SSD-α10 Instruction Manual Safety Instruction volume 2-2 rev 26 ver 8.0.2

ProSound logo is registered mark of Hitachi Aloka Medical, Ltd. in Japan and other countries. Copyright©Hitachi Aloka Medical, Ltd. All rights reserved. Microsoft and Windows Media player is registered trademark of Microsoft Corporations in United States and/or other countries. All brand name and product name are trademarks or registered trademarks of their respective companies. In this manual, ® and ™ are omitted. VS-FlexGrid Pro copyright©1999-2000 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.26

INTRODUCTION

Introduction This is an instruction manual for the model SSD-α10, an ultrasound diagnostic instrument. Read the manual carefully before using the instrument. Take special note of the items in Chapter 1, "Safety Precautions.". Keep this manual securely for future reference.

Symbols Used in this Document The following items are important in preventing harm or injury to equipment operator or patient. There are four levels of harm/damage that can be caused by ignoring instructions or displays and using the equipment incorrectly: "Danger," "Warning," "Caution," and "Note." These types are indicated by the following symbols. Indicates an imminently hazardous situation that will result in the death of or serious injury to the equipment operator. Indicates a hazardous situation that could result in death or serious injury. Indicates a hazardous situation that may result in slight or moderate injury, or property damage. Indicates a request concerning an item that must be observed in order to prevent damage or deterioration to the equipment and also to ensure effective use.

Cautions use the following graphics

This mark indicates and alert, additional information.

This mark indicates that the action is not allowed.

This mark indicates that the action is required.

Conventions used in this manual. NOTE: Notes containing additional information. IMPORTANT: Information that is considered especially important.

改 訂

Input, output and screen-messages are presented in the following font: message. Menus and switches are written as Menu. Submenus are indicated by the use of angle brackets: Menu > sub-menu > sub-menu.

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3

INTRODUCTION

About the model “SSD-α10” The SSD-α10 is intended to be used by doctors and other qualified personnel in fracture diagnostics and hemodynamic diagnostics. However, this equipment is not designed to be used in ophthalmic ultrasound diagnosis, as its sound intensity is not compliant with ophthalmic restrictions established by the FDA. Only physicians and other qualified personnel should operate this equipment for diagnostic purposes. Read section 1-1 of the Safety Instruction. 1)

PRECAUTIONS Concerning the Use/Management of the SSD-α10 •

Do not disassemble, repair or remodel this equipment or optional features without our consent. NOTE: Disassemble is removing the parts or options from the equipment using

tools. NOTE: Remodel is installing or connecting the unspecified parts or equipment,

including replacement of power cord. •

Assemble of the equipment or optional accessories shall be performed by a third party certified by us. Please contact one of our offices listed on back cover. NOTE: Assemble is installing and connecting the parts or optional accessories on

the main equipment using tools.

2)

•

Transporting this equipment (via automobile/ship) shall be performed by a third party certified by the manufacturer. Please contact one of our offices listed on back cover.

•

Please conduct routine cleaning and inspection of the equipment. Refer to Chapter 5 of the Safety Instruction for details. .

•

Ensure that the output level of the scan conforms to the required duration of diagnosis.

•

If any malfunction or abnormality is discovered during operation of the equipment, remove the probe from the patient immediately and discontinue use. If any abnormality is observed in the patient, provide proper care as quickly as possible. Refer to Chapter 4 of the Safety Instructions for more information on dealing with the equipment appropriately. If the malfunction is not listed in Chapter 4 of the Safety Instructions, contact one of our offices listed on back cover.

PRECAUTIONS for the SSD-α10 Installation This equipment is a medical electrical device that is intended for use in hospitals, and research facilities. The equipment should be installed in accordance with the following guidelines.

改 訂

•

Install in accordance with Chapter 3 of the Safety Instructions. .

•

Install in an environment that conforms to the operating environments indicated in section 2-2-2 of the Safety Instructions.

