Tag Archives: color Doppler

Advanced Imaging of the Fetal Heart

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Following the first demonstration of the fetal face in 1989 and the advent of fast processors around 2000, 3D and 4D ultrasound have become important tools in obstetric imaging over the past decade. Unlike 2D imaging, 3D ultrasound provides a volume of a region of interest that contains an infinite number of 2D planes. Mechanical and electronic transducers have the ability to acquire volumes of target organs through sweeps, and fast processors are able to display the acquired information within seconds. The operator can then choose to display this information in a multiplanar format of 2D images or as a spatial volume projecting the external or internal anatomic features on the screen.

Static 3D, spatiotemporal image correlation (STIC), or 4D imaging can be used to acquire a cardiac volume with a mechanical or electronic transducer. The best cardiac volumes are acquired using the STIC technique. Ideally, it can be used for offline assessment of cardiac structures and movements. Color Doppler, power Doppler, bidirectional power Doppler (high-definition flow), and B-flow modes can be combined with STIC acquisitions.

These volumes can be displayed with the color information alone, the grayscale information alone, or a combination of both, referred to as “glass-body” mode. A light source can emphasize the effect of depth.

If anomalies involving the four-chamber anatomy can be visualized similarly to the 2D image with color Doppler, anomalies involving the great vessels clearly demonstrate the superiority of 3D. Size difference, flow direction, and spatial relationship of the great vessels are some of the information that can be visualized with 3D color Doppler and “glass-body” mode. 3D imaging can, therefore, be used to explain anomalies to future parents and explore treatment options with colleagues.

The major limitations of the STIC technique include delayed acquisition time and movement artifacts due to fetal movements or maternal breathing movements.

Here are two examples where 3D color Doppler and “glass-body” mode are superior to 2D imaging in the assessment of fetal heart anomalies. 

A double aortic arch results from the persistence of right and left aortic arches. The left ductus arteriosus persists while the right ductus arteriosus regresses. Each aortic arch gives rise to a subclavian and a common carotid artery. A double aortic arch forms a tight vascular ring around the trachea and esophagus. This condition requires surgical intervention postnatally.

3D ultrasound image displaying major fetal heart structures, including the left and right aortic arches (LAo and RAo), pulmonary artery (PA), ductus arteriosus (DA), and superior vena cava (SVC).
3D ultrasound with the grayscale information alone in a fetus with the diagnosis of double aortic arch. The aorta can be seen bifurcating into a right and left aortic arch, forming a complete vascular ring around the trachea.

The part of the complete ring behind the trachea is not seen in this plane. It is better demonstrated with 3D color Doppler.

3D ultrasound image showing a fetus diagnosed with a double aortic arch, labeling the right aortic arch (RAo), left aortic arch (LAo), ductus arteriosus (DA), and pulmonary artery (PA). The image highlights the complete vascular ring formed around the trachea.
3D ultrasound in color Doppler in the same fetus. Note the bifurcation of the aortic arch into right and left aortic arches with the left ductus arteriosus, thus forming a vascular ring surrounding the trachea.

A coronary artery fistula (CAF) is an abnormal connection between a coronary artery and a cardiac chamber or a great vessel.

3D color Doppler ultrasound image showing the positioning of the pulmonary artery (PA) and aortic arch (Ao) in fetal heart anatomy.
3D color Doppler image showing fetal aortic arch (Ao) and pulmonary artery (PA) with visual indicators of blood flow direction.
3D ultrasound image of a fetal heart showing the right ventricle (RV), left ventricle (LV), right atrium (RA), and left atrium (LA) with color Doppler overlay.

3D color Doppler and “glass-body” mode allowed the visualization of the CAF over an entire cardiac cycle.

References:

Chaoui R, Heling K-S. 3D Ultrasound in Prenatal Diagnosis: A Practical Approach. 2nd ed. Berlin, Germany: DeGruyter; 2024.

Abuhamad A, Chaoui R. A Practical Guide to Fetal Echocardiography: Normal and Abnormal Hearts. 4th ed. Philadelphia, PA: Lippincott-Williams Wilkins; 2022.

Tekesin I, Uhlemann F. Prenatal diagnosis of coronary artery fistula using 2D and 3D/4D ultrasound. Ultrasound Obstet Gynecol 2017; 51:274-275.

Vladimir Lemaire, MD, RDMS (Ob/Gyn, FE), is a Maternal-Fetal Medicine Sonographer at UT Southwestern Medical Center in Dallas, Texas.

This posting has been edited for length and clarity. The opinions expressed in this posting are the author’s own and do not necessarily reflect the view of their employer or the American Institute of Ultrasound in Medicine.

Optimize Screening of the Fetal Heart

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The keys to optimizing screening of the fetal heart are to understand how the ultrasound machine’s functions and controls can affect your image, utilize the entire maternal abdomen, adjust your image presets, and optimize your angle of insonation. So how do you do all that?

