Microstructured silica fibres for surgical applications: A truly flexible laser scalpel.
Tiina
Delmonte, Jon Shephard
Collaborators
Prof Jonathan Knight
(Centre
for Photonics and Photonic Materials,
Prof Hamish Simpson
(Harrison
Law Chair of Orthopaedic Surgery, Department of Orthopaedic Surgery, University
of
Summary
Optical
fibres and lasers are complementary technologies and in many instances one is
of limited use without the other. The flexibility and guidance properties of
the fibre allow the unique properties of the laser light to be maintained
whilst it is flexibly delivered to wherever required, whether over a few metres
for a laser welding application; a few tens or hundreds of metres for a remote
sensing application or thousands of km for communications.
There
is an urgent technological requirement for optical fibres that can transmit
laser energy in the infrared (IR) wavelength region (above 2 microns) driven by
demands of exciting new applications. One such application is in laser medicine
for the fibre delivery of surgical lasers: a truly flexible laser scalpel.
However, nearly all optical fibres are fabricated from a glass known as silica
and whilst silica is transparent to visible radiation, there are certain types
of radiation that it will not transmit. In particular silica will not transmit
IR wavelengths.
Dramatic advances in silica fibre technology
have been made in the last few years, however, with the invention of a
radically different class of fibre – the photonic crystal fibre (PCF) also
known as the micro-structured or “holey” fibre. One such fibre has a hollow
core (a hollow core microstructured fibre - HCMF) where the majority of power
is guided in air. In these fibres only a small fraction of light overlaps with
the silica glass and hence the strong material absorption of IR energy is
minimised.
Recently,
we (together with collaborators) have demonstrated for the first time in the
world that the practical wavelength range of silica fibres need not be limited
by this intrinsic material absorption. It is now possible to realise a novel
all‑silica HCMF design that can guide into the IR region which finally
paves the way to integrate silica fibre technology with emerging IR
applications.
The aim of this research programme is to
explore the possibilities of fibre delivery for IR lasers using these novel
HCMFs, which will be designed and developed by myself and my collaborators. To
demonstrate the usefulness of these novel fibres I will carry out a feasibility
study applying these fibres to laser surgery:
Laser surgery:
Certain
IR lasers (e.g. Er:YAG) are particularly suitable for laser surgery because the
water contained in human tissue strongly absorbs IR radiation. By precisely
delivering the laser to specific areas damage to surrounding tissue can be
minimised. Hence, lasers are being increasingly used in surgical procedures
with a growing number of medical applications that utilise the Er:YAG laser,
operating at 2.94 microns.
Currently the most common method of delivery
of surgical lasers is achieved using articulated arms. There are a number of
shortfalls with these systems in that there are often misalignment issues, the
arms are unreliable and they are difficult to install which requires a
dedicated, skilled technician. Additionally, the articulated arm, although
useful for delivering laser light to the patient, is perhaps less user friendly
than a surgeon using a blade and there is significant restriction to movement.
Therefore the benefits of using laser light for surgery are offset by the
restriction to the surgeon’s skill that the articulated arms can impose. A
robust fibre delivery system would alleviate these problems and radically
increase the usefulness of surgical lasers.
All-silica
fibres have many advantages over other IR guiding optical fibres currently
being investigated for this purpose in particular they are; non-toxic;
bio-inert; mechanically strong and very flexible. Of course, because
traditional silica fibres do not guide into the IR they have not been
considered previously for this application. However, the radical approach of
using an HCMF to deliver a surgical laser finally paves the way to introduce
silica fibre based technology to the operating table.