•

Install in an environment that ensures electromagnetic compatibility, in accordance with section 1-2-6 of the Safety Instructions, "Precautions Concerning the Maintenance of Electromagnetic Compatibility," and Item 1-3, "Guidelines for Electromagnetic compatibility." NOTE: The electromagnetic compatibility (EMC) is the ability of device to function

satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbance to anything in that environment.

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INTRODUCTION

Classification of model “SSD-α10” • Protection against electric shock (ME equipment): class I • ME equipment • Protection Against Electric Shock (Applied Parts): Type BF Applied Parts –

Probe/scanner applied parts and parts treated as applied parts: Refer to the following diagram (Probe/Scanner Pattern Diagram) and table.

Figure: Probe/Scanner Pattern Diagram Above illustrates a surface/intraoperative probe. Below shows a coelomic probe. B

C

A

connector

D

connector

C

A

Applicable part of body

Applied part

parts treated as applied parts

B - C length

surface of body

Ultrasonic irradiation area (D)

A to B

100 cm

Intraoperative

Ultrasonic irradiation area (D)

A to B

20 cm

Endocavity

A to C

A to C

N/A

–

Physiological signal applied part: ECG electrodes Part treated as applied part: 2m from the ECG electrode of the ECG patient cable (consult following diagram) 2 meters ECG electrodes

connector ECG patient lead

• Protection against electric shock (Defibrillation-proof applied parts): Not suitable • Protection against harmful ingress of water or particulate matter –

equipment: IPX0 (Ordinary equipment)

–

Probe applied part: IPX7 (Watertight equipment)

• Suitability for use in an oxygen rich environment: Not suitable • Method(s) of sterilization: Not suitable for sterilization/disinfection with medicinal solution, gas or radiation. • Mode of operation: Continuous operation

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5

CONTENTS 1 Safety Precautions 1-1

Purpose of Use ... 1-1

1-2

Precautions for Use ... 1-2 1-2-1 1-2-2 1-2-3 1-2-4 1-2-5 1-2-6

1-3

Electromagnetic compatibility ... 1-17 1-3-1 1-3-2 1-3-3 1-3-4 1-3-5

1-4

Warnings and Safety Notice ... 1-3 Labels on the equipment ... 1-6 Precautions concerning acoustic power ... 1-13 Precautions for Use in Conjunction with Drugs ... 1-14 Precautions for Use in Conjunction with Other Medical Devices... 1-15 Guideline for Electromagnetic Compatibility... 1-16 Guidance and manufacturer’s declaration –electromagnetic emissions ... 1-17 Essential performance... 1-18 Guidance and manufacturer’s declaration – electromagnetic immunity ... 1-19 Guidance and manufacturer’s declaration – electromagnetic immunity ... 1-20 Recommended separation distances between portable and mobile RF communications equipment and the SSD-α10 ...1-21

Electrostatic Discharge (ESD) Guidelines ... 1-22

2 Specification and Component Names 2-1

Principle of Operation ... 2-1

2-2

Specifications ... 2-3 2-2-1 2-2-2 2-2-3

2-3

Power Requirements ... 2-7 Environmental Conditions ... 2-7 Classification of model “SSD-α10” ... 2-8

Name of Each Parts ... 2-9 2-3-1 2-3-2

Name of Each Parts ... 2-9 Operation panel ... 2-15

3 Preparation for Use

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3-1

Installing the equipment ... 3-1

3-2

Connecting the Peripheral Instrument ... 3-3 3-2-1 3-2-2 3-2-3

3-3

Connecting a Probe to the Instrument... 3-4 Connect the Physiological Signal Connector ... 3-6 Connecting with Other Instrument ... 3-9

