mode, widen the scan width) ?
4)
Is it possible to shorten exposure time ?
Keep in mind these points during examination.
17-10
Page 19
MN1-5205 Rev.18
17-7.Default Setting
17-7. Default Setting
In order to avoid unintentional high acoustic output, the sound output is limited by default setting in the following
cases (it becomes a low value):
1)
Power On
2)
Select the type of examination (Application) with the preset feature
3)
Switching the probe
4)
New Patient Function Operation (ID input)
Occasionally, Sound output is limited by Default setting (Low value).
Based on the type of examination, a sound output parameter including mechanical index (MI) and space peak time
average strength (I zpta,α) is set by a default level.
I zpta,α value is 720mW/cm2 or less for all types of examination.
There are cases that the mechanical index (MI) and the thermal index (TI) are more than 1 by the type of probe and
the mode of image display.
At that time, it displays the value in real time.
This instrument will not exceed the upper limits of TI<3, MI<1 in any fetal examination application.
The upper limits of TI<6, MI<1.9 will not be exceeded in any other examination type.
17-11
Page 20
MN1-5205 Rev.18
17-8.Protocol for calculating the measurement uncertainties
17-8. Protocol for calculating the measurement uncertainties
The protocol for calculating the measurement uncertainties follows the methods used in NEMA UD 2-2004.
The reporting of an acoustic output quantity requires the specification of the measurement mean and a quantitative
estimate of the uncertainty associated with the measurement.
Uncertainty is expressed in terms of confidence limits or tolerance limits.
A 95% confidence limit defines a range of values that will contain the true mean (or some other specified quantity)
95% of the time. A 95% tolerance limit defines a range of values that will contain a specified percentage of all
values 95% of the time.
An important feature of this approach is the incorporation of the Type A and Type B terminology in classifying the
components of measurement uncertainty, as recommended by the International Organization for Standardization
(ISO, 1993), and adopted by the American National Standards Institute (ANSI/NCSL, 1997).
These new terms replace the previous terms: "random uncertainty" and "systematic uncertainty".
Type A and Type B uncertainties are distinguished on the basis by which their numerical values are estimated.
Type A uncertainties are those that are evaluated by statistical treatment of repeated measurements, and Type B are
those that are evaluated by other means. An important reason for the new classification is to provide an internationally accepted procedure for mathematically combining individual components of uncertainty into a single total uncertainty regardless of whether arising from random or systematic effects.
Basic to this approach is representing each component of uncertainty by an estimated standard deviation, termed
standard uncertainty. Its symbol is ui and is equal to the positive square root of the estimated variance ui2 .
For a Type A uncertainty component, ui equals the statistically estimated standard deviation. Statistical methods
involve the analysis of multiple replications to estimate population parameters, such as the mean and the standard
deviation.
Type B evaluations are based on scientific judgment using all of the relevant information, which may include: (1)
previous measurement data, (2) experience with the relevant materials and instruments, (3) manufacturer's
specifications, (4) data provided national standards laboratories, and (5) uncertainty data taken from handbooks.
It should be noted that Type A evaluations of uncertainty based on limited data are not necessarily more reliable than
soundly based Type B evaluations (Taylor and Kuyatt, 1994).
Type A Evaluated Uncertainty
A Type A standard uncertainty, uA, of a measured quantity is equal to the standard deviation of the sample mean,
which is commonly called the standard error. It is given by,
uA =
Sx
(1)
n
where Sx is the sample standard deviation and n is the number of repetitions. As indicated in equation(1), a Type A
uncertainty is reduced by performing additional measurements. This results from the increase in the size of the denominator. Ideally, the measurements should be repeated a sufficient number of times to yield a reliable estimate
of the standard error.
