Diagnostic ultrasound ( PDFDrive )

872 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
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B
FIG. 23.31 Peripheral Nerve Sheath Tumor. (A) Long-axis image obtained at the site of a palpable mass shows an ovoid, hypoechoic mass
with smooth borders, arising from the ulnar nerve. Note the ulnar nerve enters and exits the mass (arrows). (B) A short-axis image of the forearm
demonstrates the mass in the expected location of the ulnar nerve. Color Doppler shows marked hyperemia within the mass. FCU, Flexor carpi
ulnaris; FDS, lexor digitorum supericialis and profunda.
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B
FIG. 23.32 Sarcoma. (A) A myxoid liposarcoma demonstrates mildly increased through transmission (arrows) due to the myxoid content.
However, the mass is solid, with internal echoes. The supericial border is microlobulated. (B) Color Doppler imaging demonstrates increased blood
low within the mass.
resection of sot tissue sarcoma, ultrasound has been shown to
have acceptable diagnostic accuracy but may miss a small number
of recurrences. Ultrasound could play a complementary role to
MRI in follow-up of these cases. 87,88
FOREIGN BODIES
Embedded sot tissue foreign bodies are a common problem
in both adult and pediatric populations. Whereas some materials,
such as metal and glass, are radiopaque and can be seen on plain
radiographs, other materials such as wood are not detected
radiographically. In these cases, ultrasound is an efective means
for diagnosis. Foreign bodies are typically highly echogenic
and may have posterior acoustic shadowing (Fig. 23. 33). hey
may be surrounded by a hypoechoic halo, representing an
inlammatory reaction 89 or hyperemia on color Doppler imaging.
A large amount of associated luid should prompt consideration
of a secondary abscess.
From a practical standpoint, the patient can usually accurately
direct the sonographer to the area of greatest concern, and
observation of skin entry and/or exit sites is helpful to focus
evaluation. Knowledge of the trajectory of foreign body entry
is particularly helpful in assessment of thin linear objects such
as wooden splinters, because they are oten seen in nonanatomic
oblique planes. Meticulous scanning is needed because small
foreign bodies may be occult to cursory scanning in the hands
and feet, where they may be obscured by adjacent ligaments,
tendons, nerves, and vessels. 90 It is also important to determine
the relationship of the object to these anatomic structures and
to determine if there is associated injury to them. In addition
to the visualization of nonradiopaque foreign bodies, ultrasound
may help guide surgical planning by providing accurate threedimensional
localization of both radiopaque and nonradiopaque
objects, and the overlying skin can be marked preprocedurally
as an aid. Ultrasound can also be used to directly guide foreign
body retrieval with real-time imaging. 91,92
SOFT TISSUE INFECTION
Infection of the skin and subcutaneous sot tissue, cellulitis, is
a common clinical problem, which can be efectively treated
with antibiotics. On ultrasound, the skin and subcutaneous tissues
are thickened and hyperechoic early in the process. Later, there
may be interdigitating reticular strands of hypoechogenicity
representing interstitial inlammatory exudate, 93 also known as
the “cobblestone” appearance (Fig. 23.34).