The Nuts and Bolts of Fine Tuning Your Ultrasound Machine to Examine the Fetal Heart - SD

Introduction

Welcome.

My name is Dr. Gregory Devore.

The title of this presentation is The Nuts and Bolts of Fine Tuning your Ultrasound Machine to examine the Fetal Heart.

This lecture will discuss methods in which the user can enhance the images obtained during the examination of the fetal heart.

The topics will cover optimization of the image display, the B mode, image, and color, and power doppler images.

Optimization of the Image Display

Let's begin with optimization of the image display.

This is often neglected by the examiner.

However, by making a few adjustments, the image of the fetal heart can be dramatically improved.

Let's first review some principles of the human eye to will assist us in maximizing the image display.

When we examine the retina of the eye, we have learned that there are two components, rods and cones that optimize visualization.

The rods are used primarily for evaluating shades of gray and the cones are used to discriminate colors.

When ultrasound first became available, it was displayed first as black and white and then various shades of gray.

Therefore, the rods were used primarily when examining the ultrasound image.

One advantage of the rods is better detection of motion when compared to cones.

However, when improved resolution is required, the cones are more efficient.

Measure density occurs for the rods and cones in the retina show an enormous density of cones in the HOA centralis from this area of the eye color vision occurs and is associated with the highest visual acuity.

This illustrates the difference between using the cones and rods of your eye.

Notice that when the CP image is on the screen, your eye muscles relax and when the gray image is on the screen, your eye muscles contract.

This suggests to me that there is less eye strain when the CP image is displayed than when observing the gray scale image.

For this reason, I usually scan using cp.

Now watch the image and see if you experience the same change in eye muscle contraction and relaxation that I have observed.

This slide illustrates different color enhancements like c pia, which is the brown colored image.

Some may prefer the other colors.

Enhancing the B-Mode Image

Let's now examine ways to enhance the BMO image when evaluating the fetal heart.

The first topic will be discussion regarding the differences between optimal images for non-cardiac and cardiac structures.

This is an example of soft tissue imaging.

When the examiner selects various presets for soft tissues, the goal is to maximize the differences between the tissues.

This example, the kidneys are easily differentiated from the surrounding structures.

When examining the bones, the examiner should maximize the differences between the soft tissues and the bone.

When examining the heart, the examiner should maximize the difference between the myocardium and the blood pool.

While at the highest achievable frame rate, let's now examine how to maximize the frame rate.

This diagram illustrates an important concept.

As one increases the width, the frame rate decreases.

When the width is decreased, the frame rate increases.

The reason for having a higher frame rate is to increase the number of images that chronicle a cardiac event, such as wall motion or valve movement.

The width of the frame is maximal resulting in a frame rate of 50 hertz or 50 frames per second.

Another method to decrease the frame rate is to decrease the depth of the image.

Therefore, to maximize the frame rate, the examiner can decrease the depth and decrease the width of the image.

Now the frame rate is minimized, which results in a frame rate of 122 hertz or 122 frames per second.

This illustrates a maximal depth of 26 centimeters in a frame rate of 62 hertz or 62 frames per second.

By decreasing the depth further, the frame rate increases to 79 hertz or 79 frames per second.

Further, a decrease in the depth to 10.1 centimeters increases the frame rate to 124 hertz or 124 frames per second.

Finally, with the depth setting of 8.3 centimeters, the frame rate is 138 hertz or 138 frames per second.

Another method to increase the frame rate is to zoom the image.

This illustrates how this is done from the original image and area of interest is selected and then the zoom button is activated.

This increases the image size for the area of interest resulting in an increased frame rate.

This illustrates the concept just described.

The box of the area that will be zoomed is identified.

The frame rate is 50 hertz or 50 frames per second.

The image is now zoomed with the rate of 174 hertz or 174 frames per second.

Optimization of the B-Mode Image for Cardiac Structures

This next section will discuss methods for optimization of the VM mode image for evaluation of cardiac structures.

Let's now review optimizing the image.

There are several techniques the examiner can use to optimize the BM mode.

Image harmonics and cross beam technologies requires the examiner to activate these functions prior to image acquisition.

Speckle reduction can be activated either prior to or following image acquisition.

