7 Factors for comparison when buying Ultrasound machine

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Ultrasound machines are one of the most widely used imaging modalities in medicine today. Since they use sound waves instead of X-radiation, they are considered to be safer than many of the other diagnostic radiology modalities. Sonography machines have advantages over other imaging modalities on account of excellent visualization and real-time imaging capabilities, non-invasive nature, proven clinical efficacy, easy access, easier management and a relatively low cost say as compared to CT/MRI. Hence ultrasound machines have become common, not only in traditional settings like cardiology, general imaging, and obstetrics/gynecology, but also in emerging specialties such as emergency departments, anesthesia and intensive care units. When one is looking to buy an ultrasound machine on a tight budget it is very important to cut-out the frills and pay for only what is necessary. What are the important features for ultrasound machine comparison?

The following are some important questions to consider when buying an ultrasound machine:

1. What is the intended use or application of the ultrasound machine?
2. What probes/ transducers are required?
3. What features & software are required? How good is the image quality?
4. Do you need a portable ultrasound machine?
5. Other general parameters like
   1. What are the dimensions and weight of the machine?
   2. Is battery back-up available? For what duration?
   3. What is the image storage capacity, Printing, data transfer and connectivity capabilities?
6. What is the cost of after sales Support?
7. What is your budget?

Looking for a ready template listing most important features to compare? Scroll to the end of the blog. For details of these 7 factors read on…

What Are the Diagnostic or Screening Uses intended?

Ultrasound machines are used for diagnostic imaging in Obstetrics, Gynecology, Cardiology, Vascular studies, Abdominal studies, Anesthesia, Breast, neck, skin and other small parts.

• Obstetrics: Ultrasound machines are used during pregnancy to assess the progress of a fetus. It is used to find out information like the number of fetuses in the womb, the age of the fetus, the location of the placenta, the fetal position, movement, breathing and heart rates and the amount of amniotic fluid in the uterus. Doppler ultrasounds may also be used to measure blood flow and may be used if there is a suspicion that the fetus is not growing properly.
• Gynecology: Apart from pregnancy related imaging, ultrasound machines are extensively used for other women’s health related issues. Vaginal/pelvic or transvaginal ultrasound is done to diagnose growths or tumors of the ovary, uterus and fallopian tubes. It can be used to assess non-pregnancy related issues such as lower abdominal pain, ovarian cysts, uterine fibroids, uterine growths, endometriosis etc.
• Cardiology: Echocardiography is commonly done to evaluate the overall functioning of the heart. It is used to evaluate the flow of blood through the chambers and valves of the heart, assesses the strength of the heart beat and the volume of blood pumped through. Doppler ultrasound echocardiography is often used for detecting heart valve problems, such as mitral valve prolapse or aortic stenosis; congestive heart failure; blood clots due to irregular heartbeats such as in atrial fibrillation; abnormal fluid collections around the heart, such as pericardial effusions and pulmonary artery hypertension.
• Blood vessels: Ultrasound is useful in detecting problems with most of the larger blood vessels in the body. Using Doppler ultrasound technology, the flow of blood through the vessels can be observed and measured. Narrowing of vessels (stenosis) or widening of vessels (dilatation, also referred to as aneurysms) can be detected. Ultrasound testing of blood vessels includes carotid ultrasound, abdominal aorta ultrasound for abdominal aortic aneurysm and blood clots in veins (superficial or deep venous thrombosis – DVT).
• Abdominal structures: Most common use of ultrasound machine is in inspecting the organs within the abdominal cavity, including the liver, gallbladder, pancreas, kidneys, and bladder.
• Ultrasound is used to diagnose testicular torsion, epididymitis (testicle infection), and testicular masses, detect thyroid and parathyroid glands nodules, growths, and tumors, image the breasts and to guide biopsy of breast masses in order to evaluate for breast cancer and also to help find certain types of foreign bodies that may become lodged in the skin. Ultrasound machine is now globally used in anesthesiology as a diagnostic tool as well as for carrying out procedures. It is the standard of care for peripheral nerve blocks and central vascular access.

First thing when buying an ultrasound, you must know how you intend to use the ultrasound machine. The use case depends on type of patients you are treating or the type of cases you are referring away to others if you do not have the right diagnostic equipment.

It may be great to have one machine which does everything, but either no such machine exists or it will be too expensive. That’s because not all ultrasounds are built alike every machine is built with a specific use in mind and has its own strengths and weaknesses. That is why identifying your specific use is critical. Are you using the ultrasound for cardiology, vascular, OB/GYN, urology, anesthesia or something else? Your answer will help you make the right decision.

Now it may sound simple. After all, the sonologist who is going to use the machine should know, right? However very often in a multi-specialty hospital the initial purchase related work is done by the bio-medical or purchase department or sometimes a physician colleague, who is not entirely clear about the overall case mix of the hospital and hence what sort of use the ultrasound machine is intended for. Therefore it is better to sit down with a checklist and document requirements and decisions and carry out an extensive ultrasound machine comparison.

What probes/ transducers are required?

