Warren Clark explores current and future opportunities for photonics in the medical field
Perhaps the greatest opportunity for the impact that the laser can have on our lives is in medicine. Though photonic technology permeates our lives through consumer products every day, it is the lifesaving potential of laser-based techniques that can make the masses sit up and take note of photonics in a major way.
Matthias Schulze, director of marketing for OEM components and instrumentation at Coherent, says: ‘Medical laser applications are split up in to two major areas – discretionary spending (paid for by the consumer), and procedures covered by insurance. As a supplier to this market, we need to monitor where the money flow is and develop products accordingly. For example, during the recent economic crisis, discretionary spending – on non-essential cosmetic procedures, for example – fell dramatically, and only started to pick up when the macro-economic conditions improved.’
From a technical perspective, the demands on the laser are very different to the more ‘conventional’ industrial uses, where the expectation is that lasers operate 24/7. ‘The challenge within the medical market is the difference in expectations as to how the laser should perform,’ continues Schulze. ‘The utilisation is fundamentally different. A treatment might only take a matter of seconds, but it takes much longer to prepare the next patient.’
Without doubt, the market that has the most potential right now is that of cosmetic skin treatments, such as hair removal and skin resurfacing. ‘Consumer confidence has returned to such a point that we believe a new market will open up – that of home-based skin treatments using laser technology,’ says Schulze. ‘This is not something that is on the horizon; it’s here now, and is expected to grow much further.’
With skin resurfacing, the more common technique involves a scalpel cutting the skin, leading to long healing times. A CO2 laser -based procedure, which has already been around for some years, is much milder by comparison and has less impact on the patient in terms of recovery.
‘In the past decade or so, the fractional laser method has been developed,’ says Schulze. ‘Here, rather than removing skin, the laser drills tiny holes, and the natural healing process will deliver the restored and rejuvenated skin. It also stimulates collagen production, which helps the skin look younger.
‘For hair removal, the technology used is an 808nm infrared diode, but more recently longer wavelengths have been used for darker skin.’
Typically, up to now, these procedures have also been carried out in a clinical environment, largely because there is a risk of accidentally applying the laser to early-stage cancerous cells, which can be very dangerous for the patient. However, the FDA has recently approved a home-based procedure for hair removal.
Laser Components is also involved in supplying its Seminex and Arima diodes for use in this field. Stuart Nunn says: ‘For laser hair removal, we predominantly use our Arima diodes in the 810nm wavelength. This wavelength is most effective for hair removal as it penetrates deeper into the skin, reaching the hair follicle.’
‘Our Seminex laser diodes are used in the field of skin wrinkle reduction, acne treatment and wart removal, predominantly at 1470nm. These skin conditions exist closer to the surface of the skin just below the upper epidermis layer. The melanonin found in the epidermis does not absorb these wavelengths strongly. As it is insensitive to skin type, this means there is no need to adjust output power for every patient. As water is strongly absorbent at this wavelength, the right penetration depth is achieved, and one chooses a laser based on the depth required.
‘Clinical trials have shown that these treatments are very effective, and they are being administered in a live clinical environment.’
‘Aesthetic or cosmetic procedures are set for strong growth over the next couple of years,’ says Schulze, ‘to a point where the sector might overtake ophthalmology in terms of dollar revenue. It is worth noting that the market for cosmetic procedures is booming in Asia. Appearance is culturally important in that part of the world, and as countries become more wealthy, they are spending more on aesthetic procedures.’
The fractional laser method is also applied in a novel method to deliver drugs into the body. Christian Naumer, product manager, mounted bar business at Oclaro, says: ‘We are working with Pantec Biosolutions on a lightweight, tabletop medical device, called Please (Precise Laser Epidermal System) Professional, that incorporates a solid-state, diode-pumped, Erbium YAG laser.
‘It works by creating micropores into the skin to enable a large number of treatments and therapies, including in vitro fertilisation (in fact, a clinical trial earlier this year has resulted in the first pregnancy using this drug delivery method). While the device is designed for use in clinics and medical practices, work is in progress on a smaller, battery-powered hand-held device, which could be used at home.
‘In both cases, the laser light is applied to the skin, creating a precise pattern of micropores into the outermost layers. For drug delivery applications, a drug-containing patch or cream is then applied to the skin, allowing the medication to be absorbed through the micropores in a controlled manner – functioning in a similar way to a nicotine patch. Ultimately, such a hand-held device could be available from a drugstore, allowing the whole process to be carried out at home and at the patient’s convenience. Both devices are laser Class 1 graded, omitting the need for specific laser safety precautions.
