Volume 11 Issue 1 (February) - Australasian Society for Ultrasound ...

ASUM Ultrasound Bulletin February 2008; 11 (1): 25–29
DIAGNOSTIC ULTRASOUND
Interventional ultrasound – general principles and
applications in gastroenterology
Torben Lorentzen 1 and Christian Nolsøe 2
1
Department of Gastroenterologic Surgery, Copenhagen University Hospital at Herlev, 2 Department of Radiology,
Copenhagen University Hospital at Koege, Denmark.
Correspondence to Torben Lorentzen. Email tlo@dadlnet.dk
Fig. 1a
Equipment in interventional US. 1a Needle guide made of metal is attached to the transducer, which is inside a sterile cover. A large cutting needle
(mounted in the biopsy gun) is inserted in the needle guide that can be adjusted for different sizes of needles and catheters. 1b Ready for a liver
biopsy. The needle will follow the puncture line seen on the monitor, (modelphoto).
Fig. 1b
Introduction
Ultrasound (US) imaging, because it is in real time, is an
unsurpassed imaging guide for interventional procedures. It
is rapid and convenient, all puncture directions are possible
and it allows continuous visualisation of the needle tip during
a needle insertion. There is no ionising radiation and the
equipment is mobile and relatively inexpensive. Because of
these advantages, US and US-guided interventional procedures
have gained widespread use.
Interventional procedures are minimally invasive, less
time consuming and gentle alternatives to, or replacements
for, many surgical procedures and have consequently had a
great impact on the management of numerous diseases. In
this paper, we focus on the general principles of interventional
US and give some examples of diagnostic and therapeutic
applications in gastroenterology.
The typical US examination in gastroenterology includes
abdominal imaging of the liver, gall bladder, pancreas, GItract,
spleen and retroperitoneum. The liver and pancreas
might be examined in more detail with a surgical approach
using intraoperative US (IUS), laparoscopic US (LUS), or
endoscopic US (EUS). Furthermore, ano-rectal diseases and
pelvic fluid collections might be examined with transrectal
or transvaginal US. Both the ‘classic’ abdominal US as
well as the surgically US approach can guide interventional
procedures.
Guidance technique
A needle guide can be attached to the transducer as seen in
Fig. 1a. The needle guides are either sterilised disposable
utensils or reusable devices that need to be sterilised between
procedures. Using a needle guide provides safer control of
the needle during insertion, but at the cost of reduced flexibility
of needle manipulation and limited degree of freedom
regarding direction of puncture.
The transducer produces two-dimensional images of the
scanned object, which is a three-dimensional structure. As
the first step in the interventional procedure, the transducer
is moved over the area of interest until the scanning sector
traverses the target, which is then visualised on the monitor
(Fig. 2). When the needle guide button on the scanner display
is activated, the puncture line appears on the monitor
(Fig. 1b). The transducer is then moved until the puncture
line goes through the target, which implies that a needle
inserted through the attached needle guide will be able to
hit the target.
The point where the needle will penetrate the skin is
marked with ink and local anaesthesia is applied. Then, the
needle guide is mounted on the transducer and, depending
on the size of the device to be inserted, a small skin incision
may be made. The planned intervention can now be
performed. If necessary, consecutive needle passes may be
carried out through the same incision.
ASUM Ultrasound Bulletin 2008 February 11 (1)
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