MicroMaxx Service Manual Aug 2005

SonoSite, Inc. 21919 30th Drive SE Bothell, WA 98021-3904 USA Telephone: 1-888-482-9449 or 1-425-951-1200 Fax: 1-425-951-1201 SonoSite Ltd Alexander House 40A Wilbury Way Hitchin, Herts SG4 OAP UK T: +44-1462-444800 F: +44-1462-444801 Caution:

Federal (United States) law restricts this device to sale by or on the order of a physician.

“MicroMaxx,” “TITAN,” and “SonoSite TITAN” are trademarks of SonoSite, Inc. Non-SonoSite product names may be trademarks or registered trademarks of their respective owners. SonoSite products may be covered by one or more of the following U.S. patents: 4454884, 4462408, 4469106, 4474184, 4475376, 4515017, 4534357, 4542653, 4543960, 4552607, 4561807, 4566035, 4567895, 4581636, 4591355, 4603702, 4607642, 4644795, 4670339, 4773140, 4817618, 4883059, 4887306, 5016641, 5050610, 5095910, 5099847, 5123415, 5158088, 5197477, 5207225, 5215094, 5226420, 5226422, 5233994, 5255682, 5275167, 5287753, 5305756, 5353354, 5365929, 5381795, 5386830, 5390674, 5402793, 5,423,220, 5438994, 5450851, 5456257, 5471989, 5471990, 5474073, 5476097, 5479930, 5482045, 5482047, 5485842, 5492134, 5517994, 5529070, 5546946, 5555887, 5603323, 5606972, 5617863, 5634465, 5634466, 5636631, 5645066, 5648942, 5669385, 5706819, 5715823, 5718229, 5720291, 5722412, 5752517, 5762067, 5782769, 5800356, 5817024, 5833613, 5846200, 5860924, 5893363, 5916168, 5951478, 6036643, 6102863, 6104126, 6113547, 6117085, 6142946, 6203498 B1, 6371918, 6135961, 6364839, 6383139, 6416475, 6447451, 6471651, 6569101, 6575908, 6604630, 6648826, 6835177, D0280762, D0285484, D0286325, D0300241, D0306343, D0328095, D0369307, D0379231, D456509, D461895, 10/682699, 10/407682. Other patents pending.

P05324-01 08/2005 Copyright 2005 by SonoSite, Inc. All rights reserved.

ii

Contents Chapter 1: Introduction Audience ... 1 Conventions Used in This Service Manual ... 1 Product Upgrades and Updates ... 1 Customer Comments ... 1 About the System ... 2 About the System Software ... 3 Software Licensing ... 3

Chapter 2: Safety Electrical Safety ... 5 Equipment Safety ... 6 Battery Safety ... 7 Biological Safety ... 8 Labeling Symbols ... 8

Chapter 3: System Overview System Overview ... 9 Theory of Operation ...10 Description of Operating Modes ...11 Velocity Color Doppler (VCD) ...14 Additional System Feature Performances ...15 ECG Module ...16 DICOM ...17 IMT ...17 System Specifications ...17 System Dimensions ...17 Display Dimensions ...17 Transducers ...17 Imaging Modes ...18 Image Storage ...18 Accessories ...18 Peripherals ...19 Temperature, Pressure, and Humidity Limits ...19 Electrical ...19 Battery ...19 Electromechanical Safety Standards ...20 EMC Standards Classification ...20 Airborne Equipment Standards ...20 DICOM Standard ...20 HIPAA Standard ...20

Chapter 4: Setup and Operation System Controls ...21 System Components ...23 Setup ...23 Setup Security Settings ...24 Audio and Battery ...28 Connectivity ...29 Date and Time ...30 Delta Key and F Keys ...31 Display Information ...31 IMT Calculations ...32

iii

OB Calculations Authors ...33 OB Custom Measurements ...34 OB Custom Tables ...35 Presets ...36 System Information ...37 Touchpad ...38 Accessories ...38 Preparing the System for Operation ...38 Installing and Removing the Battery ...38 Installing and Removing the CompactFlash Card ...39 Using AC Power/Charging Battery ...40 Connecting and Removing the Transducer ...41 Turning System On/Off ...41 Upgrading the System and Transducer Software ...42 Upgrading Triple Transducer Connect (TTC) ...46 Obtaining a License Key ...46 Installing a License Key ...47 To Display the System Information Screen ...48 To Display the License Update Screen ...48

