Page 301 - Flexible Robotics in Medicine

Design evolution of a flexible robotic bending end-effector for transluminal explorations 291

and more regular monitoring of the nasopharyngeal cavity at their own comfort of home.
The captured images will be viewed and assessed by the clinician, but this can be done
offline without formal meet-ups with clinicians.

13.2 Prior art and design criteria

Nasopharyngoscopy or nasal endoscopy is the process of evaluating the nasal passages via
optics. The process is usually done by professionals using either a rigid or flexible fiber
optic scope. The scope will be inserted through the nasal passages until the professional is
able to see the nasopharynx. Any abnormalities indicating the presence of NPC can thus be
observed. Imaging devices are usually linked to the proximal end of the scopes allowing a
zoomed and more detailed inspection.
Rigid endoscopes are used in various forms of endoscopies and consist of a long rigid
tube and an optical element at the distal tip. This optical element has a fixed viewing
angle depending on the maker. Most commonly, a fiber optic wire is attached to the
optical element and passed throughout the rigid tube to transmit the image to the
viewer.

Flexible endoscopes, on the other hand, provide more complicated maneuvering for hard to
reach places, such as colonoscopy. The key technology behind flexible endoscopes is their
designs, which include segmented, continuum, and shape memory alloy based.

Most of the segmented designs currently are based on repeated segments where these
segments are linked via coupling means such as hinges and connectors to allow bending of
the endoscope. One example would be US patent 0060239 A1, where different segments
are connected by hinges.

Continuum tubular designs make use of concentric tubes with several precurved tubes with
various levels of flexibility. This will enable the user to maintain a level of rigidity in
fragile operations to not further harm the surrounding tissue yet be able to reach a certain
point within the intended organ. One example of an endoscope with continuum design is
US patent 0023911, which uses two concentric tubes rotatable to one another, allowing
elongation of the shaft.
Shape memory alloy designs are based on metallic materials such as nitinol, where the
endoscope will be able to deform or return to its original shape based on the
thermodynamic environment it is subjected to. US patent 5645520 is one example of an
endoscopic shape memory alloy based design that uses fluids of controllable
temperature to run through channels within the body, allowing the varying of shape.
The above continuum and shape memory alloy based designs have limited flexibility
as both depend on the premanufacturing process to determine the bending angle. The