The probes required are directly dependent on the type of cases you are going to be doing. A transducer or probe is a key part of ultrasound imaging. There are ultrasound transducers in different shapes, sizes and with diverse features for effective imaging of different body parts. Probes can be either passed over the surface of the body externally or can be inserted into an orifice, such as the rectum or vagina so as to get a closer look. The ultrasound transducers differ in design depending on their piezoelectric crystal arrangement, aperture (footprint) & frequency at which they work.

There are mainly four basic types of probes used:

1. Linear probes – are generally high frequency better for imaging superficial structures & vessels also called vascular probes. Linear transducers, for example, are used for things like vascular examinations, Breast, Thyroid, orthopedics, small parts and measuring body fat.
2. Convex or Curvilinear probes – have widened footprint and lower frequency for transabdominal imaging & widen the field of view. Convex transducers are suitable for diagnosis of organs and abdominal examinations especially in urology, obstetrics & gynecology. Micro convex probes have much smaller footprint and typically used for neonatal and paediatrics applications.

3. Phase array probes – Phased Array Transducer has a small footprint and low frequency. Phased Array transducers are used for getting between ribs such as cardiac ultrasound, including Transesophageal examinations, abdominal examinations, Brain examinations etc.
4. Endocavitary probes – E.g. Transesophageal (TEE), transvaginal & transrectal probes are have a small footprint and are inserted through the related body orifices to examine organs more closely.

3D & 4D ultrasound probes help in more detailed imaging in terms of volume data acquisition, volume display & analysis and multi-planar imaging of organs. In other words, assessing multiple 2-D image planes simultaneously. 3D imaging allows fetal structures and internal anatomy to be visualized as static 3D images. However, 4D ultrasound allows us to add live streaming video of the images, showing the motion of the fetal heart wall or valves, or blood flow in various vessels. It can be seen as 3D ultrasound in live motion. Sophisticated software is used to harness the 2D data collected and create 3D and 4D presentations.

For most of the clinical diagnostic requirements however, 2D probes and images suffice.

E.g in case of OB/GYN specialty, a 2D Convex and an endo-cavity probe are sufficient to examine foetus during pregnancy, ovary, uterus, fallopian tubes and other organs for gynecological purposes. However, some nursing homes may want to share a 3D picture showing a more recognizable face of the baby or even a 4D moving video image to please expecting parents. So even though it adds no value clinically speaking one may have to spend more for the 3D/4D ultrasound machine.

On the other hand using software for automated Intima-Media thickness measurement may prove to be highly useful due to significant improvement in diagnosis accuracy for Carotid atherosclerosis. What features and software are worth spending more money on? That is the next question we should be considering.

What are the features and software required?

Once the intended use or application is identified, then identifying specific features important to the care and expected standards follows. There are many features and software that could enhance diagnosis ability such as 3D/4D, Doppler studies, Auto IMT for vascular, which helps automatically measure the intima, Speckle reduction imaging or advanced speckle reduction imaging, spatial compound imaging, elastography etc.

A 2D-mode is the default mode. It is a 2 dimensional cross sectional view of the structures/ organs being imaged and is made up of many B-mode scan lines. This mode is sufficient to assess all organs and structures including measurement of cardiac chamber dimensions, valvular structures etc. However it does not resolve rapid movements well. Hence, if you need to be detecting rapid movements of the underlying organs, you need M-mode which is very good at temporal resolution. The M-mode is commonly used for measuring chamber dimensions and calculating fractional shortening and ejection fraction etc. Similarly colour Doppler is used for detecting velocity and direction of blood flows. For better endocardial definition, better resolution even at greater depths and reduced near field clutter in echocardiography tissue harmonic imaging is used.

Real-time spatial compound imaging shows improved image quality compared with conventional ultrasound, primarily because of reduction of speckle, clutter, and other acoustic artifacts. Real-time spatial compound imaging can provide improved contrast resolution and tissue differentiation that is beneficial for imaging the breast, peripheral blood vessels, and musculoskeletal injuries.

Elastography gives an idea whether the tissue is hard or soft in turn indicating presence or status of disease. For e.g cancerous tissues would be harder than normal tissues. Elastography is not only non-invasive but also particularly advantageous in cases like where fibrosis is diffused so that a biopsy can easily miss sampling the diseased tissue. This may result in a false negative misdiagnosis.

The software installed on the machine can change its capabilities, which is why this is the most important item to consider in ultrasound machine comparison. Some applications can improve image quality significantly and others include analytical tools that can help providers identify patterns within an image, improving accuracy of diagnosis. There’s a wide range of applications available, many of them really nice to have, but they need to be weighed against actual need, depending on the type of cases you are mostly expecting to see and diagnose.

Do you need a portable ultrasound machine?

At this point, you have identified how you are going to use the ultrasound machine, the probes you need, and the features you need. Now is the time to decide if a portable machine, as opposed to a stationary console, is the right choice. Portability is an important feature for ultrasound machine comparison.

In a multi-specialty hospital it needs to be clear if the machine is going to be moved around often between ICU, OT and OPD or even for camps. If so, you need a portable machine, as stationary console based sonography machine would be too cumbersome to move around and may get damaged. However, one must be aware that convenience of mobility comes at the cost of limited features, image quality, probe options and form-factor (smaller keyboard and display etc.)

