Advanced Ultrasound Techniques for Pediatric Imaging

Abstract

Ultrasound has become a useful tool in the workup of pediatric patients because of the highly convenient, cost-effective, and safe nature of the examination. With rapid advancements in anatomic and functional ultrasound techniques over the recent years, the diagnostic and interventional utility of ultrasound has risen tremendously. Advanced ultrasound techniques constitute a suite of new technologies that employ microbubbles to provide contrast and enhance flow visualization, elastography to measure tissue stiffness, ultrafast Doppler to deliver high spatiotemporal resolution of flow, three- and four-dimensional technique to generate accurate spatiotemporal representation of anatomy, and high-frequency imaging to delineate anatomic structures at a resolution down to 30 μm. Application of these techniques can enhance the diagnosis of organ injury, viable tumor, and vascular pathologies at bedside. This has significant clinical implications in pediatric patients who are not easy candidates for lengthy MRI or radiation-requiring examination, and are also in need of a highly sensitive bedside technique for therapeutic guidance. To best use the currently available, advanced ultrasound techniques for pediatric patients, it is necessary to understand the diagnostic utility of each technique. In this review, we will educate the readers of emerging ultrasound techniques and their respective clinical applications.

Trial registration: ClinicalTrials.gov NCT03549507 NCT03549520.

Conflict of interest statement

POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

Copyright © 2019 by the American Academy of Pediatrics.

Figures

FIGURE 1

A large liver hemangioma shown with grayscale ultrasound, CEUS, and MRI, and CEUS images demonstrating centripetal enhancement over time. A, Grayscale ultrasound image of a hemangioma on the initial scan 8 months before the CEUS (C–G) and MRI (B) acquisition. B, Coronal, fat-saturated contrast-enhanced MRI image obtained a few days after the CEUS scan showing a large liver hemangioma with irregular peripheral rim enhancement. C, CEUS image of the lesion (white arrowheads) shown in contrast mode (left) and grayscale mode (right) before microbubble administration. The image is dark, as expected, before microbubble administration on contrast mode. Note the irregular streaks of bright signals within the lesion in the absence of microbubbles, likely due to internal calcifications. D, CEUS image of the lesion is shown at 10 seconds after intravenous microbubble administration. E, CEUS image of the lesion is shown at 12 seconds after administration. F, CEUS image of the lesion is shown at 15 seconds after administration. G, CEUS image of the lesion is shown at 95 seconds after administration.

FIGURE 2

CEUS of pelvic osteosarcoma in a 13-year-old boy was obtained for biopsy guidance. A, Grayscale ultrasound of pelvic osteosarcoma (short white arrows) of heterogeneous echogenicity reveals bone destruction, (long white arrows) as evidenced by a disruption of the echogenic line representing the cortex of the adjacent ilium. B, CEUS of pelvic osteosarcoma (short white arrows) at 14 seconds after contrast administration with a visible large region of necrosis (red circumscribed area) and enhancing tumor tissue on the periphery.

FIGURE 3

CEUS of the nephroblastoma in a 3-year-old boy extending into the right atrium and inferior vena cava was obtained before and after therapy to assess for treatment response. A, Transverse grayscale ultrasound of the nephroblastoma in the right atrium revealing solid cystic echotexture (arrowheads) and extending into the inferior vena cava (white arrows). B, Sagittal grayscale ultrasound revealing extension of the tumor thrombus from the inferior vena cava into the right atrium (white arrows). C, CEUS of the vascularized tumor thrombus in the inferior vena cava (black arrows) before treatment is shown. D, CEUS of the tumor thrombus in the inferior vena cava after 2 cycles of chemotherapy revealing marked decreased vascularization and diameter (black arrows).

FIGURE 4

CEUS images of brain and bowel perfusion are shown. A, Midcoronal brain CEUS image of a normal 1-month-old boy obtained at 15 seconds after microbubble administration revealing relative hyperperfusion to the central gray nuclei compared with the remainder of the brain, which is expected for that age. Normal-sized ventricles and brain volume for age are seen. B, A midcoronal brain CEUS image of a 10-month-old girl after cardiac arrest status post extracorpreal membrane oxygenation. Midcoronal brain CEUS obtained15 seconds after microbubble administration reveals marked increased perfusion to the cortical and subcortical gray and white matter, which is not typically seen in normal neonates and infants. Note also the hyperperfusion to the central gray nuclei, which is slightly higher than expected for that age. C, A midcoronal brain CEUS image of the same 10-month-old girl obtained 1 week after the examination obtained in (B), with the image acquired at 15 seconds after microbubble administration. Compared with the previous brain CEUS examination (B), significant overall decreased perfusion to the brain is noted, likely due to evolving injury, compared with the normal brain CEUS (A). Less avid perfusion to the central gray nuclei and cortex is demonstrated, as evidenced on the time intensity curve analysis (E). D, Midcoronal brain CEUS image of a 6-month-old boy 3 hours after cardiac arrest of unknown etiology reveals a near absent brain perfusion and to-and-fro flow in the avidly enhancing extracranial vessels. Note that the images (A, B, and D) were obtained with an EPIQ scanner (Philips Healthcare, Bothell, WA) and C5-1 transducer with settings of 12 Hz and a mechanical index of 0.06. Image (C) was obtained with Aplio i800 (Toshiba Medical Systems Corp, Tokyo, Japan) and an i8-C1 transducer with settings of 9 Hz and a mechanical index of 0.06. E, Normalized time intensity curve graph of the wash in of microbubbles into the brain in patients (A–D), with y-axes representing changes in signal intensity (decibels) and x-axes representing time in seconds. Note the marked hyperperfusion in the patient (B) and absent perfusion in near brain death (D). F, Bowel CEUS of a 39-day-old, formerly premature girl with necrotizing enterocolitis reveals a hyperemic bowel segment (white arrowheads). G, A bowel CEUS of a 1-day-old, formerly premature girl found to have complete bowel ischemia with no enhancement of the bowel and surrounding mesentery (white arrowheads), likely due to prenatal insult.

