Preliminary Experience with the NirisTM Optical Coherence Tomography (OCT) System during Laparoscopic and Robotic Prostatectomy

1
Preliminary Experience with the NirisTM Optical
Coherence Tomography (OCT) System during
Laparoscopic and Robotic Prostatectomy
VP1-24

• Monish Aron, Jihad H. Kaouk, Nicholas J. Hegarty,
  Jose Roberto Colombo Jr, Georges-Pascal Haber,
  Benjamin I. Chung, Ming Zhou, Inderbir S. Gill
• Section of Laparoscopic and Robotic Surgery,
  Glickman Urological Institute, Cleveland Clinic
  Foundation, Cleveland, Ohio

We report our preliminary experience with the use
of the Niris Imaging System (Imalux
Corpopration, Cleveland, OH) for tissue mapping
and identifying the NVB during LRP. Between
11/05 and 3/06, 24 patients undergoing LRP were
enrolled in this study. The operative procedure
was carried out in the standard fashion using a
transperitoneal approach. Once the bladder was
taken down and the prostate mobilized, the
NirisTM imaging system was deployed. The FDA
approved NirisTM system (Fig 1) provides a
portable OCT imaging system, using a probe to
direct the near-infrared light to the patient's
tissue.The light is backscattered from the
patient's tissue, collected by the probe's fiber
, and combined with a reference signal, to
produce a high spatial resolution image of the
tissue microstructure. It acquires real-time
images with 200 x 200 pixels, 15-µm depth
resolution in free space (11 µm in tissue), and
25 µm lateral resolution. A universal reusable
8F NirisTM probe (2.7 mm outer diameter) was used
through a 5-mm laparoscopic port for in-vivo
image acquisition, and directly on the specimens
for ex-vivo image acquisition. To minimize
gas-leak during deployment of the OCT probe, this
can be passed through a laparoscopic suction
cannula, or through a piece of paraffin gauze
placed over the outer end of the laparoscopic
port. In each patient, in-vivo images were
obtained to determine the image characteristics
of NVB, adipose tissue, prostate capsule, and
endopelvic fascia. The NVB was imaged again
in-vivo, after the prostate was excised.
Ex-vivo images were obtained from specific
locations on the prostate surface to look for
presence or absence of NVB and correlated with
the surgeons assessment of the adequacy of nerve
sparing. The image characteristics were
compared with the surgeons independent visual
assessment of the type of tissue being imaged, as
well as with focused histopathology, where
available.
More than 300 OCT images were obtained from 24
patients. These images detailed the
microstructure of tissues including endopelvic
fascia, prostate capsule, NVB, fat, lateral
pedicles, and lymphatics. Ex-vivo imaging was
performed of prostatectomy specimens after
nerve-sparing and non nerve-sparing resections.
OCT images of these specimens were obtained by
personnel who were not aware whether the NVB were
spared or not. The OCT images from the non
nerve-sparing prostatectomy specimens were able
to demonstrate the presence of NVB on the
posterolateral aspect of the gland. Images from
specimens where nerve sparing had been performed
failed to demonstrate the NVB, and instead showed
the dense fibrous structure of the prostate
capsule. OCT images were found to independently
correlate with the surgeons subjective
impression of the tissue being imaged.
Moreover, in 4 patients, the exact areas of the
prostatectomy specimen from which OCT images were
captured were marked with different sutures and a
comparison with parallel histology performed.
Pathological examination suggests that OCT can
potentially help to identify NVB and prostate
capsule during LRP.
RESULTS
MATERIALS METHODS
Introduction To evaluate the feasibility of high
resolution optical coherence tomography (OCT) in
the identification of neurovascular bundles (NVB)
during laparoscopic and robotic radical
prostatectomy (LRP). Materials and methods
Between 11/05 and 3/06, 24 patients undergoing
transperitoneal laparoscopic or robotic radical
prostatectomy were enrolled in this study. Once
the bladder was taken down and the prostate
mobilized, the NirisTM imaging system was
deployed. In each patient, in-vivo images were
obtained to determine the image characteristics
of NVB, adipose tissue, prostate capsule, and
endopelvic fascia. The NVB was imaged again
in-vivo, after the prostate was excised. Ex-vivo
images were obtained from the prostate surface to
look for presence or absence of NVB and correlate
with the surgeons assessment of the adequacy of
nerve sparing. Results From 24 patients, we
obtained more than 300 OCT images of tissue
structures including endopelvic fascia, prostate
capsule, NVB, fat, lateral pedicles, and
lymphatics. These images were found to
independently correlate with the surgeons
impression of the tissue being imaged.
Preliminary comparison with parallel histology
was performed in 4 patients that suggested that
OCT could help to identify the NVB and prostate
capsule during LRP. Conclusions We report our
preliminary experience with the NirisTM OCT
system for imaging of the NVB during LRP. OCT was
able to image the NVB in all patients. This could
potentially enhance surgical precision during
nerve sparing and positively impact potency rates
after radical prostatectomy. Further research
will be needed, including parallel histology and
follow up, to validate the findings of OCT
imaging.
The right and left neurovascular bundles (NVB)
are an arrangement of small blood vessels and
nerves (the cavernous nerves), which run
posterolateral to the prostate in close
apposition to its capsule. It is not possible to
visualize the cavernosal nerves with the naked
eye or under laparoscopic magnification. In
addition the NVBs which contain the majority of
the cavernosal nerve fibers have a variable
location and course. Refinements in technique and
technology are needed to accurately identify and
preserve the NVBs so that patient morbidity could
be reduced. The principle of Optical Coherence
Tomography (OCT) is similar to B-mode ultrasound,
except that it uses near-infrared light instead
of sound waves. It creates a two dimensional map
of the tissue microstructure by illuminating the
tissue with low-power near infrared light,
collecting the back-scattered light, and
analyzing the intensity.
INTRODUCTION
Fig 1 The Niris Imaging System with probe and
foot pedal
2
Preliminary Experience with the NirisTM Optical
Coherence Tomography (OCT) System during
Laparoscopic and Robotic Prostatectomy
VP1-24