I'll discuss each of these functions in subsequent slides.

Let's now review harmonics.

This is a link to website in which the physics of harmonic imaging is discussed by CRN CO in 2002.

I found this site most informative.

The image and panel A illustrates the transmitted frequency is a solid line and the receive frequency is a dotted line.

Besides generating the fundamental frequency, the tissues also generate additional or harmonic frequencies as a result of tissue distortion of the fundamental propagated sound wave.

Panel B illustrates the receive fundamental frequency and the additional harmonic frequencies.

Harmonic frequencies are multiples of the fundamental frequency.

For example, if the fundamental frequency is three megahertz, the harmonic frequencies are six and nine megahertz.

However, as the harmonic increases, the amplitude decreases.

Therefore, clinically, we can only use the second harmonic.

This is an example from the gallbladder.

Notice that when harmonics is activated, there are no reverberations in the lower image.

Therefore, harmonics improves contrast resolution, border detection, and reduces artifact.

Let's now review cross beam imaging or CRI.

This illustrates the native image on the left.

The native image with CRI activated on the right notice that the definition of the wall blood pool interface is improved.

Let's examine specker reduction or or SRI.

A third option is specker reduction imaging or SRI, which improves contrast resolution, border detection, and reduces artifact.

This can be activated either before or after image acquisition occurs.

This is an example of SRI.

These are images recorded simultaneously.

The left is a native image with no enhancements activated.

On the right is the same image with SRI activated.

Let's summarize. Optimizing the image.

Therefore, the examiner can activate any one or a combination of features to improve the image of the fetal heart.

The desired image should contain the following.

One, a clear interface between the blood pool and endocardium.

Two, a high frame rate and three well-defined anatomical structures.

This is a simultaneously recorded image.

The image on the left is native with no features activated.

The image on the right has three features, activated harmonics, CRI and SRI.

Optimizing the Display of Color and Power Doppler Ultrasound Images

Let's now discuss how to optimize the display of color and power Doppler ultrasound images.

This section will cover the following basic principles, color settings, initial setup of the sub menu and pearls.

The examiner should first optimize the BM mode image as described in previous slides, and then optimize the color and power dotter images.

We're now going to examine the features of color Doppler settings.

Although we'll use color Doppler as our example, the same principles apply to power Doppler settings as well.

When the user adjusts to color Doppler settings, there are two structures, the fetal heart and the umbilical cord that can be used for a reference When optimizing The color Doppler settings, note that the umbilical vein is the size of 50% of the right ventricle and the umbilical artery is the size of the foraminal valley.

Depending upon the position, the examiner may select either of these structures to use for adjusting the color Doppler image.

This slide represents the main screen and submenu of one of the ultrasound machines used in my practice.

While some of the terminology may vary between manufacturers, the concepts are the same.

Let's examine each of these features and see examples of the effect on the color Doppler image.

We will first examine the features that are often found on the main console.

Many of the features can be adjusted or activated while the image is being acquired.

Let's first examine the gain control.

The gain control is set too low.

Then no color will be displayed on the screen.

If it's set too high, then random speckle appears.

Let's view examples of this concept. In this image.

The gain control is set appropriately In this image.

The gain control is set too low.

Notice the absence of the color Doppler signal.

The gain control in this image is set too high.

Notice a random speckle that appears on the image.

What does the quality setting do?

This setting affects the color resolution and the frame rate.

If the setting is high, the color doppler resolution is improved while lowering the frame rate.

If the quality setting is normal, then there is normal resolution with a medium frame rate.

If the quality setting is low, there's a lower resolution but a higher frame rate.

In this image, the quality setting is low with a frame rate of 41.

Notice how the color bleeds over the gray scale image.

This example, the color does not discriminate between the two umbilical arteries.

This image illustrates the high setting.

Notice how the colors within the borders of the vessels and the two umbilical arteries are delineated from each other over.

The frame rate has decreased the 31 frames per second.

Now, let's examine the wall motion filter.

The wall motion filter has a number of settings ranging from low one to max.

When the filter is set to low, notice the color doppler bleeds outside the walls of the vessels.

When the wall motion filter is set to high, notice that the color remains within the vessels.

