Transcript Ultrasound in surgery

Ultrasound in surgery
Faisal Ghairat
History of US imaging
• Lazzaro Spallanzi – Physiologist (Italia)
• 1st person to provide that non-audible
sound exist around us.
• Demonstration included that blind
folded bats could navigate around
obstacles in the dark but bumped
against them when their mouths
where covered. (1794)
• Spallazani’s Bat problem
• With time the term echolocation was set:
“bats require their senses of hearing in
order to find their way”
Piezo-electric effect
• Year 1880 was the real breakthrough in ultrasound
technology
• Pierre and Jacques Currie (France) – discovered the
“Piezo-electric effect”: the electrical charge that
accumulates in certain solid materials (crystals, bone,
protein, DNA etc) in response to applied mechanical
stress.
• Lead to development of the ultrasound transducer.
• Transducer is the backbone of any ultrasound –
converts ultrasound waves to electrical signals or vice
versa
Pierre and Jacques
Currie
Ultrasound transducer
The Doppler effect
• Johann Christian Doppler (1803-1853) Austria
• “Hypothesized that the pitch of a sound would
change if the source of the sound was moving”
Doppler effect shortly described: change of
wavelenght caused by motion of the source
Physics of ultrasound (US) imaging
• Sound is energy traveling through matter as a
wave
• The wave travels by compressing matter
• Depending on the matter - the wave will travel
at different velocities or directions
• U/S probes emit and receive the energy as
waves to form pictures
Producing an image
• Probe emits a sound wave pulse - measures
the time from emission to return of the echo
• Wave travels by displacing matter, expanding
and compressing adjacent tissues
• It generates an ultrasonic wave that is
propagated, impeded, reflected, refracted, or
attenuated by the tissues it encounters
Cycle
• 1 Cycle = 1 repetitive periodic oscillation
Frequency
• Number of cycles per second
• Measured in Hertz (Hz)
-Human Hearing 20 - 20,000 Hz
-Ultrasound > 20,000 Hz
-Diagnostic Ultrasound 2.5 to 10 MHz
(this is what we use!)
Wavelength
• The length of one complete cycle
• A measurable distance
Types of transducers
• The essential element of
each ultrasound
transducer is a
piezoelectric crystal,
serving both to generate
and to receive ultrasound
waves.
• The following types of
transducers are most often
used in the critical
ultrasound imaging: sector,
linear and convex
(standard or microconvex).
Sector transducer
• piezoelectric crystal arrangement: phasedarray (most commonly used)
• operating frequency (bandwidth): 1-5 MHz
(usually 3.5-5 MHz)
• use: small acoustic windows, mainly
echocardiography, gynaecological ultrasound,
upper body ultrasound
Linear Transducer
• piezoelectric crystal arrangement: linear
• operating frequency (bandwidth): 3-12 MHz
(usually 5-7.5 MHz)
• use: ultrasound of the superficial structures,
e.g. obstetrics ultrasound, breast or thyroid
ultrasound, vascular ultrasound
Convex transducer
• piezoelectric crystal arrangement: curvilinear,
along the aperture
• operating frequency (bandwidth): 1-5 MHz
(usually 3.5-5 MHz)
• use: useful in all ultrasound types except
echocardiography, typically abdominal, pelvic
and lung (micro-convex transducer)
ultrasound
Important
• An ultrasound transducer is the most important
and usually the most expensive element of the
ultrasound machine, so it should be used
carefuly, which means the following:
• do not throw, drop or knock the transducer,
• do not allow to spoil the transducer`s duct,
• wipe the gel from the transducer after each use,
• do not sluice with alcohol-based confections.
Types of US presentations
• Most ultrasounds are done using a transducer on the
surface of the skin. Sometimes, however, doctors and
technicians can get a better diagnostic image by inserting a
special transducer into one of the body's natural openings:
• In a transvaginal ultrasound, a transducer wand is placed in
a woman’s vagina to get images of her uterus and ovaries.
• A transrectal ultrasound is sometimes used in the diagnosis
of prostate conditions.
