Tech Briefs Magazine - November 2021 - PIT-14

Illumination Design Considerations for Robotic Surgery Vision Systems
T
C
2D/3D Display
Fluidics
Stereoscopic
Console
Master Software
Light Engine
Camera Control Unit
Camera Cable
High NA fibers integrated
into the shaft
Video Laparoscope
B
NIR
R
G
Fiber taper integrated
into the handle
Low NA
Optical Fiber
he goal of robotics and roboticassisted
surgery is to enable surgeons
to perform complex, previously
not-available procedures with increased
precision that leads to reduced surgery
and recovery times, as well as lowering
risks for patients. Robotic surgery has
made significant impacts in many
applications including prostatectomy,
nephrectomy, and hysterectomy colorectal
surgery. With recent advances
in technology, there are now more
robotics applications in development
than ever before.
To improve surgical workflow, site
access, and recovery times, new innovations
are appearing in all subsystems
across the surgical robotic architecture.
Improving image quality with
accurate and consistent visualization
allows surgeons to make more
informed surgical decisions during a
procedure. Surgical vision systems
match wide field-of-view cameras with
fiber optic or LED illumination components.
Oftentimes in product
development, however, the performance
requirements and design of the illumination
system are given far less time and
resources than the camera.
To have a successful product, one
must consider all the required sub-systems
to deliver high-quality illumination.
A specific example of this situation
is a high-definition, 3D-laparoscope utilizing
a chip on tip camera.
Figure 1. The capital equipment houses various subsystems, typically a 2D or 3D display, camera control unit,
system CPU and software, and the illumination module. This module would house the LED light engine. The
light engine includes LEDs to create the white light (from R, G, B and C) and NIR spectrum and is transmitted,
via a fiber to the laparoscope which houses the fiber taper. The output of the taper will couple to the
high NA fibers routed to the tip of the laparoscope. The captured video is displayed on the capital equipment's
screen and the robotic system's stereoscopic console (console not shown).
The 3D surgical vision system has four
key subsystems:
(1) Illumination system, which brings
light to the surgical target,
(2) The camera (lenses and CMOS sensor)
to capture light from the tissue,
(3) Firmware to control image quality
and latency, and
(4) A display system (a combination of
2D and 3D displays).
Each subsystem has its own key questions
the design team should consider.
Clinical Applications
Prior to designing a robust illumination
system, the design engineer must
have a comprehensive understanding of
the clinical team's goals for a given surgical
procedure. Often, a product manager
acting as the " Voice of the Customer "
14
Cov
ToC
will identify a predicate device and ask
for the " best image quality " . The R&D
team will have to translate this request
into quantitative requirements, identifying
imaging modalities and numerical
limits on FOV, resolution, color accuracy,
and image contrast as examples, eventually
leading to the complete product
requirements. In this article we will consider
a light source for a 3D laparoscope
with a camera field-of-view of 80° and a
working distance of 5 to 100 mm. We will
primarily consider white light applications
but will discuss fluorescence considerations
as well.
To elucidate this, we consider here
the design of a fiber-based illumination
system, with an LED light engine
installed in a confined equipment housing
as part of the " capital equipment, "
i.e. vision tower. The capital equipment
encompasses the cart that typically houses
the vision and additional control systems
of the surgical platform. The
intended architecture of the surgical system
is a rigid stereo-laparoscope for use
in a robotic surgical system. To reduce
risk to schedule, safety, and future user
needs of integrating fluorescence or
other source dependent imaging, we will
consider a fiber-based solution. The
authors appreciate the advances LEDs
continue to make in size and efficiencies
and will address the design space at the
end of the article.
Illumination Considerations for
Robotic Surgery
Figure 1 highlights the major system
architectures of the illumination system
for a robotic surgery platform. To deliver
light to the scope, an illumination
source - in this case, a light engine - is
required. The light engine will couple
light into a fiber taper, if needed, and
then deliver it to the fibers that will
transmit light to the tip.
The light engine is a light source that
is installed in capital equipment. There
are different architectures for these
sources, but they can be distilled down
to two primary types. Some light engines
will use a single, broadband source,
while others will take advantage of mixing
narrow band LED's to create a
broadband source. A single broadband
LED has the risk of needing to correct
for blue light due to the white LED
architecture that uses a blue LED to activate
a phosphor. A high proportion of
Photonics & Imaging Technology, November 2021

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Tech Briefs Magazine - November 2021

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