When the examiner increases or decreases the PRF, it's equivalent to increasing or decreasing the velocity range.

The PRF or velocity range setting can be adjusted to optimize the color doper image.

This example, the PRF is set too low, thus resulting in aliasing.

In this example, the PRF has been adjusted demonstrating an ideal color Doppler image.

The invert function simply inverts the color display for direction of blood flow.

This is useful when inverting the B mode image on the screen and desiring to display the color flow, the direction the blood is actually flowing.

On the B mode image, this is the 2D and 2D color function.

This setting displays the B mode image without color.

Doppler on the left. The color doppler superimposed on the B mode image on the right, right.

This is a useful display that I used in almost all cases.

This is the threshold adjustment.

The threshold eliminates small color noise or motion artifact signals in the color image.

It can only be adjusted in the freeze mode.

In this image, the threshold is set at 10 resulting in color overlying the ventricular walls.

In septa Using a higher threshold setting, the interface between the color doppler and the walls is better delineated.

This is the sub menu page.

Each manufacturer may have different options in the sub-menu selections, however, the features are very similar.

Let's now explore what these features are, how they may affect the image.

Display selection allows the examiner to choose various settings depending upon how the examiner desires the color do to be displayed.

This is a display of the color maps that are available, velocity, velocity and turbulence, velocity and power, power and turbulence and turbulence.

Let's now examine the color map setting.

This expands upon the various iterations of the previous color maps to provide the user with more choices.

This represents the variations of the five main display maps described previously.

The transmit frequency has three settings, high, low, and mid.

That allows the user to select different velocity settings for a given PRF.

When high is selected, lower velocities are displayed and the penetration depth is reduced.

When low is selected, higher velocities are displayed and the penetration depth is increased.

The mid selection is between the high and the low flow resolution adjusts the axial resolution.

This is an important setting because it may improve the differentiation between myocardium and the blood pool.

A low flow resolution setting demonstrates larger pixels in the color map.

This is noticeable at the edges of the color map.

As blood enters the ventricular chambers, the high flow resolution setting creates smaller pixels of color.

Let's toggle between the two views so you can see the difference.

This is the scale setting menu.

This simply allows the examiner to display velocity of either kilohertz centimeters per second or meters per second.

I prefer centimeters per second.

This is the balance feature and is important to understand.

This function has also been called the right priority by other manufacturers.

In essence, it controls the amount of color displayed over B mode echoes.

Adjusting. This setting allows the examiner to balance the display between color doppler and B mode echoes.

Example of this adjustment will illustrate how this works in this image.

The balance is set at 2 25.

When examining this clip, it is evident that color pixels are overriding the walls displayed on the B mode image.

Therefore, it's impossible to identify the interface between the blood pool and the walls of the heart.

Changing the balance to 25, the color doppler is now confined to the blood pool does not extend over the walls.

Let's now examine the smoothing feature.

This performs temporal averaging, which improves the appearance of the color Doppler image.

There are two adjustments by adjusting the rise to a low value.

This prevents flooring of the color Doppler image with movement, adjusting the fall either prolongs or shortens the displayed flow.

Let's review some examples of this function.

In this example, the rise and fall are set.

At one notice, their frame rate is 29 hertz.

In this example, the rise is increased to five in the fall to 12.

Even though the frame rate is 29 hertz, the color seems to persist on the screen longer.

It does not appear to be in synchrony with the beam mode image.

In this example, the rise is 12 and the fall is 12.

Notice that by increasing the rise, the color has almost disappeared from the screen.

It's important to see how adjusting these settings affects the image.

The ensemble setting controls the number of pulses for one displayed color doppler line.

If one increases the ensemble, the frame rate decreases, but the color detail improves.

If the ensemble is decreased, the frame rate increases, but the detail of the color image decreases.

Let's see examples of the effects on the color display.

When we adjust these settings.

In this example, the ensemble is set to eight and has a corresponding frame rate of 39 hertz.

The ensemble has now been increased to 33 with a frame rate decrease in 15 hertz.

Let's now talk between these two settings and see the difference.

The line density function determines the density of lines in the color box.

For example, the lower the setting, the greater the distance between the lines and size of the color pixels.