While choosing a portable ultrasound, we have to be aware of the limitations and disadvantages. A portable ultrasound will:

• not have the same image quality and probe options as a console ultrasound
• have limited software features and options as compared to a console ultrasound
• have small keyboard and monitor like a laptop
• Could have similar footprint as a console ultrasound due to use of a cart to move it around.

How good is the After Sales Support?

If you are purchasing new ultrasound machine make sure you negotiate the price including 2-3 years of warranty. If in case you are considering used/ refurbished ultrasound machine, you need to not only check availability of after sales service support, but also track record of the refurbisher/seller in the market & spares availability with them. This goes beyond ultrasound machine comparison on features per se.

What is your budget?

The pricing of ultrasound machines vary widely starting from basic all-purpose models to high-end sophisticated machines. Decision really needs to be made depending on the most important needs vs the budget you have.

General Parameters for ultrasound machine comparison

Other important parameters to consider are things like:

• Dimensions and weight of the machine – Even if the machine is not going to be moved around, you need to see if the machine is going to occupy too much space.
• If you are worried about uninterrupted power supply, battery back-up and duration is a parameter to be checked out. This is especially pertinent in case of portable machines.
• Image storage capacity and ease of transfer, ports available, DICOM compatibility and perhaps even integration with electronic medical records or other hospital information systems would be important considerations.
• There are many other parameters such integrated gel warmer, printer, zoom other peripheral devices connectivity etc. depending on your preferences and needs that need to be listed and checked before buying.

Click to download Ultrasound machine comparison template

 

Properly performing Point of Care Ultrasound involves understanding the ultrasound knobs, machine, and equipment. But you may have issues finding a resource that allows you to easily learn how to understand and use the ultrasound machine.

In this post, I will go over the most common Ultrasound Knobology (knobs/buttons), Probes, Modes, Movements, Orientations, and Planes you will need to properly scan. By learning these ultrasound basics, you will be able to have the fundamentals on how to use any ultrasound machine you may encounter!

This post mainly goes over ultrasound machine settings, probes, buttons, and functions. I also created another post on a simple way of learning Ultrasound Physics and Artifacts you can access by clicking HERE.

Choosing the Right Ultrasound Probe (Transducer)

Choosing the Right Ultrasound Probe based on Application

The single most important factor that will determine if you can get proper ultrasound images is choosing the correct ultrasound probe or transducer. Like with anything else you do, the right tool will be needed for the right situations. For example, if you used a linear probe, that has great resolution but minimal depth, you will not be able to visualize much if any of the heart.

So before you start scanning, always ask yourself these questions to help pick your ultrasound probe:

• What application am I using the ultrasound machine for?
• How deep are the structures I’m trying to visualize?
• How big or small of a footprint do I need?
• Does it involve a procedure?
• Does it involve a cavity (pelvic, peritonsillar abscess)

In this post we will go over the 4 most common Point of Care Ultrasound probes you will encounter (linear, curvilinear, phased array, and endocavitary probes). The table below lists when you should think about using each type of ultrasound probe.

Each ultrasound probe will have it’s pros and cons. Usually, the most important factors to decide on are resolution, penetration, and footprint size. Here is a figure showing how penetration and resolution are affected with respect to the frequency of the transducer.

The Ultrasound Probe “Footprint” refers to the area on the probe that comes in contact with the patient’s skin in order to produce an ultrasound image. It is located at the very tip of the probe and is usually has a soft “rubbery” feel. Depending on the application you may want a smaller or larger footprint. Regarding footprint width from largest to smallest it goes: Curvilinear > Linear > Phased Array.

The images below demonstrate the relative sizes and footprints of the 3 most commonly used ultrasound probes (Linear, Curvilinear, and Phased Array):

Most Common Ultrasound Probes Side by SideDifferent Size Footprints of Ultrasound Probes

Linear Ultrasound Probe

The linear ultrasound probe is a high-frequency transducer (5-15 MHz) that will give you the best resolution out of all of the probes but is only able to see superficial structures. A general rule of thumb is that if you are going to ultrasound anything less than about 8cm, then use the linear probe. Anything above 8cm you won’t be able to see much.

The linear probe will give you a rectangular field of view that corresponds with its linear footprint:

Linear Ultrasound Probe

Curvilinear Ultrasound Probe

The curvilinear ultrasound probe has a frequency range of 2-5MHz. It is considered a low-frequency probe and has a large/wide footprint, allowing for better lateral resolution (compared to the phased array probe). The curvilinear ultrasound probe is often used for abdominal and pelvic ultrasound exams. However, it can also be used for cardiac and thoracic ultrasound exams but is limited by the large footprint and difficulty with scanning between rib spaces.

Here is what the Curvilinear probe looks like and how an ultrasound image will appear on the screen. Notice the curved nature of the ultrasound image.

Curvilinear Ultrasound Probe

Phased Array (Sector) Ultrasound Probe

The phased array (or sector array) transducer is commonly branded as the “cardiac probe” and has a frequency range from 1-5MHz. It has a similar frequency range as the curvilinear probe but has a smaller and flat footprint.