Moving the equipment ... 3-11 3-3-1 3-3-2

Isolate from the supply main ... 3-11 Move the equipment ... 3-11

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3-4

Storing the Instrument ... 3-15

3-5

Inspection Before Using ... 3-16 3-5-1 3-5-2

3-6

Screen Display ... 3-18 3-6-1 3-6-2 3-6-3

3-7

Character Display ... 3-18 Graphic Display ... 3-20 Color display... 3-21

Adjusting the Operation Panel ... 3-22 3-7-1 3-7-2

3-8

External Inspection ... 3-16 Operation Check ... 3-17

Adjust the Height of the Operation Panel ... 3-22 Adjust the position of the operation panel ... 3-23

Adjusting the Monitor ... 3-24 3-8-1 3-8-2

Adjust the Angle and Position of the Monitor ... 3-24 Adjust the Brightness of the Monitor ... 3-27

4 Troubleshooting 4-1

Messages ... 4-1 4-1-1 4-1-2

4-2

Message List ... 4-2 Assistant Messages ... 4-11

Other troubles ... 4-13 4-2-1

Image Display and Image Degradation ... 4-13

5 Maintenance 5-1

After Using the Instrument ... 5-1 5-1-1

5-2

Cleaning ... 5-3 5-2-1 5-2-2 5-2-3

5-3

State of the Instrument and Accessories... 5-2 Clean the Instrument ... 5-4 Cleaning the trackball ... 5-5 Cleaning the air filter ... 5-6

Maintenance ... 5-7 5-3-1 5-3-2 5-3-3

Daily check: For Using the Instrument for a Long Period ... 5-8 Checking the Measurement Accuracy... 5-9 Safety Inspection... 5-16

6 Accessories and options 6-1

Standard composition ... 6-1

6-2

Options ... 6-2

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7 Probes 7-1

Caution in the Handling of Probes ... 7-1 7-1-1 7-1-2

7-2

Probe specifications ... 7-7 7-2-1 7-2-2 7-2-3 7-2-4 7-2-5 7-2-6 7-2-7 7-2-8 7-2-9 7-2-10

7-3

Caution about Handling of Probes ... 7-1 Cautions about Cleaning and Storage ... 7-5 Convex Sector Probes ... 7-9 Phased Array Sector Probe... 7-12 Linear Probes ... 7-15 Combination Probes... 7-17 3D Probes ... 7-18 Mechanical Radial Probe ... 7-19 Mechanical Annular Array Sector Probe ... 7-20 Independent probe ... 7-20 Ultrasonic Gastrovideo Scope ... 7-21 Ultrasonic Bronchofiber Videoscope ... 7-22

Clinical Measurement Range ... 7-23

8 Acoustic Output Safety Information 8-1

Acoustic output index ... 8-1

8-2

Interaction between ultrasound and tissues ... 8-3 8-2-1

8-3

Possible Biological Effects ... 8-4

Derivation and Meaning of MI / TI ... 8-6 8-3-1 8-3-2

Mechanical Index (MI) ... 8-6 Thermal Index (TI)... 8-7

8-4

Setting condition influencing device output ... 8-9

8-5

Recommendation on ALARA principle ... 8-11

8-6

Default Setting ... 8-12

8-7

Acoustic output limits ... 8-12

8-8

Measurement uncertainties ... 8-13 8-8-1 8-8-2

8-9

Protocol for calculating the measurement uncertainties... 8-13 Results of measurement uncertainties ... 8-15

References ... 8-22

9 Acoustic Output Tables

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9-1

Acoustic power measurement value ... 9-1

9-2

Display accuracy of MI/TI ... 9-2

9-3

Acoustic Output Tables ... 9-2 9-3-1 9-3-2 9-3-3

Convex Sector Probe ... 9-4 Phased Array Sector Probe... 9-82 Linear Probe ... 9-160

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9-3-4 9-3-5 9-3-6 9-3-7 9-3-8 9-3-9 9-3-10

