Chapter 1 Foundations of Sono HA Flashcards
Define sonography.
An allied health professional who uses a specialized imaging technique to view the soft tissue structures of the body.
Define echocardiography.
(Echo) ultrasound examination of the cardiac structures.
ARDMS
American Registry of Diagnostic Medical Sonography
Ultrasound imaging is valuable because:
no radiation, portable, allows real time format, cheaper
Who is Augustin Fresnel?
created the theory of wave optics; theory of wave diffraction named after him
Who is Christian Johann Doppler?
the Doppler effect, which is the apparent change in frequency and wavelength of a wave as perceived by an observer moving relative to the wave’s source.
Who are the Curie brothers?
Peal Jaques and Pierre; discovered piezoelectricity
What does SONAR stand for?
sound navigation and ranging
Who is Dr. Karl Dussik?
made one of the earliest applications of ultrasound to medical diagnosis by positioning two transducers on opposite sides of the head to measure ultrasound transmission profiles.
Who is Dr. William Fry?
the first to introduce the use of computers in diagnostic ultrasound.
Who is Richard Cushman?
along with a team invented a “pan scanner” which was a landmark invention in B-mode ultrasound.
Who are Hertz and Edler?
credited with M-mode (motion) display
Who are Tom Brown and Dr. Ian Donald?
built an early obstetric compound scanner
What is gray scale?
B-mode scanning technique that permits the brightness of the B-mode dots to be displayed in various shades of gray to represent different echo amplitudes
What is acoustics?
the physics study of generating, propagating, and receiving sound waves
What is the range of normal human hearing? What is ultrasound range?
Normal hearing is between 20 Hz and 20 KHz. Ultrasound is above normal hearing at anything above 20KHz.
Explain compression and rarefaction.
When the transducer element vibrates, the wave emitted goes through a series of compression (condensing) and rarefaction (expanding) as it travels
Define wave.
A propagation of energy that moves back and forth or vibrates at a steady rate.
Diagnostic ultrasound uses short sound pulses at what frequency?
1 to 20 million cycles/second MHz
What is propagation velocity?
The speed of a sound wave moving through a medium.
What is the assumed average propagation velocity in soft tissue?
1540 m/sec or 1.54 mm/sec.
What determines how fast sound will travel through a structure?
stiffness or density of the medium
Which structure has a higher propagation velocity, water or bone, and why?
Bone because it is a denser medium. The denser the medium, the faster the sound will travel.
What is a decibel? (dB)
the unit used to measure the intensity (strength), amplitude, and power of an ultrasound wave.
What is amplitude?
the intensity (strength) of an ultrasound wave measured in decibels (dB)
Define power.
The rate at which energy is transmitted, measured in watts or milliwatts. Also refers to the strength of the transmitted ultrasound pulse from a transducer.
Define intensity.
power per unit area, measured in W/meter squared)
Power and intensity are related how?
They are directly related. If you double one, you double the other.
What is frequency?
The number of oscillations per second performed by the particles of the medium in which the wave is propagating.
What is acoustic impedance?
The measure of a material’s resistance to the propagation of sound.
What is attenuation?
The sum of acoustic energy losses resulting from absorption, scattering, and reflection. Think of a flashlight, concentrated light at the lens but not as concentrated in light as it casts outward.
What is an interface? What is a specular reflector?
An interface is the area where two different tissues come into contact with each other and have a difference in acoustic impedance. A specular reflector is a large smooth surface (interface)
What is refraction?
A change in the direction of sound that occurs when sound encounters an interface between two tissues that transmit sound at different speeds. (Broken appearing straw in a glass of water)
Define wavelength.
The distance over which a wave repeats itself during one period of oscillation.
Define absorption.
Loss of sound energy, secondary to its conversion to thermal energy.
What is piezoelectricity?
Physical pressure applied to a crystal results in the creation of electric potential.