Transcript Ultrasound Modes

Ultrasound Modes
Ultrasound Modes
A Mode presents reflected ultrasound energy on a single line
display. The strength of the reflected energy at nay particular depth
is visualized as the amplitude of the waveform.
B Mode converts A Mode information into a two dimensional
grayscale display.
C Mode is a color representation of blood flow velocity and direction.
D Mode is a spectral representation of blood flow velocity and
direction.
P Mode is used to visualize very low blood flows in color. Unlike C
Mode, this mode does not show the operator flow direction.
Triplex is the simultaneous operation of B Mode, C Mode and D
Mode.
M Mode is a scrolling display allowing the operator to view and
record organ motion.
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Axial Resolution
Another concern is Resolution. •
Axial resolution is corresponds directly to the wave •
length characteristics of the Ultrasound wave. As
frequency increases wave length shortens allowing for
greater resolution. What we loose is penetration. Again
as frequency increases penetration decreases. Higher
frequencies also provide finer tissue grain or
smoothness. A less grainy look.
Lateral resolution
In simple ultrasound systems Lateral •
resolution is attributed to physical focus
characteristics of the crystal element. The
concaved shape of the element provides
focus to the beam and the width of the
beam at any particular point effects the
ability of the ultrasound system to resolve
small objects that are side by side.
Transverse resolution
Transverse resolution is unique to the •
phase array probe. It is the ability of the
probe to resolve objects side by side, as in
lateral resolution, but in this case it is
measured transverse to what would be
considered the normal imaging plane.
Again this is assuming simplest probe
construction.
Contrast Resolution
The ability of the system to resolve •
adjacent bright reflectors is called contrast
resolution. This is in small part due to the
cumulative effects of axial and lateral
resolution. The systems scan converter
plays a large role is this characteristic.
Diagnostic Ultrasonography
Displaying Monitor
Transducer / Probe
Keyboard
Probe Connector
Printer (B/W & Color)
• Device that can change one form of energy into another.
Electrical excitation
into
motion and pressure.
• The necessary element for generating acoustic waves.
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Transducer Design
Echoes from Two Interfaces
Echoes from Internal Organ
A- mode
M- mode
B- mode
Doppler
Pulsed
Continuos
CRT
V
Time variable gain
Amp
H.
Pulser
T/R
Saw tooth voltage
sweep
Trigger
switch
Body
Organ
Transducer
Block diagram of an A-scan instrument. A pulser circuit triggers the
transducer, and the saw-tooth generator. The T/R switch isolates the
receiver amplifier during transmission. Amplitudes of the received
echo signals are presented on the vertical axis of the CRT.
Brightness
modulation
CRT
Time variable gain
Vert.
Amp
Horiz.
Pulser circuit
T/R
switch
Beam steering control
unit
Saw tooth voltage
sweep
A pulser circuit triggers the transducer, and the saw tooth generator.
The T/R switch isolates the receiver amplifier during transmission.
For each scanning line, the amplitudes of the received echo signals
are modulated to brightness. Steering unit is controlling the
synchronization process.
Slow voltage ramp
CRT
B
Time variable gain
Vert.
Amp
Horiz.
Pulser circuit
T/R
Sawtooth voltage
sweep
Trigge
r
switch
Body
B
A
Transducer
Fixed
organ
Moving
Organ
TRANSMITTER
RECEIVER
PULSED
CONTINUES
Linear Probe Image
Sector (Phased array) Probe
Convex Probe Image
Real Time 3D
Fetal Spine
Reconstructional 3-D
Obstetrics
Ultrasound Machines
Ultrasound Machines
Function
Diagnostic ultrasound machines are used to give images of structures within the body. This
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chapter does not deal with other kinds of machine (e.g. therapeutic and lithotripsy). The
diagnostic machine probes, which produce the ultrasound, come in a variety of sizes and
styles, each type being produced for a particular special use. Some require a large trolley
for all the parts of the unit, while the smallest come in a small box with only a audio
loudspeaker as output. They may be found in cardiology, maternity, outpatients and
radiology departments and will often have a printer attached for recording images. Unlike
X-rays, ultrasound poses no danger to the human body.
How it works
The ultrasound probe contains a crystal that sends out bursts of high frequency vibrations
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that pass through gel and on through the body. Soft tissue and bone reflect echoes back to
the probe, while pockets of liquid pass the ultrasound straight through. The echoes are
picked up and arranged into an image displayed on a screen. The machine offers a
number of processing options for the signal and image and also allows the user to measure
physical features displayed on the screen. This requires the machine to incorporate a
computer.
WHAT TYPES OF EXAMINATION ARE TO BE
CARRIED OUT ?
1. TRANSDUCER
* Curvilinear or combination of linear and sector.
2. FREQUENCY
* Standard transducer should have central frequency
of 3.5 MHz.
3. ANGLE for Sector probe should be 40 or more, linear
array should be 5 - 8 cm long.
4. FRAM RATE… 15 - 30 Hz for linear array,
5 - 10 Hz for sector array.
5. FRAM FREEZE DENSITY… at least 512*512*4 bits to
provide 16 gray levels
6. ELECTRONIC CALIPERS… one pair at least, with
Quantitative readout.
7. ADD DATA IS POSSIBLE… patient identification,
hospital name, date of examination… etc.
8. HARD COPY… should be possible.
9. MONITOR… at least 13 cm * 10 cm (preferably larger)
10. STABILIZING… should be able to stabilize voltage
variation of +/- 10%.
11. Biometric tables… (it may not be universal and
should be adjusted for local standards.
WHAT WE HAVE TO CHECK
WHEN WE RECEIVE THE SCANER
USER’S MANUAL
SERVICE MANUAL
1. Voltage setting should be compatible with the electrical supply.
2. Interference on the screen/ whit sparks.
3. Transducer and cables test.
4. Check the cursor / measuring length, …
5. Check the accessibility of the biometrics or measurement tables.
Any missing or distorted image that does not
match the real image of the part being examined
• Acoustic characteristics of the tissues.
• Scanner’s settings.
• Lack of user’s experience.
• Defected part within the scanner.
• COMMON ARTIFACTS:
• Cyst’s artifact (strong back-wall effect).
• Abdominal wall artifact.
• Gas artifact.
• Reverberation artifact.
• Incomplete imaging artifact.
• Gain artifact.
• Shadows artifact.
• Visually inspects all transducers.
“Cable, cracked surface, punctured, discolored casing”
• Visually inspect the power cords.
• Verify that the trackball and DGC controls appears clean
and free from gel or other contaminants.
Once the system is powered on:
Verify that the monitor displays CORRECTLY the
connected transducer’s identification, current date, time.
• FOCUS.
• DEPTH GAIN COMPENSATION.
• OVERALL GAIN.
• ZOOM.
• MONITOR (B/C).
TRANSDUCERS
MAIN UNIT
Linear, convex, …..
Surface of the system.
Endocavity, interoperative, …
DGC slides control.
Trackball.
Unit filters.