Quick Tips - Ultrasound Physics Doppler Shift
What is the arrow in the image referencing?
You guessed it! Zero Doppler Shift - Let's talk about why.
The Doppler effect or Doppler shift is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who described the phenomenon in 1842.
In Color ultrasound the Doppler shift works with the ultrasound system to fill in color within the vessel when there are frequency changes in relation to the observer (transducer). When the direction of the sound beam is perpendicular to the direction of flow. There is no appreciable Doppler Shift and no color filling as a result. This is due to the cosine of the angle being 90 degrees.
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Quick Tips - GYN Ultrasound ANATOMY
Which of the following structures is indicated by the arrow? Test your ultrasound anatomy skills!
You guessed it! This image is referring to the Broad Ligament.
The broad ligament is a two-layered fold of peritoneum that extends from the sides of the uterus to the floor and lateral walls of the pelvis inferiorly and the adnexa superiorly. The broad ligament helps to hold the uterus in its anatomic position. It covers the uterus, ovaries, and fallopian tubes and also includes nerves and blood vessels to these organs.
In this ultrasound image, the reason the broad ligament is easily identified is because of the fluid filling the pelvis. This highlights the location of the broad ligament. In normal settings, without a large amount of free fluid or the presence of other pathology, the broad ligament is rarely recognized on ultrasound.
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Quick Ultrasound Physics Registry Review Tips
If the level of an acoustic variable ranges from 55-105, what is the amplitude?
You guessed it! The answer is 25. But why?
The amplitude is calculated by determining the median between the range values and then calculating the difference between the median and high/low values of the range.
Amplitude is the amount of change in an acoustic variable. Amplitude is equal to the difference between average and the maximum or minimum values of an acoustic variable (or half the “peak-to-peak” amplitude).
In the example in the question, the median of the range is 80.
80 is 25 above 55 and 25 below 105 - therefore the amplitude is equal to 25.
The amplitude of ultrasound waves decrease as they travel through tissue, a phenomenon known as attenuation. For more info on amplitude and ultrasound physics, check out our other ultrasound physics resources.
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A Quick Look At Ovarian Doppler Waveforms
The following ovarian artery Doppler waveform would be indicative of what type of finding?
The answer is ABNORMAL FINDING - but why? Let's take a quick look at the Doppler waveform and what makes it abnormal.
The image reveals a low resistive waveform and is indicative of an abnormal ovarian Doppler finding. This can often be associated with Ovarian Torsion.
When a blood vessel has a LOW RESISTIVE Doppler waveform appearance, this is due to the need for extra flow. Vascular beds that require a higher blood supply show these low resistive waveforms on spectral Doppler. This means that the waveform has a high diastolic component, indicating constant flow throughout diastole. This is common for vessels that supply muscles when you're working out, or the stomach and intestines when you've just eaten, or for the vessels that supply the brain and vital organs.
However when a blood vessel shows LOW RESISTIVE characteristics for an organ that usually doesn't require a constant level of blood supply, this is a key marker that something isn't right and usually indicates stenosis. Blockage in the vessel will cause the vessel to become low resistive in order to compensate for the lack of flow.
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Scanning those tortuous Carotid vessels can sometimes be tricky! So here we'll go through 5 quick scanning tips to help you get great carotid images and accurate velocities.
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Diastology can often be confusing, as there have many updates to the standards and guidelines regarding how to assess and grade left ventricular diastology in the past few years. So let's dig in to how to assess this and the echocardiographer's role in evaluating diastology based on the updated
2016 ASE Guidelines.
So as cardiac sonographers, we should all know the basics... E/A reversal = Diastolic Dysfunction, but there is a little more to it than that. If you're not fully evaluating diastology with additional measures, you're probably missing some positive cases. Also the Intersocietal Accreditation Commission now includes reporting of left ventricular diastolic function as a requirement for echocardiography accreditation.
