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Machine Setup, Probe Selection, and Image Orientation
Machine Setup, Probe Selection, and Image Orientation
High-quality neonatal echocardiography begins with appropriate machine setup and calibration to ensure consistency across studies and between operators. Standardized initial settings reduce technical variability and allow the clinician to concentrate on physiology and clinical interpretation rather than repeated adjustments during the examination. Transducer selection is dictated by the infant’s size and the balance required between spatial resolution and depth penetration. Because imaging distances in neonates are short, high-frequency phased-array probes, typically in the 7–12 MHz range, are preferred. These probes provide excellent spatial resolution and have a small footprint that fits easily between narrow intercostal spaces. Although higher frequencies are associated with increased attenuation and reduced penetration, this limitation is rarely problematic in neonatal imaging due to the small size of the heart and thorax.
The foundation of diagnostic neonatal echocardiography lies in a sound understanding of ultrasound physics and the skilled manipulation of machine controls, often referred to as knobology. Image optimization requires a deliberate balance between spatial resolution, which determines the ability to distinguish adjacent structures, and temporal resolution, which allows accurate visualization of rapid cardiac motion. Because ultrasound waves interact with tissues through reflection, scattering, refraction, and attenuation, the operator must actively manage these interactions to produce a faithful representation of cardiac anatomy and function while minimizing artifacts. Optimization begins with adjustment of depth and sector width. Depth should be set to extend only one to two centimetres beyond the structure of interest, ensuring complete visualization without sacrificing frame rate. Narrowing the sector width further improves temporal resolution by reducing the number of scan lines the system must process. Maintaining a high frame rate is particularly important in neonates, where heart rates are fast and myocardial motion is rapid.
Most modern probes allow selection of different frequency presets, often labelled as general, penetration, or resolution modes (on Philips devices). While tissue harmonic imaging is widely used in adult echocardiography to improve image clarity and signal-to-noise ratio, in neonates it can make thin structures such as valve leaflets or septa appear artificially thick and may reduce axial resolution. For this reason, imaging with the fundamental frequency is generally preferred in neonatal echocardiography. Image orientation must also be standardized to avoid anatomic misinterpretation. Neonatal images are commonly displayed with the near field at the bottom of the screen using an up–down inversion, which preserves intuitive spatial relationships. Left–right inversion should never be used, as it disrupts anatomic orientation and can lead to errors such as reversing the relative positions of the aorta and pulmonary artery.
Gain and compensation settings control image brightness but do not improve the signal-to-noise ratio. Overall gain should be adjusted so that background speckling in the blood pool just disappears. Time gain compensation allows selective adjustment of brightness with depth to compensate for signal attenuation, producing a uniformly illuminated image from near to far field. Lateral gain compensation can be used to balance brightness across the image and is especially helpful for defining myocardial borders. Compression controls image contrast; excessive compression produces stark black-and-white images with loss of tissue texture, whereas insufficient compression can blur tissue interfaces. Lateral resolution is optimized by placing the focal zone at the level of the structure of interest, such as the mitral valve or ventricular septum. This narrows the ultrasound beam at that depth and improves discrimination of adjacent structures perpendicular to the beam axis.
Parameters for Echocardiographic Image Optimization
Parameters for Echocardiographic Image Optimization
Doppler Imaging Optimization
Doppler imaging requires additional attention to alignment and scale selection. Color Doppler should be used with the smallest possible color box and positioned precisely over the region of interest to preserve frame rate. The velocity scale, or Nyquist limit, must be matched to the expected flow velocities. Low-velocity flows such as pulmonary venous return require lower scales, whereas high-velocity jets and shunts require higher settings to avoid aliasing and misinterpretation. Spectral Doppler includes pulsed-wave and continuous-wave modalities, each with distinct advantages and limitations. Pulsed-wave Doppler allows precise spatial sampling but is limited by the Nyquist limit and is therefore unsuitable for very high velocities. Continuous-wave Doppler can measure high velocities accurately, which is essential for assessing lesions such as tricuspid regurgitation or restrictive shunts, but it lacks range specificity and records all velocities along the beam path. In all Doppler modes, accurate velocity estimation depends on aligning the ultrasound beam as parallel as possible to blood flow; even small angular deviations can result in significant underestimation of true velocities.