Chapter 5: Cleaning and Disinfecting Universal Precautions ...49 Receipt of Suspected Contaminated Materials ...49 Recommended Disinfectants ...49

Chapter 6: Troubleshooting Basic Troubleshooting ...51 Periodic Maintenance ...52 System and Subsystem Diagnosis ...52 System Repair ...52 Test Equipment ...53 Failure (Assert) Codes ...53 Verifying a System Assert Code ...53 Troubleshooting Flow Diagrams ...54 Display ...54 Control Panel ...55 System ...56 Battery ...57 DICOM ...58

Chapter 7: Replacement Procedures Display Replacement ...59 Required Parts ...59 Required Tools ...59 Display Removal ...59 Display Replacement ...61 Test the Display ...62 Control Panel Subassembly Replacement ...62 Required Parts ...62 Required Tools ...62 Control Panel Removal ...62 Control Panel Replacement ...62 Main System Disassembly for Repair and/or Replacement ...63 Required Parts ...63 Required Tools ...63 Main PCBA Removal ...63

iv

Chapter 8: Performance Testing Overview ...69 Test Equipment ...69 Setting Up Performance Tests ...69 Scan Reference Orientation ...69 Testing 2D Performance ...70 2D Image Quality ...70 Axial Measurement Accuracy ...70 Lateral Measurement Accuracy ...71 Penetration ...71 Additional Performance Tests ...72 CPD ...72 M Mode Imaging ...72 Tissue Harmonic Imaging ...72 Pulsed Wave (PW) Doppler Imaging ...73 Image Quality Verification Test/Livescan ...73 Image Review ...73 Printer ...73 Battery Charging ...73 Video Output ...74 Returning Products to SonoSite ...74 Contacting SonoSite Technical Support ...74 Shipping Instructions ...74

Appendix A: Parts List Replacement Parts List ...75 Display ...75 Control Panel ...77 Replacement Parts, System ...78 Transducer Nest Frame Assembly ...84 Ordering Replacement Parts ...84 Appendix B: Service Event Report Index ... 89

v

Chapter 1: Introduction Before servicing the MicroMaxx ultrasound system, please read the information in this manual. This text applies only to the SonoSite MicroMaxx ultrasound system product manufactured after June 1, 2005. Please find service information about products manufactured before June 1, 2005 in C1.51 Ultrasound System Service Manual (P00715), C1.75 Ultrasound System Service Manual (P01118), C1.9 PLUS Ultrasound System Service Manual (P02287), C1.99 PLUS and ELITE Ultrasound System Service Manual (P02913), and TITAN Ultrasound System Service Manual (P03309).

Audience The intended audience of this manual is properly trained field and in-house service personnel.

Conventions Used in This Service Manual These conventions are used in this service manual: • A WARNING describes precautions necessary to prevent injury or loss of life. • A Caution describes precautions necessary to protect the products. • When the steps in the operating instructions must be performed in a specific order, the steps are numbered. • Bulleted lists present information in list format, but they do not imply a sequence. • The system handle is on the front of the system, and the battery compartment is on the back of the system.

Product Upgrades and Updates SonoSite may offer software upgrades and new features that may improve system performance. Service manual updates, explaining the effects of upgrades and new features on system performance, will accompany the upgrades.

Customer Comments Questions and comments are encouraged. SonoSite is interested in your feedback regarding the service manual. Please call SonoSite at 1-877-657-8118. If you are outside the USA, call the nearest SonoSite representative. You can also send electronic mail (e-mail) to SonoSite at the following address: [email protected]

Chapter 1: Introduction

1

About the System The ultrasound system has multiple configurations and feature sets. All are described in this service manual but not every option may apply to your system. System features are dependent on your system configuration, transducer, and exam type.

