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ABDOMINAL ULTRASOUND
Figure 11.2 Testing the alignment of the biopsy guide. The electronic pathway is activated on the image, and the
needle is scanned as it is passed into a jug of water.
Equipment and needles
Figure 11.3
(bottom).
Biopsy needle closed (top) and open
The core of tissue for histological analysis is
obtained with a specially designed needle consisting
of an inner needle with a chamber or recess for
the tissue sample and an outer, cutting needle
which moves over it—the Tru-Cut needle. The
biopsy is obtained in two stages: first the inner
needle is advanced into the tissue, then the outer
cutting sheath is advanced over it and the needle
withdrawn containing the required tissue core
(Fig. 11.3).
The use of a spring-loaded gun to operate these
needles is now commonplace (Fig. 11.4). Such
devices are designed to operate the needle with
one hand; the whole needle is advanced into the
tissue, just in front of the area to be biopsied. By
pressing the spring-loaded control, the inner part
is rapidly advanced into the lesion, followed rapidly
by the cutting sheath over it. These needles can be
obtained in a variety of sizes—generally 14, 16, 18
or, less commonly, 20 gauge. Most focal lesions are
biopsied with a standard 18G needle. As a general
principle, as the needle advances approximately
1.5–2.0 cm during biopsy, it is advisable to position
the needle tip on the edge of a lesion to obtain
a good histological sample as most lesion necrosis
tends to be centrally located.
Such biopsy guns enable the operator to scan
with one hand and biopsy with the other, observing
the needle within the lesion, yielding a high
rate of diagnosis with a single-pass technique 1 and
minimizing post-biopsy complications.