Combination Probe... 9-232 3D Probe ... 9-244 Mechanical Radial Probe ... 9-262 Mechanical Annular Array Probe... 9-265 Independent Probe... 9-267 Ultrasonic Gastrovideo Scope ... 9-269 Ultrasonic Bronchofiber videoscope ... 9-317

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8 Acoustic Output Safety Information 8-1 Acoustic output index

8

Acoustic Output Safety Information

8-1

Acoustic output index With this device, output indices about the potential for ultrasound induced biological effect to the tissue are displayed. The displayed indices are the four forms. Of these, mechanical index, MI shows the mechanical bioeffect in tissue, and thermal indices, TIs show the thermal bioeffect in tissue provided three forms according to tissue models. • Mechanical index: MI Mechanical index (MI) provides an on-screen indication of the relative potential for ultrasound to induce an adverse bioeffect by a non-thermal mechanism such as cavitation. The mechanical bioeffect is caused by the motion of tissue induced when ultrasound pressure waves pass through or near a gaseous body. The majority of the mechanical interactions relate to the generation, growth, vibration and possible collapse of microbubbles within the tissue. This behavior is referred to as cavitation. Because the thermal bioeffect 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 thermal bioeffect is also important. • Thermal index: TI –

Soft tissue Thermal Index : TIS The soft tissue thermal index provides information on temperature increase within soft homogeneous tissue (heart, first trimester fetal and abdominal scans). TIS can be displayed on all modes.

–

Bone Thermal index: TIB The bone thermal index (TIB) provides information on temperature increase of bone at or near the focus when the beam passes through soft tissue (second and third trimester fetal and neonatal cephalic through the fontanels scans).

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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.

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8-1

8 Acoustic Output Safety Information 8-1 Acoustic output index –

Cranial Bone Thermal index : TIC The cranial bone thermal index (TIC) provides information on temperature increase of bone at or near the surface, such as may occur during pediatric and adult cranial scan, in which the ultrasound beam passes through bone near the beam entrance into the body. TIC can be displayed on all modes.

The demarcation between safe levels and levels that the potential for biological effects exist is important for the operators. The WFUMB (World Federation for Ultrasound in Medicine and Biology) gives some guidelines. For example, "Embryonic and fetal in situ temperature above 41 ℃ (4 ℃ above normal temperature) for 5 min or more should be considered potentially hazardous.", etc. On the other hand, the indices provide us an indication of the conditions which are more likely than others to produce thermal and/or mechanical bioeffect in comparison with other physical quantities such as the peak rarefactional acoustic pressure or its intensity. For example, TI values above a certain upper level of the range (more than 1.0) might be better to avoid in obstetric applications. Such a restriction allows a reasonable safety margin considering the WFUMB recommendation that a temperature increase of 4 ℃ for 5 min or more should be considered as potentially hazardous to embryonic and fetal tissue. However if particular clinical results cannot be obtained with lower values, increased output may be warranted, but particular attention to limit the exposure time should be made. Any extra thermal load to the fetus when the mother has a fever is also unwise, and again note should be made to avoid high TI values. The following list shows an indication of importance of maintaining low values of MI/TI in clinical use by IEC 60601-2-37. Table 1: Relative importance of maintaining low exposure indices in various scanning situations Of greater importance MI

• With contrast agents • Cardiac scanning (lung exposure)

Of less importance • In the absence of gas bodies: i.e. in most tissue imaging

• Abdominal scanning (bowel gas) TI

• First trimester scanning • Fetal skull and spine

• In well-perfused tissue: For example, Liver and spleen

• Patient with fever

• In Cardiac scanning

• In any poorly perfused tissue

• In vascular scanning

• If ribs or bones are exposed: TIB CAUTION: It has been thought that cavitation is hard to occur with the diagnostic ultrasound

because it contains as high as several MHz to several dozen MHz frequencies. However, according to the animal experiments, 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

改 訂

acoustic pressure. Also according to the animal experiments, ultrasonically induced lung damage in the fluid-filled

出図

lungs of fetuses is not to be expected.