3

4 1

2

Figure 1.1 MicroMaxx System Front View Table 1.1: MicroMaxx System Front Features Number

Feature

1

Control panel

2

Handle

3

Display

4

CompactFlash® slots (front for image storage, back for system and transducers updates, import/export OB tables, user names/passwords, and DICOM configurations)

1

2 3

Figure 1.2 MicroMaxx System Rear View Table 1.2: MicroMaxx System Rear Connectors Number

2

Feature

1

DC input connector

2

I/O connector

3

Battery

4

ECG connector

Chapter 1: Introduction

4

The system is a portable, software-controlled, ultrasound system using all-digital architecture. The system is used to acquire and display high-resolution, real-time ultrasound images: 2D, color power Doppler (CPD), Color Doppler (Color), Tissue Harmonic Imaging (THI), M Mode, pulsed wave (PW) Doppler, and continuous wave (CW) Doppler. The system has a cine buffer, pan zoom, labeling, biopsy, measurements, calculations, a connection for image transfer, image and clip storage, image review, printing, recording, the ability to archive Doppler with audio output to a videotape, and DICOM connectivity. Currently, the system supports the following broadband transducers: • C60e/5-2 MHz 60 mm curved array • HFL38/13-6 MHz 25 mm linear array • ICT/8-5 MHz 11 mm intracavitary array • L38e/10-5 MHz 38 mm linear array • P17/5-1 MHz 17 mm phased array • TEE/8-3 MHz phased array System accessories include the following: mobile docking system (MDS), MDS Lite, mini-dock, Triple Transducer Connect, a power supply, a battery, ECG cable, video and printer cables, and SiteLink Image Manager 3.0 software. See the applicable SonoSite accessory user guide for information on the accessories. System peripherals include medical grade (conforming to the requirements of EN60601-1) and non-medical (commercial) grade products. System medical grade peripherals include a printer, VCR, and DVD. System non-medical grade peripherals include a CompactFlash card and a Kensington Security Cable. System setup instructions for the use of peripherals are covered in the MicroMaxx Ultrasound System User Guide. Manufacturer’s instructions accompany each peripheral. Instructions for the use of peripherals with the system are covered in the applicable SonoSite accessory user guide.

About the System Software The ultrasound system contains software that controls its operation. A software upgrade may be required for new feature releases. Should an upgrade be required, SonoSite will provide you with a CompactFlash card containing the software. A single CompactFlash card can be used to update one or more systems. Software upgrades use the back CompactFlash slot on the right hand side of the system. CompactFlash cards installed in the front CompactFlash slot do not upgrade the system.

Software Licensing SonoSite software is controlled by a license key, which is obtained from SonoSite or from its authorized representatives. You must obtain one key for each system or transducer that will use the new software. See “Obtaining a License Key” on page 46. The software may be installed and will operate for a short period of time without requiring a valid license key. We refer to this period of time as the “grace period.” The grace period is variable. When you first install your software, your SonoSite system prompts you for a license key. If you have not yet obtained a valid license key, you can elect to use the software as long as the grace period time has not been fully consumed. When a system is running in the grace period, all system functions are available. As you use the system, the grace period is slowly consumed. When the grace period has expired, the system will not be usable until a valid license key has been entered. Grace period time is not consumed while the system is powered off or when it is in “sleep” mode. Whenever a system is running in the grace period, the grace period time remaining is available on the license update screen. Caution:

When the grace period expires, all system functions except for licensing are unavailable until a valid license key is entered into the system.

Chapter 1: Introduction

3

4

Chapter 1: Introduction

Chapter 2: Safety Read this information before using the ultrasound system. The information in this manual applies to the ultrasound system, transducer, accessories, and peripherals. This chapter contains safety information. A WARNING describes precautions necessary to prevent injury or loss of life. A Caution describes precautions necessary to protect the products.

Electrical Safety This system meets EN60601-1, Class I/internally-powered equipment requirements and Type BF isolated patient-applied parts safety requirements. This system complies with the applicable medical equipment requirements published in the Canadian Standards Association (CSA), European Norm Harmonized Standards, and Underwriters Laboratories (UL) safety standards. See the MicroMaxx Ultrasound System User Guide, Specifications chapter. For maximum safety observe the following warnings and cautions. WARNING:

To avoid discomfort or minor risk of patient injury, keep hot surfaces away from the patient. Under certain circumstances, the transducer connector and back of the display enclosure can reach temperatures that exceed EN60601-1 limits for patient contact, therefore only the operator shall handle the system. This does not include the transducer face. To avoid discomfort or minor risk of operator injury when handling the transducer connector, the system should not be operated for more than 60 minutes continuously in a live-scan mode (as opposed to freeze or sleep modes). To avoid the risk of electrical shock or injury, do not open the system enclosures. All internal adjustments and replacements, except battery replacement, must be made by a qualified technician. To avoid the risk of injury, do not operate the system in the presence of flammable gasses or anesthetics. Explosion can result. To avoid the risk of electrical shock, use only properly grounded equipment. Shock hazards exist if the power supply is not properly grounded. Grounding reliability can only be achieved when equipment is connected to a receptacle marked “Hospital Only” or “Hospital Grade” or the equivalent. The grounding wire must not be removed or defeated. To avoid the risk of electrical shock, before using the transducer, inspect the transducer face, housing, and cable. Do not use the transducer if the transducer or cable is damaged. To avoid the risk of electrical shock, always disconnect the power supply from the system before cleaning the system. To avoid the risk of electrical shock, do not use any transducer that has been immersed beyond the specified cleaning or disinfection level. See the MicroMaxx Ultrasound System User Guide. To avoid the risk of electrical shock and fire hazard, inspect the power supply, AC power cord, and plug on a regular basis. Ensure they are not damaged. To avoid the risk of electrical shock, use only accessories and peripherals recommended by SonoSite, including the power supply. Connection of accessories and peripherals not recommended by SonoSite could result in electrical shock. Contact SonoSite or your local representative for a list of accessories and peripherals available from or recommend by SonoSite. To avoid the risk of electrical shock, use commercial grade peripherals recommended by SonoSite on battery power only. Do not connect these products to AC mains power when using the system to scan or diagnose a patient/subject. Contact SonoSite or your local representative for a list of the commercial grade peripherals available from or recommended by SonoSite.

Chapter 2: Safety

5

WARNING:

To avoid the risk of electrical shock, inspect cables and power cords used within the system on a regular basis for damage. To avoid the risk of electrical shock to the patient/subject, do not touch the system battery contacts while simultaneously touching a patient/subject. To prevent injury to the operator/bystander, the transducer must be removed from patient contact before the application of a high-voltage defibrillation pulse. To avoid possible electrical shock or electromagnetic interference, verify proper operation and compliance with relevant safety standards for all equipment before clinical use. Connecting additional equipment to the ultrasound system constitutes configuring a medical system. SonoSite recommends verifying that the system, all combinations of equipment, and accessories connected to the ultrasound system comply with JACHO installation requirements and/or safety standards such as AAMI-ES1, NFPA 99 OR IEC Standard 60601-1-1 and electromagnetic compatibility standard IEC 60601-1-2 (Electromagnetic compatibility), and are certified according to IEC Standard 60950 (Information Technology Equipment (ITE)).

Caution:

Do not use the system if an error message appears on the image display: note the error code; call SonoSite or your local representative; turn off the system by pressing and holding the power key until the system powers down. To avoid increasing the system and transducer connector temperature, do not block the airflow to the ventilation holes on the side of the system.

Equipment Safety WARNING:

To avoid the risk of a burn hazard, do not use the transducer with high frequency surgical equipment. Such a hazard may occur in the event of a defect in the high frequency surgical neutral electrode connection.

To protect your ultrasound system, transducer, and accessories, follow these precautions. Caution:

Excessive bending or twisting of cables can cause a failure or intermittent operation. Improper cleaning or disinfecting of any part of the system can cause permanent damage. For cleaning and disinfecting instructions, see the MicroMaxx Ultrasound System User Guide. Do not submerge the transducer connector in solution. The cable is not liquid-tight beyond the transducer connector/cable interface. Do not use solvents such as thinner or benzene, or abrasive cleaners on any part of the system. Remove the battery from the system if the system is not likely to be used for some time. Do not spill liquid on the system. Accessible metal of the mini-dock is not protectively earthed. Do not perform high current grounding impedance test involving this part.

6

Chapter 2: Safety

Battery Safety To prevent the battery from bursting, igniting, or emitting fumes and causing personal injury or equipment damage, observe the following precautions. WARNING:

The battery has a safety device. Do not disassemble or alter the battery. Charge the batteries only when the ambient temperature is between 0° and 40°C (32° and 104°F). Do not short-circuit the battery by directly connecting the positive and negative terminals with metal objects. Do not heat the battery or discard it in a fire. Do not expose the battery to temperatures over 60°C (140°F). Keep it away from fire and other heat sources. Do not charge the battery near a heat source, such as a fire or heater. Do not leave the battery in direct sunlight. Do not pierce the battery with a sharp object, hit it, or step on it. Do not use a damaged battery. Do not solder a battery. The polarity of the battery terminals are fixed and cannot be switched or reversed. Do not force the battery into the system. Do not connect the battery to an electrical power outlet. Do not continue recharging the battery if it does not recharge after two successive six hour charging cycles. If the battery leaks or emits an odor, remove it from all possible flammable sources.