17-12
Page 21
MN1-5205 Rev.18
17-8.Protocol for calculating the measurement uncertainties
Type B Evaluated Uncertainty
A Type B evaluation of uncertainty is performed after all adjustments for correctable systematic errors have been
made. The statistical distributions of all remaining systematic errors are combined to produce an overall statistical
distribution. Unless there is information to the contrary, the individual probability distributions are considered
independent rectangular distributions, each possessing a variance equal to ai2/3, where ai is the semi-range limit for
the ith uncertainty component. Because of the independence of the individual distributions, the total variance equals
the sum of the individual variances. Thus, for n rectangularly distributed uncertainty components, the total variance,
σ 2, is given by
σ2 = σ12 + σ22 + . . . . + σn2
(2)
and the Type B standard uncertainty, uB, is then
uB = σ =
2
a12 + a22 + a + ... + an2
3
(3)
Combined Uncertainty
The combined or total uncertainty of a measured quantity includes both Type A and Type B evaluated components
of uncertainty. It is computed after all blunders have been removed from the data base, and after all possible systematic corrections have been made. The combined uncertainty, uC, of a measured quantity is given by
u C = u A2 + u B2
(4)
The ISO (1993) advocates using the combined standard uncertainty as the parameter for expressing quantitatively
the uncertainty of the result of a measurement and in giving the results for all international comparisons of measurements. Although uC can be universally used to express the uncertainty of a measurement result, in many commercial,
industrial, and regulatory applications, and when health and safety are concerned, it is often desirable to provide a
measure of uncertainty that includes a larger proportion of the distribution of values that could be reasonable
attributed to the measurand. This is provided by multiplying the combined standard uncertainty by a coverage factor
k to yield the expanded uncertainty U. That is,
U = k ⋅ uC
(5)
The result of a measurement is then conveniently expressed as
x = x ±U
(6)
The value of the coverage factor k is chosen based on the level of confidence required for any given application. In
general, k will be in the range of 2 to 3. NIST has adopted a policy of setting k = 2, unless stated otherwise (Taylor
and Kuyatt, 1994). In ultrasonic exposimetry, k is usually set to the value of t.975, at the appropriate number of degrees of freedom, in order to provide a 95% level of confidence about the expected value of the measurand. Whatever the value of k chosen, it must be clearly stated in the final specification of the uncertainty.
17-13
Page 22
MN1-5205 Rev.18
17-8.Protocol for calculating the measurement uncertainties
<Results of measurement uncertainties>
Now we would like to offer the results of measurement uncertainties of our products.4 units of Aloka SSD-4000 and
6 units of UST-9123 for 4 times repeated acoustic output measurements (e.g. total power, PII, pr, fc). Though this
product model may be different from the model specified in this manual, we believe we can obtain the similar results
from different set of console and probes. The results were analysed using a two-way crossed analysis of variance
with repeated measurements.
In this analysis it is assumed that the consoles and transducers are independent and that all repeated measurements
are independent. It is also assumed that all preliminary steps, such as correcting for systematic errors, have been performed.There are six transducers (p = 6), four consoles (q = 4) and four times (r = 4) repeated measurements.
p :transducers
q :consoles
COMPUTATIONAL SETUP FOR
r:repetetions
console (j = 1, 2, …, q)
Transducer
i
(i=1,2,…. p)
1
2
…
q
1
m11, s11
m12, s12
…
m1q, s1q
m1・
2
m21, s21
m22, s22
m2q, s2q
m2・
・
・
・
・
・
・
・
・
・
・
・
・
・
・
・
p
mp1, sp1
mp2, sp2
…
mpq, spq
mp・
m.1
m.2
…
m.q
=
S. j
17-14
m
Si .
Page 23
MN1-5205 Rev.18
17-8.Protocol for calculating the measurement uncertainties
1 r
∑ x ijk
r k =1
ijth cell mean
m ij =
ith transducer mean
1 q
mi⋅ = ∑ mij
q j =1
jth console mean
overall mean
standard deviation of ijth cell
S ij =
standard deviation of transducer
2
ijk
− mij )
∑ (m
i =1
∑ (m
q
i =1
⋅j
)
2
p
S i⋅ =
S⋅ j =
standard deviation of console
k =1
(9)
1 p q
∑ ∑ mij
pq i =1 j =1
r
∑ (x
(8)
1 p
∑ mij
p i =1
m⋅ j =
m=
(7)
i⋅
−m
)
2
−m
(r − 1)
( p − 1)
(q − 1)
(10)
(11)
(12)
(13)
Using equation (8), (9) and (10), transducer mean, console mean and overall mean are calculated respectively. The
standard deviation calculated using equation (11) is expressed in percentage to overall mean value.