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8 Acoustic Output Safety Information 8-2 Interaction between ultrasound and tissues

From these facts, it is requested to be careful for using contrast agent to inject air bubbles intentionally.

8-2

Interaction between ultrasound and tissues When ultrasound propagates through human tissue, there is a potential for tissue damage. During an exam, though 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 tissue, much of the ultrasound energy is absorbed by body tissue. Ultrasound generated by the transducer is a physical pressure wave with typical frequencies range from 2 MHz (megahertz, or millions of cycles per second) to 10 MHz. In ultrasound irradiation, the energy absorbed in the tissue may cause some biological effects. These mechanisms are classified as mechanical action and thermal action, respectively. Mechanical bioeffects 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 met, 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 closely relate to the peak-rarefactional (peak-negative) acoustic pressure 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 bioeffect, the thermal bioeffect, is due to the tissues absorbing the energy of the ultrasound beam. When an acoustic wave transmits through the body tissue, the energy of a sound wave is attenuated. There are two main causes for attenuation: Absorption and scattering. Absorption is the conversion of ultrasonic energy into heat; whereas, scattering is the redirection of the ultrasound away from the direction it was originally traveling. Absorption of acoustic energy by tissue results in the generation of heat in the tissue. This is what is referred to as the thermal mechanism. Unlike mechanical bioeffect, thermal bioeffect is thought to be temporal in nature, and relate to a tissue volume, perfusion rate, exposure time, and duty factor (ratio of the duration of transmitting pulse to the pulse repetition period). Among the physiological effects known to occur due to tissue heating are abnormalities in cell physiology or the low rate of DNA synthesis and increased possibility for the retardation of growth of systems such as the heart, brain and skeleton of the fetus.

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8-3

8 Acoustic Output Safety Information 8-2 Interaction between ultrasound and tissues

8-2-1

Possible Biological Effects Mechanical bioeffect Mechanical bioeffect is occurred by the oscillation of a pressure wave when 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. Though mechanical bioeffect contain cavitation (ultrasonically activated behavior of micro bubbles and other "nucleation sites" in tissue), acoustic radiation force and microstreaming, etc, cavitation is thought to be most important. There are two categories of cavitation: Non-inertial (once termed Steady-state) cavitation and Inertial (once termed Transient) cavitation. Non-inertial cavitation arises 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. During inertial cavitation, pre-existing bubbles or cavitation nuclei expand from the pressure of the ultrasonic field and then collapse in a violent implosion. 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 bioeffects 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 bioeffect. Higher frequencies decrease the potential for mechanical bioeffect. At this time, there is no solid evidence that cavitation occurs in human tissue with the output intensities available on current ultrasound diagnostic systems. However, mechanical effects are theoretically possible.

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8 Acoustic Output Safety Information 8-2 Interaction between ultrasound and tissues

Thermal bioeffect Thermal bioeffect occurs 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, especially 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 residual energy must be absorbed by the tissues. With this absorption, heat is developed mainly in two areas such as at the surface of the body where ultrasound beam enters and in the vicinity of the focus of the beam. Because of difference in their physical properties, different tissues absorb ultrasound energy at different rates. Absorption coefficient 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 rate than those of 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 absorb 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 bioeffects in tissue. The three models are • Soft tissues • Bone at focus and • Bone at the surface. The type of ultrasound beam also influences the potential for thermal bioeffect. In non-scanning mode (example: D-mode), 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 bioeffects 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 rate 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 ultrasound diagnostic systems is harmful to the human body.

