Basic Principles of Ultrasound Physics and Artifacts Made Easy - POCUS 101 (2023)

As a Point of Care Ultrasound (POCUS) enthusiast, you may dread the term “Ultrasound Physics” and wished there was a simple way on how to learn and understand the principles of ultrasound physics that are actually relevant to your clinical practice.

But many of the resources on ultrasound physics that you encounter may seem too technical or don’t actually relate to the clinical use of Point of Care Ultrasound (POCUS).

I totally understand what you’re going through and have seen countless POCUS learners just gloss over ultrasound physics because it seems “boring” or “irrelevant”.

However, learning basic ultrasound physics is essential if you want to really improve or perfect your POCUS skills. Don’t worry, we are going to make Ultrasound Physics and Artifacts simple, easy, and clinically relevant!

In this post I will show you an easy way to use Ultrasound Physics to:

  1. Understand how Ultrasound Creates a Picture for you
  2. Always Pick the Correct Ultrasound Probe based on Frequency
  3. Easily Understand Ultrasound Velocity, Impedance, Reflection, Refraction, Attenuation
  4. Understand Ultrasound Terminology or “Echogenicity”
  5. Understand the Doppler Modes (Color, Power, Pulse wave, Continuous Wave, Tissue Doppler)
  6. Understand how important Ultrasound ARTIFACTS are Created (with full list/images of examples)

Though beginners or experienced Point of Care Ultrasound users will find this post helpful, just think of this post as an “Ultrasound Physics for Dummies” guide or reference.

I’ll cover the most important concepts on how to understand Ultrasound Physics principles and Artifacts. Alright, let’s start your journey towards mastering Sonographic Physics and Artifacts in the easiest and most practical way possible!

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Table of Contents

What is the Definition of Ultrasound?

The definition of “ultrasound” is simply the vibration of sound with a frequency that is above the threshold of what humans can hear. The frequency of ultrasound is by definition, any frequency greater than 20,000 Hz. However, ultrasound used in medical practice is typically 1,000,000 Hz (1 Megahertz) or greater.

So the next time you pick up an ultrasound probe or transducer just notice what “Frequency” the probe is. It will usually range (termed bandwidth) between 2 Megahertz to 10 Megahertz. For example, 2.5-3.5 MHz for general abdominal imaging and 5.0-10 MHz for superficial imaging.

How Ultrasound Creates a Picture – The Piezoelectric Effect

Next let’s go over how an ultrasound device uses ultrasonic waves to create pictures on the screen for you.

It traditionally does this by using an effect called the “Piezoelectric Effect.” This is simply the vibration of a piezoelectric crystal at the tip of the transducer that generates a specific ultrasonic frequency to create ultrasound waves. (FYI These crystals are easily broken and cost thousands of dollars to replace. Think about that each time you drop a probe. Yikes!)

These ultrasonic waves can then penetrate through the body’s soft tissue and return to the transducer as reflected ultrasound waves. These returning waves are then converted into an ultrasound image on the screen for you to view.

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Therefore, all ultrasound principles are based on the physics of “waves” and if you can understand some basic physics principles that pertain to waves, you can derive exactly how ultrasound images are formed, ultrasound artifacts are created, and even how to use more advanced ultrasound applications such as Doppler.

(Editor’s note: Many of the newer handheld ultrasound devices do not use the traditional piezoelectric effect to create ultrasound images, and instead use silicon chips. However, the concepts of waves still apply)

Ultrasound Physics Table

Here is an important ultrasound physics table you can reference that goes over the speed, density, acoustic impedance, and attenuation of ultrasound relative to specific tissue types. You’ve may recognize it from other resources but never understood how to use it.

Don’t attempt to memorize this table, just look at the trends. This will help you understand why certain tissues look brighter (echogenic) compared to others, why ultrasound waves get reflected/refracted, and how ultrasound artifacts are formed. We will go over the importance of the findings of this table throughout the post.

Tissue or MaterialSpeed of Sound (m/s)Acoustic Impedance (kg/[s m2]) × 10^6Density (g/cm3)Attenuation (dB/cm/MHz)
Air3300.00040.001212
Fat14501.380.950.63
Blood15751.661.0550.18
Liver15701.691.060.94
Bone40807.751.915

What Ultrasound Physics do you Actually Need to Know?

There are a few simple ultrasound physics principles that you will need to know in order for you to optimize your use of ultrasound and to understand ultrasound artifacts. I’ll also introduce some important ultrasound physics formulas and equations to help you grasp the concepts such as artifacts and Doppler (no need to memorize this stuff). Just invest a little time into learning these basic ultrasound physics concepts and it will help you tremendously.

