UTZ Finals Reviewer

What are ultrasound waves defined as?

Mechanical waves with frequencies greater than 20,000 Hz (20 kHz).

What type of waves have motion perpendicular to the direction of travel?

Transverse waves.

What is the frequency range that the human ear can detect?

20 Hz to 20 kHz.

What are longitudinal waves characterized by?

Motion parallel to the direction of wave travel, composed of compressions and rarefactions.

What is the definition of frequency in the context of sound waves?

The number of vibrations (cycles of motion) a particle of medium makes per second.

What does elasticity refer to in ultrasound physics?

The ability of an object to return to its original shape and volume after a force is removed.

What is the significance of density in sound propagation?

Higher density materials allow for greater sound velocity.

What is compressibility in the context of ultrasound?

A measure of how much a material's volume increases under pressure.

What is the principle of superposition in wave theory?

The summation of waves to form more complex waves.

What does Huygen's principle explain?

All points on a wave can act as source points for the production of spherical waves.

What was the first successful echocardiogram performed with?

An echo test control device from a Siemens shipyard in 1953.

Who was the first to study echolocation among bats?

Lazzaro Spallanzani in 1794.

What year did Karl Dussik use sonography for medical diagnoses?

1942.

What was the first ultrasound device invented for detecting objects underwater?

A hydrophone, invented by Paul Langevin in 1915.

What technology did Don Baker and his team develop in 1966?

Pulsed Doppler ultrasound technology for imaging blood flow.

What advancements in ultrasound technology occurred in the 1980s?

Development of 3D ultrasound technology and improved imaging capabilities.

What is the piezoelectric effect?

The phenomenon where certain materials become electrically polarized when subjected to pressure.

Name a synthetic material used in ultrasound transducers.

Lead zirconate titanate (PZT).

What is the bulk modulus in relation to sound propagation?

A measure of a material's resistance to compression, inversely related to compressibility.

What is the role of acoustic variables in sound waves?

They describe the properties of sound waves, including amplitude, frequency, and wavelength.

What is the visualization of longitudinal waves often compared to?

A slinky being pushed back and forth.

What is the significance of the year 1989 in ultrasound history?

Professor Daniel Lichtenstein began incorporating lung ultrasound into medical practice.

What is the main application of ultrasound in the medical field?

Diagnostic imaging, including OB/GYN applications and echocardiograms.

What does the term 'destructive interference' refer to?

When two waves cancel each other out, resulting in a zero amplitude.

What is the relationship between sound velocity and medium density?

Higher density typically results in higher sound velocity.

What is the significance of the 1990s for ultrasound technology?

Introduction of sophisticated capabilities like endoscopic ultrasound and 4D imaging.

Who developed 3D ultrasound technology that captured fetal images?

Kazunori Baba in the 1980s.

What is the function of piezoelectric crystals in ultrasound?

They convert electrical energy into mechanical energy (sound) for transmission and mechanical energy (sound) into electrical energy for reception.

Name two types of piezoelectric materials.

Quartz (natural) and Lead zirconate titanate (PZT) (man-made ceramics).

What happens to beam divergence as the diameter of the crystal decreases?

Beam divergence increases.

What is acoustic impedance?

The product of density and velocity of ultrasound in a material, used to determine the amount of ultrasound reflected at an interface.

What are the units of acoustic impedance?

Rayls or kg/m²/s.

How does the packing of particles affect acoustic impedance?

A substance with densely packed particles has high acoustic impedance, while one with loosely packed particles has low acoustic impedance.

What is the average velocity of ultrasonic waves in soft tissue?

1540 meters per second.

What is the effect of acoustic impedance mismatch on ultrasound reflection?

Greater impedance mismatch results in a greater percentage of energy reflected at the interface.

Why is ultrasound not practical for imaging subjects containing gas or bone?

Large acoustic impedance mismatches lead to strong echoes and minimal energy transmission, preventing effective imaging.

What effect does increasing frequency have on ultrasound beam divergence?

It results in longer near field and shorter far field divergence.

What is the relationship between crystal thickness and frequency?

Thin crystals correspond to high frequency, while thick crystals correspond to low frequency.

Define near field in ultrasound.

The region where the ultrasound beam is more focused, also known as the Fresnel zone.

Define far field in ultrasound.

The region where the ultrasound beam diverges, also known as the Fraunhofer zone.

What are side lobes in ultrasound?

Energy radiating from the transducer at various angles, which can cause artifacts.

What is beam width?

The dimension of the beam in the scan plane through which the beam is sweeping.

How does beam width affect spatial resolution?

Narrower beam width generally leads to better spatial resolution, allowing for the distinction of smaller structures.

What is the formula for acoustic impedance in MegaRayls?

Acoustic Impedance = (Pressure Amplitude) x (Density) x 10^6.

What does the decibel (dB) measure in ultrasound?

It expresses relative intensity, comparing the intensity at a point of interest to a reference intensity.

What is the average intensity range of ultrasonic waves in diagnostic ultrasound?

0.1 - 10 mW/cm².

What is the relationship between intensity and pressure amplitude?

Intensity is proportional to the square of the pressure amplitude.

What is the purpose of a transducer in ultrasound?

To convert electrical energy into sound energy and vice versa.

What components are included in the physical housing of a transducer?

Crystals, electrodes, matching layer, and backing materials.

What is the frequency range for ultrasound transducers?

2 MHz to 20 MHz.

What is intensity attenuation in ultrasound?