What exactly is diastolic dysfunction? This is a decrease in left ventricular compliance during diastole. While the ejection fraction and left ventricular systolic function are needless to say, pretty important, the diastolic function of the heart is important too. If the heart does not rest properly during diastole, then it cannot fill with the right amount of blood volume needed and eventually this can lead to heart failure and significant clinical implications. So it's important to know the left atrial pressures and end diastolic left ventricular pressures in order to determine the level of severity of the diastolic dysfunction. The updated guidelines break it down like this:
Grade 0 = Normal
Grade 1 = Impaired Relaxation/Diastolic Dysfunction
Grade 2 = Pseudonormalization
Grade 3 = Restrictive Pathophysiology
So how do we get to the diagnosis? Based on the updated standards from the ASE, determination of normal vs diastolic dysfunction is evaluated initially, based on the patient's EF.
If a patient has a normal ejection fraction then the algorithm looks at four components to determine whether or not the patient has a degree of diastolic dysfunction:
1. Average E/e’ > 14
2. e' velocity
-Septal e’ velocity < 7 cm/s
-Lateral e’ velocity <10 cm/s
3.TR velocity > 2.8 m/s
4. LA volume index >34ml/m2
If <50% are positive, the patient is considered normal. If >50% are positive, the patient has a degree of diastolic dysfunction. If only 50% are positive, then we are unable to determine whether the patient has diastolic dysfunction.
If the patient has a compromised ejection fraction, then we can assume that there is a degree of diastolic dysfunction and can grade it based on the E/A ratio.
When the mitral inflow pattern shows an E/A ratio <0.8 along with a peak E velocity of <50cm/sec, then the mean LAP is either normal or low and this is considered a Grade 1.
When the mitral inflow pattern shows an E/A ratio of >2, the mean LAP is elevated, consistent with Grade 3 diastolic dysfunction. Keep in mind patients with young or athletic patients may show this ratio in the setting of normal diastolic function. Also, patients in atrial fibrillation may exhibit a reduced or loss of the mitral A wave and may also produce similar findings.
For patients with reduced EF's that do not meet one of those parameters and the mitral inflow shows an E/A Ratio >0.8 AND the peak E velocity is >50 cm/sec OR E/A Ratio >8 but <2, then other parameters are required for determination of diastolic dysfunction.
1. Average E/e’ Ratio - average E/e’ ratio >14
2. TR Velocity - peak jet velocity >2.8 m/sec
3. LA Volume Index - >34 mL/m2
If 2 of 3 are negative, the patient is considered to have Grade 1 diastolic dysfunction, where if 2 of 3 are positive, then this is considered Grade 2.
So, are you confused yet? Let's look at the grading parameters a little closer.
GRADE 0 - NORMAL DIASTOLOGY
This means that left atrial pressures (LAP) are normal and the diastolic function is not impaired. The left ventricle relaxes normally throughout diastole and allows for complete diastolic filling. The E/A ratio in a normal setting, is between 1 and 2. This gradually reduces with age and E/A ratio >0.75 may be considered normal above 75 years.
GRADE 1 - IMPAIRED RELAXATION/DIASTOLIC DYSFUNCTION
Patients that do not have a NORMAL EF, will have a degree of diastolic dysfunction and are evaluated based on filling pressures of the left atrium. Left atrial pressures can be somewhat normal in a patient with Grade 1 diastolic dysfunction, but will increased as this progresses. Patients with Grade 1 diastolic dysfunction will have reduced e' velocities and prolonged deceleration time.
GRADE 2 - PSEUDONORMALIZATION
One of the biggest factors that our role as sonographers requires, is knowing your patient history. This will often help you know whether or not you're dealing with a normal waveform or pseudonormalization. Granted there are some other key factors but the most obvious is whether or not the patient has previously been diagnosed with diastolic dysfunction. If they have previously had reversal of the E/A waveform and now have a normal waveform pattern, this is a pretty good indicator that the patient is in pseudonormalization. Also, keep in mind some of the other factors associated with increased left atrial pressures, such as blunting or changes to the pulmonary venous waveform, as well as reduced e' velocities. When pseudonormalization is present, the valsalva maneuver can assist to "unload" the ventricle and to reduce filling pressures, causing the E/A reversal to be unmasked.
