FEATURE
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Healing light

Diode lasers are well-suited to a diverse array of medical applications ranging from cosmetic to surgical, as Jessica Rowbury finds out

According to a report released in October by Transparency Market Research, the global medical laser systems market will be worth $2 billion by 2018 at a 12.5 per cent compound annual growth rate.

Among the several product types listed in the study, the diode laser segment held the largest market share in 2011 and is anticipated to maintain its leading position during the forecast horizon. This can be attributed to the fact that diodes are used for a wide range of medical applications, such as photodynamic therapy and aesthetic treatments, according to the report.

As well as looking at complete systems, a healthy grow rate is also expected for medical diode components, explained Jörg Neukum, director of sales and marketing at Dilas: ‘We expect it to increase by about 10 per cent gross year on year.’

Low-cost, efficiency, and ease of use make laser diodes well-suited to use in various medical applications, which include cosmetic, diagnostic, surgical, and therapeutic.

However, it’s the flexibility of diodes that makes them suitable for such a wide range of medical uses, whether it’s to treat a rash on the surface of the skin or to cauterise tissue during surgery. ‘You can tailor the wavelength to the specific needs of the treatment, and you can adjust the power by adding more laser diodes and get the light out of the same fibre,’ said Neukum.

‘For example, for dermatology treatments, you’d want to have high water absorption so there is no penetration into the tissue; you would therefore go with the wavelength that has this high absorption [800-900nm]. But, if you want to do something which goes deeper into the tissue you use a different wavelength [around 1,900nm],’ he said, adding that changing the wavelengths and powers of other laser types becomes much more difficult.

In addition, diode lasers can be fibre coupled, which is particularly beneficial for medical applications, as with most procedures the laser is usually attached to a rod or a wand that is either handheld or attached to a robotic arm. This allows the laser to move in various directions and ensures a precise and targeted treatment. ‘The fact that many wavelengths available nowadays are fibre coupled sources makes it easier for use by doctors, and easier to do maintenance on the system – so it’s a much more user-friendly system with fibre coupling,’ Neukum added.

Light therapy

Diode lasers are a popular choice of light source for use in both photodynamic and low level laser therapies. Photodynamic therapy involves the use of a laser to affect a photo-sensitive drug injected into the body, creating a reaction to help in the patient’s treatment. Low level laser therapy is a similar type of treatment, except it is used to inhibit or stimulate cells directly, with no photo-sensitive medication required.

These methods are being researched to develop new treatments for a wider variety of conditions – already, diseases ranging from mild skin conditions such as dermatitis or acne, to complex diseases such cancer, can be treated using such therapies. ‘There is a lot of research going into which wavelengths are good for which treatment for different conditions,’ noted Dr Jeremy Lane, MD for laser operations at ProPhotonix.

In some cases, wavelengths can be combined to treat a condition more effectively. For example, visible red lasers can be used to encourage the skin to heal faster after mild burns or rashes, but can be combined with UV light to provide an additional anti-bacterial affect.

‘UV lasers and red lasers can be used together for applications such as treating acne,’ Lane pointed out. ‘A blue violet laser can help to kill the bacteria that caused the acne, and a red laser can be used to speed up the healing of the skin. Salons would use this treatment, but hospitals are using the treatment as well.’

Although these types of therapies have been used to treat conditions such a cancer, currently the majority of the commercial systems reside in salons for cosmetic procedures. As the research continues, however, it is expected that these types of therapies will be seen more in hospitals for use in a wider range of medical applications. Lane said: ‘At the moment, not a lot of this is hospital-based, but a lot of the clinicians are involved in the research. I think the low level laser therapy type applications will become more mainstream and we will be seeing a lot more of this in clinics and hospitals, rather than salons, in the future.’

Higher powers, multi-functional, user-friendly

Although laser diode technology is well-established, the way in which medical diode systems are being configured is changing. The demand for medical instruments that have higher powers, are user-friendly and can be used for more than one function, has increased.

According to Dilas’ Neukum, medical system manufacturers are requiring higher powers because it allows for faster treatments. ‘If you take a hair removal laser diode… it’s no longer single hairs that are treated, but the whole of someone’s back, for instance, and you can treat this using a really high power non-fibre coupled diode laser.’

Higher laser powers can also allow for reduced surgery times, so that patients require less anaesthesia and, in turn, need shorter recovery times. ‘When you have some treatments where people have to have anaesthesia… with more power you could do faster treatments,’ Neukum explained. ‘For example, there are some procedures that are 90 minutes, and this could be reduced to 60 or 45 minutes using higher powers.’

