2. Learning Objectives
To comprehend the fundamentals of ultrasound
dynamics.
To demonstrate successful theoretical and clinical
manipulation regarding vascular access.
To be able to analyze and interpret various vascular
access risks and benefits.
To introduce and integrate ultrasound theoretical
frameworks with a clinical didactic.
5. History of Ultrasound
1794 – Physiologist Lazzaro Spallanzani: first to study echolocation in bats, which forms the
basis for ultrasound physics.
1877 – Brothers, Pierre and Jacques Currie discover piezoelectricity. Ultrasound transducers
(probes) emit and receive sound waves by way of the piezoelectric effect.
1915 – After the sinking of the Titanic, Physicist Paul Langevin was commissioned to invent a
device that detected objects at the bottom of the sea. He invented a hydrophone – considered
the first “transducer
1942 – Neurologist Karl Dussik is the first to use sonography for detecting brain tumors.
1948 – George D. Ludwig, M.D., (US Naval Medical Research Institute), developed A-mode ultrasound
equipment to detect gallstones.
6. History of Ultrasound (continued)
1953 – Physician Inge Edler and Engineer C. Hellmuth Hertz performed the first
successful echocardiogram using an echo test control device from a Siemens shipyard
1958 – Dr. Ian MacDonald incorporated ultrasound into the OB/GYN field of medicine.
1966 – Don Baker, Dennis Watkins, and John Reid designed pulsed Doppler
ultrasound technology; their developments led to imaging blood flow in various layers of
the heart.
1980s – Kazunori Baba (University of Tokyo), developed 3D ultrasound technology and
captured three-dimensional images of a fetus in 1986.
1989 – Professor Daniel Lichtenstein began incorporating lung and general
sonography in intensive care units.
1990s – Starting in the 1980s, ultrasound technology became more sophisticated with
improved image quality and 3D imaging capabilities.
7. Basic Physics of Ultrasound
Frequency: refers to the
number of cycles of
compressions and
rarefactions in a sound wave
per second.
8. Basic Physics of Ultrasound
(Continued)
Wavelength (λ): Distance traveled by
sound in one cycle, or the distance
between two identical points in the wave
cycle i.e., the distance from point to
point.
The smaller the wavelength (and
therefore higher the frequency), the
higher the resolution, but lesser
penetration. Therefore, higher frequency
probes (5 to 10 MHz) provide better
resolution but can be applied only for
superficial structures and in children.
9. Basic Physics of Ultrasound
(Continued)
Propagation velocity: Speed at
which sound travels through a
particular medium and is dependent
on the compressibility and density of
the medium.
Usually, the more dense the tissue,
the faster the propagation velocity.
The average velocity of sound in soft
tissues, such as the chest wall and
heart, is 1,540 meters/second.
10. Transducer: Inside the core of the transducer are a
number of piezo-electric crystals which produce
frequency.
Orientation: There is usually
a dot, groove or light on one ends
of the transducer to assist with
orientation.
11. Medical Ultrasound Limitations
Ultrasound waves are disrupted by gas or air. It is
not to be used primarily for bowel assessment. CT
scanning and radiology are appropriate diagnostic
measures
Large patients have limitations due to more dense
tissue which attenuates the sound waves, thus
producing poor quality.
Ultrasound waves do not penetrate solid objects
such as bone.
15. Ultrasound Basics
A convex probe “cardiac/abdominal
probe” uses a lower frequency,
thus allowing for deeper tissue
penetration, suboptimal resolution
compared to linear probe.
A linear probe “vascular probe” uses
a higher frequency range allowing
for higher image resolution.
Linear Probe
Convex Probe
16. Ultrasound Handling:
Three Basic Motions
1. Sliding – Moving the
probe up down along the
long axis of the probe
2. Rocking – Tilting the
probe up & down in the
long axis of the probe while
holding it in one location.
3. Fanning – Rotating the
probe like a fan, while
holding it in one location.
Remember, ultrasound is
made up of waves, think of
the ocean! When waves hit
the shore they scatter
17. Visual Specifications
When viewing structures, fluid is black, and
tissue is gray!
The more dense the tissue is, the brighter it
will appear.
• Ultrasound waves will not penetrate bone.
• Echogenicity describes how ultrasound
waves are reflected back to the transducer.
• Hypoechoic = less transmission
• Hyperechoic = more transmission
18. Long axis view
versus
Short access view.
24. What happens to the ultrasound waves
once they enter the body?
Only some of the waves return back to the probe
to help the machine form a image. The rest are
lost.
When ultrasound waves enter the body, the
waves undergo the following processes:
1. Attenuation
2. Refraction
3. Reflection
25. Attenuation
Attenuation is when body absorbs some of the
ultrasound energy, making the waves disappear.
These waves don’t return to the probe and are
therefore “wasted”.
Attenuation is a measure of the rate at which the
intensity of the ultrasound beam diminishes as it
penetrates the tissue.
26. Refraction
Every substance, (nerves, muscles, or fat), has a
unique property called “acoustic impedance”.
Substances with different acoustic impedances
alter the course of ultrasound waves in an
important manner.
27. Refraction (continued)
When an ultrasound wave tries to pass from one
substance to another substance with a different
acoustic impedance, Part of the ultrasound
waves continues into the second substance, but
becomes slightly bent away from their original
direction .
The bending away when ultrasound passes from
one substance to another substance with a
different acoustic impedance is called refraction.
28. Reflection
Irregular surfaced objects such as nerves scatter
the ultrasound waves in all directions. A small
portion of the waves are reflected back to the
probe. This is called “scattered reflection”.
If an object is large and smooth like a needle, all
the ultrasound wave is reflected back.
