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A healing light: how lasers can diagnose and treat disease

Also known as biophotonics, biomedical optics encompasses technologies from advanced imaging to light-activated drugs. Clinicians already use it widely – laser eye surgery is a visible example – but researchers believe that optics can help solve many more medical problems.

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William Whelan has seen the light, and it has healing powers. The University of Prince Edward Island physics professor specializes in biomedical optics, a growing field that uses lasers and light to detect, diagnose and treat disease.

Dr. Whelan moved to UPEI from the University of Toronto in 2008 as a Canada Research Chair in Biomedical Optics. His main research interest is new diagnostic and therapeutic technologies deploying sound as well as light.

For several years, Dr. Whelan and his laboratory have been working on laser therapies for cancer. Their target is prostate cancer, which one out of every seven men will develop, according to the Canadian Cancer Society.

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Today, the standard treatment for this disease is surgical resection of the prostate, a highly invasive procedure. By contrast, Dr. Whelan's laser therapy involves implanting optical fibres in the centre of the prostate tumour and heating it to about 55 degrees Celsius for several minutes.

"If you can do that, the tumour cells die very rapidly," says Dr. Whelan, who notes that several other groups in Canada and abroad are developing similar therapies for other solid tumours. "You want to be able to deliver enough laser energy to the tumour, but spare all those critical structures surrounding the tumour."

Also known as biophotonics, biomedical optics encompasses technologies from advanced imaging to light-activated drugs. Clinicians already use it widely – laser eye surgery is a visible example – but researchers believe that optics can help solve many more medical problems.

"It's one of the faster-growing areas of biomedical engineering," says biomedical, electrical and computer engineering professor Irving Bigio, founder of the Biomedical Optics Lab at Boston University. "We're all anxious to see some of it actually make it commercially and get into clinical practice."

To control, monitor and assess its interstitial laser therapy, Dr. Whelan's lab is developing other technologies. One of them is photo-acoustic imaging. Unlike conventional ultrasound, Dr. Whelan explains, this imaging method sends a pulsed laser light into the tumour and its surrounding tissues.

In response, a prostate tumour generates a more intense sound signature than normal tissue. But in a recent study, Dr. Whelan and his colleagues found that prostate cancer cells also give off different sound frequencies than their healthy counterparts. This discovery could help in early cancer detection.

Dr. Whelan says he's most interested in using photo-acoustics to determine how a tumour responds to treatment, as part of what he describes as an all-optical solution to cancer management. With Sano Medical Instruments Inc., based in San Antonio, Texas, his lab has built a prototype photo-acoustic system.

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"We're using laser thermal therapy to treat tissues and then photo-acoustic imaging to monitor how that treatment is going, and also to assess, maybe after a couple of days, what is the overall result of that treatment," Dr. Whelan says.

In the Department of Medical Biophysics at U of T's Faculty of Medicine, Alex Vitkin uses light to assess tissue. One of Dr. Vitkin's research areas is optical coherence tomography (OCT), a biomedical imaging technique that generates high-resolution 3D images of intact tissues.

Convinced that biophotonics will play a major role in personalized medicine, Dr. Vitkin says OCT is important in ophthalmology, oncology and other medical fields. Besides providing fine imaging of microstructure, OCT can detect micro-vascular patterns below the surface of living tissue, down to the capillary level.

"Cancer specialists are starting to realize that the tumour blood supply is as important as the actual tumour cells in terms of what happens, how aggressive the tumour is and how it responds to therapy," Dr. Vitkin says.

Monitoring changes in tumour blood supply during radiation therapy or chemotherapy can help clinicians understand, personalize and ultimately improve these cancer treatments, he explains. "Once we get clever enough, can we adjust the therapy accordingly, thus offering personalized 'midflight correction' for each patient's treatment regimen?"

Dr. Vitkin's lab has also spent a decade working in tissue polarimetry, which he calls a somewhat unexplored but potentially promising branch of biophotonics. Like many other research and industrial groups worldwide, he and his colleagues are trying to use polarized light to non-invasively detect glucose in diabetic patients – so diabetics don't have to draw blood by pricking their fingers.

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"There are many challenges in trying to measure polarization properties of the light after it interacts with tissue," Dr. Vitkin says, "and then in relating these results to important tissue properties such as blood glucose content."

Among its biomedical optics projects at Boston University, Dr. Bigio's lab has built a cancer-detecting fibre optic probe – and used it to screen hundreds of patients for potential colon cancer. The probe, which clinicians can thread into an endoscope, evaluates tissue through a form of optical spectroscopy that measures how light scatters from cells. "The optical measurement is basically instantaneous," Dr. Bigio says. "So you can examine lots of tissues and come up with an assessment of which ones are higher risk."

Dr. Bigio, who is seeking investors to commercialize the device, says it has many potential applications. "The initial one we're going after is a guidance tool for during colonoscopy, to help the doctor be more efficient in finding high-risk tissue and not waste time on tissues that are benign."

For UPEI's Dr. Whelan, one of the most appealing features of optical medical technology is that it doesn't expose patients to ionizing radiation, the way X-rays and CT scans do. Because optical diagnosis and treatment don't require lead-lined rooms, they could also save the health-care system money by reducing infrastructure costs, he says. "As long as we're wearing our laser-protective goggles, we could do this in any room in the hospital."

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