Just think of Ultrasound in terms of “Waves”

An ultrasound device creates images, simply by sending short bursts of “waves” into the body. Understanding how these waves behave will be helpful in understanding how to optimize your ultrasound settings and images. I’ll make it as simple as possible for you and just go over the things I have found to be most relevant to be able to use the ultrasound machine.

Frequency and Wavelengths

Now I’m sure you’ve heard the word “Frequency” a lot when it comes to ultrasound transducers. Such as high versus low frequency ultrasound probes. But what exactly does that mean? Okay let’s get some definitions out of the way:

Wavelength = length or distance of a single cycle of a wave.

Frequency = the number of sound wave cycles per second.
The equation for Frequency = Speed of sound wave/Wavelength

(Video) Ultrasound Principles & Instrumentation - Orientation & Imaging Planes

So you can see from the equation, as wavelength increases, frequency decreases (and vice versa). This is because Frequency is inversely related to wavelength. The SHORTER the wavelength the HIGHER the frequency and the LONGER the wavelength the LOWER the frequency.

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This is why higher frequency ultrasound probes will give you better resolution compared to a lower frequency probe. A high-frequency ultrasound probe will emit shorter wavelengths, so tissues will receive more ultrasound “waves” per unit of time with a high-frequency probe. However, the trade-off with high-frequency probes is decreased penetration because the piezoelectric crystal can only send so many ultrasound waves out before the waves dissipate.

Here is a graph showing the relationship between the frequency of an ultrasound probe and the resolution versus penetration it is able to achieve.

  • Phased array probe: great penetration, okay resolution
  • Curvilinear probe: good penetration, good resolution
  • Linear probe: poor penetration, great resolution
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Speed of Sound In Different Mediums

Now the “speed of sound” is also often referred to with ultrasound. So why is the speed or velocity of sound so important?

Well, the exact speed of sound in specific tissue does not actually mean much to you clinically. However, the change in speed between two different mediums is extremely important. This is the essence of how ultrasound waves reflect and refract to create important ultrasound artifacts. So while you don’t need to know the exact speed of sound in certain tissue you do need to understand how the speed of sound changes between different mediums such as soft tissue, fluid, air, and bone.

The average speed/velocity of sound in all mediums is 1540 cm/s. However, depending on what medium the sound waves travel through, it can drastically change the propagation speed of sound as it passes through.

Two of the factors that affect the speed of sound are the stiffness and density of the material it is traveling through. The stiffer the medium, the faster the sound waves will travel and that is why sound waves travel faster in solids than in liquids or gases. So the ultrasound propagation speed from slowest to fastest is: Lung (air) << Fat < Soft tissue << Bone. This happens because stiffer mediums have tighter particles to propagate the ultrasound wave and therefore the velocity is greater.

Acoustic Impedance – Reflection and Refraction

Acoustic Impedance is the Resistance to Ultrasound Propagation as it Passes Through a Tissue

Acoustic Impedance is probably one of the most confusing terms when trying to learn ultrasound physics.

Acoustic Impedance (Z) is actually a physical property of a medium or tissue. It is dependent on the tissue density and the speed of sound through that tissue.

Impedance = Density x Propagation Speed of Sound Wave

So if the density of a tissue increases, the impedance (resistance) will increase as well. Refer to the ultrasound physics table again:

Tissue or MaterialSpeed of Sound (m/s)Acoustic Impedance (kg/[s m2]) × 10^6Density (g/cm3)Attenuation (dB/cm/MHz)
Air3300.00040.001212
Fat14501.380.950.63
Blood15751.661.0550.18
Liver15701.691.060.94
Bone40807.751.915

Reflection of Ultrasound Waves

The importance of Impedance in ultrasound becomes apparent at the interface of two tissue types with significantly different impedance values. Ultrasound waves will reflect when this situation occurs. The proportion of ultrasound waves reflected back is proportional to the difference in impedance (or density) of two tissue types

REFLECTION occurs with ultrasound waves when two adjacent tissues have Significantly Different Impedance Values.

This is why bone and air appear as bright lines on ultrasound and also why you get the reflected “A-Lines” with pulmonary ultrasound. There is such a large difference between impedance of tissue and bone/air that they will cause almost all of the ultrasound waves to reflect back instead of penetrating through. What is interesting is that the impedance values of Air (extremely low at 0.0004) and bone (very high at 12), both cause reflection because of its drastic difference from the impedance of soft tissue (approximately 1.6).

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We will go into more detail on the artifacts caused by reflection in the detailed Ultrasound Artifacts Section below but they include: reverberation artifact, mirror image artifact, comet tails, and ring down artifact.

