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3 (Color) Doppler US: Theory, Artefacts, Typical Applications inChildhood
55
3.4.2.3 Urinary Bladder 3DUS
Ideal for automatic volume calculations, particularly valuable in bladders with
irregular shape.
Using surface rendering, inner surface information is extracted and displayed
improving depiction of trabeculation, bladder wall/bladder neck pathology, as well
as enabling viewing of ureteral ostium/ostium changes (Fig.3.16).
• 4DUS of the bladder using surface rendering allows performing real-time virtual
cystoscopy.
3.4.2.4 3DUS ofthePaediatric (Female) Genitalia
As shown in adults, 3DUS is particularly valuable for assessment of uterine malformations (e.g. DDx of didelphis/arcuate uterus) (Fig.3.17).
Note This application only can be performed with sufcient diagnostic accuracy
within the rst month of life (fetally stimulated enlarged inner genitalia) or again
after onset of puberty (when uterus, vagina and ovaries are stimulated again—get
reasonable size).
Fig. 3.16 Bladder
3DUS.Three orthogonal
views of urinary bladder
and surface rendered view
(right lower box) of inner
bladder surface
conspicuously depicting
position of the two ureteric
ostia and some bladder
trabeculation in an infant
with recurrent UTI
Fig. 3.17 3DUS of the inner genitalia: uterine
duplication. Coronal reconstructed thick slab and
mucosa-weighted rendered view of two uterine
cavities (baby girl with Wunderlich syndrome)
56
M. Riccabona
3.4.2.5 Musculoskeletal 3DUS Applications
3DUS helpful in depiction of fractures and analysis of fracture shape enabling differentiation of simple versus complex fracture or a suture from a facture:
• Particularly valuable in skull fractures for differentiation of potential victims of
child abuse (Fig.3.18).
3.4.2.6 Small Part 3DUS Applications
Assessment of tumours, neonatal spinal canal 3DUS and assessment of cutaneous
vascular malformation or vessel anomalies by enabling comprehensive overview of
complex and tortuous vessels by aCDS rendering, as well as assessment of nodes,
cysts, lumps and bumps (Fig.3.19). In general, any display and volume measurement of organs or particularly irregularly shaped structures (e.g. various glands) can
be achieved with a higher accuracy as the usual 2DUS volume estimations.
Fig. 3.18 3DUS of skull
fracture. Three orthogonal
views of skull and surface
rendered view (right lower
box) of outer skull bone
surface conspicuously
demonstrating skull
fracture and its shape
ab
Fig. 3.19 Small part 3DUS. (a) Use of 3DUS in suspected rib anomaly—rendered view: due to
the cartilaginous nature of infant rib ends, plain lm could not answer the query, whereas the
reconstructed rendered view after chest wall 3DUS acquisition conspicuously demonstrates the rib
anomaly obviating any other imaging. (b) Thyroid nodule in goitre—thyroid 3DUS (segmented
aCDS acquisition): a box view demonstrates the large nodule with its respective vessels
3 (Color) Doppler US: Theory, Artefacts, Typical Applications inChildhood
Fig. 3.20 Cardiac 3D-/4DUS in neonate.
Colour-coded 4DUS of neonatal heart
demonstrating blood ejection from heart with open
communication (septal defect) between right
pulmonary system and left systemic circulation
57
3.4.2.7 Other Potential 3D-/4DUS Applications
Many other options, e.g. other abdominal/oncologic 3DUS and (neonatal) heart
3D-/4DUS (Fig.3.20):
• However, have not yet been thoroughly evaluated, partially still struggle with
methodical problems, but promise to become more important and interesting in
near future.
3.4.3 Benefits of3D-/4DUS
• Complete coverage of entire structure with improved information for analysis
and DDx, particularly reconstructed planes which are inaccessible for 2DUS but
essential for diagnosis or DDx.
• Comprehensive documentation: ideal for comparison during follow-up as well as
for comparison with other sectional imaging—as any desired plane can be
reconstructed.
• 3DUS allows for accurate volume calculations—even in objects with irregular
shape difcult to assess by 2DUS.