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8-5

8 Acoustic Output Safety Information 8-3 Derivation and Meaning of MI / TI

8-3

Derivation and Meaning of MI / TI In 1992, AIUM (The American Institute of Ultrasound in Medicine) and NEMA (National Electrical Manufacturers Association) published the voluntary standard "TI/MI output display standard" (AIUM/NEMA: Standard for real-time display of thermal and mechanical acoustic output indices on diagnostic ultrasound equipment). This standard has established the method calculating and displaying indices relatively indicating the possibility of mechanical and thermal bioeffect. IEC 60601-2-37 "Particular requirements for the basic safety and essential performance of ultrasonic medical diagnostic and monitoring equipment" employs the same indices. Therefore the user can control the acoustic output while confirming the indices are real-time displayed on the majority of modern diagnostic ultrasound equipment. These indices, the thermal index (TI) and the mechanical index (MI), provide unitless numbers giving information on the likelihood of an adverse biological effect resulting from the current ultrasound examination. The indices were designed so that if either index exceeded a predefined value, there was a potential for harm. When the value of index exceeds 1.0, the user should assess if the examination could be performed with a lower acoustic output, or consider mitigating factors in reevaluating the risk-benefit analysis. Mitigating factors include the absence of gas-containing structures, anatomical sites that would be particularly invulnerable to damage and the perfusion rate in the region being examined. Also, the duration of the examination should be kept to a minimum to avoid any unnecessary exposure. However there is another risk that must be considered: the risk of not doing the ultrasound exam and either not having the enough information necessary to diagnose. It is also important to recognize that the potential harm from misdiagnosis can have greater consequences than that of ultrasound-induced bioeffect.

8-3-1

Mechanical Index (MI) Scientific evidence suggests that mechanical or nonthermal bioeffect, like cavitation, are a threshold phenomenon, occurring only when a certain level of output is exceeded. However the threshold level varies depending on the tissue. The potential for mechanical effects is thought to increase as peak-rarefactional acoustic pressure increases, but to decrease as the ultrasound frequency increases. Therefore the mechanical index MI is defined as: CMI = 1 MPa MHz-1/2

改 訂 出図

MI =

pr, α fawf-1/2 CMI

pr : attenuated peak-rarefactional acoustic pressure (MPa) fawf: acoustic working frequency (MHz)

CMI is a standardization coefficient, and it is 1 [MPa MHz-1/2]. Therefore, MI is unitless.

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8 Acoustic Output Safety Information 8-3 Derivation and Meaning of MI / TI

The MI becomes important at a gas/soft tissue interface, for example in cardiac scanning where the lung surface may be exposed. Most critically, however, is with the use of contrast materials containing gas bubbles when most attention should be paid to limit MI. As the ultrasound goes through the fluid such as amniotic fluid or bladder with very little decrease, the sound pressure received by the tissues might be high even if the value of MI is low.

8-3-2

Thermal Index (TI) TI is defined that the ratio of attenuated acoustic power at a specified point, Pα [mW] to the attenuated acoustic power required to raise the temperature at that point in a specific tissue model by 1 ℃ , Pdeg [mW].

TI =

Pα Pdeg

Pα: attenuated output power

TI is unitless as well as MI. There are three thermal indices are used for different combinations of soft tissue and bone in the area to be examined, namely, TIS (soft tissue), TIB (bone) and TIC (cranial bone). The purpose of the thermal indices is to keep users aware of conditions that may lead to a temperature rise whether at the surface, within the tissues, or at the point where the ultrasound is focusing on bone. Each thermal index estimates temperature rise under certain assumptions. • For scanning mode, the position of the maximum heating is assumed to be at the surface of the probe for all tissue models. • For non-scanning mode, if bone is not present, the maximum heating is likely to occur between the surface of the probe and the focus of the ultrasonic beam. • For non-scanning mode, if bone is present and located near the focus of the ultrasonic beam, the maximum heating is likely to occur at the surface of the bone. When doing diagnoses of the fetus that are developing neural tissues, such as the brain and spinal cord, that may be in a region of heated bone, it is recommended to display TIB and pay attention to its value. When you are undecided which TI should be displayed, it is preferable to refer the following chart to decide where the bones are located in the region at which is irradiated by ultrasound.