The advantage of this probe is that piezoelectric crystals are layered and packed in the center of the probe making it easier to get in-between small spaces such as the ribs (notice the extremely small pinpoint footprint on the ultrasound image below).

It is the ideal probe for cardiac scanning however it can perform all of the applications the curvilinear probe can as well (with less lateral resolution).

Phased Array Ultrasound Probe

Endocavitary Ultrasound Probe

The endocavitary probe has a curvilinear footprint with a wide view but has a much higher frequency (8-13 MHz) than a curvilinear ultrasound probe. The image resolution of the endocavitary probe is exceptional, but like the linear probe, it must be adjacent to the structure of interest since it has such a high frequency/resolution, but poor penetration.

The most common POCUS applications for the endocavitary ultrasound probe are for intraoral (peritonsillar abscess) and transvaginal applications (early pregnancy, ovarian torsion, ovarian cyst, fibroids, ectopic pregnancy, etc). Make sure to always place a sterile endocavitary probe cover (condom or glove) prior to scanning.

Endocavitary ProbeEndocavitary Probe – Pelvic Ultrasound

The All-in One Handheld Ultrasound Probes:

The ultrasound probes just described are for the traditional cart-based systems.

However, there are now handheld devices that connect to your smartphone and can simulate multiple probe types with just a click of the button. The Butterfly Ultrasound Device is an example of this (see below). From my experience, the footprint is slightly larger than the phased array and the weight of the probe is about 2-3 times more than a typical phased array. This increased weight is accounted for by the processor and the battery.

Ultrasound Probes Side by Side with Butterfly Handheld

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Ultrasound Probe Movements and Manipulation

Handling the ultrasound probe and proper movement is essential to obtaining optimal ultrasound images. There are traditionally 4 basic movements that are performed when scanning with ultrasound they are Slide, Rock, Tilt(Fan), Rotate. Another technique that could be considered a “5th” cardinal movement is Compression.

The 4 Cardinal Ultrasound Movements (Adapted from Ramsingh 2018)

Here is a quick 45 second video we made for you that shows all of the essential ultrasound movements:

It is very important that you master each of these ultrasound transducer manipulation/movement techniques. Most experienced sonographers think what manipulation or combination of movements will give them the desired image. In their minds, they know how each transducer manipulation should change their image. With deliberate practice, you will be able to do this too!

POCUS 101 Tip: For learners, really trying to improve, I always suggest that when you see a suboptimal image, think to yourself what is the next best transducer manipulation you can perform to get an optimal image. Too often, learners try a random combination of transducer movements without thinking first what the image should look like prior to manipulating the transducer.

SLIDING

The Ultrasound Probe

Sliding involves moving the entire probe in a specific direction to find a better imaging window. This is usually used to find the best window, move to different areas of the body, or to follow a specific structure (such as a vessel).

Ultrasound Movement – SlidingUltrasound Movement – Sliding (Illustration)

(Editors Note: There is some more recent literature that suggests that the term “sliding” should indicate motion along the long axis of the probe and “sweeping” involves motion along the short axis of the probe. However, I have found this confuses learners more than just the general term sliding to encompass any movement of the probe from the original position. Also sometimes when you are sliding you are not just going along the short or long axis of the probe but a combination. However, I wanted to mention this distinction in case you encounter it)

TILTING (FANNING)

the Ultrasound Probe

Tilting the ultrasound probe involves moving the transducer from side to side along the short axis of the probe. It is commonly also called “Fanning” as well. Tilting will allow visualization of multiple cross-sectional images of a structure of interest. You can apply this technique to structures such as the heart, kidney, bladder, vessels, etc.

Ultrasound Movement – Tilting/FanningUltrasound Movement – Tilting/Fanning (Illustration

ROTATING

the Ultrasound Probe

Rotating the ultrasound probe involves turning the transducer in a clockwise or counterclockwise direction along its central axis. Rotation is most commonly used to switch between the long and short axis of a specific structure such as a vessel, the heart, the kidney, etc.

In the example below, we are going from a short axis to the long axis of the brachial artery by rotating clockwise 90 degrees:

Ultrasound Movement – RotatingUltrasound Movement – Rotating

ROCKING

the Ultrasound Probe

Rocking the ultrasound probe involves “rocking” the ultrasound probe either towards or away from the probe indicator along the long-axis.

Rocking allows you to help center the area of interest. This is also referred to as “in-plane” motion because the image is kept in-plane throughout the manipulation.

Here is an example of rocking the ultrasound probe:

Ultrasound Movement – RockingUltrasound Movement – Rocking

COMPRESSION

with the Ultrasound Probe

Compression with the ultrasound probe involves putting downward pressure on the probe to evaluate the compressibility of a structure or organ of interest. The most common use is to evaluate for deep vein thrombosis, differentiate between artery versus vein, and evaluation for appendicitis (non-compressible).

Here is an example of compression used to compress the brachial artery and vein:

Ultrasound Movement – Compression

Indicator (Orientation Marker) Position

Ultrasound

PROBE

Indicator (Orientation Marker) Position

The “probe indicator” on the ultrasound probe can be identified as an orientation marker (ridge, indentation, groove, or nub) on one side of the probe. This corresponds to the indicator or orientation marker on the ultrasound image.