Caution:

To avoid the battery bursting, igniting, or emitting fumes from the battery and causing equipment damage, observe the following precautions: Do not immerse the battery in water or allow it to get wet. Do not put the battery into a microwave oven or pressurized container. If the battery emits an odor or heat, is deformed or discolored, or in any way appears abnormal during use, recharging or storage, immediately remove it and stop using it. If you have any questions about the battery, consult SonoSite or your local representative. Store the battery between -20°C (-4°F) and 60°C (140°F). Use only SonoSite batteries. Do not use or charge the battery with non-SonoSite equipment. Only charge the battery with the system.

Chapter 2: Safety

7

Biological Safety Observe the following precautions related to biological safety. WARNING:

Non-medical (commercial) grade peripheral monitors have not been verified or validated by SonoSite as being suitable for diagnosis. Do not use the system if it exhibits erratic or inconsistent behavior. Discontinuities in the scanning sequence are indicative of a hardware failure that must be corrected before use. Do not use the system if it exhibits artifacts on the LCD screen, either within the clinical image or in the area outside of the clinical image. Artifacts are indicative of hardware and/or software errors that must be corrected before use. Some transducer sheaths contain natural rubber latex and talc, which can cause allergic reactions in some individuals. Refer to 21 CFR 801.437, User labeling for devices that contain natural rubber. Perform ultrasound procedures prudently. Use the ALARA (as low as reasonably achievable) principle and follow the prudent use information concerning MI and TI. SonoSite does not currently recommend a specific brand of acoustic standoff. If an acoustic standoff is used, it must have a minimum attentuation of .3dB/cm/MHz. Some SonoSite transducers are approved for intraoperative applications if a market-cleared sheath is used.

Labeling Symbols Labeling symbols for SonoSite products can be found in the user guide for each product.

8

Chapter 2: Safety

Chapter 3: System Overview System Overview The SonoSite High-Resolution Ultrasound System (MicroMaxx) is a full featured, general purpose, software controlled, diagnostic ultrasound system used to acquire and display high-resolution, real-time ultrasound data in 2D, M-Mode, Pulsed Wave (PW) Doppler, Continuous Wave (CW) Doppler, Color Power Doppler, and Velocity Color Doppler or in a combination of these modes. The System has an electrocardiography (ECG) display feature and supports a 3-lead ECG cable assembly to collect data for M-mode and Doppler measurements. The System provides measurement capabilities for anatomical structures and fetal biometry that provide information used for clinical diagnostic purposes. The System has a PW and CW Doppler audio output feature and cine review, image zoom, labeling, biopsy, measurements and calculations, image storage and review, printing, and recording capabilities. The system includes the ability to measure the intima-media thickness (IMT) of the carotid artery using digital ultrasound images. The IMT measurement of the carotid artery may be used adjunctively with other medical data obtained by a physician to help assess the cardiovascular health of a patient. The system includes Digital Imaging and Communications (DICOM) capabilities as well as general computer communication capabilities to provide the acceptance, transfer, display, storage, and digital processing of ultrasound images and loops. Security support is also provided to facilitate HIPAA compliance. The System/Transducer is capable of exceeding a TI or an MI of 1.0 in certain operating modes or mode combinations. The System monitor displays the current output level in terms of one of two bioeffects indices (“Mechanical Index [MI]” and “Thermal Index [TI]”) in accordance with the AIUM/NEMA Standard for Real Time Display of Thermal and Mechanical Acoustic Output Indices on Diagnostic Ultrasound Equipment.