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8 Acoustic Output Safety Information 8-3 Derivation and Meaning of MI / TI Table 2: Thermal Index categories and models Scanning mode

Non-scanning mode

TIS: Soft tissue thermal index

Probe

Probe

Tissue surface Tissue surface Soft tissue

Soft tissue

Before a focus

TIB: Bone thermal index Probe Soft tissue

Bone surface Bone

TIC: Cranial-bone thermal index Probe

Probe

Bone

Bone

Bone surface

Bone surface Soft tissue

Soft tissue

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8 Acoustic Output Safety Information 8-4 Setting condition influencing device output

8-4

Setting condition influencing device output It is necessary to understand the setting condition of the ultrasonic diagnostic equipment influencing MI/TI to use the indicated information of MI/TI more effectively. MI is calculated using the peak rarefactional (negative) acoustic pressure. TI is proportional to the time averaged value whereas MI is proportional to instantaneous value. The following table shows diagnosis device control settings to influence MI/TI. Some parameters such as the pulse repetition frequency are not displayed on a screen of the device. Therefore it is recommended to read carefully the instruction manual (User’s Guide) in use. Table 3: Ultrasound Diagnostic System setting condition to influence MI/TI *1 Settings condition to influence MI/TI in continuous wave doppler (CWD) are only drive voltage and electric focus. *2 Gain do not influence MI/TI for processing gain after receiving.

System Control Settings*1 COMMON Drive Voltage

B

M

PW

Switch or function

MI

TI

―

Acoustic Power

Electric focus

Focus

*2

Gain

Gain

―

Pulse repetition frequency

Depth/Range

―

PRF limit

―

Drive frequency

Image/Freq

Number of scanning lines

Framerate

―

Beam Process

―

ScanArea

―

Imaging mode (wave)

ExPHD, PHD

Pulse repetition frequency

Depth/Range

Drive frequency

Image/Freq

Imaging mode (wave)

ExPHD, PHD

Pulse repetition frequency

Velocity Range

―

High PRF

―

Drive frequency

Image/Freq

Pulse duration

IP Select

Imaging mode (wave)

TDI

―

―

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8 Acoustic Output Safety Information 8-4 Setting condition influencing device output

System Control Settings*1 Mflow

Flow

Pulse repetition frequency

Switch or function

MI

Velocity Range

―

High PRF

―

Drive frequency

Image/Freq

Pulse duration

IP Select

Imaging mode (wave)

TDI

Pulse repetition frequency

Depth/Range

―

Velocity Range

―

TI

―

Drive frequency

Image/Freq

Number of scanning lines

Framerate

―

Beam Process

―

FlowArea

―

Average(Flow)

―

Pulse duration

IP Select

―

Imaging mode (wave)

eFlow, Power, TDI

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8 Acoustic Output Safety Information 8-5 Recommendation on ALARA principle

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Recommendation on ALARA principle ALARA stands for "As Low As Reasonably Achievable". Following the ALARA principle means that total acoustic output is kept as low as reasonably achievable, while diagnostic information being optimized. This guiding philosophy is the same as in the use of X-ray equipment. For example, when the mechanical index (MI) is considered, • Selection of appropriate probe • Selection of drive frequency (higher frequency is lower in MI value) • Selection of electronic focus • Lower Drive voltage • Adjust Gain (Higher Gain) Keep in mind these points during examination. In addition, be more careful before using a contrast agent. When Thermal Index(TI) is considered, • Selection of appropriate TI • Appropriate image adjustment (raise the gain, etc.) • Reduction of TI value (reduce transmission voltage, lowering pulse repetition frequency, widen the scan width in the case of scan mode) • Shorten exposure time Keep in mind these points during examination.

改 訂 出図 2012.3.14 MS 技 MN1-5205 rev.26 アロカ

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