• Using rendering and surface viewing, new diagnostic areas can become available
that have been inaccessible to conventional 2DUS.
• Furthermore these tools enable conspicuous and comprehensive display of structures difcult to demonstrate on standard 2D image.
• aCDS data can be incorporated for anatomic vessel display, helpful particularly
in complex anatomy or pathology (see Fig.3.5).
• Superior data for medical-legal issues as well as for image analysis, counseling,
second opinion consultations or teaching and training, as all the information are
present in data set and can be retrieved whenever needed (without need of patient
being present).
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M. Riccabona
3.4.4 Restrictions of3D-/4DUS
• Restricted resolution—particularly in reconstructed plane. Presently limits
3DUS, particularly in small structures.
• Very few/no dedicated paediatric transducers available for all applications (e.g.
brain 3DUS).
• Handling of often clumsy transducers may be difcult particularly in noncooperative patients causing motion artefacts and image deterioration.
• At present directional Doppler information cannot be included in 3D data: ow
information cannot be incorporated.
• Time necessary for postprocessing/reading, however, at benet of potentially
shorter investigation at patient (i.e. acquiring data set)—shortening investigation
at patient’s bedside.
• Hardware and viewing facility demands—may also increase costs of US device
(particularly cumbersome as long as no reimbursement established for 3DUS).
3.4.5 Potential Future Paediatric 3DUS Applications
Besides increasing use of 4DUS for neonatal echocardiography, some other aspects
on horizon or already introduced recently:
• Combining 3D/4DUS with ce-US/ce-VUS (already introduced).
• Using 4DUS for functional assessment.
• Combining 4DUS with multidirectional US-elastography throughout entire
imaging eld and all planes/directions.
• Interventional 4DUS (already introduced and reported some time ago).
• Image fusion [3DUS information combined with information retrieved from
other sectional imaging (e.g. 4DUS-based intraoperative/biopsy guidance)]
(this biopsy technique has been introduced by several vendors recently).
Contrast-Enhanced US, andUltrasound
Elastography inChildhood
M.Riccabona andH.J.Mentzel
4.1 Contrast-Enhanced Ultrasound (ce-US)
4.1.1 Basics
UCA are materials that can be applied either intravenously or into cavities that
enhance reection, improve visualisation/depiction of certain areas/structures (distribute purely intravascular/intraluminal—whereas contrast agents in CT or MRI
also go to the interstitium). When observing these changes over time, similar perfusion and enhancement patterns can be observed as in contrast-enhanced CT or
MRI—improves not only lesion detection but also differentiation; enables improved
functional imaging.
Many different UCA: all based on some microgas bubbles (air, Peruoropropane,
Peruorobutane, Sulfurhexauoride …) attached to carrier molecule, stabilised by
external capsule. Stabilising shell—usually palmitic acid. Carrier molecule was
galactose (Levovist, Bayer-Schering—not on the market any longer), and now is
either protein (Optison, GE Healthcare) or lipid (SonoVue/Lumason, Bracco;
Denity, Lantheus Medical Imaging; Sonazoid, Daiichi Sankyo).
Modern UCA are relatively stable within blood, small enough to pass capillaries
(about size of erythrocyte). New agents with improved stability and increased signal
signature are being developed. Can also be administered into any other cavity (e.g.,
collecting system or bladder, peritoneum, pleural space, abscesses and collections).
4
M. Riccabona (*)
Department of Radiology, Division of Pediatric Radiology, Medical University Graz
and University Hospital Graz, Graz, Austria
e-mail: michael.riccabona@medunigraz.at
H. J. Mentzel
Section of Pediatric Radiology, Institute of Diagnostic and Interventional Radiology,
University Hospital Jena, Jena, Germany
e-mail: Hans-Joachim.Mentzel@med.uni-jena.de
© Springer Nature Switzerland AG 2020
M. Riccabona (ed.), Pediatric Ultrasound,
https://doi.org/10.1007/978-3-030-47910-7_4
59
60
M. Riccabona and H. J. Mentzel
Potential risks of UCA: based on their relatively high osmolarity as well as on
chemical entity with specic reactions:
• Levovist® was contraindicated in galactosemia.
