Brave new world of lasers and robots driving ENT surgery

THE last five decades have witnessed several advances in otolaryngology (ear, nose and throat surgery). The development of a variety of highly specialised technologies, designed by engineers to be used by ENT surgeons to deliver better treatment for their patients, has been the driving force behind minimally invasive surgery for benign and malignant conditions requiring surgery with or without reconstruction of the head and neck.

The impact these engineering feats have had are quite staggering on the reduction of disfigurement to the individual, concomitant collateral injury to structures uninvolved and, most importantly, quality of life. The ENT surgeon has, quite simply put, a rather important role in aiming to preserve bodily functions that are often taken for granted - such as breathing, speaking, swallowing AND the majority of the "special senses" which include hearing, balance, smell and taste.

Surgical odyssey in space age

For the most part of the 20th century, ENT surgery was fairly rudimentary in its application. Access to the ear, nose and throat was hindered by the lack of equipment that could illuminate these small and poorly visualisable orifices with an added feature of secretions such as saliva, mucus and in the surgical context - blood and pus. In addition, there was always the challenge of an altered anatomy from the very pathology that was being treated.

Given the intricacies surrounding the head and neck with its plethora of important nerves, arteries and structures, the need to be able to magnify the operative field and minimise the size of the instruments to fit into the field became the necessity that mothered these inventions.

Lasers

Nobel Laureate Albert Einstein postulated the ability to amplify light by the stimulation of radiation emissions ("laser" is an acronym for "light amplification by the stimulated emission of radiation") almost a century ago. It was not until Theodore Maiman, an American engineer designed the progenitor of the laser - utilising microwaves instead of light (the "maser") and thereafter using a crystal of ruby to create light amplification, that the first solid state laser was invented. Further development of lasers allowed for cheaper materials to be used as the media for light amplification. Indian scientist Dr Kumar Patel's seminal work at Bell Laboratories in the United States resulted in the development of the now ubiquitous carbon dioxide (CO2) laser.

Lasers were a technological breakthrough in medicine for a variety of reasons. The different types of lasers possessed very "feature-specific" properties - the most important being that they existed at a fixed wavelength of light and in so doing would only be absorbed by certain equally specific constituents of the human body.

An example of this would be the potassium-titanyl phosphate laser (KTP), a "green-light laser" that had properties which would be specific to substances that were in the red band of the spectrum of visible light. The commonest example of such a substance would be the molecule called haemoglobin found in blood that gives it its redness. Haemoglobin would better absorb the light energy from the KTP laser compared to plain water which is colourless. Therein lay the potential for selective uses of laser energy in the body - from skin (pigmented moles, scars, loose skin, cancers) to tumours in the mouth, nose and throat and even stones in the salivary ducts (and in the case of urologists - within the kidney, ureters and bladder - the Holmium-YAG laser).

The CO2 laser has come a long way from its first experimental use on dogs in the early 1970s. The seminal work by Drs Jako and Strong at Tufts University in Boston, US, which paved the way for laser surgery of the voice box and throat - cruder then when compared to now - was an engineering marvel providing the precision tool to cut, ablate and penetrate according to the indication it was used for.

It has become a workhorse in the treatment of tumours of the voice box and is used by surgeons to treat snoring and help in the management of sleep apnoea. While originally designed to be applied/fired in a straight line given its long and "unwieldy" wavelength, it is now manipulated by a joy stick akin to a computer game with the added benefit of magnification by an operating microscope. Flexible fibre delivery - designed in the late 20th century - has allowed the surgeon to utilise the CO2 laser with flexible fibre endoscopes in awkward locations like the middle ear, tongue base and nose.

It is now quite common in several centres across the world that patients are awake and locally anaesthetised while the scope and laser fibre are inserted and applied - something that would have been impossible a generation ago. Minimally invasive surgery is progressing at a pace that would have been inconceivable five decades ago, with advances in optics, lasers, diagnostics, robotics and computer-aided therapeutics.

Robots

When Leonardo da Vinci dreamt of his Automa cavaliere (Automaton knight) over five centuries ago, little did he realise that his invention would be remembered as the Robot di Leonardo and inspire the creation of similar automatons that would help humans perform tasks in a pre-programmable fashion across diverse settings such as the motorcar manufacturing industry to medicine.

The term robot, however, was coined by the brother of Czech playwright Karel Capek who used it in his play Rossum's Universal Robots. The meaning of robot was essentially "servitude" and had its origins from the Germanic for "work" - arbeit.

Modern medical robotics took off in the early 21st century. The essential difference in the application of medical robots compared to industrial ones was one of complete independence from human interference/control to one where the robot "operator" remained in control of all functions regarding the surgical procedure. The debate that surrounds this term "robot" in the surgical context is thus one where the current robots used in otolaryngology are really manipulators and not independent machines with algorithmic programming to substitute the surgeon's decision-making and skill.

Current robotic technology in ENT is mainly limited to two platforms - the da Vinci Surgical System (Intuitive Surgical Inc, Sunnyvale, California, US) and the Medrobotics Flex system (Medrobotics Raynham, Massachusetts, US). Both systems provide the surgeon with access to the upper aerodigestive tract through the mouth.

The da Vinci system is a rigid, line-of-sight system incorporating a camera arm with high definition visualisation and illumination while two other instrument arms are inserted into the mouth to manoeuvre, dissect, cut and coagulate tissue.

The system has allowed head and neck surgeons to access the back of the mouth and tongue - areas generally difficult to operate, given the contours of the mouth, throat and back of the voice box (larynx). As a result, patients undergoing radical and often mutilating procedures requiring splitting of their jaw to remove cancers from their tonsils, palate and tongue base with further plastic surgical reconstruction can now be successfully treated without the need to perform such extensive surgery.

The results of these operations are equally good compared to the more radical open operation but the quality of life after the operation is better with shorter lengths of stay in hospital. The Flex system is effectively a hybrid of a flexible endoscopic platform which is controlled using a manipulator and a rigid camera with side-arms allowing for grasping, cutting, laser transmission and dissection and resembles a multi-linked "snake". The major differences between the two systems reside in the fact that the "Flex" was designed specifically for the needs of head and neck surgery (initially) while the da Vinci system has a wider field of application. It is particularly useful given its flexibility to negotiate the areas behind the tongue and can enter the voice box and upper oesophagus.

Lasers and robots are alternatives to providing precision and access to the complex and challenging anatomy of the upper aerodigestive tract. With more features such as high-definition video, illumination, image guidance and anti-tremor filtering, the march of technology continues unabated.

This series is produced in collaboration with Singapore Medical Specialists Centre.