GRADE 3 - RESTRICTIVE FILLING PATTERN
Grade 3 diastolic dysfunction involves increased left atrial pressures and increased end diastolic left ventricular pressure. This may result in reversal of the pulmonary venous waveform and is often seen with the presence of left atrial enlargement and left ventricular hypertrophy.
ECHO DIASTOLOGY GRADING ANALYSIS TOOLS!
The newly updated algorithm for determining diastology and left atrial pressures can be a little overwhelming and difficult to follow, but we make it easy with our Echocardiography Analysis Tools which include our exclusive LV Diastology Assessment Tool! Quickly and easily determine and grade the diastology based on the updated ASE guidelines. Also there are many other parameters that affect diastology and the application of the diagnostic criteria, such as age, athletic hearts and other factors. Learn and review these additional factors and an in depth study of diastolic dysfunction in our MASTERING LV DIASTOLOGY CME COURSE!
REFERENCE: ASE/EACVI GUIDELINES AND STANDARDS Recommendations for the Evaluation of Left Ventricular Diastolic Function by Echocardiography: An Update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging; Nagueh et al
Please note: allaboutultrasound.com and iheartecho.com are not endorsed by or affiliated with the American Society of Echocardiography
Re-post from https://www.iheartecho.com/echoblog/the-echocardiographers-role-in-lv-diastology-assessment
Mastering Echocardiography can be tough, especially when it comes to complex processes like Constrictive Pericarditis. Patients with Constrictive Pericarditis do not present for typical pericarditis symptoms. Instead, they present with symptoms of heart failure and so this can often be a challenge for even very skilled sonographers to identify the subtle differences between Restrictive Cardiomyopathy and Constrictive Pericarditis. These two disease processes can appear very similar on echocardiography. However, there are a few things that clue us into the correct diagnosis.
Constrictive Pericarditis is seen with a fibrotic, thickened pericardium, which insulates the ventricle and constricts the ventricle from fully relaxing during diastole. Whereas, Restrictive Cardiomyopathy results in a thickened myocardium, which inhibits the ability of the ventricle to relax and also results in abnormal diastolic function. However, that's where the similarities end.
First of all, we need to evaluate for interdependence of the ventricles. But what does that mean? Ventricular interdependence is when there is a respiratory ventricular septal shift. This then leads to an increase in the volume of one ventricle associated with a decreased volume in the opposite ventricle. This can be tricky to diagnose, so it takes a pretty detailed echo exam and a keen eye of the sonographer and physician.
Secondly, when evaluating for constriction, we will need to look at respiratory changes to the Doppler waveform patterns. The respiratory changes in the Mitral inflow pattern will show a variation of greater than 15% when constriction is present. Whereas, with restriction, this waveform pattern will show a restrictive filling pattern with an E/A ratio >2.0 and deceleration time <160ms.
Another key factor in determining constriction vs. restriction is the E/e' ratio and diastolic function. Remember that both disease processes will have a degree of diastolic dysfunction. Normal left ventricular function will typically show a lateral e’ greater than septal/medial e' velocities, because the septal wall is somewhat restricted and the lateral wall is more free to move. However, with constriction the pericardium is insulating the ventricular movements and does not allow for full relaxation and movement of the lateral wall. This results in mitral annulus reversus, which is a decreased lateral e' velocity and compensatory increase in tissue velocities in the septal/medial annulus. Restrictive patterns in tissue velocities will show an overall decrease in both the lateral and septal e' velocities.
Additionally, with constriction, this will result in expiratory hepatic vein reversal. But why does this occur? Remember that air moves from areas of high pressure to low pressure, which allows for air flow into the lungs. During expiration, the volume of air (and the pressure) of the thoracic cavity decreases, causing the intrapulmonary pressure to rise above the atmospheric pressure. However, with constriction, the pericardium is insulating the intracardiac chambers and this keeps them from tracking normally with intrapulmonary pressures. Remember the pulmonary artery and aorta are OUTSIDE of the pericardium.