Refraction of Ultrasound Waves

REFRACTION occurs with ultrasound waves when two adjacent tissues have Slightly Different Impedance Values.

So when ultrasound waves travel through tissue and meet another tissue with slightly different impedance values, the speed changes somewhat and cause the ultrasound waves to change in direction. This change in direction is called Refraction!

The degree of how much refraction occurs is dependent on what angle the ultrasound wave encounters the second medium and how much of a change in speed there is in the second medium. This is seen mostly in situations at the rounded interfaces between a fluid-filled circular structure and the adjacent soft tissue. This is what gives rise to the edge artifact seen in ultrasound with black lines arising from the edge of fluid-filled structures such as the gallbladder, cyst, vessels, and bladder.

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(Video) Introduction to Point of Care Ultrasound (POCUS) - Basics
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Attenuation – Absorption

ATTENUATION is the Loss and Absorption of Ultrasound Energy Through a Medium

Attenuation is a fairly easy concept to understand compared to impedance. It just describes how rapidly does a medium reduce the intensity of an ultrasound wave as it passes through it. The two mediums with the highest amounts of attenuation are actually AIR and BONE!

As you can see attenuation is not simply dependent on the density of the material like impedance is. Look at ultrasound physics table below to see the relationship between tissue density, impedance, and attenuation:

Tissue or MaterialSpeed of Sound (m/s)Acoustic Impedance (kg/[s m2]) × 10^6Density (g/cm3)Attenuation (dB/cm/MHz)
Air3300.00040.001212
Fat14501.380.950.63
Blood15751.661.0550.18
Liver15701.691.060.94
Bone40807.751.915

This is the reason that ultrasound waves can’t pass through air or bone. The ultrasound waves either get reflected back (impedance mismatch) or gets absorbed (high attenuation).

Attenuation will account for the “Shadowing” artifact seen in bone or gall stones.

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Basic Ultrasound Terminology: “Echogenicity”

So if you want to speak the “language” of ultrasound, you will need to refer to specific structures on an ultrasound image based on it’s “Echogenicity.”

“Echogenicity” refers to how bright (echogenic) a tissue appears on ultrasound relative to another tissue.

ANechoic (Black)

The term “Anechoic” on ultrasound means no internal echoes are emitted and there is a completely black appearance. This is most commonly seen with fluid-filled structures since ultrasound waves pass through fluid without reflecting any echoes back to the ultrasound machine.

Here is a list of structures that appear “Anechoic” or black on ultrasound: blood (unclotted), bladder, transudative pleural effusions, ascites, simple cysts, gallbladder.

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HYPERechoic (Bright/White)

The term “Hyperechoic” on ultrasound means that a specific structure gives off MORE echoes relative to it’s surrounding structures resulting in a brighter/whiter appearance. Below is an example of the pleural line which is “Hyperechoic” (bright/white) compared to the surrounding soft tissue.

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HYPOechoic (Darker/Grey)

The term “Hypoechoic” on ultrasound means that a specific structure gives off fewer echoes relative to it’s surrounding structures resulting in a darker or more grey appearance.

In the image below this patient has hepatitis with a Hypoechoic (darker) appearing liver compared to the right kidney:

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ISOechoic (Similar)

The term “Isoechoic” on ultrasound means that a specific structure gives off similar echoes relative to another structure on the ultrasound screen. For example, you may say the Renal Cortex is isoechoic to the Spleen Parenchyma like the image below:

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Ultrasound Doppler Made Easy

One of the most used modes with ultrasound is Doppler. Initially, Doppler may seem confusing with all of the different Doppler modes available to you (color Doppler, power Doppler, pulse wave Doppler, continuous wave Doppler, and tissue Doppler).

But if you just think of Doppler signals as detecting the speed of movement either Towards or Away from your probe you can derive all of the different Doppler ultrasound modes.

The Doppler Effect (or Doppler Shift) is used to evaluate movement either towards or away from the ultrasound probe/transducer. The most common Doppler ultrasound application we think of is detecting movement of blood, but we can also use Doppler on ultrasound to evaluate tissue and muscle movement.

Doppler Shift Equation:

Doppler Shift = (2 x Velocity of blood x transducer frequency x cos θ)/ Propagation speed

(Video) Basic Transthoracic Echocardiography (Cardiac Ultrasound) - TTE Made Simple

*θ = Angle of Insonation (angle of incidence between the ultrasound beam and the direction of flow)

So the Doppler shift is mainly related to TWO things:

  1. The Velocity of the blood cells
  2. The Angle of Insonation

Below is a figure detailing how the Doppler Shift is used and how the angle of insonation is extremely important in what the transducer will detect as the amount of flow/movement. For any type of Doppler you want the flow/movement to be going directly towards your probe (zero degrees) as you move more towards a 90 degree angle there will be no flow detected by the ultrasound machine.