Indicator Orientation Marker on Ultrasound Probe

Ultrasound

IMAGE

Indicator (Orientation Marker) Position

In general, for almost all standard applications and procedures the indicator orientation marker position will be on the LEFT side of the screen. In cardiac mode, the indicator orientation marker will be on the RIGHT side of the screen.

Indicator Orientation Marker – StandardIndicator Orientation Marker – Cardiac

Ultrasound Imaging Planes/Orientation

Radiographically, the body is divided into three distinct planes: Sagittal, Coronal, and Transverse. Any combination of those movements is considered “Oblique.”

Ultrasound Imaging Planes (Wikimedia)

Sagittal Plane

Parallel to the long axis of the body and separates the body from left to right.

Transverse Plane

Perpendicular to the long axis of the body and separates body from top (superior) to bottom (inferior).

Coronal Plane

Parallel to the long axis of the body and separates the body from front (anterior) to back (posterior).

Oblique Plane

Oblique imaging planes refer any plane that uses a combination of those planes.

Short Axis and Long Axis Orientation:

Cylindrical and non-circular structures can additionally be described using the terms Short vs Long axis.

Long Axis: plane parallel to the maximal length of a structure.

Short Axis: plane perpendicular to the long-axis of a structure.

These views can be obtained by rotating 90 degrees relative to each other. These terms are helpful in structures such as vascular and cardiac applications. Also, this is useful when deciding to perform a procedure in a short versus long-axis approach.

Below we are rotating between a short-axis and long-axis of the brachial artery using a clockwise rotation of 90 degrees.

Going from Short to Long Axis of Artery

Here is an example of the long axis and short axis of the heart. The parasternal short axis is obtained by rotating 90 degrees clockwise from the parasternal long axis view.

Parasternal

LONG

axis of heartParasternal

SHORT

axis of heart

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Ultrasound Knobology and Settings: Step-by-Step Approach

Starting to use an ultrasound machine can feel really intimidating since they seem to have so many knobs and buttons!

The good news is that all ultrasound machines have the same basic settings and once you understand them you can start using any ultrasound device with ease.

I would suggest approaching any ultrasound machine in with the following order using the step-by-step approach below. I’ve found doing it in this order prevents you from forgetting to optimize basic ultrasound settings that can drastically improve your image quality.

Knobology Step 1

:

Power Button

Yes the most important button of all is the power button! Simple enough!

This is an interesting fact: the on and off buttons were derived from a binary numbering system where “0” was for OFF and “1” was for ON. So to create the universal symbol for Power the “0” and “1” were combined to make the following symbol:

Universal On/Off Power Button Symbol

This power symbol applies to almost all ultrasound devices as well. Just look for it when you want to turn on your machine.

Ultrasound Power Button

Knobology Step 2:

Switch to the Correct Ultrasound Probe/Transducer

If you read the beginning of this post, you should already know what ultrasound probe you need to use based on the application you are performing. So after turning on the ultrasound machine, the next most important step is to switch to the correct ultrasound transducer you will need.

This seems like common sense but I’ve seen many learners just want to jump in and start scanning with the wrong transducer. Unfortunately, understanding all of the ultrasound knobs won’t mean much if you have the wrong ultrasound probe to start off with!

Every machine will have a way to for you to switch between transducers.

Ultrasound Probe Switch Buttons

(Editor’s note: for the Butterfly. You don’t actually have to switch between transducers because it is an “all-in-one” device. When you switch the application preset it will automatically simulate the correct transducer settings for you)

Knobology Step 3:

Application Preset

After switching to the correct ultrasound probe, the next step is to select the correct application preset for that transducer.

Each transducer will have a different list of application presets based on its frequency and footprint. The ultrasound device companies will create application presets that make sense for those specific probes.

Think of selecting the ultrasound application preset like how you would select the correct preset for your point and shoot camera. You would use a different setting for day mode versus light mode. The camera will help adjust the settings to optimize for those specific conditions.

Selecting the correct application preset is similar in that it will automatically select the ideal frequency, depth, and gain for that application (i.e. cardiac vs abdominal). This gives you a great starting point to further fine-tune your image with the other knobs/buttons (depth, gain, focus, TGC, etc). In addition, the ultrasound will always start in B-mode or “greyscale” mode by default.

Ultrasound Preset Buttons

Knobology Step 4:

Depth

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Now the application preset will usually give you a decent image right when you place the ultrasound probe on the patient. However, there are some ultrasound settings that may need to be adjusted to optimize your ultrasound settings further.

The first of these ultrasound settings you should adjust is the depth. The ultrasound depth setting is simply how deep you want the ultrasound machine to be able to scan.

The rule of thumb is to only use as much depth that is necessary to see your structure of interest. Often times for beginning users, their depth will be too high and there is a lot of wasted “Ultrasound Real Estate” on the bottom of the screen.

The right side of the screen will have dots or lines that correspond to the depth in centimeters. This can give you an estimation of how deep your structures are as well. As you INCREASE the depth setting on your machine, you will see the numbers increase on the right side of the screen to correspond to the depth of penetration.