Chapter 3: System Overview

9

Theory of Operation The SonoSite High-Resolution Ultrasound System (MicroMaxx) has seven (7) major functional groups: • Transducer • Acquisition Subsystem • Processing Subsystem • Display Subsystem • Control Subsystem • User Interface Subsystem • Power Subsystem Figure 3.1 is a system block diagram that shows the relationship of the functional groups. External video to monitor, VCR, printer Acquisition RF Bus Processing AQ Bus Display subsystem subsystem subsystem

Video User interface IrDA

Control Bus

Control subsystem

Serial Bus Power subsystem Battery pack assembly

Display power Transducer

Logic power Pulser voltage

Power adapter

External power

Figure 3.1 SonoSite High-Resolution Ultrasound System (MicroMaxx) Block Diagram The Transducer elements convert the pulser voltage to acoustic energy during the transmit portion of the ultrasound acquisition cycle. The elements convert the acoustic echo to voltage in the receive portion of the acquisition. The voltage developed on the transducer elements is sensed by the acquisition subsystem. The system transducers have 64 to 128 elements. The Acquisition Subsystem consists of the beamformer and interface to the transducer. The beamformer times the transmit pulses to focus the acoustic beam. The beamformer amplifies the low-level echo signal and times the receive information to focus the receive information. The system beamformers up to 64 transmit elements and 64 receive elements. The Processing Subsystem includes capabilities for interfacing with the beamformer and performing high speed processing. The processing subsystem demodulates, filters, detects, and compresses the signal supplied by the beamformer into display information. The Display Subsystem converts the detected ultrasound data into picture elements (pixels). The software user interface graphics are combined with the ultrasound information and converted to a video stream. The external video port supports NTSC and PAL format.

10

Chapter 3: System Overview

The Control Subsystem consists of the central processing unit, program and video memory, permanent image storage and retrieval memory, external communication interface ports, and connection to the user interface keys. The control software includes the acoustic power and intensity software subsystem, power group monitors, and a beamformer monitor. This software guarantees a level of patient safety by ensuring the system is operating within acoustic power and intensity limits. The User Interface Subsystem represents the software interface and form factor. The software interface is the interaction between the user and the screen layout components. The form factor is the type of physical buttons, location, and grouping of the buttons and the device size, shape, and weight. Dedicated controls are for high usage activities and grouped according to the user workflow. The Power Subsystem provides the system power and protects the hardware from destructive and/or unsafe conditions by detecting failures in the system through hardware and software monitors. Detection of a fault results in disabling of the pulser supply, and signaling of an error to the Control Group. The power subsystem includes the battery pack and battery charging electronics.

Description of Operating Modes

2D Mode

2D mode is a two dimensional image of the amplitude of the echo signal. It is used for location and measurement of anatomical structures and for spatial orientation during operation of other modes. In 2D, a two-dimensional cross-section of a 3-dimensional soft tissue structure such as the heart is displayed in real time. Ultrasound echoes of different intensities are mapped to different gray scale or color values in the display. The outline of the 2D cross-section may be a rectangle, parallelogram, trapezoid, sector, or a full circle, depending on the particular transducer used. 2D mode can be used in combination with any other modes.

M Mode

“M Mode” is also known as “T-M mode” or “time-motion” mode. It is used primarily for cardiac measurements such as valve timing and septal wall thickness when accurate timing information is required. Ultrasound echoes of different intensities are mapped to different gray scale values in a scrolling display. M Mode displays time motion information of the ultrasound data derived from a stationary beam. Depth is arranged along the vertical axis with time along the horizontal axis. M Mode can be used alone but is normally used in conjunction with a 2D image for spatial reference. The 2D image has a graphical line (M-line) superimposed on the 2D image indicating where the M Mode beam is located.

Color Power Doppler (CPD)

In CPD, a real-time two-dimensional cross-section of blood flow is displayed. The 2D cross-section may be presented as a rectangle, parallelogram, trapezoid, sector, or a full circle, depending on the particular transducer used. The 2D cross-section is presented as a full color display, with various colors being used to represent the power in blood flow echoes. Often, to provide spatial orientation, the full color blood flow cross-section is overlaid on top of the gray scale cross-section of soft tissue structure (2D echo). For each pixel in the overlay, the decision of whether to display CPD, gray scale (echo) information or a blended combination is based on the relative strength of echoes from the soft-tissue structures and from the red blood cells. A high pass filter (wall filter) is used to remove the signals from stationary or slowly moving structures. Tissue motion is discriminated from blood flow by assuming that blood is moving faster than the surrounding tissue, although additional parameters may also be used to enhance the discrimination. The power in the remaining signal after wall filtering may be averaged over time (persistence) to present a steady state image of blood flow distribution.