So with constriction the thorax pressure and the pulmonary venous pressure will drop, but there are phasic filling differences within the heart, because the gradient to fill the left side of the heart is decreased. The heart is no longer able to push outward against the pericardium, so the pressure is forced inward into the cardiac chambers. So during expiration, the pressure in the right atrium causes flow reversal in the hepatic veins. Whereas, with chronic late stages of restriction, there is an inspiratory reversal during diastole, because there is no shifting of septum and the right heart cannot accommodate increased flow which results from chronic diastolic dysfunction and this causes hepatic vein reversal.
While diagnosing Constrictive Pericarditis on echocardiography can certainly be a challenge, it can be done with confidence. Paying close attention to the details and recognizing when your patient with heart failure symptoms might actually be more than meets the eye, can help to make the correct diagnosis and ensure adequate treatment for your patient.
Want more information on the differences between Constrictive Pericarditis and Restrictive Cardiomyopathy, including Strain Imaging methods? See our E-Learning Course Mastering Constrictive Pericarditis and earn 1 SDMS CME credit.
Studying for that ARDMS or CCI ultrasound registry exam can be brutal!
So we've covered this topic a few times before, but it is always helpful to revisit some of these study tips. Passing your ARDMS or CCI Ultrasound Registry exam is easier than you think.... There's no need to worry!
Don't stress over it... just study. Mastering ultrasound physics or any other ultrasound specialty can be so overwhelming and often it can you make you want to give up. Don't give up! You've got this! Keep on studying and use these simple tips to study and PASS your ultrasound registry!
Hope these tips help you pass your ultrasound registry. For more help and tools to pass - check out our ultrasound registry reviews with quizzes and tools to help you master the ARDMS and CCI registries! Sign up for a FREE TRIAL (no credit card needed) of our Ultrasound Physics SPI Registry Review Course that includes our PASS GUARANTEE and pass with us!
It is so easy to get caught up with our patients who need our immediate attention for things that aren't even ultrasound related and even seasoned sonographers can ignore physics altogether, but when we take it back to the basics, this is where image optimization begins. So, let's take a step back and look at the basics again..... Doppler principles and hemodynamics... I know, I know, for some just saying the words brings tears to their eyes as they recall sleepless nights studying for the Ultrasound Physics registry! But no need to fear! Doppler is simple when you break it down. So the Doppler Effect is quite simply either a positive shift which is a compression in the wavelength (a higher frequency) or a negative shift, which results in an elongated wavelength, (a lower frequency) and this is of course all relative to the observer.
So what does this have to do with Doppler ultrasound? I'm glad you asked.
Doppler frequency shifts come from moving red blood cells and give us the spectral display that we see in Continuous Wave and Pulse Wave Doppler. The velocities obtained from these frequency shifts can also be displayed in Color Doppler, superimposed on top of the 2D ultrasound image. This is a method of displaying the mean or average velocity, while the spectral Doppler display can quantify specific velocities, like the peak systolic and end diastolic velocities, at a point in time.
Because the Doppler frequency shift is relative to the position of the observer, this is important when placing the Doppler sample and angle of insonation. The Doppler sample volume is the "observer" and the frequency shift created by the moving red blood cell is what we are evaluating on the spectral display. But what happens if the observer changes position? The velocity observed will be different. This is extremely important for Doppler Angle. The Society for Vascular Ultrasound recommends that scanning angle be maintained between 45-60 degrees. While we know that the closer to 0 degrees, the more accurate the velocity result because of the math and the cosine of the angle, try getting that on a your average carotid Doppler. It is often not attainable and so for reporting and to maintain consistency in the lab, it is best to stay within the range of what can be easily obtained on most exams.
So as you can see from the image, as the angle of insonation is moved, the velocity result is SIGNIFICANTLY impacted. This can be a very big factor in following up serial ultrasound studies if the same Doppler angle is not used for follow up exams. This is why it is so important to look at the previous study images, especially if there is disease. So when you're scanning don't forget these very basic settings and factors that can have a large impact on your patient's results.
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