The decrease in intensity of the ultrasound beam as it travels through a medium.

What artifacts can arise from side lobes and grating lobes?

They can cause considerable artifacts due to 3D misregistration and degradation of lateral resolution.

What is the primary function of the physical housing in an ultrasound transducer?

To provide structural support and act as an electrical and acoustic insulator.

What effect do piezoelectric elements have in transducers?

They operate on the piezoelectric effect, generating voltages when subjected to mechanical force.

What is the purpose of backing materials in ultrasound transducers?

To shorten the ultrasound pulse length, improving axial resolution.

How does frequency affect ultrasound resolution?

Higher frequency results in shorter wavelength, increased resolution, and reduced penetration; lower frequency has longer wavelength, decreased resolution, and better penetration.

What is the role of the impedance matching layer in ultrasound transducers?

To minimize reflection at the boundary between the piezoelectric crystal and the patient, allowing more acoustic energy to be transmitted.

What is the function of an acoustic lens in ultrasound imaging?

To improve image resolution by reducing the beam width of the transducer.

What materials are commonly used for backing/damping materials in transducers?

Tungsten powder mixed with plastic or epoxy resin, cork, rubber, and Araldite.

What are the three types of electronic array transducers?

Linear Array, Curvilinear Array, and Phased Array Transducers.

What is spatial resolution in ultrasound imaging?

The ability to display two structures situated close together as separate images.

What is axial resolution in ultrasound imaging?

Resolution along the axis of the beam, highly dependent on spatial pulse length.

What is the best way to achieve optimal axial resolution?

By using a higher frequency transducer and minimizing spatial pulse length.

What is contrast resolution in ultrasound imaging?

The ability to differentiate between body tissues and display them as different shades of gray.

What is temporal resolution in ultrasound imaging?

The ability to display events occurring at different times as separate images.

What does hyperechoic mean in ultrasound terminology?

More echogenic than surrounding tissue.

What does hypoechoic mean in ultrasound terminology?

Less echogenic than surrounding tissue.

What does anechoic mean in ultrasound terminology?

Devoid of echoes.

What is the attenuation coefficient?

A parameter used to differentiate the attenuation properties of various media, expressed in dB per cm per MHz.

What happens to the ultrasound beam as it travels through the body?

It loses energy due to attenuation.

What is the significance of beam width in lateral resolution?

A narrow beam width provides better spatial resolution.

What is the relationship between frequency and lateral resolution?

Higher frequency leads to better lateral resolution.

What is the main application of curvilinear array transducers?

Abdominal and obstetric scanning.

What type of transducer is best suited for cardiac ultrasound?

Phased Array Transducers.

What is the effect of using thinner piezoelectric materials?

They produce higher resonant frequencies.

What is the difference in acoustic impedance between PZT and soft tissue?

It is large, about greater than 15 times, leading to significant reflection without an impedance matching layer.

What is the best resolution achievable in axial resolution?

Half the spatial pulse length.

What does lateral resolution depend on?

The beam width; a narrow beam width gives better lateral resolution.

What is the purpose of focusing the ultrasound beam?

To improve spatial resolution at the area of interest.

What is attenuation in ultrasound?

The loss of energy of the ultrasound beam as it travels through the body, resulting in decreased intensity and amplitude.

What is the main factor causing attenuation of the ultrasound beam?

Absorption.

How does frequency affect ultrasound absorption?

Higher frequency results in greater absorption.

What are the three factors affecting the amount of absorption in ultrasound?

Viscosity, relaxation time, and frequency.

What is the relationship between frequency and attenuation coefficient?

They are directly proportional; as frequency increases, the attenuation coefficient increases.

What is scattering in ultrasound?

When an ultrasound wave strikes a boundary or small structures, causing the wave to scatter in different directions.

What is refraction in ultrasound?

The deviation of the ultrasound beam when it encounters an interface between two tissues with different speeds of sound at an oblique angle.

What is reflection in ultrasound?

Occurs when ultrasound waves encounter a large structure with significantly different acoustic impedance, causing some wave energy to reflect back to the transducer.

What is divergence in ultrasound?

The spreading of the ultrasound beam as it travels through tissue due to diffraction effects.

What is an ultrasound artifact?

A structure in an image that does not directly correlate with the actual tissue being scanned.

What is reverberation artifact?

Production of false echoes due to repeated reflections between two interfaces with a high acoustic impedance mismatch.

What does acoustic shadowing indicate?

An area of low amplitude echoes behind strongly attenuating tissue, caused by severe attenuation of the beam.

What is acoustic enhancement artifact?

A localized area of increased echo amplitude behind an area of low attenuation.

What causes edge shadowing artifact?

Occurs at the edges of rounded structures when the speed of sound is different from that in surrounding tissue.

What is beam width artifact?

Occurs when echoes from across the full width of the beam return to the transducer, which can vary by several millimeters.

What is slice thickness artifact?

Occurs due to the thickness of the ultrasound beam, similar to beam width artifacts.

What is side lobe artifact?

Occurs when sound reflects from a strong reflector outside of the central beam, creating a false image.

What causes double image artifact?

Caused by refraction of the ultrasound beam, resulting in a duplicate image.

What are equipment-generated artifacts?

Artifacts that appear due to incorrect use of ultrasound equipment controls.

What is a mirror image artifact?

A type of propagation artifact where a structure is duplicated on the opposite side of a strong reflector.

What is B-mode display in ultrasound?

Brightness mode, a 2D imaging mode that displays the amplitude of echoes.