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(Editor’s note: I’m using the velocity of blood as the example here. But the same principles apply if you are measuring muscle movement using tissue doppler. Check out the diastology post to learn more about tissue Doppler. )

So the most important thing you can do to improve your Doppler technique for any mode is to make sure that the movement of whatever you are measuring is parallel to your ultrasound probe as much as possible (zero degrees). Anything above 25-30 degrees will significantly underestimate your measurements. And if you are perpendicular, the cosine of 90 degrees = 0 and the ultrasound Doppler will read no flow or movement.

Color Doppler

The most common Doppler mode you will use is color Doppler. This mode allows you to see the movement of blood movement in arteries and veins with blue and red patterns on the ultrasound screen.

A common question that comes up with color Doppler is: What do the colors on ultrasound mean? The answer is: RED means there is flow TOWARDS the ultrasound probe and BLUE means that there is flow AWAY from the ultrasound probe. It is a misconception that red is arterial and blue is venous. It actually just depends on the direction blood is flowing relative to the angle of your ultrasound beam.

An easy way to remember this is to use the BART mnemonic: Blue AWAY, Red TOWARDS.

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There is a mode similar to color Doppler that you may encounter called Power Doppler. This mode does not show up as red or blue on the screen but only uses a single yellow color signifying the amplitude of flow. It is more sensitive than color Doppler and is used to detect low flow states such as venous flow in the thyroid or testicles.

The “Other Doppler Modes”

Now some learners may feel like the “other doppler modes” such as Pulse wave, Continuous wave, and Tissue Doppler are very advanced settings. However, the same principles of color Doppler apply to these other Doppler modes as well. The ultrasound probe is just detecting flow or motion either TOWARDS or AWAY from it. If it is towards the probe there will be a positive deflection and if it is away from the probe there will be a negative deflection.

Here is an illustration that sums up the those Doppler modes:

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Going through each of these Doppler modes is beyond the scope of this post. However, if you want a good explanation of exactly how Pulse Wave Doppler and Tissue Doppler are used, check out the diastolic dysfunction post HERE.

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Essential Ultrasound Artifacts

Ultrasound artifacts are frequently encountered and can be a source of confusion for interpreting providers. Ultrasound artifacts can be understood with a basic understanding of the ultrasound physics we just discussed pertaining to reflection, refraction, and attenuation.

The ability to recognize and fix correctable ultrasound artifacts is important for getting quality ultrasound images and optimizing the care of your patients.

Here are the main ultrasound artifacts we will cover:

  • Mirror Image Artifact
  • Acoustic Shadowing Artifact
  • Posterior Acoustic Enhancement
  • Edge Shadowing Artifact
  • Reverberation Artifact
  • Comet Tail Artifact
  • Ring Down Artifact
  • Side Lobe Artifact

Mirror Image Artifact

The mirror image artifact on ultrasound occurs when ultrasound waves encounter a highly reflective surface that is adjacent to air.

The most common instance of this is the pleural-diaphragm interface causing the appearance of “liver” or “spleen” inside the lung. You can also see mirror image artifact when you are performing cardiac ultrasound as the ultrasound waves, approach the pleural-pericardium interface. These are normal findings.

Acoustic Shadowing Artifact

Acoustic shadowing occurs when ultrasound waves encounter a structure that has a high attenuation coefficient.

You will most commonly encounter the acoustic shadowing artifacts in the following structures: bones, ribs, and gallstones.

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(Video) Wall Filter, Steering, and Angle Correction - Advanced Ultrasound Doppler Settings made Easy
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Posterior Acoustic Enhancement

This is the opposite of the acoustic shadowing artifact and occurs when ultrasound waves pass through a structure with significantly low attenuation such as blood or fluid-filled structures.

The most common situation you will see posterior acoustic enhancement: bladder, gallbladder, cysts, vessels, ocular ultrasound.

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Edge Shadowing Artifact

Edge artifact on ultrasound occurs because of refraction. Ultrasound waves are deflected from their original path when they encounter curved and smooth-walled structures. This will result in a shadow-like line that comes off of the edge of these structures. The most common times you will see this are: vessel walls, gallbladder, cystic structures, testicle, aorta.

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Reverberation Artifact

In the presence of highly reflective surfaces, echoes may reflect back and forth between the reflective surface and the ultrasound probe. This can cause the ultrasound screen to record and display multiple echoes on the screen. This ultrasound artifact is known as Reverberation Artifact.