• Monish Aron, Jihad H. Kaouk, Nicholas J. Hegarty,
  Jose Roberto Colombo Jr, Georges-Pascal Haber,
  Benjamin I. Chung, Ming Zhou, Inderbir S. Gill
• Section of Laparoscopic and Robotic Surgery,
  Glickman Urological Institute, Cleveland Clinic
  Foundation, Cleveland, Ohio

OCT has potential in the identification of the
NVB during LRP and could improve nerve sparing.
It could be combined with other intra-operative
tools such as TRUS navigation and/or
intraoperative nerve stimulation to maximize
potency outcomes. It can also potentially
distinguish between benign and malignant
glandular tissue and the prostatic capsule. This
optical biopsy could play a potential role in
reducing surgical margins and prognosticating
long-term outcomes. Sometimes younger patients
with excellent pre-operative potency may need
wide excision of the NVB. Such patients may be
candidates for a sural nerve graft or a nerve
conduit. One of the pitfalls of nerve grafting is
the precise identification of the proximal and
distal cut end of suitable nerve fascicles. OCT
technology could potentially aid in identifying
these nerve fascicles. In conclusion, the
potential urological applications of OCT are in
evolution. Further research is needed including
detailed histological comparison and follow-up in
a large cohort of patients, to validate the
findings of OCT imaging.
OCT imaging of the prostate capsule reveals a
dense fibromuscular structure without any
evidence of a layered structure. Sometimes the
OCT images of the capsule may reveal small blood
vessels within its structure. Figure 9 shows the
ex-vivo OCT image of a NVB in a patient who
underwent non nerve-sparing robotic
prostatectomy. The presence of the NVB on the
prostate specimen at the same location was
confirmed on histopathology (Fig 10). The
limitations of this technique include a limited
depth of penetration that prevents deeper tissue
architecture being imaged, and requires very
precise placement of the OCT probe. Imaging
smaller nerves could therefore be quite
challenging. Adipose tissue, lymphatics and small
blood vessels could sometimes mimic nerve tissue.
The technique is highly operator dependant.
CONCLUSIONS
Introduction To evaluate the feasibility of high
resolution optical coherence tomography (OCT) in
the identification of neurovascular bundles (NVB)
during laparoscopic and robotic radical
prostatectomy (LRP). Materials and methods
Between 11/05 and 3/06, 24 patients undergoing
transperitoneal laparoscopic or robotic radical
prostatectomy were enrolled in this study. Once
the bladder was taken down and the prostate
mobilized, the NirisTM imaging system was
deployed. In each patient, in-vivo images were
obtained to determine the image characteristics
of NVB, adipose tissue, prostate capsule, and
endopelvic fascia. The NVB was imaged again
in-vivo, after the prostate was excised. Ex-vivo
images were obtained from the prostate surface to
look for presence or absence of NVB and correlate
with the surgeons assessment of the adequacy of
nerve sparing. Results From 24 patients, we
obtained more than 300 OCT images of tissue
structures including endopelvic fascia, prostate
capsule, NVB, fat, lateral pedicles, and
lymphatics. These images were found to
independently correlate with the surgeons
impression of the tissue being imaged.
Preliminary comparison with parallel histology
was performed in 4 patients that suggested that
OCT could help to identify the NVB and prostate
capsule during LRP. Conclusions We report our
preliminary experience with the NirisTM OCT
system for imaging of the NVB during LRP. OCT was
able to image the NVB in all patients. This could
potentially enhance surgical precision during
nerve sparing and positively impact potency rates
after radical prostatectomy. Further research
will be needed, including parallel histology and
follow up, to validate the findings of OCT
imaging.
Fig 3 OCT imaging of the prostate capsule
reveals a dense fibromuscular structure (arrow)
without any evidence of a layered structure
Fig 4 Sometimes the OCT images of the prostate
capsule may reveal small blood vessels within its
structure
Fig 2 Nerve in tangential section. The
perineurium is identified by arrows. The nerve
fascicle is seen in tangential section with axons
outlined by endoneurium
Fig 6 An OCT image of lymphatics. Note the
variability of shapes and sizes and the absence
of a well-defined wall around the lumens.
The NirisTM system was able to distinguish
between nerve tissue (Fig 2), prostate capsule
(Figs 3-4), fat (Fig 5), lymphatics (Fig 6) and
NVB (Fig 7-8). Nerve tissue reveals axons
outlined by endoneurium and the fascicles are in
turn enveloped by dense perineurium.
Fig 5 An OCT image of a fat globule. Rotating
the OCT probe will show an absence of
longitudinal arrangement in a fat globule. In
addition the dense perineurium will be absent
Fig 7 In vivo OCT image of NVB prior to excision
of the prostate during LRP
RESULTS (continued)
Fig 10 Histopathology confirmed presence of a
large nerve trunk (arrow) in the right NVB at the
marked site corresponding to the OCT image (Fig 9)
Fig 9 Ex-vivo OCT image of right NVB on the
prostate specimen after non nerve sparing robotic
prostatectomy
Fig 8 In-vivo OCT image of residual NVB after
LRP