Artifacts and Interpretation Pitfalls
Artifacts arise when the assumptions made by the ultrasound system about sound propagation are violated and must be recognized to avoid diagnostic error. Reverberation artifacts occur when sound waves repeatedly reflect between strong interfaces, creating multiple false echoes or comet-tail patterns. Mirror-image artifacts result from reflection off smooth, highly reflective surfaces such as the diaphragm, producing a duplicate structure deeper than its true location. Side-lobe and beam-width artifacts can cause structures outside the imaging plane to appear within it or can obscure small structures when the beam is wider than the object being imaged. Acoustic shadowing occurs when dense structures such as ribs or vertebrae block the ultrasound beam, creating dark regions distal to the reflector. Several technical pitfalls are common in neonatal studies. Low color Doppler gain can lead to underestimation of valvular regurgitation or shunt flow, while foreshortened views caused by poor probe positioning can result in rounded ventricular apices and inaccurate assessment of chamber size and systolic function. Any unexpected finding should be interrogated in multiple planes and views to distinguish true anatomy from artifact. In neonatal echocardiography, artifacts are errors in image production that occur when the ultrasound machine's assumptions about sound propagation are violated. Recognizing these artifacts is vital for the practitioner to avoid misinterpreting anatomic structures or making incorrect clinical diagnoses.
The following is a comprehensive list of potential artifacts and their explanations:
Reverberation Artifacts: These are generated when sound waves interact with strong reflectors, such as the ribs or pericardium. Instead of a direct path, the waves undergo additional reflections within the tissue before returning to the probe. Because the machine assumes a direct, single path for every echo, these artifacts appear as multiple repetitive images behind the real reflector or as "comet tails".
Side Lobe Artifacts: Ultrasound scanners assume the beam is infinitely thin, but energy is actually focused at the centre of the field with some energy leaking into "side lobes". If these side lobes encounter a very strong reflector outside the primary two-dimensional plane, that object may appear faintly within the main image, potentially mimicking a structure that is not actually there.
Acoustic Shadowing: This occurs when a highly reflective or absorptive structure, such as bone or calcified tissue, transmits or blocks most of the emitted sound waves. This leaves very little residual energy to reach or reflect off deeper structures, resulting in a dark, echo-free area (a "shadow") on the monitor behind the strong reflector.
Mirror Imaging: This artifact displays a duplicate of a real structure, where one image is real and the other is an artifact. It occurs when the sound beam hits a strong, smooth reflector like the diaphragm, which acts as a mirror. The system incorrectly assumes the reflected pulse has travelled in a straight line, placing the duplicate image deeper than the true anatomy.
Beam Width Artifacts: These occur when the ultrasound beam is wider than the specific reflector being imaged. The scanner averages the echogenicity of the reflector with the neighbouring normal tissue; this can cause small solid lesions to disappear or make cystic, fluid-filled structures appear solid.
Refraction Artifacts: Refraction is the bending of the ultrasound beam when it enters a medium with a different propagation speed. Because the machine assumes the beam always travels in a straight line, refraction can cause structures to be displayed in an incorrect anatomical location.
Aliasing (Spectral and Colour Doppler): This is the most common Doppler artifact, occurring when the blood flow velocity exceeds the Nyquist limit (which is half of the pulse repetition frequency). On spectral Doppler, the signal "wraps around" the baseline and appears on the opposite side; in colour Doppler, this is represented by a colour reversal or mosaic pattern where flow toward the probe suddenly appears as flow away from it.
Flash Artifact: This appears as a sudden burst of colour filling the entire colour box, often obscuring the underlying anatomy. It is typically caused by non-cardiac motion, such as the infant’s breathing or movement of the intestines.
Bruit Artifact: This occurs when high-velocity, turbulent blood flow causes the surrounding tissue to vibrate. These vibrations are misinterpreted by the scanner as blood flow, creating "fringe" colour or tissue signals that spread out around the actual jet.