Let’s use the highly reflective pleural line as an example below. The ultrasound waves that return after a single reflection represents the actual pleural line (white arrows/line in the figure below). All of the subsequent echoes (blue, green, and red arrows/lines) will take longer to return the probe and the ultrasound will interpret those as increased equidistantly spaced linear reflections. These other lines are also known as “A-lines” and are a form of reverberation artifact in normal lung.

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Comet Tail Artifact

Comet tail artifact is a form of reverberation artifact. In comet tail artifact the two reflective surfaces are closely spaced together (such as the bevel of a metallic needle). The reflective surfaces are so close that it is difficult to distinguish between each reflected echo.

Comet tail artifact is different from ring down artifact (described next) because the comet tail artifact dissipates with depth and has a triangular and tapered shape. See the image below of a comet tail artifact arising from a needle tip.

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Ring Down Artifact

Previously, the ring down artifact was thought to be a type of comet tail artifact, since both have bright “echogenic” lines arising from a specific location. However, the ring down artifact has a distinct feature compared to the comet tail artifact in that the echos do NOT dissipate as the depth of the image is increased. These echogenic vertical lines will go all the way to the bottom of the screen, regardless of depth. This has become known as the “ring down artifact” and is most commonly seen as “B-lines” in lung ultrasound, signifying interstitial edema.

The theory for the ring down artifact is that when fluid is trapped in a tetrahedron of air bubbles, the ultrasound waves reflect infinitely and result in an infinitely long vertical echogenic line.

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Side lobe Artifact

Side lobe artifact occurs when the beam of an off-axis side lobe encounters a structure and returns this off-axis object as coming from the main beam. This creates a duplicate structure on the screen but in a different area.

In the example below, it seems like there is a moving structure in the left atrium, but it is actually a side lobe artifact resulting from the mitral valve leaflet. This is important because oftentimes these side lobe artifacts may be mistaken for clots or foreign bodies. It is always a good habit to get multiple views to confirm that what you are seeing is artifact versus pathology.

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Best Ultrasound Physics Book Reference – Sidney K. Edelman PhD

I hope you found this ultrasound physics post helpful and clinically relevant. Of course, I could not cover every detail of ultrasound physics in one post, but if you went through this post you will have all the ultrasound physics basics to help your scanning.

However, if you want to learn more about ultrasound physics, I would recommend checking out this book by Sidney K. Edelman PhD. It will go over all of the ultrasound physics you could ever want but in a very reader-friendly way. It’s definitely a staple on my ultrasound bookshelf!

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References

  1. Understanding Ultrasound Physics book by Sidney K. Edelman PhD
  2. Steel, R., Poepping, T., Thompson, R., Macaskill, C. (2004). Origins of the edge shadowing artefact in medical ultrasound imaging Ultrasound in Medicine & Biology 30(9), 1153-1162. https://dx.doi.org/10.1016/j.ultrasmedbio.2004.07.014
  3. Feldman, M., Katyal, S., Blackwood, M. (2009). US artifacts. Radiographics : a review publication of the Radiological Society of North America, Inc 29(4), 1179 – 1189. https://dx.doi.org/10.1148/rg.294085199

(Special thanks to Kimberly Ayers RDCS for reviewing this post)

(Video) Module 1: Fundamentals of Point of Care Ultrasound (POCUS)

FAQs

What are the types of artifacts in ultrasound? ›

Artifacts
  • acoustic enhancement.
  • acoustic shadowing.
  • aliasing artifact.
  • anisotropy.
  • bayonet artifact.
  • beam width artifact.
  • blooming artifact.
  • color bruit artifact.
8 Jul 2022

What is the physics behind the ultrasound? ›

Ultrasound waves can be generated by material with a piezoelectric effect. The piezoelectric effect is a phenomenon exhibited by the generation of an electric charge in response to a mechanical force (squeeze or stretch) applied on certain materials.

Why is Knobology important? ›

Knobology is a terminology that describes the manipulation of ultrasound knobs and system controls in order to obtain the best image possible from diagnostic ultrasound. The inadequate use of knobology variables may impair image quality and can result in misdiagnosis.

What is B mode in ultrasound? ›

B-mode: In B-mode ultrasound, a linear array of transducers simultaneously scans a plane through the body that can be viewed as a two-dimensional image on screen.

What causes artifacts in ultrasound? ›

Artifacts in ultrasonographic diagnostics are a result of the physical properties of the ultrasound waves and are caused by interaction of the ultrasound waves with biological structures and tissues and with foreign bodies. On the one hand, they may be distracting and may lead to misdiagnosis.

What does artifacts mean in ultrasound? ›

Artifacts are any alterations in the image which do not represent an actual image of the examined area. They may be produced by technical imaging errors or result from the complex interaction of the ultrasound with biological tissues. REVERBERATION. Reverberation artifacts appear as a series of equally spaced lines.

