New optical technique that 'can see under skin'
A new technique for diagnosing skin cancer, and other skin conditions, may be in the pipeline, the Daily Mail reported today. It said that doctors could be able to “see” under the skin without using invasive techniques, such as biopsies, which can be both unpleasant for the patient and time-consuming for clinicians.
The story comes from a small study which looked at a high resolution imaging technique, known as optical coherence tomography (OCT), that has been described as ‘ultrasound with light’.
Ultrasound scanners work by emitting high-frequency sound waves through human tissue. The way the waves are then scattered as they pass through different types of tissue is converted into a real-time image.
OCT works in the same way, but instead of using sound waves, it uses light. While the light can only penetrate a small layer of skin (around 1-2mm), it can provide detailed images of underlying blood vessels, which existing techniques are unable to do.
This is potentially very useful as certain skin conditions are known to cause changes to the patterns of blood vessels supplying blood to the skin.
Learning more about these blood vessels could aid diagnosis and provide a useful way of seeing how well (or not) a person is responding to treatment.
In the study, researchers used the technique on five patients – one with healthy skin, two with inflammatory skin conditions and two with basal cell carcinoma, the most common form of skin cancer.
They found that in the patients with skin disorders they were able to detect changes to the patterns of blood vessels compared to the person with healthy skin.
A great deal more research into the safety and effectiveness of OCT is required, but the results of this study are certainly promising.
Where did the story come from?
The study was carried out by researchers from Medical University Vienna and Ludwig Maximilian University of Munich and was funded by the European Commission.
The study was published in the peer-reviewed medical journal: Biomedical Optics Express.
The Mail’s story, claiming that doctors could be able to diagnose cancer without using invasive techniques, overstated the results of this research. While the technique has the potential to be able to detect certain skin conditions early, there is no evidence, yet, that it could replace standard methods of diagnosis, such as biopsies.
Many initially promising techniques fail to live up to their potential when they are tested on larger groups of people.
What kind of research was this?
In this study, researchers tested an imaging technique called Optical Coherence Tomography (OCT) to study the fine blood vessels beneath the surface of the skin in five different patients, four of whom had skin conditions including basal cell carcinoma. They were able to view the pattern of blood vessels in these patients without removing them for study in the laboratory. This type of study, called in situ (where the study is carried out in a ‘real-world’ setting, which in this case was a specialist dermatology clinic), is regarded as superior to an in vitro study (which takes place in a laboratory).
In this case, it meant researchers could examine the blood vessels as they delivered blood to skin tissue, in ‘real-time’.
OCT is a technology that produces high-resolution, cross-sectional images at high speed, using light waves. The various ways that light waves are scattered by different types of tissue allows the OCT scanner to ‘build-up’ an image in much the same way as an ultrasound scanner using sound waves.
The advantage is that it can provide images of soft tissue in situ and in real time. OCT has been used to image different parts of the eye since the 1990s and has recently attracted interest from skin specialists. It is typically used to show tissue structure, but can also be used to reveal the pattern of blood vessels.
The researchers say that OCT has the potential to play an important role in cancer diagnosis as well as the development and monitoring of cancer treatments. They say that various disorders are known to affect the vascular network, some at an early stage. They believe that this type of analysis of blood vessels might provide valuable diagnostic information about skin lesions.
The researchers believe they are the first to use OCT to produce images of the network of blood vessels in human skin that feed cancerous skin lesions. They also used a specialist type of laser, called a Bessel beam, to enhance the images produced by OCT.
What did the research involve?
The researchers recruited four patients with skin diseases and one with healthy skin.
- one had allergy-induced eczema (often known as atopic eczema) on the forearm
- one had dermatitis, a common skin disorder, on the forehead
- the third had basal cell carcinoma on the forehead
- the fourth had a basal cell carcinoma on the cheek
The final person, with healthy skin, was used as a ‘mini-control group’ so that the results provided by OCT when looking at their healthy skin could be compared with those from people known to have a skin condition.
Using high-speed OCT and laser, they produced images of the skin lesions and the blood vessels feeding them, from all four patients, in situ and in real time. They compared the pattern of blood vessels found in the four cases with images of healthy tissue in the palm of the hand, in the fifth patient.
What were the basic results?
The results show that the vascular patterns found in all four lesions were significantly different to those found in the healthy skin.
- In the healthy skin, the images showed smaller capillary vessels in the upper layers, and increased vessel size in deeper skin tissue (capillaries are the smallest blood vessels in the body).
- In the cases of eczema and dermatitis (both inflammatory conditions), blood vessels were dilated and blood flow increased.
- In the cases of basal cell carcinoma, the image showed “a denser network of unorganised vessels with chaotic branching; larger vessels even closer to the skin surface; capillary structure less pronounced and visible.”
How did the researchers interpret the results?
The researchers say the results indicate that skin disease is accompanied by abnormal changes in blood vessel patterns. OCT can assess these vascular changes and could be used, they believe, to provide additional information about skin diseases. They say that the study is a step towards non-invasive on-site diagnosis, and could eventually reduce the number of biopsies needed to assess suspected cases of skin cancer and other skin conditions. It could also be used to monitor treatment effectiveness and to assess the stage of disease.
Conclusion
It’s important to point out that this study, while of interest, does not mean that patients with suspected skin cancer can currently be diagnosed by using non invasive imaging, as the Mail implies. The study did not test the effectiveness of this technique, or compare it with standard diagnostic methods such as biopsy. Only two of four patients had a diagnosis of skin cancer. That said, the study is of interest and, as the researchers point out, it is possible that there may be a place for this type of imaging in the early detection of skin cancers, or for guiding biopsies, or staging cancers which have already been diagnosed.
The study was performed in only four patients. A far larger study would be required to confirm whether the differences found in blood vessel patterns in those with basal cell carcinoma were useful for the diagnosis or management of this type of skin cancer.
Also, the cost of the imaging is not described, which makes it difficult to assess whether it would be widely adopted by the NHS if it was found to be effective and safe.