You start with the transducer. Be sure to select a transducer that allows for adequate penetration and optimal resolution. All transducers have different operating frequencies and capabilities; high frequencies produce better detail resolution but, of course, with limited sound penetration. These frequencies can be applied in all trimesters, particularly since the advent of high-resolution transducers, which are helpful when imaging delicate heart structures, such as the valves and vessel walls. If, however, the imaging is subpar with a high-frequency transducer, switch to a low-frequency transducer, which is more useful in your patients with a high body mass, in the late second trimester, in the third trimester, and in the event that there is also polyhydramnios syndrome, even when there is rib shadowing. Keep in mind too, that transvaginal imaging is helpful for evaluating the fetal heart in the first or early second trimester, in the event that there is suspected fetal cardiac abnormality, and even when maternal body habitus causes imaging to be difficult.

For your next step, adjust your image presets to optimize your temporal resolution so that you maintain a high frame rate of greater than 25 frames per second. A few of the technical settings that affect temporal resolution are the frame rate (in Hz), frequency selection, depth & focus, sector angle width, and zoom magnification. The better the temporal resolution, the improved detail resolution. To optimize your image, avoid unnecessary depth and make sure your focus is on the region of interest. A multiple focal zone may be applied to structures that don’t move, such as the placenta, but when looking at the 4-chamber heart, you will need a single focal zone. In addition, adjust your sector angle width. Reducing it increases lateral line density, which improves the image quality. Finally, make small adjustments to your settings, such as applying speckle-reduction imaging, adjusting the dynamic range (more or less gray), and scanning in different tones.

When incorporating color Doppler, the color box, color gain, wall motion filter, velocity scale/pulse repetition frequency (PRF), balance, and angle of insolation can each affect the image. The color box slows the frame rate by a significant degree so the smaller the color box, the higher the frame rate. Set color gain initially on low (ie, less color) and gradually increase it until you have optimized the amount of color. The wall motion filter eliminates signals caused by wall motion and low velocities. The velocity scale is the range of mean velocities or PRF in the region of interest. If it is too low, it can produce aliasing, which could lead to a misdiagnosis; too high and the low-velocity flow will not be displayed. Here is a sample of potential ideal velocity flows:

High-velocity flow (>60–80 cm/sec)Low-velocity flow (<30 cm/sec)
Atrioventricular valvesPulmonary veins
Semilunar valvesBicaval (IVC/SVC)
The great vessels (3VV)Evaluating atrial and ventricular septum
The scale is dependent on factors such as body mass index and fetal positioning within the uterus.

The balance allows you to display how much grayscale and color Doppler information you would like to see. Reducing the balance will show grayscale elements within the color box. And, finally, the angle of insonation is very important to keep in mind as the signal from the transducer should be parallel to the direction of blood flow.

J of Ultrasound Medicine, Volume: 35, Issue: 1, Pages: 183-188, First published: 01 January 2016, DOI: (10.7863/ultra.15.02036)

One of the major challenges in ultrasound imaging is scanning a morbidly obese patient. This is a result of the increased distance between the transducer and fetal anatomy, causing degraded resolution. Some techniques for optimizing your imaging in these cases include scanning above the tissue, when the patient’s bladder is full, through the umbilicus, or when the patient is in the Sim’s position (with the patient on their left side), which allows the extra tissue to fall to the left side. Also, keep in mind that when scanning an obese patient, the color doesn’t always fill in. Lowering the color attenuation can help clarify the image.

So, remember, the key to optimizing your fetal heart imaging is in understanding your machines’ functions and controls and how they can affect your image, utilizing the entire maternal abdomen, adjusting your image presets, and optimizing your angle of insonation!

To learn more and see case scenarios, see the American Institute of Ultrasound in Medicine’s (AIUM’s) on-demand webinar with speaker Mishella Perez, MS, RDMS, RDCS, “Fetal Heart Image Optimization: The Key to Screening”, from which this post was adapted. AIUM members can access the webinar for free.

Interested in learning more about fetal imaging? Check out the following resources from the American Institute of Ultrasound in Medicine (AIUM):

Is it Nuts to Think About Sparing the Testicles?

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The testi-monial

On my ultrasound list today, patient X, returning for a follow-up, was recounting his ‘close shave’ from losing one of his testicles after a suspected lump was detected during an ultrasound examination at his local hospital when he had pain in the scrotum. He was initially listed for theatre for an orchiectomy and the patient was grateful that someone stopped that and referred him to us for a repeat scan, this time with an adjunct contrast-enhanced ultrasound, which showed the abnormality in his testicle was an infarct instead of a tumor (Figure 1), which improved on follow-up (Figure 2).

Figure 1: Grayscale (left) and contrast-enhanced ultrasound (right) of patient X’s right testicular focal abnormality. Contrast-enhanced ultrasound showed no enhancement within the abnormality.
Figure 2: On follow-up contrast-enhanced ultrasound, it reduced in size and again showed no enhancement, supporting the diagnosis of a resolving infarct.

Incidentally detected testicular focal abnormality inevitably generates a great amount of anxiety, both for patients and doctors involved.

Why?

Ultrasound is good at picking up lesions. The problem is that, often, we do not know what they are, or what to do with them. While the old surgical dogma of ‘if in doubt, take it out’ does a good job in dealing with the uncertainty, it does appear to be an overly aggressive anxiety-relieving strategy, and not without consequence, as orchiectomy comes with associated endocrine, reproductive, and psychological impact.