Range Ambiguity: This arises in spectral Doppler when the system cannot determine the exact location of a recorded velocity. This is the primary drawback of continuous-wave Doppler, which records every velocity along the entire length of the beam rather than at a specific depth.
Speckle and Gain Noise: Excessive system gain can amplify weak, stray reflections, creating a noisy "speckled" appearance in blood-filled chambers that should be dark. Conversely, inadequate gain may result in a failure to display real tissue interfaces.
Patient Care and Practical Considerations
Patient comfort and safety are integral to obtaining high-quality neonatal echocardiographic studies. Infants should be settled, swaddled, and positioned comfortably whenever possible. The use of sterile, warmed ultrasound gel minimizes cold stress and reduces infection risk, particularly in extremely preterm or critically ill neonates. Minimal transducer pressure should be applied, especially during subcostal imaging, to avoid provoking vomiting or cardiorespiratory instability.
Targeted views facilitate assessment of indwelling lines and catheters. Inferior vena cava catheters are best visualized in the subcostal long-axis view, while superior vena cava lines are more reliably seen using high parasternal bi-caval or suprasternal short-axis views. Existing electrocardiography leads should be used for gating whenever possible to avoid additional adhesive trauma to fragile neonatal skin. Finally, study limitations such as excessive movement, crying, or high respiratory and oxygen support must be recognized and documented, as these factors directly affect image quality and the confidence of clinical interpretation.
Sliding
Rotating
Tilting / Fanning
Rocking
Compression
Video Modules
Video Modules
Quick overview of the knobology of the Philips Epiq-7C machine that we use at the NeoCardioLab - Montreal Children's Hospital.
Quick overview of the knobology of the Philips Epiq-7C machine that we use at the NeoCardioLab - Montreal Children's Hospital.
NH-TNE Teaching of July 8, 2025 - Knobology
NH-TNE Teaching of July 8, 2025 - Knobology
Knobology en français en direct de la machine
Knobology en français en direct de la machine
Knobology in english live on the machine
Knobology in english live on the machine
Specific information regarding Philips Cardiovascular Systems
Specific information regarding Philips Cardiovascular Systems
On Philips Epiq: Other presets to adjust for image optimization:
2D Opt: Bottom left knob under your touchscreen. It changes the frequency of the transducer. HRes (high frequency, best resolution, less penetration), HGen (mid-frequency, mid-range between your resolution and your frame rate), HPen (low frequency, less resolution, more penetration). Change between these 3 options depending on the image desired. Adjusting the frequency will allow improvement of structure characterization. As such, decreasing the frequency will allow to image deeper structure.
Res/Spd: Second bottom left knob. One control that adjust nearly 40 pre-processing parameters. Try to change between one and an other to take the best image quality that you like. Best practice is to let it at 12 o'clock.
Compress: 3rd bottom left knob. Usually around 50. Put it around 44-48 to optimize coronaries and around 52-56 to see well thin leaflets.
XRES: On the second page of the touchscreen (hit the right arrow, bottom right to change the page). XRES is an image processing algorithm that reduces speckle and enhances contrast resolution. It provides sharper margins and improves border delineation. XRES 1 (smoother image), XRES 5 (coarser image). Default is at 3, so consider putting it at 1 for vessels and 5 in apical if struggling for the visualization of the left ventricular endocardium.
Adjust gain and lateral gain compensation / time gain compensation
Adjust the sector width and depth. Make sure to narrow the scanning area to the structure of interest to increase frame rate capture.
Adjust the focal zone to the structure of interest.
Sur Philips Epiq: Autres préréglages à régler pour l'optimisation de l'image :
Opt 2D : bouton en bas à gauche sous votre écran tactile. Il change la fréquence du transducteur. HRes (haute fréquence, meilleure résolution, moins de pénétration), HGen (moyenne fréquence, milieu de gamme entre votre résolution et votre fréquence d'images), HPen (basse fréquence, moins de résolution, plus de pénétration). Basculez entre ces 3 options en fonction de l'image souhaitée. L'ajustement de la fréquence permettra d'améliorer la caractérisation de la structure. En tant que tel, la diminution de la fréquence permettra d'imager une structure plus profonde.