‘The higher power Please Professional version has already been introduced by Pantec Biosolutions; the hand-held device is currently under development.’
For the moment, the largest sector in terms of dollars is ophthalmology, which covers two major applications of laser technology. Lasik treatments use excimer lasers to reshape the cornea, while photocoagulation is a technique used to treat age-related macular degeneration (AMD). AMD is the leading cause of blindness and loss of vision in the Western world.
Coherent’s Schulze says: ‘This technique involves using a CW yellow laser to cauterise leaking blood vessels in the retina. The trick here is to hit the wavelength absorption peak of the oxygenated haemoglobin, which is 577nm. Our OPSL technology enables the laser to be tuned to exactly that wavelength. If you hit the absorption at the peak, you need less light, there is less heat generated and the process is much more efficient. There is also a greater degree of patient comfort and faster healing.’
A growing area within biophotonics is photodynamic therapy, whereby a photosensitiser drug is first introduced into the body. Dr Dirk Hüttenberger, director of research and development at Apocare Pharma, continues the explanation: ‘After a period of three to four hours, one has selectively enriched tumour cells. The drug itself is non-toxic and performs no other function, until a laser light is introduced to excite the photosensitiser. Using a blue light, this process generates fluorescence, which enables medical staff to differentiate between healthy and cancerous tissue. Then, using a red laser, which achieves a higher penetration into the tissue, one creates reactive oxygen species, which then destroy the affected cells selectively.
‘At Apocare, we are developing a new photosensitiser, which has a few advantages: it doesn’t stay so long in the patient, and is more rapidly enriched in the tumour cells. We then use spectrometers (from Avantes) to measure the amount of the drug in particular cells. We then use these measurements to calculate the light dosage required for effective destruction of the cells. With the presence of the photosensitiser, we can illuminate the whole tumour area with the laser without damaging healthy tissue.
‘At the moment, this form of therapy is used largely to treat skin cancer, since the affected areas are on or close to the surface. We are also looking at treatments for bladder cancer, for example, since it is relatively easy to bring light into the bladder. Indeed, Avantes has built us a fibre optic device to enable us to take spectrometric measurements in the bladder. The same principle can also be applied for lung cancer, by passing fibre optic cable through an endoscope working channel.
‘Ultimately, we are looking to build a medical device that enables the measurements to be taken and the laser treatment to be administered, without the need for a physicist to be present to do all the calculations. We are looking at clinical trials of this early in 2012.’
Medical device manufacture
Lasers play a huge part in the manufacture of medical devices, where femtosecond lasers allow the size of objects to be reduced and be fabricated at the micro or even nano scale. Lithuanian company Workshop of Photonics is heavily involved in this area. It recognises the importance of these characteristics to medicine, where all measurements are dependent on the size of biological structures, like size of blood vessel or cell.
Zivile Simkute, responsible for R&D sales at Workshop of Photonics, says: ‘For example, there are methods to cut stents from metals, but fabricating a stent from biodegradable or thermo-sensitive materials is still a difficult task. However, using femtosecond laser technology means even tiny stents for capillaries can be fabricated to a high level of precision.
‘Our laser Femtofabrication technology platform allows products for medicine to be made using additive technology. Two-photon polymerisation (2PP) is a technology for building 3D polymeric structures in nanometre precision. The standard direct writing technique is able to produce repeatable structures as small as 100nm, but by employing the controllable self-polymerisation effect, this is reduced to 20nm.
‘For medical applications special polymeric materials are created and tested in vivo and in vitro. Biocompatibility and biodegradability are the main features for fabrication of artificial 3D polymeric scaffolds for stem cell growth. Polymeric 3D scaffolds can replace other artificial scaffolds used in todays’s regenerative medicine. With the help of our femtosecond technology platform, artificial scaffolds can be made that are identical to a natural tissue structure. For example, a stem cell may not appear any different while growing in the artificial polymeric scaffold, because porosity, permeability or elastic features can be easily tuned according to the requirements.’
Other medical markets worthy of mention include lithotripsy, where lasers are used to destroy urinary stones. Laser light is delivered via a fibre, and a plasma shockwave is generated at the tip. This plasma wave shatters the stone.
Dentistry is another area, where lasers can be used to drill holes in the teeth, or remove diseased soft gum tissue.
Coherent’s Schulze concludes: ‘Overall, there is potential in the field of diagnostics (as opposed to treatment), particularly with optical coherence tomography (OCT). This is a tool that allows for deeper analysis of tissue, whether that be the retina, a tooth and so on.’