FIGURE 5

ceVUS images are shown. A, Side by side sagittal grayscale and corresponding ceVUS image of the right kidney (white arrows) of a 19-month-old boy revealing grade 2 reflux into the renal pelvis (white arrowheads). B, Sagittal ceVUS image of the right kidney (white arrows) with grade 4 reflux into the dilated renal pelvis and calyces (white arrowheads) in a 16-month-old boy. C, Microbubble-filled tortuous megaureter (arrowheads) and bladder (white arrows) in a 3-week-old boy. D, Sagittal ceVUS image of the microbubble-filled urinary bladder (white arrows) and urethra (white arrowheads) in an 8-month-old boy during the voiding phase.

FIGURE 6

Shear-wave and strain elastography images are shown. A, A rectangular cursor is placed in the cortex of the brain of a normal neonate on a sagittal plane for shear-wave elastography measurement, here shown as 1.08 ± 0.26 m/s. B, Similar shear-wave elastography measurement of the periventricular gray-white matter in an infant after anoxic brain injury reveals a markedly elevated elastography measurement of 3.17 ± 0.26 m/s. C, A solid, isoechoic thyroid nodule depicted on grayscale ultrasound (left) and strain elastography (right), with the strain elastography revealing mild increased stiffness as noted by the green color (blue noting soft and red noting hard). D, A normal testis shown in grayscale ultrasound (left) and strain elastography mode (right) reveals slightly stiffer tissue (this time denoted by blue/green) close to the echogenic band of connective tissue across the testis, so-called mediastinum testis, compared with the adjacent softer tissue (red). Note that depending on the system settings, color representation of tissue stiffness may differ.

FIGURE 7

UfD images of the normal neonatal brain are shown. A, Ultrafast power Doppler images of the neonatal brain acquired through the anterior fontanel from left to right: coronal view, tilted parasagittal view, parasagittal view. B, Directional power Doppler images based on the speed information from left to right: medial sagittal view revealing venous network around lateral ventricle, parasagittal view revealing small thalamic and cortical arterioles and venules, and transtemporal transverse view through mastoid fontanel for imaging the circle of Willis and cerebellum. C, Resistivity mapping based on UfD data. The RI in big arteries is between 0.8 and 1 (left and center image), whereas the RI in small and veins are lower at ∼0.6 and

FIGURE 8

A representative image revealing the 3D reconstruction and quantification of the brain ventricular volume. Dotted lines trace the borders of the mildly enlarged third and fourth ventricles in sagittal (top left), axial (bottom left), and coronal planes (top right) for 3D reconstruction (bottom right). The calculated ventricular volume (red) is shown at the bottom. COR, coronal.

FIGURE 9

The nail plate of the distal phalanx of the second digit was imaged with a high-resolution ultrasound scanner by using a 40 MHz transducer. Shown is the picture diagram of the distal aspect of the second digit (B), with the magnification box noting the region of ultrasound evaluation. Annotated on the corresponding grayscale image (A) are the nail plate of the distal phalanx of the second digit (red arrows), nail bed with germinal matrix (between white arrows), eponychium (cuticle) (black arrow), and vessels supplying the nail unit (inside white box).

FIGURE 10

Small parts imaged with a high-resolution ultrasound scanner. A, A 50-MHz transducer was used to image the right median nerve in the transverse plane (white arrows) and the numerous fascicles visible within the nerve. B, A 50-MHz transducer was used to image the wall of the superficial palmar arch artery with intima-media (white arrows). C, A 30-MHz transducer was used to image the dilated superficial vein of the lower extremity with the valves (white arrows) and debris in the folds of valves preventing full opening of the valves (red arrows). D, A 50-MHz transducer was used to image the inner oral cavity sublingual glands (white arrows) and the mucous membrane (between red arrows).