• A transesophageal echocardiogram uses the transducer
probe in the esophagus so that the sonographer can obtain
clearer images of the heart.
Transvaginal ultrasound
Transrectal ultrasound
• Additionally,
ultrasound
technology has
advanced to allow for
different types of
imaging:
• Doppler is a special
type of ultrasound
that creates images of
blood flow through
vessels.
• 3D imaging adds
another dimension to
the ultrasound image,
creating threedimensional
interpretations rather
than the flat twodimensional images
that are made with
traditional ultrasound.
A-mode one dimensional
A-mode (amplitude mode) is the simplest type of
ultrasound. A single transducer scans a line through the
body with the echoes plotted on screen as a function of
depth. Today used only in opthalmology
B – mode (brigntness modulation)
• The B mode most
commonly used
today, relates the
brightness of the
image to the
amplitude of the US
wave.
• Thus, denser
sructures appear
brighter (i.e. whiter
more echogenic) on
the image because
they reflect the US
waves better.
M-mode
• The M-mode was the
first ultrasound
modality to record
display moving
echoes from the
heart, and thus the
motion could be
interpreted in terms
of myocardial and
valvular function.
The M-modes were
originally recorded
without access to 2dimensional images.
Doppler Ultrasound
• A Doppler ultrasound test uses reflected sound
waves to see how blood flows through a blood
vessel. It helps doctors evaluate blood flow
through major arteries and veins, such as those
of the arms, legs, and neck. It can show blocked
or reduced flow of blood through narrow areas in
the major arteries of the neck that could cause a
stroke. It also can reveal blood clots in leg veins
(deep vein thrombosis, or DVT) that could break
loose and block blood flow to the lungs
(pulmonary embolism).
Color Doppler
• The direction of blood flow is assigned red
or blue, indicating flow toward or away from
the ultrasound transducer.
Color Doppler
• Transducer perpendicular to radial artery
(no flow is detected)
Color Doppler
• Transducer aiming away from the artery
(flow in Blue)
Color Doppler
• Transducer aiming towards the artery (flow
in Red)
Intraoperative US
• Intraoperative ultrasound (IOUS) is a dynamic
imaging modality that provides interactive and
timely information during surgical procedures.
Because the transducer is in direct contact
with the organ being examined, highresolution images can be obtained that are
not degraded by air, bone, or overlying soft
tissues.
Intraoperative ultrasound (liver)
• Here is a intraoperative picture of liver
metastasis from colorectal cancer
• dfsdf
Laparoscopic ultrasound used in staging of patient
with adenocarcinoma of pancreas
US in fields other than surgery
• Ultrasound is used in many different fields
• E.g like we talked earlier about: Bats and
porpoises, they use ultrasound for locating
prey and obstacles.
• Dogs with normal hearing can hear
ultrasound. A dog whistle exploits this by
emitting a high frequency sound to call to a
dog.
Weapons
• Ultrasound has been
studied as a basis for
sonic weapons, for
applications such as
riot control,
disorientation of
attackers, up to lethal
levels of sound.
Ultrasonic cleaning
• An ultrasonic cleaning is a process that uses
ultrasound (usually from 20–400 kHz) and an
appropriate cleaning solvent (sometimes ordinary
tap water) to clean items e.g jewelry
Examples of US imaging
Acute appendicitis
Spleen injury
• Ultrasound terms:
• Hyperechoic – more echogenic (brighter) than
normal
• Hypoechoic – less echogenic (darker) than
normal
• Isoechoic – the same echogenicity as another
tissue
Remember
• Ultrasound terms:
• Hyperechoic – more echogenic (brighter) than
normal
• Hypoechoic – less echogenic (darker) than
normal
• Isoechoic – the same echogenicity as another
tissue
Remember
• A good mnemonic for echogenicity is:
• “my cat loves sunny places”
• Taking the first letter from each word, the
tissues go from hypoechoic to hyperechoic
relative to each other. The renal medulla
(inner portion of the kidney) is normally more
hypoechoic than the renal cortex (outer
portion of the kidney), which in turn is more
hypoechoic than the liver, spleen and prostate