Why is physics important in ultrasound? ›

It is a highly user-dependant interaction among the sonographer, patient, and machine. An understanding of the physics of ultrasound is important because it helps explain some of the limitations of the modality and artifacts encountered.

What is F number in ultrasound? ›

The f-number equals the depth of the returning echo divided by the aperture of the beam. (the aperture of the beam is the width of the number of simultaneous firing transducer elements in the array, that means the larger the aperture the more elements are fired simultaneously).

Why do you need physics for ultrasound? ›

A basic knowledge of ultrasound physics and instrumentation is vital to ensure the correct application of ultrasound for both diagnostic and therapeutic interventions.

What are the 3 most basic components of the ultrasound machine? ›

Any ultrasound system has three basic components: a transducer, or probe; the processing unit, including the controls; and the display.

What is M mode? ›

Background: M-mode or "motion" mode is a form of ultrasound imaging that is of high clinical utility in the emergency department. It can be used in a variety of situations to evaluate motion and timing, and can document tissue movement in a still image when the recording of a video clip is not feasible.

What determines depth in ultrasound? ›

Depth Penetration

It depends on transducer frequency, transmission power, and Tissue Harmonic Imaging (THI). Several aspects should be considered when determining depth penetration.

What are 4 uses of ultrasound? ›

Ultrasound is used for many reasons, including to:
  • View the uterus and ovaries during pregnancy and monitor the developing baby's health.
  • Diagnose gallbladder disease.
  • Evaluate blood flow.
  • Guide a needle for biopsy or tumor treatment.
  • Examine a breast lump.
  • Check the thyroid gland.
  • Find genital and prostate problems.
30 Apr 2022

What is PW and CW in ultrasound? ›

CW Doppler measures all blood flow velocities along the cursor line. This is in contrast to PW Doppler which measures flow at a specific point within the heart using a sample volume box. Thus CW can measure multiple different blood flows within different cardiac chambers throughout the cardiac cycle.

How do ultrasounds reduce artifacts? ›

You can reduce the effects of the artifact by decreasing the transducer's frequency, decreasing depth, and choosing an anatomic structure with a velocity below the Nyquist limit. This is accomplished by using a low-frequency probe and examining the structure from a window that's located close to the probe.

What is an artifact in physics? ›

In natural science and signal processing, an artifact or artefact is any error in the perception or representation of any information introduced by the involved equipment or technique(s).

How do ultrasound artifacts affect ultrasound image? ›

In ultrasound, artifacts are echoes that appear on the image but do not have a true correspondence to an anatomical structure. An artifact may cause the anatomical structure to be missing from the image. It also shows structures as present but incorrect in location, size, or brightness [1].

How do you avoid mirror image artifacts? ›

To avoid this artifact, change the position and angle of scanning to change the angel of insonation of the primary ultrasound beam.

Why is it important for a sonographer to be able to identify imaging artifacts? ›

Recognition of artifacts is important, as they may be clues to tissue composition and aid in diagnosis. The ability to recognize and correct potential ultrasound artifacts is important for image-quality improvement and optimal patient care.

What causes enhancement artifact? ›

Enhancement results from low attenuation objects in the sound path while shadowing results from strongly reflecting or strongly attenuating objects. Additional artifacts include section thickness, refraction, multipath, side lobe, grating lobe, focal enhancement, comet tail, ring down, speed error, and range ambiguity.

What waves do ultrasounds use? ›

Description. Ultrasound imaging (sonography) uses high-frequency sound waves to view inside the body. Because ultrasound images are captured in real-time, they can also show movement of the body's internal organs as well as blood flowing through the blood vessels.

What is Snell's law in ultrasound? ›

Snell's law Application in Ultrasonic Testing - YouTube

How ultrasound image is formed? ›

An ultrasound uses high-frequency sound waves to produce detailed images of internal organs. Unlike X-rays, ultrasound scanning does not involve radiation, which means that it has no known side effects and is very safe.

What is attenuation in ultrasound? ›

The amplitude and intensity of ultrasound waves decrease as they travel through tissue, a phenomenon known as attenuation. Given a fixed propagation distance, attenuation affects high frequency ultrasound waves to a greater degree than lower frequency waves.

What is aperture size in ultrasound? ›

Aperture size and wavelength: The aperture is the active area that transmits or receives acoustic wave at certain moment. For a single-element transducer, the aperture size is the transducer element size. For array transducer, the aperture are all the elements that works together simultaneously.