Apart from speedier treatments, multi-wavelength systems – where users can simply press a button for a completely different wavelength – are also increasing in demand. Again, this is beneficial for both cosmetic procedures, as salons can provide two treatments simultaneously and therefore increase profit, but also for surgical applications: ‘Sometimes [doctors] want to switch the wavelength during the treatment. So, they will start for example with 980nm, then towards the end of the treatment they may want to have a much higher absorption in the upper layers of the skin – so the removal rate of the tissue is slower – and then they switch to a longer wavelength,’ explained Neukum.

Another trend, which is particularly apparent for aesthetic-based applications, is the movement of treatments from hospitals and dedicated laser clinics into less conventional settings such as hair or nail salons. This transition was led primarily by laser hair removal applications, but now a variety of treatments, including skin resurfacing, wrinkle removal and tooth whitening among others, can be delivered by trained professionals outside of hospitals.

This trend has driven a demand for devices that are not only smaller, handheld, or even portable, but for ease-of-use, as more users with non-medical backgrounds are adopting the technology. ‘I do see that as the devices become smaller and easier to use, some treatments might be done simply at home and no longer in a doctor’s practice. Or, they might be done in a salon,’ Neukum noted, adding that in the future hair removal systems could be sold in supermarkets for home use.

ProPhotonix’s Lane added: ‘Semiconductor laser diodes are relatively low cost, and they can be integrated into quite portable and handheld-type devices. I’m certainly seeing a lot more of these [smaller, portable] devices being put into production.’

The future for medical diodes

According to the Transparency Market Research report, diode lasers hold the largest share of the global medical laser systems market and further growth is expected. As laser treatments for cosmetic purposes continue to move out of the clinic and into salons, beauty parlours, and possibly one day even the home, they will become available to a much wider audience.

And, with further research into how varying wavelengths and powers can be used to treat different diseases, the number of surgical applications will increase. Diode laser offer a bloodless operating field, minimal swelling and scarring, and decreased post-surgical pain.

‘There are two effects – replacing traditional existing technologies and new treatments with laser-based devices,’ commented Neukum.  ‘And, more people will have access to laser technology for medical applications.’

Positioning the patient

Patient-positioning is an important consideration when using medical and dental instruments, particularly for imaging and radiotherapy. Ensuring that instruments are well aligned with the patient helps ensure high quality imaging, giving clearer information and ultimately helping to achieve swift and accurate diagnoses.

These systems typically use a low power laser mounted alongside the imaging equipment, to show where images will be taken and therefore allow the instruments and patient to align correctly and obtain the best image. Usually a red (635nm) laser line or cross is used, to give a high level of visibility.

A similar, perhaps more crucial, visual alignment application is ensuring surgeons aim high-power lasers precisely when cutting or cauterising tissue. ‘Those high-power lasers need pilot lasers so that the surgeon can see where that cutting laser is going to strike when they hit the ‘on’ button,’ explained Dr Jeremy Lane, managing director for laser operations at ProPhotonix. ‘It is important because obviously if a high power cutting laser is not cutting the patient exactly where the surgeon wants to strike, then there is a serious problem.’

Traditionally, visible red light has always been used for these applications for cost reasons. ‘Surprisingly, considering [the alignment laser] is being used with medical equipment that costs hundreds of thousands of pounds or dollars, patient alignment is a fairly cost-sensitive application,’ Lane pointed out.

According to Lane, green light is actually more favourable for these applications because the wavelength is more visible to the human eye. However, the high cost of green semiconductor direct laser diodes had, up until recently, always limited the use of green lasers.

But as the cost of green lasers is decreasing, medical equipment manufacturers are now moving towards the green wavelength for these systems. ‘As the cost of green laser diodes is coming down, they are taking a bigger share of the market,’ commented Lane. ‘Osram has launched some quite reasonably priced green laser diodes – they are still more expensive than red, but only by a factor of two or three and not by a factor of 50 or 100.

‘So, green is becoming more economical and it is preferred for two reasons – for equipment alignment applications, green is more visible on darker skin tones,’ Lane continued. ‘The other is, for surgical applications, green light is more visible when there is a lot of blood around – if you’re directing a red laser into the human body, then you obviously will not see very well. But if you were to shine a green laser on the same area then you will see it much more clearly.’