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Kwon, Ji-YoungApplication Chief Manager
Ultrasound Division
Canon Medical Systems Korea
Associates Course(10:40 – 11:20)
June 6th, 2019
1. Ultrasound Instruments
2. Image Mode
3. Quality Assurance
Contents
2
1. Ultrasound Instruments
(1) Main System
(2) Transducers
2. Image Mode
3. Quality Assurance
Contents
3
Advantages & Disadvantage of Ultrasound
4
Main advantages
Noninvasive examination
Possible to observe cross-sectional images in real-time
System itself is compact (Easy to be installed and moved to wards)
Main disadvantages
Need experience for proper operation, and lack reproducibility a little
Ultrasound Main Body System
5
1) Pulser : produces electrical voltage bursts.
2) Transducer : vibrates to convert electrical voltage into pulse of
ultrasound, and again convert echo into tiny electrical voltage called
“echo signal”.
3) Receiver : amplifies received signal.
4) Memory : stores in memory until complete image is created.
5) Display : displays on monitor in real-time with frame averaging
15~30 fps.
6) Recording Device : film cameras, laser cameras, printer, video
recorders, PACS, etc.
Principle of Real-time Scanning
6
1. Electronic Scanning
- Broad bandwidth electronic arrays
- Electronic focusing
- Conventional transducers
2. Mechanical Scanning
- Contains moving part (crystal or mirror) within transducer
- Fixed focus
- 3D/4D transducers
Ultrasound Transducers
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1. Linear Array Transducers
- Linear switched arrays : subgroup firing of elements in sequential
fashion
- Rectangular FOV : all scan lines are parallel to each other
- Mainly used for superficial region : breast, thyroid, MSK, vessel, etc.
Elements
Scanning lines
Ultrasound Transducers
8
2. Convex Array Transducers
- Curved switched arrays : subgroup firing of elements in sequential
fashion with wide arc
- Fan-shaped FOV : scan lines are not parallel to each other
- Mainly used for abdomen, pelvis, OB, etc.
Elements
Scanning lines
Ultrasound Transducers
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3. Phased Array Transducers
- Generally called sector transducer : phasing delays to steer with
firing all elements together
- Pie-shaped FOV : fewer elements and much smaller foot print
- Mainly used for cardiac, TCS, etc.
Elements
Scanning lines
Ultrasound Transducers
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4. Matrix Transducers
- Generally called 1.5D arrays transducer
- Electronic focusing in slice thickness plane
- More uniform image than conventional array transducers
Matrix
1.5D Array
Conventional
1D Array
Scan plane
Slice thickness
plane
1. Ultrasound Instruments
2. Image Mode
(1) B Mode
(2) Color Mode
(3) Doppler Mode
3. Quality Assurance
Contents
11
Principle of Display Modes
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1. A-mode (Amplitude mode)
- First form of echo display
- Presented as vertical spikes along horizontal baseline
2. B-mode (Brightness mode)
- Generally called 2D mode presented by brightness of dot
3. M-mode (Motion or Time-motion mode)
- Produced by tracking single B-mode scan line orienting it vertically
4. Doppler mode
- Color flow display with mapping or spectral display with waveform
using Doppler shift calculated by Doppler equation
5. 3D/4D mode
- Obtained by series of 2D slices of volume of tissue and
constructing by computer
- Static or real-time displays
B Mode Optimization
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1. Overall Gain
- Amplification function of RF signal
- Increases brightness of all echoes in image
Brighter
Darker
Proper gain setting
-> uniform quality
Under gain setting
-> too dark and not clear
Over gain setting
-> too bright on the higher
echogenic part
B Mode Optimization
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2. TGC or STC
- Compensation function in depth direction
- Adjusts with same brightness regardless of their location in anatomy
Proper TGC setting Improper TGC setting
B Mode Optimization
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3. Depth Range
- Determines PRF and affects frame rate
- Effect of magnification
Shallower display
Deeper display
Normal depth setting Proper depth setting
for GB polyp observation
Depth and FOV adjustment
-> higher frame rate
B Mode Optimization
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4. Focus
- A process of reducing beam width
- Improves lateral resolution and increases spatial intensity and sensitivity
Shallow position
-> poor quality except near field
Medium position
-> uniform quality
Deep position
-> improved quality in deep part
B Mode Optimization
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5. Frequency
- Trade-off between resolution and penetration
- Improves axial resolution in higher frequency
- Improves penetration in lower frequency
Deep penetration mode
High resolution mode
High frequency
-> good resolution, but less power
Standard frequency
-> medium quality
Low frequency
-> good penetration in far field,
but less resolution in near field
Doppler Mode
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1. Doppler Effect
- Wave phenomenon in which there is change in frequency and wavelength of wave due to
motion between source of wave and receiver.
2. Doppler Shift Frequency
- Difference(Fd) between received frequency(Fr) and transmitted frequency(Ft)
3. Doppler Equation
Color Doppler Mode
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1. Color Flow Imaging
- Doppler shifts are detected within “color box”.
- It is possible to know the blood flow direction.
- In general, the blood flow coming close to the probe is displayed in red
color, and the flow going away from the probe is displayed in blue color.
2. Power Doppler Imaging
- Signals colored according to the intensity of Doppler signal are displayed.
- High flow volume is displayed bright and low flow volume dark.
3. High Resolution Doppler Imaging
- Increased sensitivity to flow, so useful for slow flow or small vessels.
