Diagnostic ultrasound ( PDFDrive )

CHAPTER 56 Pediatric Interventional Sonography 1943
patient. On the contrary, children tolerate levels of pH, creatinine,
Po 2 , and sedation that might cause major complications in adults.
he pediatric patient is oten quite unconcerned with the details
of the disease and treatment, and all but the sickest patients
simply want to leave the imaging department with the greatest
amount of play and the least amount of anxiety and discomfort
possible. Conversely, the parents are oten more diicult to
manage than the child. Understanding of the diferent needs of
the parents and the child is essential from the beginning of the
interaction.
Personnel and Equipment
Adequate equipment and experienced assistants are essential
for successful and safe pediatric intervention. Although most
interventional radiologists should be able to perform basic
ultrasound-guided procedures on children, some cases are
not appropriate for the inexperienced or occasional operator.
A commitment to careful, graded learning, including the
use of training phantoms, is needed, as is a good knowledge
of regional anatomy or the willingness to learn and
review the relevant anatomy before attempting challenging
procedures.
By its nature, the timing of interventional practice is not always
predictable or convenient, and it is common for the general
ultrasound department to resent calls for borrowing ultrasound
equipment on short notice. Despite the inconvenience, the
interventionist should insist on the best technical ultrasound
equipment available. he ideal situation is to have dedicated
interventional ultrasound equipment housed in the interventional
suite. Some major pediatric radiology departments have moved
the interventional suite to the operating room environment. his
integration of interventional radiology services within the operating
room environment has generally resulted in increased
cooperation between interventional radiologists and surgeons,
especially involving intraoperative ultrasound assistance during
traditional surgical procedures.
GUIDANCE METHODS
Computed tomography (CT) is necessary for some procedures,
especially for procedures involving bone, but in most other cases,
ultrasound-guided access with either ultrasound or luoroscopic
monitoring of wire and catheter placement is ideal (Table 56.1).
Ultrasound can be used in the CT suite to complement a predominantly
CT-guided procedure. Radiation dose to children
undergoing CT procedures has recently aroused signiicant
controversy, so ultrasound can be used to lower the need
for CT. 1
Multimodality Interventional Suites
he recent availability of cone-beam CT sotware installed on
advanced angiography equipment with virtual three-dimensional
(3-D) guidance enables combined complex interventional
procedures involving ultrasound guided access, CT-like 3D
imaging, live guidance graticules superimposed over 3-D images,
and conventional luoroscopy, all in the same interventional
radiology suite. 2
TABLE 56.1 Computed Tomography (CT)
Versus Ultrasound for Interventional
Procedures
Ionizing
radiation
Scan plane
Resolution
Convenience
CT
Radiation dose to
pediatric patients is
an important current
issue in pediatric
imaging, particularly
for interventional
procedures, when
more than one scan
may be needed
Typically limited to
initial axial images
(especially dificult
near the diaphragm)
Excellent, although
lack of fat in
children can limit
visualization
More dificult to
schedule
Magnetic resonance imaging (MRI) guidance in pediatrics
is uncommon. An example of multimodality guidance is shown
in Fig. 56.1.
ULTRASOUND TECHNIQUES
Ultrasound
None
Unlimited, except
by bone or gas
Excellent except
for membranes
in luid
collections
High
Cost High Intermediate
Monitoring By repeat scan; no
real-time ability;
recovery from
kinked wires
dificult
Real time
Gas and
bowel
Excellent, especially
with contrast
Poor
Equipment and Transducers
A selection of transducers is essential. Small patient size and
lack of subcutaneous fat in most children allow use of highfrequency
transducers. Procedures performed around ribs, such
as thoracentesis, are best done with small-footprint sector
transducers. Vascular access procedures are best performed with
a linear high-frequency transducer. Color Doppler is useful for
localization of major blood vessels. Transducers with good nearield
resolution are used for supericial lesions and for initial
accurate placement of local anesthetic on the peritoneum, deep
fascia, or organ capsule.
One Operator Versus Two
It is common for inexperienced operators to require a technologist
or another radiologist to perform the ultrasound scanning. his
should be vigorously discouraged. Although large, simple luid