The variability inherent in the measurement technique is quantified by Smeas, the square root of the variance attributed solely to the measurement technique. That is,
S meas =
1 p q 2
∑∑ S ij
pq i =1 j =1
(14)
The transducer variability is quantified by Strans, which is given by
S trans = S i2⋅ −
1 2
S meas
rq
(15)
And the console variability is quantified by Scons, which is given by
S cons = S ⋅2j −
1 2
S meas
rp
17-15
(16)
Page 24
MN1-5205 Rev.18
17-8.Protocol for calculating the measurement uncertainties
The total variability is quantified by Stotal, which is given by
2
2
2
S total = S trans
+ S cons
+ S meas
(17)
The variance of the measurand is given by
2
σˆ x2 = Stotal
(18)
and the variance of the measurand mean is given by
σˆ x2 =
2
2
2
S trans
S cons
S meas
+
+
p
q
rpq
(19)
The Type A standard uncertainty is the square root of the variance of the measurand mean. That is,
u A = σˆ x2
(20)
The type B uncertainty is given by
uB = σ 2 =
a12 + a 22 + a 32 + ... + a n2
3
(21)
Then the combined uncertainty will be
u C = u A2 + u B2
(22)
The expanded uncertainty, U, for the purposes of ultrasonic exposimetry should be set for a level of confidence of
95%. Thus, k should be set equal to 2.07, the value of t.975 with pq-1 = 23 degrees of freedom (from Table 1 of UD
2-2004, Appendix A). Then,
U = k ⋅ u C = t.975 ( pq − 1) ⋅ u C
(23)
and the ultrasound power should be reported as
Power = m ± U
(24)
An upper 95% tolerance limit is computed using an expanded uncertainty in which the coverage factor is an appropriately chosen tolerance coefficient and the Type A component of the combined uncertainty equals σˆ x2 , instead
of
σˆ x2 . Thus, for an upper 95% tolerance limit for 99% of power values is given by,
u C = u A2 + u B2 = σˆ x2 + u B2
(25)
k should be set to the value of K.99 for pqr-1=95 degrees of freedom.
Then the expanded uncertainty is
U = k ⋅ u C = K .99 ( pq − 1) ⋅ u C
(26)
and the upper tolerance limit is expressed as
Power ≤ m + U
17-16
(27)
Page 25
MN1-5205 Rev.18
17-8.Protocol for calculating the measurement uncertainties
1) Uncertainty evaluation of total power
The standard deviation obtained from mean value of 6 transducers by eq. (12), Si. :
The standard deviation obtained from mean value of 4 consoles by eq. (13), S.j :
The standard deviation derived from measurement technique by eq.(14), Smeas:
The standard deviation due to the transducer variability by eq. (15), Strans:
The standard deviation due to the console variability by eq. (16), Scons:
The total standard deviation calculated by eq. (17), Stotal:
6.44
2.57
1.01
6.43
2.56
7.00
%
%
%
%
%
%
The type A uncertainty by eq. (20), uA:
2.92 %
Uncertainty components for type B uncertainty evaluation
The error due to reading the balance scale, a1 :
The error due to the reference source, a2 :
The error derived from alignment of the transducer, a3 :
The error derived from not coupling directly between the transducer and water, a4 :
The error derived from not enough thickness of the absorbing target, a5 :
±2 %
±4 %
-5%
-3%
-5%
The type B uncertainty by eq. (21), uB :
The combined uncertainty by eq. (22), uC :
5.13 %
5.91 %
The expanded uncertainty, U, for the purposes of ultrasonic exposimetry should be set for a level of confidence of
95%. Thus, k should be set equal to 2.07, the value of t.975 with pq-1 = 23 degrees of freedom (from Table 1 of UD
2-2004, Appendix A)
The expanded uncertainty by eq. (23), U
Totalpower= m ± 12.22%
12.22 %
(95% C.I.)
An upper 95% tolerance limit is computed using an expanded uncertainty in which the coverage factor is an appropriately chosen tolerance coefficient and the Type A component of the combined uncertainty equals
σˆ x2 and not
σˆ x2 as before.
The upper 95% tolerance limit for 99% of power values, uC :
8.68 %
The coverage factor, k should be set to the value of K.99 for pqr-1 = 95 degrees of freedom. Since a value for K.99
for 95 degrees of freedom is 2.69, then the coverage factor k = 2.69
The expanded uncertainty for the upper 95% tolerance limit, U
Total power ≤ m + 23.38%
17-17
23.38 %