Let's review the effect of changing the setting on the image.

This image illustrates a line density of one.

Notice that their frame rate is 28.

The definition of the color dopper image is blurry, lacking detail and covers the interal septum.

This would be considered artifact.

In this example, the line density has been increased to six.

The frame rate has dropped to 14.

However, the color dopper contains more color pixels resulting in better discrimination between the blood pool and the walls and septa of the heart.

The line density has now been increased to 10.

Their framing is now further decreased to seven.

The color pixels are smaller with even more detail than the previous setting.

User selects a setting for the line density.

The selection should provide the highest line density with an acceptable frame rate.

The next option is artifact suppression.

This setting reduces movement artifact for an evaluation of the cardiovascular system.

This should be set to off.

Next is the baseline setting.

This changes the baseline and prevents icing in one direction.

This is a clip that illustrates different colors displayed when the baseline is set in the middle.

In this example, the baseline has been adjusted upwards, resulting in primarily a blue display.

This is an example of adjusting the baseline upwards.

This illustrates setting the baseline at the bottom resulting in a red color Doppler image display.

This illustrates the color doppler image when the baseline is at the bottom.

Let's now examine the line filter setting.

The line filter determines the amount of lateral filtering that occurs, which is the balance between lateral resolution and image noise.

In this example, the line filter is off.

Notice how the color is displayed beyond the borders of the vessels.

In this image, the line filter is seven.

The color dopplers now can find more within the vessels.

This sequence illustrates the changes in the image when the line filters adjusted from off to seven.

Notice that as the line density has increased, the color stays within the boundaries of the vessel walls.

Preferred Settings for Sub-Menu

Let's now review examples of settings for the sub-menu.

For color, HD power and power doppler ultrasound.

This table lists the settings that I prefer for the sub menu when using color doppler ultrasound, let's review these settings.

Display velocity and turbulence. Color map three.

Frequency, lower mid flow resolution, mid one scale centimeters per second.

Balance high, one 30, smoothing rise one fall three.

Ensemble seven, line density eight.

Artifact suppression off baseline, middle line filter seven.

This table list of preferred settings for HD power doppler.

Let's review these settings. Display not applicable.

HT map one.

Frequency, lower mid flow resolution.

Mid one scale, not applicable.

Balance high one 30.

Smoothing rise one, fall three.

Ensemble seven, line density. Eight.

Artifact suppression off baseline, not applicable.

Line filter seven.

This table lists the preferred settings for power doppler ultrasound.

Let's review these settings.

Display not applicable PD map one.

Frequency, lower mid flow resolution, mid one scale, not applicable.

Balance high one 30, smoothing rise one, fall three.

Ensemble seven, line density eight artifact suppression off baseline, non-applicable line filter seven.

Pearls for Using Color Doppler Ultrasound

This section contains pearls that may be useful as you consider using color.

Doppler ultrasound.

This is the four chamber view of a 24 week fetus.

Do you see any evidence of an abnormality?

The color doppler demonstrates two findings.

First, there is a pericardial effusion.

Second, there is a ventricular septal defect.

This is the short axis view of the level of the ventricles in the 24 week fetus.

Do you see any abnormalities?

The color doppler illustrates the shunting ventricular septal defect.

This is the four chamber view from a 30 week fetus.

Do you see any abnormalities?

This illustrates a shunting ventricular septal defect.

This is a 35 week fetus. What is wrong with this image?

This illustrates mitral regurgitation, aortic stenosis, and left to right flow across the foraminal valley.

This image illustrates the color Doppler image when the PRF is 84 centimeters per second.

Do you see the VSD?

This is the same image when the PRF is 27.

Now you see the shunting adjusting the PF may alter what you see on the screen.

If you would like to see the interface between the blood pool and the walls of the chambers or outflow tracts as accurate as possible, it's important to adjust the balance downwards.

Here's an example in which the balance is set low.

Using the HD parado ultrasound, notice the interface between the blood pool and the walls of the chambers and outflow tracts of the heart.

This is HD Parado with a balance set low.

Notice the interface between the blood pool and the walls of the chambers and the outflow tracts of the heart.

Thank you.