Res/Spd : Deuxième bouton en bas à gauche. Un contrôle qui ajuste près de 40 paramètres de prétraitement. Essayez de changer entre l'un et l'autre pour prendre la meilleure qualité d'image que vous apprécié. La meilleure pratique est de le laisser à 12 heures.
Compresser : 3ème bouton en bas à gauche. Généralement autour de 50. Mettez-le autour de 44-48 pour optimiser les coronaires et autour de 52-56 pour voir des feuillets des valves.
XRES : Sur la deuxième page de l'écran tactile (appuyez sur la flèche droite, en bas à droite pour changer de page). XRES est un algorithme de traitement d'image qui réduit le grain et améliore la résolution du contraste. Il fournit des marges plus nettes et améliore la délimitation des frontières. XRES 1 (image plus lisse), XRES 5 (image plus grossière). La valeur par défaut est 3, pensez donc à la mettre à 1 pour les vaisseaux et à 5 en apical si vous avez du mal à visualiser l'endocarde ventriculaire gauche.
Ajuster le gain et la compensation de gain latéral/compensation de gain de temps
Réglez la largeur et la profondeur du secteur. Assurez-vous de réduire la zone d'acquisition à la structure d'intérêt pour augmenter la capture de la fréquence d'images.
Ajuster la zone focale à la structure d'intérêt.
EPIC_Control_Surface_QG_20160511_v01.pdfVM156_EPIQ_BreastImagingControls_QG_CA_20160509_v02.pdfSome pearls by views
Some pearls by views
References
References
https://hholdorf.wordpress.com/wp-content/uploads/2015/09/physics-scanner-controls.pdf
BASIC Critical Care Ultrasound. 02 Knobology, Image Optimization and Transducer Manipulation [Video]. YouTube; 2020. Available from: https://www.youtube.com/watch?v=F3zWv9e_W_c
The Echo Lady. 2D IMAGING + Image optimisation! (Echocardiogram) [Video]. YouTube; 2020. Available from: https://www.youtube.com/watch?v=A395yWwG24M
Fazulu H. Knobology 1-A Optimising ECHO Images. Cardiology Lectures DM DNB [Video]. YouTube; 2021 Jul 1. Available from: https://www.youtube.com/watch?v=8M6pAn06S40
Critical Care Echo and Ultrasound (POCUS). Knobology and image optimisation for focused echo [Video]. YouTube; 2021. Available from: https://www.youtube.com/watch?v=U36y8OaGf9E
Mastering & Guidelines in Ultrasound & Echo-Card. Optimizing Image in Ultrasound & Echo 3: Knobology in Epic Ultrasound Machine- Part I [Video]. YouTube; 2020. Available from: https://www.youtube.com/watch?v=fSExLzK5fI0
Mastering & Guidelines in Ultrasound & Echo-Card. Optimizing Image in Ultrasound & Echo 3 Knobology in Epic Part 2: Doppler, M-Mode [Video]. YouTube; 2020. Available from: https://www.youtube.com/watch?v=RAn8E8z8Tks
Shernan SK. Optimizing Two-Dimensional Echocardiographic Imaging. Thoracic Key [Internet]. Available from: https://thoracickey.com/optimizing-two-dimensional-echocardiographic-imaging/
Kamat SS. Physics of Echocardiography, Knobology and Image Optimization. J Acute Care. 2023;2(3):101–109. doi: 10.5005/jp-journals-10089-0046.
European Special Interest Group ‘Neonatologist Performed Echocardiography’ (NPE). NPE Teaching Manual: Ultrasound and tissue interactions. Version 2019. p. 18–27.
Alsaiad AMA. Examination, Image Optimization & Knobology in Transthoracic Echocardiography. In: Basic Echocardiography Physics and Transthoracic Echocardiogram. Springer Nature Singapore Pte Ltd; 2024. p. 101–113.
Groves AM, Singh Y, Dempsey E, Molnar Z, Austin T, El-Khuffash A, de Boode WP. Introduction to neonatologist-performed echocardiography. Pediatr Res. 2018;84(S1):S1–S12. doi: 10.1038/s41390-018-0076-y.
https://www.pocus101.com/ultrasound-machine-basics-knobology-probes-and-modes/
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