Chapter 3: System Overview

11

Continuous Wave (CW) Doppler

CW provides a real-time representation of blood flow and is displayed as a velocity-versus-time sweeping output. Velocity (or frequency) is presented as the vertical axis with time along the horizontal axis. The magnitude of the detected signal is represented as different gray scale values. CW Doppler mode provides the clinician with the ability to obtain blood flow velocities focused about a user specified focal region. A continuous transmit waveform of ultrasound energy with a known frequency is transmitted and focused by the System; on the receive side, the transducer receive echoes are continuously amplified, focused about the focal region and converted to a base band quadrature signal. The signal is analyzed by a quadrature phase detector that establishes two receive channels to allow detection of flow direction. These two channels are then analyzed by a fast complex Fourier transform (FFT) circuit to establish the spectrum of frequencies present in the echoes. The data are displayed as spectrum frequencies with respect to time. CW can be used alone but is normally used in conjunction with a 2D image for spatial reference. The 2D image has a graphical line (D-line) superimposed on the 2D image indicating where the M-mode beam is located.

Pulsed Wave (PW) Doppler

PW provides a real-time representation of blood flow and is displayed as a velocity-versus-time sweeping output. Velocity (or frequency) is presented as the vertical axis with time along the horizontal axis. The magnitude of the detected signal is represented as different gray scale values. The ultrasound data is derived from a single area, the sample volume, on a stationary beam. PW Doppler mode provides the clinician with the ability to obtain blood flow velocities about a spatial sample volume. A burst of ultrasound with a known spectrum is transmitted by the System; on the receive side, the transducer receive echoes are amplified and range gated at the appropriate depth. The signal is analyzed by a quadrature phase detector that establishes two receive channels to allow detection of flow direction. These two channels are then analyzed by a fast complex Fourier transform (FFT) circuit to establish the spectrum of frequencies present in the echoes. The data are displayed as spectrum frequencies with respect to time. PW can be used alone but is normally used in conjunction with a 2D image for spatial reference. The 2D image has a graphical line (D-line) superimposed on the 2D image indicating where the M-mode beam is located. The sample volume position (depth) and size are also indicated on the D-Line.

The Doppler functional processing platform is in Figure 3.2.

12

Chapter 3: System Overview

DIS Peak & mean

AVG

CMP

Temporal Averaging

Compress

Back End Baseline shift

Display interpolate

RES

FFT

128/192/256/384 samples per line

128 samples @ 50/100/200 Hz

QBP QBP

WAF PRF

RF (PW) or Quadrature basband input (CW)

Wall filter 128 tap FIR

Post gain

PRF

Resample

MAG

Window

FFT

128 IQ pairs @ 1 kHz

|.| 128 samples @ 1 kHz

Audio Output I

Hilbert phase shifter

+

+

Audio gain

+

2x16 bits @ PRF rate

+

Indicates IQ pairs Q

Delay

_

+

Audio gain

Figure 3.2 Doppler Processing Block Diagram The Doppler processing platform can be partitioned into eight (8) blocks: • Wall filter • Resampler • Hilbert phase shifter (stereo separator) • Audio output • Fast Fourier transformer (FFT) • Magnitude estimation • Temporal averaging • Compression

Wall Filter

The wall filter is a high pass filter used to remove the clutter velocity information or wall motion signal.

Resampler

Time domain Doppler samples are transformed into spectral lines using a fast Fourier transform (FFT) technique. The resampler module does the selection of a sample set used for computing windowed FFTs. It thus interfaces the processing thread operating at the PRF rate with the one that computes FFT on segments of data separated at the FFT rate.

Hilbert Phase Shifter and Audio Output

The gain adjusted IQ stream from the wall filter is processed by a Hilbert Transformer to shift an in-phase component by 90 degrees to present the Doppler signal as stereo audio. The 90 degree phase shift in the in-phase component is accomplished by convolving it with the Hilbert Transform impulse response. The quadrature component data stream does not undergo any filtering other than a delay that matches the group delay of the in-phase channel. This is followed by a stage that computes the sum and difference of in-phase and quadrature components to produce stereo audio data.

Fast Fourier Transformer

This module applies a window function to the IQ sample set selected for spectral estimation followed by the FFT. Radix 2 decimation-in-time FFT is performed using block-floating scaling to retain maximum precision. The resulting output is later normalized during magnitude computation.