Ultrasound Depth Marker (4cm in this example)

Here is an example of increasing the ultrasound depth to visualize a deeper structure:

Increasing Ultrasound Depth

Conversely, if you decrease the depth you will be visualizing more superficial structures. Here is an example below of decreasing depth:

Decreasing Ultrasound Depth

Knobology Step 5:

Gain (Overall)

After optimizing your depth, the next ultrasound setting you should adjust is your gain.

Ultrasound gain simply means how bright or dark you want your image to appear. It increases or decreases the strength of the returning ultrasound signals that you visualize on the screen.

Ultrasound Overall Gain Button

All ultrasound machines will have an “Overall” Gain setting that, when increased or decreased, will make the entire ultrasound image brighter or darker. This is good to use when your entire imaged is too dark (under-gained) or too bright (over-gained).

Undergained Ultrasound ImageOvergained Ultrasound ImageOptimal Gain Ultrasound Image

(Editor’s note: Regarding this section, we are referring to Gain in the setting of B-mode/greyscale. You can also change the gain in your Doppler modes which we will discuss in the following section on “Advanced Modes.” Lastly, some machines have an “Autogain” button that I rarely use because I find it typically undergains your image.)

Knobology Step 6:

Near/Far Field Gain and Time Gain Compensation (TGC)

Most ultrasound machines will have settings that allow you to fine-tune and adjust the gain at specific depths of your greyscale ultrasound image. These will be termed Near/Far field gain or Time Gain Compensation (TGC).

Near Field and Far Field Gain (Sonosite)

The commonly used Sonosite M-Turbo or Edge machines allow you to adjust the “Near field” and “Far field” gain of your ultrasound images. The near field refers to the top half of the ultrasound screen and the far field refers to the bottom half of the ultrasound screen. The overall gain is just called “Gain” and is on the bottom left-hand corner of the Sonosite machine buttons.

Near and Far-field Gain – Sonosite

Time Gain Compensation (TGC)

Most other ultrasound machines will allow you to further adjust the gain in even more specific areas of your ultrasound screen. This ultrasound setting is called “Time Gain Compensation” or TGC.

Adjusting the Time Gain Compensation (TGC) allows you to adjust the gain at almost any depth of your ultrasound image, not just the near and far-fields. The top rows of the Time Gain Compensation control the nearfield gain and the bottom rows control the far-field gain.

Time Gain Compensation (TGC)

Here is an example of decreasing the TGC of the middle of the image with a corresponding absence of echoes on the middle of the ultrasound screen.

Decrease TGC in Middle of Ultrasound Image

Knobology Step 7:

Focus

The last ultrasound setting you can use to optimize your image is by adjusting the focus. When you adjust your focus you are simply concentrating your ultrasound waves at a specific depth of the image to maximize the resolution at that depth.

Some machines like the Sonosite don’t allow adjusting the focus since the machine has auto-focus built in.

However, if a machine does allow you to adjust the focus, it is very important to place the focus cursor to the depth of the area of interest. Usually, the focus is indicated by a small arrow (or hourglass) superimposed on the depth markings.

Ultrasound Focus Depth

Knobology Step 8:

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If you went through the previous steps then you should have a really good and optimized image. Here are just some other buttons you may encounter that may be useful if you need to freeze, measure, or capture your ultrasound image.

Freeze

Just like the world implies, the “freeze” button freezes a frame for you so you have time to view it in more detail. The ultrasound machine will usually store a 10-30 seconds of data and you can scroll back to see previous frames as well.

Calipers (measure)

Calipers are an important feature of ultrasound machines that allows you to measure the distance of specific structures of interest.

Image/Video Capture

All ultrasound machines will allow you to save an image and/or video clip of your ultrasound scan. This is important if you are trying to archive, bill, or use any ultrasound images/videos as teaching files.

Video example of Freeze, Measure, Image Capture:

Below is a quick video demonstrating how to use all of these functions (freeze, measure, image capture) by measuring the LVOT (left ventricular outflow tract) diameter. You can use this same technique to measure any other structure of interest.

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Basic Ultrasound Modes (B-Mode and M-Mode)

Now it may seem daunting when thinking about all of the available ultrasound modes available. In this section, the most common and basic ultrasound modes: B-mode and M-mode. In the following section, I will cover the more advanced Doppler Modes.

I would suggest that if you are just starting out, focus on B-mode (greyscale), and get really good at obtaining high-quality 2D images. After you feel comfortable with B-mode start adding on and learning the other more advanced Doppler modes. You can always come back to this post as a reference when you are ready to use the other modes!

Basic Ultrasound Modes – B and M-Mode

B-Mode (Brightness Mode) or 2D mode

B-Mode (Brightness Mode) in ultrasound is a setting that creates a two-dimensional (2D) greyscale image on your ultrasound screen and is the most commonly used mode. It is also commonly called 2D mode.

B-mode is the single most important mode you need to master in order to be proficient at point of care ultrasound (POCUS). All of the other modes rely on you getting a good B-mode (2D) image. Fortunately, we already discussed the most common ultrasound settings for B-mode in the ultrasound Knobology section above.