- Improves color spatial resolution, so less blooming artifact.
4. Micro Flow Imaging
- Latest color Doppler technique for micro-vascular flow.
- Excellent for low velocity flow with less clutter artifact.
Superb Micro-vascular Imaging Monochrome SMI
Spectral Doppler Mode
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1. Pulsed Wave Doppler
- Provides most detail about blood flow : not only presence and direction, but additional
information such as blood velocity and detailed characteristics of flow.
- Only Doppler shift from within sample volume is evaluated, giving good range resolution.
2. Continuous Wave Doppler
- Most use of echocardiography.
- Not transmitting pulses, but continuous stream, and no range resolution.
Continuous Wave
Pulsed Wave
Color Mode Optimization
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1. Color Gain
- Start with higher setting, then reduce gain as appropriate without noise
More color
Less color
Color Mode Optimization
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2. Scale
- Controls PRF and determines velocity range
- Appropriate without aliasing
Lower velocity range
Higher velocity range
< CCA distal > < ICA proximal > < ICA proximal >
Velocity range : 28.8 cm/s Velocity range : 28.8 cm/s Velocity range : 38.4 cm/s
Color Mode Optimization
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3. Color Box Steering
- Angle between color box and blood flow
- 10~30 degrees to flow direction
Left side steering Right side steering
CCA distal - Neutral CCA distal - 20° steering to Rt.
ICA prox. - 20° steering to Rt. ICA prox. - 10° steering to Lt.
PW Mode Optimization
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1. Doppler Gain
- Same procedure as used for color Doppler
Stronger signal
Weaker signal
Proper gain setting
-> peak velocity is seen well
Under gain setting
-> weak signal of spectrum
Over gain setting
-> too strong signal with
background noise
PW Mode Optimization
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2. Baseline
- Optimize display scale for particular flow without aliasing
- Typically baseline is adjusted first, then Doppler scale
PW Mode Optimization
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3. Scale
- Set to display blood velocity and accurately determine velocity
Lower velocity range
Higher velocity range
< Vert. A > < Vet. A > < ICA proximal >
Velocity range : 100 cm/s Velocity range : 70 cm/s Velocity range : 120 cm/s
PW Mode Optimization
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4. Doppler Cursor Steering
- Angle between pulsed Doppler cursor line and blood flow
- 10~30 degrees to flow direction
- Mostly activates with color box steering, but can control independently
Left side steering Right side steering
10° steering - underestimation 20° steering 30° steering - over estimation
< Same Scale Condition >
PW Mode Optimization
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5. Doppler Angle Correction
- To calculate blood velocity accurately
- Try to correct at 30~60 degrees, but not at greater than 60 degree
- No need to correct angle if you want to measure RI value
60° correction 30° correction - underestimation 0° - no correction
< Same Steer Angle >
Pitfalls in Color & PW Doppler Interpretation
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Common mistake is to assume that lighter shades of color close to Nyquist limit
indicate faster moving blood in Color Doppler.
Lighter shades of color indicate higher Doppler shifts
Color represents Doppler shifts, not blood velocity
= Positive channel
= Negative channel
Pitfalls in Color & PW Doppler Interpretation
30
Second common error is to assume that shifts above baseline are positive in PW
Doppler.
Positive channel Negative channel
Negative channel Positive channel
1. Ultrasound Instruments
2. Image Mode
3. Quality Assurance
(1) QA Test
(2) Cleaning, Disinfecting, and Sterilization
Contents
31
Quality Assurance
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What is quality assurance program?
- All procedures necessary to maintain proper and consistent equipment operation
- To keep diagnostic quality of US image
- Good quality assurance will ┌ ensure proper equipment operation
├ detect gradual changes in performance
├ minimize equipment down time
├ reduce number of repeat scans
└ optimize operator and patient safety
Ultrasound QA Device
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Tissue-mimicking phantom
ATS-539 (USA)
Ultrasound QA Test
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Dead Zone : ring-down zone or ring-down space
Axial Resolution : along length of beam
Lateral Resolution : across beam
Gray Scale and dynamic range
Vertical measurement : range accuracy (depth calibration accuracy)
Horizontal measurement : horizontal accuracy (lateral accuracy)
Sensitivity : maximum depth of penetration
Focal Zone : beam Profile (shape of beam)
Functional Resolution : uniformity (definition and fill-in)
Conformance Criterion
Conformance Reference
Reference
Equipment Cleaning, Disinfecting, and Sterilization
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Cleaning (Cleansing)
- Removal of soil, hence reduction in numbers of microorganisms from surface
- By washing with Soap and water, or wiping with 70% Alcohol (Ethyl alcohol, Enzyme)
- Essential first step prior to either disinfection or sterilization
- Appropriate for transducer used for normal abdominal scanning
Disinfecting
- Inactivation of vegetative bacteria, viruses and fungi, but not bacterial spores
- By Boiling method, Glutaraldehyde (Metricide, Cidex, Widex, Procide)
- Used in contact with intact mucous membranes
- Essential for vaginal transducer
Sterilization
- Complete destruction of microorganisms, including bacterial spores
- By Autoclaving(steam under pressure), Ethylene Oxide(EO gas), Plasma
- Most common approach when used in operating room
- Simple method of maintaining sterility : to cover transducer with sterile sheath
36
Thank You for Your Attention
