Delivery of the Radiopharmaceutical
Interestingly technology is evolving here as well.
A new approach to the delivery of tracer is the use
of the J-Tip Needle Free Injector (National Medical
Products Inc., USA). We have experimented with
this device since it clearly presents a major advan-
tage from the point of view of patient acceptance.If
its use proves successful, reproducibility studies,
which are still vital for improved understanding of
the varying patterns of lymphatic flow, will be
significantly facilitated, and the whole procedure
will be rendered still less invasive.
The device which we have used is made of an
almost standard syringe and plunger system, but
at the proximal end of the device a small capsule of
an expanding gas can be activated easily via a pres-
sure point on the syringe outer layer such that the
plunger is driven downwards by the rapid expan-
sion of this gas. At high speed, the particles are
delivered intradermally and with almost no pain
to the patient. Studies are in progress to investigate
the dispersion and the depth of delivery achieved
with such devices, but interest is already extensive
as judged by the achieved interaction with the
pharmaceutical industry. An example of such a
device is shown in Fig. 2.
Intra-operative Histological Diagnosis
At present, one of the limiting factors in the wider
application of the sentinel node technique is the
lack of a fast and reliable method of histological
diagnosis. The false-negative rate of standard fro-
zen section is unacceptably high, and this tech-
nique cannot be relied upon for routine intra-
operative use. The technique of serial sectioning
at 15 levels and standard immunohistochemical
staining with cytokeratin markers, described by
Ve ronesi et al. [1], has an acceptable accuracy but
the significant increase in the operating time is a
major drawback which renders its routine use
impractical for most institutions.
The development of rapid immunostaining
methods for frozen sections by Chilosi et al.is pro-
mising. Microwave irradiation is used to speed
immunohistochemical analysis using “enhanced
polymer one-step staining” (EPOS). The overall
nisms of uptake which mainly reflect trapping and
phagocytosis of labelled particles. In the next few
years it will be necessary to have properly register-
ed radiopharmaceuticals for the specific purpose
of sentinel node detection. At present there are
none.All of the relevant tracers in current use were
developed years ago for the imaging of the reti-
culoendothelial system.
Significant batch to batch variations in particle
size occur. This problem will be solved in the
coming months. It is, however, uncertain whether
the industry is prepared to develop an entirely new
tracer for the sole purpose of sentinel node detec-
tion in view of the costs associated not just with
the development process but also with the docu-
mentation/registration process now required by
the various licensing authorities. Were it not for
cost considerations,technology would be available
for much improved tracers.
In the academic environment groups will con-
tinue to look at the development of tracers which
take advantage of functional properties of the
lymph nodes. Examples are tracers with specific
receptor-associated uptake (Fc receptors or other
small peptide-mediated lymph node uptake),
some form of metabolic-mediated uptake (it is
known that lymph nodes take up tracers such
as labelled glucose) or antibody-mediated uptake
(a number of possibilities have been and are
being explored and described, often under the
designation of radio-immunoguided detection/
chapter
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Fig. 1.
Optical biopsy of the sentinel node