The buttons to get you back to B-mode/2D can be:

• B (just the letter) – GE machines
• 2D (Sonosite and Philips)

POCUS 101 Tip: Sometimes, you may be in a different mode or ultrasound machine setting and may wonder how to just reset your settings. Usually pushing the B-mode or 2D button on the ultrasound machine will reset everything and bring you back to the simple B-mode setting.

M-Mode (Motion Mode)

Ultrasound M-mode is defined as a motion versus time display of the B-mode ultrasound image along a chosen line. The motion is represented by the Y-axis and time is represented by the X-axis. Common applications for M-mode include looking at E point septal separation in cardiac scanning or calculating fetal heart rate for obstetrics. You can also use M-mode in lung ultrasound to evaluate for lung sliding and rule out pneumothorax.

Below is an example of how the M-mode (left side of screen) and B-mode (right side of screen) compare when looking at lung sliding. M-mode simply takes a “slice” of your B-mode image where the cursor line is placed and translates that “slice” over time. It ignores everything else on the B-mode scan except for where you have that cursor line. You can see on the Y-axis how the structures (subcutaneous tissue, muscle, and pleural line) correlate between the M-mode and B-mode images. You can also see the relative motion of these structures over time (X-axis).

Here are the steps to acquiring an M-mode Image:

• M-mode Step 1: Acquire 2D image and Center Structure of Image
• M-mode Step 2: Push the M-mode button to make the M-mode cursor line appear
• M-mode Step 3: Place the M-mode cursor line along the structure of interest
• M-mode Step 4: Push the M-mode button again to activate M-mode
• M-mode Step 5: Push the Freeze Button
• M-mode Step 6: Scroll to the desired image
• M-mode Step 7: Push the Measure Button
• M-mode Step 8: Measure Area of Interest

Here is also a video of performing the 8 steps of M-mode to measure Cardiac E-point Septal Separation (EPSS):

Here is another example of how to use M-mode to look for lung sliding and pneumothorax on ultrasound:

Advanced Ultrasound Modes (Doppler)

Besides B-mode and M-mode you will have other advanced ultrasound Modes that involve “Doppler.” Here is an image of all the available ultrasound modes:

All Ultrasound Modes

Initially, these Doppler modes may seem confusing but in reality, all Doppler settings are simply meant to detect speed going either Towards or Away from your probe (check out our previous post on Doppler Physics HERE). Understanding this is the first step to mastering ultrasound Doppler.

Doppler Shift Equation

All Doppler signals (regardless of which Doppler mode you are using) are calculated using the Doppler Shift Equation. 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 speed 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.

Doppler Shift Equation

(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.

So the most important thing you can do to improve your technique for any Doppler mode is to make sure that the movement/speed 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 Mode

The most common Doppler mode you will use is color Doppler. This mode allows you to see the movement of blood 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.

Ultrasound Color Doppler Principles using BART (Blue Away, Red Towards)

Color Doppler Steps:

• Color Doppler Step 1: Activate Color Doppler
• Color Doppler Step 2: Adjust Color Doppler Area
• Color Doppler Step 3: Adjust Color Doppler Scale
• Color Doppler Step 4:Adjust Color Doppler Gain

Color Doppler Steps

Here is a video demonstrating all of these steps for Color Doppler:

Power Doppler Mode

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. So you can’t tell if the flow is going towards or away from the probe given that it has only one color. It is more sensitive than color Doppler and is used to detect low flow states such as venous flow in the thyroid or testicles.

Ultrasound Power Doppler Setting

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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 flow/motion 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:

Pulse Wave (PW) Doppler Mode

Pulse Wave (PW) Doppler allows you to measure the velocity of blood flow (at a single point). A unique aspect of Pulse Wave Doppler is that you can specify to the ultrasound machine exactly where you would like the machine to measure the velocity using the Sample Gate. It’s usually seen by two horizontal lines along your cursor. you can move your cursor and your sample gate and place it exactly where you want to measure your blood velocity.

See the example figures below:

The biggest limitation with Pulse Wave Doppler, however, is that there is a limit on the maximum speed you can detect. Anything past this limit (termed Nyquist Limit) will cause the signal to alias. In general, you do not want to use Pulse Wave Doppler for any applications that require measuring speed above 200cm/second.

This is why you can’t use this mode for very high-velocity applications such as severe regurgitation or stenosis of the heart valves. Here is an example of aliasing with pulse wave Doppler:

Ultrasound Aliasing with Pulse Wave

Common applications of pulse wave Dopplers are to measure cardiac output (LVOT VTI) or diastolic dysfunction.

Here are the steps to properly use Pulse Wave Doppler after you acquire your 2D image:

• PW Doppler Step 1: Push Pulse Wave Doppler Button to make PW Cursor line appear
• PW Doppler Step 2: Place PW Sample Gate at Area of Interest
• PW Doppler Step 3: Push PW button again to activate Pulse Wave Doppler Mode
• PW Doppler Step 4: Adjust the PW Gain, Baseline, and Scale
• PW Doppler Step 7: Adjust the Sweep Speed (how many seconds are shown on the X-axis, see video below for example)
• PW Doppler Step 8: Push the Freeze Button
• PW Doppler Step 9: Scroll to the desired image
• PW Doppler Step 10: Push Measure Button
• PW Doppler Step 11: Measure Area of Interest

Here is a video demonstrating all of these Pulse Wave Doppler steps to calculate the Velocity Time Integral of the left ventricular outflow tract:

Also here is a video on how to use pulse wave doppler to measure diastolic dysfunction:

Continuous Wave (CW) Doppler Mode

Continuous Wave Doppler is very similar to pulse wave Doppler except it does not alias and can detect very high velocities (greater than 1000cm/second). So Continuous Wave Doppler is the optimal choice for measuring high-velocity applications such as valvular stenosis and regurgitation.

