applications mEdical
➤Class 1 graded, omitting the need for specifi c laser safety precautions. ‘The higher power Please Professional version has already been introduced by Pantec Biosolutions; the hand-held device is currently under development.’
opthalmology
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 effi cient. There is also a greater degree of patient comfort and faster healing.’
photodynamic therapy A growing area within biophotonics is photodynamic therapy, whereby a photosensitiser drug is fi rst 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 fl uorescence, 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 fi bre optic device to enable us to take spectrometric measurements in the bladder. The same principle can also be applied for lung
‘Our laser Femtofabrication technology We can illuminate the whole
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.
tumour area with the laser without damaging healthy tissue
cancer, by passing fi bre 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
coherent’s Excistar Xs is used in ophthalmology for lasik surgery
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 diffi cult task. However, using femtosecond laser technology means even tiny stents for capillaries can be fabricated to a high level of precision.
14 ElEctro optics l october 2011
‘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 artifi cial 3D polymeric scaffolds for stem cell growth. Polymeric 3D scaffolds can replace other artifi cial scaffolds used in todays’s regenerative medicine. With the help of our femtosecond technology platform, artifi cial 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 artifi cial polymeric scaffold, because porosity, permeability or elastic features can be easily tuned according to the requirements.’
other markets
Other medical markets worthy of mention include lithotripsy, where lasers are used to destroy urinary stones. Laser light is delivered via a fi bre, 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 fi eld 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.’
www.electrooptics.com
sEm micrographs of 3d artifi cial scaffolds, fabricated using femtosecond lasers from Workshop of photonics
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