• Proteins and lipids can cause early and late anaphylactoid reactions.
• High osmolarity can cause systemic and local vascular reactions.
• Encapsulating substances usually do not cause signicant problems in cavities.
Note In IV. applications small risk of even severe anaphylactoid reactions exists
even in children–be prepared.
In general UCA have negligible side effects, particularly when compared with
CA commonly used for other imaging modalities such as CT, MR and catheter
angiography.
Note UCA particles are cavitation seeds! Thus potential risk of cavitation and
cavitation- induced side effects increases, should be specically considered when
applying these agents to risky areas (e.g., neonatal brain, bowel wall and testis).
Intrinsically, low MI techniques using very low sound pressure are preferable, not
only for reducing cavitation risks but also as they spare UCA/enable longer observation period at lower UCA dose.
4.1.2 ce-US Applications-General Remarks
Many different applications established also applicable to children—though most
mainly applied to adults (due to restricted availability/lack of approval for paediatric
use). Main basic approaches:
• Detection (of lesions or pathology …): US technique optimised towards visualising structures rather than contrast dynamics/enhancement patterns.
Sometimes UCA used to enable sonographic depiction of structures or phenomena impossible to visualise on baseline US, as insufcient penetration or
increased scattering impairs proper grey scale or CDS analysis. For example,
transcranial Doppler sonography may be cumbersome in older children and adolescents: with UCA vessels more easily depictable, duplex gate placeable properly, angle correction performed correctly—thus assessment signicantly
improved. Same applies to visualisation of vascular structures in deep body compartments or in difcult scanning conditions particularly in obese patients, with
vessels at poor insonation angle, and thus also helpful in post-transplant
assessment.
• Improved visualisation of vascular structures or other hollow organs/cavities that
can be lled with UCA (Fig.4.1).
• Lesion characterisation: Functional viewing focuses on perfusion/enhancement
patterns: tries to evaluate contrast behaviour within targeted structure over time
4 Contrast-Enhanced US, andUltrasound Elastography inChildhood
Fig. 4.1 Malposition of drain after PCN—intracavitary ce-US.Double/split image display of kidney after instillation of diluted UCA (1%) into a nephrostomy drain for assessment of drain function and position: echogenic UCA not only seen in central collecting system on the left hand
contrast-weighted image, but also scattered around kidney indicating either rupture/injury to collecting system or malposition of some drain side holes causing pararenal UCA extravasation
61
analysing inow, uptake and washout similar to contrast enhancement with other
imaging techniques. In general same rules apply as for ce-CT or -MRI.Observing
different arterial, parenchymal and venous phase-enhancement patterns as well
as late phase imaging improves not only lesion detection but also lesion characterisation. For this technique proper UCA application and potentially intermittent complete UCA destruction within targeted area (achievable, e.g., by single
strong signal burst) allowing for reperfusion assessment necessary.
Note UCA remains purely intravascular, except for liver sinusoids or damaged vas-
cular wall.
• Further details described in respective chapters with individual applications.
4.1.3 Contrast-Enhanced Voiding Urosonography (ce-VUS)
Also known as sonographic VCU(G)/ce-MUS (micturition urosonography)/ceMCS (micturition cystosonography)
• Allows reliable assessment for vesicoureteral reux (VUR) by US.
• Importance of VUR/VUR detection decreasing still remains common/important
in infants, particularly those with congenital urinary tract malformations and
recurrent or upper febrile urinary tract infection (UTI) with potential renal
scarring.
• Conventionally VUR assessment performed by radiographic voiding cystoureterography (VCUG) which carries signicant radiation burden. Thus, increas-
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M. Riccabona and H. J. Mentzel
ingly ce-VUS promoted—presently recommended in Europe at least as primary
investigation in girls, in screening conditions and for follow-up investigations
(EFSUMB recommendation, recently FDA and EMA approved this application
in childhood).