Unlike Pulse Wave Doppler which has a sampling gate to measure a single point along your cursor, Continuous Wave Doppler measures all points along your cursor. Therefore what you will see will be the maximum velocity of flow detected along the cursor line. This is a pro and a con. It is a pro because you don’t have aliasing and can detect high velocities, but it is a con because you don’t know exactly where that velocity is coming from on the cursor. Also if there are two velocities along the cursor line, you won’t be able to differentiate the lower velocity compared to the higher velocity signal, since the high-velocity signal will mask the low-velocity one.

The steps to performing continuous wave Doppler are the similar to Pulse wave Doppler except where you put the sample gate does not matter. It will measure velocities across the entire cursor line.

Steps to performing Continuous Wave Doppler:

• CW Doppler Step 1: Push Continuous Wave Doppler Button to make CW Cursor line appear
• CW Doppler Step 2: Place CW Cursor at Area of Interest (where you put the sample gate doesn’t matter)
• CW Doppler Step 3: Push CW button again to activate Continuous Wave Doppler Mode
• CW Doppler Step 4: Adjust the CW Gain, Baseline, and Scale
• CW Doppler Step 7: Adjust the Sweep Speed (if needed)
• CW Doppler Step 8: Push the Freeze Button
• CW Doppler Step 9: Scroll to the desired image
• CW Doppler Step 10: Push Measure Button
• CW Doppler Step 11: Measure Area of Interest

Here is an example of measuring tricuspid regurgitation (TR) using continuous wave Doppler. Notice how CW Doppler can measure the high velocity of this TR jet (344cm/s).

Tricuspid Regurgitation – Continuous Wave Doppler

Tissue Doppler Imaging (TDI) Mode

Now let’s go over how to use Tissue Doppler.

The good news is that all of the principles of Pulse Wave Doppler also apply to Tissue Doppler. In fact, Tissue Doppler is just another form of Pulse Wave Doppler that allows you to measure the much slower speeds of tissue/muscle movement (from 1cm/s – 20cm/s) compared to Pulse Wave Doppler that measures the much faster speed of blood (30cm/s – 200cm/s).

Accessing the Tissue Doppler function will vary by machine but usually just involves pushing a knob/button labeled “TDI” (Tissue Doppler Imaging) while you are in the Pulse Wave Doppler mode.

Here are the steps to using Tissue Doppler Imaging:

• TDI Doppler Step 1: Push Pulse Wave Doppler Button
• TDI Doppler Step 2: Place Sample Gate at Area of Interest
• TDI Doppler Step 3: Push TDI button to activate TDI Mode
• TDI Doppler Step 4: Adjust the TDI Gain, Baseline, and Scale
• TDI Doppler Step 5: Adjust the TDI Scale (if needed)
• TDI Doppler Step 6: Adjust the Sweep Speed
• TDI Doppler Step 7: Push the Freeze Button
• TDI Doppler Step 8: Scroll to the Desired Image
• TDI Doppler Step 9: Push Measure Button
• TDI Doppler Step 10: Measure Area of Interest

Here is a Step-by-Step video on how to use Tissue Doppler by measuring the medial e’ to evaluate diastolic function:

Other Ultrasound Doppler Settings: Wall Filter, Steer, Angle Correction

When you are in one of these Doppler settings, you will be able to optimize your image further by adjusting the following ultrasound buttons/knobs:

1. Wall Filter: decreases low-velocity signals. Used to minimize the amount of artifacts on your Doppler images

2. Steer: allows you to steer the color Doppler box when you can’t get an optimal angle
3. Angle Correction: used for Pulse wave to correct the angle of your sample gate when you can’t get an optimal angle

This video explains how to use all three of these ultrasound settings:

Ultrasound Knobology Summary

I hope you found this post helpful! Here is a Video summarizing the most commonly used ultrasound knobs, probes, and modes:

References

1. AIUM technical bulletin. Transducer manipulation. American Institute of Ultrasound in Medicine. Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine 1999
2. Bahner, D., Blickendorf, J., Bockbrader, M., Adkins, E., Vira, A., Boulger, C., Panchal, A. (2016). Language of Transducer Manipulation Journal of Ultrasound in Medicine 35(1), 183 – 188. https://dx.doi.org/10.7863/ultra.15.02036
3. Ransingh. Teaching Point-of-Care Ultrasound (POCUS) to the Perioperative Physician. 2018. https://doi.org/10.1017/9781316822548.013
4. Case courtesy of Dr Balint Botz , Radiopaedia.org. From the case rID: 64786

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