It is worth noting that this problem is further exacerbated by the increased use of ultrasound for a variety of indications, which led to an increasing number of incidentally detected small focal testicular lesions. Many incidentally detected lesions are benign.

Even with the most beneficial of intentions, is scrotal ultrasound causing harm?

What could we do?

Which test tickles your fancy?

Although a variety of tools have been at the clinician’s disposal, the preoperative diagnoses of testicular masses remain uncertain in many cases. Tumor markers are often not raised in patients with malignant testicular tumors. MRI is considered a second-line tool for the characterization of focal testicular lesions; high cost, long study time, lack of standardization, and expertise are some of the drawbacks.

In most cases, ultrasound remains the primary diagnostic test to facilitate decision-making. Lack of flow on color Doppler (CD) increases the probability of a benign lesion but must be interpreted with caution as a substantial proportion of malignant lesions show no detectible vascularity.1 Microflow techniques may increase sensitivity,2 but the evidence is lacking for its value in assessing small testicular lesions. Imaging with contrast-enhanced ultrasound (CEUS) and elastography provides additional information.3,4 CEUS is a particularly valuable technique. The unique value of CEUS is the unequivocal demonstration of the lack of vascularity likely to be encountered in benign lesions, such as an infarct,5 hematoma,6 or epidermoid cyst,7 allowing for “watchful waiting” with ultrasound.8 Contrast dynamics may help differentiate benign from malignant solid masses, but this technique is not yet sufficiently robust for routine clinical use.9 Strain elastography could potentially identify the “hard” lesion as more likely malignant and the “soft” lesion benign on strain elastography.10 Shear-wave elastography has been less extensively evaluated but may also show differences between benign and malignant testicular lesions.11

I am not advocating that these ultrasound techniques are entirely diagnostic, but I am certainly suggesting that when combined with clinical and laboratory information, ultrasound technology is available for a more accurate assessment of the risk of malignancy. This may facilitate more desirable testis-sparing management options, such as ultrasound surveillance or testis-sparing surgery (TSS), to be considered, and avoid unnecessary orchidectomies.  

It is not nuts to suggest sparing the testicles.

The ball’s in your court.

References

  1. Ma W, Sarasohn D, Zheng J, Vargas HA, Bach A. Causes of avascular hypoechoic testicular lesions detected at scrotal ultrasound: can they be considered benign? Am J Roentgenology 2017; 209:110–115.
  2. Lee YS, Kim MJ, Han SW, et al. Superb microvascular imaging for the detection of parenchymal perfusion in normal and undescended testes in young children. Eur J Radiol 2016; 85:649–656.
  3. Huang DY, Sidhu PS. Focal testicular lesions: colour Doppler ultrasound, contrast-enhanced ultrasound and tissue elastography as adjuvants to the diagnosis. Br J Radiol 2012; 85 Spec No 1:S41–S53.
  4. Huang DY, Pesapane F, Rafailidis V, et al. The role of multiparametric ultrasound in the diagnosis of paediatric scrotal pathology. Br J Radiol 2020; 93(1110):20200063.
  5. Zebari S, Huang DY, Wilkins CJ, Sidhu PS. Acute testicular segmental infarct following endovascular repair of a juxta-renal abdominal aortic aneurysm: case report and literature review. Urology 2019; 126:5–9.
  6. Yusuf GT, Rafailidis V, Moore S, et al. The role of contrast-enhanced ultrasound (CEUS) in the evaluation of scrotal trauma: a review. Insights Imaging 2020; 11:68.
  7. Patel K, Sellars ME, Clarke JL, Sidhu PS. Features of testicular epidermoid cysts on contrast-enhanced sonography and real-time tissue elastography. J Ultrasound Med 2012; 31:115–122.
  8. Shah A, Lung PF, Clarke JL, Sellars ME, Sidhu PS. Re: New ultrasound techniques for imaging of the indeterminate testicular lesion may avoid surgery completely. Clin Radiol 2010; 65:496–497.
  9. Pinto SPS, Huang DY, Dinesh AA, Sidhu PS, Ahmed K. A systematic review on the use of qualitative and quantitative contrast-enhanced ultrasound in diagnosing testicular abnormalities. Urology 2021; 154:16–23.
  10. Fang C, Huang DY, Sidhu PS. Elastography of focal testicular lesions: current concepts and utility. Ultrasonography 2019; 38:302–310.

Roy C, de Marini P, Labani A, Leyendecker P, Ohana M. Shear-wave elastography of the testicle: potential role of the stiffness value in various common testicular diseases. Clin Radiol 2020; 75:560 e9–e17.

Dr. Dean Huang, FRCR, EBIR, MD(Res), is a radiologist and the clinical lead of uroradiolgy at King’s College Hospital, London, UK. He completed his doctoral research on the clinical application of contrast-enhanced ultrasound for scrotal pathologies at King’s College London, UK.

Tweet him @DrDean_Huang

Interested in learning more about contrast-enhanced ultrasound? Check out the following posts from the Scan: