A prototype opto-nuclear probe for combined radio- and fluorescence tracing of the sentinel node

Recent developments in the field of image-guided surgery have resulted in the
introduction of fluorescent tracers into the clinic. For optical sentinel node
identification, the near-infrared fluorescence tracer indocyanine green (ICG)
was introduced. However, it does not allow for preoperative sentinel node
mapping; the limited tissue penetration of the fluorescence signal prohibits
this. With the introduction of a hybrid tracer, in which ICG is coupled to the
conventional radiocolloid 99mTc-nanocolloid, our group showed that both
preoperative sentinel node mapping and fluorescence sentinel node
identification is possible with a single tracer.
To surgically detect the radioactive and the fluorescent signal,
intraoperatively generally a gamma probe (detection radioactive signal) and a
fluorescence camera (detection fluorescent signal) are used for sentinel node
identification. To further improve these logistics, the company Eurorad
developed a prototype opto-nuclear probe that is able to detect both the
radioactive and the fluorescent signal. This way, it becomes possible to detect
hybrid, combined radioactive and near-infrared fluorescent, tracers using a
single imaging modality.

Primary objective:
- Determination of the sensitivity and specificity of the open-procedure
opto-nuclear probe for sentinel node(s) identification using the combination of
radio- and fluorescence tracing. Obtained results will be compared to those
obtained using the conventional method(s);
- Determination of the sensitivity and specificity of the laparoscopic
opto-nuclear probe for sentinel node(s) identification using the combination of
radio- and fluorescence tracing. Obtained results will be compared to those
obtained using the conventional method(s).

Secondary objective:
- Identification of (tumor positive) sentinel node(s) using the opto-nuclear
probe for open procedures;
- Identification of (tumor positive) sentinel node(s) using the opto-nuclear
probe for laparoscopic procedures;
- Obtaining the CE-mark for the opto-nuclear probe for open procedures;
- Obtaining the CE-mark for the opto-nuclear probe for laparoscopic procedures.

30 Patients will be prospectively included in this study. The number and
location of the sentinel node(s) will be determined following the hybrid tracer
injection and preoperative imaging (current routine). Intraoperatively, a
prototype opto-nuclear probe will be used for sentinel node identification.
Findings of this prototype will be compared to that of the conventional
standards (gamma camera and fluorescence camera).

According to the current standard, on the afternoon prior to, or on the morning
of surgery, ICG-99mTc-nanocolloid will be injected peritumorally sub- or
intracutaneously (patients with prostate cancer will be injected
intraprostatically). Lymphoscintigrams and SPECT/CT imaging will be performed
to determine the number and location of the sentinel node(s).
Sentinel node biopsy will be performed after general or regional anesthesia
using the opto-nuclear probe. Firstly, sentinel nodes will be pursued via their
radioactive signature. After localizing the sentinel node, the mode of the
opto-nuclear probe will be switched to the fluorescence setting. Thereafter,
fluorescence tracing to the sentinel node will be performed. After localization
using the opto-nuclear probe, the conventional methods (gamma camera and
fluorescence camera) will be used to evaluate the accuracy.
For each removed sentinel node, the gamma probe status (amount of radioactivity
in the node) and the fluorescence status (amount of fluorescence in the node)
will be documented. Sentinel nodes will be assessed following the standard
sentinel node protocol at the pathology department.

Ultimately the proposed research will lead to the intraoperative use of one
modality that allows for combined gamma- and fluorescence tracing instead of
the need of various modalities. This may lead to improved logistics and a
reduced operation time.

Due to the proposed research, patients will be kept under anesthesia for an
extra 10-15 minutes.

Risk-analysis revealed no (in)direct risks for the intraoperative use of the
opto-nuclear probe.