What is the maximum applied voltage of an ultrasound transducer? ›

In addition to high current, piezo ultrasonic transducers require high voltage. Their required voltage is usually greater than 10V and up to 100V or higher.

Why is fluid black on ultrasound? ›

On sonography imaging liquids appear black because they are “anechoic”. It means that the ultrasound wave goes through them without emitting any return echo .

Is ultrasound a pressure wave? ›

An ultrasound is a type of oscillating sound pressure wave that has a higher frequency than human hearing is able to detect. An ultrasound is not a unique type of sound, therefore, but is classified differently due to the fact that humans cannot hear it.

What is the frequency range of ultrasound? ›

Sounds with a frequency of 20 kHz and higher are referred to as ultrasound (or ultrasonic sound). High frequency sound is sound of which the frequency lies between 8 and 20 kHz.

Why is gel used in ultrasound? ›

Ultrasound gel is used as a coupling medium in all ultrasound procedures to replace air between the transducer and the patient's skin, as ultrasound waves have trouble in traveling through air.

What are the characteristics of ultrasound? ›

10 Important Properties of Ultrasonic Waves
  • Property 1: Ultrasonic waves vibrate at a frequency greater than the audible range for humans (20 kilohertz).
  • Property 2: They have smaller wavelengths. ...
  • Property 3: They cannot travel through vacuum.
  • Property 4: Ultrasonic waves travel at the speed of sound in the medium.

What is Doppler mode? ›

Doppler mode: This is the presentation of the Doppler spectrum (continuous wave or pulsed wave). Color Doppler (mode): A 2D Doppler image of blood flow is color coded to show the direction of flow to and away from the transducer (see Figure 10.8A).

What is Colour Doppler test? ›

Sheps, M.D. A Doppler ultrasound is a noninvasive test that can be used to estimate the blood flow through your blood vessels by bouncing high-frequency sound waves (ultrasound) off circulating red blood cells. A regular ultrasound uses sound waves to produce images, but can't show blood flow.

How many types of ultrasound machines are there? ›

6 Common Types of Ultrasound and How They Are Used.

What color is air on ultrasound? ›

Because there is poor transmission of sound waves from body tissues through air (they are reflected back to the transducer), bowel filled with air appears on ultrasound as a bright (white) area.

What is a focal zone? ›

Focal Zone: The narrowest part of the ultrasound beam profile when it is emitted from the transducer. In this region, the pulse waves are concentrated resulting increased beam intensity (energy/area).

How far can ultrasound penetrate? ›

Ultrasound Depths in Modality Texts

Starkey33 stated that 1-MHz ultrasound can affect tissues up to 5 cm deep, and 3-MHz ultrasound is effective on tissues up to 2 cm deep.

What are the 3 types of ultrasounds? ›

Types of Ultrasound
  • Endoscopic ultrasound.
  • Doppler ultrasound.
  • Color Doppler.
  • Duplex ultrasound.
  • Triplex ultrasound (color-flow imaging)
  • Transvaginal ultrasound.

What is the difference between ultrasound and ultrasonic? ›

ultrasound, also called ultrasonography, in medicine, the use of high-frequency sound (ultrasonic) waves to produce images of structures within the human body. Ultrasonic waves are sound waves that are above the range of sound audible to humans.

What ultrasound can detect? ›

Ultrasound can help providers diagnose a wide range of medical issues, including:
  • Abnormal growths, such as tumors or cancer.
  • Blood clots.
  • Enlarged spleen.
  • Ectopic pregnancy (when a fertilized egg implants outside of your uterus).
  • Gallstones.
  • Aortic aneurysm.
  • Kidney or bladder stones.
12 Apr 2022

Who invented ultrasound? ›

Besides, ultrasound was the brainchild of engineer Tom Brown and Obstetrician Ian Donald. They were the first people who crafted the prototype system. They created it centered on an instrument that served the purpose of detecting the flaws in the industrial ships. However, in the 1970s, it became widely used.

Who can hear ultrasonic sound? ›

Among the following animals dogs, cats and bats can hear ultrasonic sounds.

What are five uses of ultrasound? ›

Ultrasound can also be done much faster than CT and MRI scans and has the advantage of having no radiation.
  • Ultrasound to Monitor your baby. Measuring the size of the fetus to determine the due date. ...
  • Breast Ultrasound to detect cancer. ...
  • Testicular Ultrasound to detect cancer. ...
  • Muscle and joint pain. ...
  • Abdominal pain.
10 May 2020

What is Nyquist limit in ultrasound? ›

The Nyquist limit represents the maximum Doppler shift frequency that can be correctly measured without resulting in aliasing in color or pulsed wave ultrasound.

