monoclonal antibodies (predominantly anti-CEA
antibodies) optimised for external imaging by
chelation to indium-111 have been evaluated
intra-operatively, primarily for the investigation
of colorectal cancer [22–26] and medullary thy-
roid cancer [27]. More recently monoclonal anti-
bodies labelled with
99m
Tc have also b ee n de te ct -
ed intra-operatively in ovarian cancer [28] and in
colorectal carcinoma [29].
Neuroendocrine tumours expressing somato-
statin receptors demonstrate uptake of radiola-
belled forms of the somatostatin analogue oct-
reotide [30] and have also been detected intra-
operatively using these tracers. Both Wängberg
[31] and Öhrvall and co-workers [32] have report-
ed the successful use of
111
In-labelled DTPA-
D
-Phe
1
-octreotide to detect a mixed group of
predominantly abdominal cancers, and the same
tracer has also been used to localise occult
tumour in recurrent medullary thyroid carci-
noma [33].
125
I-Tyr
3
-octreotide has been used by
Schirmer et al. to identify gastroenteropancreatic
tumours [34] and later by Martinez and collea-
gues to detect occult neuroblastoma [35]. Adams
et al. have used both
111
In-labelled DTPA-
D
-Phe
1
-
octreotide and
99m
Tc (V)-dimercaptosuccinic acid
(DMSA) to localise medullary thyroid carcinoma
and gastroenteropancreatic tumours [36].
Metaiodobenzylguanidine (mIBG) has been
developed as a tracer to target neural crest
tumours [37] and has also been used intra-ope-
ratively in both
125
I- and
123
I-labelled forms to
localise neuroblastoma, most notably in a recent
series of 58 patients by Martelli and group [38].
Intra-operative Detector Design
To det ec t a sentinel node containing
radiolabelled
colloid both reliably and safely one requires a
radiation detector designed for intra-operative
use, and optimised for the application (Fig. 1).
Using such a probe, the node must be detectable
both transcutaneously and within the exposed
surgical field by virtue of its radioactivity.
The system is required to perform reliably
under surgical conditions, and the detector itself
must demonstrate good stability over its expected
lifetime. In considering the design features of
such a probe, fundamental issues must be addres-
chapter
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