Chapter 3: System Overview

13

Magnitude Estimation

This module combines real and imaginary components to estimate magnitude spectrum. The magnitude of Doppler spectrum is calculated using “cordic approximation”, which is done by estimating the complex magnitude by successive approximation. The vectors are reflected into the first quadrant by taking the absolute value, then rotating them sequentially by halved degrees.

Temporal Averaging

Spectral lines are produced by the FFT module at a constant rate. This module averages the appropriate number of spectral lines to produce output lines at the desired display scroll rate.

Compression

The compression module maps the input spectral magnitude values to display output values.

Velocity Color Doppler (VCD) In Velocity Color Doppler, a real-time, two-dimensional cross-section of blood flow is displayed. The 2D cross-section may be presented as a rectangle, parallelogram, trapezoid, sector, or a full circle, depending on the particular transducer used. The 2D cross-section is presented as a full color display, with various colors being used to represent the velocity, both positive and negative, of the blood flow echoes. Often, to provide spatial orientation, the full color blood flow cross-section is overlaid on top of the gray scale cross-section of soft tissue structure (2D echo). For each pixel in the overlay, the decision of whether to display VCD, gray scale (echo) information or a blended combination is based on the relative strength of echoes from the soft-tissue structures and from the red blood cells. A high pass filter (wall filter) is used to remove the signals from stationary or slowly moving structures. Tissue motion is discriminated from blood flow by assuming that blood is moving faster than the surrounding tissue, although additional parameters may also be used to enhance the discrimination. The remaining signal after wall filtering may be averaged over time (persistence) to present a steady state image of blood flow distribution. Variance information may also be displayed to provide information when large variance is observed in the velocity information.

14

Chapter 3: System Overview

Additional System Feature Performances

Broadband Imaging

This ultrasound acquisition system uses high resolution uses broadband technology in the transmit pulsers, transducer, and receivers. The receive path can capture and process signals over a wide spectrum, from below 2.0 MHz to beyond 10 MHz. For each application, the transmit pulse is designed to produce an appropriate bandwidth. For example, in 2D grayscale imaging, a wide band pulse is used to support good axial resolution. For Doppler modes, a narrower band pulse is used, which improves the spectral resolution of the detected Doppler signal. In addition to transmit pulse control, programmable digital signal processing is used in the receive path to further refine the bandwidth used to produce the final image. Digital filters are applied to the digitized received signal to limit and shape the spectral bandwidth used to generate the displayed output.

Tissue Specific Imaging

In this feature, parameters for signal and image processing are optimized to maximize the image quality or to obtain the best compromise of resolution and penetration for different specific clinical applications. These parameters include: the order of received filters, the bandwidth, the dynamic range, the compression curve, the gain setting and parameters for compounding frequency band, etc. For example, different system parameter setups are used for abdominal or peritoneal scanning. This feature is for ease of use for the operator by automatically setting up system control parameters rather than manually adjusting settings for best performance.

Biopsy Guidance

The System is capable of displaying a pair of biopsy guidelines that represent the anticipated path of the biopsy needle. The image of an anatomical target, biopsy guidelines, a scan plane marker, and a biopsy needle are displayed on the monitor to assist in guiding the biopsy needle to the target. The system also provides needle guidance for vascular access procedures. Additional information regarding this feature can be found in the biopsy user guides.

Measurement and Calculation Capabilities

The System offers a variety of measurements and calculations, specific to exam type and transducer. A listing of the volume, cardiac, Doppler and obstetrical calculations and measurements that may be made is provided in the User Guide, in the chapter Measurements and Calculations, and author reference in provided the chapter References. Measurement accuracy is discussed the Reference chapter of the User Guide.

Continuous Wave Doppler Audio Output

The system provides for audio output of the CW velocity information. This can be presented as stereo information, with flow moving towards the transducer on one channel and flow away on the other, or as a monaural output with the single audio output representing the summation of the flow directions.

Pulsed Wave Doppler Audio Output

The System provides for audio output of the PW velocity information. This can be presented as stereo information, with flow moving towards the transducer on one channel and flow away on the other, or as a mono output with the single audio output representing the summation of the flow directions.

Electrocardiograph (ECG) Display

ECG is provided to measure the electrical signal generated by the heart. A three lead interface: Right Arm (RA), Left Arm (LA) and Left Leg (LL), is provided on the System. The ECG signal is displayed as an amplitude-versus-time sweeping output. Amplitude is presented on the vertical axis with time along the horizontal axis.

Chapter 3: System Overview

15