• Conventional uoroscopic VCUG (still?) considered and indicated for preoperative anatomic assessment, assessment of diverticula/urethral and complex urogenital pathology (e.g., male urethra (e.g., urethral valve or folds, strictures …),
stula tracts, or cloacal malformation spectrum) (Table4.1).
Technique (ESUR/ESPR recommendation—see Pediatr Radiol 2008, update 2014)
• Initial thorough US of entire (genito-)urinary tract.
• Bladder catheterised (use, e.g., nasogastral tube in infants, catheter not blocked)
and emptied; urine sample taken to assure absence of infection.
• Thereafter bladder lled by normal warmed saline drip infusion from plastic
containers at physiological lling pressure levels (<50cm above bladder level)
until micturition.
• Contrast application strategies vary: some apply UCA rst (0.1ml SonoVue/
Lumason—according to manufacturer), others apply UCA intermittent with
Table 4.1 ce-VUS/grading of VUR
Adapted from Darge etal. (2002) EJR
VUR grades dened as with conventional uoroscopic voiding cystourethrography; additionally
(as US visualises also non-reuxing systems) “a” is added for non-dilated, “b” for dilated systems:
this gives a scale from VUR 0°a/b to VUR V° a/b
4 Contrast-Enhanced US, andUltrasound Elastography inChildhood
63
saline infusion (at 25, 50, 100% of estimated bladder volume), others mix UCA
into saline plastic container (create a 0.1—2.5% solution) for the UCA infusion
(as done in VCUG)-my preferred application.
• Constant alternating US monitoring of bladder, retrovesical space (distal ureters)
and both kidneys performed—to depict potential reux of echogenic UCA into
ureters/renal collecting system (Fig.4.2).
• If UCA arrives in renal pelvis look for ureter (elongation, kinking, width, peristalsis …) and document (image, clip): evaluation of ureter necessary for grading.
• When bladder lled: voiding attempted in whichever position patient accepts.
• During rst voiding, US of bladder, retrovesical space and kidneys repeated—
with post-void assessment of residual urine (volume measurement!); check for
potentially reuxed material in renal collecting system (Fig.4.3a). Drainage of
reuxed material into bladder should also be noted.
• Potentially use a second dedicated ling cycle and voiding for assessing urethra
(using a perineal approach).
Note During voiding (period with maximum intravesical pressures) thorough eval-
uation also of medullary areas should be attempted to depict intrarenal reux (in
patients who exhibit grade III reux or higher) (Fig.4.4).
• Particularly in neonates and infants, cyclic lling, (e.g., three attempts) should be
performed with repetitive UCA application in order to not only improve VUR
detection but also to enable (trans)perineal urethra assessment during voiding on
a dedicated cycle (Fig.4.3b).
• After investigation assess images thoroughly; VUR grading performed according to proposed grading scale (adopted from established international VCUG
VUR classication) (Table4.1).
Note ce-VUS cannot only show/detect VUR, measure residual volume and assess
drainage dynamics of reuxed material; it also may depict intrarenal reux, assess
renal parenchyma as well as potentially dilated non-reuxing systems and reveal
information on urethra.
Fig. 4.2 VUR III° on
ce-VUS: echogenic
bubbles reux during low
pressure lling phase (low
pressure VUR) into straight
and only slightly dilated
ureter (U) up into the
non-dilated pelvi- calyceal
system—with slightly
clubbed calices
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M. Riccabona and H. J. Mentzel
Fig. 4.3 ce-VUS: double/split image display—contrast-weighted image to the left in (a, b) and right
in (c). (a) UCA lled urinary bladder with echogenic UCA in dilated right distal ureter retrovesically
(+ +). (b) Echogenic UCA in renal collecting system indicating dilating high-grade VUR into clubbed
calices. (c) Perineal view during voiding during ce-VUS: contrast-lled normal urethra, but reux of
echogenic UCA into non-dilated vagina without stula (baby girl with labial synechia)
Fig. 4.4 Intrarenal reux on ce-VUS:
note some echogenic bubbles (arrow)
beyond borders of somewhat clubbed
calices (i.e., in distal medullary tubuli) in
a boy with VUR III-IV°