Radiation Detectors
to significantly degraded energy resolution. The
development and successful use of an improved,
compact detector for this application was report-
ed by Szypryt and colleagues [7], who provided
an early report of the intra-operative use of a
cadmium telluride detector. More recently, the
excision of osteoid osteoma and successful fol-
low-up in 12 patients has been reported [8] and
Wioland and Sergent-Alaoui [9] have reviewed
their experience of 175 radionuclide-guided ex-
cisions; both teams used scintillation detectors.
Parathyroidectomy has been guided with the aid
of a radiation probe, with resection of both ec-
topic parathyroid adenomas and hyperpara-
thyroid tissue localised via their uptake of thal-
lous-201 chloride [10] and more recently
99m
Tc-
labelled sestamibi (MIBI) [11, 12].
Radiolabelled monoclonal antibodies may also
be detected intra-operatively. The technique was
first reported in 1984 by the group led by Martin,
initially identifying occult tumour through detec-
tion of a polyclonal
131
I
anti-CEA antibody in a
patient with colorectal cancer [13]. The technique
has been significantly refined since this time,
using monoclonal antibodies with greater specifi-
city and employing
125
I
as the radiolabel [14–18].
The short range of the low-energy gamma rays
emitted by
125
I
precludes external imaging, but
also acts to eliminate the detection of extraneous
activity from distant sites of uptake. The 60-day
half-life of
125
I
also permits intra-operative detec-
tion after tumour to background activity levels
have dropped to their optimum ratio, many days
after administration of the radiolabelled anti-
body.Other groups have used this approach [19,
20] and the group of Di Carlo et al. have in-
vestigated pharmacological strategies for reduc-
ing the time delay necessary before operation
[21]. With generally less success,
radiolabelled
Next
page
Intra-operative Radiation Detectors
Radiation detectors have been used intra-opera-
tively to identify and localise pathology for
nearly
50
years, and a number of clinical applications are
documented in the published literature.
Clinical Applications
Radiation detection systems were first used intra-
operatively in 1949, when Selverstone and asso-
ciates successfully used narrow-bore Geiger-
Müller needle probes to detect the uptake of
sodium phosphate incorporating the beta-emit-
ting radionuclide phosphorus-32 in a range of
cerebral tumours [1]. The physical characteristics
for
32
P
and other radionuclides discussed in this
section are listed in Table 1.
Harris [2] and subsequently Morris and col-
leagues [3] developed a miniaturised CsI(Tl) scin-
tillation probe to assist in the removal of occult
thyroid cancer through detection of its uptake
of
either iodine-131 or iodine-125. Lennquist
and co-workers have also used this technique to
remove residual tissue at thyroidectomy, success-
fully avoiding the need for postoperative radio-
iodine ablation in more than half of those
patients demonstrating a residual uptake of
iodine [4, 5].
Radiodetection probes have also been used to
ensure the complete resection of osteoid osteoma,
utilising its avidity for technetium-99m labelled
phosphonate tracers. Harvey and Lancaster were
the first to investigate this technique, and they
designed a scintillation detector incorporating a
fibre-optic light guide to aid its miniaturisation
[6]. However, they, and later other workers, found
that this resulted in suboptimal performance due
chapter
3