What is PRF in ultrasound? ›

PRF is the Doppler sampling frequency of the transducer and is reported in kilo Hertz (KHz). The frequency with which these pulses are emitted determines the maximum Doppler shifts obtainable. The maximum Doppler shift frequency that can be sampled without aliasing is PRF/2, called the Nyquist limit [14].

Why is Nyquist limit half PRF? ›

Nyquist's theorem and Nyquist limit

Recall that the Doppler shift is directly related to the velocity of blood flow; the greater the velocity, the greater the Doppler shift. Thus, the maximum velocity that can be determined is half the PRF and this limit is called the Nyquist limit.

What are artifacts in radiology? ›

An artifact on an image is a feature that does not correlate with the physical properties of the subject being imaged and may confound or obscure interpretation of that image. In this article, examples of artifacts from flat-panel detector–based digital radiographic systems are presented.

What are two artifacts associated with refraction? ›

  • windmill artifact.
  • cone beam effect.
  • MPR artifact. zebra artifact. stair-step artifact.
2 Aug 2021

What is side lobe artifact in ultrasound? ›

Side lobe artifacts occur where side lobes reflect sound from a strong reflector that is outside of the central beam, and where the echoes are displayed as if they originated from within the central beam.

What is ring down artifact? ›

"Ring-down" is an ultrasound artifact that appears as a solid streak or a series of parallel bands radiating away from abdominal gas collections.

What is an example of an artifact? ›

Vase Being Excavated

An artifact is an object made by a human being. Artifacts include art, tools, and clothing made by people of any time and place. The term can also be used to refer to the remains of an object, such as a shard of broken pottery or glassware.

What causes image artifacts? ›

An image artifact is sometime the result of improper operation of the imager, and other times a consequence of natural processes or properties of the human body. It is important to be familiar with the appearance of artifacts because artifacts can obscure, and be mistaken for, pathology.

How do ultrasounds reduce artifacts? ›

You can reduce the effects of the artifact by decreasing the transducer's frequency, decreasing depth, and choosing an anatomic structure with a velocity below the Nyquist limit. This is accomplished by using a low-frequency probe and examining the structure from a window that's located close to the probe.

What is an artifact in physics? ›

In natural science and signal processing, an artifact or artefact is any error in the perception or representation of any information introduced by the involved equipment or technique(s).

What impact can artifacts have on ultrasound images? ›

In ultrasound, artifacts are echoes that appear on the image but do not have a true correspondence to an anatomical structure. An artifact may cause the anatomical structure to be missing from the image. It also shows structures as present but incorrect in location, size, or brightness [1].

What is speed error in ultrasound? ›

Speed displacement artifact, also known as propagation velocity artifact, is a gray scale ultrasound finding that can be identified as an area of focal discontinuity and displacement of an echo deeper than that its actual position in an imaged structure.

What is shadowing in ultrasound? ›

An acoustic shadow is an ultrasound artifact occurring at boundaries between significantly different tissue impedances, resulting in signal loss and a dark appearance. Shadow detection is important as shadows can identify anatomical features or obscure regions of interest.

What is slice thickness artifact? ›

1.3 Slice Thickness Artifact. This is similar to the beam width artifact but occurs due to the thickness of the beam which is 90° to the scan plane (Feldman et al. 2009 ). The slice of transducer will receive echoes from either side of the intended slice and will be included in the displayed image.

What causes twinkle artifact? ›

CONCLUSION. The appearance of the twinkling artifact is highly dependent on ma- chine settings and is likely generated by a narrow-band, intrinsic machine noise called phase (or clock) jitter. Surface roughness secondarily broadens the noise spectrum.

What is speckle artifact? ›

Speckle artifact may be encountered in ultrasound. It is caused by the scattering of waves from the surface of small structures within a certain tissue. The artifact produces a textured appearance.

What causes reverberation in ultrasound? ›

A: Reverberation artifact occurs when an ultrasound pulse gets "trapped" between two strong parallel reflectors. The wave reflects back and forth between the reflectors ("reverberates"). The waves that return to the transducer are interpreted as deeper structures since they arrive to the transducer at a later time.

Videos

1. How to use Any Ultrasound Machine - Knobology and Physics - Made Super Simple
(POCUS 101)
2. Basic PoCUS 1: Essential Physics & Knobology in Ultrasonography
(Emergency & Trauma Hospital Kuala Lumpur)
3. Basic Applications : Female Pelvis - Scanning Techniques
(westernsono)
4. POCUS - Thoracic/Lung Basic Ultrasound and Anatomy
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5. Vascular Doppler using Ultrasound Made Simple
(POCUS 101)
6. Ultrasound 101 Part 5 Terminology and Tissues.mp4
(Petra Lewis)
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